Sliding Mechanical Properties Of Fault Gouge Based On The Analysis Of Microstructure Characteristics

Fault activity is one of the main factors that induce geological disasters and control the spatial distribution of geological disasters.The microstructures of sliding surface of fault gouge record the activity information of the fault.The Shendaogou Fault is located in the management area of the ―Gully Land Consolidation‖ Project in Yan ’an.The rise of groundwater level caused by ―Gully Land Consolidation‖ may weaken the strength and the resistence to sliding of fault gouge.Taking fault gouge of the Shendaogou Fault as the research object,the particle size and mineral composition of fault gouge as the research foundation,the sliding behaviors of fault gouge with different normal stress and water content were simulated by the ring shear test.The microstructures of shear surfaces were quantitatively analyzed by scanning electron microscopy(SEM).Through the reflection of microstructure on the sliding characteristics of fault gouge,the sliding mechanical characteristics of fault gouge were explored.Based on the field monitoring of groundwater level and landslide deformation,the potential disaster-causing effect of ―Gully Land Consolidation‖ was evaluated,and obtained the following main research results.(1)The sliding mechanical properties of fault gouge are affected by fabric characteristic parameters(mineral and granularity)and mechanical environmental factors(water and stress).The content of coarse particles and the content of non-clay minerals can be used as the quantitative indexes to evaluate the sliding mechanical properties.The strain softening of fault gouge is affected by the content of water and coarse particles,which first strengthened and then weakened with the increase of water content.(2)The shear surface roughness can be used to characterize the macroscopic strength from the perspective of microstructure.There is a linear relationship between shear surface roughness and residual strength.Coarse particle fault gouge is more likely to show a larger residual strength at low water content,and the residual strength with a rough shear surface develops more strongly under the same normal stress.The analysis method based on the shear surface roughness can provide a reference for evaluating the sliding resistance of fault gouge.(3)The sliding of hard coarse particles shapes the sliding scratches,and the ratio of sliding scratches(R)can be used as a quantitative index of the microstructure to characterize the sliding mechanical properties of the gouge.The significant linear relationship between the residual strength parameters and R indicates that the sliding scratch is the external performance of the residual strength stage.R is negatively correlated with water content and normal stress,and positively correlated with quartz content and sand grain content.(4)A multivariate model of the microstructure under the influence of mechanical environment factors and fabric characteristics is established.The multivariate model shows that the anti-sliding ability of fault gouge decreases with the continuous increase of water content.The field monitoring shows that there is a strong consistency between the uplift of groundwater level caused by the ―Gully Land Consolidation‖ and the deformation of landslide in the fault crossing area.Therefore,the change of engineering geological effect of the Shendaogou Fault and the potential geological disasters caused by ―Gully Land Consolidation‖should be paid constant attention.