重塑非饱和含粘砂土变形强度特性的三轴试验

利用多功能土工三轴仪探讨了非饱和含粘砂土的变形和强度特性，共进行3种应力路径的三轴试验：控制吸力的各向同性压缩试验、控制净平均应力的三轴收缩试验、控制吸力和净围压为常数的三轴排水剪切试验。研究结果表明：该土的屈服净平均应力和偏应力都随吸力增大；在净平均应力不变的条件下，该土的屈服吸力是一常数但不等于土样在历史上曾受过的最大吸力；随着净围压增大，其应力-应变曲线由软化向硬化型转变；在高吸力高围压下，呈现脆性破坏。控制吸力和净围压为常数的三轴排水剪切试验在p—q平面内的强度包络线为直线；在试验研究的吸力范围（50～200kPa）内，该土的粘聚力随吸力线性增加；内摩擦角随吸力的变化很小，可以认为是一常数；该土具有显著的剪胀特性，剪胀性不仅取决于千密度与围压，而且还与吸力密切相关。

Triaxial Test of Deformation and Strength Change of a Remolded Unsaturated Sand

With triaxial apparatus for unsaturated soil,the deformation and strength properties of remolded unsaturated sand are discussed. Three types of stress path tests using modified triaxial apparatus are conducted： an isotropic compression test with controlled suction, a triaxial shrinkage test with controlled net mean stress and a triaxial drained shear test with controlled suction and net cell pressure. The research shows that the net mean yield stress and deviatoric yield stress increase with suction, and the yield suction is not equal to the maximum suction experienced by the soil specimen under constant net mean stress. The stress-strain curves of undisturbed sand will change from strain softening to strain hardening with the increase of consolidation cell pressure. Brittles destroy will happen with high suction and high cell pressure. Strength envelopes in p - q plane of test with controlled suction and with controlled initial water contents is a line. The cohesion of unsaturated sand has a linear increase with the increase of suction within research suction range（50-200 kPa） , but the friction angle is found to have little change with the change of suction. The swell-shrinking of unsaturated sand is distinct. It not only depends on the dry density and the confining pressures, but also relates to the suction closely.