Triaxial creep tests of weak sandstone from fracture zone of high dam foundation
不同应力路径下砂岩真三轴试验及数值模拟
第52卷第3期2021年3月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.52No.3Mar.2021不同应力路径下砂岩真三轴试验及数值模拟李江腾，刘双飞，赵远，郭群(中南大学资源与安全工程学院，湖南长沙，410083)摘要：利用TRW-3000室内真三轴试验系统开展不同应力路径下的真三轴加载、卸载试验，研究其相应的力学特性，在此基础上开展PFC 3D 数值模拟对比试验，探讨细观裂纹演化规律。
研究结果表明：岩石最大、最小主应力差(σ1−σ3)与中间主应力σ2呈线性相关；基于Drucker −Prager 准则拟合不同应力路径下岩石强度效果良好；与加载相比，卸载条件下岩石黏聚力c 、内摩擦角φ均有所降低；PFC 3D 数值模拟试验破坏模式与室内试验破坏模式基本吻合；在不同应力路径下，数值模型剪切裂纹数与拉伸裂纹数均随ε1增大而增大，剪切裂纹比例曲线ε1随变化趋势呈“И”型，且当主应变ε1相同时，随着中间主应力σ2增大，各类裂纹数量减少；与加载相比，卸载时各类裂纹数量快速增加，剪切裂纹数占比降低，曲线由加载的“上凸”型转变为卸载的“下凹”型。
关键词：中间主应力；应力路径；数值模拟；裂纹演化中图分类号：TU43文献标志码：A开放科学(资源服务)标识码(OSID)文章编号：1672-7207（2021）03-0693-08True triaxial test and numerical simulation of sandstone indifferent stress pathsLI Jiangteng,LIU Shuangfei,ZHAO Yuan,GUO Qun(School of Resources and Safety Engineering,Central South University,Changsha,410083,China)Abstract:TRW-3000indoor true triaxial test system was used to carry out true triaxial loading and unloading tests in different stress paths to study the corresponding mechanical characteristics of the sandstone.On this basis,PFC 3D numerical simulation comparison test was carried out to explore the evolution law of microscopic cracks.The results show that the difference (σ1−σ3)between the maximum and the minimum principal stress of the rock is linearly related to the intermediate principal stress σ2.The Drucker-Prager criterion has good effect in fitting rock strength in different stress pared to load path,the cohesion c and the internal friction angle φof the rock are reduced under unloading conditions.The results of PFC 3D numerical simulation experiment are consistent with those of laboratory experiment.In different stress paths,the numbers of shear cracks and tensile cracks of theDOI:10.11817/j.issn.1672-7207.2021.03.004收稿日期：2020−04−10；修回日期：2020−06−12基金项目(Foundation item)：国家自然科学基金资助项目(51979293，51774322)；湖南省水利厅科技项目(2015131-5)(Projects(51979293，51774322)supported by the National Natural Science Foundation of China;Project(2015131-5)supported by the Science and Technology Program of Water Resources Department of Hunan Province)通信作者：郭群，高级实验师，从事岩石力学研究；E-mail:****************引用格式：李江腾,刘双飞,赵远,等.不同应力路径下砂岩真三轴试验及数值模拟[J].中南大学学报(自然科学版),2021,52(3):693−700.Citation:LI Jiangteng,LIU Shuangfei,ZHAO Yuan,et al.True triaxial test and numerical simulation of sandstone in different stress paths[J].Journal of Central South University(Science and Technology),2021,52(3):693−700.第52卷中南大学学报(自然科学版)numerical model increase with the increase of the maximum principal strainε1.Shear crack ratio curve with themaximum principal strainε1trends show"И"type.Under the same maximum principal strainε1,with the increaseof the intermediate principal stressσ2,the numbers of all kinds of cracks pared with loading,the number of various cracks increases rapidly and the proportion of shear cracks decreases.The curve changes from "upward convex"type under loading to"downward concave"type under unloading.Key words:intermediate principal stress;stress path;numerical simulation;crack evolution隧道、边坡、矿山等施工导致围岩应力状态发生变化，多表现为沿开挖工作面的应力降低，在此过程中，岩石表现出的力学性质直接影响工程的安全。
岩石混凝土损伤力学英文名著
岩石混凝土损伤力学英文名著In the realm of civil engineering and materials science, the study of rock and concrete damage mechanics is a critical field that has garnered significant attention. This branch of science delves into the understanding of the behavior of rock and concrete materials under various stress conditions, leading to their eventual failure or damage.Rock and concrete, being widely utilized in construction, are subjected to a plethora of forces and environmental conditions that can induce damage. The mechanics of this damage involve complex processes such as cracking, spalling, and fragmentation, which are influenced by the material's microstructure, stress history, and environmental exposure.One of the seminal works in this field is the research conducted by Professor H.H. Einstein, who developed a comprehensive model for the fracture process in rock. His work, which is extensively referenced in the literature, provides a theoretical framework for predicting the onset and progression of fractures in rock materials.In addition, the development of numerical models and simulation tools has been instrumental in advancing the understanding of damage mechanics in concrete. These models, such as the finite element method (FEM), allow engineers to simulate the behavior of concrete under various loading conditions, thereby predicting the onset of damage and thepotential for structural failure.Moreover, the incorporation of non-destructive testing (NDT) techniques has been vital in assessing the integrity of rock and concrete structures. Techniques such as ultrasonic testing, ground-penetrating radar, and acoustic emission monitoring provide valuable insights into the internal condition of these materials, identifying areas of potential weakness before catastrophic failure occurs.The study of rock and concrete damage mechanics is not only confined to theoretical and computational models. Experimental research plays a crucial role in validating these models and understanding the real-world behavior of these materials. Laboratories worldwide conduct a variety of tests, including uniaxial and triaxial compression tests, tensile tests, and fatigue tests, to study the response of rock and concrete to different types of stress.In conclusion, the study of rock and concrete damage mechanics is a multifaceted discipline that combines theoretical knowledge, computational modeling, and experimental research to enhance our understanding of material behavior under stress. This knowledge is essential for the design and maintenance of safe and durable structures in the built environment.。
基于非定常分数阶的岩石时效性蠕变模型
采矿与安全匸程学报Journal of Mining & Safety Engineering 笫38卷笫2期2021年03月Vol.38 No.2Mar. 2021文章编号：1673-3363-(2021 )02-0388-08基于非定常分数阶的岩石时效性蠕变模型刘文博巳张树光"，陈雷2(1.广西岩土力学与工程重点实验室，广西桂林541004； 2.辽宁工程技术大学土木工程学院*辽宁 阜新123000： 3.桂林理工人学上木打建筑工程学院，广西桂林541004)摘要 为了研究砂岩在不同围压作用下的蠕变特性，采用MTS 815.02试验机对砂岩进行三轴蠕变试验，进而分析了砂岩在不同围压作用下的蠕变变形规律。
将黏壶黏滞系数非定常化来构建非定常Abel 黏壶，在此基础上对分数阶阶数进行非定常化，进而建立一种基于非定常分数阶的砂岩时效性蠕变本构模型，使得该模型可以更好地描述岩石的加速蠕变变形规律；通过Levenberg-Marquardt 算法对三轴蠕变模型参数进行识别，来验证构建蠕变模型的正确性。
结果表明：在时间和应力双重作用影响下，将分数阶阶数)，当做是一个关于应力和时间的函数，构建的非定常分 数阶砂岩三维时效性蠕变本构模型可以很好地描述岩石的加速蠕变变形规律；模型曲线和试验曲 线拟合均在0.95以上，侧面证明了将分数阶阶数非定常化是可行的。
同时，采用单轴蠕变曲线和蠕变模型曲线进行对比，得出试验数据与一维时效性蠕变模型的吻合度也较高，这进一步说明了采用非定常化分数阶阶数建立的一维时效性蠕变模型是可靠的。
关键词分数阶；非定常化；时效性蠕变本构模型；加速蠕变；参数识别中图分类号 TD32 文献标志码 A DOI 10.13545/ki.jmse.2019.0563Time-dependent creep model of rock based onunsteady fractional orderLIU Wenbo 1'2, ZHANG Shuguang 1'3, CHEN Lei 2(1. Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering* Guilin, Guangxi 541004» China ；2. School of Civil Engi n eering a n d Transportation, Liaoning Technical University, Fuxin, Liaoning 123000, China ；3. School of Civil Engineering, Guilin U Diversity of Tech n ology, Guilin, Guangxi 541004, China )Abstract In order to study creep characteristics of sandst o ne un d er different con f ining pressure,triaxial creep test on sandstone was carried out with the testing machine of MTS 815.02, and the creepdefonnation of sandstone under different con f ining pressures was analyzed. An unsteady Abel clay potwas constructed with unsteady viscosity coefficient, based on which the fractional order was sorted interms of unsteady, and a time-dependent creep constitutive model based on unsteady fractionalsandstone was established for better description of accelerated creep deformation law. Finally,parameters of the triaxial creep model was identified with Levenberg ・Ma 「quanit algorithm to verify thecorrectness of the creep model. The results have shown that under dual influence of time and stress, withfractional order y regarded as a flmction of stress and time, the three-dimensional time-dependent creepconstitutive model of unsteady fractional sandstones constructed well describes the law of accelerated收稿日期：2020-11-23 责任编辑：宋爽基金项目:国家自然科学基金项11(51274109)作者简介：刘文博(1990—),男，甘肃省兰州市人,博士,从事地卜匸程与岩看本构模世方面的研究。
泥质砂岩三轴压缩力学特性试验研究
2020年35期众创空间科技创新与应用Technology Innovation and Application泥质砂岩三轴压缩力学特性试验研究*刘海壮，刘春*，张庆，黄富禹，周义舒（重庆科技学院安全工程学院，重庆401331）岩石是构造地壳地表岩体的主体成分，其构造十分复杂，是各种矿物质的集合体，不同岩石在其形成过程中的成因各不相同，造成岩石的物理特性和力学特性有很大差异，呈现出明显的非线性、不连续性、不均质性和各向异性等特点。
在地下空间工程领域，为了深入研究地下硐室开挖后的特征，了解岩石的基本构成和分类极为重要，其决定岩石力学性质和物理性质，是进行力学分析的关键因素之一。
获取岩石力学参数的主要手段之一是岩石的单轴、三轴试验，试验获得的粘聚力和内摩擦角等参数能为工程设计、硐室开挖及围岩支护提供有力依据。
目前许多学者对岩石力学特性已有深入研究。
姜永东等[1]研究了砂岩在饱和、自然、风干三种状态下的单轴和三轴抗压强度特征，得到应力与轴向、径向和体积应变间的关系曲线，根据试验数据绘制莫尔圆并通过回归分析得到强度参数粘聚力和内摩擦角的值。
李晓娟等[2]对粉砂岩试样进行三轴压缩实验，得到试样力学参数，并通过扫描电镜试验得到细观损伤图片，从微观角度分析了粉砂岩的力学特性。
李文帅等[3]通过砂岩真三轴加载试验，结合CT 扫描技术，研究了不同中间主应力条件下岩石的强度、变形及破坏特征，得到了砂岩真三轴条件下的力学特征。
本文通过常规三轴试验，介绍了岩石试样的制备过程，试验设备以及试验方案，并对实验结果进行了分析，得到岩石基本力学参数粘聚力和内摩擦角等，通过前人方法处理数据，得到岩石重要力学参数，方便工程实验人员运用，为类似试验处理提供技术指导。
1试验方法1.1试样制备及试验设备本次试验以泥质砂岩为研究对象，为保证试验获得参数准确可靠，在采样过程中，采样点位于隧道施工现场同一位置，岩石试样尽量均质，严格按照规定切割、打磨制成高为100mm 、直径为50mm 的圆柱样，试样直径和高度误差均不超过2mm ，岩石试样用保鲜膜包裹并裹上胶带，将试样打包放于泡沫纸箱运至岩石力学实验室。
滑坡的变形破坏行为与内在机理_许强
Journal of Engineering Geology工程地质学报1004－9665/2012/20（2）-0145-07滑坡的变形破坏行为与内在机理*许强（成都理工大学地质灾害防治与地质环境保护国家重点实验室成都610059）摘要自20世纪60年代日本学者斋藤借助于蠕变试验成果进行滑坡预测预报以来，人们就一直不停地对斜坡变形破坏行为和滑坡预报方法进行研究和探索，先后提出了数十种滑坡预测预报模型和方法。
随着滑坡变形监测实例的不断增多，其变形监测资料越来越丰富，各式各样的变形－时间曲线相继产生。
斜坡变形－时间曲线的类型、特征以及形成这些变形－时间曲线的力学条件等诸多问题都是滑坡预警预报必须查明的最基本科学问题。
本文通过对各类滑坡变形破坏行为和变形－时间曲线的分析总结，结合岩土体流变试验成果，根据斜坡变形－时间曲线特征，将滑坡分为稳定型、渐变型、突发型3类，并给出了产生这3类变形行为的力学条件。
同时，从细观力学的角度分析认为，斜坡产生宏观变形破坏行为的主要原因是岩土体细观尺度颗粒的“流动”和“微破裂”，但在不同岩性组成的斜坡和同一斜坡的不同变形阶段，“流动”和“微破裂”将分别发挥不同的作用。
关键词滑坡变形－时间曲线流变细观力学内在机理中图分类号：P642．22文献标识码：ATHEORETICAL STUDIES ON PREDICTION OF LANDSLIDES USING SLOPE DEFORMATION PROCESS DATAXU Qiang（State key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，Chengdu610059）Abstract Research on slope deformation and failure process and landslide prediction method has been undertaken freqeuently since Saito developed the landslide prediction and forecasting method with help of creep test in1960s．Dozens of models and methods for landslide prediction and forecasting have been put forward．With the increasing monitoring work on slope deformation and increasing available data，many kinds of displacement-time curves have been proposed．Many problems such as the types and features of slope displacement-time curves and the mechanic conditions forming the curves must be regarded as the most basic scientific problems．Theyhave to be answered and solved when landslide early warning and prediction are being carried out．This paper summarizes the landslide de-formation and failure mechanisms and their corresponding displacement-time curves．With the aid of rheological test，three types of landslide deformation and failure processes are proposed．They are thehe steady type，the grad-ual change type and the sudden failure type．Their corresponding mechanic conditions are also studied．In the view of micromechanics，the macro deformation and failure of a slope are mainly attributed to the flow and micro rupture of rock and soil in microscopic scale．The flow and micro rupture can play different roles in slopes with different li-thology or in different deformation phases of a slope．Key words landslide，displacement-time curve，rheology，micromechanics，failure mechanism*收稿日期：2012－01－30；收到修改稿日期：2012－03－14．基金项目：教育部创新团队发展计划（IRT0812），教育部高等学校科技创新工程重大项目培育资金项目（708079）．作者简介：许强，主要从事地质灾害预测评价及防治处理方面的教学与研究工作．Email：xuqiang_68@126．com1引言自20世纪60年代日本学者斋藤借助于蠕变试验成果来探索斜坡岩土体的变形破坏行为及预测预报方法［1 3］以来，人们就一直不停地对此问题进行研究和探索，先后提出了数十种滑坡预测预报模型和方法［4］。
低温作用下岩石基本力学性质试验研究_徐光苗(岩石力学与工程学报-2006-12)
compressive strength of rock. The cohesive strength and inner friction angle achieved by the triaxial compression tests increase with the decreasing of temperature with range of －10 ℃ to 20 ℃，and the red sandstone exhibits larger dependence on temperature. According to these test results，some valuable curves are obtained；and relevant
收稿日期：2005–09–07；修回日期：2006–01–05 基金项目：国家重点基础研究发展规划(973)项目(2002CB12704) 作者简介：徐光苗(1978–)，男，博士，2001 年毕业于长安大学地质工程系建筑工程专业，主要从事低温岩体 THM 耦合、低温岩体损伤及地下铁道 工程方面的研究工作。E-mail：xuguangmiao@
2.51
2.74
饱和含水 孔隙度
量/%
n/%
6.93 15.86
1.09
2.90
3 低温下岩石单轴压缩试验
3.1 试验准备 取干燥或饱和岩样，用乳胶套密封好，并逐一
红层泥岩水岩作用特征研究
表 1 红层软岩岩矿鉴定成果汇总表 Table 1 Statistics of m ineral and chem ical
composition of red beds
取样 地点
岩样 名称
矿物成份 / ( % )
铁
方褐
石
绢云母 长
泥
解铁
英
绿泥石 石
质
石矿
含石英粉砂
K90 铁质泥岩
15
85 少
KY90 -1
J ou rna l of Eng ineering Geology 工程地质学报 1004 - 9665 /2008 /16 (01) 20022205
红层泥岩水岩作用特征研究 3
张永安 ①② 李 峰 ① 陈 军 ②
( ①昆明理工大学国土资源工程学院 昆明 650093) ( ②中国水电顾问集团昆明勘测设计研究院勘察分院 昆明 650041)
© 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved.
