淋溪河水电站大野坪滑坡体渗流应力耦合分析

Seepage-stress coupling analysis of Dayeping landslide in Linxihe Hydropower Station

软弱夹层的渗流、应力耦合作用是影响滑坡体稳定性的主要因素。为正确评价含软弱夹层的大野坪滑坡体的整体稳定性,基于Biot固结微分方程,采用虚位移原理,按照Goodman单元的形成格式,引入Desai单元控制嵌入的思想,构造了二维4节点耦合薄层单元,给出了能够模拟滑坡体蠕变特性的弹黏塑性本构模型,编制了相应的有限元程序,并用孔压实测数据检验了程序的正确性。同时,对大野坪滑坡体处于正常蓄水位和水位骤降两种工况的渗流场、应力场进行了非线性有限元耦合分析。结果表明:正常蓄水位,滑坡体处于稳定状态;而水位骤降工况,使滑坡体中前部孔隙水压力、位移、剪应力水平等均有大幅度地提高,塑性区沿着软弱夹层向上也有较大发展,致使滑坡体有可能沿着软弱夹层在中前部发生局部折线滑动,对滑坡体的稳定性极为不利。最后,采用刚体极限平衡法,对耦合分析的结果进行校核,两者结论一致。该研究成果为全面评价淋溪河水电站建设的可行性提供了重要的理论依据,建立耦合单元研究软弱夹层耦合特性的方法,为其他含软弱夹层的滑坡体的稳定性评价提供了有益的借鉴。

The seepage-stress coupled interaction of weak intercalated layer is the key factor affecting landslide stability. In order to estimate the integral stability of Dayeping landslide with weak intercalated layer, based on Biot consolidation differential equation, according to Goodman element form and introduced the interpenetration check idea of Desai element, 2D four nodes coupled thin-layer element is established by virtual displacement principle. An elastic-viscoplastic constitutive model is given to simulate the creep of landslide; and a corresponding finite element program is developed; then the program is verified by in-situ pore pressure testing data. At the same time, by using nonlinear FEM the seepage-stress coupling analyses of Dayeping landslide are carried out under normal water level and water level falling suddenly. The results indicate that the landslide is stable under normal water level, but under water level falling suddenly, landslide stability becomes worse because water level falling suddenly make the pore pressure, displacement, shear stress, plastic zone increase rapidly in middle-front part, and this may result in landslide middle-front part slipping along weak intercalated layer. In the end, rigid limit equilibrium method is used to verify coupled results; and the two conclusions are coincident. The analyses provide important theoretical basis for the comprehensive evaluation of Linxihe Hydropower Station construction feasibility, and the method establishing coupled element for analyzing weak intercalated layer provides helpful references for dealing with the stability of other landslides with weak intercalated layer.