酸碱环境干湿循环作用下砂岩抗剪强度劣化规律研究

Deterioration rules of shear strength in sandstones under wetting and drying cycles in acid and alkali environment

为研究酸碱环境中砂岩在干湿循环作用下抗剪强度的劣化规律,在浸泡溶液p H值分别为7,9,4的环境中,对砂岩试件进行次数为1,3,6,10次的干湿循环试验。通过不同循环次数后的单轴和三轴试验,计算得到每个阶段循环后砂岩的黏聚力和内摩擦角及其与干湿循环次数N的变化关系式,从而获得砂岩在不同p H值干湿循环作用下抗剪强度随循环次数的变化公式。结果表明,砂岩的抗剪强度随着循环次数的增加而降低,在干湿循环作用前期,受影响较为显著,抗剪强度降幅很大,而后,强度降幅相对较小;酸性环境下,砂岩抗剪强度劣化最为严重,碱性次之,中性最轻;干湿循环后的干燥试件抗剪强度劣化幅度远不如湿状态下的劣化幅度。

In order to study the deterioration rules of shear strength in sandstones under wetting and drying cycles, sandstone specimens arc tested after 1, 3, 6, 10 wetting and drying cycles in the environment ofpH=7, 9, 4. Through UCS and TCS after diiTercnt cycles, the cohesion and internal friction angle of sandstone are calculated, and the relation formulae between them and number of cycles N arc determined, respectively, thus the shear strength is obtained under wetting and drying cycles in acid and alkali cnvironrncnt. The results show that the shear strength of sandstone decreases with the increase of cycles. In the early stage of cycles, the deterioration effect is comparatively significant, and the deterioration of shear strength is very large, then, the strength deterioration is relatively small. In the acidic environment, the deterioration of shear strength in sandstones is the most serious, slightly reduced in the alkaline environment, and the neutral condition is the lightest. The deterioration of shear strength in dried samples is much lower than that of wet samples.