Lecture 3 soil water characteristic curve

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饱和_非饱和有机质粉土抗剪强度的对比

图 2 饱和土抗剪强度τsat 与净正应力σˊ试验曲线 Fig. 2 Variation of shear strength τsat with net normal stress σˊ under same matric suctions ψ for saturated soil 图 3 非饱和土抗剪强度τf 与净正应力σˊ试验曲线 Fig. 3 Variation of shear strength τf with net normal stress σˊ under different matric suctions ψ for unsaturated soil
Abstract: Comparisons of shear strength between the saturated and unsaturated sandy silt were shown based on the measured shear strength using a modified direct shear device, and shear strength was predicted using the saturated soil properties and soil-water characteristic curve (SWCC) for the sandy silt. It was illustrated that the saturated shear strength was less than the unsaturated shear strength, and the unsaturated shear strength increased with increasing matric suction. It was shown by this study that properties of the saturated-unsaturated fine-grained soils were affected by physical conditions and the stress condition in the field. Key words: unsaturated sandy silt; shear strength; matric suction; SWCC

5.土壤水E

Capillary hanging water sketch map
Soil particle
Field capacity：
Field capacity-The amount of water remaining in a soil after the free water has been allowed to drain away (a day or two) after the root zone had been previously saturated; expressed as a percentage.
membranous water
Schematic diagram of membranous water
（3） Soil capillary water ：
Capillary water-The water held in the “capillary” or small pores of a soil, usually with a tension >60 cm of water. Capillary water includes capillary hanging water and capillary rise water.
Percentage water = {[(wet soil weight)-(oven dry soil weight)]/ (oven dry soil weight)} ×100
（二） The volume water content （ θv）
Volume water content = volume of water/bulk volume of soil=(weight of water/ρW)/(weight of dry soil/ ρb)

不同干密度下非饱和土土-水特征曲线

不同干密度下非饱和土土-水特征曲线陈宇龙;内村太郎【摘要】对吸湿与脱湿过程中引起非饱和土土-水特征曲线进行分析,观察不同密度土样的土-水特征曲线与滞后现象.利用Fredlund and Xing的土-水特征曲线模型对试验数据进行拟合,得到模型拟合参数与土-水特征曲线参数的定量关系.研究结果表明:进气值随着参数a的增大而线性增大,残余基质吸力随着参数m的增大而呈幂函数减小,减湿率随着参数n的增大而呈指数减小.干密度对土-水特征曲线有显著影响.随着干密度增大,残余基质吸力与进气值及进水值增大,减湿率减小,滞后现象的显著程度降低.瓶颈效应、不同的接触角和空气体积是造成滞后效应的主要因素.%Drying and wetting soil-water characteristic curves (SWCCs) for two sandy soils were investigated to research the effects of dry density on the SWCCs and hysteretic behaviors. Drying and wetting SWCCs were obtained for two sandy soils with different dry densities. The test data were best-fitted using the Fredlund and Xing equation. The results show that the fitting parametera increases linearly with the increase of the air-entry value of the SWCC, the fitting parameterm decreases with the increase of the residual suction of the SWCC and the fitting parametern also decreases with the increase of the slope of the SWCC. With the increase of parametera, the air-entry value increases linearly; with the increase of parameterm, the residual suction decreases in power function, and with the increase of parameter n, the slope of drying SWCC decreases in exponential function. The dry density has significant effects on the soil-water characteristic curve. With the increase of dry density, the residualsuction, air-entry value and water-entry value increase, and both the slope of drying SWCC and the hysteresis decrease. The hysteresis is mainly attributed to the ink-bottle effect, the contact angle effect and entrapped air.【期刊名称】《中南大学学报（自然科学版）》【年(卷),期】2017(048)003【总页数】7页(P813-819)【关键词】非饱和土;土-水特征曲线;干密度;滞后现象【作者】陈宇龙;内村太郎【作者单位】东京大学土木工程系,日本东京,113-8656;东京大学土木工程系,日本东京,113-8656【正文语种】中文【中图分类】TU441土−水特征曲线(soil-water characteristic curve，SWCC)是描述非饱和土中吸力与饱和度或体积含水率之间关系的曲线[1−2]，它能够反映非饱和土的众多性质如渗透性、强度、应变、应力状态等[3−6]。

A study of hysteresis models for soil-water characteristic curves

Mots clés : courbe caractéristique sol-eau, modèle d’hystérèse, comparaison, courbe à la frontière, courbe de balayage, sols non saturés.
[Traduit par la Rédaction] Pham et al. 1568
Key words: soil-water characteristic curve, hysteresis model, comparison, boundary curve,oils.
Résumé : On présente une revue de modèles d’hystérèse pour les courbes caractéristiques sol-eau. Les modèles peuvent être catégorisés en deux groupes : (i) modèles de domaines (ou modèles basés sur la physique) et (ii) modèles empiriques. Certains modèles sont capables de prédire des courbes de balayage alors que d’autres sont capables de prédire les courbes d’humidification et de séchage à la frontière. Une comparaison de la capacité de cinq modèles sélectionnés pour prédire la courbe d’humidification à la frontière montre que le modèle de Feng et Fredlund bonifié par Pham, Fredlund et Barbour semble être le modèle le plus approprié pour la pratique de l’ingénieur. Une autre comparaison entre cinq modèles basés sur la physique pour prédire les courbes de balayage ont démontré que le modèle de Mualem donne globalement la meilleure prédiction des courbes de balayage. L’étude a montré que prenant en compte l’effet du blocage des pores ne donne pas toujours une meilleure prédiction des courbes caractéristiques d’hystérèse sol-eau. On présente aussi dans cet article une méthode d’échelle pour estimer la courbe initiale de séchage, la courbe de mouillage à la frontière et la courbe de séchage à la frontière.

