井下煤层气抽采随钻注浆护壁浆液渗流模型

针对随钻注浆护壁浆液渗流过程进行了数学建模，首先建立关于注浆压力、渗透半径和渗透时间关系的偏微分方程，确定了初始条件和边界条件；然后采用隐式差分法得到浆液渗流的有限差分方程；最后判断了方程近似解的收敛性和稳定性，并进行了模拟计算。研究结果表明，浆液压力P0>1.0 MPa时，浆液扩散效果较好，能够达到护壁作用，但P0>1.0 MPa后浆液扩散效果相差不大，这也说明决定浆液渗透效果的关键因素是煤层的渗透率。

Slurry seepage model of grouting while drilling to protecting wall used in underground methane drainage

In terms of the diffusion process in grouting while drilling，a mathematical model for seepage diffusion was developed.Firstly partial differential equations were established regarding the relationship among the grouting pressure，penetration radius and penetration time，and the initial conditions and boundary conditions were determined.Secondly，using implicit difference method，a slurry seepage finite difference equation was obtained.Finally，the convergence and stability of the approximate solution were assessed and the simulations were performed.The results show that when the slurry pressure P0>1.0 MPa，the slurry diffusion effect is better and able to protect drillhole wall.However，there is a little difference after P0>1.0 MPa.This also shows that the key factor that decides the slurry penetration effect is the permeability of the coal seam.The model developed can be used as a theoretical basis for grouting pressure and grouting quantity selection when grouting while drilling is needed in soft coal seams.