库岸边坡水-岩作用对节理砂岩力学特性影响研究

三峡库区蓄水之后,库水位在145 m和175 m之间呈周期性的升降变化趋势,考虑消落带岩体的实际赋存环境,设计进行了考虑水压力升降变化和浸泡-风干循环的水-岩作用试验,分析了水-岩作用的劣化效应。研究结果表明:(1)节理砂岩抗压强度、变形模量随节理倾角的变化呈先减小再增大的U形变化规律,在周期性水-岩作用下,节理砂岩的抗压强度和变形模量劣化效应明显,其中前5次水-岩作用导致的劣化效应尤为显著;(2)水-岩作用使得节理砂岩的各向异性力学特性逐渐减弱,其中,抗压强度的各向异性度从1.56降低到1.41,变形模量的各向异性度从1.53降低到1.33;(3)水-岩作用不仅使得岩体整体力学性质劣化,也逐渐改变节理岩体的破坏模式,导致不同倾角节理砂岩力学特性劣化趋势存在明显差异,其中,在节理倾角为0°和90°附近时,水-岩作用导致的劣化幅度相对较大,而节理倾角为60。左右时的劣化幅度相对较小。研究结果可为库岸边坡的长期变形稳定分析提供较好的参考。

Study on influence of water-rock interaction of reservoir bank slope on mechanical characteristics of jointed sandstone

After the water impoundment of the area of Three Gorges Reservoir,the reservoir water level periodically fluctuates between 145 m and 175 m,for which the actual occurrence environment of the rock mass in the fluctuating zone is considered,and then an experiment on the water-rock interaction under the consideration of the water pressure fluctuation and the cycle of immersion-air drying is designed and carried out for analyzing the degradation effect of water-rock interaction.The study result shows that(1)The changes of the compressive strength and deformation modulus of jointed sandstone exhibit the U-typed changing laws,i.e.decreasing at first and then increasing along with the change of the joint inclination,while the degradation effect on the compressive strength and deformation modulus of the jointed sandstone is obvious under the periodical water-rock interaction,in which the degradation effects caused by the first 5 water-rock interactions are particularly significant.(2)The water-rock interaction makes the anisotropic mechanical properties of the jointed sandstone gradually weaken,among which the degree of anisotropy of the compressive strength decreases from 1.56 to 1.41 and the degree of anisotropy of the deformation modulus decreases from 1.53 to 1.33.(3)The water-rock interaction not only makes the overall mechanical properties of the rock mass degrade,but also gradually changes the failure mode of the jointed rock mass,and then leads to obvious difference among the degradation trends of the mechanical properties of the jointed sandstones with different inclinations,in which the degradation amplitude caused by the water-rock interaction is relatively larger when the joint inclination is near 0°and 90°,while the degradation amplitude is relatively smaller when the joint inclination is about 60°.The study result can provide a better reference for the analysis on the long-term deformation stability of the reservoir bank slope.