Nature of Soil–Water Characteristic Curve for Plastic Soils

Nature of Soil–Water Characteristic Curve for Plastic SoilsFernando A.M.Marinho 1Abstract:Determinations of unsaturated soil parameters using experimental procedures are time consuming and difﬁcult.In recent years,the soil–water characteristic curve ͑SWCC ͒has become an important tool in the interpretation of the engineering behavior of unsaturated soils.Difﬁculties associated with determining such parameters have justiﬁed the use of indirect determination.This paper presents the general behavior of the SWCC for plastic soils,in terms of gravimetric water content versus soil suction,according to the soil type,and also the stress history of the soil.In order to investigate possible relationships between the liquid limit ͑w 1͒,suction capacity and SWCC,data from the literature were collected and analyzed.The present study examined 49SWCCs from 18soils.The objectives of the paper were twofold:to contribute to the interpretation and use of the SWCC and to present a simple method for inferring the SWCC for plastic soils,taking into account the stress history of the soil.DOI:10.1061/͑ASCE ͒1090-0241͑2005͒131:5͑654͒CE Database subject headings:Unsaturated soils;Soil water storage;Soil suction;Liquid limit;Stress history .IntroductionThe soil-water characteristic curve ͑SWCC ͒has been used as a tool for predicting the mechanical and hydraulic properties of unsaturated soils.The indirect determination of these parameters may be justiﬁed not only by the difﬁculties involved in such tests but also by the costs associated with determinations of these pa-rameters ͑e.g.,Fredlund 1998͒.The proliferation of SWCC use for indirect determination of unsaturated soil properties is un-avoidable and in some cases desirable.The volume change with increased suction will depend on the initial void ratio and/or the stress history.The shape of the SWCC reﬂects the inﬂuence of stress history on the soil.For this reason,models used for pre-dicting unsaturated soil parameters should consider the inﬂuence of the stress history of the soil via the SWCC.An understanding of the phenomena involved in the relationship between water con-tent and suction is paramount for adequate interpretation of the SWCC.One of the objectives of this paper was to contribute to the interpretation and use of the SWCC,which in turn would help in understanding the engineering behavior of unsaturated soils.The SWCC was analyzed in terms of gravimetric water content versus soil suction,according to the soil type and taking into account the stress history of the soil.A further objective was to present a simple method for deducing the SWCC for plastic soils using one water content/suction determination and the liquid limit of the soil.Background to Soil–Water Characteristic Curve The shape of the SWCC depends on the pore size distribution and compressibility of the soil in relation to suction.These two char-acteristics of porous materials are affected by the initial water content,soil structure,mineralogy,and the stress history ͑e.g.,Lapierre et al.1990;Vanapalli et al.1999;Simms and Yanful 2000͒.Most SWCCs are S shaped and the curve shapes are a response to the pore size distribution of the material.For a rigid porous material of single pore size ͑i.e.,uniform pore size distri-bution ͒,whether it is a soil or not,the SWCC should be similar to curve ͑a ͒shown in Fig.1.However,complete water loss with suction increasing beyond the air entry value is not usual.In other words,it is difﬁcult to remove all the water from a porous mate-rial by means of a small increase in suction.Even in a porous material with uniform pore size distribution,some water would still be present in the material due to surface phenomena.The SWCC shape for a material of single pore size could be more appropriately represented by curve ͑b ͒in Fig.1.Nevertheless,for this material even after air entry suction,some water still remains in the soil and for the removal of the residual water higher energy are required.Curve ͑c ͒in Fig.1represents an example of material with two pore sizes.Each of the sizes is associated with one suction value via the capillary phenomenon ͑e.g.,Fredlund and Rahardjo 1993͒.Material with great numbers of pore sizes should present a more gradual reduction in water content with an in-crease in suction,as shown in curve ͑d ͒in Fig.1.By applying the capillary model,the equivalent pore size for the material can be deduced ͑i.e.,from 0.0146to 0.0000146mm ͒.Clay soils typically have nonuniform grain size and pore size distributions ͑e.g.,Delage and Lefebvre 1983͒.As a consequence,linear and less steeply sloping SWCCs ͑using a semilog plot ͒are normally obtained for clays.Clays may experience shrinkage that reduces pore size.Fine-grained soils with a liquid limit greater than 25%typically exhibit signiﬁcant shrinkage characteristics when dried.This can be observed in Fig.2,in which the liquid limit and shrinkage limit for some soils are presented.This ﬁgure also illustrates that the shrinkage limit by itself is not a sufﬁcient parameter for identifying soil behavior.Shrinkage phenomena in1Associate Professor,Dept.of Foundation and Engineering.,Univ.of São Paulo,CED 04318-002Sao Paulo,Brazil.E-mail:fmarinho@usp.br Note.Discussion open until October 1,2005.Separate discussions must be submitted for individual papers.To extend the closing date by one month,a written request must be ﬁled with the ASCE Managing Editor.The manuscript for this paper was submitted for review and pos-sible publication on May 31,2000;approved on September 23,2004.This paper is part of the Journal of Geotechnical and Geoenvironmental Engineering ,V ol.131,No.5,May 1,2005.©ASCE,ISSN 1090-0241/2005/5-654–661/$25.00.654/JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING ©ASCE /MAY 2005D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .clays due to increased suction can play an important role in shap-ing the SWCC.During shrinkage the emptying of pores is accom-panied by reduction in pore size,which keeps the spaces ﬁlled with water and increases the air entry value.A reduction in pore size in clays may also occur due to me-chanical overconsolidation.In this case,the air entry value is higher than for the normally consolidated soil,and the SWCC shape for this type of material is relatively ﬂat.Various methods are commonly used when deﬁning the SWCC for a soil from lower to higher suction levels ͑e.g.,McQueen and Miller 1974;Blight and Roussev 1995;Barbour 1998͒.The reason for this is that not all methods used to measure suction can cover all suction ranges.Depending on the method used,total or matric suction is obtained.When a combination of methods is used without paying attention to the type of suction that is being measured,the SWCC shape may be affected if the value of osmotic suction is signiﬁcant.For suctions up to 30kPa,the pressure plate method with the hanging column is usually convenient.For suctions between 30and 1,500kPa,the pressure plate ͑i.e.,axis-translation technique ͒or ﬁlter paper methods can be used.In most high suction range ͑i.e.,greater than 1,500kPa ͒the suction measured is the total suction,regardless of the method used for measurement.Marinho and Chandler ͑1993͒drew attention to the fact that the ﬁlter paper,even when in con-tact with the soil,may not have adequate contact with the soil–water and hence this method may measure a combination of total and matric suction.Effect of Soil Plasticity on Soil–Water Characteristic CurveThe inﬂuence of soil plasticity on the SWCC has been demon-strated in the literature ͑e.g.,Black 1962;Mitchell and Avalle 1984;Fleureau et al.1990,among others ͒.Results obtained by Marinho and Chandler ͑1993͒showed a relationship between liq-uid limit and suction capacity ͑C ͒for compacted soils.Suction capacity is deﬁned as the reduction in water content ͑expressed in percent ͒over one logarithmic cycle.It has also been suggested that soils prepared from slurries should represent the upper limit of suction capacity for a given soil.There is a unique relationship between soil suction and water content normalized by the suction capacity C ͑i.e.w /C ͒,for dynamically compacted soils.The value of C could be reduced in accordance with the stress history.Har-rison and Blight ͑2000͒emphasized the relationship between C and some soil properties such as plasticity index,clay fraction and linear shrinkage.Harrison and Bligh ͑2000͒observed that,for residual soils,the relationship did not present good correlation.The effect of soil plasticity on the SWCC is displayed sche-matically in Fig.3͑a ͒,showing that the slope of the SWCC changes with the liquid limit when a log scale is used for repre-senting suction.This effect can be compared to the relationship between void ratio and effective overburden pressure for saturated soils presented by Skempton ͑1970͒.The general behavior of clay samples with different stress histories or different preparation pro-cedures is schematically shown in Fig.3͑b ͒.The behavior ob-served is also in agreement with data presented by Croney and Coleman ͑1954͒and Toll ͑1988͒.The SWCC for most soils with a liquid limit of more than 25%can be assumed to be a straight line between suctions of 100and 10,000kPa,on a semilog plot,regardless of the suction method used ͑McQueen and Miller 1974;Marinho and Chandler 1993͒.Some soils,such as residual soils,may present some predomi-nance of void size that induces a change in suction capacity at suction levels within the interval mentioned above.The soil state at the liquid limit has been used for relating soil properties.Burland ͑1990͒introduced the concept of intrinsic properties for saturated clays,which was based on the voidratioFig.1.General shape of soil–water characteristic curve according to pore sizedistributionFig.2.Relation between liquid limit and shrinkage limit for some soils ͓Holtz ͑1959͒;Fleureau et al.͑1993͒;Tuncer ͑1988͔͒Fig.3.Plasticity chartJOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING ©ASCE /MAY 2005/655D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .of samples prepared between the liquid limit ͑w L ͒and 1.5w L .The relationship between water content and stress during isotropic consolidation can be obtained provided the speciﬁc gravity of the soil is known.The results obtained from drying saturated clay are equivalent to the isotropic consolidation,provided the soil re-mains saturated ͑e.g.,Blight 1965͒.Reddi and Poduri ͑1997͒pre-sented a study in which the void ratio at the liquid limit was used to obtain the water retention properties of the soil at other states.Marinho and Pinto ͑1997͒,in discussing the work presented by Reddi and Poduri ͑1997͒,presented data showing the relationship between w L and the pore size distribution index ͑␭͒,based on the Brooks and Corey ͑1966͒model for undisturbed soils and soils prepared at the w L .Effect of Stress History on Soil–Water Characteristic CurveCroney and Coleman ͑1954͒were among the ﬁrst investigators to study the effect of the stress history of the sample on the SWCC.It is clear from the ﬁndings of this study that,for the same water content,overconsolidation induces a reduction in suction and as a consequence in suction capacity.The degree of saturation of an overconsolidated sample is always higher than that of a normally consolidated soil,provided the suction is higher than the air entry value of the normally consolidated sample.Toll ͑1988͒performed a series of tests and described the soil behavior during desatura-tion,presenting a framework for examining the relationship be-tween water content and volume change with suction.Toll ͑1988͒also presented the concept of a virgin desaturation line ͑VDL ͒,which is the line where,for some value of suction,the relation-ship between water content and logarithm of suction is unique ͓see Fig.3͑b ͔͒.The point at which soils in different initial states reach the VDL is associated with the air entry value.Delage and Lefebvre ͑1983͒used mercury intrusion porosimetry to show the effect of the stress history on the air entry value of plastic soils.Tests were performed on St.Marcel clay,consolidated at different stress levels,including dried samples.The results clearly indi-cated that the air entry value increases with the consolidationpressure and is even higher for samples previously dried.It should be pointed out that the air entry value increases with the overconsolidation of the soil but,as for saturated soils,the stress required to reach the same water content is lower.Vanapalli et al.͑1999͒performed a series of tests using a sandy clay till ͑Indian Head till ͒to deduce the effect of soil struc-ture and stress history on the SWCC.The samples were statically compacted,placed in an oedometer cell,soaked under constant volume,and mechanically loaded to different values of net nor-mal stress.After the required stress was reached,the samples were unloaded under drained conditions.The loading and unload-ing of the sample induced additional overconsolidation in the sample.The samples were then removed from the oedometer cell and the SWCC was obtained from a pressure plate.No correction for volume change was made when the degree of saturation was used to represent the SWCC.A negligible volume change of the soil during drying was observed.Vanapalli et al.