Journal Papers on Unsaturated Soils (Till 2002)

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不同钝化处理与叶面阻控剂对Cd污染稻田的修复效果

湖北农业科学2023年Cd的影响不显著，但能有效抑制糙米对Cd的富集。

由于不同地区的土质与土壤环境存在较大差异，因此需要选择最佳处理方式，在不同地区进行相应的大田试验，在松滋市选择3750mL/hm2叶面阻控剂+ 1200kg/hm2土壤调理剂+1200kg/hm2重金属钝化剂处理效果最好，土壤有效Cd与糙米中Cd含量分别下降了33.33%与44.95%。

4小结1）不同处理方式对土壤pH的影响有所差异，其中2400kg/hm2土壤调理剂、2400kg/hm2重金属钝化剂、3750mL/hm2叶面阻控剂+2400kg/hm2土壤调理剂、3750mL/hm2叶面阻控剂+2400kg/hm2重金属钝化剂、1200kg/hm2重金属钝化剂+1200kg/hm2土壤调理剂、3750mL/hm2叶面阻控剂+1200kg/hm2土壤调理剂+1200kg/hm2重金属钝化剂处理土壤pH 较对照显著增加，分别增加了5.07%、4.42%、6.06%、3.76%、5.73%、5.24%，而3750mL/hm2叶面阻控剂处理pH与对照之间无显著差异。

表明土壤调理剂、钝化剂能够适当调节土壤pH。

2）不同处理对土壤pH提升的幅度不同，对应的土壤中有效Cd含量的下降幅度也有较大变化。

除3750mL/hm2叶面阻控剂处理外，其他处理较对照有效Cd含量均显著降低，表明叶面阻控剂不能有效降低土壤有效Cd含量。

1200kg/hm2重金属钝化剂+1200kg/hm2土壤调理剂、3750mL/hm2叶面阻控剂+1200kg/hm2土壤调理剂+1200kg/hm2重金属钝化剂处理有效Cd含量下降幅度较大，分别降低了29.76%、33.33%。

3）不同处理糙米中Cd含量均较对照下降，且糙米中Cd含量均在安全限值内。

其中3750mL/hm2叶面阻控剂+1200kg/hm2土壤调理剂+1200kg/hm2重金属钝化剂处理效果最好，糙米中Cd含量下降了44.95%。

水泥固化软土抗拉特性研究

第53卷第7期2022年7月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.53No.7Jul.2022水泥固化软土抗拉特性研究李斯臣1,2，杨俊杰1,2，武亚磊1,2，王曼1,2(1.中国海洋大学海洋环境与生态教育部重点实验室，山东青岛，266100；2.中国海洋大学环境科学与工程学院，山东青岛，266100)摘要：为探究固化土的拉伸破坏问题，利用研制的单轴拉伸试验仪研究水泥固化不同软土的抗拉特性；基于抗拉强度随灰水比(水泥与水的质量之比)和龄期的变化规律，建立双曲线形式的抗拉强度−龄期关系式。

研究结果表明：抗拉强度、拉伸模量随水泥土的灰水比和龄期增加而增大；表征材料韧性的断裂能随龄期增加而增大，胶州湾黏土固化土断裂能随灰水比先增大后减小，而东营港粉土固化土断裂能随灰水比持续增大；水泥土的抗拉强度与无侧限抗压强度呈线性关系，其拉压比可取0.15；与其他学者的试验数据对比，所提公式的抗拉强度计算值与试验结果较吻合，能在一定程度上反映水泥固化软土抗拉强度随龄期的变化规律。

关键词：水泥固化软土；抗拉特性；灰水比；龄期；抗拉强度预测中图分类号：TU411文献标志码：A文章编号：1672-7207（2022）07-2619-14Research on tensile characteristics of cement-treated soft soilLI Sichen 1,2,YANG Junjie 1,2,WU Yalei 1,2,WANG Man 1,2(1.Key Laboratory of Marine Environment and Ecology,Ministry of Education,Ocean University of China,Qingdao 266100,China;2.College of Environmental Science and Engineering,Ocean University of China,Qingdao 266100,China)Abstract:In order to explore the tensile failure properties of solidified soil,the developed uniaxial tensile tester was conducted to investigate the tensile characteristics of cement-treated soft soil.Based on the law whereby the tensile strength of cement-treated soil increases with the curing time and cement-water ratio(mass ratio of cement to water),a hyperbolic formula was established,with which the relationship between the tensile strength of cement-treated soft soil and curing time was obtained.The results show that the tensile strength,tensile modulus increase with the cement-water ratio and curing time and the fracture energy characterizing the toughness of materials increases with the curing time.The fracture energy of cement-treated Jiaozhou Bay clay increases at first收稿日期：2021−08−01；修回日期：2021−09−21基金项目(Foundation item)：国家自然科学基金资助项目(51779235，52078474)(Projects(51779235,52078474)supported by theNational Natural Science Foundation of China)通信作者：武亚磊，博士(后)，从事地基处理及固废资源化、环境岩土工程等研究；E-mail ：***************DOI:10.11817/j.issn.1672-7207.2022.07.021引用格式：李斯臣,杨俊杰,武亚磊,等.水泥固化软土抗拉特性研究[J].中南大学学报(自然科学版),2022,53(7):2619−2632.Citation:LI Sichen,YANG Junjie,WU Yalei,et al.Research on tensile characteristics of cement-treated soft soil[J].Journal of Central South University(Science and Technology),2022,53(7):2619−2632.第53卷中南大学学报(自然科学版)and then decreases with the cement-water ratio,while the fracture energy of cement-treated Dongying Port silt continues to increase with the cement-water ratio.The tensile strength of cement-treated soil has a linear relationship with the unconfined compressive strength,and the tension-compression ratio can be adopted as0.15. The calculated values of tensile strength obtained by the proposed formula are consistent with the experimental results,which can basically reflect the change law of the tensile strength of cement-treated soft soil.Key words:cement-treated soft soil;tensile characteristics;cement-water ratio;curing time;tensile strength forecast拉伸破坏是土体破坏的基本形式之一[1−2]。

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]。

土木工程重要国际学术会议

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国际水科学与工程会议
International Conference on Hydroscience and Engineering
IAHR（International Association for
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国际水利学大会
Hydro-Environment Engineering）
Congress
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国际计算科学大会
International Conference on Computational Science（ICCS）
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国际nference on the Mechanics of Jointed and Faulted
Rock （MJFR）
地学计算年会
Geocomputation
地震工程国际会议东亚及太平洋地区结构工程与
营造学术会议
钝体空气动力学会议
风险分析和减灾中计算机模拟国际会议
International Conference on Earthquake Engineering
East Asian-Pacific Conference on Structural Engineering &
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10 11 12 13 14 15
16 17 18 19 20 21 22
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会议名称
中文名称
FRP加固混凝土结构国际会议
Geo+地点（名称不定，以举办城市命名）
英文名称 International Symposium on FRP
Reinforcement for Concrete Structure

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 .。

journal of soils and sediments评价 -回复

journal of soils and sediments评价-回复Journal of Soils and Sediments评价Journal of Soils and Sediments (JSS) 是一本国际性的科学期刊，于2001年创刊，由国际土壤学会（International Union of Soil Sciences）主办。

