Study On Fracture Damage Mechanism And Stability Of Fractured Rock Mass

The stability of fractured rock slope is a research hot in slope engineering.Its sudden,destructive chacteristics directly threat life and property.Under the influence of the geological structure,excavation,long-term weathering and the heavy rainfall,a variety of macro-and micro-cracks in the natural rock mass occur.Because of the stress concentration at the crack tip,the crack extension along the crack tip is an important factor causing the rock slope failure.Based on fracture mechanics,this paper examines the complex rock mass related to engineering,and considers the influence of fracture on macroscopic mechanical behavior so as to provide an effective method for assessing stability of cracked rock slopes.Based on the theoretical analysis,experimental testing and numerical computation,the study on the mechanism of fracture propagation and constitutive model of macro-and micro-defects in fractured rock mass and analysis of rock slope stability are performed,and the results are obtained as follows.(1)Based on the linear elastic theory and fracture theory,the theoretical and numerical methods of the stress intensity factor at the crack tip are obtained,and its applicability are discussed considering the geometric features of the cracks.The theoretical analysis can be used to calculate the stress intensity factor at the crack tip.However the relationship between size and crack length must be taken into account.The numerical method can not only calculate complex model,but also shows high precision.There is a assumption that rock mass is a homogeneously elastic.Therefore,there are some limitations in the engineering application.(2)The compression shear fracture test of rock-like specimen was carried out.The mode II fracture criterion of brittle material is studied.At the same time,the method identifying the fracture type and the conditions of the crack initiation criterion are proposed.The experimental results show that the proposed method is effective and reliable.(3)Creep fracture tests of rock-like specimen was performed.The damage mechanics and fracture mechanics are used in fractured rock.The coupling between macroscopic-and micro-defects during fracture damage propagation is considered.The rheological constitutive model and the damage evolution are obtained,which is available for macro-and micro-fracture material.The creep constitutive model is used to predict the deformation of the rock-like specimen,and the test results are in good agreement with the theoretical solution.The creep constitutive model and the damage variables are accurate.(4)Combined with the pratical fractured rock slope,the stability evaluation of the fractured rock slope and the prediction of the fracture failure mode are performed using fracture mechanics.The finite element software ABAQUS is used to simulate the process of fracture instability of a fractured rock slope.The results show that the fracture mechanics can examine the stability of rock mass and predict the crack initiation angle,which is of great significance to predict the unstable volume of rock mass,and determine the anchorage design and anchorage depth.The numerical results of rock mass instability are close to the results of fracture mechanics.Furthermore,the accuracy of the method is proved.The stability of fractured rock slope is affected by weathering effect and the depth of weak interlayer.The combined action will lead to increase of the deformation of the rock slope,and the potential destabilizing factors are formed.