考虑渗流与蠕变耦合作用的水库滑坡变形数值分析

Numerical Analysis on Deformation of Reservoir Landslides Considering Coupling Effect of Seepage and Creep

水库滑坡土体的变形主要是流固耦合作用的结果,但是变形并不是立刻发生的,大都经历了一个时间发展的过程,具有典型的流变特性。本文基于某滑坡土体的蠕变试验结果,推导了扩展的Burgers蠕变模型M–2K,并将其推广至3维形式,应用蠕变试验数据对推导的M–2K蠕变模型进行拟合,求得了蠕变模型参数。在传统的流固耦合分析中引入了时间变量关系,构建了渗流与蠕变耦合作用的数学模型,对其进行有限元求解,并应用MATLAB软件编写了有限元程序。以三峡库区白家包滑坡为例,应用该程序分别对滑坡体进行了考虑蠕变及不考虑蠕变的流固耦合计算。研究结果表明:3维形式的M–2K蠕变模型拟合程度较高,能反映土体的蠕变性质;有限元计算结果说明考虑渗流与蠕变耦合作用下孔压减少值大于不考虑耦合作用下时孔压减小值;选取关键点的耦合及非耦合条件位移计算结果与实际的GPS位移进行比较,两种计算值与实际监测值变形趋势基本一致,考虑渗流与蠕变耦合条件下两个监测点的位移值比不考虑耦合时大,而且与实际值比较接近。研究结果表明:所建立的渗流与蠕变耦合数学模型是合理的,有限元数值求解程序是正确的,该成果为水库滑坡的预测与预报提供了新途径。

The deformation of reservoir landslide is mainly resulted from fluid-solid coupling.It is not occurred immediately,but gone through a long-term development and exhibiting typical rheological characteristics.In this study,the extended Burgers creep model(M–2K)was derived and extended into the three-dimensional form.The creep testing results of the landslide soil were fitted by the derived M–2K creep model and the creep model parameters were obtained.A time-dependent relationship was introduced in to the traditional fluid-solid coupling analyses,and a mathematical model of the seepage–creep coupling was derived and solved by finite element method.Taking the Baijiabao landslide in the Three Gorges Reservoir Area as an example,the numerical calculations considering the seepage–creep coupling or non-coupling were completed using this program.The results demonstrate that the three-dimensional M–2K creep model had a high fitting degree and could reflect the creep properties of the landslide soil.The finite element calculation results show that the pore pressure reduction value under the seepage–creep coupling condition was greater than that under the non-coupling condition.The displacement calculation results of the key points under seepage–creep coupling or non-coupling conditions were compared with the actual GPS displacement measurements.The evolution trend of calculated results were basically consistent with the actual monitoring results,and the displacement values of two monitoring points considering the seepage–creep coup-ling were larger than those without considering the coupling process and more closer to the actual value.The results show that the established mathematical model of seepage–creep coupling is reasonable and the finite element numerical solution procedure is correct.The research provides a more reasonable and accurate new way for reservoir landslide prediction.