基于复杂形状离散元/有限元的砂卵地层盾构仿真方法与实验研究

Because of the high strength, the strong corrosion and loose arrangement of the particles in sandy cobble stratum, shield tunneling is meeting some problems such as large wear of cutters and poor stability of the stratum. The finite element method (FEM), which is based on the continuum mechanics, is capable of describing the stress, stain, the deformation of the cutter head and cutters, and so on. The discrete element method (DEM) has a clear advantage in handling the discontinuous natures of the sandy cobble stratum. The purpose of this project is to develop an effective approach which can describe the sandy cobble stratum through 3D DEM and the cutters and cutter head via FEM, while the interaction between the sandy cobble particles and the cutter head as well as the cutters will be computed by the combined discrete/finite element method. Moreover, the corresponding parallel computing software will be developed as well. The mainly research contents of this project are as follows: the discrete element model with complex shapes will be developed for the accurate description of the cobble particles, and the contact algorithm among DEs and the one between DEs and FEs will be proposed; in order to control the model size of the sandy cobble stratum, alternate-replenishing stratum method will be developed; a simulation method for cutter wear and fracture will be presented based on the wear and fracture models of the cutters; a high-performance analysis software will be developed by the cooperatively parallel computation of manycore CPU and GPU, and then the developed models and the software will be further validated by the small experiments of the shield tunneling; the flow behavior of sandy cobble particles, the failure behavior of the cutter will be investigated by simulations. The successful implementation of this project will give a new method for quick and effective investigation of the wear behavior of the cutters and the stratum stability in shield tunneling by simulations.

由于砂卵石地层松散、颗粒强度高、侵蚀性大，盾构施工面临着刀具磨耗大、地层稳定性差等问题。基于连续介质力学的有限元法可很好地分析刀盘刀具的应力、应变和变形等，而离散元法适合描述砂卵石地层的非连续性。本项目采用三维复杂形状离散单元模拟砂卵石地层、有限单元分析刀盘刀具，通过离散元/有限元耦合方法分析刀盘刀具与砂卵石的相互作用，开发并行分析软件。主要内容包括：构建描述砂卵石颗粒真实几何的复杂形状离散单元模型，开发复杂形状离散元间的接触算法和复杂形状离散元/有限元接触耦合算法；提出砂卵石层备份补充法以控制地层模型规模；构建刀具磨损和断裂模型，提出刀具磨损和断裂失效仿真方法；开发多核CPU、GPU协同计算高性能并行软件，并以小型盾构实验验证模型和软件的正确性；仿真研究砂卵石地层盾构时颗粒流动特性、刀具失效机理和特性。本项目的成功实施将为砂卵石地层盾构刀具磨损性能及地层稳定性提供一种快速有效的仿真评价。

由于砂卵石地层松散、颗粒强度高、侵蚀性大，盾构施工面临着刀具磨耗大、地层稳定性差等问题。基于连续介质力学的有限元法可很好地分析刀盘刀具的应力、应变和变形等，而离散元法适合描述砂卵石地层的非连续性。本项目致力于提出了适用于处理卵石-刀具刀盘相互作用的离散元/有限元(等几何)接触耦合方法，开发了岩石材料内聚力本构模型与断裂模拟方法，建立基于内聚力模型的离散元/有限元连结-断裂耦合模型，研究了滚刀作用下岩石破碎特性研究和颗粒材料的流动特性。基于上述理论、方法和模型，开发出了高性能计算程序，并通过实验室实验结果验证了其正确性和有效性。上述成果将为砂卵石、工程机械间相互作用的准确计算、岩石和脆性涂层破碎和岩石颗粒的流动特性研究提供另外一种有效方法。