24
Jou rna l of Eng ineering Geology 工程地质学报 2008
16 (1) 张永安等 :红层泥岩水岩作用特征研究
23
的水岩作用特征及对边坡稳定性的影响进行分析 。
2 红层工程地质特性
2. 1 地层岩性特征
滇中红层地区岩体多由薄 - 中厚层状的泥岩 、 泥质粉砂岩 、粉砂质泥岩 、粉砂岩 、砂岩等组成 ,一般 呈互层状产出 。红层岩性特征分述如下 : ( 1 )白垩 系 K1 - 2 :紫色 、灰紫色砂岩 、泥质粉砂岩夹泥岩 ,局 部呈软硬相间不等厚互层状 。 ( 2 )侏罗系上统 J3 : 紫色 、灰紫色泥岩 、泥质粉砂岩夹灰绿色泥灰岩 。 (3)侏罗系中统 J2 :紫红 、褐红 、灰紫色泥岩 、粉砂质 泥岩夹砂岩 、泥质粉砂岩 、灰绿色泥灰岩 。 ( 4)侏罗 系下 - 中统 J1 - 2 : 紫红色砂岩 、泥岩 、泥质粉砂岩互 层。
煤岩不同应力水平的蠕变及破坏特性
煤岩不同应力水平的蠕变及破坏特性赵斌;王芝银;伍锦鹏【摘要】对韩城地区3#和5#煤岩在9 MPa围压下进行三轴蠕变试验,通过分级加载试验获取不同应力水平下煤岩的蠕变曲线.建立不同应力水平下煤岩的蠕变本构方程,并根据试验数据进行参数识别.结果表明:当3#和5#煤岩样的轴向应力分别小于其瞬时抗压强度的60％、40％时,蠕变曲线仅包含瞬时变形阶段、衰减蠕变阶段和等速蠕变阶段,在等速蠕变阶段应变速率几乎为零;当3#和5#煤岩样的轴向应力分别介于其瞬时抗压强度的60％～80％、40％～80％时,等速蠕变阶段的应变速率近似为一常值;而当3#及5#煤岩样的轴向应力均为其瞬时抗压强度的80％以上,蠕变试验曲线分别表现出蠕变脆性破坏特性和蠕变韧-脆性破坏特性.【期刊名称】《中国石油大学学报（自然科学版）》【年(卷),期】2013(037)004【总页数】5页(P140-144)【关键词】煤岩;三轴蠕变试验;本构方程【作者】赵斌;王芝银;伍锦鹏【作者单位】中国石油大学城市油气输配技术北京市重点实验室,北京102249;中国石油大学城市油气输配技术北京市重点实验室,北京102249;中国石油大学城市油气输配技术北京市重点实验室,北京102249【正文语种】中文【中图分类】TU451煤层气井的排采是一个长期的过程，储层煤岩的蠕变特性会对煤层气井的稳定性以及储层的物理性质造成影响，进而影响煤层气的排采。
对煤岩或其他材料的蠕变特性，国内外学者进行了诸多研究。
通过蠕变试验，明确岩石的蠕变规律并测定蠕变参数，进而确定岩石蠕变模型是煤岩蠕变特性研究的一般方法［1-4］，也可以基于流变理论，导出岩石与其他材料的蠕变方程［5-7］，再通过试验确定其中的参数并验证其正确性。
三轴压缩蠕变试验中岩石试件的轴向应变或轴向应变率受到蠕变应力与围压的影响［8-10］。
一般地，岩石的蠕变过程可分为初始蠕变、稳态蠕变与加速蠕变3个阶段，脆性岩石的蠕变过程可分为初始蠕变、延迟弹性蠕变、塑性蠕变与脆性蠕变［11］。
三轴压缩下不同岩性煤岩体的强度及变形特征
三轴压缩下不同岩性煤岩体的强度及变形特征张宇;任金虎;陈占清【摘要】There are many lithology of coal and rock in coal mines,its mechanical strength and deforma-tion characteristics directly affect the roadway supporting effect. With CRIMS-DDL600 electronic universal testing machine,the sandstone,coal gangue and triaxial compression tests are carried out under different confining pressures. By means of the criterion of Moore explains different lithology of specimens damage Angle sizes,and by comparing the graphics and analysis of the phenomenon,the effect of confining pres-sure on the three samples stress-strain curve and deformation features is analyzed and compared. The re-sults show that:Specimens with three kinds of properties of the three axial compression process has gone through the initial compaction stage,elastic stage,yield and failure stage,and the more pressure and confi-ning,the longer specimen initial compression phase is;in confining pressure range,three kinds of failure forms of samples are not the same,and specimen failure angle's size of the three kinds of rock are of large difference,meanwhile there peak strength increases with the increase of confining pressure;also there properties are consistent with Coulomb strength criterion,and the size of cohesion and internal friction an-gle is given according to Moore's circle;with the growing of confining pressure,elastic modulus of three kinds increases,and the pressure effect on the elastic modulus varies due to the sample types.%煤矿井下存在多种岩性的煤岩体,其力学强度和变形特征直接影响巷道支护效果.利用CRIMS-DDL600电子万能试验机,进行了不同围压下砂岩、矸石与煤样的三轴压缩试验,采用莫尔准则诠释了不同岩性的试样破坏角大小不等,通过图形对比和现象分析,得到了围压对3种不同岩性的试样应力、应变曲线及变性特征的影响.结果表明:3种性质的试样三轴压缩过程中都经历了初始压密阶段、弹性阶段、屈服阶段与破坏阶段,且围压越大,试样初始压密阶段越长;在试验加载的围压范围内,3种性质的试样破坏形式并不相同,且3种不同岩性的试样破坏角大小相差较大,砂岩破坏角最大,煤破坏角最小,3种性质的试样其峰值强度随着围压的增大而增长;3种性质的试样符合Coulomb强度准则,依据莫尔应力圆给出3种试样内聚力和内摩擦角的大小;随着围压的增大,3种性质的试样弹性模量呈增大趋势,且围压对试样弹性模量的影响因试样类型的不同而不同.【期刊名称】《西安科技大学学报》【年(卷),期】2015(035)006【总页数】7页(P708-714)【关键词】三轴压缩;围压;破坏形式;峰值强度;弹性模量【作者】张宇;任金虎;陈占清【作者单位】中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221008;中国矿业大学力学与建筑工程学院,江苏徐州221008;内蒙古久和能源装备有限公司研发中心,陕西西安710018;中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221008;中国矿业大学力学与建筑工程学院,江苏徐州221008【正文语种】中文【中图分类】TD3150 引言天然岩层大都处于三向应力状态，这种应力状态下岩石的强度及其变形特征，对于研究岩层地质构造形成机制、地下工程围岩稳定性和深孔钻探等方面的工程实际问题具有重要意义［1-2］。
砂岩单轴三轴压缩试验研究
(1)
4 强度影响因素
影响岩石强度的因素有许多 , 大体可以分为两
类 , 一类是岩石本身的影响 , 如矿物成分 、颗粒大
小 、胶结情况 、密度 、孔隙比 、含水量 、生成条件
以及层理结构等 , 第二类是试验环境与物理环境如
试件尺寸 、形状 , 试件加工情况 、压力机的刚度 、 加载速度 、温度等〔3 ,7〕。
σc/σs 0164
图 4 砂岩在不同围压下的全应力应变曲线
图 6 莫尔圆包络线及强度准则
312 强度特性 砂岩在不同围压下的强度特征表现为 : 随围压
增大 , 抗压强度明显提高 , 塑性变形明显增大 , 其 变形不仅与围压σ3 大小有关 , 而且与σ1 - σ3 的大 小有关 , 当σ1 - σ3 在一定范围内 , 变形符合线弹 性变形规律 , 当σ1 - σ3 超过一定范围时 , 变形才 具有塑性变形 , 见图 5 。
1 试件的加工与试验设备 为了研究砂岩的力学特性 , 本次实验采用重庆
市云阳县寨坝滑坡体下盘的砂岩 , 将所取岩芯加工 成为圆柱体试件 , 试件直径 为 50mm , 高 h 为 100mm 。
单轴压缩试验采用日本 SHIMADZU 公司生产 的伺服式刚性试验机 , 该试验机可以进行拉伸 、压 缩 、剪切试验 , 轴向载荷最大 250kN , 可采用载荷 控制 、位移控制进行加载 , 计算机自动采集数据 。 本次进行的单轴压缩试验采用载荷控制 , 加载速度
图 3 第 3 组试件在三种状态下的应力与 纵向 、横向 、体应变曲线
饱和状态 自然状态 风干状态
表 1 砂岩在饱和 、自然 、风干状态下的强度σc 、屈服强度σs 、σs/σc 值
σc/ MPa
第 1 组试件 σs/ MPa
干燥和饱水状态下砂岩力学特性试验
第３７卷第１期２０２２年㊀３月矿业工程研究ＭｉｎｅｒａｌＥｎｇｉｎｅｅｒｉｎｇＲｅｓｅａｒｃｈＶｏｌ.３７Ｎｏ.１Ｍａｒ.２０２２ｄｏｉ:１０.１３５８２/ｊ.ｃｎｋｉ.１６７４－５８７６.２０２２.０１.００３干燥和饱水状态下砂岩力学特性试验谭涛ꎬ赵延林∗(湖南科技大学资源环境与安全工程学院ꎬ湖南湘潭４１１２０１)摘㊀要:为研究饱水对岩石力学特性的影响ꎬ以干燥砂岩和饱水砂岩为研究对象ꎬ利用ＭＴＳ８１５多功能岩石力学系统ꎬ对其进行１０ꎬ２０ꎬ３０ＭＰａ围压作用下的三轴压缩试验ꎬ得到干燥砂岩和饱水砂岩的偏应力－应变曲线和破坏形态ꎬ基于库伦准则ꎬ分析２种状态下砂岩的强度特征和变形特性.结果表明:随着围压的增大ꎬ干燥砂岩和饱水砂岩的峰值偏应力㊁残余偏应力㊁扩容起始偏应力㊁峰值轴向应变和体积应变不断增大ꎬ峰值侧向应变不断减小ꎻ在不同压缩阶段ꎬ饱水砂岩的内聚力和内摩擦角始终低于干燥砂岩ꎻ不同围压下ꎬ饱水砂岩破坏更为显著ꎬ其试件表面产生更多裂纹.关键词:砂岩ꎻ三轴压缩试验ꎻ饱水ꎻ强度中图分类号:ＴＤ４５２㊀㊀㊀文献标志码:Ａ㊀㊀㊀文章编号:１６７２－９１０２(２０２２)０１－００１５－０９ＴｅｓｔｏｆＳａｎｄｓｔｏｎｅ ｓＭｅｃｈａｎｉｃａｌＰｒｏｐｅｒｔｉｅｓｉｎＤｒｙａｎｄＷａｔｅｒ－ｓａｔｕｒａｔｅｄＳｔａｔｅＴＡＮＴａｏꎬＺＨＡＯＹａｎｌｉｎ(ＳｃｈｏｏｌｏｆＲｅｓｏｕｒｃｅｓꎬＥｎｖｉｒｏｎｍｅｎｔａｎｄＳａｆｅｔｙＥｎｇｉｎｅｅｒｉｎｇꎬＨｕｎａｎＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙꎬＸｉａｎｇｔａｎ４１１２０１ꎬＣｈｉｎａ)Ａｂｓｔｒａｃｔ:Ｔｏｓｔｕｄｙｔｈｅｗａｔｅｒ－ｓａｔｕｒａｔｅｄｅｆｆｅｃｔｏｎｒｏｃｋｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓꎬｔｈｉｓｐａｐｅｒｔａｋｅｓｔｈｅｄｒｙｓａｎｄｓｔｏｎｅａｎｄｗａｔｅｒ－ｓａｔｕｒａｔｅｄｓａｎｄｓｔｏｎｅａｓｔｈｅｒｅｓｅｒｃｈｏｂｊｅｃｔꎬｕｓｅｓｔｈｅＭＴＳ８１５ｍｕｌｔｉｆｕｎｃｔｉｏｎａｌｒｏｃｋｍｅｃｈａｎｉｃｓｓｙｓｔｅｍｔｏｃａｒｒｙｏｕｔｔｈｅｔｒｉａｘｉａｌｃｏｍｐｒｅｓｓｉｏｎｔｅｓｔｓｕｎｄｅｒ１０ꎬ２０ａｎｄ３０ＭＰａｃｏｎｆｉｎｉｎｇｐｒｅｓｓｕｒｅ.Ｄｅｖｉａｔｏｒｉｃｓｔｒｅｓｓ－ｓｔｒａｉｎｃｕｒｖｅｓａｎｄｆａｉｌｕｒｅｍｏｄｅｓｏｆｄｒｙｓａｎｄｓｔｏｎｅａｎｄｗａｔｅｒ－ｓａｔｕｒａｔｅｄｓａｎｄｓｔｏｎｅａｒｅｏｂｔａｉｎｅｄ.ＢａｓｅｄｏｎｔｈｅＣｏｕｌｏｍｂｃｒｉｔｅｒｉｏｎꎬｔｈｅｓｔｒｅｎｇｔｈａｎｄｄｅｆｏｒｍａｔｉｏｎｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｓａｎｄｓｔｏｎｅｉｎｔｈｅｔｗｏｓｔａｔｅｓａｒｅａｎａｌｙｚｅｄ.Ｒｅｓｕｌｔｓｓｈｏｗｔｈａｔｗｉｔｈｔｈｅｉｎｃｒｅａｓｅｏｆｃｏｎｆｉｎｉｎｇｐｒｅｓｓｕｒｅꎬｔｈｅｐｅａｋｄｅｖｉａｔｏｒｉｃｓｔｒｅｓｓꎬｒｅｓｉｄｕａｌｄｅｖｉａｔｏｒｉｃｓｔｒｅｓｓꎬｉｎｉｔｉａｌｄｅｖｉａｔｏｒｉｃｓｔｒｅｓｓｏｆｅｘｐａｎｓｉｏｎꎬｐｅａｋａｘｉａｌｓｔｒａｉｎａｎｄｖｏｌｕｍｅｔｒｉｃｓｔｒａｉｎｏｆｄｒｙａｎｄｗａｔｅｒ－ｓａｔｕｒａｔｅｄｓａｎｄｓｔｏｎｅｉｎｃｒｅａｓｅｃｏｎｔｉｎｕｏｕｓｌｙꎬｗｈｉｌｅｐｅａｋｌａｔｅｒａｌｓｔｒａｉｎｄｅｃｒｅａｓｅｓｃｏｎｔｉｎｕｏｕｓｌｙ.Ａｔｄｉｆｆｅｒｅｎｔｃｏｍｐｒｅｓｓｉｏｎｓｔａｇｅｓꎬｔｈｅｃｏｈｅｓｉｏｎａｎｄｉｎｔｅｒｎａｌｆｒｉｃｔｉｏｎａｎｇｌｅｏｆｗａｔｅｒ－ｓａｔｕｒａｔｅｄｓａｎｄｓｔｏｎｅａｒｅａｌｗａｙｓｌｏｗｅｒｔｈａｎｔｈｏｓｅｏｆｄｒｙｓａｎｄｓｔｏｎｅ.Ｔｈｅｄａｍａｇｅｄｅｇｒｅｅｏｆｗａｔｅｒ－ｓａｔｕｒａｔｅｄｓａｎｄｓｔｏｎｅｉｓｍｏｒｅｓｉｇｎｉｆｉｃａｎｔｕｎｄｅｒｄｉｆｆｅｒｅｎｔｃｏｎｆｉｎｉｎｇｐｒｅｓｓｕｒｅｓꎬａｎｄｍｏｒｅｃｒａｃｋｓａｐｐｅａｒｏｎｔｈｅｓｕｒｆａｃｅｏｆｔｈｅｓｐｅｃｉｍｅｎｓ.Ｋｅｙｗｏｒｄｓ:ｓａｎｄｓｔｏｎｅꎻｔｒｉａｘｉａｌｃｏｍｐｒｅｓｓｉｏｎｔｅｓｔｓꎻｗａｔｅｒ－ｓａｔｕｒａｔｅｄꎻｓｔｒｅｎｇｔｈ在隧道工程和采矿工程中ꎬ由于围岩的赋存条件ꎬ部分岩石会处于饱水状态.在岩石的饱水过程中ꎬ水－岩作用会对岩石造成损伤ꎬ并且饱水岩石内部孔隙和微裂纹中的水会进一步软化岩石ꎬ影响其力学性质.饱水岩石的力学特性是研究岩石与环境相互影响的一个重要基础.近年来ꎬ国内外学者对饱水岩石的力学特性㊁变形特征进行了大量研究ꎬ取得了丰富的成果.国内学者对大理岩[１－３]和花岗岩[４－６]进行了各种力学特性试验ꎬ发现水会弱化岩石的强度ꎬ降低岩石的内摩擦角和内聚力ꎻ刘建等[７]对干燥砂岩和饱水砂㊀收稿日期:２０２１－１２－１０基金项目:国家自然科学基金资助项目(５１７７４１３１)㊀㊀∗通信作者ꎬＥ－ｍａｉｌ:ｙａｎｌｉｎ＿８＠１６３.ｃｏｍ博看网 . All Rights Reserved.矿业工程研究２０２２年第３７卷岩进行了单轴蠕变试验ꎬ发现与干燥砂岩相比ꎬ饱水砂岩更容易发生蠕变现象ꎻ李佳伟[８]㊁杨春和[９]㊁宋勇军[１０]等通过三轴压缩试验ꎬ分析了水岩耦合作用下板岩的力学特性ꎬ并建立了力学参数预测模型ꎻ郭佳奇等[１１]对自然状态和饱水状态下的岩溶灰岩进行单轴压缩和三轴压缩试验ꎬ从能量角度对两者的损伤破坏过程进行了研究ꎬ发现随着试件含水率的增加ꎬ其可释放应变能与总应变能的比值下降ꎬ且饱和试件的应变能释放率大于自然状态下试件的应变能释放率ꎻ于怀昌等[１２]对干燥和饱水粉砂质泥岩进行了应力松弛试验ꎬ分析水对基本应力松弛参数的影响ꎬ并基于Ｈｏｏｋｅ－Ｋｅｌｖｉｎ模型ꎬ建立了岩石的非线性应力松弛损伤模型.这些研究成果对研究饱水岩石的力学特性具有重要的参考价值.为了更加深入研究干燥和饱水岩石的强度变化规律和破坏特征ꎬ本文以干燥砂岩和饱水砂岩为研究对象ꎬ对其进行不同围压作用下的三轴压缩试验.１㊀室内试验㊀图１㊀标准砂岩试件１.１㊀试件的制备试验所用砂岩取自河北马城铁矿砂岩含水层ꎬ该地区的砂岩在自然状态下长期处于饱水状态.该砂岩呈黄褐色ꎬ带有斑点ꎬ岩性为粗砂岩ꎬ主要成分为石英.将采集到的岩样制备成Ф５０ｍｍˑ１００ｍｍ的标准圆柱体试件ꎬ如图１所示.按照水利水电工程岩石试验规程(ＳＬ/Ｔ２４６ ２０２０)[１３]对试件进行饱水处理ꎬ并采用煮沸法强制饱水ꎬ测得砂岩试件的饱和吸水率在６.５６％左右.砂岩试件基本参数如表１所示.表１㊀砂岩试件基本参数编号高度/ｍｍ直径/ｍｍ上部中部下部干燥质量/ｇ饱水质量/ｇ饱和吸水率/％１１００.３２４９.８４４９.９２４９.９２４２９.６４２１００.３６４９.８２４９.８２４９.８２４３０.９６３１００.４０４９.８４４９.８２４９.８４４３０.７１４１００.３０４９.８６４９.７８４９.８４４３０.０３５１００.３０４９.８４４９.８２４９.８２４２９.０１６１００.４０４９.８２４９.８４４９.８２４３０.６４７１００.４２４９.８２４９.９０４９.８２４３０.５０４５８.３３６.４６５８１００.４２４９.８４４９.８６４９.８６４３０.６６４５８.６２６.４９２９１００.４０４９.８２４９.８６４９.８６４２９.９０４５８.２７６.５９９１０１００.３０４９.８４５０.００４９.８６４３０.７３４５９.１２６.５９１１１１００.３４４９.８２４９.８４４９.８２４２９.９１４５８.１２６.５６２１２１００.２０４９.８２４９.８２４９.８２４２８.９３４５８.７５６.９５２１.２㊀砂岩孔隙度测试岩石孔隙度是岩体最基本的性质ꎬ本试验随机选取３个饱水砂岩试件ꎬ采用ＡｎｉＭＲ－１５０核磁共振分析仪测量砂岩试件的孔隙度.测得砂岩孔隙类型为管状ꎬ孔隙度为１４.２３％~１４.３６％ꎬ如表２所示.表２㊀砂岩孔隙度测试结果编号体积/ｃｍ３孔隙度/％１＃１９６.３５１４.３６２＃１９６.３５１４.２３３＃１９６.３５１４.２４６１博看网 . All Rights Reserved.第１期谭涛ꎬ等:干燥和饱水状态下砂岩力学特性试验㊀㊀砂岩核磁共振试验结果如图２所示.由图２可知３个砂岩试件的核磁共振结果比较接近ꎬ表明该岩样比较均质ꎬ离散性较小ꎬ符合试验要求.在图２ａ中ꎬ弛豫时间越长ꎬ说明砂岩内部的孔隙越大ꎻ信号强度越高ꎬ说明孔隙的数量越多.从图２ｂ中可知ꎬ砂岩的孔径大小基本分布于０.０１~１０μｍꎬ主要为中孔和大孔.图２㊀砂岩核磁共振试验结果１.３ 三轴压缩试验装置及方案为研究饱水砂岩的力学特性ꎬ采用湖南科技大学ＭＴＳ８１５多功能岩石力学测试系统(如图３ａ所示)对砂岩进行三轴压缩试验ꎬ具体操作步骤:１)首先将试件放置于２个同等直径的刚性压盘中间ꎬ用热缩管将试件及刚性压盘与试件接触部分包裹ꎻ然后用热风枪均匀吹动热缩管ꎬ使其与试件和上下刚性压盘充分接触ꎬ即接触面无明显气泡ꎬ为防止在试验过程中ꎬ三轴腔内部的白油进入试件内部对其造成额外破坏ꎬ用铁丝将上下２个刚性压盘与热缩管进一步固定ꎻ最后将试件放置于试验系统底座指定中心位置ꎬ安装好环向引伸计和轴向引伸计ꎬ如图３ｂ所示.图３㊀砂岩三轴压缩试验装置２)加载阶段ꎬ以２.０ＭＰａ/ｍｉｎ的速度将围压和轴压加载至设定值ꎬ使其达到三轴静水压力状态(σ１＝σ２＝σ３)ꎬ维持１０ｍｉｎ.然后以轴向位移加载的方式进行偏应力加载ꎬ加载速率为０.１ｍｍ/ｍｉｎ[１４－１５]ꎬ直到试件破坏并达到残余阶段.试验加载路径示意图如图４所示.７１博看网 . All Rights Reserved.矿业工程研究２０２２年第３７卷图４㊀三轴试验加载路径１.４ 试验结果三轴压缩试验得到的干燥砂岩和饱水砂岩的偏应力－应变曲线如图５所示.从图５中可知ꎬ对于干燥砂岩和饱水砂岩ꎬ在不同的围压作用下ꎬ试件的偏应力－轴向应变曲线的变化趋势大体一致ꎬ均经历了５个阶段[１６－１９]ꎬ即原生裂隙压密阶段㊁线弹性阶段㊁裂纹稳定发展阶段㊁裂纹非稳定发展阶段和峰值阶段.这表明饱水并不会改变其应力－应变曲线的发展趋势.在峰前阶段ꎬ随着轴向偏应力的增加ꎬ侧向应变速率逐渐增大ꎻ并在相同的偏应力下ꎬ随着围压的增大ꎬ侧向应变数值变小.这是由于围压会抑制砂岩的侧向变形ꎬ从而降低了侧向应变.当应力达到峰值强度时ꎬ随着应变的增大ꎬ其应力迅速下降ꎬ表明饱水无法改变砂岩的岩性ꎬ饱水砂岩和干燥砂岩均为脆性岩样.试验后期ꎬ在围压的作用下ꎬ随着应变的增大ꎬ砂岩的应力基本保持不变ꎬ此时对应的轴向应力为砂岩的残余强度.