裂隙煤体注浆浆液扩散规律及变质量渗流模型研究

Grouting fluid diffusion law and variable mass seepage model for fractured coal

研究煤岩裂隙中浆液扩散过程及降渗规律对于强化瓦斯抽采钻孔封孔效果具有重要意义。首先通过对注浆裂隙煤体内部质量变化进行分析,推导浆液封堵裂隙质量守恒方程及浆液流动方程;根据浆液对煤体裂隙结构影响推导了裂隙和渗透率变化方程,构建了浆液对裂隙煤体的堵漏降渗的变质量渗流模型。其次,利用注浆实验系统对裂隙煤样开展注浆试验,对注浆前后煤样分别进行CT扫描观测以及渗透率实验测定;最后,在理论模型的基础上,根据实验条件确定数值模拟初始条件及边界条件,对裂隙煤体注浆浆液扩散和降渗规律开展了数值模拟研究,结果表明:建立的基于裂隙煤体注浆的变质量渗流模型较好地反映浆液颗粒沉积过程对煤体裂隙结构及渗透率的影响;模型计算的浆液扩散与渗透率变化规律与试验结果吻合较好,验证了模型的合理性;在浆液渗流扩散作用下,煤体裂隙内浆液颗粒逐渐扩散并沉积,裂隙不断被充填,导致裂隙煤体渗透率不断下降。研究成果为定量分析注浆浆液颗粒运移规律、强化抽采钻孔封孔效果提供了新的思路。

It is an important precondition to study the process of grouting fluid diffusion and the law of reducing seepage in coal rock fractures for improving the holes sealing quality and the gas extraction efficiency.Firstly,by analyzing the internal mass variation of fractured coal samples,the mass conservation equation and continuity equation of grouting fluid sealing fractures are derived.The permeability variation model is derived based on the influence of grouting fluid on coal void structure,building the variable mass seepage model for plugging fractures and reducing seepage.Secondly,the grouting experiment system is used to conduct grouting experi-ments on fractured coal samples,and CT scanning observations and permeability experiments are respectively performed for coal samples before and after grouting.Finally,based on the theoretical model,the numerical simulation initial values and boundary conditions are determined according to the experimental conditions.The numerical simulation study of the cracking law shows that the established variable mass seepage model based on fractured coal body grouting better reflects the influence of grouting fluid particle deposition process on coal fracture structure and permeability.The grouting fluid diffusion process and the law of reducing seepage for fractured coal samples are studied by using numerical simulation.The study results indicate that the variable mass seepage model for grouting fluid in fractured coal can generally reflect the influence of particles sediment on the fractured coal and permeability,and the numerical simulation result is in good agreement with the experimental results,which verifies the correctness of the model.Under the action of seepage and diffusion,the grouting fluid particles in the coal body cracks gradually diffuse and deposit,and the fractures are continuously filled,resulting in the continuous decrease of the permeability of the fractured coal.The research results provide a new idea for the quantitative analysis of the migration law of grouting fluid particles and strengthening the sealing effect of gas extraction boreholes.