͑1999͒observed a signiﬁcant difference in the SWCC ͑represented as degree of saturation versus suction ͒,particularly at the beginning of the curve ͑low suctions ͒,thus reﬂecting the macrostructure of the soil.The results also suggested that the increase in stress after compaction reduced the differences observed in the SWCC at low suctions.Relationship between Suction Capacity and Liquid LimitThere seems to be an upper limit for the suction capacity C ,and this is related to the samples prepared and tested from slurry.The upper limit for C also agrees well with the data for saturated clays presented by Burland ͑1990͒and shown by Marinho and Chan-dler ͑1993͒in terms of suction capacity.There also seems to be a lower limit for the suction capacity related to overconsolidated clays.The stress history of the sample plays an important role in its suction capacity.Hence,a compacted soil may be near the upper limit or near the lower limit for the C value.It depends on the level of stress to which the sample was subjected.For differentTable 1.Soils Analyzed Soil w 1͑%͒w p ͑%͒I p ͑%͒Reference1London clay 78.026.052Croney and Coleman ͑1954͒2Silty clay41.520.521Croney and Coleman ͑1954͒3Red clay from Kenya 95.035.060Coleman et al.͑1964͒4London clay70.024.046Marinho ͑1994͒5Taplow Terrace Brickearth 36.019.017Dumbleton and West ͑1968͒6Kaolinite 61.030.031Biarez et al.͑1987͒7Yellow clay 40.020.020Fleureau et al.͑1990͒8Residual soil48.029.019Marinho and Stuermer ͑1998͒9Residual of gneiss ͑from 1.6m depth ͒50.031.01910Residual of gneiss ͑from 3.0m depth ͒50.034.01611Residual of gneiss ͑from 4.4m depth ͒53.033.02012Residual of gneiss ͑from 6.0m depth ͒51.039.01213London clay77.029.048Marinho ͑1994͒1490%London clay/10%sand 69.024.045Marinho ͑1994͒1570%London clay/30%sand 54.019.035Marinho ͑1994͒1650%London clay/50%sand 40.017.023Marinho ͑1994͒1730%London clay/70%sand 24.018.06Marinho ͑1994͒18Carsington63.031.032Marinho ͑1994͒656/JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING ©ASCE /MAY 2005D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .samples of a soil compacted with the same energy but different water contents,little difference is observed in the suction capacity ͑e.g.,Marinho and Stuermer 2000͒.The SWCC determined by Marinho and Stuermer ͑2000͒started from the compaction water content,thus implying that only the micropores are controlling behavior.Simms and Yanful ͑2000͒observed that the pore size distributions of the micropores are similar,regardless of the com-paction water content.Even for nonplastic materials,such as the till tested by Watabe et al.͑2000͒,the effect of the compaction water content can be detected.Watabe et al.͑2000͒tested samples compacted at differ-ent initial water contents.The samples were dynamically com-pacted and saturated using backpressure.The results showed that the higher the degree of saturation after compaction,the higher the suction at the air entry value is.The SWCC shape obtained differed signiﬁcantly up to 300kPa,thereby showing the effect of the compaction water content on the initial portion ͑i.e.,macropores ͒of the SWCC.The effect of the stress history from a particular initial structure on the SWCC was not investigated by Watabe et al.͑2000͒.It should be pointed out that,although the till tested by Watabe et al.͑2000͒was a nonplastic material,it was a well-graded soil with clay content ͑%Ͻ2␮m ͒of 7%,silt con-tent of approximately 36%,and ﬁne sand content of about 30%.The clay content and grain size distribution of the nonplastic por-tion may be an important factor in the observed behavior.Normalization of Using Suction CapacityMarinho and Chandler ͑1993͒proposed the normalization of water content on the SWCC.It was found that the normalization of the SWCC applied to dynamically compacted soils gives a unique relationship for the soils analyzed.Models for Predicting Soil–Water Characteristic CurvesThere are several models available in the literature for predicting the SWCC using a limited quantity of data ͑e.g.,Black 1962;McQueen and Miller 1974;Gupta and Larson 1979͒.None of the suggested methods take into account the stress history of the soil.In order to obtain the complete SWCC,most of the available models divide the SWCC into segments.The geometrical and mathematical aspects of the ﬁtting method may justify the proce-dure of dividing the SWCC into segments.The models are also aimed at characterizing the physical meaning of the holding forces that are present at different levels of suction.McQueen and Miller ͑1974͒presented a procedure for deﬁning the SWCC based on one suction/water content measurement.A straight line on a semilog plot can,according to McQueen and Miller ͑1974͒,rep-resent the SWCC in the range between 30kPa and 10Mpa.It should be pointed out that this suction range can still be associ-ated with capillary water provided the pore sizes are equivalent to the suction.McQueen and Miller’s ͑1974͒method makes no ref-erence to the history of the soil specimen.Black ͑1962͒presented a method that correlates the plasticity index,water content and soil suction.The method was to be used for remolded soils and was based on results obtained using British clays.All data analyzed by Black ͑1962͒were above the A line on the plasticity chart and the relationship between soil suction and water content presented a well-deﬁned correlation with the plas-ticity index.In order to investigate possible relationships between theliq-Fig. 4.Schematic representation of relationship between water content and suction for:͑a ͒different soils in similar states and ͑b ͒same soil in differentstatesFig. 5.Soil–water characteristic curves for soil starting drying process fromslurry Fig.6.Soil–water characteristic curves for stiff soils upondryingFig.7.Soil–water characteristic curves for dynamically compacted samples upon dryingD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .uid limit,suction capacity and SWCC,previously reported data were collected and analyzed.The results presented in this paper show a consistent relation-ship between the slope of the SWCC ͑with suction in log scale ͒and the rigidity of the soil in relation to suction increase.This peculiar behavior suggests the possibility of adopting a simple model for deducing the SWCC.Soils Considered in AnalysisData from 42SWCCs from 18soils were analyzed.The Atterberg limits and the reference sources for the soils analyzed are shown in Table 1.Fig.4presents soils analyzed in this paper on a plas-ticity chart.It can be seen that most of the soils are located above the “A line.”Only the residual soils ͑8,9,10,11,and 12͒lie below the A line.Figs.5–8present the relationship between water content and soil suction for samples at initial state ranging from slurry to stiff material,including dynamically compacted and statically com-pacted,respectively.Even for the same type of sample ͑prepared from slurry,with dynamic compaction,etc.͒,the behavior can vary widely according to the soil type.In some cases slurry samples have low water content values,thereby indicating a low value for suction capacity,particularly at low suction levels.This behavior is associated with the storage capacity of the soil,and in this case it is more directly associated with soil mineralogy.This paper shows that the liquid limit can adequately reﬂect the rela-tionship between storage capacity and the stress history of the soil.The soil state that represents the association between water content and suction at failure conditions is called the “continu-ously disturbed state”͑e.g.,Croney and Coleman 1954;Brady 1988͒.After each suction measurement the sample is deliberately mixed or disturbed,to simulate a failure condition.The continu-ously disturbed state can also be identiﬁed as a critical state line for the SWCC ͑e.g.,Croney and Coleman 1954;Brady 1988͒.Fig.9presents the SWCC for continuously disturbed samples obtained from results presented by Croney and Coleman ͑1954͒,Dumbleton and West ͑1968͒,and Marinho ͑1994͒.Fig.10presents the relationship between suction capacity and liquid limit obtained from tests with samples at four different initial conditions.In addition to the data related to the soils pre-sented in Table 1,Fig.10also presents some data from the litera-ture,in which it was not possible to obtain the SWCC,but the suction capacity could be deduced ͑e.g.,Holmes 1955;Blight 1961;Matyas,1963;Olson and Langfelder 1965;Cepeda-Diaz 1987;Jucá1990;Ho et al.1992;Ridley 1995;Clarke and Neves,Jr.1996͒.From the analysis of the data collected from the literature,it was observed that the normalization with the suction capacitywasFig.8.Soil–water characteristic curves for statically compacted samples upondryingFig.9.Soil–water characteristic curves for continuously disturbedsamples Fig.10.Relationship between suction capacity and liquid limit for different samplehistoriesFig.11.Soil–water characteristic curve normalization using the suction capacityD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .not universal.The suction capacity alone cannot represent the SWCC of the soils.Some discrepancies were observed in the data used.The differences in the position of the SWCC can be ob-served in Fig.11,where the normalized water content is plotted against soil suction on a logarithmic scale.One important observation related to Fig.11is that most of the normalized data lay along parallel lines.This empirical behavior can be used to indirectly estimate the SWCC for plastic soils using only one suction/water content measurement and the soil–liquid limit,and using the empirical relation between the liquid limit and suction capacity ͑Fig.10͒.Deducing Soil–Water Characteristic Curve Using One Set of Data and Liquid LimitThe steps to be followed for obtaining the SWCC for soils with a liquid limit of more than 25%are described as follows:The At-terberg limits for the soil must be determined in order to certify that the soil lies above the A line on the plasticity ing the liquid limit and observing the soil state,the suction capacity can be determined using Fig.10.At least one value of water content ͑w i ͒and suction ͑suction i ͒needs to be obtained.Any method for suction measured can be used for determining the necessary suc-tion ing the ﬁlter paper method at least 7days is neces-sary for equilibrium.If a high capacity tensiometer ͑e.g.,Marinho and Pinto 1997͒is used,just few minutes are necessary.With the water content ͑w i ͒of the sample,Fig.12can be used to estimate the line related to the suction capacity obtained ing the interception point as a reference,a horizontal line is then traced.A vertical line is drawn at the value of the suction mea-sured ͑suction i ͒that is associated with the water content ͑w i ͒.The intersection between that vertical line and the horizontal traced line is a point on the line that relates the normalized water content͑w /C ͒and the soil suction.In order to convert the relationship between the normalized water content ͑w /C ͒and suction into the SWCC,the suction capacity ͑C ͒previously obtained is used.Applying MethodThree examples of the use of the method are presented using data from Bao and Ng ͑2000͒,Ridley ͑1995͒,and Vaunat and Romero ͑2000͒.However,experimental results obtained by Vaunat and Romero were not included in the data used for the development of the method.The data taken from the above references were the liquid limit and one suction/water content measurement,as shown in Table 2.Table 2also presents the parameters obtained from the method.A guide to the use of the method is presented for the soil shown by Bao and Ng ͑2000͒:1.The liquid limit of the soil is 63.5%and its plastic limit is27.3%͑Ng,personal communication,May 2001͒.2.The soil is above the A line in the plasticity chart.3.Since the soil is an undisturbed expansive soil,it is assumedthat the soil is heavily overconsolidated.From Fig.10,the suction capacity ͑C ͒is 5%.4.The values of water content and suction were obtained di-rectly from the reference,as shown in Table 2͑Bao and Ng 2000͒.5.By entering the water content in Fig.12,the intercept withthe dotted line corresponding to the C value is obtained in Fig.10.6.The interception point corresponds to a normalized watercontent ͑w /C ͒of 5.9.ing the suction value from Table 2,the line showing therelationship between normalized water content and suction is obtained.8.Assuming that C =5%,the value of the water content can beobtained for some points.Considering this is a graphical method,the linear relationship may not be accurately obtained.Fig.13presents the experimental data from Bao and Ng ͑2000͒,Ridley ͑1995͒,and Vaunat and Romero ͑2000͒,and a line representing the results obtained using the method.The results obtained when using the method for the soils presented by Bao and Ng ͑2000͒and Ridley ͑1995͒was reasonably good.The SWCC prediction for the soil presented by Vaunat and Romero ͑2000͒was also reasonable,although a small discrepancy was observed.This discrepancy obtained may be as-sociated with the interpretation of the stress history of the soil.ConclusionsFrom the analysis of data from 42SWCCs from 18soils obtained from the literature,it was possible to classify the behavior of the soil according to its nature ͑associated parameter w 1͒and its stress history ͑associated parameter C ͒.It was observed that soilsTable 2.Data from Literature and Parameters of Method ReferenceSample type w 1͑%͒Water content ͑%͒Suction ͑kPa ͒C ͑%͒w /C Bao and Ng ͑2000͒Undisturbed 63.5281005 5.9Ridley ͑1995͒Compacted643057012 2.5Vaunat and Romero ͑2000͒Compacted high density562245054.5Fig.12.Diagram for soil–water characteristic curve approximation using one data set and liquid limitJOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING ©ASCE /MAY 2005/659D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/17/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .。

