Analysis of the formation process of the covered karst ground collapse induced by groundwater changes based on the coupled LBM-DEM numerical simulation at micro scale
To investigate the hydraulic characteristics and soil behaviors during the formation of covered karst ground collapse induced by the groundwater changes,a 2D fluid-solid coupling model was developed based on discrete element method and lattice Boltzmann method.This model utilizes the linearly interpolated bounce-back scheme of Bouzidi and the momentum exchange method,allowing for the simulation of the formation of covered karst ground collapse from a microscopic perspective.Using the fluid-solid coupling model,an exploratory study was conducted to simulate the formation of covered karst ground collapse induced by a decrease in the hydraulic head of confined aquifers.Simulation results indicate that when the water level of a confined aquifer declines,the groundwater flow mainly affects the particles located above a cave opening and produces a downward force on the surrounding soil.When soil particles spall,the hydraulic heads at the positions of the spalled soil particles drop sharply.This results in a significant increase in the hydraulic gradient,causing the groundwater force on internal particles to sharply increase as well.As a result,the upper particles lose stability due to the combined force of groundwater dragging and gravitational force,which can lead to a gradual acceleration process of collapse.The research results provide valuable insights into the understanding of covered karst ground collapse formation induced by the groundwater changes.
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