该期刊旨在促进土壤和沉积物领域的研究和交流，发表高质量的原创研究论文、评论和研究动态。

JSS 的主要目标是提供土壤和沉积物科学领域的高质量科学研究成果和知识，促进该领域的学术交流和合作。

该期刊涵盖了多个研究领域，包括土壤科学、岩石学、水资源管理、环境地球化学和污染物迁移等。

其广泛的研究领域使得该期刊成为了该领域内的一个重要的学术出版物。

JSS 的编辑团队由国际知名的领域专家组成，确保了出版的论文质量。

投稿的论文会经过严格的同行评审过程，以确保其学术水准和科学价值。

这一流程确保了发表在JSS 上的文章具有较高的可靠性和可重复性。

该期刊对于研究人员来说，是一个重要的学术交流平台。

在JSS 上发表论文不仅可以提高作者的学术声誉和地位，还可以增加其研究成果的影响力。

对于读者来说，JSS 提供了最新的科学研究成果和知识，有助于他们了解该领域的最新发展动态。

在评价JSS 这一期刊时，可以从以下几个方面入手：1. 出版质量：JSS 的编辑团队由国际知名的领域专家组成，确保了论文的出版质量。

该期刊的同行评审过程严格，确保了投稿论文的学术水准和科学价值。

2. 学术影响力：JSS 是该领域内的一个重要学术期刊，发表在该期刊上的论文会为作者带来较高的学术声誉和地位。

此外，JSS 的文章能够广泛传播，提高作者研究成果的影响力。

3. 研究领域覆盖面：JSS 涵盖了广泛的研究领域，包括土壤科学、岩石学、水资源管理、环境地球化学和污染物迁移等。

这使得JSS 成为了该领域内的一个综合性学术期刊，吸引了众多研究人员和读者的关注。

非饱和黄土基质吸力的滤纸法测试

非饱和黄土基质吸力的滤纸法测试唐东旗，彭建兵，孙伟青【摘要】摘要: 黄土属于非饱和土，具有明显的大孔隙、垂直节理发育、湿陷性等特征，使得黄土地区工程地质灾害问题频发。

由于黄土具有水敏性，因此水的因素成为诱发地质灾害的主要因素。

基质吸力的变化是土体边坡稳定的重要因素。

利用滤纸法对非饱和黄土的基质吸力进行试验研究，得出随着含水率的增加基质吸力逐渐减小；在土体含水率较小时基质吸力的变化比较敏感，含水率越高，其变化越小；在含水率达到饱和时基质吸力消失为零；并且随含水率的增加土体的抗剪强度逐渐减小。

研究认为，滤纸法对操作过程中空气条件要求相对严格，是一种能够快速、简便测试非饱和土体基质吸力的方法。

【期刊名称】煤田地质与勘探【年(卷),期】2012(000)005【总页数】5【关键词】关键词：滤纸法；非饱和黄土；基质吸力；土水特征曲线；抗剪强度中国黄土广泛分布在西北、华北与东北地区，尤其集中分布在被称为中央黄土高原的陕西、甘肃、山西以及宁夏等省区，黄土面积达到了63万km2，占陆地面积的6.63%，占世界黄土覆盖面积的4.9%。

多年来黄土地区水土流失严重，地质灾害频发，严重制约了经济的发展。

黄土属于非饱和土，具有大孔隙、垂直节理发育和湿陷性等特征，使得黄土地区工程地质灾害问题严重。

开展黄土地区地质灾害的成因机理研究是预防黄土地质灾害的基础，而非饱和土的土水特征曲线是解释非饱和土工程现象的一项本构关系，是一切非饱和土研究的纽带[1]。

对非饱和土基质吸力的测试方法很多，主要有张力计法、滤纸法、渗析法、压力板仪法、离心机法和三轴仪法，这些方法各具优点。

本文采用滤纸法对非饱和土的基质吸力进行测量。

现有的研究表明，滤纸法是一种即能测土体总吸力又能测基质吸力的间接测试方法，该方法具有价格低廉、操作简单、量程大和精度高等优点。

当前，国外有关滤纸法研究的成果较多采用whatman’s No.42和Schleicher＆Schuell No.589-WH两种型号的滤纸，但在国内滤纸法的研究成果屈指可数[2-5]，且主要涉及国产“双圈”牌滤纸的吸力率定试验。

非饱和土稳态渗流试验装置的研制与应用

第２７卷第１１期岩土工程学报Ｖｏｌ．２７Ｎｏ．１１　２００５年１１月Ｃｈｉｎｅｓｅ　Ｊｏｕｒｎａｌ　ｏｆ　Ｇｅｏｔｅｃｈｎｉｃａｌ　ＥｎｇｉｎｅｅｒｉｎｇＮｏｖ．，２００５　非饱和土稳态渗流试验装置的研制与应用邵龙潭１，梁爱民１，王助贫２，孙健３　（１．大连理工大学　工程力学系，辽宁　大连　１１６０２４；２．中国农业大学　水利与土木工程学业院，北京　１０００８３；３．上海岩土工程勘察设计研究院有限公司，上海　２０００３１）　摘要：非饱和土稳态渗流试验装置是用于实验室量测非饱和土土水特性和导水系数参数的装置。

该装置以在稳态渗流状态下测定土壤对水分的吸持能力为基础，用来量测非饱和土在脱水、吸湿两种循环状态下的土壤水分特征曲线；同时可以量测上述两种过程中各级基质吸力所对应的非饱和土的导水系数。

在相同的条件下，所测试结果与美国Soilmoisture公司生产的1250型压力板仪所得的试验结果具有很好的一致性和稳定性，可以在实验室中推广应用。

　关键词：非饱和土；土壤水分特征曲线；导水系数；稳态渗流；基质吸力　中图分类号：TU 411.93 文献标识码：A 文章编号：1000–4548(2005)11–1338–03作者简介：邵龙潭(1963–)，男，教授、博士生导师，主要从事土力学和岩石力学试验测试技术和仪器开发研制、非饱和土和孔隙介质的强度和本构关系、土壤渗流理论与计算以及水土保持与节水灌溉等应用项目的研究。

　Manufacture and application of steady seepage equipment for unsaturated soilSHAO Long-tan1, LIANG Ai-min1, WANG Zhu-pin1, SUN Jian3(1. Department of Engineering Mechanics, Dalian University of Technology, Dalian 116024, China; 2. College of Water Conservancy &Civil Engineering, China Agricultural University, Beijing 100083, China; 3. Shanghai Geotechnical Investigation & Design Institute Co.,Ltd., Shanghai 200031, China)Abstract: The apparatus was applied to determine the parameter of unsaturated soils in the laboratory, based on thecharacteristics of soil that the ability of adsorption was invariable in the steady seepage state, which could test the water-soilcharacteristic curve in and the conductivity of unsaturated soils the process of desorption and sorption. Under the sameconditions, the water-soil characteristic curve attained from the steady seepage test accorded with the result obtained from the1250 volumetric pressure plate extractor made in Soilmoisture Equipment Corp of USA. The experimental results indicate thatthe apparatus is stable, and can be used in the laboratory to study soils.Key words: unsaturated soils; soil-water characteristic curve; permeability; steady seepage; soil suction０前言　土壤水分特征曲线反映了土壤水的能量和数量之间的关系，是研究土壤持水能力和水分运动所必须的。

土壤微塑料影响植物生长的因素与机制研究进展

塑料作为一种被广泛应用的有机合成聚合物材料，在为我们生活提供便利的同时，也带来了后续的环境问题。

据估算，到2050年，将有大约12000万t 塑料垃圾被埋入垃圾填埋场或自然环境中[1]，塑料垃圾进入到环境后会逐渐破碎变成微塑料（<5mm ），导致其在土壤和水体中的丰度逐年递增[2-3]。

2015年的第二届联合国环境大会已将微塑料污染列为环境与生态领域的第二大科学问题[3]。

目前，人们对水体中微塑料的认识已较为系统[4-6]，土壤微塑料逐步成为新的研究热点[7-8]。

2012年Rillig [9]首次提出微塑料会影响土壤理化性质，这引起了人们对土壤微塑料的关注，后续研究表明微塑料可被植物吸收并积累[10-11]，最终通过食物链进入人体。

