Study On Creep Mechanical Characteristic Of Mica-quartz Schist In Qinba Mountainous Terrain

Qinba Mountainous terrain traverses middle part region of China, and is a climatic boundary between the North and South. In the region, the mountain is high and steep, with the gully sprawling. Complex geological structure and various types of rocks has formed in a long geologic history. Moreover, intensive tectonic movement and unloading process results in a fragmentized rock mass, with a bad mechanical property. In recent years, many geological hazards incidents has occurred, including the shallow landslides, which was the most common type in this area., triggered by heavy rainfall along with engineering activities, the geological hazards bring about casualties and property loss and maintains a long-lasting threat. Qinba area went through complex tectonic movement in geologic history, which leads to complicated topography, geologic structure and fragmentized rock mass. Weathering process and unloading resulted in widely-distributed structure plane in metamorphic rock, especially for those sheet-like rocks, which controls the formation, development and stability of the shallow landslide.This kind of rock shallow slope generally goes through a long period of time before being unstability. Continuous heavy rainfall and human activities accelerate the creep deformation of the slope. In this case, the study on the creep characteristic of typical epimetamorphic rock is imperative to understand mechanism in shallow landslide, conduct numerical simulation on typical landslide and hazard prevention measures. In addition, creep experiment could supply reliable essential data for building creep constitutive model. At present, study on rheological mechanical theory is a hot issue on field of rock mechanics. In this paper, the author mainly focus on the creep experiment on mica-quartz schist, and combined with the creep theory analysis and numerical simulation. The research method considers the macroscopical mechanical behaviors and microstructure change in schist, including damage mechanical theory, to understand the mechanism in creep deformation and failure in mica-quartz schist.(1) Typical shallow landslide was set an example to illustrate the problem, and the mica-quartz schist, which controls the time-dependent deformation behavior of slope, was set to be the research object under various conditions including different confining pressure, water content and inclination of schistosity to study its creep behavior in different realistic condition, by analysizing axial, lateral and volumetric creep curves, isochronous stress-strain curves and creep rate curves.(2) Based on the SEM method, failure mode of structure in micro-scale was observed. All above is expected to understand the mechanism in deformation and failure of schist;(3) Moreover, based on relevant theoretical analysis, creep curves were identified by a appropriate non-liner model, then, model parameters was determined by non-liner east square method. Considering the tests were in three-dimensional stress state, conventional one-dimensional creep equation was theoretically expanded to three-dimensional creep equation by plastic mechanics theory, meanwhile, by introducing yield approach index(YAI), a threshold above which steady-state creep stage begins was expressed in a spatialized way.(4) Furthermore, by continuum damage theory and statistical strength theory, conventional Nishihara model was modified to fit for the creep curves, and this could reveal damage mechanism during the creep process.(5) In the end, creep model parameters were used in numerical simulation on shallow landslide.