中文摘要：

利用GDS应力路径三轴试验系统对南阳膨胀土进行3种应力速率下、4种超固结比(OCR)的被动压缩三轴试验及3种超固结比的被动挤伸三轴试验,分析了不同超固结比和应力速率下其应力(孔隙水压力)-应变关系、有效应力路径及变形模量的演化规律,对膨胀土变形模量各向异性特性进行了初步探讨。结果表明,应力速率、超固结比及卸荷路径均对膨胀土力学特性有一定影响。在被动压缩路径和被动挤伸路径下,随着应力速率和超固结比的增加,相同轴向应变时的偏应力值单调增加;不同超固结比和应力速率时膨胀土的孔隙水压力始终为负值,且其降幅总体上随超固结比的增加而增大,但其降幅随应力速率的变化规律与剪切路径有关。在被动压缩路径下,相同应变时不同应力速率下的孔压降幅基本相同;而在被动挤伸路径下,其降幅随应力速率的增加而增大。边坡开挖路径的选择对于边坡变形影响显著,被动挤伸路径下达到设定极限偏应力时的轴向应变明显大于被动压缩路径。膨胀土变形模量E100随着超固结比和应力速率的增加而增加,但各应力速率下变形模量的各向异性特性则随着超固结比的增加而变弱。

英文摘要：

A total number of 21 consolidated undrained triaxial shear tests on Nanyang expansive clay have been performed by GDS stress path triaxial system. The specimens are prepared in kinds of 4 different overconsolidation ratios (OCR) for reduced triaxial compression (RTC) shear tests and 3 for reduced triaxial tension (RTT) shear tests, which all sheared at three different stress relief rates. The influences of OCR and stress rate on stress-strain relationship, pore water pressure, effective stress path and deformation modulus are investigated. The results show that the influences of OCR and stress rate on mechanical behavior of expansive clay in compression and tension are similar. As the increase of stress rate and OCR, the deviatoric stress in stress-strain curve increased monotonically to the maximum with the same axial strain. The pore water pressure is always negative with different OCRs and unloading stress rates in compression and tension. The decreasing range increased with the increasing of OCR, and the influence rule of stress rate on the change range of pore water pressure is shear stress path related. The deformation modulus E100 increased with the increasing of OCR and stress rate; but the anisotropy of deformation modulus is becoming weaker as the increase of OCR under different stress rates.