不同含水率下滑坡滑带土动力特性试验研究

Experimental Study on the Dynamic Properties of Sliding Zone Soil of a Landslide under Varying Water Content

甘肃舟曲泄流坡滑坡地处活跃断层破裂带内,断层活动控制着该滑坡的发育和运动。为了研究该滑坡滑带土的动力特性,采用重塑滑带土样,在固结不排水条件下,利用分级循环加载法开展动三轴试验,重点探讨含水率的变化对滑带土动力特性的影响规律。试验结果表明:含水率一定时,泄流坡滑坡滑带土的动弹性模量随动应变的增大呈指数形式减小;动应变一定时,动弹性模量随含水率的增大而不断减小,且衰减速率随含水率的增大而增大;含水率并不影响动弹性模量-动应变关系曲线的形态,不同含水率下该关系曲线可以进行归一化。滑带土阻尼比随含水率的增大而增大,阻尼比-动应变关系曲线也具有归一化特征。不同含水率下泄流坡滑带土动应力-应变本构关系可以用双曲线模型进行描述。

The Xieliupo landslide is in an active and ruptured fault zone,and its growth and movement are controlled by the active fault.Historically,the combined effect of earthquakes and rainfall has repeatedly activated the landslide,causing severe damage to life and property.Hence,it is important to evaluate the dynamic stability of the Xieliupo landslide for mitigation of the hazards.The sliding zone soil,viewed as one of the major components of a landslide,is always perceived as a key factor in keeping the landslide stable and steady.To investigate the dynamic properties of the sliding zone soil of the Xieliupo landslide,remolded specimens of various water contents are tested on a cyclic triaxial apparatus under consolidated and undrained conditions using a step-by-step method to increase the dynamic load.The test results show that the dynamic elastic modulus of the sliding zone soil decreases exponentially with the increase of shear strain under constant water content.As the water content increases,the dynamic elastic modulus of the slip soil also decreases continuously under the same confining pressure and its deterioration velocity increases with increased water content.It seems that there is a threshold water content（around the plastic limit）in describing the variation of maximum elastic modulus with water content.The maximum dynamic elastic modulus of the slip soil,calculated from the cyclic triaxial test results,initially reduces slowly with water content,but when the water content is above the plastic limit,it abruptly decreases with further increase of the water content.Additionally,the relationship between dynamic elastic modulus and dynamic strain under different water content could be perfectly normalized,referring to the maximum dynamic elastic modulus.The damping ratio of the slip soil increases with shear strain and under the same confining pressure,the damping ratio increases as the water content increases.The relations between damping ratio and dynamic shear strain of the slip soil could also be normalized based on the maximum damping ratio.Based on the analysis of the cyclic triaxial test results,it can be concluded that the backbone curves of dynamic stress against strain for the sliding zone soil of the Xieliupo landslide could be described using the conventional hyperbolic model.