Soil Water Characteristic Curve

Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated GeotechnicsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Advances in Unsaturated Geotechnics D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H a r b i n I n s t i t u t e o f T e c h n o l o g y o n 11/16/13. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .。

SOIL MECHANICS lecture

SOIL MECHANICSLECTURE NOTESLECTURE # 1SOIL AND SOIL ENGINEERING* The term Soil has various meanings, depending upon the general field in which it is being considered.*To a Pedologist ... Soil is the substance existing on the earth's surface, which grows and develops plant life.*To a Geologist ..... Soil is the material in the relative thin surface zone within which roots occur, and all the rest of the crust is grouped under the term ROCK irrespective of its hardness.*To an Engineer .... Soil is the un-aggregated or un-cemented deposits of mineral and/or organic particles or fragments covering large portion of the earth's crust.* Soil Mechanics is one of the youngest disciplines of Civil Engineering involving the study of soil, its behavior and application as an engineering material.*According to Terzaghi (1948): "Soil Mechanics is the application of laws of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixture of organic constituent."* Geotechnical Engineering ..... Is a broader term for Soil Mechanics.* Geotechnical Engineering contains:- Soil Mechanics (Soil Properties and Behavior)- Soil Dynamics (Dynamic Properties of Soils, Earthquake Engineering, Machine Foundation)- Foundation Engineering (Deep & Shallow Foundation)- Pavement Engineering (Flexible & Rigid Pavement)- Rock Mechanics (Rock Stability and Tunneling)- Geosynthetics (Soil Improvement)Soil Formation* Soil material is the product of rock* The geological process that produce soil isWEATHERING (Chemical and Physical).* Variation in Particle size and shape depends on:- Weathering Process- Transportation Process* Variation in Soil Structure Depends on:- Soil Minerals- Deposition Process* Transportation and DepositionFour forces are usually cause the transportation and deposition of soils1- Water ----- Alluvial Soil 1- Fluvial2- Estuarine3- Lacustrine4- Coastal5- Marine2- Ice ---------- Glacial Soils 1- Hard Pan2- Terminal Moraine3- Esker4- Kettles3- Wind -------- Aeolin Soils 1- Sand Dunes2- Loess4- Gravity ----- Colluvial Soil 1- TalusWhat type of soils are usually produced by the different weathering & transportation process?- Boulders- Gravel Cohesionless- Sand (Physical)- Silt Cohesive- Clay (Chemical)* These soils can be- Dry- Saturated - Fully- Partially* Also they have different shapes and texturesLECTURE # 2SOIL PROPERTIESPHYSICAL AND INDEX PROPERTIES1- Soil Composition- Solids- Water-Air2- Soil Phases- Dry- Saturated * Fully Saturated* Partially Saturated- Submerged3- Analytical Representation of Soil:For the purpose of defining the physical and index properties of soil it is more convenient to represent the soil skeleton by a block diagram or phase diagram. 4- Weight - Volume Relationships:WeightW t = W w + W sVolumeV t = V v + V s = V a + V w + V s 1- Unit Weight - Density* Also known as- Bulk Density- Soil Density-Unit Weight-Wet DensityRelationships Between Basic Properties:Examples:________________________________________________________________________Index PropertiesRefers to those properties of a soil that indicate the type and conditions of the soil, and provide a relationship to structural properties such as strength, compressibility, per meability, swelling potential, etc.________________________________________________________________________1- PARTICLE SIZE DISTRIBUTION* It is a screening process in which coarse fractions of soil are separated by means of series of sieves.* Particle sizes larger than 0.074 mm (U.S. No. 200 sieve) are usually analyzed by means of sieving. Soil materials finer than 0.074 mm (-200 material) are analyzed by means of sedimentation of soil particles by gravity (hydrometer analysis).1-1 MECHANICAL METHODU.S. Standard Sieve:Sieve No. 4 10 20 40 60 100 140 200 -200Opening in mm 4.76 2.00 0.84 0.42 0.25 0.149 0.105 0.074 -Cumulative Curve:* A linear scale is not convenient to use to size all the soil particles (opening from 200 mm to 0.002 mm).* Logarithmic Scale is usually used to draw the relationship between the % Passing and the Particle size.Example:Parameters Obtained From Grain Size Distribution Curve:1- Uniformity Coefficient C u (measure of the particle size range)Cu is also called Hazen CoefficientCu = D60/D10C u < 5 ----- Very UniformC u = 5 ----- Medium UniformC u > 5 ----- Nonuniform2- Coefficient of Gradation or Coefficient of Curvature C g(measure of the shape of the particle size curve)C g = (D30)2/ D60 x D10C g from 1 to 3 ------- well graded3- Coefficient of Permeabilityk = C k (D10)2 m/secConsistency Limits or Atterberg Limits:- State of Consistency of cohesive soil1- Determination of Liquid Limit:2- Determination of Plastic Limit:3- Determination of Plasticity IndexP.I. = L.L. - P.L. 4- Determination of Shrinkage Limit5- Liquidity Index:6- Activity:SOIL CLASSIFICATION SYSTEMS* Why do we need to classify soils ?To describe various soil types encountered in the nature in a systematic way and gathering soils that have distinct physical properties in groups and units.* General Requirements of a soil Classification System:1- Based on a scientific method2- Simple3- Permit classification by visual and manual tests.4- Describe certain engineering properties5- Should be accepted to all engineers* Various Soil Classification Systems:1- Geologic Soil Classification System2- Agronomic Soil Classification System3- Textural Soil Classification System (USDA)4-American Association of State Highway Transportation Officials System (AASHTO) 5- Unified Soil Classification System (USCS)6- American Society for Testing and Materials System (ASTM)7- Federal Aviation Agency System (FAA)8- Others1- Unified Soil Classification (USC) System:The main Groups:G = GravelS = Sand.........................M = SiltC = Clay........................O = Organic........................* For Cohesionless Soil (Gravel and Sand), the soil can be Poorly Graded or Well GradedPoorly Graded = PWell Graded = W* For Cohesive Soil (Silt & Clay), the soil can be Low Plastic or High Plastic Low Plastic = LHigh Plastic = HTherefore, we can have several combinations of soils such as:GW = Well Graded GravelGP = Poorly Graded GravelGM = Silty GravelGC = Clayey GravelPassing Sieve # 4SW = Well Graded SandSP = Poorly Graded SandSM = Silty SandSC = Clayey SandPassing Sieve # 200ML = Low Plastic SiltCL = Low Plastic ClayMH = High Plastic SiltCH = High Plastic ClayTo conclud if the soil is low plastic or high plastic use Gassagrande's Chart________________________________________________________________________ 2- American Association of State Highway Transportation Officials System (AASHTO):- Soils are classified into 7 major groups A-1 to A-7Granular A-1 {A-1-a - A-1-b}(Gravel & Sand) A-2 {A-2-4 - A-2-5 - A-2-6 - A-2-6}A-3More than 35% pass # 200A-4Fine A-5(Silt & Clay) A-6A-7Group Index:_________________________________________________ ___3- Textural Soil Classification System (USDA)* USDA considers only:SandSiltClayNo. Gravel in the System* If you encounter gravel in the soil ------- Subtract the % of gravel from the 100%.* 12 Subgroups in the systemExample: ********MOISTURE DENSITY RELATIONSHIPS(SOIL COMPACTION)INTRODUCTION:* In the construction of highway embankments, earth dams, and many other engineering projects, loose soils must be compacted to increase their unit weight.* Compaction improves characteristics of soils:1- Increases Strength2- Decreases permeability3- Reduces settlement of foundation4- Increases slope stability of embankments* Soil Compaction can be achieved either by static or dynamic loading:1- Smooth-wheel rollers2- Sheepfoot rollers3- Rubber-tired rollers4- Vibratory Rollers5- Vibroflotation_____________________________________________________________________________________________General Principles:* The degree of compaction of soil is measured by its unit weight, , and optimum moisture content, w c.* The process of soil compaction is simply expelling the air from the voids.or reducing air voids* Reducing the water from the voids means consolidation.Mechanism of Soil Compaction:* By reducing the air voids, more soil can be added to the block. When moisture is added to the block (water content, w c, is increasing) the soil particles will slip more oneach other causing more reduction in the total volume, which will result in adding moresoil and, hence, the dry density will increase, accordingly.* Increasing W c will increaseUp to a certain limit (Optimum moister Content, OMC)After this limitIncreasing W c will decreaseDensity-Moisture RelationshipKnowing the wet unit weight and the moisture content, the dry unit weight can be determined from:The theoretical maximum dry unit weight assuming zero air voids is:I- Laboratory Compaction:* Two Tests are usually performed in the laboratory to determine the maximum dry unit weight and the OMC.1- Standard Proctor Test2- Modified Proctor TestIn both tests the compaction energy is:1- Standard Proctor TestFactors Affecting Compaction:1- Effect of Soil Type2- Effect of Energy on Compaction3- Effect of Compaction on Soil Structure4- Effect of Compaction on Cohesive Soil PropertiesII- Field CompactionFlow of Water in SoilsPermeability and Seepage* Soil is a three phase medium -------- solids, water, and air* Water in soils occur in various conditions* Water can flow through the voids in a soil from a point of high energy to a point of low energy.* Why studying flow of water in porous media ???????1- To estimate the quantity of underground seepage2- To determine the quantity of water that can be discharged form a soil3- To determine the pore water pressure/effective geostatic stresses, and to analyze earth structures subjected to water flow.4- To determine the volume change in soil layers (soil consolidation) and settlement of foundation.* Flow of Water in Soils depends on:1- Porosity of the soil2- Type of the soil - particle size- particle shape- degree of packing3- Viscosity of the fluid - Temperature- Chemical Components4- Total head (difference in energy) - Pressure head- Velocity head- Elevation headThe degree of compressibility of a soil is expressed by the coefficient of permeability of the soil "k."k cm/sec, ft/sec, m/sec, ........Hydraulic GradientBernouli's Equation:For soilsFlow of Water in Soils1- Hydraulic Head in SoilTotal Head = Pressure head + Elevation Headh t = h p + h e- Elevation head at a point = Extent of that point from the datum- Pressure head at a point = Height of which the water rises in the piezometer above the point.- Pore Water pressure at a point = P.W.P. = g water . h p*How to measure the Pressure Head or the Piezometric Head???????Tips1- Assume that you do not have seepage in the system (Before Seepage)2- Assume that you have piezometer at the point under consideration3- Get the measurement of the piezometric head (Water column in the Piezometer before seepage) = h p(Before Seepage)4- Now consider the problem during seepage5- Measure the amount of the head loss in the piezometer (Dh) or the drop in the piezometric head.6- The piezometric head during seepage = h p(during seepage) = h p(Before Seepage) - DhGEOSTATIC STRESSES&STRESS DISTRIBUTIONStresses at a point in a soil mass are divided into two main types:I- Geostatic Stresses ------ Due to the self weight of the soil mass.II- Excess Stresses ------ From structuresI. Geostatic stressesI.A. Vertical StressVertical geostatic stresses increase with depth, There are three 3 types of geostatic stresses1-a Total Stress, s total1-b. Effective Stress, s eff, or s'1-c Pore Water Pressure, uTotal Stress = Effective stress + Pore Water Pressures total = s eff + uGeostatic Stress with SeepageWhen the Seepage Force = H g sub -- Effective Stress s eff = 0 This case is referred asBoiling or Quick ConditonI.B. Horizontal Stress or Lateral Stresss h = k o s'vk o = Lateral Earth Pressure Coefficients h is always associated with the vertical effective stress, s'v.never use total vertical stress to determine s h.II. Stress Distribution in Soil Mass:When applying a load on a half space medium the excess stresses in the soil will decrease with depth.Like in the geostatic stresses, there are vertical and lateral excess stresses.1. For Point LoadThe excess vertical stress is according to Boussinesq (1883):- I p = Influence factor for the point load- Knowing r/z ----- I1 can be obtained from tablesAccording to Westergaard (1938)where h = s (1-2m / 2-2m) m = Poisson's Ratio2. For Line LoadUsing q/unit length on the surface of a semi infinite soil mass, the vertical stress is:3. For a Strip Load (Finite Width and Infinite Length): The excess vertical stress due to load/unit area, q, is:Where I l = Influence factor for a line load3. For a Circular Loaded Area:The excess vertical stress due to q is:。