图５㊀砂岩偏应力－应变曲线岩石进入塑性变形后会发生体积扩容现象.在岩石的三轴压缩试验中ꎬ砂岩试件为标准圆柱形ꎬ其体积应变εｖ可由式(１)求得.εｖ＝ε１＋２ε３.(１)式中:ε１ꎬε３分别为试件的轴向应变和侧向应变.根据式(１)计算ꎬ得到砂岩的体积应变－轴向应变曲线如图６所示.由图６可知ꎬ干燥砂岩和饱水砂岩的体积变形均经历体积压缩和体积膨胀阶段.体积压缩出现在试验加载初期ꎬ该阶段试件的体积应变随着轴向应变的增大而缓慢增大ꎬ然后出现一个 拐点 ꎬ此时试件的体积应变达到最大值ꎻ随着轴向应变的进一步增大ꎬ体积应变开始减小至０. 拐点 对应的轴向应力为试件的起始扩容应力.在体积膨胀阶段ꎬ干燥砂岩在１０ＭＰａ围压作用下ꎬ其体积应变随着轴向应变的增大而增大ꎬ最后基本保持不变ꎻ在２０ꎬ３０ＭＰａ的围压下ꎬ其体积应变随着轴向应变的增大而减小.而饱水砂岩的体积应变在不同的围压下都随着轴向应变的增大呈现逐渐减小的趋势.８１博看网 . All Rights Reserved.第１期谭涛ꎬ等:干燥和饱水状态下砂岩力学特性试验图６㊀砂岩的体积应变－轴向应变曲线三轴压缩过程中ꎬ试件的特征应力有峰值偏应力(σ１－σ３)ｍａｘ㊁扩容起始偏应力(σ１－σ３)ｄ和残余偏应力(σ１－σ３)ｒꎬ特征应变有峰值偏应力对应的轴向应变ε１ꎬｍａｘ㊁侧向应变ε３ꎬｍａｘ和体积应变εｖꎬｍａｘ.由图５和图６中的应力－应变曲线ꎬ可以得到干燥砂岩和饱水砂岩的特征应力和特征应变值ꎬ如表３所示.表３㊀砂岩试件的特征应力和特征应变值试件状态σ３/ＭＰａ(σ１－σ３)ｍａｘ/ＭＰａ(σ１－σ３)ｄ/ＭＰａ(σ１－σ３)ｒ/ＭＰａε１ꎬｍａｘε３ꎬｍａｘεｖꎬｍａｘ干燥砂岩１０１１７.８８８４.１１３２.６７０.０１２０５－０.００６６３－０.００１２０２０１４１.７２１０８.１０５５.１２０.０１４４０－０.００７６８－０.０００９５３０１７６.２９１３８.８３６８.２９０.０１６６０－０.００８７２－０.０００８４饱水砂岩１０１００.１６６９.５８３６.２１０.０１２０７－０.００７１６－０.００２２５２０１３３.３５１００.６８４８.４１０.０１３２０－０.００７３３－０.００１４６３０１４９.３３１１８.２１６４.６９０.０１５０４－０.００７５１０.００００１为了进一步分析不同饱水状态下ꎬ砂岩相关力学参数与围压的关系ꎬ根据表３的数据绘制散点图ꎬ如图７所示.由图７可知:在１０ꎬ２０ꎬ３０ＭＰａ的围压下ꎬ干燥砂岩的峰值偏应力和起始扩容偏应力均大于饱水砂岩的峰值偏应力和起始扩容偏应力ꎻ当围压为２０ꎬ３０ＭＰａ时ꎬ干燥砂岩残余偏应力大于饱水砂岩的残余偏应力ꎻ砂岩在干燥和饱水２种情况下ꎬ砂岩的峰值偏应力㊁起始扩容偏应力和残余偏应力与围压呈线性正相关关系ꎬ均随围压的增大而增大ꎬ但干燥砂岩的增长速度明显高于饱水砂岩.分别对σ１－σ３()ｍａｘꎬσ１－σ３()ｄ和σ１－σ３()ｒ与σ３的关系进行线性拟合(如图７ａ~图７ｃ所示)ꎬ得到拟合关系式:σ１－σ３()ｍａｘ＝ｋ１σ３＋ｄ１ꎻ(２)σ１－σ３()ｄ＝ｋ２σ３＋ｄ２ꎻ(３)σ１－σ３()ｒ＝ｋ３σ３＋ｄ３ꎻ(４)式中:ｋ１ꎬｄ１ꎬｋ２ꎬｄ２ꎬｋ３ꎬｄ３均为拟合系数.无论是干燥砂岩还是饱水砂岩ꎬ砂岩的峰值强度㊁起始扩容应力㊁残余强度与围压拟合的相关系数均大于０.９６ꎬ这表明使用式(２)~式(４)分别表达砂岩的峰值偏应力㊁起始扩容偏应力以及残余偏应力与围压的关系是合理可靠的.从图７ｄ可以发现ꎬ在不同围压作用下ꎬ干燥砂岩的峰值轴向应变始终高于饱水砂岩的轴向应变ꎬ且都随着围压的增大而增大.由图７ｅ和图７ｆ可知ꎬ在１０ＭＰａ的围压下ꎬ干燥砂岩的峰值侧向应变大于饱水砂岩侧向应变ꎬ当围压为２０ꎬ３０ＭＰａ时ꎬ干燥砂岩的峰值侧向应变小于饱水砂岩的峰值侧向应变ꎬ其峰值侧向应变随着围压的增大而减小ꎬ而体积应变随着围压的增大而增大.对砂岩峰值应变与围压的关系进行线性拟合(如图７ｅ~图７ｇ所示)ꎬ发现砂岩的峰值轴向应变㊁峰值９１博看网 . All Rights Reserved.矿业工程研究２０２２年第３７卷侧向应变㊁峰值体积应变与围压分别存在关系:ε１ꎬｍａｘ＝ｋ４σ３＋ｄ４ꎻ(５)ε３ꎬｍａｘ＝ｋ５σ３＋ｄ５ꎻ(６)εｖꎬｍａｘ＝ｋ６σ３＋ｄ６ꎻ(７)式中:ｋ４ꎬｄ４ꎬｋ５ꎬｄ５ꎬｋ６ꎬｄ６为拟合系数.饱水砂岩和干燥砂岩的峰值应变与围压的关系拟合的相关系数均大于０.９５ꎬ这表明用式(５)~式(７)表示砂岩的峰值应变与围压的关系是合理的.图７㊀干燥和饱水砂岩相关力学参数随围压变化关系０２博看网 . All Rights Reserved.第１期谭涛ꎬ等:干燥和饱水状态下砂岩力学特性试验２㊀砂岩强度与围压的关系分析２.１㊀基于莫尔－库伦准则的砂岩强度与围压关系在三轴压缩试验中ꎬ砂岩的峰值强度σｐ等于峰值偏应力与围压之和ꎬ即σｐ＝σ１－σ３()ｍａｘ＋σ３.(８)结合式(２)和式(８)ꎬ可以得到砂岩的峰值强度与围压的关系式ꎬ即σｐ＝ｋ１＋１()σ３＋ｄ１.(９)同理可以得到砂岩的起始扩容应力σｄ和残余强度σｒ与围压的关系式ꎬ即σｄ＝ｋ２＋１()σ３＋ｄ２ꎻ(１０)σｒ＝ｋ３＋１()σ３＋ｄ３.(１１)根据库伦准则ꎬ岩石的剪切强度准则为τ＝ｃ＋σｔａｎφ.(１２)式中:τ为剪切面上的剪应力ꎻσ为剪切面上的正应力ꎻｃ为内聚力ꎻφ为内摩擦角.库伦准则可以用莫尔极限应力圆表示ꎬ如图８所示.㊀图８㊀τ－α坐标下的库伦准则式(１２)的几何意义可以由图８中的直线ＡＬ表示ꎬ其斜率为内摩擦角的正切值ꎬ截距为内聚力ｃ.对应图８可以得到库伦准则的主应力表达式:σ＝１２σ１＋σ３()＋１２σ１－σ３()ｃｏｓ２θꎻτ＝１２σ１－σ３()ｓｉｎ２θ.ìîíïïïï(１３)式中:θ为岩石的断裂角ꎬ且２θ＝π２＋φ.将式(１３)代入式(１２)可得σ１＝１＋ｓｉｎφ１－ｓｉｎφσ３＋２ｃｃｏｓφ１－ｓｉｎφ.(１４)此外ꎬ定义砂岩在峰后残余阶段的内聚力为残余内聚力ｃｒꎬ内摩擦角为残余内摩擦角φｒꎬ同理可得残余强度σｒ与围压σ３的关系:σｒ＝１＋ｓｉｎφｒ１－ｓｉｎφｒσ３＋２ｃｒｃｏｓφｒ１－ｓｉｎφｒ.(１５)联立式(９)和式(１４)可以得到φ＝ａｒｃｓｉｎｋ１２＋ｋ１ꎻ(１６)ｃ＝ｄ１ｃｏｓφ２＋ｋ１().(１７)将图７中的拟合系数数值代入式(１６)和式(１７)ꎬ可以得到砂岩的内聚力和内摩擦角.同理可以得到１２博看网 . All Rights Reserved.矿业工程研究２０２２年第３７卷砂岩残余阶段的内摩擦角和内聚力ꎬ如表４所示.从表４中可以发现ꎬ饱水砂岩在不同阶段的内聚力和内摩擦角均小于干燥砂岩.表４㊀砂岩试件的内摩擦角和内聚力砂岩试件φ/(ʎ)ｃ/ＭＰａφｒ/(ʎ)ｃｒ/ＭＰａ干燥砂岩３６.４２１.９５２８.１７.００饱水砂岩３３.５２１.０７２４.５６.８５２.２㊀砂岩强度软化系数为分析在三轴压缩试验中干燥和饱水状态下砂岩强度的变化ꎬ定义峰值强度软化系数为Ｋｐꎬ起始扩容应力的软化系数为Ｋｄꎬ残余强度的软化系数为Ｋｒꎬ其计算公式为Ｋｐ＝１－σｗｐσｄｐꎻＫｄ＝１－σｗｄσｄｄꎻＫｒ＝１－σｗｒσｄｒ.ìîíïïïïïïïïï(１８)㊀图９㊀不同围压下饱水前后砂岩强度软化系数式中:σｗｐꎬσｗｄꎬσｗｒ分别为饱水砂岩的峰值强度㊁起始扩容应力和残余强度ꎻσｄｐꎬσｄｄꎬσｄｒ分别为干燥砂岩的峰值强度㊁起始扩容应力和残余强度.根据式(１８)可以得到砂岩的强度软化系数ꎬ如图９所示.从图９可知ꎬ砂岩的强度软化系数随着围压增加而上下波动.试件的峰值强度和起始扩容应力的软化系数相差不大ꎬ在１０ＭＰａ围压下ꎬ峰值强度软化系数和起始扩容应力软化系数达到最大值ꎬ分别为０.１３９和０.１５４ꎻ在２０ＭＰａ围压下影响最弱ꎬ其软化系数分别为０.０５２和０.０５８.在峰后残余阶段ꎬ砂岩残余强度的软化系数变化较大ꎬ其波动范围为－０.０８３~０.０８９.这表明饱水对砂岩强度的弱化作用会随着围压的变化而变化.３㊀破坏模式㊀㊀不同围压下ꎬ干燥砂岩和饱水砂岩的破坏形态如图１０和图１１所示.图１０㊀干燥砂岩破坏形态图１１㊀饱水砂岩破坏形态从图１０可知:在不同的围压作用下ꎬ干燥砂岩的破坏形态均为单斜面剪切破坏ꎬ裂纹为剪切裂纹.这是因为该砂岩具有明显的矿物颗粒ꎬ由于矿物颗粒间的黏结强度较低ꎬ进而出现单一的剪切面ꎻ又因为砂岩试件与试验仪器的垫块之间的接触面存在摩擦作用[２０]ꎬ砂岩试件出现从端部开始自上而下的对角破坏.此外ꎬ可以发现随着围压的增大ꎬ试件的破裂角从７０ʎ减小至６３ʎ.从图１１可以看出:不同围压作用下ꎬ饱水砂岩的破坏形态以单斜面剪切破坏为主ꎬ试件产生一条从上２２博看网 . All Rights Reserved.第１期谭涛ꎬ等:干燥和饱水状态下砂岩力学特性试验到下的斜剪切主裂纹ꎬ也出现了次生的剪切裂纹.饱水砂岩的破裂角随着围压的增大而减小ꎬ与干燥砂岩一致.比较图１０和图１１可以发现:在１０ＭＰａ的围压下ꎬ两者的破裂角相等ꎻ随着围压的增大(围压为２０ＭＰａ和３０ＭＰａ)ꎬ饱水砂岩的破裂角均小于干燥砂岩的破裂角.总体上ꎬ饱水对砂岩试件的破坏形态造成了较大的影响ꎬ而且降低了砂岩的破裂角.４㊀结论１)干燥和饱水砂岩的强度特征与变形特性都受到围压影响ꎬ它们的峰值偏应力㊁起始扩容偏应力㊁残余偏应力㊁峰值轴向应变和峰值体积应变与围压呈正相关关系ꎬ而峰值侧向应变与围压呈负相关关系.２)饱水会降低砂岩在不同阶段的内聚力和内摩擦角ꎬ使得饱水砂岩的峰值强度㊁起始扩容应力和残余强度均低于干燥砂岩的强度.此外ꎬ饱水对砂岩的弱化作用受到围压的影响ꎬ砂岩的峰值强度和起始扩容应力在１０ＭＰａ围压下弱化最大ꎬ而残余强度在２０ＭＰａ的围压下饱水的弱化作用最为显著.３)干燥砂岩和饱水砂岩的破裂角均随着围压的增大而减小.但是由于水对岩石的腐蚀作用ꎬ与干燥砂岩的单斜面剪切破坏相比ꎬ饱水砂岩的破坏模式更为复杂ꎬ其主剪切破坏面附近出现了次生剪切裂纹.参考文献:[１]陈钢林ꎬ周仁德.水对受力岩石变形破坏宏观力学效应的实验研究[Ｊ].地球物理学报ꎬ１９９１(３):３３５－３４２.[２]杨圣奇ꎬ苏承东ꎬ徐卫亚.大理岩常规三轴压缩下强度和变形特性的试验研究[Ｊ].岩土力学ꎬ２００５ꎬ２６(３):４７５－４７８.[３]杨圣奇ꎬ徐卫亚ꎬ谢守益ꎬ等.饱和状态下硬岩三轴流变变形与破裂机制研究[Ｊ].岩土工程学报ꎬ２００６ꎬ２８(８):９６２－９６９.[４]罗丹旎ꎬ苏国韶ꎬ何保煜.不同饱水度花岗岩的真三轴岩爆试验研究[Ｊ].岩土力学ꎬ２０１９ꎬ４０(４):１３３１－１３４０.[５]李铀ꎬ朱维申ꎬ白世伟ꎬ等.风干与饱水状态下花岗岩单轴流变特性试验研究[Ｊ].岩石力学与工程学报ꎬ２００３(１０):１６７３－１６７７.[６]陈旭ꎬ俞缙ꎬ李宏ꎬ等.不同岩性及含水率的岩石声波传播规律试验研究[Ｊ].岩土力学ꎬ２０１３ꎬ３４(９):２５２７－２５３３.[７]刘建ꎬ李鹏ꎬ乔丽苹ꎬ等.砂岩蠕变特性的水物理化学作用效应试验研究[Ｊ].岩石力学与工程学报ꎬ２００８ꎬ２７(１２):２５４０－２５５０.[８]李佳伟ꎬ徐进ꎬ王璐ꎬ等.砂板岩岩体力学特性的水岩耦合试验研究[Ｊ].岩土工程学报ꎬ２０１３ꎬ３５(３):５９９－６０４.[９]杨春和ꎬ冒海军ꎬ王学潮ꎬ等.板岩遇水软化的微观结构及力学特性研究[Ｊ].岩土力学ꎬ２００６ꎬ２７(１２):２０９０－２０９８.[１０]宋勇军ꎬ雷胜友ꎬ毛正君ꎬ等.干燥和饱水状态下炭质板岩力学特性试验[Ｊ].煤炭科学技术ꎬ２０１４ꎬ４２(１０):４８－５２.[１１]郭佳奇ꎬ刘希亮ꎬ乔春生.自然与饱水状态下岩溶灰岩力学性质及能量机制试验研究[Ｊ].岩石力学与工程学报ꎬ２０１４ꎬ３３(２):２９６－３０８.[１２]于怀昌ꎬ赵阳ꎬ刘汉东ꎬ等.三轴应力作用下水对岩石应力松弛特性影响作用试验研究[Ｊ].岩石力学与工程学报ꎬ２０１５ꎬ３４(２):３１３－３２２.[１３]中华人民共和国水利部.水利水电工程岩石试验规程:ＳＬ/Ｔ２４６ ２０２０[Ｓ].北京:中国水利水电出版社ꎬ２０２０.[１４]赵延林ꎬ廖健ꎬ刘强ꎬ等.水－力耦合和隔离状态下孔道砂岩力学特性的对比[Ｊ].煤炭学报ꎬ２０２０ꎬ４５(１２):３９７３－３９８３.[１５]赵延林ꎬ刘强ꎬ刘欢ꎬ等.水－力耦合作用下单裂隙灰岩三轴压缩与声发射试验及压剪断裂模型[Ｊ].煤炭学报ꎬ２０２１ꎬ４６(１２):３８５５－３８６８.[１６]ＢＩＥＮＩＡＷＳＫＩＺＴ.Ｍｅｃｈａｎｉｓｍｏｆｂｒｉｔｔｌｅｆｒａｃｔｕｒｅｏｆｒｏｃｋ:ＰａｒｔｓＩꎬＩＩａｎｄＩＩＩ[Ｊ].ＩｎｔｅｒｎａｔｉｏｎａｌＪｏｕｒｎａｌｏｆＲｏｃｋＭｅｃｈａｎｉｃｓａｎｄＭｉｎｉｎｇＳｃｉｅｎｃｅ＆ＧｅｏｍｅｃｈａｎｉｃｓＡｂｓｔｒａｃｔｓꎬ１９６７ꎬ４(４):３９５－４０６.[１７]ＭＡＲＴＩＮＣＤꎬＣＨＡＮＤＬＥＲＮＡ.ＴｈｅｐｒｏｇｒｅｓｓｉｖｅｆｒａｃｔｕｒｅｏｆＬａｃｄｕＢｏｎｎｅｔｇｒａｎｉｔｅ[Ｊ].ＩｎｔｅｒｎａｔｉｏｎａｌＪｏｕｒｎａｌｏｆＲｏｃｋＭｅｃｈａｎｉｃｓａｎｄＭｉｎｉｎｇＳｃｉｅｎｃｅ＆ＧｅｏｍｅｃｈａｎｉｃｓＡｂｓｔｒａｃｔｓꎬ１９９４ꎬ３１(６):６４３－６５９.[１８]ＧＯＫＴＡＮＲＭꎬＹＩＬＭＡＺＮＧ.Ａｎｅｗｍｅｔｈｏｄｏｌｏｇｙｆｏｒｔｈｅａｎａｌｙｓｉｓｏｆｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｒｏｃｋｂｒｉｔｔｌｅｎｅｓｓｉｎｄｅｘａｎｄｄｒａｇｐｉｃｋｃｕｔｔｉｎｇｅｆｆｉｃｉｅｎｃｙ[Ｊ].Ｊｏｕｒｎａｌ－ＳｏｕｔｈＡｆｒｉｃａｎＩｎｓｔｉｔｕｔｅｏｆＭｉｎｉｎｇａｎｄＭｅｔａｌｌｕｒｇｙꎬ２００５ꎬ１０５(１０):７２７－７３２.[１９]ＣＨＥＮＸꎬＹＵＪꎬＴＡＮＧＣＡꎬｅｔａｌ.Ｅｘｐｅｒｉｍｅｎｔａｌａｎｄｎｕｍｅｒｉｃａｌｉｎｖｅｓｔｉｇａｔｉｏｎｏｆｐｅｒｍｅａｂｉｌｉｔｙｅｖｏｌｕｔｉｏｎｗｉｔｈｄａｍａｇｅｏｆｓａｎｄｓｔｏｎｅｕｎｄｅｒｔｒｉａｘｉａｌｃｏｍｐｒｅｓｓｉｏｎ[Ｊ].ＲｏｃｋＭｅｃｈａｎｉｃｓ＆ＲｏｃｋＥｎｇｉｎｅｅｒｉｎｇꎬ２０１７ꎬ５０(６):１５２９－１５４９.[２０]苏承东ꎬ付义胜.红砂岩三轴压缩变形与强度特征的试验研究[Ｊ].岩石力学与工程学报ꎬ２０１４ꎬ３３(ｓ１):３１６４－３１６９.３２博看网 . All Rights Reserved.。
岩石疲劳破坏的变形控制律
第 30 卷 2008 年第1期 1月岩土工程学报Chinese Journal of Geotechnical EngineeringVol.30 No.1 Jan., 2008岩石疲劳破坏的变形控制律、岩土力学试验的实时 X 射线 CT 扫描和边坡坝基抗滑稳定分析的新方法葛修润(1.中国科学院武汉岩土力学研究所，湖北 武汉 430071；2.上海交通大学岩土力学与工程研究所，上海 200030；3.岩土力学与 工程国家重点实验室，湖北 武汉 430071)摘要：介绍了近年来在岩土力学领域方面取得的一些进展:①关于岩石疲劳破坏试验方面的实验结果。
大量的试验清楚表明岩石发生疲劳破坏时的变形量受岩石应力-应变 全过程曲线控制的规律，介绍了这方面的试验技术及新型的岩石力学试验机——RMT 机的特性，对岩石的 I 型和Ⅱ型分类作了评述。
岩石疲劳试验结果也提示我们在研究 岩石的强度理论时要特别重视从变形角度去探讨。
②简要介绍了岩土力学室内试验方 面的一项新的实验技术——实时 X 射线 CT 扫描的试验方法和原理。
重点给出了南桥 砂岩三轴试验的结果，并与典型的全过程曲线作了对比分析。
这一新技术为岩土力学 界提供了一种新手段，使宏观的力学性能与细观层次上的结构演变和裂纹萌生、扩展 直到破坏有机地联系起来，为损伤研究提供了一种新的实验手段。
③论述了采用强度 储备概念求抗滑稳定安全系数方面的不足之处。
基于力是矢量这一基本概念，提出了 计算抗滑稳定安全系数的新方法——矢量和分析方法，并与传统分析方法作了对比， 指出了这种新方法的优点。
除了平面问题外，还论述了三维问题的计算方法和算式。
关键词：岩土力学；周期荷载；疲劳；不可逆变形；应力–应变全过程曲线；损伤扩 展机理；CT 实时试验；边坡与坝基；抗滑稳定分析；矢量和分析法；安全系数 中图分类号：TU45 文献标识码：A 文章编号：1000–4548(2008)01–0001–20 作者简介：葛修润（1934– ），男，上海市人，岩土力学专家，中国工程院院士。
利用印达隆石灰石废物砂石和碎石作为严实路面砖石的替代物说明书
Utilization of Silica Sand and Gravelfrom Indarung Limestone Waste as AggregateSubstances for Rigid PavementEtri Suhelmidawati(B),Fahmiza Yufajri,Muhammad Ikhsan,Gusriyaldi,and Zulfira MiraniDepartment of Civil Engineering,Politeknik Negeri Padang Jalan Kampus Limau Manis,Kec.Pauh,Padang25164,West Sumatera,Indonesia*********************Abstract.Roads have a very important role in advancing national development,structures made of concrete are very susceptible to cracking due to the brittle natureof the material and the nature of concrete that is strong against pressure,but weakagainst pulling.And the utilization of waste material as substitution of aggregatein concrete has been increasing nowadays.Therefore in this research,the useof silica sand and gravel from Indarung limestone waste were investigated.Thepurpose of this study is to determine the utilization of silica sand and gravel affectthe compressive strength of the concrete as a substitution of coarse aggregates andfine aggregates in concrete mixtures in order to increase the value of compressivestrength and bending strength in concrete,especially for rigid pavements.Themethod in this research applies experimental methods,the tests carried out in thisstudy include material testing,compressive strength testing and concrete bendingstrength testing.Testing is carried out referring to the American Standard Testingand Materials(ASTM).Based on the experimental results;the highest compressivestrength value of concrete obtained in the3rd concrete variation with a concretemixture of100%Silica sand+Natural gravel+Sikament NN with a value of41.14MPa.For the optimum bending strength value obtained in a concrete mixturewith the4th variation,namely100%Natural sand+Silica Gravel+Sikament NNwith a value of1.6MPa.Based on the results in road planning,the4th concretevariation was used as a variation that will be applied on the basis of its optimumbending strength value and a compressive strength value that exceeds the designcompressive strength which is32.36MPa.The planning for rigid pavement onJalan Simpang Anak Aia–Fly Over Minangkabau International Airport STA22+800to STA22+800by using the MDP2017method,with the pavement thicknessof27.5cm.Keywords:concrete·pavement·silica·strength1IntroductionRoads have a very important role in advancing national development.In recent years, the use of rigid pavement for roads has become more common.Structures made of ©The Author(s)2023T.P.Syawitri et al.