Study On Grouting Diffusion Mechanism Of Loose Bottom Aquifer In Guotun Coal Mine

In recent years,more than one hundred wellbore deflection accidents have occurred in the well shaft of the thick loose layer coal mine in East China,which has seriously affected the safety of coal mine production and downhole personnel.This type of wellbore deflection is caused by the large amount of water in the bottom aquifer of the loose layer(abbreviated as "bottom aquifer").The three wellbore deviations in the Guotun coal mine located in the Juye coalfield are typical cases.How to control the further deflection of the wellbore,For mine safety production is of great significance.Based on the analysis of the hydrogeological characteristics of Loose bottom aquifer around wellbore in Guotun Coal Mine,this paper uses the drilling water pressure test method to obtain the hydrogeological parameters of the grouting interval and analysis most distant observation period W1 of the main bore hole grouting "take slurry" cause of the accident due to the observed large holes surrounding formation permeability due to differences with the rest of the formation.Through the analysis of the loose layer grouting process,a conceptual model and a mathematical model for 3 holes for wind detection,the main W1 hole "bottom aquifer" grouting were established,and multi-physics coupling methods such as material diffusion,Darcy flow,and solid mechanics were used to Comsol.Comsol Multiphysics software is used as a tool to simulate the distribution of slurry dispersion,pressure field,flow field,and stress field.The mechanism of slurry diffusion during grouting and the stress on the wellbore under grouting pressure are analyzed.The simulation validates the past "Slurry" process.Research indicates:(1)The shape of the slurry diffusion began to appear circular.Under the influence of moving water conditions,the slurry gradually transitioned to droplets,and the slurry diffusion rate gradually decreased with time.(2)The pressure distribution of the model shows that the pressure at the orifice of the grouting hole is the largest and gradually approaches the boundary pressure at the inlet and outlet as the distance increases.(3)Affected by the grouting pressure,the stress and displacement of the formation around the grouting hole are the largest,and the maximum stress of the wellbore is located near the grouting hole at the bottom of the wellbore,and the wellbore displacement gradually decreases from top to bottom.(4)Influenced by the difference in formation permeability coefficient,the numerical simulation results simulated the phenomenon of mud spillage in the observation hole at the farthest position of the main W1 hole,and verified the correctness of the analysis.