厘清微塑料对植物生长的影响及其机制，有助于系统掌握其在土壤-植物体陈欣，郭薇，李济之，等.土壤微塑料影响植物生长的因素与机制研究进展[J].农业环境科学学报,2024,43（3）：488-495.CHEN X,GUO W,LI J Z,et al.Research progress on the influencing factors and mechanisms of soil microplastics on plant growth[J].Journal of Agro-Environment Science ,2024,43（3）：488-495.土壤微塑料影响植物生长的因素与机制研究进展陈欣1，郭薇1，2，李济之1，2，迟光宇1*（1.中国科学院沈阳应用生态研究所，污染生态与环境工程重点实验室，沈阳110016；2.中国科学院大学，北京100049）Research progress on the influencing factors and mechanisms of soil microplastics on plant growthCHEN Xin 1,GUO Wei 1,2,LI Jizhi 1,2,CHI Guangyu 1*（1.Key Laboratory of Pollution Ecology and Environmental Engineering,Institute of Applied Ecology,Chinese Academy of Sciences,Shenyang 110016,China ；2.University of Chinese Academy of Sciences,Beijing 100049,China ）Abstract ：Microplastics in soil can affect plant growth in a variety of ways,accumulate in plants,and eventually enter the human body via the food chain.Clarifying the mechanisms and main factors whereby microplastics influence plant growth can contribute to a systematic understanding of their environmental behavior in soil-plant systems.Both the occurrence state and physicochemical characteristics of microplastics can influence their effects on plants.In this paper,from the perspectives of particle size,shape,concentration,and type,plastic additives,and aging degree of microplastics,we review the main factors and mechanisms underlying the effects of soil microplastics on plant growth.The key direction of future research is proposed,which will provide a reference for further clarifying the impact of microplastics on soil ecosystems.Keywords ：soil;microplastics;plant;influencing factor;mechanism of action收稿日期：2023-04-13录用日期：2023-06-19作者简介：陈欣（1968—），男，辽宁沈阳人，博士，研究员，研究方向为农业生态。

土壤修复的英文顶刊

土壤修复的英文顶刊There are several top journals in the field of soil remediation. Some of the prominent ones include:1. Environmental Science & Technology (ES&T): This journal covers a wide range of environmental science topics, including soil remediation. It publishes research articles, reviews, and perspectives on various aspects of soil remediation techniques, technologies, and case studies.2. Journal of Environmental Quality (JEQ): JEQ focuses on the quality of soil, water, and air resources. It publishes research articles, technical notes, and reviews related to soil remediation practices, including soil contamination assessment, remediation strategies, and monitoring techniques.3. Chemosphere: Chemosphere is an interdisciplinary journal that covers a broad range of environmental science topics, including soil remediation. It publishes originalresearch articles, reviews, and short communications on the assessment and remediation of contaminated soils, as well as the fate and transport of contaminants in soil environments.4. Environmental Pollution: This journal publishes research articles, reviews, and short communications on various aspects of environmental pollution, including soil contamination and remediation. It covers topics such assoil pollution assessment, risk assessment, and innovative remediation technologies.5. Soil Science Society of America Journal (SSSAJ): SSSAJ is a leading journal in the field of soil science. It publishes research articles, technical notes, and reviews on various aspects of soil remediation, including soil physics, chemistry, and biology, as well as the application of remediation techniques to restore soil health.These journals provide comprehensive coverage of soil remediation research and offer valuable insights into the latest advancements in the field.。

大型尾矿库下游高等级排土场的降雨入渗特性

大型尾矿库下游高等级排土场的降雨入渗特性朱君星;李跃;李从德【摘要】尾矿库和排土场都是高势能的泥石流重大危险源，二者的降雨入渗特性均较复杂。

而当高等级排土场位于大型尾矿库的下游时，其复杂性更不言而喻。

通过对太和铁矿的工程实例分析，计算得到尾矿库在千年一遇洪水条件下的浸润线分布，将其导入到排土场中作为初始条件，计算得到初始浸润线；再据此分析整个研究区域的降雨条件下入渗特性。

研究结果表明，尾矿库内的浸润线分布对下游排土场的影响很大，入渗作用改变了排土场边坡内的地下水渗流场，而地下水的升高则是一个缓慢的过程。

%Both of tailing pond and waster dump is high -potential fatal danger fountainhead for debris flow , and the infiltration characteristic are all complex of them .Especially , when a high-class dump is downstream of a large-scale tailing pond , the degree of complexity is more self -evident .Based on the engineering instance a-nalysis of Taihe Iron Mining , phreatic line under the case of the millennium of the tailing pond was obtained , which is introduced into the waster dump model as an initial condition to calculate the initial phreatic line .On the basis, the infiltration characteristic in the entire area under rainfall was analyzed .The study results showed that the phreatic line distribution in the tailing pond has great influence on the waster dump at downstream , the groundwater seepage field in the dump was changed by the infiltration , and the rise of groundwater is a slow .【期刊名称】《安徽理工大学学报（自然科学版）》【年(卷),期】2015(000)001【总页数】5页(P45-49)【关键词】降雨入渗;非饱和渗流;尾矿库;排土场;基质吸力【作者】朱君星;李跃;李从德【作者单位】中钢集团马鞍山矿山研究院有限公司，安徽马鞍山 243000; 金属矿山安全与健康国家重点实验室，安徽马鞍山 243000;中钢集团马鞍山矿山研究院有限公司，安徽马鞍山 243000; 金属矿山安全与健康国家重点实验室，安徽马鞍山 243000;重钢西昌矿业有限公司，四川西昌 615041【正文语种】中文【中图分类】TD216(1. 中钢集团马鞍山矿山研究院有限公司，安徽马鞍山243000 2. 金属矿山安全与健康国家重点实验室，安徽马鞍山243000；3. 重钢西昌矿业有限公司，四川西昌615041)(1. Maanshan Institute of Mining Research, Sinosteel Group Co. Ltd., Maans han Anhui 243000, China; 2. State Key Laboratory of Safety and Health for Metal Mine, Maanshan Anhui 243000, China；3. Xichang Mining Co., Ltd., Chongqing Iron and Steel Group, Xichan Sichu an 615041, China)Key words:Rainfall infiltration; unsaturated seepage; tailing pond; waster d ump; matric suction尾矿库和排土场作为矿山重要的两大附属设施，安全性直接影响到矿山的经济效益。