(Eds.):MEST2022,AER222,pp.448–460,2023.https:///10.2991/978-94-6463-134-0_43Utilization of Silica Sand and Gravel from Indarung Limestone Waste449 concrete are very susceptible to cracking due to the brittle nature of the material as well as the properties of concrete that are strong against pressure,but weak against tensile. The weak tensile properties cause concrete to crumble or break without changing shape when the maximum stress is reached.Structures made of concrete are very susceptible to cracking due to the brittle nature of the material as well as the properties of concrete that are strong against pressure,but weak against tensile.The weak tensile properties cause concrete to crumble or break without changing shape when the maximum stress is reached[1].The use of silica sand is often used for metallurgical sand,which is sand produced from the processing of a mineral or metal from silica sand.Silica sand is widely used in industrial activities in which its use is used according to its characteristics,including being used as glass making production,ceramic manufacturing,clean water production filters,concrete casting,sandblasting to clean iron rust crusts such as machines,pipes, plates and so on.In concrete castingfine aggregate or silica sand is used as the main element in the manufacture of fresh concrete in the batching plant,in addition to coarse aggregate,cement and water and additives[2].Due to these limitations,it was decided that the supply of silica from the mine was only to meet the needs of the Indarung plant,while at the factory in October2016it was decided to use Pozzolan as a substitute for the limited silica from the mine.From this data it can be concluded that the use of silica is lacking in the cement manufacturing process and becomes an unused material.Indarung factory waste can be a benefit to the community because it is not every region has silica material.Silica material can be used as an alternative to aggregate replacement for mixed materials in concrete so that it can open up job opportunities for the community and be able to improve the community’s economy.In this study,further research was conducted on the extent to which silica sand and gravel affect the compressive strength and bending strength of concrete as a substi-tute for coarse aggregate andfine aggregate in concrete mixes[3]in order to increase the compressive strength andflexural strength values of concrete,especially for rigid pavements.2Research MethodologyThe method in this research applies the experimental method.The tests carried out in this study include material testing[4],compressive strength testing and concreteflexural strength testing.Tests were carried out referring to the American Standard Testing and Material(ASTM)as well as some previous research literature that has been carried out in Concrete Laboratory,Department of Civil Engineering,Politeknik Negeri Padang.Silica material used in this research are from Indarung limestone waste,whilefine and coarse aggregate are from natural aggregate in West Sumatera.This research was conducted to obtain the composition of the silica aggregate mixture as an additional ingredient in concrete,where the results of this study are the results of compressive strength,flexural strength of concrete and for rigid pavement design.In this research,there arefive types of variations in the percentage of silica aggregate that will be added to the concrete mixture, where thefive variations include,100%natural sand+natural gravel,100%natural sand450 E.Suhelmidawati et al.Table1.Slump test result(cylinder samples)Samples H1H2H3Average 100%fine aggregate+coarse aggregate99.5109.5100%fine aggregate+coarse aggregate+sika1110.51010.5100%silica sand+coarse aggregate+sika11.5111010.8100%fine aggregate+silica gravel+sikaflowflowflow0.0100%silica sand+silica gravel+sika8888.0Table2.Slump test result(beam samples)Samples H1H2H3Rata-Rata 100%fine aggregate+coarse aggregate9.5101110.2100%fine aggregate+coarse aggregate+sika98129.7100%silica sand+coarse aggregate+sika911.51010.2100%fine aggregate+silica gravel+sikaflowflowflow0.0100%silica sand+silica gravel+sikaflowflowflow0.0+natural gravel+Sikament NN,100%silica sand+natural gravel+Sikament NN, 100%natural sand+silica gravel+Sikament NN and100%silica sand+silica gravel +Sikament NN.The amount of Sikamen used is about2.3%.[5].Mix design method for high strength concrete is based on ACI211.4R-93Guided for Selecting Proportions for High Strength Concrete.And for rigid pavement design is based on MDP2017.3Results and Discussion3.1Fresh Concrete TestingThe results of the slump and weight content tests with silica sand and gravel as aggregate substitutes in concrete mixes with cylinder samples can be seen in Table1and beam samples can be seen in Table2.The slump value has a plan slump limit of80–120mm.[6].However,in the man-ufacture of the mixture there are several conditions that are caused by the addition of additives,namely Sikamen NN,which gives watery properties to the concrete but is fast in the concrete setting process,so that when the concrete slump test is carried out,the flow concrete slump is obtained.3.2Compressive Strength TestingSome variations of silica sand and gravel as aggregate substitution in concrete mixtures for compressive strength testing are as follows:Utilization of Silica Sand and Gravel from Indarung Limestone Waste451 Table3.28-day compressive strength.Samples Weight of Sample(kg)Force(kN)Compression strength(MPa)Average of compressive strength (MPa)112.320306.5917.3617.2812.245299.6316.9612.545309.4717.52212.41478.6239.7336.1012.5439.6836.4912.565386.6532.09312.52483.9140.1641.1412.50488.4140.5412.55514.7642.73412.745451.8837.5132.3612.870374.3731.0712.885343.2228.49513.255301.4025.0226.5212.880338.4828.0912.895318.5626.441.100%fine aggregate+coarse aggregate2.100%fine aggregate+coarse aggregate+sika3.100%silica sand+coarse aggregate+sika4.100%fine aggregate+silica gravel+sika5.100%silica sand+silica gravel+sikaThe results of testing the compressive strength of sand concrete and silica gravel as aggregate substitution at the age of28days.[7].Can be seen at Table3.From the graph in Fig.1,it can be seen that the highest compressive strength value is found in3rd variation(100%silica sand+coarse aggregate+sika)with an average compressive strength value of41.14MPa,then concrete with2nd variation(100%fine aggregate+coarse aggregate+sika)with a compressive strength of36.10MPa and concrete4th variation(100%fine aggregate+silica gravel+sika)with a concrete compressive strength value of32.36MPa,so that it can meet the compressive strength plan in this study,namely fc’30MPa.3.3Flexural Strength TestingThe results of theflexural strength test of sand concrete and silica gravel as aggregate substitution at the age of28days.[8],can be seen in Table4.452 E.Suhelmidawati et al.17.2836.1041.1432.3626.5212345Cylinder variaƟonpressive strength Table 4.28-day flexural strength.Variation Weight of Sample (kg)Notation (mm)Compressive strength (kN)Flexural strength (MPa)l b h 131.660450150154130.731.19045015215314.40.8233.06545015315322.1 1.232.93045015315321.1 1.1332.91545015215320.7 1.132.62545015015321.2 1.2432.90545015015027.4 1.533.02545015015028.4 1.6529.21545015015026.3 1.429.36045015015032.61.8From the graph in Fig.2,it can be seen that the highest flexural strength value is found in 4th variation (100%Silika gravel +fine aggregate +Sikament NN)with an average compressive strength of 1.6MPa.3.4Crack Analysis of Test ObjectsThe following are some of the results of the cracking pattern of 28-day-old cylindrical specimens can be seen in Fig.3and Table 5.Based on Table 5.it can be seen that the average crack pattern for variations 1to 4is type 2.Crack pattern type 2is a crack pattern starting from the top surface but not reaching the bottom surface of the specimen.Cracking pattern type 1to type 5is a well-defined pattern and the specimen has reached its compressive capacity limit.