中文摘要：

对杭州饱和软黏土的不排水三轴压缩试验的静力特性进行研究。重点分析加荷速率与初始剪应力的耦合作用对杭州软黏土静力特性的影响。研究结果表明：随着初始剪应力的增加，土样的总强度增加，但抗剪强度减少；初始剪应力为60kPa时，衰减幅度可达60％；土样的孔隙水压力表现为降低的趋势，初始剪应力为60kPa时，衰减幅度可达50％。随着加荷速率的增加，土样的强度有所提高；孔隙水压力随之降低。当不存在初始剪应力时，应力-应变关系表现为硬化型曲线；当存在初始剪应力时，随着初始剪应力的增加，应力-应变关系曲线向软化型曲线发展。通过引入量纲一的峰值剪应力参数s与峰值孔隙水压力参数AP对加荷速率与初始剪应力耦合作用下土体的峰值强度与孔隙水压力变化规律进行描述。该参数综合反映了初始剪应力与有效围压的影响。归一化后的结果表明：随着量纲一的应变率增加，s增加，AP减少。在半对数坐标下，s，AP分别与量纲一的应变率呈直线关系，并且随着初始剪应力的增加，s与AP变化并不显著。

英文摘要：

Undrained triaxial compressive tests are carried out on Hangzhou saturated soft clay to investigate the coupling effects of initial shear stress and loading rate on the monotonic characteristics of soft clay. It is observed that the shear strength decreases and the total strength increases as the initial shear stress increases. When the initial shear stress is 60 kPa, the shear strength decreases about 60%. The pore water pressure decreases with the increase of initial shear stress. When the initial shear stress is 60 kPa, the pore water pressure reduces about 50%. As the increase of loading rate, the strength increases and pore water pressure decreases. The stress-stain curve shows the strain-hardening characteristic without initial shear stress. However, it turns to be strain-softening with the increase of initial shear stress. Empirical equations for the peak strength and pore water pressure considering the coupling effects of initial shear stress and loading rate are proposed respectively by introducing the normalized peak shear stress parameter s and pore water pressure parameter △P. It is observed that with the increase of normalized strain rate, s increases and △P decreases. The relationships between s, △P and normalized strain rate show linearity with a semi-log scale. In such a case, the effect of initial shear stress on s and △P is not significant.