Unsaturated Soil Mechanics in Engineering Practice

Unsaturated Soil Mechanics in Engineering PracticeDelwyn G.Fredlund1Abstract:Unsaturated soil mechanics has rapidly become a part of geotechnical engineering practice as a result of solutions that have emerged to a number of key problems͑or challenges͒.The solutions have emerged from numerous research studies focusing on issues that have a hindrance to the usage of unsaturated soil mechanics.The primary challenges to the implementation of unsaturated soil mechanics can be stated as follows:͑1͒The need to understand the fundamental,theoretical behavior of an unsaturated soil;͑2͒the formulation of suitable constitutive equations and the testing for uniqueness of proposed constitutive relationships;͑3͒the ability to formulate and solve one or more nonlinear partial differential equations using numerical methods;͑4͒the determination of indirect techniques for the estimation of unsaturated soil property functions,and͑5͒in situ and laboratory devices for the measurement of a wide range of soil suctions.This paper explains the nature of each of the previous challenges and describes the solutions that have emerged from research puter technology has played a major role in achieving practical geotechnical engineering puter technology has played an important role with regard to the estimation of unsaturated soil property functions and the solution of nonlinear partial differential equations.Breakthroughs in the in situ and laboratory measurement of soil suction are allowing unsaturated soil theories and formulations to be veriﬁed through use of the“observational method.”DOI:10.1061/͑ASCE͒1090-0241͑2006͒132:3͑286͒CE Database subject headings:Unsaturated soils;Soil mechanics;Geotechnical engineering;Research.PreambleKarl Terzaghi is remembered most for providing the“effective stress”variable,͑␴−u w͒,that became the key to describing the mechanical behavior of saturated soils;where␴=total stress and u w=pore–water pressure.The effective stress variable became the unifying discovery that elevated geotechnical engineering to a science basis and context.As a graduate student I was asked to purchase and study the textbook,Theoretical Soil Mechanics,by Karl Terzaghi͑1943͒.I had already selected the subject of unsaturated soil behavior as myﬁeld of research and was surprised toﬁnd considerable infor-mation on this subject in this textbook.Two of the19chapters of the textbook contribute extensively toward understanding unsat-urated soil behavior;namely,Chapter14on“Capillary Forces,”and Chapter15,on“Mechanics of Drainage”͑with special atten-tion to drainage by desiccation͒.These chapters emphasize the importance of the unsaturated soil portion of the proﬁle and in particular provide an insight into the fundamental nature and importance of the air–water interface͑i.e.,contractile skin͒. Considerable attention was given to soils with negative pore–water pressures.Fig.1shows an earth dam illustrating how waterﬂowed above the phreatic line through the capillary zone ͑Terzaghi1943͒.The contributions of Karl Terzaghi toward unsaturated soil behavior are truly commendable and still worthy of study.Subsequent reference to the textbook Theoretical Soil Mechan-ics during my career,has caused me to ask the question,“Why did unsaturated soil mechanics not emerge simultaneously with saturated soil mechanics?”Pondering this question has led me to realize that there were several theoretical and practical challenges associated with unsaturated soil behavior that needed further re-search.Unsaturated soil mechanics would need to wait several decades before it would take on the character of a science that could be used in routine geotechnical engineering practice.I am not aware that Karl Terzaghi ever proposed a special description of the stress state in an unsaturated soil;however, his contemporary,Biot͑1941͒,was one of theﬁrst to suggest the use of two independent stress state variables when formulating the theory of consolidation for an unsaturated soil.This paper will review a series of key theoretical extensions that were required for a more thorough representation and formulation of unsaturated soil behavior.Research within the agriculture-related disciplines strongly inﬂuenced the physical and hydraulic model that Terzaghi developed for soil mechanics͑Baver1940͒.With time,further signiﬁcant contributions have come from the agriculture-related disciplines͑i.e.,soil science,soil physics,and agronomy͒to geo-technical engineering.It can be said that geotechnical engineers tended to test soils by applying total stresses to soils through the use of oedometers and triaxial cells.On the other hand, agriculture-related counterparts tended to apply stresses to the water phase͑i.e.,tensions͒through use of pressure plate cells. Eventually,geotechnical engineers would realize the wealth of information that had accumulated in the agriculture-related disciplines;information of value to geotechnical engineering. Careful consideration would need to be given to the test proce-dures and testing techniques when transferring the technology into geotechnical engineering.1Professor Emeritus,Dept.of Civil and Geological Engineering,Univ. of Saskatchewan,Saskatoon SK,Canada S7N5A9.Note.Discussion open until August1,2006.Separate discussions must be submitted for individual papers.To extend the closing date by one month,a written request must beﬁled with the ASCE Managing Editor.The manuscript for this paper was submitted for review and pos-sible publication on February16,2005;approved on May1,2005.This paper is part of the Journal of Geotechnical and Geoenvironmental Engineering,V ol.132,No.3,March1,2006.©ASCE,ISSN1090-0241/ 2006/3-286–321/$25.00.An attempt is made in this paper to give the theory of unsat-urated soil mechanics its rightful position.Terzaghi ͑1943͒stated that “the theories of soil mechanics provide us only with the working hypothesis,because our knowledge of the average physical soil properties of the subsoil and the orientation of the boundaries between the individual strata is always incomplete and often utterly inadequate.”Terzaghi ͑1943͒also emphasized the importance of clearly stating all assumptions upon which the theories are based and pointed out that almost every “alleged contradiction between theory and practice can be traced back to some misconception regarding the conditions for the validity of the theory.”And so his advice from the early days of soil mechan-ics is extremely relevant as the theories for unsaturated soil be-havior are brought to the “implementation”stage in geotechnical engineering.IntroductionFundamental principles pivotal to understanding the behavior of saturated soils emerged with the concept of effective stress in the 1930s ͑Terzaghi 1943͒.There appeared to be considerable interest in the behavior of unsaturated soil at the First International Conference on Soil Mechanics and Foundation Engineering in 1936,but the fundamental principles required for formulating unsaturated soil mechanics would take more than another 30years to be forthcoming.Eventually,a theoretically based set of stress state variables for an unsaturated soil would be proposed within the context of multiphase continuum mechanics ͑Fredlund and Morgenstern 1977͒.There have been a number of challenges ͑i.e.,problems or difﬁculties ͒that have slowed the development and implement-ation of unsaturated soil mechanics ͑Fredlund 2000͒.Each of these challenges has provided an opportunity to develop new and innovative solutions that allow unsaturated soil mechanics to become part of geotechnical engineering practice.It has been necessary for geotechnical engineers to adopt a new “mindset”toward soil property assessment for unsaturated soils ͑Fredlund et al.1996͒.The primary objective of this paper is to illustrate the progres-sion from the development of theories and formulations to practical engineering protocols for a variety of unsaturated soil mechanics problems ͑e.g.,seepage,shear strength,and volume change ͒.The use of “direct”and “indirect”means of characteriz-ing unsaturated soil property functions has been central to the emergence of unsaturated soil mechanics.The key challenges faced in the development of unsaturated soil mechanics are described and research ﬁndings are presented that have made it possible to implement unsaturated soil mechanics into geotech-nical engineering practice.A series of unsaturated soil mechanics problems are presented to illustrate the procedures and methodology required to obtain meaningful solutions to plete and detailed case histories will not be presented but sufﬁcient information is pro-vided to illustrate the types of engineering solutions that are feasible.Gradual Emergence of Unsaturated Soil Mechanics Experimental laboratory studies in the late 1950s ͑Bishop et al.1960͒showed that it was possible to independently measure ͑or control ͒the pore–water and pore–air pressures through the use of high air entry ceramic boratory studies were reported over the next decade that revealed fundamental differences be-tween the behavior of saturated and unsaturated soils.The studies also revealed that there were signiﬁcant challenges that needed to be addressed.The laboratory testing of unsaturated soils proved to be time consuming and demanding from a technique standpoint.The usual focus on soil property constants was diverted toward the study of nonlinear unsaturated soil property functions.The increased complexity of unsaturated soil behavior extended from the laboratory to theoretical formulations and solutions.Originally,there was a search for a single-valued effective stress equation for unsaturated soils but by the late 1960s,there was increasing awareness that the use of two independent stress state variables would provide an approach more consistent with the principles of continuum mechanics ͑Fredlund and Morgenstern 1977͒.The 1970s was a period when constitutive relations for the classic areas of soil mechanics were proposed and studied with respect to uniqueness ͑Fredlund and Rahardjo 1993͒.Initially,constitutive behavior focused primarily on the study of seepage,shear strength,and volume change problems.Gradually it became apparent that the behavior of unsaturated soils could be viewed as a natural extension of saturated soil behavior ͑Fredlund and Morgenstern 1976͒.Later,numerous studies attempted to combine volume change and shear strength in the form of elasto-plastic models that were an extension from the saturated soil range to unsaturated soil conditions ͑Alonso et al.1990;Wheeler and Sivakumar 1995;Blatz and Graham 2003͒.The study of con-taminant transport and thermal soil properties for unsaturated soils also took on the form of nonlinear soil property functions ͑Newman 1996;Lim et