厚煤层沿空留巷变形漏风机制及多元协同防治技术

Deformation and air leakage mechanism of gob-side entry retaining and multiple collaborative prevention and control technology in thick coal seam

为解决厚煤层沿空留巷墙体变形机理及采空区漏风流场不清、瓦斯防治效果不佳的问题,以山西沁城煤矿20107工作面为工程背景,采用力学建模、理论分析研究了沿空留巷顶板断裂位置对应力集中及传播路径的控制作用,并指出断裂线位于留巷外侧时,可有效转移支撑应力并卸压,并提出了分段压裂切顶关键位置的计算方法。采用单元法实测,从采空区漏风量分布及留巷漏风通道两方面,揭示了沿空留巷采空区漏风流场及瓦斯浓度分布规律,进而提出了沿空留巷采空区瓦斯多元防治技术,即采用定向钻孔分段压裂切顶卸压-强化瓦斯抽采超前协同共治为主,弱化转移顶板来压避免墙体变形产生裂隙漏风的同时提高采空区瓦斯抽采效率;采用硅酸盐复合材料对已有墙体裂隙发育区(顶板交界处、插管外壁周围)进行喷涂堵漏,封堵留巷漏风通道;辅以留巷插管参数优化及控风降压,进一步减小采空区漏风及瓦斯涌出,并通过现场考察验证。研究结果表明:①20107采空区漏风以运输巷进风流正压漏入为主、回风侧以高浓瓦斯漏入沿空留巷为主,工作面倾向0~36 m区段正压漏风量332.84 m^(3)/min,占工作面总体漏入采空区风量(572.15 m^(3)/min)58.17%;留巷走向54~108 m区段留巷漏入风量408.45 m^(3)/min,占采空区总体漏入沿空留巷风量(469.01 m^(3)/min)87.09%;②优化后,裂隙带定向钻孔(压裂孔+抽采孔)平均瓦斯抽采纯量为7.46 m^(3)/min,压裂切顶后留巷墙体变形、裂隙控制大幅改善,沿空留巷平均瓦斯体积分数由原0.59%逐渐降至0.34%,实现工作面高效达产。

In order to solve the problems of wall deformation mechanism of gob-side entry retaining,unclear air leakage flow field in goaf and poor gas control effect in thick coal seam,taking 20107 working face of Qincheng Coal Mine in Shanxi Province as the engineering background,mechanical modeling and theoretical analysis are used to study the influence of roof fracture position on stress concentration and propagation path in gob-side entry retaining.It is pointed out that when the fracture line is located outside the retaining roadway,the support stress can be effectively transferred and the pressure can be relieved.The calculation method of the key position of roof cutting by staged fracturing is proposed.By means of unit method measurement,the distribution law of air leakage flow field and gas concentration in goaf of gob-side entry retaining is revealed from two aspects of air leakage volume distribution in goaf and air leakage channel in gobside entry retaining,furthermore,the multiple prevention and control technology of goaf gas in gob-side entry retaining is put forward,that is,the directional drilling staged fracturing roof cutting pressure relief-strengthening gas drainage advanced collaborative governance,weakening the transfer of roof pressure to avoid wall deformation and fracture air leakage,and improving the efficiency of goaf gas drainage.Silicate composite materials were used to spray and plug the existing wall crack development area(at the junction of the roof and around the outer wall of the intubation)to plug the air leakage channel of the roadway.With the optimization of the intubation parameters of the retaining roadway and the air volume ratio of the working face,the air leakage and gas emission in the goaf are further reduced,and verified by field investigation.The results show that:①In 20107,the air leakage in 20107 goaf is mainly caused by the positive pressure leakage of the inlet air flow in the belt roadway,and the return air side is mainly caused by the leakage of high concentration gas into the gob-side entry retaining.The positive pressure air leakage in the 0-36 m section of the working face is 332.84 m^(3)/min,accounting for 58.17%.The leakage air volume of the 36-108 m section of the retaining roadway is 408.45 m^(3)/min,accounting for 87.09%.②After optimization,the average gas drainage purity of directional drilling(fracturing hole+pumping hole)in fracture zone is 7.46 m^(3)/min,and the average gas concentration in gob-side entry retaining is gradually reduced from 0.59%to 0.34%.After fracturing and roof cutting,the deformation and fracture control of the retaining wall are greatly improved,and the efficient production of the working face is realized.