Soil - Water presentation IAgE PMisciewicz230513

Soil and Water Management in Responseto Extreme WeatherPaula MisiewiczHarper Adams UniversityOptions for Soil Management in 2012-2013:Tillage and DrainageOutlineFundamentalsThe problem and the penaltiesS&W Management Options Short termMedium termLong termConclusionsTypical problemsA less common sceneWaterlogging treatment Grain Yield (g/m²)Straw Yield (g/m 2)Free draining 937942From 19 Nov for 25 daysWater table @ 5 cm837*879***From 19 Nov for 25 daysSurface water table850*827***From 19 Nov for 120 daysSurface water table876847***LSD (5%)8510.7% reduction Effect of winter waterlogging on Winter wheat yield (Letcombe)Sandy loam 1976-7 & 1977-812.2% reductionSource: Belford (1981), J. Agric. Sci, 97Waterlogging treatment Grain Yield (g/m²)Straw yield (g/m²)1. Free draining 12818612. From 1 Nov for 42 days 11958753. From 25Jan for 42 days 12358574. From 2 May for 21 days 11318022 &3 & 41044**782LSD (5%)1679119 % reductionThe Role of Drainage onMechanisationIncreasing water table depth:o Increases soil strength &trafficabilityo Less soil damage orcompaction.o Easier& more effective fieldoperations.o Increased number of availablework days, improvedtimeliness and establishment.From :ProfiLand drainage and crop yieldCrop failure –during growth, in this case ~25% lossSoya beans, Illinois -July 2008Effect on crop growth –Denchworth SoilFDEU studies at Drayton 1970 -74 Winter WheatYield ~4.5 t/haDrains & Moles + 1.0 t/haDrains No moles & subsoiling+ 0.6 t/haStudies at Brooksby showed + 0.5t/ha from molingBirds Eye lost 40% of pea yield in summer of2007 due to poor trafficabilityFDEU Annual Report 1975Water budgetPrincipal types of drainage problem1.Surface water control (perched water table or top water)2.Groundwater table control (bottom water)Impermeable layerImpermeable layerSaturated zoneRelationship betweencompaction and infiltration rateAfter: Chyba, 20121.42 1.58 1.62 1.62Soil Density g/ccInfiltrationrate(mm/Effect of organic matter•Silt loam soils in Missouri:organic matter decline from 3.9% to 2.6% over 60 years.•This corresponded to a change in plastic limit moisture content from 27% to 22% and a less ideal working range.After: Baver et. al., 1972Hard Friable Plastic Liquid HardFriablePlasticLiquid3.9%2.6%Soil moisture contentIdeal working rangeDryWetShort term measures•Study “Old Drainage Plans”•Walk ditch drains•Check that tile drains, plastic pipes and mole drains are flowing•Clean blocked ditch and open drains•Flush pipe drains•Ensure outfalls are functioning•Install “short term” mole drains if appropriate•Map damaged areas for repair later in the season/next opportunityClean ditchesDrainage Maintenance:Pipe Jetting for Blockages13Mole drain/pipe from the ditchFit duals and reduce inflation pressureShallow, i.e.12-15” deep, mini-mole with 2’’ diameter foot.No -Expander+ 2nd tractor &chains or winch Herringbone cracksMole plough draught forces 1/3 of the force at 0.6m “Mini mole” depthConventional mole depthAfter: Godwin, Spoor & Leeds Harrison, 1982Medium term•Mole drain clay soils with perched water tables to connect with gravel backfill of existing tile/plastic drains•Subsoil (with wings) damaged areas after next harvest •Improve existing drainage systemsLong term measures•Install pipe/ditch drains (probably targeted)•Mole drain clay soils with perched water tables to connect with gravel backfill•Install grass waterways•Grade low spots in flat lands•Improve existing drainage systems•Reduce surface compaction by reducing traffic density and intensity (CTF and LGP)•Improve soil organic matter content (a very long term effect)Grass waterways/USDALand smoothing of low spotsAfter: Schwab et al 1993Random Traffic ProblemsExtensive areas of the field are exposed to trafficking•Random Traffic + plough = 85% covered•Minimum Tillage= 65% covered•Direct Drilling= 45% covered Kroulik et al, 2011grain cartingstraw carting straw baling Wheat Czech RepublicPotatoesShropshireKroulik , Misiewicz, White and Godwin, 2012After: Tullberg et al. 2003Reduced pressure/axle weight and central tyre inflation pressurecontrol systemsOptions for compaction reductionControlled trafficSource: CTF EuropeControlled Traffic Farming (CTF)•Area exposed to wheels < 30-40% & could be <20%•Improved soil structure•Reduced input costs: time; fuel; machinery by 22%•Operating profit up 8% (£75/ha without yield addition)•Increased crop yields from non trafficked soils + 9 to16%•Infiltration increased by circa 400% in UKSource: Chamen, 2011Lower Ground Pressure (LGP)+ Simple+ Cheap-Pressure is applied+ Less working time and improved fuel economy, trafficability andmanoeuvrabilityCombine: + £3 to 4/ha for 5 -7 year lifePrice offset by improved trafficability and narrower operatingwidthsTyrell, Claas UKExtra costsTractor -280 hp : Ultraflex tyres extra = £1/haCombine: Ultraflex = £0.50/haPrice offset by fuel savings (c.20%)Mozziconacci, MichelinEffect of infiltration rate on runoffParrett and Tone Catchment, Dorset/Somerset@ Haselbury Plucknet/ChiselboroughRainfallRainfallRainfallRainfallRainfallandrunoffrates(mmh-1)23rd December25th December24th Decemberq poor=0.72q good-Infiltration Rate 4-8 mm/hrq poor=1.6q poor=3.3q good =1.23q good=2.6q goodq poor=0.89q poor=1.7q good=1.35^^^^^^^^^^||||25%23% 21%19%% Reduction in peak flow After: Godwin and Dresser, 2003From: Schwab et al., 1993Infiltration Rate1-4 mm/hr25Regular inspections of drainage systems are needed.Restoration of an old system is cheaper than a new system.Improved soil and water management is achieved by:•Considering the short, medium and longer term actions •Checking, maintaining and improving drainage infrastructure •Reducing traffic intensity & contact pressurePrevention is better than cureConclusionsThank You!pmisiewicz@。

第四章土壤物理性质ppt课件

土壤密度与4℃时纯水密度之比，一般取2.65。
二、土壤容重(bulk density of soil)
1. 概念: 单位体积自然状态土壤体（原状土）（含粒间孔隙）的重量（干重）。（g/cm3） 2. 土壤容重(soil bulk density)作用 (1)计算土壤孔隙度(soil porosity)
三、土壤孔性
（一）概念土壤总孔度、大小孔隙分配、孔隙在土体中分布。（二）孔隙度(soil porosity)
土壤全部孔隙容积(pore volume)占土体容积的百分率。
水和空气共存并充满于土壤孔隙中。
2. 土壤三相组成及孔度计算总孔度(total porosity)＝ (1－容重/密度) ×100% 固相(solid phase)＝(容重/密度) ×100% 液相(liquid phase)＝(水分重量百分率×容重) ×100% 气相(gas phase)＝(总孔度－液相) ×100% 土壤三相比＝固相:液相:气相
增加介质中电解质浓度也可促进胶粒凝聚。农业生产中，常采用排水晒田、晒垄、冻垄等措施，提高土壤溶液电解质的浓度，促进土壤胶粒凝聚。
（2）水膜(water film)的粘结作用土粒在水膜的作用下，在土粒接触处形成弯月
面，由于弯月面内侧的负压，把相邻的土粒团聚在一起，形成土团。（3）胶结作用(cementation) a、简单的无机胶体(simple soil mineral colloid)
水分结冰时体积膨胀增大约9%，对周围的土体产生压力而使土壤崩裂。
孔径愈小，其中水分冰点愈低。造成膨压的差异使土体产生裂痕，一旦融化，土壤就会沿裂痕酥散。
(3)生物作用(biological effect) a、植物根系的穿插挤压，可使土体破碎形成结构。 b、土壤中的蚯蚓、昆虫、蚁类等，对土壤结构形成