[9].Utilization of Silica Sand and Gravel from Indarung Limestone Waste 4530.751.15 1.151.61.550.20.40.60.811.21.41.61.812345F l e x u r a l s t r e n g t h (M P a )Beam variaƟonFig.2.Concrete flexuralstrengthFig.3.Crack pattern of cylinderThe crack pattern of the beam test specimens during the flexural test for variations 1,2and 3is type 1where the crack is at 1/3of the center span,while variations 2and 4are type 2where the crack is outside 1/3of the center span and the fracture line is at <5%of the span illustrated as in Fig.4.The crack pattern for type 1and type 2flexural strength values can be used.[8].The role of silica sand and gravel can be seen in increasing the compressive strength of normal concrete after the addition of silica material,it also impact in resisting cracking in cylindrical test specimens can be seen from the shape of the collapse which is increasingly conical upwards along with the increase in the variation in the use of silica aggregate material.This proves that the silica aggregate material present in concrete inhibits the crack path that occurs where the greater the variation in the addition of silica aggregate material,the shorter the resulting crack path.While in the beam test specimens the resulting crack pattern is a flexural crack,where the flexural crack produced extends along with the increase in the variation of silica aggregate material.454 E.Suhelmidawati et al.Table5.Crack pattern of cylinder after28daysVariation No Sampel Crack type Average11Type2Type22Type23Type321Type2Type22Type23Type231Type3Type22Type23Type241Type2Type22Type23Type251Type3Type32Type23Type3Fig.4.Example of crack pattern of beam specimens3.5Design of Rigid Pavement ThicknessIn this study,rigid pavement thickness planning was carried out using the2017Road Pavement Design Manual(MDP)method,with the following data required:Utilization of Silica Sand and Gravel from Indarung Limestone Waste455Table6.Age PlanPavement Type Pavement Element AgeFlexible pavement Asphalt coating and granular coating(2)20Road foundationAll pavements for areas where coating is not possibleoverlay,such as:urban roads,underpasses,Cement Treated Based(CTB)40Rigid Pavement Upper foundation layer,subbase layer,cement concretelayer,and road foundations.Uncovered Road All elements(including road foundation)Minimum10 Source:Manual Desain Perkerasan Jalan2017Table7.Traffic growth rate factor(i)(%)Jawa Sumatera Kalimantan Rata-rataIndonesia Arteries and cities 4.80 4.83 5.14 4.75rural collector 3.50 3.50 3.50 3.50Village Road 1.00 1.00 1.00 1.00Source:Manual Desain Perkerasan Jalan20171.The road consists of4lanes2divided directions(4/2D)2.Type of road based on function,namely Collector roads with Secondary class andIIA.3.6Determining the Plan LifeDetermination of the plan life for road pavement in MDP2017[10].Depends on the type of pavement to be used in accordance with the Pavement Plan Life,the plan life is 40years(Table6)with the start of operation in2024.3.7Determine Traffic Growth Factor(I)Determining the traffic growth factor(i)can be determined based on the rigid pavement table for roads with heavy traffic loads reviewed,namely urban roads located on the island of Sumatra with traffic growth of4.83%(Table7).3.8Determining Direction and Lane Distribution FactorsThe directional distribution factor(DD)is generally used0.50except in locations where the number of commercial vehicles tends to be higher in one particular direction.Deter-mination of the value of the lane distribution factor can be determined based on the456 E.Suhelmidawati et al.ne Distribution Factor(DL)Number of lanes every direction Commercial vehicle on design lane(%of commercial vehiclepopulation)1100280360450Table9.Number of Vehicles Fly Over Design-Anak Aia IntersectionTime Vehicle Class2345a5b6a6b7a7b7c 17.00–17.1510411500018900 17.15–17.3010401310410400 17.30–17.4513201200210500 17.45–18.009012020113701 Total430260307512501Table10.Number of Vehicles Design of Anak Aia Intersection-Fly OverTime Vehicle Class2345a5b6a6b7a7b7c 17.00–17.15790600215400 17.15–17.30772140005700 17.30–17.4592160019400 17.45–18.00850500110200 Total333331004391700Traffic Growth Rate Factor Table(i)On the road under review there are2lanes per direction with80%lane distribution(Table8).3.9Average Daily LHRCalculation offlexible pavement thickness using vehicle data on Sunday,February20, 2022at17.00–18.00.Motorcycles and light vehicles are not taken into account in the MDP2017method planning Table9and Table10.Utilization of Silica Sand and Gravel from Indarung Limestone Waste457Table11.Recapitulation of LHR Calculation of Each Vehicle TypeTransportation type Vehicle Class LHR(vehicle/day/2way)Mobil Kendaraan29583Oplet,Mini Bus363Pick-up41011Bus Kecil5a38Bus Besar5b0Truk2Sumbu4Roda6a138Truk2Sumbu6Roda6b1189Truk3Sumbu7a525Truk Gandeng7b0Truk Semi Trailer7c13Total12560Table12.Recapitulation of Cumulative Value of Commercial Vehicle Axis GroupVehicle Types LHR(2ways)2022LHR2024LHR2027VDF5FaktualVDF5NormalESA5(‘24-’26)ESA5(‘27-’44)MobilPenumpangdankendaraanringanlainnya106571171113492----5B38424811006A1381521750,50,5226733531456B1189130715057,44,6289113027992612 7A52557766518,47,4317417719883588 7B000--007C13141629,59,6126014638731CESA5621399348868077CESA52024–204455082070The following is a recapitulation of the calculation of vehicle LHR in units of vehicles/day/direction:Based on Table11,it can be seen that the number of vehicles that are widely traveled on the Jalan Anak Aia-fly over intersection is Car Vehicles with a total LHR of9583458 E.Suhelmidawati et al.vehicles/day/direction and the total LHR for the2017MDP method rigid pavement is 12560vehicles/day/direction.3.10Determining the Volume of the Commercial Axis Vehicle Group Cumulative load calculation(ESA5)for20years(2024–2044)using VDF Table Lane Distribution Factor(DL)and4.83%traffic growth.The following is an example of ESA5calculation for vehicle type6A:─Lintas harian rata-rata 2 arah 2022= 138─Pertumbuhan lalu lintas = 4.83%─Nilai DD = 0.50.8─NilaiDL ==0.5(Table Faktor Distribusi Lajur (DL))Faktual─VDF─VDF Normal = 0.5 (Table Faktor Distribusi Lajur (DL))─R(24-26) = 2.048─R(27-44) = 27.69─LHR 2024 = LHR 2 arah 2021 x (1 + 0.0483)3= 138 x (1 + 0.0483)3=152─LHR 2026 = LHR 2 arah 2021 x (1 + 0.0483)5= 138 x (1 + 0.0483)5= 175─ESA5(24-26) = LHR 2024 x VDF5 Faktual x 365 x DD x DLx R= 159 x 0.5 x 365 x 0.5 x 0.8 x 2.048= 2.26E+04─ESA5(27-44) = LHR 2026 x VDF5 Normal x 365 x DD x DLRx= 175 x 0.5 x 365 x 0.5 x 0.8 x 27.69= 3.53E+05The recapitulation of the cumulative value of the commercial vehicle axis group can be seen in Table12.Based on Table12,the cumulative value of the2024–2044commercial vehicle axis group is55.08E+06ESAL.3.11Determining the Road Foundation StructureBased on the calculation of the CBR value with2methods,the results obtained with the graphical method are7.2%and the analytical method is4.81%,the smallest CBR value used in planning is the analytical method of4.81%.Based on the Lane Distribution Factor Table,the minimum road foundation design is obtained for CBR4.81%,then the subgrade strength class is SG.4,which requires subgrade improvement with a minimum repair thickness of200mm.Utilization of Silica Sand and Gravel from Indarung Limestone Waste459 3.12Define Pavement Layer Structure TableThe cumulative design commercial vehicle axis group is55.08E+06ESAL,based on the Terminal Serviceability Index Table,theflexural pavement thickness is obtained in the following table:1.Plan life:20years(2024–2044)2.Thickness of concrete slab:275mm3.Thin concrete layer(LC):100mm4.Class A Foundation Layer:150mm4ConclusionBased on the results of research and planning that has been carried out,the following conclusions are obtained.1.The highest compressive strength value of concrete is obtained in the3rd concretevariation with a concrete mixture of100%Silica sand+Natural gravel+Sikament NN with a value of41.14MPa.For the optimumflexural strength value obtained in the4th concrete mixture(100%natural Sand+Silica Gravel+Sikament NN) with a value of1.6MPa.Based on these results in road planning,we use the4th concrete variation as a variation that will be applied on the basis of its optimum flexural strength value and also with a compressive strength value that exceeds the compressive strength of the plan,namely32.36MPa.2.Planning of rigid pavement on Jalan Simpang Anak Aia-Fly Over MinangkabauInternational Airport STA22+800s/d STA22+800using MDP2017method obtained pavement thickness of27.5cm.So it can be concluded that the results of this research and planning of rigid pavement thickness can be used as an alternative to rigid pavement and also reduce mining waste in the form of silica aggregate material in the environment.Acknowledgments.We,the author would like to thank to Politeknik Negeri Padang for funding this research with DIPA funds for the2022Fiscal Year and the Field Team who have helped a lot both during preparation materials,concrete mixing,until material testing and paper writing. References1.Adi,A.S.Aanalysis Of Use Of Silica Sand As Replacement Of Fine Aggregate On ConcreteMixture.1.