深部煤系页岩吸水及软化效应微观机理研究

Study on micromechanism of water absorption and its softening effect on shale rock in deep coal measures

采用自主研发的深部软岩水理作用智能测试系统,对采自辽宁沈阳大强煤矿的页岩样品进行了不同水压条件下的吸水实验,并对吸水前后的页岩试样进行了X射线衍射实验、压汞实验、电子扫描电镜实验以及单轴压缩实验。研究结果表明:①页岩试样的吸水率随吸水时间增长而显著增加,而吸水速率则随吸水时间增长显著下降,吸水曲线均可以通过指数函数拟合;②不同水压条件下页岩试样吸水能力差异显著,水压能显著提高页岩试样的吸水率;③页岩试样的吸水能力与黏土矿物含量之间存在正相关关系,黏土矿物特别是伊利石在页岩试样的吸水过程中起着重要作用;④页岩试样的吸水能力与有效孔隙率之间存在负相关关系,这种关系的内在原因与其微观孔隙结构密切相关;⑤水化页岩试样的单轴抗压强度与其含水率之间呈线性负相关关系,吸水后岩石内部孔隙率的增加是导致页岩试样吸水之后强度衰减的重要原因之一。

Water absorption experiments under different water pressures were carried out on a series of shale samples collected from Shenyang of Liaoning province using a self-developed hydrophilic experimental system.At the same time,X-ray diffraction,high pressure mercury intrusion,scanning electron microscope and uniaxial compression experiments were performed on the shale rock samples before and after water absorption.The experimental results are as follows:①the absorbed water increases with time while the water absorption rate decreases with time and water absorption curves can be well fitted by an exponential function;②the water absorption capacities of the shale samples under different water pressures are remarkably different which are suggesting that water pressure can significantly increase the water absorptivity;③the water absorption capacity and the clay mineral content are positively correlated which indicates that the clay minerals,specifically illite,plays an important role in water absorption process of the shale samples;④the water absorption capacity and the effective porosity are negatively correlated and the reasons are closely related to a micro-structural perspective;⑤the uniaxial compression strength(UCS)of the hydrated shale samples is negatively correlated with their water content and the increase of the porosity after water absorption may be an important reason for decreased strength of the hydrated shale samples.