Microsoft PowerPoint - 第二章土壤性质

6
４．盐基饱和度（Ｂａｓｅｓａｔｕｒａｔｉｏｎｐｅｒｃｅｎｔａｇｅ）
盐基饱和度与土壤酸碱性的关系：土壤中交换性盐基离子（K+、 Na +、NH 4+、 Ca 2+ 、 M g 2+等）总量占阳离子交换量的百分数。我国干旱半干旱的北方地区，土壤盐基饱和度大，土壤的pH 值高；多雨湿润的南方地区，土壤盐基饱和度小，土壤pH 值低。盐基饱和度与土壤肥力的关系：盐基离子(B ases) ：K+、Na +、NH 4+、Ca 2+、M g 2+ 等。酸离子（Aci di c i ons ）：H +、Al 3+离子。盐基饱和度>80 % —— 肥沃；盐基饱和度50 %~80% —— 肥力中等；盐基饱和度<50 % —— 肥力较低。
土壤物理化学吸收性的基础
同晶代换
来源
负电，不受介质pH影响
阳离子交换作用
K + 的吸附过程 K + ads o rptio n
永久电荷
土壤胶体
为什么带电？
主要带负电荷（决定电位离子层）
土壤胶粒
Ca NH 4
+ 3K+
土壤胶粒
K K K
+ Ca 2+ + NH 4+
可变电荷
来源
分子(原子)解离
比表面积＝表面积/质量
Specific surface area ＝surface area / weight 由于表面的存在而产生的能量叫做表面能。由于表面的存在而产生的能量叫做。胶体的粒径越小，比表面积越胶体的粒径越小，比表面积越大，表面能也越，表面能也越大，吸附能力也，吸附能力也越强。。1g土壤胶体比表面积一般有200 200-300m2 。粒级粗砂粒中粉粒粗粘粒胶粒直径（µ m）

第三章土壤水分ppt课件

吸湿水 (hydroscopic water) 物理束缚水
膜状水 (membrane/film water)
毛管水
毛管上升水
自由水
(capillary water)
(ascending capillary water)
（free water）
重力水
毛管悬着水
(hanging capillary water)
•Water which is absorbed from atmospheric vapor and held tightly to the soil granule.
氢键
HH
范德华 A
A
力库仑力
EE
HH
A
A
EE
water vapor
土壤学与农作学
H
H
R
R
E
E
hygroscopic water layer
土壤吸湿水的最大值；水吸力3.1MPa
2. 凋萎系数（wilting coefficient）：植物产生永久凋萎（permanent wilting）时土壤的含水量。植物可利用的土壤水量（有效水）的下限。
吸湿水＋部分膜状水；水吸力 1.5MPa ；吸湿系数的 1.5～2.0倍
土壤(学gra与vit农atio作na学l water)
认识到了贫困户贫困的根本原因，才能开始对症下药，然后药到病除。近年来国家对扶贫工作高度重视，已经展开了“ 精准扶贫”项目
1、吸湿水（紧束缚水）
hygroscopic/hydroscopic water
• 吸湿水：干燥土粒从大气和土壤空气中吸附的气态水分

Soil and Water Cons

Soil & Water ConservationCourse Code: 5627COURSE DESCRIPTION:The Soil and Water Conservation course is a combination of subject matter and planned learning experiences on the principles involved in the conservation and/or improvement of soil and water resources for economic and recreational purposes. Typical learning activities include erosion control, land use planning, site surveying and profile leveling techniques, drainage and irrigation systems, constructing and maintaining ponds and dams, participating in personal and community leadership development activities, planning and implementing a relevant school-to-work transition experience, and participating in FFA activities.This course is a component of the following Agriculture, Food and Natural Resources Pathways: ∙Environmental and Natural Resources Management∙Agricultural Mechanics and TechnologyOBJECTIVE:Given the necessary equipment, supplies, and facilities, the student, upon completion of the prescribed number of instructional hours, will be able to successfully complete the following core competencies. Credit: 1 unitRECOMMENDED TEXTBOOK:Managing our Natural Resources –Thomson / DelmarADDITIONAL RESOURCES:Environmental Resources Lesson Plan Library –CAERT, Inc.Agricultural Mechanics and Technology Lesson Plan Library –CAERT, Inc.Natural Resources –Prentice Hall / InterstatePond Construction, Some Practical Considerations –Virginia Cooperative Extension Publication 420-011Advisor’s Guide to the FFA Student Handbo okUnit A Developing Leadership Skills in AgricultureLesson 1. Planning and Organizing an FFA MeetingStudent Learning Objectives:. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain how to plan a meeting and develop the order of business.2. Describe how to set up the meeting room.3. Explain the parliamentary procedure used in an FFA meeting.Lesson 2. Developing an Awareness for Your CommunityStudent Learning Objectives:. Instruction in this lesson should result in students achieving the followingobjectives:1. Describe the meaning and importance of community service.2. List and identify community service organizations.3. Explain how FFA members can be involved with community improvement and development.Lesson 3. State FFA DegreeStudent Learning Objectives:. Instruction in this lesson should result in students achieving the followingobjectives:1.List the requirements for the State FFA Degree.2.Explain how a FFA member can obtain the State FFA Degree.Unit B Supervised Experience in AgricultureLesson 1. Keeping and Using SAE RecordsStudent Learning Objectives: Instruction in this lesson should result in students achieving the followingobjectives:1. Explain how SA E records are organized.2. Identify the procedures to making entries in the SA E records.3. Explain how to summarize and analyze the SA E records.Lesson 2. Making Long Range Plans for Expanding SAE ProgramsStudent Learning Objective: Instruction in this lesson should result in students achieving the followingobjectives:: 1. Identify the factors that should be considered in expanding an SA E program.2. Explain how placement and ownership SAE programs may be expanded.Unit C: Soil & Land ResourcesLesson 1: Soil CharacteristicsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Outline the processes involved in soil formation.2.Describe a mature soil profile.3.Discuss the eight land capability classes4.Define soil series and explain how those differ from land capability classes5.Properly classify a given soil.Lesson 2: Soil ErosionStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Differentiate between natural soil erosion and soil erosion caused by humans.2.List the main causes of accelerated soil erosion3.List and define the major types of soil erosionLesson 3: Controlling Erosion on the FarmStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Explain how land capability classes relate to wise soil use2.Describe the main vegetation methods farmers use to control water-caused soil erosion.3.Describe the main mechanical methods farmers use to control water-caused soil erosion.4.Describe the control measures farmers use to control wind-caused erosion.5.Explain why soil erosion control should be important to every farmer.Lesson 4: Non-Farm Erosion ControlStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Describe the major forces of non-farm soil erosion2.Explain why non-farm landowners should accept responsibility for erosion control on their land.3.Explain the relationship between mining or construction and erosion.4.Describe some important techniques used in controlling non-farm erosionLesson 5: Land-Use PlanningStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Explain why land-use planning is important to our ecosystem and to our economy2.Differentiate between farmland-use planning and political land-use planningpare farming for intermediate income and farming for long-term income as they relate to soilconservation.4.Explain why economic development for short-term profit can be damaging to the economy as a whole interms of long term soil erosion.5.Properly read and evaluate Soil Survey maps for specific counties.e soil survey maps to determine land class, soil type, and recommendations of land use.Lesson 6: Understanding Soil Drainage SystemsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Identify the soil characteristics that effect soil drainage.2. Explain what needs to be considered when designing a drainage system.3. Identify the different types of soil drainage systemsUnit D: Soil and Environmental Technology SystemsLesson 1: Understanding Land Measurement and Legal DescriptionsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the purpose of land measurement and legal descriptions.2. Identify the systems of land measurement and legal description used in the United States.3. Discuss the causes of irregular townships and sections.Lesson 2: Using Surveying EquipmentStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the proper use of the equipment for a taping exercise.2. Explain the proper use of the hand sighting level.3. Explain the proper use of the tripod level.4. Explain the proper way to read a leveling rod.Lesson 3: Applying Profile Leveling TechniquesStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the important aspects of keeping survey notes for a profile survey.2. Explain the steps involved in completing a profile survey exercise.3. Explain how to calculate allowable error in a survey exercise.Lesson 4: Applying Differential Leveling TechniquesStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the important aspects of keeping survey notes for a differential survey.2. Explain the steps involved in completing a differential survey exercise.3. Explain how to calculate allowable error in a survey e xercise.Unit E: WaterLesson 1: Understanding the Water Cycle and Its Importance to the EnvironmentStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Describe the water cycle.2. Describe the physical and chemical makeup of water.3. Identify bodies of flowing water.4. Identify bodies of non-flowing water.Lesson 2: Determining Uses of WaterStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the importance of water.2. Define potable water.3. Identify methods of water management.Lesson 3: Identifying Water Sources and Quality StandardsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Identify sources of water.2. Describe factors used to determine water quality.3. Describe when and what to test for.Lesson 4: Identifying and Reducing Water PollutionStudent Learning Objecti ves. Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the difference between point and non-point source pollution.2. Identify sources of water pollution.3. Identify ways that water can be preserved and protected.Lesson 5: Maintaining WatershedsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Define watershed.2. Explain the importance of watersheds.3. Identify the features of a watershed.4. Explain how to manage a watershed.Lesson 6: Conducting Water Quality TestsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Define water quality monitoring.2. Identify types of physical monitoring.3. Explain water testing.Lesson 7: Tracking Groundwater ContaminationStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Define groundwater.2. List causes of groundwater contamination.3. Explain the severity of groundwater conservation.Lesson 8: Water Purification and Wastewater TreatmentStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Outline the kinds of impurities that must be removed from water for use by humans.2.Explain how water is purified in the municipal water treatment systems3.List and describe the kinds of wastewater generated4.Describe how septic systems are designed and how they work5.Conduct a percolation test6.Discuss how wastewater is treated before it is returned to the water cycleLesson 9: Drainage and Irrigation TechnologyStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.State the reasons for draining soils2.Describe the basic elements of a drainage system3.State the benefits of irrigation4.Identify and discuss the common types of irrigation systemse soil moisture sensors6.Relate cost factors involved with irrigation systems7.Design a sprinkler system8.Explain the maintenance of irrigation systems used in agriculture9.Identify and describe the types of electric irrigation pumps10. Properly install an irrigation pump11. Describe the calibration of irrigation systems used in agriculture.12. Discuss the benefits of a Drip Trickle Irrigation system.Unit F: Planning, Constructing, and Maintaining PondsLesson 1: Uses of PondsStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discuss the various uses of ponds.2.List and describe the basic types of pondsLesson 2: Selecting a Pond SiteStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discuss pond safety2.Discuss the soil types that are most suitable for ponds3.Discuss how geology is important to a pond selection site4.Discuss how the topography relates to pond construction costs5.Discuss how watersheds/drainage areas pertain to the selection of a pond site.Lesson 3: Pond Design and LayoutStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discuss the technical assistance available for pond design2.Discuss how to determine the proper size of the pond3.Discuss techniques in pond shaping4.List and describe the water control structures used in pondspare and contrast the uses of the principal spillway and the emergency spillway.Lesson 4: Pond ConstructionStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discus the permit requirements for pond construction2.Proper conduct a site analysis and read a site survey to determine the proper pon d lay out for a given area.3.Discuss the construction cost and construction equipment need for pond construction.4.Discuss the steps in site preparation for pond construction.Lesson 5: Dam ConstructionStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discuss the types of dams used in pond construction2.Determine the best soil type for a proper dam3.Determine the best slope for a dam4.Properly survey a site for an earthen dam designed for a farm pond.Lesson 6: Pond Maintenance1.Discuss proper maintenance techniques used on dams and spillways.2.Discuss how to control vegetation on pond banks and dams3.Discuss pond pest control4.Discuss aquatic weed control5.Determine stocking rates for fish ponds6.Discuss the use of riprap for pondsUnit G: Careers in Soil Water ConservationLesson 1: Careers in Soil ManagementStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Outline several career areas in soil and range management2.Describe some of the things people in those careers do3.List the kinds of training needed for entry into those careersLesson 2: Careers in Water ManagementStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1.Discuss the jobs, working conditions, and salaries of a career in water management.Unit H Developing Communication SkillsLesson 1—Introduction to CommunicationStudent Learning Objectives: Instruction in this lesson should result in students achieving the followingobjectives:1. Define communication and explain its purpos e.2. Identify the components of the communication process.3. Identify the five different levels of communication.4. Explain the barriers of successful communication.5. Explain the relationship between communication and leadership.Lesson 2—Organizing and Presenting a Persuasive MessageStudent Learning Objectives: Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the steps in preparing a persuasive message.2. Describe delivery techniques in a persuasive message.Lesson 3—Using Communication Skills In Appropriate SituationsStudent Learning Objectives: Instruction in this lesson should result in students achieving the followingobjectives:1. Understand the role of communication skills in the workplace.2. Understand how to present a problem to a supervisor.3. Identify the techniques used in requesting information from a supervisor.4. Explain the role of written communication in an agribusiness.Unit I Gaining EmploymentLesson 1—Developing GoalsStudent Learning Objectives: Instruction in this lesson should result in students achieving the followingobjectives:1. Explain the process of goal setting.2. Describe the terms and types of goals.3. Explain some aspects of effective goals.Lesson 2—Finding a JobStudent Learning Objectives. Instruction in this lesson should result in students achieving the followingobjectives:1. Describe information sources for job opportunities.2. Develop a system to evaluate job openings.Lesson 3—Applying for a Job1. Explain how to research a job opportunity.2. Describe two methods of applying for a job.3. Identify the common types of information requested on a job application form..Lesson 4—Writing a Résumé and Letter of ApplicationStudent Learning Objectives. Instruction in this lesson should result in students achieving the following objectives:1. Explain the purpose of a résumé.2. List the main items that should be included in a résumé.3. Describe the purpose of a letter of application and its primary elements.。

