基于Newmark积分方案的DDA方法

 不连续变形分析(DDA)方法以离散的块体集合作为研究对象，引入动力学分析和时步积分技术模拟块体系统的不连续变形行为。对DDA采用的常加速度法进行拓展，给出求解块体系统运动方程的Newmark积分格式，并引入一种与块体不平衡力成正比的自适应阻尼使系统收敛到新的平衡状态，保证求解的稳定性。作为考核，将基于Newmark积分方案的DDA方法应用到隧洞开挖模拟，通过和UDEC软件的计算结果进行对比分析，论证改进后DDA方法的有效性和实用性，进一步拓展DDA解决实际工程问题的能力。

DISCONTINUOUS DEFORMATION ANALYSIS METHOD BASED ON NEWMARK INTEGRATION ALGORITHM

Time integration theories applicable to the discontinuous deformation analysis(DDA) method are studied. The general formulae of the global increment displacement solution algorithm for the DDA by using Newmark method are presented. By changing the collocation parameters in Newmark method，a variety of well- known time integration algorithms are produced，including the constant，average and linear acceleration schemes. To ensure the stability of the integration algorithms，a self-adaptive damping which is in direct proportion to the imbalance force is introduced to consider energy losses for block system. An example of tunnel excavation has been analyzed，and the results are compared with those obtained by UDEC to evaluate the performance of the Newmark integration algorithms. The numerical results show the validity and the reliability of the improved DDA method.