al.1998;Pentland et al.2001͒.The 1980s was a period when boundary-value problems were solved using numerical,ﬁnite element,and ﬁnite difference mod-eling methods.Digital computers were required and iterative,numerical solutions became the norm.The challenge was to ﬁnd techniques that would ensure convergence of highly nonlinear partial differential equations on a routine basis ͑Thieu et al.2001;Fig.1.An earth dam shown by Terzaghi ͑1943͒illustrating that water can ﬂow above the phreatic line through the capillary zone ͑reprinted with permission of ErLC Terzaghi ͒Fredlund et al.2002a,b,c͒.Saturated–unsaturated seepage model-ing became theﬁrst of the unsaturated soils problems to comeinto common engineering practice.Concern for stewardshiptoward the environment further promoted interest in seepage andgeoenvironmental,advection-dispersion modeling.The1990s and beyond have become a period where therehas been an emphasis on the implementation of unsaturated soilmechanics into routine geotechnical engineering practice.A seriesof international conferences have been dedicated to the exchangeof information on the engineering behavior of unsaturated soilsand it has become apparent that the time had come for increasedusage of unsaturated soil mechanics in engineering practice.Implementation can be deﬁned as“a unique and important stepthat brings theories and analytical solutions into engineeringpractice”͑Fredlund2000͒.There are several stages in the devel-opment of a science that must be brought together in an efﬁcientand appropriate manner in order for implementation to becomea reality.The primary stages suggested by Fredlund͑2000͒,areas follows:͑1͒State variable;͑2͒constitutive;͑3͒formulation;͑4͒solution;͑5͒design;͑6͒veriﬁcation and monitoring;and ͑7͒implementation.Research is required for all of the above-mentioned stages in order that practical,efﬁcient,cost-effective,and appropriate technologies emerge.Primary Challenges to the Implementationof Unsaturated Soil MechanicsThere are a number of primary challenges that needed to beaddressed before unsaturated soil mechanics could become a partof routine geotechnical engineering practice.Several of thechallenges are identiﬁed here.Each challenge has an associatedsolution that is further developed throughout the manuscript.Insome cases it has been necessary to adopt a new approach tosolving problems involving unsaturated soils.In this paper,anattempt is made to describe the techniques and procedures thathave been used to overcome the obstacles to implementation;thuspreparing the way for more widespread application of unsaturatedsoil mechanics.Challenge1:The development of a theoretically sound basisfor describing the physical behavior of unsaturated soils,startingwith appropriate state variables.Solution1:The adoption of independent stress state variablesbased on multiphase continuum mechanics has formed the basisfor describing the stress state independent of soil properties.The stress state variables can then be used to develop suitableconstitutive models.Challenge2:Constitutive relations commonly accepted forsaturated soil behavior needed to be extended to also describeunsaturated soil behavior.Solution2:Gradually it became apparent that all constitutiverelations for saturated soil behavior could be extended to embraceunsaturated soil behavior and thereby form a smooth transitionbetween saturated and unsaturated soil conditions.In each case,research studies needed to be undertaken to verify the uniqueness of the extended constitutive relations.Challenge3:Nonlinearity associated with the partial differen-tial equations formulated for unsaturated soil behavior resulted in iterative procedures in order to arrive at a solution.The conver-gence of highly nonlinear partial differential equations proved to be a serious challenge.Solution3:Computer solutions for numerical models have em-braced automatic mesh generation,automatic mesh optimization,and automatic mesh reﬁnement͓known as adaptive grid reﬁne-ment͑AGR͔͒,and these techniques have proved to be of greatassistance in obtaining convergence when solving nonlinear par-tial differential equations.Solution procedures were forthcomingfrom the mathematics and computer science disciplines.Challenge4:Greatly increased costs and time were required for the testing of unsaturated soils.As well,laboratory equipmentfor measuring unsaturated soil properties has proven to be tech-nically demanding and quite complex to operate.Solution4:Indirect,estimation procedures for the character-ization of unsaturated soil property functions were related to thesoil–water characteristic curve͑SWCC͒and the saturated soilproperties.Several estimation procedures have emerged for eachof the unsaturated soil property functions.The computer has alsoplayed an important role in computing unsaturated soil propertyfunctions.Challenge5:Highly negative pore–water pressures͑i.e., matric suctions greater than100kPa͒,have proven to be difﬁcultto measure,particularly in theﬁeld.Solution5:New instrumentation such as the direct,high suc-tion tensiometer,and the indirect thermal conductivity suctionsensor,have provided new measurement techniques for thelaboratory and theﬁeld.Other measurement systems are alsoshowing promise.These devices allow suctions to be measuredover a considerable range of matric suctions.The null type,axis-translation technique remains a laboratory reference procedure forthe measurement of matric suction.Challenge6:New technologies such as those proposed for unsaturated soil mechanics are not always easy to incorporate intoengineering practice.The implementation of unsaturated soilmechanicsﬁndings into engineering practice has proven to be achallenge.Solution6:Educational materials and visualization systems have been assembled to assist in effective technology transfer ͑Fredlund and Fredlund2003͒.These are a part of teaching and demonstrating the concepts of unsaturated soil behavior;information that needs to be incorporated into the undergraduateand graduate curriculum at universities.Protocols for engineeringpractice are being developed for all application areas of geotech-nical engineering.Changes are necessary in geotechnical engineering practicein order for unsaturated soil mechanics to be implemented.Eachchallenge has been met with a deﬁnitive and practical solution.In the case of the determination of unsaturated soil propertyfunctions a signiﬁcant paradigm shift has been required͑Houston2002͒.The new approaches that have been developed appearto provide cost-effective procedures for the determination ofunsaturated soil property functions for all classes of problems ͑Fredlund2002͒.Laboratory and Field Visualizationof Varying Degrees of SaturationClimatic conditions around the world range from very humid to arid,and dry.Climatic classiﬁcation is based on the average net moistureﬂux at the ground surface͓i.e.,precipitation minus potential evaporation͑Thornthwaite1948͔͒.The ground surface climate is a prime factor controlling the depth to the groundwater table and therefore,the thickness of the unsaturated soil zone ͑Fig.2͒.The zone between the ground surface and the water table is generally referred to as the unsaturated soil zone.This is some-what of a misnomer since the capillary fringe is essentially saturated.A more correct term for the entire zone above the water table is the vadose zone ͑Bouwer 1978͒.The entire zone sub-jected to negative pore–water pressures is commonly referred to as the unsaturated zone in geotechnical engineering.The unsaturated zone becomes the transition between the water in the atmosphere and the groundwater ͑i.e.,positive pore–water pressure zone ͒.The pore–water pressures in the unsaturated soil zone can range from zero at the water table to a maximum tension of approximately 1,000,000kPa ͑i.e.,soil suction of 1,000,000kPa ͒under dry soil conditions ͑Croney et al.1958͒.The water degree of saturation of the soil can range from 100%to zero.The changes in soil suction result in distinct zones of saturation.The zones of saturation have been deﬁned in situ as well as in the laboratory ͓i.e.,through the soil–water characteristic curve ͑Fig.3͔͒.Table 1illustrates the terminologies commonly used to describe saturation conditions in situ and in the laboratory.Soils in situ start at saturation at the water table and tend to become unsaturated toward the ground surface.Soils near to the ground surface are often classiﬁed as “prob-lematic”soils.It is the changes in the negative pore–water pressures that can result in adverse changes in shear strength and volume mon problematic soils are:expansive orswelling soils,collapsible soils,and residual soils.Any of the above-mentioned soils,as well as other soil types,can also be compacted,once again giving rise to a material with negative pore–water pressures.Unsaturated Soil as a Four-Phase MixtureAn unsaturated soil is commonly referred to as a three-phase mixture ͑i.e.,solids,air,and water ͒but there is strong justiﬁcation for including a fourth independent phase called the contractile skin or the air–water interface.The contractile skin acts like a thin membrane interwoven throughout the voids of the soil,acting as a partition between the air and water phases.It is the interaction of the contractile skin with the soil structure that causes an unsatur-ated soil to change in volume and shear strength.The unsaturated soil properties change in response to the position of the contrac-tile skin ͑i.e.,water degree of saturation ͒.It is important to viewTable parison of Terminology Used to Describe In Situ and Laboratory Degrees of Saturation In situ zones of saturation Zones of saturation on the soil-watercharacteristic curveCapillary fringeBoundary effect Two phase ﬂuid ﬂowTransition Dry ͑vapor transport of water ͒ResidualFig.2.Illustration of the unsaturated soil zone ͑vadose zone ͒on a regional and localbasisFig. 