非饱和黄土初始剪切模量与孔径分布试验研究

Experimental study on initial shear modulus and pore-size distribution of unsaturated loess

土的初始剪切模量G_0是地震、爆破响应中一个非常重要的土动力学参数,对预测地表沉降、土工建筑物周围土体变形等具有重要作用。黄土在中国及世界各地分布广泛,且现场常处于非饱和状态。对非饱和黄土的压实试样进行了吸力控制的共振柱试验以及压汞试验,研究非饱和黄土初始剪切模量G_0与孔径分布的关系。试验表明:干湿循环过程中,试样的G_0随吸力的增大而增大,再随吸力的减小而减小。主要原因是试样内孔隙密度最大的孔径大小随吸力的增大而减小,试样内大孔隙减少,小孔隙增多,导致毛细水所占比例增加,土颗粒接触更加紧密。同一吸力作用下,湿润段试样的小孔隙比例比干燥段大,故毛细水作用更显著,从而湿润段试样的G_0大于干燥段。

The initial shear modulus of soil G_0 is an important parameter for predicting the ground deformation and dynamic response of many earth structures subjected to earthquake or explosion. Loess is spread all over the world and is usually in unsaturated state in the field. The principal objectives of this research are to investigate the initial shear modulus and pore-size distribution of an unsaturated loess by using the suction controlled resonant column tests and mercury intrusion porosimetry tests. The test results show that G_0 increases with the increasing suction during drying and decreases with suction during wetting. The main reason is that the amount of large pores decreases while that of small pores increases during drying. As a result, the amount of meniscus water increases, which holds soil particles more tightly. Under the same suction, the amount of small pores is larger for specimens during wetting than that during drying, which results in stronger meniscus water effect and thus G_0 during wetting is higher than that during drying.