深基坑PCMW工法开挖过程离散元数值模拟分析

摘要

The stability of deep foundation pit is an important engineering problem,in which effective supporting structure is the basis of foundation pit engineering.The discrete element method is employed in this paper,and a modeling and numerical simulation method of foundation pit and supporting structure is proposed.A close-packed discrete element model is used to build the model of initial layers,and the clump model of discrete element is used to build pipe piles with smooth surfaces.A deep foundation pit is taken as an example.The geometrical model can be built using the three-dimensional discrete element software MatDEM3D.The mechanical parameters of elements are determined according to the mechanical properties of soil.In numerical simulations,the soil layers are compacted using a pre-balancing operation,after which the deformation of soil and piles are simulated during the excavation process of foundation pit.The numerical simulation results are compared with the measured monitoring data to evaluate the effectiveness of foundation pit support structures.The discrete element numerical simulation method of foundation pit has potential application prospect in the stability prediction of foundation pit excavation process and the evaluation of the effectiveness of supporting structures.%深基坑稳定性问题是重要的工程问题,其中,有效支护结构是保证基坑工程顺利实施的基础.本文引入离散元法,提出了基坑及支护结构建模和数值模拟方法.采用紧密堆积离散单元构建模型初始地层,引入了离散单元团簇模型来构建表面较为光滑的管桩.以南京某深基坑工程为例,采用三维离散元模拟软件MatDEM3D构建几何模型,并根据土体的力学性质设定相应单元的力学参数.数值模拟中,通过预平衡操作实现土层的压实,进而模拟了基坑开挖过程中土体和管桩的变形.将数值模拟结果与实测监测数据进行了对比分析,评价了基坑支护结构的有效性.这种基坑离散元数值模拟方法在基坑开挖过程的稳定性预判和支护结构的有效性评价上具有潜在的应用前景.