3.Illustration of the in situ zones of desaturation deﬁned by a soil–water characteristic curvean unsaturated soil as a four-phase mixture for purposes of stress analysis,within the context of multiphase continuum mechanics.Consequently,an unsaturated soil has two phases that ﬂow under the inﬂuence of a stress gradient ͑i.e.,air and water ͒and two phases that come to equilibrium under the inﬂuence of a stress gradient ͑i.e.,soil particles forming a structural arrangement and the contractile skin forming a partition between the ﬂuid phases ͒͑Fredlund and Rahardjo 1993͒.The contractile skin has physical properties differing from the contiguous air and water phases and interacts with the soil structure to inﬂuence soil behavior.The contractile skin can be considered as part of the water phase with regard to changes in volume–mass soil properties but must be considered as an independent phase when describing the stress state and phenom-enological behavior of an unsaturated soil.Terzaghi ͑1943͒emphasized the important role played by surface tension effects associated with the air–water interface ͑i.e.,contractile skin ͒.Distinctive Features of the Contractile Skin :Numerous research studies on the nature of the contractile skin point toward its important,independent role in unsaturated soil mechanics.Terzaghi ͑1943͒suggested that the contractile skin might be in the order of 10−6mm in thickness.More recent studies suggest that the thickness of the contractile skin is in the order of 1.5–2water molecular diameters ͑i.e.,5Å͒͑Israelachvili 1991;Townsend and Rice 1991͒.A surface tension of approximately 75mN/m translates into a unit stress in the order of 140,000kPa.Lyklema ͑2000͒showed that the distribution of water molecules across the contractile skin takes the form of a hyperbolic tangent function as shown in Fig.4.Properties of the contractile skin are different from that of ordinary water and have a water molecular structure similar to that of ice ͑Derjaguin and Churaev 1981;Matsumoto and Kataoka 1988͒.The Young–Laplace and Kelvin equations describe fundamen-tal behavioral aspects of the contractile skin but both equations have limitations.The Young–Laplace equation is not able to explain why an air bubble can gradually dissolve in water without any apparent difference between the air pressure and the water pressure.The validity of the Kelvin equation becomes suspect as the radius of curvature reduces to the molecular scale ͑Adamson and Gast 1997;Christenson 1988͒.Terzaghi ͑1943͒recognized the limitations of the Kelvin equa-tion and stated that if the radius of a gas bubble “approaches zero,the gas pressure …approaches inﬁnity.However,within the range of molecular dimensions,”the equation “loses its validity.”Although Terzaghi recognized this limitation,later researchers would attempt to incorporate the Kelvin equation into formula-tions for the compressibility of air–water mixtures,to no avail ͑Schuurman 1966͒.The details of the laws describing the behav-ior of the contractile skin are not fully understood but the contractile skin is known to play a dominant role in unsaturated soil behavior.Terzaghi ͑1943͒stated that surface tension “is valid regardless of the physical causes.…The views concerning the molecular mechanism which produces the surface tension are still controversial.Yet the existence of the surface ﬁlm was established during the last century beyond any doubt.”Designation of the Stress StateState variables can be deﬁned within the context of continuum mechanics as variables independent of soil properties required for the characterization of a system ͑Fung 1965͒.The stress state variables associated with an unsaturated soil are related to equilibrium considerations ͑i.e.,conservation of energy ͒of a multiphase system.The stress state variables form one or more tensors ͑i.e.,3ϫ3matrix ͒because of the three-dimensional Cartesian coordinate system generally used for the formulation of engineering problems ͑i.e.,a three-dimensional world ͒.The description of the state variables for an unsaturated soil becomes the fundamental building block for an applied engineering science.The universal acceptance of unsaturated soil mechanics depends largely upon how satisfactorily the stress state variables can be deﬁned,justiﬁed,and measured.Historically,it has been the lack of certainty regarding the description of the stress state for an unsaturated soil that has been largely responsible for the slow emergence of unsaturated soil mechanics.Biot ͑1941͒was probably the ﬁrst to suggest the need for two independent stress state variables for an unsaturated soil.This is evidenced from the stress versus deformation relations used in the derivation of the consolidation theory for unsaturated soils.Other researchers began recognizing the need to use two independent stress state variables for an unsaturated soil as early as the 1950s.This realization can be observed through the three-dimensional plots of the volume change constitutive surfaces for an unsatur-ated soil ͑Bishop and Blight 1963;Matyas and Radakrishna 1968͒.It was during the 1970s that a theoretical basis and justi-ﬁcation was provided for the use of two independent stress state variables ͑Fredlund and Morgenstern 1977͒.The justiﬁcation was based on the superposition of coincident equilibrium stress ﬁelds for each of the phases of a multiphase system,within the context of continuum mechanics.From a continuum mechanics stand-point,the representative element volume ͑REV ͒must be sufﬁ-ciently large such that the density function associated with each phase is a constant.It should be noted that it is not necessary for all phases to be continuous but rather that the REV statistically represents the multiphase system.Although the stress analysis had little direct application in solving practical problems,it helped unite researchers on how best to describe the stress state of an unsaturated soil.Three possible combinations of independent stress state vari-ables were shown to be justiﬁable from the theoretical continuum mechanics analysis.However,it was the net normal stress ͓i.e.,␴−u a ,where ␴=total net normal stress and u a =pore–air pressure ͔and the matric suction ͑i.e.,u a −u w ,where u w =pore–water pres-sure ͒combination of stress state variables that proved to be the easiest to apply in engineering practice.The net normal stress primarily embraces the activities of humans which aredominatedFig.4.Density distribution across the contractile skin reprinted from Liquid–Fluid Interface ,V ol.3of Fundamental of Interface and Colloid Science,J.Lyklema ͑2000͒,with permission from Elsevierby applying and removing total stress͑i.e.,excavations,ﬁlls,and applied loads͒.The matric suction stress state variable primarily embraces the impact of the climatic environment above the ground surface.The stress state for an unsaturated soil can be deﬁned in the form of two independent stress tensors͑Fredlund and Morgenstern1977͒.There are three sets of possible stress tensors, of which only two are independent.The stress state variables most often used in the formulation of unsaturated soil problems form the following two tensors:΄͑␴x−u a͒␶yx␶zx␶xy͑␴y−u a͒␶zy␶xz␶yz͑␴z−u a͒΅͑1͒and΄͑u a−u w͒000͑u a−u w͒000͑u a−u w͒΅͑2͒where␴x,␴y,and␴z=total stresses in the x,y,and z directions, respectively;u w=pore–water pressure;and u a=pore–air pressure.The stress tensors contain surface tractions that can be placed on a cube to represent the stress state at a point͑Fig.5͒.The stress tensors provide a fundamental description of the stress state for an unsaturated soil.It has also been shown͑Barbour and Fredlund 1989͒that osmotic suction forms another independent stress tensor when there are changes in salt content of either a saturated or unsaturated soil.All the stress state variables are independent of soil properties and become the“keys”to describing physical phenomenological behavior,as well as deﬁning functional relationships for unsaturated soil properties.The inclusion of soil parameters at the stress state level is unacceptable within the context of continuum mechanics.As a soil approaches saturation,the pore–air pressure,u a, becomes equal to the pore–water pressure,u w.At this point,the two independent stress tensors revert to a single stress tensor that can be used to describe the behavior of saturated soils:΄͑␴x−u w͒␶yx␶zx␶xy͑␴y−u w͒␶zy␶xz␶yz͑␴z−u w͒΅͑3͒Variations in the Description of Stress StateStress tensors containing stress state variables form the basis for developing a behavioral science for particulate materials. The stress tensors make it possible to writeﬁrst,second,and third stress invariants for each stress tensor.The stress invariants associated with theﬁrst and second stress tensors are shown in Fredlund and Rahardjo͑1993͒.It is not imperative that the stress invariants be used in developing constitutive models;however, the stress invariants are fundamental in the sense that all three Cartesian coordinates are taken into consideration.There have been numerous equations proposed that relate some of the stress variables to other stress variables through the inclusion of soil properties.It is important to differentiate be-tween the role of these equations and the description of the stress state͑at a point͒in an unsaturated soil.It is also important to understand the role that these equations might play in subsequent formulations for practical engineering problems.The oldest and best known single-valued relationship that has been proposed is Bishop’s effective stress equation͑Bishop 1959͒:␴Ј=͑␴−u a͒+␹͑u a−u w͒͑4͒where␴Ј=effective stress and␹=soil parameter related to water degree of saturation,and ranging from0to1.Bishop’s equation relates net normal stress to matric suction through the incorporation of a soil property,␹.Bishop’s equation does not qualify as a fundamental description of stress state in an unsaturated soil since it is constitutive in character.It would be erroneous to elevate this equation to the status of stress state for an unsaturated soil.Morgenstern͑1979͒explained the limitations of Bishop’s effective stress equation as follows:•Bishop’s effective stress equation“…proved to have little impact on practice.The parameter,␹,when determined for volume change behavior was found to differ when determined for shear strength.While originally thought to be a function of degree of saturation and hence bounded by0and1,experi-ments were conducted in which␹was found to go beyond these bounds.•The effective stress is a stress variable and hence related to equilibrium considerations alone.”Morgenstern͑1979͒went on to explain:•Bishop’s effective stress equation“…contains the parameter,␹,that bears on constitutive behavior.This parameter is found by assuming that the behavior of a soil can be expressed uniquely in terms of a single effective stress variable and by matching unsaturated soil behavior with saturated soil be-havior in order to calculate␹.Normally,we link equilibrium considerations to deformations through constitutive behavior and do not introduce constitutive behavior into the stress state.Another form of Bishop’s equation has been used by several researchers in the development of elastoplastic models͑Jommi 2000;Wheeler et al.2003;Gallipoli et al.2003͒.␴ij*=␴ij−͓S w u w+͑1−S w͒u a͔␦ij͑5͒where␴ij=total stress tensor;␦ij=Kroneker delta or substitutiontensor;␴ij*=Bishop’s average soil skeleton stress;and Sw=water degree of saturation.In this case,the water degree of saturation has been substituted for the␹soil parameter.The above-mentioned equation is once again empirical and constitutive in character.Consequently,the Fig.5.Deﬁnition of stress state at a point in an unsaturated soil。

