Experimental proportioning design.

Gob-side entry retention (GER) has been successfully advanced and implemented for several years. Notably, strong economic returns have been realised for different thicknesses of coal seams under near-horizontal and gently inclined conditions. However, implementing gob-side entry retention under the conditions of high dip angle or steeply inclined coal seam has always been difficult. This paper systematically introduces the material and construction processes of flexible formwork GER. Engineering practice, theoretical calculations and indoor test analysis were used to propose an independently designed and developed special-shaped flexible formwork concrete wall with a width of 1.2 m, a strength of C30 and an inclination angle of 20°. This wall was then used to investigate the GER technology in the No. 31342 working face of the Dachiba Coal Mine. The findings reveal that the strength of the developed coal solid waste flexible formwork concrete fulfils the design requirements, and the residual strength and healing capacity are superior to that of ordinary concrete. The design of the supporting parameters of flexible formwork GER was satisfactory in the No. 31342 working face of the Daichiba Coal Mine. The overall deformation of the roadway is small, and a decent effect is obtained with respect to retaining the roadway. Hence, the technical challenge of enacting GER in medium-thick coal seams with a high dip angle under the filling and supporting modes has been resolved successfully.

沿空留巷（Gob-side entry retention, GER）技术已成功推广应用多年，在近水平、缓倾斜煤层的不同厚度条件下均取得了可观的经济效益。然而，在大倾角或急倾斜煤层条件下实施沿空留巷技术始终是行业难题。本文系统介绍了柔性模板沿空留巷的材料与施工工艺。研究结合工程实践、理论计算与室内试验分析，提出并自主研发了一款宽度1.2m、强度等级C30、适配倾角20°的异形柔性模板混凝土墙体，并将其应用于大池坝煤矿31342工作面的沿空留巷技术研究中。研究结果表明：研发的煤固体废弃物柔性模板混凝土强度满足设计要求，其残余强度与自愈能力均优于普通混凝土。大池坝煤矿31342工作面的柔性模板沿空留巷支护参数设计合理，巷道整体变形量小，留巷效果良好。本次研究成功解决了大倾角中厚煤层采用充填支护模式实施沿空留巷的技术难题。