粉质黏土卸荷变形特性试验研究

依托武汉长江隧道江北明挖段基坑工程，开展了一系列的K0固结状态下原状粉质黏土卸荷应力路径排水剪三轴试验，并对卸荷变形特性进行了深入分析。分析表明：卸荷应力路径下原状粉质黏土的应力-应变关系与应力路径有着密切的关系，近似呈双曲线型。根据应力-应变曲线表现，可将卸荷应力路径分为A、B两组，A组应力路径试样表现为轴向压缩；B组应力路径试样表现为轴向伸长。卸荷应力路径下粉质黏土的应力-应变关系具有良好的归一化特性，同一应力路径下不同固结压力的应力-应变曲线可采用双曲线函数用平均固结压力归一化，但A、B两组应力路径下的归一化方程有所差别。给出了各种应力路径下的归一化方程，可为卸荷土体的变形参数及本构关系研究提供参考。

Experimental study on deformation behavior of silty clay under unloading

Relying on the open excavation section of Jiang Bei of the Yangtze River tunnel in Wuhan,a series of drained triaxial tests on unloading stress paths at K0 consolidation have been carried out with undisturbed silty clay.And the deformation characters under unloading were deeply analyzed.Analysis shows that stress-strain curves and stress paths have close relationship and the stress-strain curves under unloading are similar to a hyperbolic type.According to the stress-strain curves,unloading stress paths can be divided into two groups A and B.The stress paths of group A exhibit axial compression and ones of group B show axial tension.The normalization of its stress-strain relationship is very good under unloading stress paths for undisturbed silty clay.The stress-strain curves of different confining pressures in the same stress path can be normalized with average confining pressures.But normalized equations of groups A and B are different.Additionally the normalized equations of all stress paths have been given.This outcome can be used to further research on both deformation parameters and constitutive equation of soils under unloading.