Development Of A Cohesive Zone Model For Modeling Rock Fragmentation And Its Application In Rock Avalanche Analysis

The rock avalanche is a kinetic and dynamic process of the landslide from the development of deformation,instability to high speed,collision and accumulation.The depth of its research has important scientific theoretical value.The internal rock mass in the process of moving will be further broken disintegration,the study of progressive rock breaking process is undoubtedly a prerequisite for the interpretation of high-speed and run-out features,is a fundamental problem.Based on the fracture characteristics of quasi-brittle materials,this paper develops the theory of progressive fracture and explores the interaction mechanism of progressive disintegration behavior and transport-dynamic characteristics of sturzstrom.This article mainly to do the following aspects of research work.(1)Based on the basic principle of distinct element method,the Mohr-Coulomb yield surface with pull-off property is proposed as the initiation criterion,and the BK composite energy criterion is introduced to establish the force and displacement equation of the tension-shear zone,the tension zone and the compress-shear zone,then the nonlinear contact constitutive model of the C++ program.(2)In order to overcome the path dependence,a large-scale 2D and 3D Voronoi tessellation generation method and regularization method are introduced,including generating 3DE-Voronoi tessellation model based on element attributes(such as size distribution)and multi-dimensional model.The results show that the 3DEC-Voronoi tessellation model has the applicability and effectiveness by using the three-point bending beam test and characterizing the progressive development of the crack path through the state of the sub-contact point.(3)Based on the Galvez asymmetric beam test,the parameters of the stiffness k,the friction angle fric and the cohesion coh are analyzed respectively,and the discontinuous medium model is considered to be a natural unresolved deviation.The fracture process of Galvez beam under different energy criterion,softening curve and shear factor is analyzed.(4)The numerical simulation of single particle compression was carried out,and the influence of parameters such as stiffness,fracture energy,shear factor and particle gradation on its mechanical behavior were analyzed.The disintegration process of single particle under static loading is described in detail,which is divided into four stages: conical failure,columnar failure zone expansion,spindle transformation and longitudinal shear fracture formation.(5)Then develop rock mass progressive disintegration simulation method,based on Voronoi multi-dimensional tessellation model generation method,achiving communication with 3DEC software command flow and the formation of quasi-threedimensional multi-dimensional sturzstrom geometric model.Based on the kinematics and dynamics analysis of the whole process of landslide from the start-up to transport,the influence of the friction angle of the sliding bed and the nature of the rock mass on the dynamic disintegration is explored.The interaction of the disintegration effect on the velocity of the sturzstrom is improving.