不排水条件下轴向加卸载时结构性土的力学特性探讨

 为研究结构性土在不排水条件下的力学特性，开展固结不排水条件下初始应力各向异性结构性土、各向同性结构性土及重塑土在25，50，100，200及400 kPa共5种围压下的三轴加卸载试验，并利用二元介质概念对试验现象进行了分析。结果表明：结构性土在固结应力较低时结构性保持较好，存在明显的结构屈服强度，不同应力循环中平均模量无明显变化；固结应力较高时结构性减弱，表现为与重塑土相似的特性，受结构性减弱及正孔压等因素影响，平均模量随εa增加而减小；结构性土胶结元破损率与摩擦元中土颗粒间距随轴向应变增加而增大，卸载时体缩趋于明显。

Investigation on mechanical properties of structured soils subjected to axially loading-unloading under undrained conditions

To study the mechanical properties of structured soils under undrained conditions，the triaxial compression tests on reconstituted soils and two kinds of structured soils with initial stress-induced anisotropy and isotropy were carried out under axially loading-unloading-reloading. The soils were tested under consolidation- undrained(CU) conditions at the confining pressures of 25，50，100，200 and 400 kPa，and the results of tests are analyzed with the binary-medium theory. It is found that the structured soils have stronger structures at lower consolidation stress. Meanwhile，Eave does not change significantly in different stress cycles. When the confining pressures are higher，the structures of soils are weakened，and their characteristics are similar to those of reconstituted soils. Because of the structure weakening and positive pore pressure，Eave decreases with the increase of εa. With the increase of the axial strain，the breakage rate of the bonded components and the soil particle spacing of friction components increase. In the meantime，the tendency of the volume contraction becomes more apparent when unloading.