Numerical Studies On The Failure Mechanism Of Rock Bridge Under Direct Shear

Landslide is one of the most important geological disasters in the world.It is of urgent social need and important scientific value to carry out research on its instability mechanism and prediction,scientifically evaluate its possibility and accurately predict its occurrence time.Compared with the instability mechanism of other types of landslide,the instability mechanism of locked segment landslide is more clear and easy to understand.In other words,the prediction of instability of locked slopes may be easier to solve.A large number of studies have pointed out that the lock section is the key geological structure to control the evolution process of the locked segment landslide,and it is of great value for solving the prediction of the instability of the locked segment landslide to gain insight into the mechanical behavior characteristics of the brittle failure of the lock section and carry out quantitative analysis on it.In this paper,the coplanar rock bridge model is generalized into the coplanar rock bridge model based on the straight shear type locked landslide.The purpose is to reveal the fracture mechanism of the coplanar rock bridge under the action of direct shear,so as to better understand the instability process of the straight shear type locked landslide and help to solve the prediction problem.In order to facilitate the study,the model with two coplanar rock bridges is taken as the research object in this paper.Need to point out that although has quite a few scholars of rock bridge of the mechanical behavior of rock mass under the effect of direct shear are studied,promoted us to contain the understanding of the rock mass deformation and failure process of rock bridge,but for the weak intercalations contains multiple failure process of rock bridge interaction mechanism is lack of quantitative research,and multiple rupture of rock bridge well versed in order by what factors control remains to be further study of textual research.Based on previous researches,this paper focuses on the following aspects:(1)The classification of cracks in discontinuous jointed rock mass and several criteria commonly used in the process of propagation and connection are summarized: more-coulomb criterion,maximum tensile stress criterion,Jennings strength criterion and Lajtai bridge failure theory criterion.(2)The direct shear numerical simulation was carried out on the rock mass of the rock-bearing bridge by ABAQUS,and the influence of crack connection rate and normal stress on crack propagation in the failure process of the model was investigated.Under the same connectivity rate and different normal stress states,with the increase of normal stress,it is more difficult for the wing crack to expand,indicating that the larger the normal stress is,the stronger the inhibition on the development of tensile crack is.Under the same normal stress state and different connection rates,with the increase of connection rates,the end wing cracks of the primary cracks at both ends developed better.(3)The direct shear numerical simulation was carried out on the model with two locking segments by ABAQUS,and the effects of normal stress,size and strength of the locking segment on the fracture sequence of the two locking segments were investigated.In direct shear test,the fracture sequence of the lock section is affected by the size and strength of the lock segment,and usually follows the rule of small size and small strength of the lock segment.