饱水-失水循环作用下岩石劣化特性试验研究

合徐高速公路位于江淮地区,夏季周期性的降雨作用使得合徐高速公路下覆浅埋岩层长期处于被雨水饱和-失水-再饱和的交替过程。为研究江淮地区泥岩和砂岩在水岩相互作用下的劣化特性,对取自合徐高速公路浅埋地层的泥岩和砂岩试样进行了抗剪、抗压强度实验以及电镜扫描实验,从宏观和微观的角度共同揭示了不同饱水-失水周期作用下岩石的孔隙结构与岩石强度软化的对应关系及相互映证规律。实验结果表明:水岩相互作用对泥岩和砂岩的抗剪、抗压强度参数及孔隙参数影响显著。岩石内聚力、内摩擦角随循环次数的增加而迅速衰减,当循环次数达到某一值之后,两种岩石的抗剪、抗压强度参数基本稳定。孔隙的数量、总面积、最大孔隙的面积、直径以及岩石表面孔隙率均随着循环次数的增加而增加。基于实验结果,探讨了水岩相互作用对岩石特性影响的劣化机制,为研究岩石劣化特性以及合徐高速公路工程稳定性提供了依据。

Experimental study of rock deterioration characteristics under saturated-loss cycles

Hexu expressway is located in Jianghuai area. The periodic rainfall in summer induced long-term alternative saturation-loss-resaturation processes of shallow-buried rock layer below Hexu expressway. In order to study the deterioration characteristics of mudstone and sandstone in Jianghuai area under water-rock interaction, the experimental study on anti-shear, anti-compressionand Scanning electron microscopywere conducted for the samples taken from in situ in order to reveal the corresponding relationship and their validation laws between rock porosity structure and rock strength softness from macroscopic and microscopic levels during different wetting and drying cycles. The results showed that, water-rock interaction had a significant impact on the anti-shear intensity and anti-compression intensity void parameter of mudstone and sandstone. Rock cohesion and internal friction angle decreased fast with the increase of wetting and drying cycle times. When the wetting and drying cycles reached a certain value, the anti-shear intensity and anti-compression intensity of two types of rocks tended to be stable. The pore number, total area, the diameter and area of maximum micro pore and surface porosity increased with the increase of wetting and drying cycles. Based on the experimental results, the rock deterioration mechanism has been discussed, which provided a basis for the study of rock deterioration characteristics and the stability of Hexu expressway.