开展土石混合体的大型叠环式单剪试验与大型三轴试验,根据颗粒材料及砂土的单剪试验规律分析单剪试样应力状态,探讨两种试验条件下土石混合体的强度特性差异。结果表明:①对应相同小主应力,试样在单剪过程中的大主应力率水平更低、变化范围更小,主应力比峰值更低,对应极限应力摩尔圆更小;②单剪条件下的割线剪切模量各向异性,其中水平向割线剪切模量在剪切过程中恒低于三轴条件下的割线剪切模量,但差值随主应力轴与主应变轴间的非共轴度减小而减小;③对于采用试料,单剪条件下的摩尔-库仑抗剪强度指标值显著低于三轴条件下的值,其中内摩擦角低约9.5%。初步研究认为,单剪过程中的主应力轴旋转以及非共轴性是造成土石混合体2种试验强度特性差异的重要原因。
Abstract
Large-scale laminar-ring simple shear test and large-scale triaxial test of soil-rock mixture(SRM) were carried out. The stress state of samples in simple shear was analyzed according to the joint test law of granular material and sand in simple shear. The differences in the strength properties of SRM under simple shear and triaxial compression were then explored. Results reveal that: (i) With the same minimum principal stress, the rate of maximum principal stress in simple shear is lower and changes in a smaller range, and the peak value of principal stress ratio is lower, which means the ultimate Mohr's circle of stress is smaller. (ii) The secant shear modulus under simple shear is anisotropic, and the secant shear modulus in horizontal direction is constantly lower than that under triaxial compression, but such difference shortens with the decrease of non-coaxiality degree between principal stress axes and principal strain axes. (iii) For the samples used, the shear strength indices of Mohr-Coulomb strength criterion obtained under simple shear are significantly lower than those under triaxial compression, and in particular, the internal friction angle is about 9.5% lower. Preliminary investigation shows that the rotation of principal stress axes and non-coaxiality in simple shear are important reasons for the differences of strength properties of SRM.
关键词
土石混合体 /
强度特性 /
大型单剪试验 /
大型三轴试验 /
主应力轴旋转 /
非共轴
Key words
soil-rock mixture /
strength properties /
large-scale simple shear test /
large-scale triaxial test /
rotation of principal stress axes /
non-coaxiality
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基金
国家自然科学基金项目(51979009;52008032);中央级科研院所基本科研业务费项目(CKSF2019191/YT)
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