降雨作用下地震损伤斜坡破坏机理研究

Study on failure mechanism of earthquake damage slope under rainfall condition

地震导致斜坡岩体产生裂隙,岩体裂隙的存在为不稳定斜坡再次发生灾害提供了条件。降雨渗入到损伤斜坡裂隙中,使斜坡岩体强度降低,进而诱发大规模地质灾害。根据损伤力学理论,考虑岩体损伤与降雨入渗流的作用,基于FLAC^(3D)自定义损伤本构的二次开发,利用C++开发环境建立裂隙岩体的损伤本构模型。结合都江堰三溪村滑坡的成灾特征,运用开发的损伤本构模型,分析降雨入渗过程中斜坡内孔压场的分布规律及其破坏机理。分析结果表明:在降雨初期,斜坡到达完全饱和之前,有效应力变化幅度很大,斜坡内不同岩性岩体交界面位置的孔隙水压力值较大;地形陡峭的浅层岩体最先达到剪切破坏状态,随着降雨入渗时间增加,屈服范围逐渐向斜坡内部扩大,并且在斜坡的后部出现拉伸屈服破坏。降雨入渗强度在降雨前期对斜坡内的有效应力影响较大,当斜坡到达完全饱和之后,对有效应力的影响很小。

An earthquake can result in cracks in the slope rock mass,which provides the condition for the unstable slope failure. The rainfall may infiltrate into the cracks in the damaged slope,which reduces the strength of rock mass and induces large-scale geological hazards. In this paper,according to the damage mechanics theory,a new model of fractured rock mass is established by C ＋ ＋. It considers the effect of rock mass damage and rainfall infiltration,and is based on a second development of the damage constitutive model in FLAC3Dsoftware. The developed damage constitutive model is used for analysis of Sanxi village landslide in Dujiangyan. The pore water pressure distribution law and failure mechanism of the damage slope in the process of rainfall infiltration is investigated. The results show that the effective stress changes greatly before the slope reaching full saturation,and the pore water pressure is relatively large in the interfaces of different rock masses in the slope. At the same time,the shallow rock with steep terrain firstly reaches shear failure state. The yield range gradually expands into the slope with the increase of rainfall infiltration time and the tensile yield failure occurs at the back of the slope. What＇s more,the rainfall infiltration intensity has a great influence on the effective stress of the slope in the early stage of rainfall,while its effect becomes very small when the slope is completely saturated.