饱和兰州黄土液化过程中孔压和应变发展的试验研究

采用WF12440型空心圆柱扭剪仪，用反压饱和法对初始饱和度较低的原状黄土进行饱和，进行室内原状黄土饱和液化试验研究，探讨了饱和兰州黄土液化过程中孔隙水压力、轴向应变、应力-应变滞回圈的发展规律。结果表明，对初始饱和度较低的原状黄土，反压饱和法使孔压系数B值达到0.95以上，即土样完全饱和；兰州黄土在均压固结条件下液化的孔压发展，开始时上升速率较缓慢，循环数一定后会出现孔压迅速增高的现象直至达到有效围压；应力-应变滞回特性随着振动次数的增加发生变化，塑性逐步增大；当轴向应变小于2%时，孔压增长缓慢；此后，孔压上升速率加大，3%应变可以出现在初始液化前；接近液化时偏应力为负值时的有效应力大于正值时的有效应力。

Experimental study of development of strain and pore water pressure during liquefaction of saturated Lanzhou loess

Using a dynamic hollow cylinder apparatus WF12440 as the test platform, this paper firstly studied the loess saturation by the back pressure method. The developments of pore water pressure, axial strain, deviatoric stress-axial strain curve during liquefaction are then investigated. Testing results indicate that the back pressure method can be successfully used for loess saturation; and the pore water pressure coefficient could achieve 0.95 and more. Under the condition of isotropic consolidation, pore water pressure increased slowly at the beginning; after several cycles the pore water pressure increased rapidly until it reached the effective consolidation pressure. The deviatoric stress-axial strain curve developed with the increase of cycles; and plastic strain increased step by step. When the axial strain was less than 2%, the pore water pressure increased slowly; afterwards, its increase ratio was much larger, and a strain of 3% could appear at the initial liquefaction process. Before liquefaction of the loess, the mean effective stress under negative deviatoric stress is larger than that under the positive deviatoric stress.