大型地下洞室三维弹塑性损伤动力有限元分析

采用动力时程分析法研究地下洞室地震响应特性。根据运动学动力平衡方程,以Newmark直接积分法为基础,结合三维弹塑性损伤有限元理论,编写动力时程计算程序。采用塑性附加荷载、损伤附加荷载思想考虑单元塑性及损伤情况,每时步计算对单元损伤状态进行继承,反映损伤不可逆性。采用增量变塑性刚度迭代法,求解非线性动力方程。计算结果表明,该方法一般3步内收敛,计算快,精度高。阐述大型地下洞室动力响应时程分析中,模型边界条件的设置方法及动荷载的输入方式。通过对渔子溪大型水电站地下厂房洞室群的模拟计算表明,该程序计算速度较其他商业程序速度快,计算结果合理,准确,可以应用于地下工程动力时程分析。

DYNAMIC FINITE ELEMENT ANALYSIS OF LARGE-SCALE COMPLEX UNDERGROUND CAVERNS WITH THREE-DIMENSIONAL ELASTOPLASTIC DAMAGE MODEL

The seismic response characteristics of underground caverns are studied by employing dynamic time-history method. Based on the dynamic equilibrium equations of kinemato-dynamic time-history method and Newmark direct integration method，the computational codes are programmed by adopting three-dimensional elastoplastic finite element theory. The concepts of additional plastic load and additional damage load are considered to simulate the plasticity and damage of elements. The damage state of rock mass within each time step is inherited by subsequent time steps. Therefore，the irreversible trend of rock damage can be reflected. The incremental variable plastic stiffness iteration method is employed to solve dynamic equations. The calculation results show that the proposed iteration method has good convergence and fast computational speed. The iteration of each step can attain convergence within 3 steps. The way to setup boundary condition and the way to input dynamic loads are expounded by performing dynamic time-history analysis of large-scale complex underground caverns of Yuzixi hydropower station. The calculation results show that the computational speed of the proposed method in the codes is faster than that of common software. The calculation results are reasonable as well，which indicate that the proposed methods are rational and can be used to carry out dynamic time-history analysis of underground engineering.