土壤学中英文对照名词

土壤学中英文对照名词土壤soil 陆地表面由矿物质、有机物质、水、空气和生物组成，具有肥力,能生长植物的未固结层。

土壤学soil science 研究土壤的形成、分类、分布、制图和土壤的物理、化学、生物学特性、肥力特征以及土壤利用、改良和管理的科学。

发生土壤学pedology 侧重研究土壤的发生、演化、特性、分类、分布和利用潜力的土壤学。

耕作土壤学edaphology 侧重研究土壤的组成、性质及其与植物生长的关系，通过耕作管理提高土壤肥力和生产能力的土壤学.土壤地理［学］soil geography 研究土壤的空间分布和组合及其地理环境相互关系的学科.土壤物理［学] soil physics 研究土壤中物理现象或过程的学科。

土壤化学soil chemistry 研究土壤中各种化学行为和过程的学科。

土壤生物化学soil biochemistry 阐明土壤有机碳和氮素等物质的转化、消长规律及其功能的学科.土壤矿物学soil mineralogy 研究土壤中原生矿物和次生矿物的类型、性质、成因、转化和分布的学科。

01.011 土壤分析化学soil analytical chemistry 研究用化学方法和原理测定土壤成分和性质的技术学科. 01。

012 土壤生物学soil biology 研究土壤中生物的种类、分布、功能及其与土壤和环境间相互关系的学科.01.013 土壤微生物学soil microbiology 研究土壤中微生物种类、功能和活性以及与土壤和环境间相互关系的学科。

01.014 土壤生态学soil ecology 研究土壤环境与生物间相互关系，以及生态系统内部结构、功能、平衡与演变规律的学科。

01.015 土壤微形态[学］soil micromor—phology 研究土壤显微形态特征的学科.01。

016 土壤资源soil resources 土壤类型的数量与质量。

01.017 土壤区划soil regionalization 按土壤群体的地带性和地域性差异进行分区划片，提出开发利用途径。

石灰改良土的土水特征曲线及其冻结特征曲线

第40卷第6期2020年12月Vol.40No.6Dec.2020防灾减灾工程学报Journal of Disaster Prevention and Mitigation EngineeringDOI：10.13409/ki.jdpme.2020.06.016石灰改良土的土水特征曲线及其冻结特征曲线，王叶娇I,王有为I,靳奉雨I,马田田2"(1.上海大学土木工程系，上海200444；2.中国科学武汉岩土力学研究所，湖北武汉430071；3.岩土力学与工程国家重点实验室，湖北武汉430071)摘要：土水特征曲线反映了非饱和土的持水特性，与土体的水力特性及力学特性密切相关。

土的冻结特征曲线表示土体中液态水的势能与含水率之间的关系，也可以用来描述土体的持水特性。

以黄土为研究对象，利用低温恒温冷浴结合核磁共振系统(NMR)测得未处理黄土以及石灰改良土的冻结特征曲线，根据冻结温度降低法计算得出试验土样0°C时对应的土水特征曲线。

另外，采用滤纸法在0°C附近得到实测的土水特征曲线，将这两结果进行对比分析，并讨论了抽真空饱和过程对土样的土水特征曲线的影响。

通过滤纸法测得的土水特征曲线与非饱和土样的冻结特征曲线具有较好的一致性，两者之间存在差异很小。

土样在饱和状态下利用冻结温度降低法得到的孔隙水总势能#与质量含水率w关系曲线位于非饱和土样结果的下方，这可能是因为饱和土样在冻结过程中会发生冻胀现象，土样结构被破坏，孔隙增大，土样持水性能下降关键词：土水特征曲线；冻结特征曲线；非饱和土；核磁共振技术中图分类号:TU443文献标识码：A文章编号:1672^2132(2020)06-0967-07Soil-water Characteristic Curve and Freezing Characteristic Curve ofLime Improved SoilWANG Yejiao',WANG Youwei1,JIN Fengyu1.MA Tiantian2(1.Department of Civil Engineering,Shanghai University,Shanghai200444,China；2.State Key Laboratory of Geomechanics and Geotech n ical En g ineeri n g,Wuhan430071,China；3.Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan430071,China)Abstract：The soil-water characteristic curve(SWCC)indicates the water retention properties of unsaturated soil,which is strongly related to soil hydro-mechanical behavior.The freezing characteristic curve of the soil represents the relationship between the potential energy of the liquid water in the soil and the water content.It can also represent the water retention behavior of unsaturated soil.In this study,loess was selected as the research object.The freezing characteristic curves of untreated loess and lime-treated soil were obtained from a cryogenic thermostat cold bath and nuclear magnetic reso-nance(NMR)system,and then the soil-water characteristic curve at0°C was deduced by applying the freezing temperature reduction method.In addition,the measured soil-water characteristic curve was obtained by using the filter paper method at around0°C.The two results were compared and analyzed, and the influence of the vacuum saturation process on the soil-water characteristic curve of the soil *收稿日期：2020-05-05；修回日期：2020-09-11基金项目：国家自然科学基金项目(41702306)资助作者简介：王叶娇(1988-),女，讲师，博士。

