南水北调中线段原状膨胀土抗剪强度试验研究
Study on Shear Strength of Undisturbed Expansive Soil of Middle Route of South-to-North Water Diversion Project
作者：戴福初(华北水利水电大学 资源与环境学院, 河南 郑州 450045;北京工业大学 城市与工程安全减灾教育部重点实验室, 北京 100124)；董文萍(华北水利水电大学 资源与环境学院, 河南 郑州 450045)；黄志全(华北水利水电大学 资源与环境学院, 河南 郑州 450045)；张晓丽(华北水利水电大学 资源与环境学院, 河南 郑州 450045)；王安明(华北水利水电大学 资源与环境学院, 河南 郑州 450045)；曹世超(华北水利水电大学 资源与环境学院, 河南 郑州 450045)
Author：DAI Fuchu(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China;Key Lab. of Urban Security and Disaster Eng. of Ministry of Education, Beijing Univ. of Technol., Beijing 100124, China)；DONG Wenping(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China)；HUANG Zhiquan(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China)；ZHANG Xiaoli(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China)；WANG Anming(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China)；CAO Shichao(Inst. of Resources and Environment, North China Univ. of Water Resources and Electric Power, Zhengzhou 450045, China)
收稿日期：2018-03-07 年卷（期）页码：2018,50(6):123-131
期刊名称：工程科学与技术
Journal Name：Advanced Engineering Sciences
关键字：膨胀土;黏粒含量;塑性指数;快剪强度摩擦角;残余强度摩擦角
Key words：expansive soil;clay content;plasticity index;quick shear strength friction angle;residual strength friction angle
基金项目：国家重点基础研究发展计划资助项目（2014CB744700）；河南省重点科技攻关项目资助（152102210111）；河南省科技创新人才计划资助项目（154100510006）；国家自然科学基金重点资助项目 （U1704243）；国家自然科学基金资助项目（41741019）；华北水利水电大学博士研究生创新基金资助项目
中文摘要
膨胀土的抗剪强度除了受含水率、干密度、正压力、干湿循环、裂隙等因素影响外，同时受到黏粒含量和塑性指数的影响。现有研究对于黏粒含量和塑性指数的考虑不足，不能系统、客观地反映某一个地区内膨胀土抗剪强度的规律性变化。以南水北调中线段某一个县的21种原状膨胀土为基础，作者研究了膨胀土中黏粒含量对其自由膨胀率、塑性指数的影响，并利用电动应变控制式剪切仪和ShearTrac Ⅱ反复直剪仪分别以0.8和0.02 mm/min的剪切速率开展了原状膨胀土的快剪（包括快剪、饱和快剪、饱和固结快剪）试验和残余剪试验，分析了黏粒含量、塑性指数对快剪强度摩擦角、残余强度摩擦角的影响。研究结果表明：自由膨胀率随黏粒含量的增加逐渐增大并趋于平缓；塑性指数随黏粒含量的增加逐渐增大，当黏粒含量增大到33%时，塑性指数开始趋于平缓；试样抽气饱和后，强度明显降低，表现为饱和快剪强度摩擦角小于快剪摩擦角，固结对试样起到了“治愈”作用，强度明显提高，表现为饱和固结快剪摩擦角高于饱和快剪摩擦角；随着黏粒含量、塑性指数的增加，快剪摩擦角、饱和快剪摩擦角、饱和固结快剪摩擦角均随之减小，当黏粒含量、塑性指数达到临界值（临界值分别为32%和24%）后，摩擦角变化趋于平缓；残余强度摩擦角随黏粒含量的增加逐渐减小并趋于平缓，但是随着塑性指数的增加，残余强度摩擦角逐渐减小后是否趋于平缓尚有待进一步的研究。
英文摘要
The shear strength of expansive soil is not only influenced by the water content, dry density, vertical stress, wetting-drying cycle, crack and other factors, but also influenced by the clay content and plasticity index. However, the existing studies rarely considered the clay content and plasticity index, and thus could not systematically and objectively reflect the regularity of shear strength of expansive soil in a certain area. In order to study the effect of clay content on the free expansion ratio and plasticity index, the effect of clay content and plasticity index on the quick shear strength friction angle (including quick shear, saturated quick shear, saturated and consolidated quick shear) and residual strength friction angle of 21 expansive soils at a county of Middle Route of South-to-North Water Diversion Project, shear tests were conducted on undisturbed soil using electric strain controlled direct shear apparatus at 0.8 mm/min and ShearTrac Ⅱ reversal direct shear apparatus at 0.02 mm/min. It was founded that the free expansion ratio gradually increases with increase of clay content and then changes gently. The plasticity index exhibits a logarithmic growth relation with clay content and then changes gently as clay content increased to 33%. The shear strength of samples significantly reduces after saturating, ie. The friction angle of saturated quick shear is less than the quick shear friction angle. There is a "cure" effect of consolidation on the samples, the strength is obviously improved, ie. The friction angle of saturated and consolidated quick shear is larger than the saturated quick shear friction angle. The friction angle of quick shear, saturated quick shear, saturated and consolidated quick shear decreases with increase of clay content and plasticity index, and then changes gently with critical value about 32% and 24%,respectively. The friction angle of residual strength decreases with increase of clay content and then changes gently. With the increase of plasticity index, the friction angle of residual strength decreases, but it is not clear whether the friction angle changes gently after decreasing. Further research is being carried out by the project team.
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