基于CD三轴试验的非饱和黄土吸应力强度参数确定

基于CD三轴试验的非饱和黄土吸应力强度参数确定张新婷;李同录;邢鲜丽;李萍【摘要】非饱和土强度参数的确定是其能够用于工程实际的关键.目前公认的非饱和土强度理论有Bishop的单变量理论、Fredlund的双变量理论以及LuNing的吸应力强度理论.其中吸应力强度理论基于吸应力特征曲线,可直接由常规三轴试验得出,回避了测定基质吸力的问题,便于在工程实际中推广.本文通过不同含水率的三轴CD试验,测得陕西泾阳原状Q2(L5)黄土的有效强度参数.结果表明,该黄土不同含水率的有效内摩擦角基本接近;有效黏聚力随含水率的增大呈指数递减,当含水率超过塑限时,黏聚力趋于定值.根据有效黏聚力和吸应力的关系,可以获得吸应力和含水率的关系,即吸应力特征曲线,并通过拟合得出吸应力函数,以及非饱和土强度表达式.%The study on strength theory of unsaturated soil and the determination of related parameters are the core of the research in unsaturated soil mechanics.At present,Bishop's single-variable strength theory,Fredlund's double-variables strength theory,and Lu Ning's suction stress strength theory are generally accepted.Lu Ning introduced the concept of suction stress and the suction stress characteristic curve (the relationship between the suction stress and the volumetric water content).This theory avoids the determination of matric suction and it is convenient for widely promotion in engineering practice.This paper tests the effective strength parameters based on the conventional triaxial CD test with different water contents.Results show that the effective internal friction angles with different water contents are basically same.The effective cohesion increases with the water content.When the watercontent increases to the plastic water content,the cohesion reaches a constant value.According to the relationship between effective cohesion and the stress suction,suction stress characteristic curve can be obtained and then fit the stress suction function.The function can explain unsaturated strength combined with the effective internal friction angle and saturated effective cohesion.【期刊名称】《工程地质学报》【年(卷),期】2017(025)001【总页数】7页(P36-42)【关键词】非饱和黄土;有效强度参数;吸应力;吸应力特征曲线【作者】张新婷;李同录;邢鲜丽;李萍【作者单位】长安大学,地质工程与测绘学院西安 710054;长安大学,地质工程与测绘学院西安 710054;中国地质调查局西安地质调查中心,国土资源部黄土地质灾害重点试验室西安 710054;太原理工大学矿业工程学院太原 030024;长安大学,地质工程与测绘学院西安 710054;中国地质调查局西安地质调查中心,国土资源部黄土地质灾害重点试验室西安 710054【正文语种】中文【中图分类】P642.3非饱和土理论是现代土力学的重要研究领域，其中强度理论是该领域研究的核心问题。

基于ABAQUS分析砼面板堆石坝坝后渗流场

基于ABAQUS分析砼面板堆石坝坝后渗流场[摘要]应用ABAQUS软件的位移—孔压单元计算钢筋混凝土面板堆石坝(CFRD,或简称面板坝)坝后渗流场中的各关键要素,解决了复杂边界、多种介质的面板坝稳定渗流问题,并通过实例验证。

[关键词] 面板坝渗流场ABAQUS有很多的方法和有限元软件计算渗流，而有限元软件中计算3D渗流场的有ANSYS、Seep3D和Adina，很少有人用ABAQUS，本文就主要介绍应用ABAQUS计算3D渗流场，并用实例验证。

1、ABAQUS简介ABAQUS是国际上最先进的大型通用有限元计算分析软件之一[1~2]，拥有不同种类的单元模型、材料模型、分析过程等，可以进行结构的静态与动态分析，其中，位移—孔隙压力单元可模拟固体与流体的相互作用，还可以进行饱和土—非饱和土的变形—渗流计算，不但用于稳定渗流，而且也可以用于超出达西定律的非线性渗流计算，这都可以说明，ABAQUS作为岩土工程分析渗流的专业软件来看待。

2、ABAQUS在饱和—非饱和渗流场中的分析2.1多孔介质中的液体流动在非饱和土中，支配着土壤水在液态下整体转移的是重力和水的表面张力，而在饱和土壤中，引起水分转移的力是重力和水的压力。

Richards等曾在1931年就证明非饱和土中的渗流与饱和土一样符合达西定律和连续方程[3]。

ABAQUS/Standard中处理多孔介质中的流体流动的方式和岩土工程的做法一致[4~5]，将多孔介质视为土、水和气体，土体的体积包括两部分：土颗粒的体积和孔隙的体积，孔隙的体积等于孔隙中液体的体积与气体的体积之和[6~7]，孔隙中的水也包含两部分：一是液体，另一部分是气体。

计算中将网格固定在土架上，气体或液体可流过网格，但要满足流体的连续性方程。

2.2非饱和渗流中的边界问题为了能说明问题，图1给出面板堆石坝的典型边界条件，具体为：图1 面板堆石坝典型边界图（1）S1为已知总水头边界条件，即总水头＝H1，对于已知总水头边界条件，ABAQUS/Standard中指定边界上的孔隙水压力即可即：（2）S2为已知总水头边界条件，即总水头2＝H2，对于已知总水头边界条件，ABAQUS/Standard中指定边界上的孔隙水压力即可，即：（3）S3为不透水边界条件，即通过该边界的流量为零，由于ABAQUS/Standard中默认所有的边界条件是不透水的，因此分析中无须额外设置。

非饱和土试验操作手册

GDS 非饱和土模块GDS 非饱和土三轴试验系统操作手册孔孔©GDS Instruments Ltd,2003关于本手册UNSAT用户手册描述了作为目前GDS三轴系统扩充的GDS非饱和土试验系统。

关于安装和运行UNSAT系统软件请参考GDSLAB软件手册。

该手册也可以和相应的GDSTTS，GDSTAS等系统的手册结合使用。

关于本手册 (1)1 简介 (3)2 GDSLAB 非饱和土软件模块 (3)3 如何完成非饱和土试验? (3)3.1 方法1 – GDS 1000cc 气压/体积控制器 (4)3.2 方法2 – HKUST 内压力室 / 差压测量 (6)3.3 测量大气压的要求 (8)3.4 用于非饱和土试验的GDS UNSAT底座 (8)3.5 高进气值陶土板的特性. (9)4 准备高进气值陶土板（饱和） (11)5 准备用于非饱和土试验的试样 (12)5.1 设置饱和度 (12)5.2 土水特征曲线 (12)5.3 在饱和或不饱和条件下的排水试验 (13)1 简介GDS非饱和土系统是传统三轴试验的扩展，主要用来研究地下水位以上的土地特性，可以模拟现场的应力状态和饱和状态。

