含水率对细粒长石岩屑砂岩蠕变特征影响试验研究

Experimental study on the effect of moisture content on creep characteristics of fine-grained feldspar lithic sandstone

煤矿采空区储水库建立过程中,由水的运移引发各种水-岩作用,促使水库坝体长期强度发生变化。为了探究含水率对地下水库坝体蠕变特征影响,以西部梅花井煤矿4-2#煤层底板细粒长石岩屑砂岩为研究对象,通过自制无损浸水加湿设备制取含水率为0%,2%,6%和11%的岩样,采用机械分级加载分别对不同含水率岩样进行三轴蠕变试验,并监测岩样蠕变过程中声发射信号。研究发现随着含水率的增加,岩样蠕变各阶段持续时间显著减少,岩样达到稳定状态所需要时间也相应缩短,同时,岩样的极限应变量呈线性增加,岩样的长期强度呈指数降低,不同含水率长期强度的值与单轴抗压强度的比值为0.3~0.5。声发射RA值监测结果表明,随着含水率的提高,岩样内部拉张裂纹数量明显增加。b值监测结果表明含水率的增加改变了岩石内部结构,岩石试件内部裂隙发育期间,声发射事件普遍比较微弱,随着含水率的增加,试件内部小裂隙比较发育。

During the establishment of reservoir in goaf of coal mine,the long-term strength of reservoir dam is weakened by various water-rock interactions are triggered by water movement,which weakens.In order to explore the influence of water content on creep characteristics of groundwater reservoir dam body,with the fine-grained feldspar lithic sandstone in the floor of coal seam 4-2#in Meihuajing Coal Mine as the research object,the rock samples with water content of 0%,2%,6%and 11%have been respectively prepared by self-made non-destructive water immersion humidification equipment,and triaxial creep tests have been carried out on the rock samples with different water content through mechanical graded loading.Then,acoustic emission signals have been monitored during creep of rock samples.It has been found that with the increase of water content,the duration of creep stages of rock samples decreases significantly,and the time required for rock samples to reach a stable state is shortened correspondingly.At the same time,the ultimate strain of rock samples increases linearly,the long-term strength of rock samples decreases exponentially,and the ratio of long-term strength of different water content to uniaxial compressive strength is 0.3~0.5.The results of acoustic emission RA monitoring have shown that the number of tension cracks in rock samples increases obviously with the increase of water content.The value of b shows that the increase of water content changes the internal structure of rock,and the acoustic emission events are generally weak during the development of internal cracks in rock specimens.With the increase of water content,the small cracks develop in rock samples.