Fluid-solid coupling is a common phenomenon in the studies of granular materials, geotechnical engineering and so on. Based on a multiphase fluid model in the framework of lattice Boltzmann method (LBM) and the discrete element method (DEM), a multiphase fluid-solid coupling algorithm of LBM-DEM is proposed, where the coupling module is developed on the basis of two open-source codes, Palabos and Yade. The feasibility and accuracy of the algorithm are validated through three classical fluid-solid coupling examples: a single sphere settling in a fluid, a sphere falling into a fluid from the air and two spheres colliding with each other in fluid. Then two complex phenomena in geotechnical engineering, transient-state flow and debris flow, are simulated. The results indicate that the LBM-DEM coupled method has strong advantages in the numerical simulation of complex fluid-solid coupling problems. It can accurately reveal the fluid-solid interaction mechanisms, physical & mechanical behaviors and failure process at both macroscopic and mesoscopic scales. Furthermore, from the numerical simulation results, the process of debris flow can be divided into three stages: steady seepage stage, startup stage and flow stage of the fluid-solid mixture.

流固耦合是颗粒材料，岩土工程等研究中的普遍现象。基于格子玻尔兹曼法（LBM）和离散元法（DEM）框架下的多相流体模型，提出了LBM-DEM的多相流固耦合算法，在此基础上开发了耦合模块开源代码，Palabos和Yade。通过三个经典的流固耦合示例验证了该算法的可行性和准确性：单个球体在流体中沉降，一个球体从空中掉入流体中，两个球体在流体中相互碰撞。然后，模拟了岩土工程中的两个复杂现象，即瞬态流和泥石流。结果表明，LBM-DEM耦合方法在复杂的流固耦合问题的数值模拟中具有很强的优势。它可以在宏观和介观尺度上准确揭示流体-固体相互作用的机理，物理和机械行为以及破坏过程。此外，从数值模拟结果来看，泥石流的过程可以分为三个阶段：固液混合的稳态渗流阶段，启动阶段和流动阶段。