应力路径的使用使得大多数标准试验可以模拟实际状态下饱和和非饱和试样的轴向和径向应力和孔隙水压、孔隙气压试验。

4D线性应力路径试验可以模拟现场的状态，轴向和径向应力，孔隙气压和水压可以同时变化。

在应力路径的每一个分支，计算每一个压力控制器的不连续的中间目标值。

对于这个试验，要进行下一个不连续的目标值，所有四个压力控制器必须汇聚到他们的当前目标值。

试验的影响是只能运行最慢的压力控制器的最大速度（通常是孔隙气压控制器，因为气体比除气水的压缩性更高）。

2 GDSLAB非饱和软件模块GDSLAB非饱和土试验模块的主要部分是4维应力路径。

4D应力路径可以同时控制孔隙气压、孔隙水压、径向和轴向控制器。

规则与饱和土试验中的应力版本（2D）一样，只是增加了控制孔隙气压和孔隙水压的功能。

非饱和土三轴仪应用及展望

非饱和土三轴仪应用及展望孙广利;王祥虎【摘要】非饱和土三轴仪作为一种比较先进的土工试验仪器,在自动化程度等方面具有常规三轴仪无法比拟的优势.对非饱和土三轴仪在土工试验中的应用进行了综述,并对未来发展趋势进行了展望.【期刊名称】《四川建材》【年(卷),期】2018(044)002【总页数】2页(P82,84)【关键词】非饱和土三轴仪;非饱和土【作者】孙广利;王祥虎【作者单位】吉林建筑大学测绘与勘查工程学院,吉林长春 130021;吉林建筑大学测绘与勘查工程学院,吉林长春 130021【正文语种】中文【中图分类】TU430 前言非饱和土三轴仪与常规三轴仪相比具有多方面的优势。

在测量土样的轴向应变方面，常规三轴仪采用的是外部位移传感器，且采用了透水石、滤纸等，这些辅助设施在试验时都存在误差；非饱和土三轴仪具有常规三轴仪无法比拟的极高精确度；非饱和土三轴仪系统在控制方式及数据采集方面全部采用电脑自动控制，其主要组成部分包括B&W压力室、GDS压力/体积数字控制器、霍尔效应传感器三部分。

通过查阅国内外有关非饱和土三轴仪的相关文献，本文对非饱和土三轴仪在非饱和土方面的研究现状进行了综述，并对非饱和土三轴仪在土工试验中的应用及未来发展趋势进行了探讨。

1 基质吸力与c、φ的研究基质吸力是孔隙气压力与孔隙水压力的差值。

基质吸力、土的内摩擦角φ、粘聚力c是非饱和土力学性质的重要参数，它们之间存在相关联系，并相互影响。

在此方面，叶为民等(2006)对上海地区软土的强度特征进行了非饱和土的三轴剪切试验研究。

实验结果表明，在基质吸力很低的范围内，上海地区软土的强度与吸力大致呈线性增长的关系，同时，得到了非饱和土的抗剪强度参数c=10.6 kPa[1-2]。

黄润秋等(2007)提出了新的非饱和土强度公式τf=Cu+(σ+Uε)tanφ′,非饱和土三轴仪实验得出的结果与上述公式吻合较好[3]。

李顺群等(2009)结合非饱和土三轴实验得出三点结论：①在饱和度很高的条件下，非饱和土的吸力摩擦角比净应力摩擦角大；②在水封闭条件下，强度的增长与基质吸力的增加大致上呈线性关系；③从宏观破坏特点看，非饱和试样与饱和土试样的破坏面是不一致的，非饱和土的破坏发生在很明显的斜面上[4]。

土木工程学科国际系列学术会议推荐表

Osaka, Japan 日本大阪
第十一届国际岩土力学计算机方法与新进 √ 展会议
11th International Conference of
June 19-24, 2005. Torino,
Italy 意大利都林
Computer Methods and Advances in
Geomechanics
Geotechnique Symposium 2005: Risk and
variability in geotechnical engineering
第十届国际工程地质会议
√
The 10th IAEG Congress
国际岩土物理模型会议
√
International Conference on Physical Modelling in Geotechnics
国际岩土技术会议：土体结构的交互作
√
用——计算方法与工程实践International geotechnical conference：Soil-
页码，2/3
2006年，泰国
2005年9月，韩国汉城
2005年7月4-6日，波兰格但斯克 4th-6th, July, 2005, Gdansk, Poland
Phoenix, Arizona, USA 美国亚利桑那州，菲尼克
斯大学
第二届国际结构混凝土联盟大会
√
June 5-8, 2006 Naples,
2nd International fib Congress
Italy 意大利那不勒斯
第二届国际混凝土结构维修学术会议
√
St-Malo, Brittany, 27-29
16 - 19 July 2006 Porto

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。

journal of soils and sediments评价 -回复

journal of soils and sediments评价-回复评价《Journal of Soils and Sediments》《Journal of Soils and Sediments》（土壤和沉积物杂志）是一份国际性的科学期刊，致力于土壤和沉积物领域的研究。

本文将一步一步回答关于《Journal of Soils and Sediments》的评价。

第一步：介绍期刊内容和范围《Journal of Soils and Sediments》是由Springer出版社出版的一份同行评议的期刊，涵盖了土壤和沉积物科学的各个方面，包括但不限于以下内容：土壤形成与演化，土壤物理、土壤化学、土壤生物学，土壤与环境交互作用，土壤污染与修复，土壤与水资源管理，沉积物物理、沉积物化学、沉积物生物学，沉积物与环境相互作用，沉积物作为环境指示物的应用等。

第二步：强调期刊的影响力和学术声誉《Journal of Soils and Sediments》是土壤和沉积物领域一个备受认可的期刊。

它被收录在众多重要的文献引用数据库中，如SCI、EI、Scopus 等。

这些数据库不仅是研究者们的重要信息来源，也是评估一个期刊影响力和学术声誉的标准之一。

第三步：评估期刊的审稿流程和质量《Journal of Soils and Sediments》的同行评议流程相当严格，确保研究成果的科学性和准确性。

每篇提交的论文都会经过编辑先行评估，然后分配给经验丰富的同行专家进行匿名审稿。

审稿人将对论文的质量、方法、结果和结论进行评估，并提出改进建议。

根据审稿人的意见，编辑决定接受、拒绝或要求作者进行修订。

这个审稿流程确保了期刊发表的论文具有高质量和广泛影响力。

第四步：分析期刊的撰写风格和语言质量《Journal of Soils and Sediments》的撰写风格非常规范和科学。

论文要求作者使用规范的科学写作格式，遵循期刊的指南和规定。

边坡稳定分析

非饱和土坡稳定是近年来人们所关心的热点,特别是降雨引起非饱和土坡失稳,给人们生产及安全带来了极大损失。

主要介绍了由于雨水入渗,使非饱和土坡的含水量发生变化,而含水量正是与基质吸力有着直接的联系。

正是由于基质吸力的变化才使整个土坡的整体稳定性也随着变化,也就是说安全系数与含水量分布有着必然的关系。

从而得出当土坡处于危险状况下的含水量分布,当土坡中的含水量达到危险含水量时,土坡处于危险状态。

这种含水量分布就叫做DVWCCP(Dangerous V olumetric Water Content Curves Profile)。

因此,通过监测土坡的含水量的变化来获得土坡的稳定信息,为生产和安全近年来,国内外学者对于非饱和土进行了比较深入的研究,取得了不少成果。

Vanapalli & Frendlund在1996年,提出了非饱和土的抗剪强度公式[1~2]:τf=c′+[σt-u a+S e(u a-u w)]tanυ′(1)其中:S e=S-S r1-S F式中:S———饱和度;S r———残余饱和度;τf———抗剪强度;σt———总应力;u a———孔隙气压力;u w———孔隙水压力;u a-u w———基质吸力;c′、υ′———有效内聚力和内摩擦角。

当S=1,也就是当土体饱和时,Se=1-Sr1-Sr=1,基质吸力ua-uw=0。

那么,非饱和土的抗剪强度公式就可以写成饱和土的抗剪强度公式:τf=c′+(σt-u w)tanυ′(2)这样公式(1)就把正的以及负的孔隙水压力都包括进去了[3],从而能够比较全面的进行计算土坡的稳定性。

文中采用公式(1)进行非饱和土坡的稳定性分析,下面详细介绍分析过程。

[1]L.T.Shao,Zh.P.Wang. On the stability of unsaturated soil slopes[Conf]. Proceedings of the Asian Conference on Unsaturated Soils,2000.825~829.[2]Vanapalli S.K,Frendlund D.G. Model for the Prediction of Shear Strength with Respect to Soil Suction.[J].Can. Geo. 1996.V ol.33.54~59.随着城市建设的发展,城市土地资源越来越紧张,因此充分利用地下空间将成为21世纪城市建设与发展的方向,对于北京地区来说,地下工程涉及的土质主要是非饱和土。

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