鄂西北软弱变质岩水理力学性质及其滑坡致灾机理分析

Hydro Mechanical Properties of Soft Metamorphic Rock and Its Landslide Disaster-causing Mechanism in Northwest Hubei

十堰市地处中国鄂西北山区,区内地质环境背景复杂,主要地层岩性为变质岩。受地质环境的影响,区内变质岩岩性软弱,岩体结构较为破碎,风化强烈,与第四系松散岩地层一起构成了易滑地层,是滑坡灾害的高易发区。以十堰市软弱变质岩为研究对象,基于吸水性、耐崩解性、单轴压缩试验及直剪试验,分析变质岩水理力学性质及其滑坡致灾机理。结果表明,软弱变质岩吸水性较强且具有明显的各向异性特征和遇水软化特征,其单轴抗压强度随着法向应力方向与片理面之间夹角的增大呈现出两边高、中间低的“V”型变化规律,抗剪强度参数随着法向应力方向与片理面之间夹角的增大而增大,并且随着浸水时间的延长而逐渐减小;同时降雨诱发软弱变质岩滑坡的变形破坏,与岩土体强度、潜水、承压水作用息息相关,均遵循有效应力的原理。其研究成果可对十堰地区以及中国类似软弱变质岩地区的滑坡成灾机理认识及防灾减灾工作提供有益参考。

Shiyan City is located in the mountainous area of northwest Hubei Province.The geological environment background in the area is complex,and the main formation lithology is metamorphic rock.Affected by the geological environment,the metamorphic rock in the area has weak lithology,relatively broken rock mass structure and strong weathering.Together with the Quaternary loose rock stratum,it forms a slippery stratum,which is a high risk area for landslide disasters.In this paper,the soft metamorphic rock in Shiyan City is taken as the research object,and water absorption test,collapse resistance test,uniaxial compression test and direct shear test are carried out to obtain the hydraulic and mechanical properties of metamorphic rock and landslide disaster mechanism.The test results show that the weak metamorphic rock has strong water absorption and obvious anisotropic characteristics and water softening characteristics.Its uniaxial compressive strength shows a“V”shaped change law of high on both sides and low in the middle with the increase of the angle between the normal stress direction and the schistosity plane.The shear strength parameter increases with the increase of the angle between the normal stress direction and the schistosity plane,and gradually decreases with the increase of the immersion time.At the same time,the deformation and failure of rainfall induced soft metamorphic rock landslide are closely related to the strength of rock and soil mass,phreatic water and confined water,and all follow the principle of effective stress.The research results can provide useful reference for the understanding of landslide disaster mechanism and disaster prevention and reduction work in Shiyan area and similar weak metamorphic rock areas in China.