饱水对煤系地层岩石力学性质影响的试验研究

EXPERIMENTAL STUDY OF EFFECT OF WATER-SATURATED STATE ON MECHANICAL PROPERTIES OF ROCK IN COAL MEASURE STRATA

为研究饱水对煤系地层岩石力学性质的影响,在自然和饱水状态下,利用RMT–150B岩石力学系统对砂岩、砂质泥岩和泥岩进行巴西劈裂、单轴压缩和常规三轴压缩试验。试验结果表明:3种岩石的平均吸水率为0.241%～0.482%,吸水率与时间的关系可以用对数函数进行拟合;饱水后对3种岩石的强度和变形特征均有不同程度的影响,泥岩表现最为明显,其次是砂质泥岩和砂岩,抗拉强度的软化系数为0.40～0.92;单轴抗压强度的软化系数为0.58～0.94,弹性模量的降低系数为0.58～0.95,变形模量的降低系数为0.68～0.94,泊松比的降低系数为1.08～1.11;三轴压缩峰值强度的软化系数K与围压σ3大致成正相关,表明饱水状态下试样峰值强度对围压的敏感度大于自然状态下试样峰值强度对围压的敏感度;饱水对3种岩石试样的黏聚力均有不同程度降低,降低幅度为20.6%～67.0%,而摩擦因数大致保持不变,表明黏聚力是一个结构参数,摩擦因数是一个材料参数。

In order to study the effect of water-saturated state on mechanical properties of rock in coal measure strata, Brazilian Split test, uniaxial and pseudo-triaxial compression experiments are carried out to investigate sandstone, sandy mudstone and mudstone specimens under natural and water-saturated state by rock mechanics test equipment RMT - 150B. The results are as follows： the average rate of water absorption of sandstone, sandy mudstone and mudstone is between 0.241% and 0.482%： water absorption rate with respect to time can be fitted with logarithmic relationship. Different influences of the strength and deformational character among these three types of rocks are found after reaching water-saturated state, mudstone performs most obviously, then comes the sandy mudstone and the sandstone. The softening coefficient of tensile strength is roughly between 0.40 and 0.92： softening coefficient of uniaxial compression strength is between 0.58 and 0.94; reducing coefficient of elastic modulus is between 0.58 and 0.95： reducing coefficient of deformational modulus is between 0.68 and 0.94： and the reducing coefficient of Poisson ratio locates in the range of 1.08 - 1.11. The softening coefficient of peak strength measured by triaxial compression tests-K and the confining pressure-σ3 are approximately positive correlated. It is indicated that the sensitivity of peak strength to the confining pressure in water-saturated state is greater than that in natural state. Water-saturated state can reduce the cohesion of these rock specimens; the percentage of reducing lies between 20.6 % and 67.0%. On the other hand, intemal friction coefficient almost keeps in the same level; it is shown that the former coefficient is a structural parameter and the latter is a material parameter.