土壤水分特征曲线VG模型参数求解对比分析

土壤水分特征曲线VG模型参数求解对比分析新疆农业大学2011,34(5):437~441 JournalofXinjiangAgriculturalUniversity文章编号:1007—8614(2011)05—0437—05土壤水分特征曲线VG模型参数求解对比分析刘洪波.,张江辉,虎胆?吐马尔白,白云岗(1.新疆农业大学水利与土木工程学院,乌鲁木齐830052;2.新疆水利水电科学研究院,乌鲁木齐830049)摘要:采用负压汁对砂壤土试样进行了土壤水吸力和对应含水量的测量,并分别运用RETC软件和Matlab软件对不同水分处理土壤水分特征曲线VG模型进行了拟合计算,然后将拟合值与实测数据进行对比分析.结果表明.Matlab和RETC软件均可用于土壤水分特征曲线VG模型的参数求解,Matlab 软件比RETC软件拟合的误差小,拟合效果明显优于RETC软件,RETC软件对极端干旱区砂石占绝对比重的砂壤土拟合效果不佳.关键词:RETC;Matlab;Van—Genuchten模型;土壤水分特征曲线中图分类号:$274.1文献标识码:A ContrastAnalysisonSoilWaterCharacteristicCurveofVGModelParametersLIUHong—bo,ZHANGJiang—hui,Hudan.Tumaerbai,BAIYun—gang.(1.CollegeofWaterConservancyandCivilEngineering,XinjiangAgriculturalUniversity, Uru—mqi830052,China;2.XinjiangResearchInstituteofWaterResourcesandHydropower,Uru mqi830049,China)Abstract:Water—absorbingpowerandcorrespondingwatercontentofsandyloamsamplesweremeasured withnegativepresureandVGmode1ofsoi1watercharacteristiccurvewithdifferentwaterwe reaccordably calculatedwithRETCsoftwareandMatlabsoftwarerespectively,thenthecontrastanalysis wasconductedonfittingvalueandmeasureddata.TheresultshowedthatbothMatlabandRETCsoftwaresca nbeusedtOsolvetheparametersofVGmodelofsoi1watercharacteristiccurve,Matlabhaslessfittinge rrorsthanRETCsoftware,itsfittingeffectswerebetterthanthatofRETCsoftware.RETCsoftwareperf ormedits poorfittingeffectonabsoluteproportionofsandyloamintheextremelyaridregion. Keywords:RETC;Matlab;V an—Genuchtenmodel;soilwatercharacteristiccurve士壤水分特征曲线表示土壤水在非饱和状态下能态与数量问的关系,它是分析土壤水运动的最基本的资料之一,同时也是获取其他土壤水分常数和土壤水动力参数的基础.用负压式张力计法测定土壤水分特征曲线虽然范围有一定的限度,但是它结构简单,使用方便,而且能直接在田间测量,并且能用来指示灌溉,所以应用比较广泛【卜.目前,尚不能根据土壤的基本性质从理论上分析得出土壤水的基质势与含水率的关系,因此主要采用实测结果拟收稿日期:基金项目:通讯作者:合经验模型的方法测定水分特征曲线,常用的经验模有Broods—Corey模型,Gardner模型,V anGenu—chten模型(简称VG模型)和Gardner—Russo模型.目前,对Broods—Corey模型和Gardner—Russo模型国内仅做了少量研究l4-7],而国内外使用最为普遍的描述土壤水分特征曲线的是VG模型_1引,通过Matlab和RETC软件推导出实验土壤的土壤水分曲线,并认为RETC软件较Matlab软件拟合的误差小,拟合效果优于Matlab软件.李春友等口1532010—05—21国家科技支撑计划项目(2011BAD29B05);新疆维吾尔自治区科技攻关项目(200931105);水利部公益性行业科研专项(201001066)张江辉,E—mail:**************438新疆农业大学通过优化方法,阻尼最小二乘法以及遗传算法等不同方法推求了VG方程的参数,并且大部分的研究土壤质地为粘土,砂土或壤土等,而对于极端干旱区的砂壤土现有的研究甚少,本研究尝试对该地区使用RETC和Matlab软件提供的有关函数完成VG模型中4个参数的求解.1材料与方法1.1试验条件试验地点位于新疆吐鲁番地区鄯善县新疆葡萄瓜果开发研究中心试验基地(北纬42.91.,东经9O.30.);海拔419m.年降雨量25.3mm,年蒸发量2751mm,≥10℃积温为4522.6～5548.9℃,全年日照时数2900～3100h,平均日较差为14.3～15.9.C,最大可达17.0～26.6℃,无霜期192～224d.土壤质地主要为砾石沙壤土.葡萄品种为无核白,1981年定植,树龄28a,大沟定植,东西走向,沟长54m,沟宽1.0～1.2rn,沟深0.5m左右;株距约1.2～1.5m,行距3.5In;栽培方式为小棚架栽培,棚架前端高1.5m,后端高0.8ITI.1.2试验设计试验采用地面滴灌灌溉方式,设高水X(14775ITI./hm),中水X2(7950m./hm)和低水X.(5850m./hm)3个不同的水分处理,每个处理设2个重复,每个试验处理小区面积0.028hm.1.3试验内容与方法1.3.1土壤水势土壤水势利用DLS一1I负压计测定20,3O,50cm土层负压.1.3.2土壤含水率土壤含水率采用TRIM—IPH中子仪测定,在2010年7月2O日至7月26日8:O0观测不同处理0～2O,20～4O,40～60,60～80,8O～100cm深度上的田间土壤含水率.2结果与分析2.1VG模型VG模型由美国学者V anGenuchten于1980年提出,其表达式为:+式中:为体积含水率(cm./cm.);0,为残留含水率(cm./cm.);0为饱和含水率(cm./cm.);h为负压(cmH.O);a,,为经验拟合参数(或曲线性状参数);m一1—1/n.2.2实验数据对试验地随机定点,用环刀对3个不同取样点的0～20cm和20~40cm的土壤进行取样,进行容重的测定,结果表明0～20cm的土壤容重是1.40g/cm.,而20～40cm的土壤容重是1.15g/cm.(表1).其土壤水吸力与土壤含水量实测值具体结果见表2.2.3RETC和Matlab软件拟合土壤水分特征曲线RETC软件由USSL(美国盐改中心)开发,可用来分析非饱和土壤水分和水力传导特性.它可以很方便的实现土壤转换函数功能,即根据土壤的颗粒级配中砂粒,粉粒,粘粒的百分含量以及土壤容重等土壤物理性质数据,可直接输出V an—Genuchten 模型中的4个参数.由于饱和含水率0已由实验得到,故为已知值.将表1中土壤颗粒级配参数输入到RETC软件中,拟合得到其余+3参数值在0～20cm土层深度时0,一0.0441,0/一0.0376和视一1.6592,在20~40cm土层深度时0,-----0.0472,口一0.0395及一1.5643,并将通过实验已知的0～20cm和20～40cm饱和含水率0===24.5和0一19.9分别代人VG模型公式(1)中,得RETC拟合公式,(2)式为O～20cm,(3)式为20~40cm:=:=0.0441+(2)_--0.0472q-㈦对VG模型中的参数求解只需调用Matlabl1I¨中非线性曲线拟合函数lsqcurvefit求解非线性最小二乘问题,给出参数值区间,并给出初始值,即.=Eo1.100.O04];初始迭代值,由于m一1—1/>0,所以要求>1表1试验土壤颗粒级配Table1Theparticlesizedistributionoftestsoil0～2O20～4015.0112.161.401.15第5期刘洪波,等:土壤水分特征曲线VG模型参数求解对比分析439 z一Fo100.004];待定参数的下界.一F55111;待定参数的上界函数根据最小二乘原理进行自动迭代求解.然后利用实测数据就可确定VG模型中的0…0a和4个参数.通过编程得到拟合参数在0～20cm土层深度时0一O.2438,0,一O.0228,a—O.0251和,2—1.2583,在20~40cm土层深度时0一0.1993,0,一O.0118,口:==0.2219及一1.1751,并将通过实验已知的O～20cm和2O～40cm饱和含水率一24.5和0一19.9分别代人VG模型公式(1)中,得到Matlab拟合公式,(4)式为O～20cm,(5)式为2O～40cm:_0.0228+(4)O_O.0118+(5)将RETC软件和Matlab软件拟合的曲线与实测数据绘制在同一坐标系中(图1,图2).两种求参方法所得到的曲线存在明显差异(图1,图2),在O～2Ocm深度上,Matlab拟合值与实测值较接近,其重合程度要明显优于RETC拟合曲线,在2O～4Ocm深度上,Matlab在x和x水分处理上拟合优于RETC,但x.处理上RETC拟合值与实测值更为接近.对RETC和Matlab软件拟合的曲线进行残差分析(-h3).通过残差分析,可明显看出Matlab软件拟合效果优于RETC软件.O实测值*RETc拟合值"-~-Matlab拟合值一一皿旺I1抽磷_H一一噩I1*抽磷土壤水吸力(em)土壤水吸力(em)土壤水吸力(em)x.处理x处理x处理图1O～2ocm深度不同水分处理拟合土壤水分特征曲线比较Fig.1Comparisionofthefittingsoilwatercharacteristiccurvein0—20cmdepthwaterdifferentwatertreatments440新疆农业大学2011钲一一皿删抽磷0实测值*RETc拟合值-~-Matlab拟合值2蔓tt一一皿硎*缸磷土壤水吸力(cm)土壤水吸力(cm)x,处理x处理图220~40cm深度不同水分处理拟合土壤水分特征曲线比较土壤水吸力(cm)X处理Fig.2Comparisonofthefittingsoilwatercharacteristiccurvein2O一40cmdepthwithdifferentwatertreatments表3同软件拟合值残差分析Table3Analysisontheresidualerrorfittedwithdifferentsoftware第5期刘洪波,等:土壤水分特征曲线VG模型参数求解对比分析4413小结运用RETC软件和Matlab软件对土壤水分特征曲线VG模型中4个参数进行了拟合,表明RETC和Matlab软件进行土壤水分特征曲线VG模型的参数求解是可行的.从两种求参方法看,RETC软件操作步骤简单,计算精度高,无需编程;Matlab软件数值运算功能强大,对用户的编程能力有一定的要求;从拟合结果看,Matlab软件拟合结果明显优于RETC软件,这与王薇_l..和范严伟_】的研究结果存在差异,主要原因是他们所试验土壤质地为黏壤土和粉沙壤土,在RETC软件中可以得到更精确的参数,从而得到与实测值误差更小的拟合值,而本研究试验土壤虽为砂壤土,但砾石占有一定比重,使拟合参数本身存在一定偏差,进而导致拟合曲线与实测值差异较大.参考文献:[1]李玉琪.负压计测定土壤水分的应用分析[J].中国农村水利水电,1999(3):18—19.[2]刘思春,王国栋,朱建楚,等.负压式土壤张力计测定法改进及应用[J].西北农业,2002,11(2):29—33.E3]王凤新,康跃虎.用负压计拟定滴灌马铃薯灌溉计划的方法研究I-J].干旱地区农业研究.2005,23(3):58—64. 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