煤层底板区域注浆浆液扩散数值模拟及影响因素分析

Numerical simulation of grout diffusion under coal seam floor and analysis of influencing factors

地面高压超前区域注浆已成为煤矿水害防治的首选工程方法,注浆浆液扩散机理受到普遍关注,且分支孔间距设计多依赖现场经验,具有一定的盲目性,制约着工程效果及效益。基于淮北煤田恒源煤矿注浆现场实际工况,利用COMSOL Multiphysics软件,开展地面定向钻煤层底板区域高压注浆浆液扩散数值模拟研究及浆液扩散影响因素分析,探讨地面高压注浆浆液扩散机理。结果如下:(1)煤层底板石炭系太原组第三薄层灰岩(简称三灰)裂隙发育,通过模拟发现,8~12 MPa高压注浆时很可能发生劈裂作用,期间渗透系数增大4~5个数量级。(2)不考虑重力影响时,以分支孔为中心,浆液向周边扩散距离相等,且在分支孔附近,浆液浓度较大,体积分数达20%以上;考虑重力作用时,水平向浆液扩散范围相对增大,垂向上浆液主要向下扩散,表现为“上短下长”。(3)浆液扩散模拟得出,扩散范围为41.2 m;浆液扩散范围现场实测显示,扩散范围为38.3~44.0 m,浆液扩散现场实测验证了扩散模型的正确性。(4)浆液扩散范围与浆液相对密度、静水压力、浆液动力黏度、浆液屈服强度及孔隙率呈负相关,与裂隙隙宽、渗透系数呈正相关。其中浆液相对密度越小,其扩散范围响应越明显;随动力黏度增加,扩散范围减小得越来越慢。研究成果可为煤系底板水害区域注浆治理工程合理设计提供参考,具有较好的参考应用价值。

Ground high-pressure advanced regional grouting has become the preferred engineering method for the prevention and control of water disasters in coal mines.The diffusion mechanism of grout has received widespread attention,and the design of branch hole spacing mostly relies on the on-site experience,which has a certain degree of blind-ness and restricts the effectiveness and efficiency of the project.Based on the actual working conditions of grouting site in Hengyuan Coal Mine,Huaibei Coalfield,the numerical simulation was performed with the COMSOL Multiphysics software for the high-pressure grout diffusion in the floor area of the ground directional drilling coal seam,the influen-cing factors of grout diffusion were analyzed,and the mechanism of ground high-pressure grout diffusion was discussed.The results are as follows:(1)Fractures are developed in the third thin layer of limestone in the Carboniferous Taiyuan Formation(hereinafter referred to as“the third limestone layer”)of the coal seam floor.It is found through simulation that the fracturing effect is likely to occur during 8-12 MPa high-pressure grouting,during which the permeability coeffi-cient increases by about 4 orders of magnitude.(2)Without considering the influence of gravity,the grout diffusion dis-tance to the periphery is equal with the branch hole as the center,and the grout density is large near the branch hole,with the volume fraction more than 0.2.When the gravity is considered,the horizontal grout diffusion range is relatively in-creased,and the grout mainly diffuses downward vertically,which is“short up and long down”.(3)The grout diffusion simulation shows that the diffusion range is 41.2 m.Definitely,the field grout diffusion range is measured to be 38.3-44.0 m,which verifies the correctness of the grout diffusion model.(4)The range of grout diffusion is negatively correl-ated with the relative density,hydrostatic pressure,dynamic viscosity,yield strength and porosity of grout,and posit-ively correlated with the width of fracture and permeability coefficient.Specifically,the smaller the relative density of grout is,the more obvious the response of its diffusion range is.With the increase of dynamic viscosity,the diffusion range decreases more and more slowly.The research results could provide a reference for the reasonable design of the grouting treatment project in the water hazard area of the coal measures floor,with good reference and application value.