煤层底板砂岩含水层水文地质特征的分布式放水试验探查研究

Research on distributed dewatering test based on the hydrogeological characteristics of sandstone aquifer in coal seam floor

为了查明宁东煤田煤层底板宝塔山砂岩含水层的水文地质特征,在国家能源集团宁夏煤业有限责任公司石槽村煤矿2个不同的区域开展了分布式放水试验,2个阶段的放水试验均包括了单孔和多孔放水试验,计算的渗透系数平均值分别为0.219~0.301、0.024~0.029 m/d,单位涌水量平均值分别为0.079、0.012 L/(s·m),影响半径分别约为700、750 m。通过放水试验,查明宝塔山砂岩含水层的厚度约为60 m,岩性为粗砂岩,局部夹薄层砂质泥岩和泥岩;含水层渗透性和富水性均较弱,且存在不均一性,但是由于宝塔山砂岩含水层位于下组煤底板,研究区下组煤承压均在3 MPa以上;含水层地下水水温约为41℃,下组煤采掘活动面临一定的热害影响;宝塔山砂岩含水层具有较好的可疏性,疏水降压是底板砂岩水害防控最佳措施。通过放水试验进一步查明了宝塔山砂岩含水层的水文地质特征,补充了抽水试验未能查明的水文地质条件,其探查结果可以作为煤层底板砂岩水害防控的依据。

In order to find out the hydrogeological characteristics of Baotashan sandstone aquifer in coal seam floor in Ningdong coalfield,distributed dewatering tests were carried out in two different areas of Shicaocun coal mine.The dewatering tests of the two stages include single-borehole and multi-borehole dewatering tests,and the average calculated permeability coefficient was 0.219~0.301 m/d and 0.024~0.029 m/d,the average water inflow per unit was 0.079 L/(s·m)and 0.012 L/(s·m),and the influence radius was about 700 m and 750 m,respectively.It is found that the thickness of Baotashan sandstone aquifer was about 60 m through the dewaetering test,and the lithology was coarse sandstone with thin sandy mudstone and mudstone.The permeability and water richness of the aquifer were weak and non-uniform,but because the Baotashan sandstone aquifer was located under the lower group coal seam,the water pressure of lower coal group in the study area was above 3 MPa.The groundwater temperature of the aquifer was about 41℃,and the coal mining activities of the lower group coal workface faced a certain thermal damage.Baotashan sandstone aquifer had good drainage property,the method of water drainage and pressure reduction was the best measure to prevent and control water hazard of sandstone aquifer under the coal seam.The hydrogeological characteristics of the sandstone aquifer in Baotashan were further identified through water discharge tests,which supplemented the hydrogeological conditions that could not be identified through pumping tests,and the exploration results could serve as a basis for the prevention and control of water hazard in coal seam floor sandstone.