破碎顶板切顶留巷采空区顶板垮落特征试验研究

Study on sandstone roof caving character in gob-side entry retaining by roof cut and pressure relief

垮落带内含有的坚硬厚砂岩冒落性差,易在沿空留巷实体煤帮的支撑下形成三角板结构,随着上覆岩层的断裂和应力传递,造成沿空巷道采动压力影响剧烈。基于禾草沟二号煤矿1105工作面厚砂岩顶板设计10种不同间距切顶钻孔试验方案进行现场试验,并在相应区域对沿空侧采空区岩层垮落特征进行监测。试验表明,在未爆破区域和爆破区域,采空区顶板岩石垮落时间随炮孔间距的增大而增大,爆破区域沿空侧采空区垮落矸石充填满巷帮时间为非爆破区域的0.4倍,沿空巷道稳定速度更快。在未爆破区域和爆破区域中,沿空侧巷帮垮落矸石块度随切顶钻孔间距的增大而增大,未爆破区域垮落矸石块度最大为1.33 m,爆破区域垮落矸石块度最大仅为0.36 m。在设计方案中,巷道顶板压力与巷道顶底板位移均随切顶钻孔间距的增大而增大,相同间距钻孔,爆破区域巷道顶板压力与巷道顶底板位移均明显小于非爆破区域。根据试验结果,在设计方案中,钻孔间距400 mm、间隔爆破时,切顶效果较好,沿空侧采空区顶板冒落性好、接顶速度快、沿空巷道动压显现较弱。

Hard and thick sandstone in caving areas is not likely to fall and tends to form triangular structure with integrated coal rib support in gob-side roadways. As overlying strata breaks and the stress transfers, dynamic mining pressure affects gob-side roadway dramatically. Field experiment was held based on ten designed different spacing roof cutting and hole drilling schemes for thick sandstone roof of 1105 working face of No. 2 Coal Mine in Hecaogou village. Stratum caving character was monitored along the gob-side roadway. The experiment showed that in blasting zones and no-blasting zones, time for goaf top rocks to fall increases with lengthening of hole spacing. Collapsed gangue takes 0. 4 as much time to fill up roadway wails in blasting zones as it does in no-blasting zones, and gob-side roadway in blasting zones stabilizes faster. In both blasting zones and no-blasting zones, lumpiness of collapsed gangue from gateway walls increases with the increase of distance between roof cutting boreholes. Maximum lumpiness of collapsed gangue in no-blasting zones is 1. 33 m while the lumpiness in blasting zones can only reach 0. 36 m. According to the scheme, both pressure on roadway top and displacement of top-floor enlarge wtUa the mcrea^e ol u space is equal, pressure on roadway top and displacement of top-floor in blasting zones are observably smaller than those in no-blasting zones. Based on the test result, interval blasting with the borehole space of 400 mm is the optical scheme for effective roof cutting, better caving along gob-side roadway, fast roof-contacted filling and weak dynamic pressure on gob-side roadway.