冲击荷载作用的离散-连续耦合数值模拟

强夯、冲击碾压工法广泛应用于水库堤坝、港口等水利工程。目前,冲击荷载作用下,复杂的动力响应研究主要依据室内模型试验和工程经验,数值模拟研究较少。本文结合离散单元法和有限差分法的优点,建立了冲击荷载作用的离散-连续耦合数值模型。冲击荷载作用中心区域采用PFC2D中的滞回阻尼模型进行精细模拟,周围区域采用FLAC2D中的摩尔-库伦模型进行模拟。在离散模型中,得到离散颗粒作用于边界墙的合力与合弯矩,根据力的平衡原理,分配到连续模型边界节点上,同时考虑到耦合边界不能承受拉应力,进行二次调整,实现边界面应力的传递;并通过接收连续模型中边界节点的速度,来指定离散模型中边界墙的速度,实现边界面速度的传递。对比模型试验结果验证了冲击荷载耦合模拟的可行性,为今后堤坝、码头堆场等加固处理及动力稳定性分析提供一种新的研究手段。

Discrete and continuous coupling numerical simulation of the impact loading

Dynamic compaction and impact rolling have been widely used in hydraulic engineering (e.g. port engineering and dam engineering). The research about complex dynamic characteristics mainly depends on laboratory model tests and engineering experience, while the numerical method was rarely used. Combining the discrete element method (DEM) and finite difference method (FDM), a discrete and continuous coupling model was established to simulate dynamic compaction. The hysteretic damping model of the PFC2D is used in the important area, while the surrounding area is simulated with Mohr-Coulomb model of FLAC2D. According to the force equilibrium principle, the resultant force and bending moment acting on the boundary wall are distributed to the boundary node of continuous model. Due to the fact that the coupled boundary could not bear tensile stress, adjustment is made to transfer the boundary surface stresses, and the velocity of boundary wall is determined by the velocity of boundary node. The numerical results were compared with those of laboratory tests and the feasibility of the coupling simulation was validated, which provides a new method for dynamic improvement and stability analysis of dam and port.