Research Of Numerical Methods And Deformation Characteristics For Rockfill

Rockfill is a discrete material which is always utilized in the ports and water conservancy projects.In the port projects,with the increase of scale of gravity quay,thickness of the rubble bed is increasing,leading to the increase of the settlement deformation and the stress inside it,which means calculation of the settlement deformation of the rubble bed is still a problem not solved well.When rockfill is imposed to gravity and load,the stones inside adjust their positions with translation and rotation,sometimes the stones will break.Compression test and numerical experiment are two common ways to study the deformation characteristics of rockfill.Discontinuous deformation analysis(DDA)and discrete element method(DEM)could simulate the translation and rotation of blocks in discontinuous block systems well,while these methods could not simulate the generation and propagation of crack inside the block and abrasion of angular area of the block.In this paper,stress accuracy inside single block of DDA and bonded-particle model(BPM),relationship of load and displacement in angular-plane compression test and the corresponding numerical experiment,meticulous simulation of crack inside the block,compression test of rockfill and the corresponding numerical experiment are carried out and studied.The main contents are as follows.(1)Contact stress on the boundary of a DDA block is deduced.Based on the contact stress on the surface,a stress recovery method is proposed for DDA.Numerical examples are designed,compared with the result of finite element method(FEM),accuracy of the method is illustrated.(2)Combine with the average stress value of a DEM particle,a stress recovery method is proposed for BPM.Numerical examples are designed and influence factors of accuracy of the method are analyzed.(3)Angular-plane compression test are carried out with concrete blocks,load-displacement curves during loading are obtained.Through the compression test,parameters for the numerical experiment are obtained.The angular-plane contact numerical experiment is designed and the related subroutine is complied.Simulation of this phenomenon by BPM is verified.(4)Base on the Griffith strength theory,combine with the continuous stress field obtained by the stress recovery method of BPM,a numerical method that can simulate crack inside the block meticulously is proposed.When number of particles inside a block is limited,the method could simulate generation and propagation of crack meticulously.(5)Single axis compression test is carried out for rockfill utilized in the rubble bed of gravity quay,in which the stones weigh 10-100 kg,load and unload curves are obtained.Numerical BPM compression experiments are designed.The numerical compression experiments could simulate crack and angular abrasion in rockfill.Simulation of compression test of rockfill by BPM is verified.(6)Different numerical models are generated with multiple grades,upper and lower limits of weight range of stones,shapes of stones.Compressions of these models are carried out to study the deformation characteristics of rockfill.Some disciplines are found,such as with the same lower limit of weight range,enhancing the upper limit will lead to increase of compression modulus,with the same upper limit of weight range,enhancing the lower limit will lead to decrease of compression modulus,etc.