用非连续介质模型分析拱坝坝肩的动力稳定性

DYNAMIC STABILITY ANALYSIS OF ARCH DAM ABUTMENT WITH DISCONTINUOUS MEDIA MODEL

拱坝坝肩岩体内包含断层、裂隙等结构面,分析坝肩岩体的稳定性宜采用非连续介质力学模型。界面元可以较好地模拟相邻两单元界面上位移的不连续性,适用于描述单元之间的分离和滑移现象,用于坝肩稳定可靠度分析可以得到更加符合实际的计算结果。坝肩稳定分析中涉及到的水压荷载、地震作用、岩石的力学参数等均为随机变量,适合用结构可靠度理论分析坝肩的稳定性。坝肩岩体是变形体,其受力后产生的应力和变形是判断坝肩稳定性的主要指标,以断层、界面上的抗拉、抗剪能力作为可靠度计算的强度准则,建立极限状态方程,采用响应面法计算坝肩稳定的动力可靠度。坝肩稳定可靠性是结构体系可靠度分析问题,在研究破坏模式的基础上,通过修改劲度矩阵模拟结构状态的变化,跟踪计算各单元的可靠度,最后得到坝肩稳定的可靠度或坝肩发生失稳的概率。针对某一拱坝进行坝肩动力稳定可靠度分析的结果表明,采用非连续介质力学模型和响应面法计算坝肩稳定的可靠度是可行的,得到的结果是合理的。

There are many faults and cracks in rock of arch dam abutment. It is appropriate that abutment stability is analyzed by discontinuous media mechanical model. The interface element method(IEM) is well used in the modelling of the displacement discontinuity in the interface of two adjacent elements. It is applicable to describe the phenomena of detachment and sliding between the two elements. The more practicable results may be obtained with the IEM being used to analyze the abutment stability. The concerned variables,such as water pressure,earthquake load,material parameters and so on,are random variables in the study of abutment stability. Structural reliability theory is suitable for the analysis of abutment stability. The abutment rock mass is deformable body,and the stress and deformation of the abutment rock mass are the main indexes in determining the abutment stability. The tensile and shearing strength of faults and interfaces are regarded as the criterion to establish the limit state equation. The response surface method is used in the reliability analysis of abutment. In order to calculate the system reliability of abutment,the stiffness matrix must be modified continuously to analyze the change of the structure. The method is used in an example of reliability analysis of abutment stability,and the obtained result shows that it is suitable for the stability analysis of abutment.