岩土工程不连续变形分析计算中的若干问题

通过引入黏性阻尼吸收块体动能,基于变分原理建立考虑阻尼力影响的块体系统总体平衡方程,给出DDA方法求解准静态问题的正确能量耗散方式,并定义系统达到稳定状态后的位移、速度以及加速度收敛准则和相应的控制标准.考虑到开挖岩体的稳定性与开挖程序及应力历史紧密相关,根据DDA方法的特点,探讨DDA数值模拟中开挖荷载和锚固支护荷载的计算问题,发展采用DDA模拟岩体分期开挖的两种计算方法:基于开挖荷载的模拟方法和基于软化单元的模拟方法,并给出相应的迭代计算格式.数值算例和工程实例分析表明,针对上述问题进行改进后DDA方法不仅具有较高的计算精度,而且具有较好的收敛性能,便于在实际工程中应用.

SOME ISSUES IN DISCONTINUOUS DEFORMATION ANALYSIS FOR GEOTECHNICAL ENGINEERING

Some key problems including energy dissipation,convergence criterion and simulation of construction procedure for geotechnical engineering in discontinuous deformation analysis(DDA) method are discussed.A linear viscous-type resistance is used to absorb the kinetic energy of the block system;and the equilibrium equations to contain damping term are derived by minimizing the total potential energy.The mechanism of the energy consumption by damping force is discussed;and three types of convergence criteria including displacement criterion,velocity criterion and acceleration criterion are defined to ensure convergence to the correct result for quasi-static analysis.According to the features of DDA,the problems of the excavating load and bolting load in the analysis of geotechnical engineering are studied.Two new algorithms to simulate sequential excavation for rock masses have been developed and implemented into the DDA program.Three typical numerical examples are calculated to demonstrate the capability of the DDA with the new extensions.The computational results show that the improved DDA has not only high accuracy and good convergence performance,but also is easily applied to practical engineering.