水对受力岩石变形破坏宏观力学效应的实验研究

AN EXPERIMENTAL STUDY CONCERNING THE MACROSCOPIC EFFECT OF WATER ON THE DEFORMATION AND FAILURE OF LOADED ROCKS

为了了解水对受力岩石的宏观力学效应,在MTS电液伺服材料试验系统上,对不同饱水度的砂岩、花岗闪长岩、灰岩和大理岩进行了单轴压缩试验,取得了这几种岩石的单轴抗压强度和弹性模量随饱水度变化的定量结果.结果表明,水对受力岩石的力学效应与岩石中的含水状态是密切相关的,自然状态的砂岩、花岗闪长岩浸水后,其峰值强度和弹性模量随饱水度的增加而迅速衰减,当饱水度达到某一定值时,这两种岩石的峰值强度和弹性模量基本稳定下来;文中用函数Y=Aexp(-Bx)+C对实验结果进行了最小二乘法拟合.实验中求得水饱和状态和自然状态砂岩的泊松比并没有明显差异,说明在宏观上水对该种岩石受力变形的作用是各向同性的.通过10^(-5)/s和10^(-4)/s两种不同应变率试验,发现水对受力岩石的力学效应具有时间依赖性,这一特点说明仅从有效应力原理来考虑水对受力岩石的力学效应是不够的,而应考虑应力腐蚀这样复杂的过程.此外,大理岩的试验结果表明,水对受力的碳酸盐类岩石的作用机理是一个值得进一步探讨的问题,它与水对受力的含SiO_2类岩石相比,可能存在差异.

In orler to investigate the macroscopic mechanical effect of water on the deformation and failure of loaded rocks, red sandstone, granodiorite, limestone, and marble with different saturation degree are uniaxially compressed in a servo-controlled material test system and quantitative results concerning the changes of uniaxially compressive strength and elastic modulus with saturation degree are obtained. It is found that the mechanical effect of water on loaded rocks is closely related to the moisture content of rocks. The peak strength and elastic modulus of sandstone and granodiorite decrease rapidly as the saturation degree in the rocks increases from the natural state, and become stable after a definite saturation degree is achieved; these experimental results are fitted by the function Y = Aexp (-Bx)+C using the minimum square multiply. The Possion's ratio of the sandstone in the test shows no distinct difference between specimens in saturated and natural state, and it could be concluded from this result that the effect of water on the deformation of this rock is isotropic: It is also found that the water effect on the loaded rocks is time-dependent through the tests with different strain ratios. This property indicates that it is not adequate to consider the mechanical effect of water on the loaded rocks only from the point of effective stress, and that more complicat-ted processes such as stress corrosion should be taken into account.Finally, it is infered out from the test that the mechanism of water on loaded carbonate rocks is worth further studying. There might be some differences between the mechanisms of water on loaded carbonate rocks and on loaded siliceous rocks.