干湿循环作用下云母石英片岩抗压性能劣化规律及机理

Degradation law and mechanism of the compressive strength of mica quartz schist under dry-wet cycles

干湿循环作用可促使片岩边坡岩体力学性能劣化、稳定性降低,进而诱发滑坡、崩塌等地质灾害。以湖北十堰地区广泛分布的云母石英片岩为研究对象,分别对不同干湿循环作用下云母石英片岩试样开展了单轴压缩试验和电镜扫描测试,揭示了其抗压性能劣化规律及机理。结果表明:在干湿循环作用下,云母石英片岩抗压强度和弹性模量劣化效应明显,前期劣化速率较快、劣化幅度较大,后期劣化速率减缓、幅度降低;宏观破坏模式受到片理面的控制作用而逐步增强,由“X”型、“Y”型破坏逐渐演变为沿片理面的剪切破坏;微观结构表现为片状矿物颗粒不断剥落、颗粒化,微裂隙、孔隙逐渐发育、扩展贯通;干湿循环作用使得云母石英片岩产生次生矿物、离子和岩屑并不断离开岩石,促使片理、微裂隙等结构面扩展开裂、岩石结构松散,进而使得云母石英片岩整体力学性能劣化。研究成果可为片岩边坡稳定性分析及治理工程设计提供理论依据。

[Objective]The dry-wet cycles can promote the deterioration of the mechanical properties and stability of schist slope rock masses and induce geological disasters such as landslides and collapses.[Methods]Taking mica quartz schist,which is widely distributed in Shiyan,Hubei Province,as the research object,uniaxial compression tests and electron microscope scanning were carried out on mica quartz schist samples under different dry-wet cycles to reveal the degradation law and mechanism of its compressive property.[Results]The results show that under the action of dry-wet cycles,the degradation effect of the compressive strength and elastic modulus of mica quartz schist were obvious.The degradation rate was fast and the degradation range was large in the early stage,but the degradation rate was slow and the degradation range was low in the later stage.The macroscopic failure modes were gradually controlled by the schistosity planes,which gradually evolved from styles of"X"and"Y"failure to along the schistosity planes failure.The microstructure was characterized by continuous spalling and granulation of flake mineral particles,and the microcracks as well as pores were gradually developed,expanded and connected.The mica quartz schist produces secondary minerals,ions and rock cuttings and leaves the rock continuously under dry-wet cycles,which promotes the preferential expansion and cracking of schistosity,microcracks and other structural planes.which then degrades the overall mechanical properties of the mica quartz schist.[Conclusion]The research results can provide a theoretical basis for the stability analysis and treatment design of schist slopes.