深部煤层非充分采动下覆岩裂隙场可视化探测研究

Study on visual exploration of fissure field of overlying strata in deep coal seam under subcritical extraction

覆岩采动裂隙分布规律与导水裂隙带高度的探测是煤矿安全开采研究的热点问题之一,对矿井水害防治与瓦斯治理具有重要作用,为获得深埋煤层在非充分采动下覆岩裂隙场分布特征及导水裂隙带的发育高度,以济宁煤田某矿为试验矿井,采用传统经验公式、钻孔冲洗液漏失量观测及钻孔电视观测3种方法,进行了理论计算、定量探测和定性分析。探测结果表明:缓倾斜煤层平均倾角6°、埋深538~595 m、条带式非充分采动下,导水裂隙带高度66.0 m,为采高的23.6倍;垮落带高度8.45 m,为采高3.02倍;覆岩采动裂隙主要为NEE向斜裂缝形式,发育在垮落带与裂隙带下部,主要发育范围为采空区底板以上约33.55 m,约为采高的12倍,占导水裂隙带高度的50.8%;采动覆岩裂隙在裂隙带表现出明显的分层性,裂隙带上部裂隙发育强度与宽度有限,虽具有水文意义,但对采空区地表残余变形影响较小;裂隙带下部裂隙发育强烈,存在多处离层,对地下水渗流和采空区地表残余变形均存在一定程度影响;对比分析表明,3种方法在精度上存在较大差异,钻孔彩色电视观测效果最优,可精确探测岩体内部裂隙分布及其产状;钻孔冲洗液漏失量观测效果次之,可以获得较为精确的数据;传统经验公式精度最差,仅能确定大致范围。

The detection of the overburden mining fracture distribution and the height of water conducting fracture zone are one of the hot issues in the study of coal mine safety subcritical mining,which plays an important role in mine water disaster prevention and gas management.In order to obtain the distribution characteristics of the overburden fracture field and the development height of the water-conducting fracture zone in deep buried coal seam,taking a mine in Jining Coalfield as a test mine the traditional empirical formula,the leakage observation of drilling flushing fluid and the borehole TV observation were used for theoretical calculation,quantitative detection and qualitative analysis.The results show that under the average dip angle of gentle inclination coal seam of 6°,deep buried is 538~595 m and strip-type subcritical extraction,the height of water-conducting fracture zone is 66.0 m,which is 23.6 times of mining height;the height of caving zone is 8.45 m,which is 3.02 times of mining height.Overburden mining fractures are mainly the form of NEE syncline fractures,which develops in the collapse zone and the lower part of the fracture zone.The main development range is about 33.55 m above the floor of the gob,which is about 12 times of the mining height,accounting for 50.8%of the height of the water fracture zone.Mining overburden fractures show obvious stratification in the fracture zone.The fracture development strength and width of the fractures in the upper part of the fracture zone are limited.Although it has hydrological significance,it has little effect on the residual deformation on the surface in the gob.The fracture development in the lower part of the fracture zone develops obviously,and there are many separated layers,which have certain degree of impact on underground water seepage and surface residual deformation in the gob.The comparative analysis shows that there are great differences among the three methods in accuracy.The drilling color television observation has the best effect,which can accurately detect the distribution and occurrence of fractures in the rock mass;the drilling flushing fluid leakage observation has the second effect,which can obtain more accurate data;the traditional empirical formula has the worst accuracy,and only approximate ranges can be determined.