干燥失水对泥质粉砂岩遇水后物理力学性质的影响

Effect of Desiccation and Dehydration on Physical and Mechanical Properties of Argillaceous Siltstone Contacting Water

近年来,四川东部红层地区多次出现"久旱逢雨"的特殊天气,干燥的岩体土质迅速转为饱水状态,物理力学性质发生变化造成地质灾害的发生。为应对这种极端天气,需探究干燥失水对岩体遇水后物理力学性质的影响,该文以具有代表性的四川中江红层泥质粉砂岩为研究对象,采用烘箱使岩样达到干燥失水状态做浸水试验,探究干燥失水对川东红层泥质粉砂岩遇水后的单轴抗压强度、弹性纵波波速及矿物成分的影响,揭示其宏观力学性质、细观结构及微观矿物成分的变化规律。试验结果表明:泥质粉砂岩虽然具有较高的含砂量,但在干燥失水条件下遇水后,其物理力学特性发生显著变化,纵波波速及强度先大幅下降后趋于稳定,与天然岩体直接饱水浸泡相比,干燥失水条件下的岩体随浸水时间,强度下降的速度和幅度都有所增加。矿物成分测试结果表明:伊利石、长石分解为蒙脱石等矿物,这对工程施工地质体防治提供了理论依据。

In recent years,the special weather of"raining after a long drought"has occurred in the red bed area of eastern Sichuan for quite a few times,making the dry rock mass soil quickly enter the saturated state,and the change of physical and mechanical properties causes geological disasters.In order to cope with such extreme weather,it is necessary to explore the influence of desiccation and dehydration on the physical and mechanical properties of rock mass contacting water.In this paper,the typical argillaceous siltstone in the red bed area of Zhongjiang,Sichuan Province was taken as the research object,and an oven was used to desiccate and dehydrate the rock sample for water immersion test,so as to study the effects of desiccation and dehydration on the uniaxial compressive strength,the elastic longitudinal wave velocity,and the mineral composition of argillaceous siltstone in the red bed area of eastern Sichuan,and reveal the change laws of the macroscopic mechanical properties,the microscopic structure and the microscopic mineral composition.The test results showed that the physical and mechanical properties of argillaceous siltstone change significantly when contacting water under the condition of desiccation and dehydration,although the siltstone has a higher sand content;the longitudinal wave velocity and strength first decreased sharply and then tended to be stable;and compared with natural rock masses soaked in water directly,the decreasing speed and strength of rock mass in desiccation and dehydration rose with the increase of the immersion time.The mineral composition test results showed that illite and feldspar were decomposed into montmorillonite and other minerals,which provides a theoretical basis for the prevention and control of plastids in construction sites.