(2018).2.Nadia,&Fauzi,A.Pengaruh Kadar Silika Pada Agregat Halus Campuran Beton TerhadapPeningkatan Kuat Tekan.Kontruksia,3(1),35–43.(2011).3.Statements,B.,&Size,T.Standard Test Method for Materials Finer than75-µm(No.200)Sieve in Mineral Aggregates by Washing.14(200),3p.(1995).460 E.Suhelmidawati et al.4.Standard,T.O.Standard Test Method for Density(Unit Weight),Yield,and Air Content(Gravimetric).1–6.https:///10.1520/C0138.(2019).5.ASTM C494/C494M-05Standard Specification for Chemical Admixtures for Concrete.(n.d.).5–7.6.Test,C.C.,&Statements,B.(n.d.).Standard Test Method for Slump of Hydraulic-CementConcrete1.1–4.https:///10.1520/C01437.Test,C.C.,Drilled,T.,Test,C.C.,&Statements,B.ASTM C39/C39M–01.Standard TestMethod for Compressive Strength of Cylindrical Concrete Specimens.3–9.https:///10.1520/C0039.(2014).8.ASTM.Astm C78/C78M-18:Standard Test Method for Flexural Strength of Concrete(UsingSimple Beam with Third-Point Loading)ASTM A,04.02,1–3.(2002).9.Ag-,C.,Machine,A.,&Units,M.Standard specification for concrete aggregates(ASTMC33/C33M-13).https:///10.1520/C0033.(2013).10.Direktorat Jendral Bina Marga.Spesifikasi Teknis Jalan Bebas Hambatan dan Jalan Tol.Kementerian Pekerjaan Umum dan Perumahan Rakyat.(2017).Open Access This chapter is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0International License(/licenses/by-nc/4.0/), which permits any noncommercial use,sharing,adaptation,distribution and reproduction in any medium or format,as long as you give appropriate credit to the original author(s)and the source, provide a link to the Creative Commons license and indicate if changes were made.The images or other third party material in this chapter are included in the chapter’s Creative Commons license,unless indicated otherwise in a credit line to the material.If material is not included in the chapter’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use,you will need to obtain permission directly from the copyright holder.。
岩石三轴压缩实验的强度特性及应用_李亚林
４期
李亚林等：岩石三轴压缩实验的强度特性及应用
７５
１．１ 摩尔强度理论简介 １９００ 年，由德国工程师摩尔（Ｍｏｈｒ）创立的强度理论，被后人称为摩尔强度理论。 以广州某重大工程基底中风化泥质粉砂岩的三轴强度包络线图（图 １）为例，对摩尔强
２００６， ２６（３）：４４－ ４６．
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ＬＩ Ｙａｌｉｎ， ＧＡＯ Ｌｅｉ， ＧＵＯ Ｄｅｓｈｕｎ， ＹＡＮ Ｙｕｄｉｎｇ
２００６， ２６（１）：１１－ １７． ［４］ Ｙａｎ Ｙｕｄｉｎｇ， Ｌｉ Ｙａｌｉｎ， Ｚｈａｎｇ Ｚｈｕａｎ ｅｔ ａｉ， Ｅｘｐｅｒｉｍｅｎｔ ｏｎ Ｈｙｄｒａｕｌｉｃ Ｆｒａｃｔｕｒｉｎｇ ｉｎ Ｒｏｃｋ ａｎｄ Ｉｎｄｕｃｅｄ Ｅａｒｔｈｑｕａｋｅ，
Ｅａｒｔｔｈｑｕａｋｅ Ｒｅｓｅａｒｃｈ ｉｎ Ｃｈｉｎａ，２００５， １９（４）：３５４￣３７０． ［５］ 姜慧，胡聿贤，赵凤新，等． 用随机模拟方法研究设定地震的地面运动参数 ［Ｊ］ ． 地震工程与工程震动，
图 １ 广州某工程基底中风化泥质粉砂岩的三轴强度包络线 Ｆｉｇ．１ Ｔｒｉａｘｉａｌ ｓｔｒｅｎｇｔｈ ｅｎｖｅｌｏｐｅｓ ｏｆ ｔｈｅ ｍｏｄｅｒａｔｅ－ ｅｆｆｌｏｒｅｓｃｅｎｔ ａｒｇｉｌｌａｃｅｏｕｓ ｓｉｌｔｓｔｏｎｅ ｓａｍｐｌｅ
１．２ 岩石三轴强度的特点 表 １ 为中风化泥质粉砂岩的部分三轴实验结果和相关数据。结合图 １ 和表 １ 阐述岩石
（２）由三轴抗压强度实验可得到理论破裂角 θ，此 θ即为破裂面的倾角。可为工程设计 者提供应作重点应力分析的剖面。如岩体内存在薄弱结构面，此薄弱面的倾角若与 θ相近，
3种砂岩变形与强度特征对比分析
㊀第45卷第4期煤㊀㊀炭㊀㊀学㊀㊀报Vol.45㊀No.4㊀㊀2020年4月JOURNAL OF CHINA COAL SOCIETYApr.㊀2020㊀移动阅读王云飞,宿辉,王立平,等.3种砂岩变形与强度特征对比分析[J].煤炭学报,2020,45(4):1367-1374.doi:10.13225/ki.jccs.2019.0418WANG Yunfei,SU Hui,WANG Liping,et al.Study on the difference of deformation and strength characteristics of three kinds of sandstone[J].Journal of China Coal Society,2020,45(4):1367-1374.doi:10.13225/ki.jccs.2019.04183种砂岩变形与强度特征对比分析王云飞1,宿㊀辉2,王立平1,焦华喆1,李㊀震1(1.河南理工大学土木工程学院,河南焦作㊀454000;2.河北工程大学水利水电学院,河北邯郸㊀056002)摘㊀要:为了明确3种砂岩力学行为的差异及产生差异的内在原因,利用RMT -150B 岩石力学试验系统对3种砂岩进行了三轴试验,分析了3种砂岩的变形㊁强度和破坏特征㊂试验结果表明:白砂岩和红砂岩的屈服特征明显,塑性变形显著,随着围压的增大,屈服段逐渐增长,黄砂岩屈服特性不明显且受围压影响较小;砂岩的单轴抗压强度越高,围压对其强度的提高效应越显著,其中黄砂岩抗压强度受围压影响提高显著;砂岩弹性模量和变形模量受围压影响的提高程度与低围压时弹性模量和变形模量的大小成正比,且围压对黄砂岩弹性模量和变形模量的影响显著;3种砂岩的内摩擦角差值较大,而黏聚力相差较小,因而可见3种砂岩强度的差异主要是内摩擦角的不同导致的;砂岩的巴西劈裂强度为单轴抗压强度的3．5%~5．8%㊂3种砂岩的围压影响系数随围压增加整体按负指数关系减小,20MPa 是围压影响系数减小快慢的转折点;通过试验结果分析3种强度准则,指出幂函数Mohr 强度准则能更好的反应不同围压岩石强度的非线性特征;白砂岩发生典型的缓倾角剪切破坏,破裂面为平面,红砂岩和黄砂岩在低围压下发生张剪复合破坏,在高围压时发生陡倾角剪切破坏,红砂岩的破裂面为锥面,黄砂岩的破裂面为高低不平的起伏面㊂关键词:砂岩;强度;变形;屈服准则;破坏特征中图分类号:TD315㊀㊀㊀文献标志码:A㊀㊀㊀文章编号:0253-9993(2020)04-1367-08收稿日期:2019-04-04㊀㊀修回日期:2019-04-24㊀㊀责任编辑:陶㊀赛㊀㊀基金项目:国家自然科学基金资助项目(U1604142);河北省自然科学基金面上资助项目(E2018402263);河南理工大学青年骨干教师资助项目(2016XQG -10)㊀㊀作者简介:王云飞(1978 ),男,内蒙古乌盟人,副教授㊂E -mail:wyf_ustb@126．com ㊀㊀通讯作者:王立平(1979 ),男,山西阳泉人,讲师,博士㊂E -mail:wlp1116@Study on the difference of deformation and strength characteristics ofthree kinds of sandstoneWANG Yunfei 1,SU Hui 2,WANG Liping 1,JIAO Huazhe 1,LI Zhen 1(1.School of Civil Engineering ,Henan Polytechnic University ,Jiaozuo ㊀454000,China ;2.School of Water Conservancy and Hydroelectric Power ,Hebei Univer-sity of Engineering ,Handan ㊀056002,China )Abstract :In order to clarify the differences and the intrinsic causes of mechanical behavior of three kinds of sand-stone,the conventional triaxial test for three kinds of sandstone were carried out by RMT -150B rock mechanics test system,and the deformation,strength and failure characteristics of three kinds of sandstone were analyzed.The resultsshowed that the yield characteristics of white sandstone and red sandstone were obvious,and the plastic deformation were remarkable,with the increase of confining pressure,the yield stage increased gradually,while the yield character-istic of yellow sandstone was not obvious and less affected by confining pressure.The higher the uniaxial compressivestrength of sandstone is,the more significant the effect of confining pressure on its strength is,and the effect of confi-煤㊀㊀炭㊀㊀学㊀㊀报2020年第45卷ning pressure on the compressive strength of yellow sandstone was remarkable.The improvement degree of elastic mod-ulus and deformation modulus of sandstone influenced by confining pressure is proportional to the magnitude of elastic modulus and deformation modulus under lower confining pressure,and the influence of confining pressure on elastic modulus and deformation modulus of yellow sandstone was significant.The difference of internal friction angle between the three kinds of sandstone was large,while the difference of cohesion was small.Therefore,the strength difference of the three kinds of sandstone is mainly caused by the difference of internal friction angle.Brazilian splitting strength of sandstone is3.5%-5.8%of uniaxial compressive strength.The confining pressure influence coefficient of the three kinds of sandstone decreased in a negative exponential relationship with the increase of confining pressure,and20MPa is the turning point of speed change of the confining pressure influence coefficient.Three kinds of strength criteria were analyzed through the experimental data,it is pointed out that the strength function of Mohr strength criterion can better reflect the non-linear characteristics of rock strength under different confining pressures.The typical slow dip angle shear failure occurs in white sandstone,and its fracture plane is plane.the tension-shear composite failure of red sand-stone and yellow sandstone occurs under lower confining pressure,and steep dip angle shear failure occurs under high-er confining pressure,the fracture plane of red sandstone is conical,while that of yellow sandstone is uneven.Key words:sandstone;strength;deformation;strength criterion;failure characteristics㊀㊀岩石单轴㊁常规三轴是测定岩石力学参数的基础性实验,通过实验获得相关力学参数,建立岩石力学理论并解决岩体工程问题㊂力学参数的科学合理选择对工程岩体的稳定至关重要,故国内外学者从多角度对岩石力学性质进行了研究㊂主要集中在以下方面:①在岩石的加㊁卸荷力学特性方面,如大理岩应力路径和荷载速率[1-2]㊁卸荷方向[3]对强度和破坏特征的影响,真三轴岩石卸荷力学特性的研究[4],煤-岩组合强度[5],轴向㊁侧向同时卸荷砂岩强度特性[6],脆性硬质红砂岩加㊁卸载强度特征[7]等㊂②在损伤特性及强度影响因素关联性分析方面,有表面裂纹量化参数与应力状态之间的关系[8],花岗岩压缩变形各阶段的破裂演化机制[9],砂岩在酸性环境干湿循环作用下强度的劣化规律[10],砂岩抗拉强度㊁破坏特征㊁能量参数和劈裂面微观形貌变化规律及相关性[11],砂岩裂纹演化特征[12]㊁各向异性对砂岩强度的影响[13],纵向裂隙对砂岩单轴强度的劣化特征[14],大理岩损伤破坏声发射特征[15],顶板砂岩声发射特性及力学行为[16]㊂微结构量化参数和无侧限抗压强度关联性分析[17]等㊂③在强度准则方面,有三轴强度准则[18],扩展HB准则[19],节理岩体强度准则[20],完整岩石的非线性强度[21],对常用强度准则与判据的试验分析验证[22-24],多轴应力状态下预测岩体破坏的新判据[25],人工神经网络多轴强度模型[26]等㊂综上可见,国内外学者对各种岩石的力学和变形特性进行了大量研究,但对不同种类砂岩之间力学变形特性差异的对比研究还不够深入(如不同种类砂岩强度差异内在原因分析等)㊂鉴于此,笔者开展了相关分析,研究成果可为地下工程选址㊁围岩稳定性分析提供参考依据㊂1㊀砂岩特性与试验方法试验砂岩采自四川省内江市,岩样经过钻㊁磨工序加工成尺寸约ϕ50mmˑ100mm的圆柱形标准试件,如图1所示,试件误差满足‘工程岩体试验方法标准“要求㊂为了保证试验岩样的均质性通过波速测定进行了试样的筛选,3种砂岩的平均密度和纵波波速见表1㊂图1㊀3种砂岩试样Fig．1㊀Three kinds of sandstone samples表1㊀3种砂岩的平均密度与纵波波速Table1㊀Density and longitudinal wave velocity of threekinds of sandstone岩性平均密度/(kg㊃m-3)纵波波速/(km㊃s-1)白砂岩2417．762．4825黄砂岩2347．672．7189红砂岩2401．252．94848631第4期王云飞等:3种砂岩变形与强度特征对比分析㊀㊀试验采用RMT-150B岩石力学试验系统,进行了3种砂岩的单轴㊁常规三轴压缩和巴西劈裂试验㊂利用1000kN力传感器测量垂直荷载,5mm 位移传感器测量试件垂直变形㊂单轴压缩试验每种岩石取3个试样,试验结果取平均值,巴西劈裂试验每种岩石取5个试样,试验结果取平均值㊂加载方式采用位移控制,轴向加载速率为0．002mm/ s,围压加载速率为0．1MPa/s㊂常规三轴加载初期采用静水压力条件加载至预定围压,然后伺服控制围压,轴向采用0．002mm/s的速率施加轴向压力直至试样破坏㊂2㊀砂岩试验结果分析2．1㊀砂岩应力应变特征图2为砂岩常规三轴压缩试验的应力-应变曲线,压缩曲线经历压密㊁弹性㊁屈服和破坏4个阶段㊂在压密和弹性变形阶段3种砂岩的应力应变曲线形态基本相同㊂在屈服阶段差异明显,白砂岩屈服阶段最显著,其次是红砂岩,黄砂岩的屈服段最短㊂随着围压的增大,白砂岩和红砂岩的屈服特性更加显著,屈服段逐渐增长,出现显著的塑性变形,峰值应变增加,逐渐由脆性向延性转化,而黄砂岩的屈服特性受围压影响较小㊂在破坏阶段,白砂岩峰值后应力跌落速度相对缓慢,红砂岩和黄砂岩的蜂后应力迅速降低,表明黄砂岩和红砂岩破坏时的能量释放要比白砂岩剧烈㊂屈服阶段主要发生不可恢复的塑性变形,可见白砂岩和红砂岩的塑性变形能力比黄砂岩强㊂塑性变形主要是岩样内部形成微裂隙,在外力作用下颗粒相对滑移产生的,因而从微观角度分析,白砂岩和红砂岩承受损伤变形能力更强㊂故可知,白砂岩承受变形能力最强延性最好,红砂岩居中,而黄砂岩承受变形能力最差脆性最强㊂表2给出3种砂岩的弹性模量E㊁变形模量E50和峰值应变值㊂弹性模量为应力应变曲线近似直线段(30%~70%峰值强度)斜率,变形模量为50%峰值强度点与原点连线斜率,峰值应变为峰值点处对应轴向应变值㊂随着围压的增大,3种砂岩的弹性模量和变形模量也在增大(只有白砂岩40MPa时例外)㊂围压从5MPa增加到40MPa,白砂岩㊁红砂岩和黄砂岩的弹性模量增幅分别为22%,38%和60%,变形模量的增幅分别为74%,90%和125%㊂可见围压对黄砂岩弹性模量和变形模量的影响最显著,围压对白砂岩弹性模量和变形模量的影响相对最小㊂从图2㊀3种砂岩不同围压应力应变曲线Fig．