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在陕北榆林小纪汗煤矿实际建井开采过程中发现了煤层为矿井主充水含水层这种特殊的水文地质现象,为对这种特殊现象下底板岩层的力学性质进行分析,对现场底板岩样进行岩石矿物成分测试、岩石膨胀性测试及水作用下岩石强度弱化规律测试等一系列试验研究。研究发现:1)小纪汗煤矿煤层为裂隙含水层,且为矿井主充水含水层,底板岩层长时间受水侵蚀,岩体易于软化、变形,易造成岩层裂隙扩展及其稳定性破坏;2)底板岩样中含蒙脱石、伊利石等膨胀性矿物是底板岩层膨胀变形的微观影响因素;3)底板岩样浸水膨胀变形经过急速膨胀—变形缓慢—变形结束3个阶段,岩样浸水2 h内的膨胀变形已占总变形量73.3%,浸水2~12 h,变形量占总变形量的24.7%,浸水12 h后,试样基本不变形;4)岩样与水作用后其单轴抗压强度、弹性模量、劈裂抗拉强度随饱水时间的延长、含水率的增大而不断降低,总体呈指数关系递减;5)岩样浸水12 h后,岩石单轴抗压强度、弹性模量及抗拉强度降低值占总衰减值分别为71.6%,72.3%和65.4%,煤层裂隙水对底板岩层的侵蚀软化作用明显。
During the actual construction of the Xiajihan coalmine in Yulin, Northern Shaanxi Province, a special hydrological and geologic phenomenon was found in which the coal seam was the main water-filled aquifer in the mine. In order to analyze the mechanical properties of the floor rock under this special phenomenon, Rock samples for rock mineral composition testing, rock expansibility test and the law of rock strength under weakening water test and a series of experimental study. The results show that: 1) The coal seam of the Xiajihan coal seam is a fissure aquifer, which is the main water-filled aquifer in the mine. The floor rock is eroded by water for a long period of time. The rock mass is easy to soften and deform, which easily leads to the expansion of the fissure of the rock formation and its stability destruction. 2) In the basement rock samples, the expansive minerals such as montmorillonite and illite are the micro-factors that affect the expansion and deformation of the floor rock; 3) The swelling and deformation of the base rock samples after rapid expansion, slow deformation and the end of deformation, After 2 hours immersion, the total deformation amount accounted for 73.3% of total deformation and immersed in water for 2 ~ 12 hours. The deformation amount accounted for 24.7% of the total deformation amount. After immersion for 12 hours, the specimen did not deform basically. 4) The uniaxial compressive strength, elastic modulus and splitting tensile strength decrease with the increase of water-holding time and moisture content, and decrease with exponential relationship. 5) The values of compressive strength, elastic modulus and tensile strength decrease 71.6%, 72.3% and 65.4%, respectively. The fissure water of coal seam plays an important role in erosion and softening of floor rock.