Seisimic Damage Characteristics Of Rock Based On Energy Dissipation And Disaster-pregnant Mechanism Of Strong Earthquake

Co-seismic disaster occurred instantaneously,but the post debris flow and post landslide have a long-term effect,which seriously increased the disaster of the earthquake affected area.Meanwhile,due to the seismic rock damage with high concealment,gravity and rainfall can easily trigger landslides.Since the Wenchuan earthquake in 2008,the damage rock slide events has reached dozens,which creates an immeasurable loss.Rock mass damage is one of the important subjects of seismic geohazard research.In this paper,the damage mechanism of rock mass caused by earthquake is the main research content,demonstrating damage characteristics of rock mass from macroscopic-microscopic-microscopic scale.Based on rock dynamic load test,the nonlinear deformation characteristics of rock and the relationship between dynamic damage and energy dissipation are studied systematically,and established an interface slip criterion and a fracture criterion of rock mass.And then,taking the typical damaged rock landslide as the research object,the investigation of the characteristics of the rock mass in the slope rock is carried out,and the cumulative effect of the repeated earthquakes on the slope damage.Taking one of the the typical earthquake landslide in Wenchuan earthquake area as the research object,the quasi-dynamic analysis of the typical wedge slope is carried out,and the stability model of seismic wedge slope is established.The main research results and conclusions are as follows:(1)The cracking and damage characteristics of rock under dynamic load are revealed from macroscopic,microscopic and microscopic scales.The rock damage on macroscopic scale is mainly manifested by seismic crack;on the mesoscale is mainly manifested as the fissure or veins expansion along the original rock cracks;and on the microscopic scale is characterized by intergranular fracture or transgranular fracture phenomenon.The paper points out that the damage and cracking of rock are from microcosmic to macroscopic gradual development.The microscopic damage of the rock mass accumulates macroscopically and eventually leads to the destruction of the rock mass.(2)The nonlinear deformation characteristics of rock under dynamic load are studied from the mesoscopic scale by using the triaxial test method.The experimental results show that the dynamic elastic modulus and the residual strain of the rock are logarithmically related to the upper limit stress of the cyclic load,and the influence of the circulation cycle is small.The test also revealed the ultimate deformation law of the rock under the low cycle fatigue load,and determined the upper limit stress of rock's low cycle fatigue.(3)Combined with cyclic loading test,the energy evolution law of rock dynamic deformation and failure process is studied,and the relationship between elastic energy and dissipation energy is revealed.Based on the principle of energy dissipation and considering the initial damage of rock,the damage model of rock under unidirectional compression and low cycle fatigue is established.(4)Based on the theory of fluctuation,the propagation characteristics of different waves in the layered rock mass and the cracked rock and the dynamic response of rock mass interface are studied.The criterion of interface slip criterion based on energy dissipation and the dynamic stress intensity factor criterion of rock mass fracture are established.The propagation law of stress wave in fractured rock mass is further visualized by numerical simulation method,and the energy absorption effect of soft rock mass is revealed.(5)Based on the principle of quasi-dynamic analysis,a calculation model of rock cracking depth controlled by a rock level or a crack is established,and the judgment criterion of shear-landslide is established.The geometrical characteristics of the complex structure rock mass are analyzed and a typical wedge-shaped landslide Quasidynamic evaluation model for instability of shattering is established.(6)Seismic cracking mechanism of fractured rock mass.Based on the principle of quasi-dynamic analysis,the calculation model of seisimic cracking depth of fractured rock mass is established,and the seismic shear criterion of rock landslide is established.On this basis,the fracturing of complex rock and the stability evaluation model of typical earthquake wedge landslide is established.And the model is verified by actual cases.