2㊀Stress-strain curves of three kinds of sandstone underdifferent confining pressure5MPa到40MPa,白砂岩㊁红砂岩和黄砂岩变形模量增幅与弹性模量增幅之比分别为3．36,2．37和2．08,表明变形模量相对弹性模量受围压影响增加更快㊂以20MPa为例,黄砂岩㊁红砂岩相对白砂岩的弹性模量比值分别为1．34和1．19,变形模量的比值分别为1．25和1．24,可见3种砂岩弹性模量和变形模量由高到低的顺序为黄砂岩㊁红砂岩和白砂岩㊂综合分析可见,砂岩弹性模量和变形模量受围压影响的提高程度与低围压时弹性模量和变形模量的大小成正比㊂随着围压的增大,3种砂岩的峰值应变值总体在增加㊂围压从5MPa增加到40MPa,白砂岩㊁红砂岩9631煤㊀㊀炭㊀㊀学㊀㊀报2020年第45卷和黄砂岩的峰值应变值增幅分别为67%,49%和43%㊂黄砂岩相对白砂岩和红砂岩,5MPa时的峰值应变最大,40MPa时的峰值应变却最小㊂表明3种砂岩受围压影响的变形大小顺序为:白砂岩>红砂岩>黄砂岩㊂表2㊀3种砂岩的变形特征Table2㊀Deformation characteristics of three kinds ofsandstone岩性σ3/MPa E/GPa E50/GPaε0/10-3513．689．739．641015．2512．2410．13白砂岩2016．3114．4211．373017．4417．7213．814016．7116．9016．07516．4812．439．801018．2815．1811．01红砂岩2019．4117．8713．173020．2920．5614．354022．8123．5914．61517．8711．8010．081021．6915．5810．25黄砂岩2021．8617．9912．823028．3124．9611．824028．6126．5314．37㊀㊀图3为3种砂岩破坏时的最大主应力σ1与围压的关系,并用Coulomb强度准则拟合为σ1=kσ3+m(1)其中,m为砂岩拟合回归获得的单轴抗压强度;k为围压对砂岩承载能力的影响系数㊂最大主应力与围压的关系又可表示为σ1=1+sinφ1-sinφσ3+2c cosφ1-sinφ(2)㊀㊀进一步获得砂岩内摩擦角φ和黏聚力c与k和m的关系为φ=arcsin[(k-1)/(k+1)](3)c=m(1-sinφ)/(2cosφ)(4)㊀㊀白砂岩㊁红砂岩和黄砂岩拟合获得的参数和对应的黏聚力与内摩擦角结果见表3㊂图3采用3个单轴抗压强度平均值与5个不同围压强度进行回归㊂由图3可知,Coulomb强度准则获得单轴抗压强度(m)都高于实际砂岩的单轴抗压强度值,主要原因在于单轴试验岩样破坏是张剪复合破坏,强度较低,而由不同围压回归获得的单轴抗压强度是理想单轴剪切破坏强度,相应较高㊂由表3可知,理想单轴剪切破坏强度,黄砂岩最大,红砂岩次之,白砂岩最小㊂图3㊀3种砂岩峰值强度与围压的关系Fig．3㊀Relationship of sandstone peak strength and confiningpressures of thres rinds of sandstone表3㊀3种砂岩的强度参数Table3㊀Strength parameters of three kinds of sandstone 岩性k m/MPaφ/(ʎ)黏聚力c/MPa 白砂岩4．1675．5637．7618．53红砂岩5．2991．0143．0019．79黄砂岩6．8394．8948．1318．15㊀㊀3种岩石的内摩擦角:黄砂岩>红砂岩>白砂岩,黄砂岩和红砂岩的内摩擦角分别是白砂岩内摩擦角的1．28倍和1．14倍㊂3种砂岩的黏聚力相差较小,最大黏聚力(红砂岩)仅为最小黏聚力(黄砂岩)的1．09倍㊂砂岩的强度是由黏聚力和内摩擦角共同提供,因而从分析可见,3种砂岩强度的差异主要是由于内摩擦角的不同导致的㊂2．2㊀围压影响系数为了描述围压对3种砂岩强度的影响差异,定义围压影响系数η为η=σ1-σcσ3(5)式中,σc为砂岩单轴抗压强度㊂利用3种砂岩三轴试验数据,按照式(5)计算出围压影响系数,并将围压影响系数随围压的变化关系绘于图4㊂由图4可知,3种砂岩的围压影响系数变化规律一致,随着围压的增加整体都按负指数关系减小㊂相同围压下,白砂岩的围压影响系数小,红砂岩的居中,而黄砂岩的最大㊂较低围压下围压影响系数减小显著,围压较大时围压影响系数减小缓慢,由图4可知, 20MPa是3种砂岩围压影响系数减小快慢的明显转折点㊂这表明对于3种砂岩,围压小于20MPa时,围0731第4期王云飞等:3种砂岩变形与强度特征对比分析图4㊀砂岩围压影响系数随围压的变化Fig．4㊀Variation of confining pressure effect coefficientof sandstone with confining pressure压增大对强度的提高效应显著,围压大于20MPa 时,增大围压对强度的提高效应减小并逐渐趋于定值㊂白砂岩围压影响系数趋于4．22,红砂岩的趋于5．37,黄砂岩的趋于7．02,可见3种砂岩中围压对黄砂岩的强度提高效应显著㊂2．3㊀拉压强度关系3种砂岩的巴西劈裂强度㊁单轴抗压强度和不同围压强度值及强度之间的比值关系见表4,表4中的比值是以单轴抗压强度为基准,其他强度为单轴抗压强度的倍数㊂由表4可以看出,巴西劈裂强度远低于单轴抗压强度,3种砂岩的巴西劈裂强度为单轴抗压强度的3．5%~5．8%㊂黄砂岩的巴西劈裂强度最低而红砂岩的最高,但黄砂岩的单轴抗压强度在3种砂岩中却是最高的,出现这一现象的主要原因在于白砂岩和红砂岩的均质性较好,而黄砂岩的纹理较明显,受其纹理影响导致巴西劈裂强度较低㊂围压对3种砂岩的强度影响顺序为:黄砂岩㊁红砂岩和白砂岩,当围压达到40MPa 时,黄砂岩㊁红砂岩和白砂岩的强度分别是单轴抗压强度的4．8467倍㊁4．0153倍和3．6854倍㊂同一种砂岩,随着围压的增加强度提高效应会减弱㊂进一步的分析发现,砂岩的单轴抗压强度越高,围压对其强度的提高效应越明显㊂表4㊀3种砂岩的强度比值关系Table 4㊀Strength ratio relationship of three kinds of sandstone项目白砂岩强度/MPa 比值黄砂岩强度/MPa 比值红砂岩强度/MPa 比值巴西劈裂强度2．92280．04602．63900．03514．39840．0587单轴抗压强度63．56341．000075．10441．000074．99981．00005MPa 围压强度99．81421．5703137．52821．8312123．62861．648410MPa 围压强度124．96881．9661179．66972．3923156．42232．085620MPa 围压强度162．96872．5639232．62943．0974202．91712．705630MPa 围压强度204．59753．2188297．84473．9657242．26753．230240MPa 围压强度234．25723．6854364．00724．8467301．15024．01532．4㊀强度准则分析根据白砂岩㊁红砂岩和黄砂岩的三轴试验结果,在σ-τ坐标系中绘制不同岩性的应力圆,并拟合建立线性㊁抛物线和幂函数3种Mohr 强度包络线(图5),要求3种包络线在正应力为0时,切应力都为相应岩石的黏聚力㊂白砂岩幂函数Mohr 强度准则为τ=0．94σ0．952+18．53㊀㊀红砂岩幂函数Mohr 强度准则为τ=1．10σ0．959+19．79㊀㊀黄砂岩幂函数Mohr 强度准则为τ=1．27σ0．968+18．15㊀㊀由图5可以看出,当统一满足正应力为0,切应力为黏聚力的条件时,抛物线型Mohr 强度包线偏离实际值较大,在高应力区理论值比实际值偏小很多,不能反映真实强度㊂线性Mohr 强度包线和幂函数Mohr 强度包线基本都能和应力圆很好相切,但幂函数Mohr 强度包线相对线性Mohr 强度包线吻合程度更好,且在高应力区线性Mohr 强度包线相对幂函数Mohr 强度包线偏高,研究表明Mohr 强度包线并非是线性的而是按非线性规律变化,因此采用幂函数型Mohr 强度准则能更好的确定岩石强度,符合工程实际㊂2．5㊀破坏特征3种砂岩在不同围压下的破坏形式如图6所示㊂由图6可见,砂岩试样有两种破坏形式:剪切破坏和张剪复合破坏㊂剪切破坏根据破裂角度可以分为缓倾角和陡倾角剪切破坏两种形式,对于尺寸为1731煤㊀㊀炭㊀㊀学㊀㊀报2020年第45卷图5㊀3种砂岩常规三轴试验强度包络线Fig．5㊀Strength envelope curves of conventional triaxial testof thres kinds of sandstone50mmˑ100mm的试样而言,对角截面的倾角为63．43ʎ,当实际破裂角小于该值时称为缓倾角破坏,大于该值时称为陡倾角剪切破坏㊂白砂岩发生典型的缓倾角剪切破坏,红砂岩和黄砂岩既有张剪复合破坏又有陡倾角剪切破坏㊂白砂岩破裂面单一,破裂面近似平面,如图7所示,破坏时沿单一剪切平面发生滑移,个别试样的水平裂纹是由于滑移过程围压挤压作用形成,在5~40MPa围压条件下,白砂岩均发生剪切破坏㊂在5~10MPa围压条件下,红砂岩和黄砂岩发生张剪复合破坏,除了有剪切裂纹外,还有平行于轴向的劈裂裂纹,由于黄砂岩的主控破裂面接近直立,所以张拉劈裂效应比红砂岩更加显著㊂在20~40MPa围压条件下,红砂岩和黄砂岩发生陡倾角剪切破坏,破裂以主控剪切面控制,红砂岩破坏面形态为锥面而黄砂岩破坏面为高低不平的起伏面㊂图6㊀3种砂岩的破坏特征Fig．6㊀Failure samples of thres kinds of sandstone表5给出了根据Coulomb强度准则预测的破裂角(θ=45ʎ+φ/2),Coulomb破裂角是将岩土体作为均质体导出的,且与围压没有关系,理论破裂角都在实际破裂角范围之内㊂白砂岩的实际破裂角为57ʎ~ 63ʎ,红砂岩的实际破裂角为58ʎ~74ʎ,黄砂岩的实际破裂角为63ʎ~76ʎ,可见3种砂岩的实际破裂角比较离散,这是由于砂岩不均质性和内部缺陷的存在,以及试样受端部约束的影响,导致破裂角的波动和随机性㊂尽管试样的实际破裂角有些离散,但就总体变化趋势而言,破裂角随围压的增加有减小的趋势㊂表5㊀3种砂岩破裂角Table5㊀Fracture angle of three kinds of sandstone岩性φ/(ʎ)理论破裂角θ/(ʎ)实际破裂角θᶄ/(ʎ)白砂岩37．7663．8857~63红砂岩43．0066．5058~74黄砂岩48．1369．0663~762731第4期王云飞等:3种砂岩变形与强度特征对比分析图7㊀3种砂岩典型破裂面形态Fig．7㊀Typical fracture surface form of three kindsof sandstone3㊀结㊀㊀论(1)随着围压的增大,白砂岩和红砂岩的屈服特性更加显著,屈服段逐渐增长,出现显著的塑性变形,而黄砂岩的屈服特性受围压影响较小㊂白砂岩峰值后应力降速度相对缓慢,红砂岩和黄砂岩的蜂后应力迅速降低㊂(2)围压对黄砂岩弹性模量和变形模量的影响最显著,对白砂岩弹性模量和变形模量的影响相对最小㊂砂岩弹性模量和变形模量受围压影响的提高程度与低围压时弹性模量和变形模量的大小成正比㊂(3)3种岩石的内摩擦角大小关系:黄砂岩>红砂岩>白砂岩,3种砂岩的黏聚力相差较小,故3种砂岩强度的差异主要是由于内摩擦角的不同导致的㊂(4)3种砂岩的围压影响系数随着围压的增加整体都按负指数关系减小㊂20MPa是3种砂岩围压影响系数减小快慢的明显转折点㊂(5)3种砂岩的巴西劈裂强度为单轴抗压强度的3．5%~5．8%㊂黄砂岩的巴西劈裂强度最低而红砂岩的最高㊂(6)通过3种砂岩试验结果分析线性Mohr强度㊁抛物线型和幂函数Mohr强度准则,指出幂函数Mohr强度准则能更好的反应岩石强度的非线性特征㊂(7)白砂岩发生典型的缓倾角剪切破坏,红砂岩和黄砂岩在5~10MPa围压下发生张剪复合破坏,在20~40MPa围压下发生陡倾角剪切破坏㊂参考文献(References):[1]㊀沙鹏,伍法权,常金源.大理岩真三轴卸载强度特征与破坏力学模式[J].岩石力学与工程学报,2018,37(9):2084-2092.SHA Peng,WU Faquan,CHANG Jinyuan.Unloading strength and failure pattern of marble under true triaxial test[J].Chinese Journal of Rock Mechanics and Engineering,2018,37(9):2084-2092.[2]㊀肖桃李,黄梅,李新平.考虑围压效应的深埋大理岩强度变形特性研究[J].地下空间与工程学报,2018,14(2):362-368.XIAO Taoli,HUANG Mei,LI Xinping.Research on strength and de-formation with Marble of deep rock mass considering confining pres-sure effect[J].Chinese Journal of Underground Space and Engineer-ing,2018,14(2):362-368.[3]㊀王璐,刘建锋,杨昊天,等.深埋大理岩卸载力学特性的实验研究[J].四川大学学报(工程科学版),2014,46(2):46-51.WANG Lu,LIU Jianfeng,YANG Haotian,et al.Experimental re-search on mechanical properties of deeply buried marble under un-loading conditions[J].Journal of Sichuan University(Engineer-ing Science Edition),2014,46(2):46-51.[4]㊀DU Kun,LI Xibing,LI Diyuan,et al.Failure properties of rocksin true triaxial unloading compressive test[J].Transactions of Non-ferrous Metals Society of China,2015,25(2):571-581. [5]㊀左建平,陈岩,张俊文,等.不同围压作用下煤-岩组合体破坏行为及强度特征[J].煤炭学报,2016,41(11):2706-2713.ZUO Jianping,CHEN Yan,ZHANG Junwen,et al.Failure behavior and strength characteristics of coal-rock combined body under differ-ent confining pressures[J].Journal of China Coal Society,2016, 41(11):2706-2713.[6]㊀韩铁林,师俊平,陈蕴生,等.轴㊁侧向同卸荷下砂岩力学特性影响的试验研究[J].力学学报,2016,48(3):936-943.HAN Tielin,SHI Junping,CHEN Yunsheng,et al.Experimental study on mechanics characteristics of sandstone under axial unloa-ding and radial unloading path[J].Chinese Journal of Theoretical and Applied Mechanics,2016,48(3):936-943.[7]㊀刘泉声,魏莱,雷广峰,等.砂岩裂纹起裂损伤强度及脆性参数演化试验研究[J].岩土工程学报,2018,40(10):1782-1789.LIU Quansheng,WEI Lai,LEI Guangfeng,et al.Experimental study on damage strength of crack initiation and evaluation of brittle pa-rameters of sandstone[J].Chinese Journal of Geotechnical Engineer-ing,2018,40(10):1782-1789.[8]㊀程立朝,许江,冯丹,等.岩石剪切破坏裂纹演化特征量化分析[J].岩石力学与工程学报,2015,34(1):31-39.3731煤㊀㊀炭㊀㊀学㊀㊀报2020年第45卷CHENG Lizhao,XU Jiang,FENG Dan,et al.Quantitative analysis on development of surface cracks of rocks upon shear failure[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(1): 31-39.[9]㊀赵星光,马利科,苏锐,等.北山深部花岗岩在压缩条件下的破裂演化与强度特性[J].岩石力学与工程学报,2014,33(S2): 3665-3675.ZHAO Xingguang,MA Like,SU Rui,et al.Fracture evolution and strength characteristics of Beishan deep Granite under compres-sion conditions[J].Chinese Journal of Rock Mechanics and Engi-neering,2014,33(S2):3665-3675.[10]㊀傅晏,袁文,刘新荣,等.酸性干湿循环作用下砂岩强度参数劣化规律[J].岩土力学,2018,39(9):3331-3339.FU Yan,YUAN Wen,LIU Xinrong,et al.Deterioration rules ofstrength parameters of sandstone under cyclical wetting and dryingin acid-based environment[J].Rock and Soil Mechanics,2018,39(9):3331-3339.[11]㊀邓华锋,王晨玺杰,李建林,等.加载速率对砂岩抗拉强度的影响机制[J].岩土力学,2018,39(S1):79-88.DENG Huafeng,WANG Chenxijie,LI Jianlin,et al.Influ-ence mechanism of loading rate on tensile strength of sandstone[J].Rock and Soil Mechanics,2018,39(S1):79-88. [12]㊀范鹏贤,李颖,赵跃堂,等.红砂岩卸载破坏强度特征试验研究[J].岩石力学与工程学报,2018,37(4):852-861.FAN Pengxian,LI Ying,ZHAO Yuetang,et al.Experimental studyon unloading failure strength of red sandstone[J].Chinese Journalof Rock Mechanics and Engineering,2018,37(4):852-861.[13]㊀SU Haijian,JING Hongwen,DU Mingrui,et al.Experimental inves-tigation on tensile strength and its loading rate effect of sandstoneafter high temperature treatment[J].Arabian Journal of Geosci-ences,2016,9(13):1-7.[14]㊀邓华锋,原先凡,李建林,等.饱水度对砂岩纵波波速及强度影响的试验研究[J].岩石力学与工程学报,2013,32(8):1625-1631.DENG Huafeng,YUAN Xianfan,LI Jianlin,et al.Experimental re-search on influence of saturation degree on sandstone longitudinalwave velocity and strength[J].Chinese Journal of Rock Mechanicsand Engineering,2013,32(8):1625-1631.[15]㊀YUAN Ruifu,SHI Bowen.Acoustic emission activity in directly te-nsile test on marble specimens and its tensile damage constitu-tive model[J].International Journal of Coal Science&Technology,2018,5(3):295-304.[16]㊀LI Huigui,LI Huamin.Mechanical properties and acoustic emis-sion characteristics of thick hard roof sandstone in Shendong coalfield[J].International Journal of Coal Science&Technology,2017,4(2):147-158.[17]㊀胡昕,洪宝宁,王伟,等.红砂岩强度特性的微结构试验研究[J].岩石力学与工程学报,2007,26(10):2141-2147.HU Xin,HONG Baoning,WANG Wei,et al.Experimental studyon microstructure of strength property of red sandstone[J].ChineseJournal of Rock Mechanics and Engineering,2007,26(10):2141-2147.[18]㊀YOU Mingqing.True triaxial strength criteria for rock[J].Interna-tional Journal of Rock Mechanics and Mining Sciences,2009,46(1):115-127.[19]㊀THOMAS Benz,RADU Schwab,REGINA A.Kauther,et al.AHoek-Brown criterion with intrinsic material strength factorization[J].International Journal of Rock Mechanics and Mining Sci-ences,2008,45(2):210-222.[20]㊀MAHENDRA Singh,BHAWANI Singh.Modified Mohr-Coulomb cr-iterion for non-linear triaxial and polyaxial strength of jointed rocks[J].International Journal of Rock Mechanics and Mining Sciences,2012,51:43-52.[21]㊀MAHENDRA Singh,ANIL Raj,BHAWANI Singh.Modified Mohr-Coulomb criterion for non-linear triaxial and polyaxial strength ofintact rocks[J].International Journal of Rock Mechanics and Min-ing Sciences,2011,48(4):546-555.[22]㊀SRIAPAI Tanapol,WALSRI Chaowarin,FUENKAJORN Kittitep.True-triaxial compressive strength of Maha Sarakham salt[J].In-ternational Journal of Rock Mechanics and Mining Sciences,2013,61:256-265.[23]㊀THOMAS Benz,RADU Schwab.A quantitative comparison of sixrock failure criteria[J].International Journal of Rock Mechanicsand Mining Sciences,2008,45(7):1176-1186. [24]㊀COLMENARES L B,ZOBACK M D.A statistical evaluation of in-tact rock failure criteria constrained by polyaxial test data forfive different rocks[J].International Journal of Rock Mechanicsand Mining Sciences,2002,39(6):695-729.[25]㊀RAFIAI Hosein.New empirical polyaxial criterion for rock strength[J].International Journal of Rock Mechanics and Mining Sci-ences,2011,48(6):922-931.[26]㊀RUKHAIYAR S,SAMADHIYA K.A polyaxial strength model forintact sandstone based on Artificial Neural Network[J].Interna-tional Journal of Rock Mechanics and Mining Sciences,2017,95:26-47.4731。
砒砂岩的三轴强度特性及微观结构研究
砒砂岩的三轴强度特性及微观结构研究作者：***来源：《人民黄河》2020年第03期摘要：为深入认识黄土高原地区砒砂岩干燥时坚如磐石、遇水后溃散泥化的微观机理，对不同粒度砒砂岩原状试样进行三轴剪切试验和CT扫描，获取不同粒度砒砂岩的强度特征和微结构特征，并分析了砒砂岩孔径的分布特点。
结果表明：砒砂岩试样的抗剪强度随粒度增大而降低，试样的峰值强度与固结围压存在良好的线性关系;由CT扫描得到的砒砂岩二维图像显示不同粒度试样的孔隙形态非常复杂;从三维重构模型的统计结果发现砒砂岩平均孔隙半径随砒砂岩粒径的增大而升高;砒砂岩的强度存在明显的粒度效应，砒砂岩粒度大小决定了内部孔隙的分布情况，进而引起强度的改变。
关键词：砒砂岩;粒度;孔隙;抗剪强度;三轴试验;CT扫描中图分类号：TU43;S157.1 文献标志码：Adoi：10.3969/j.issn.1000-1379.2020.03.014Study on Triaxial Strength Characteristics and Microstructure of the ArsenicSandstoneLIU Yaping（School of Architecture， Zhengzhou Shengda Economics and Management College，Zhengzhou 451191， China）Abstract：In order to further understand the microscopic mechanism of arsenic sandstone which is hard as rock in dry state and muddy in water， triaxial shear test and CT scan test were carried outfor obtaining the strength characteristics and microstructure characteristics of arsenic sandstones in different grain grades. The results show that the strength of sandstone sample decreases with the increase of grain size in triaxial shear test. There is a good linear relationship between peak strength and consolidation confining pressure. The two-dimensional and three-dimensional reconstruction images of sandstone samples can be obtained by CT scanning. It is found that the porosity and average pore radius of sandstone increase with the increase of particle size. The strength of sandstone has obvious “particle size effect”. The smaller the particle size of arsenic sandstone， the smaller its porosity， and thus the higher the strength.Key words： arsenic sandstone; particle size; pore; shear strength; triaxial shear tests; CT scanning我国黄土高原北部地区分布的砒砂岩，是一种由厚层砂岩、页岩和泥质砂岩组成的互层状陆相碎屑岩系[1-3]，是由各种砂粒堆积、胶结在一起的风化沉积岩，其颗粒直径通常为0.062 5～2 mm [4-5]。
纤维加筋黄土的三轴蠕变试验研究
摘要摘要土的流变问题是岩土工程设计中普遍需要考虑的一个问题，土的流变效应是土体变形随时间变化的过程。
蠕变作为土的流变效应的一种，近年来已有大量学者参与研究，已有研究表明黄土具有明显的蠕变效应，纤维加筋黄土作为新型复合土，必然存在蠕变特性。
对于纤维加筋黄土的蠕变研究，不仅能对纤维加筋黄土的理论进行补充，还能对黄土地区地基改良技术做相应的实践指导。
本文采用了固结排水的试验方式，对杨凌某工地黄土进行了玄武岩纤维加筋黄土三轴剪切蠕变试验，通过对不同偏应力、初始含水率、加筋率和围压控制，分析了纤维加筋黄土的蠕变特性，模拟了纤维加筋黄土的蠕变经验方程。
研究表明：（1）黄土和纤维加筋黄土试样的蠕变变形均随着偏应力的增大而增大，都符合标准的蠕变曲线类型，可分为4阶段：弹性阶段、衰减蠕变阶段、蠕变稳定阶段与等速蠕变阶段。
在施加低水平偏应力时，土体先发生瞬时弹性变形，随着偏应力的升高，表现为衰减蠕变的趋势，偏应力达到某一临界值时，表现为蠕变稳定的过程，当偏应力增加到一定大小时，试样进入等速蠕变阶段。
（2）玄武岩的掺入，对黄土的蠕变变形抑制效果明显。
纤维加筋黄土的蠕变变形随着加筋率的升高先减小后增大，存在最优加筋率，本试验中以蠕变变形最小时加筋率0.25%为最优加筋率。
0.25%、0.50%、1.00%的加筋率的纤维加筋黄土相对于素土所减小的变形分别维持在31%、26%、19%左右，超过最优加筋率时，加筋效果随着加筋率的升高而减小。
（3）含水率对于黄土和纤维加筋黄土蠕变的影响效果显著，黄土和纤维加筋黄土的蠕变变形、蠕变速率、蠕变到达稳定阶段所用的时长都是随着初始含水率的升高而增大，纤维加筋黄土的加筋效果随着初始含水率的升高而减小，且在低偏应力下这种趋势表现得更为明显；围压对黄土和纤维加筋黄土的蠕变有一定影响，随着围压的升高，黄土和纤维加筋黄土的蠕变变形、蠕变速率均减小；纤维加筋黄土的加筋效果随着围压的升高而增大，这种趋势在高偏应力下更为明显。
三轴压缩与干湿循环作用下灰岩的力学试验研究
试验设备使用的是由美国 MTS 公司生产的三轴伺服刚性试验机 MTS815, 专门适用于岩石和混凝 土, 它具有 3 套独立的闭环伺服控制功能, 分别是轴压、围压和孔隙水压。可开展单轴与三轴压缩试验、 流变试验、流—固耦合试验等, 能实现最大轴向压力(拉力)4 600 kN(2 300 kN), 最大动态围压 140 MPa 和最大孔隙水压 140 MPa。
南京地铁 6 号线万寿村站至燕尧路站区间深部主要为灰岩, 盾构隧洞贯通后, 深部岩体对隧洞维护 起至关重要的作用, 据此, 本文通过该地铁深部灰岩在干湿循环后的常规三轴试验, 研究了灰岩在不同 干湿循环次数与不同围压条件下的强度与变形特征, 为该地铁深部稳定性提供理论指导。
1 干湿循环试验设计
1.1 试样准备
1.3 干湿循环三轴压缩试验方案
根据国家标准[25], 本文试件干湿循环方法为: (1) 将标准岩样放入 105 ℃烘箱中干燥 24 h, 待其冷 却至室温后取出; (2) 再放入容器中自由吸水 24 h, 水为纯净水, 中性。上述两步为 1 次干湿循环, 本文 设定干湿循环次数有 0、1、5、10 次。
通信作者: 常乐, 1120361969@。收稿日期: 2020–07–22
70
湖南文理学院学报(自然科学版)
2021 年
number of wet and dry cycles, the inclination of the shear fracture surface gradually increases, and the shear failure becomes more obvious. Keywords: rock mechanics; triaxial compression; wetting-drying cycle; failure mode; peak strength
深部砂岩力学特性试验与本构模型
深部砂岩力学特性试验与本构模型张向东;蔡冀奇;唐楠楠;李庆文;孙闯【摘要】为深入探究岩石强度劣化特性对深部开采工程稳定性的不利影响.以红庆梁深立井工程为背景,对现场砂岩岩样开展不同围压条件下三轴压缩试验,结合Mohr-Coulomb强度理论研究了砂岩应力-应变、强度与变形等特征;基于岩石损伤变量服从Weibull分布的特点,推导出砂岩损伤软化本构模型,探讨了模型参数F0和m与围压的函数关系,结合模型参数对模型的影响及砂岩应力-应变曲线变化特点,采用非线性拟合方法对模型参数进行修正,最后得到修正的损伤软化本构模型;利用FLAC3D对修正后的本构模型数值求解,将理论计算结果与砂岩全应力-应变曲线对比验证;通过构建马头门硐室围岩数值模型对修正后本构模型进行工程应用,并分析了数值计算结果的合理性.结果表明:①砂岩变形参数对围压敏感度较低,强度参数受围压影响较大,不同围压条件下,当应力达到峰值后,砂岩呈现出明显的应变软化特性;②通过FLAC3D数值验证结果可知,损伤软化模型理论计算应力-应变曲线与试验曲线高度吻合,说明模型具有较高的真实性,能反映砂岩在复杂应力状态下的破坏全过程;③利用数值模拟方法对深部马头门硐室围岩与支护结构破坏规律分析表明,在拱顶及拱肩位置较易出现塑性剪切破坏,并且与实际工程中支护结构破坏位置及范围基本相同.【期刊名称】《煤炭学报》【年(卷),期】2019(044)007【总页数】7页(P2087-2093)【关键词】砂岩;力学特性;本构模型;稳定性分析【作者】张向东;蔡冀奇;唐楠楠;李庆文;孙闯【作者单位】辽宁工程技术大学土木工程学院,辽宁阜新123000;辽宁工程技术大学土木工程学院,辽宁阜新123000;辽宁工程技术大学土木工程学院,辽宁阜新123000;辽宁工程技术大学土木工程学院,辽宁阜新123000;辽宁工业大学土木建筑工程学院,辽宁锦州 121001;辽宁工程技术大学土木工程学院,辽宁阜新123000【正文语种】中文【中图分类】TD315砂岩在我国西北深部地层中广泛分布并比较常见，随着我国煤炭资源的开采强度不断加大，矿井建设逐渐向深部发展，以砂岩为工程地质条件的情况日益增多[1-2]。
富水全、强风化砂岩强度特性试验及本构关系探讨
富水全、强风化砂岩强度特性试验及本构关系探讨邹翀;雷胜友;岳喜军;宋妍;高攀【摘要】According to the feature of sandstone weathered and absorbed water heavily, the authors analyzed the physical and mechanical properties and chemical composition of the sandstone experimentally, then studied influence of blasting disturbance, water content, sample bedding on stress-strain strength characteristics through uniaxial and triaxial compression tests, and found that the sandstone would become weak in the strength when it absorbed water, and its cohesion decreased and showed significant anisotropy while friction angle was not changed.After the sandstone underwent blasting, its uniaxial compressive resistance and elastic modulus decreased, and Poisson ratio increased. As the sandstone has obvious bedding properties, the strengths of sample obtained from two different loading directions are different obviously. Based on the stress-strain curves from the triaxial tests, the anthors found the stress-strain curves could be described well by the modified Duncan-Zhang model.%针对富水全、强风化砂岩的特点,进行了该砂岩的基本物理力学性质、化学成分实验,然后通过单轴、三轴压缩实验研究了爆破扰动、含水量、试样层理对砂岩应力-应变强度特性的影响.发现砂岩遇水软化,粘聚力大幅度降低,表现出显著的各向异性;爆破扰动后,岩石试样的单轴抗压强度减低,弹模减小,泊松比增大;由于砂岩具有明显的节理性,按两种方向加载所得到的岩石试样强度明显不同;根据实验所得应力-应变曲线特点,发现用修正的Duncan-Zhang模型可以很好地描述砂岩的前应力-应变曲线.【期刊名称】《中国工程科学》【年(卷),期】2011(013)001【总页数】7页(P74-80)【关键词】砂岩;含水量;强度;爆破扰动;节理;本构关系【作者】邹翀;雷胜友;岳喜军;宋妍;高攀【作者单位】中铁隧道集团有限公司技术中心,河南洛阳,471009;长安大学公路学院,西安,710064;长安大学公路学院,西安,710064;中铁隧道集团有限公司技术中心,河南洛阳,471009;中铁隧道集团有限公司技术中心,河南洛阳,471009【正文语种】中文【中图分类】TU425某新建铁路隧道围岩属强风化砂岩，隧道岩层产状310°∠3°～280°∠7°，岩层主要发育三组节理:①103 °∠78 °张节理，节理间距为0.5 ～0.6 m，裂隙宽度为1.5～2.0 mm，充填泥质，延长2～3 m;②153 °∠80 °张节理，节理间距为 0.4 ～0.5 m，裂隙宽度为1.5 ～2.0 mm，充填泥质，延长 4～5 m;③250°∠66 °张节理，节理间距为 0.7～0.8 m，裂隙宽度为0.8～1.0 mm，充填泥质，延长5～8 m。