Discrete Element Simulation Of Limestone Micro-fracturing Processes With Flat Joint Contact Model

Karst landform is widely present in China,As reported,China suffers intensively from the collapses of karst,and loss of properties and human life every year,disturbing industries and civil life greatly.The development of karst requires soluble rocks and erosive groundwater,and seepage condition.Karst includes the chemical dissolution processes of soluble rocks,mechanical erosion under groundwater seepage,and transport and sedimentation of fine rocks.Therefore,karst is a complex chemical and physical processes.Limestone is one of the common soluble rocks,and its micro-fracturing investigation is a fundamental approach to understand the development of karst.Rocks are inhomogeneous and anisotropic discontinuities.Hence,the continua approach for numerical and theoretical analysis have critical limitation.The present studies explore the micro-fracturing of brittle limestone using a discrete element method software,named PFC3 D.The content of the present research includes,(1)Development of 3D particle flow simulation using flat joint contact model.Development of the relationship between macroscopic mechanical properties and microscopic parameters,and a 3D particle flow model reflecting precise elastic modules,uniaxial compression and tension strengths..(2)Development of Brazilian test model of limestone sample with single pre-existing flaw,which aimed to study the splitting failure mechanism.The angle of loading direction and flaw direction is controlled,and hence,the stress distribution around the fracture in mode I and the failure mechanism of mode I and mode II combination can be found.(3)Development of uniaxial compression modeling with pre-existing flaw limestone sample to investigate the micro-fracturing process.Investigate the influences of flaw direction in the initiation characteristics of tip micro-fracturing,expansion and propagation.The microfracturing initiation and propagation mechanism can be obtained with controlling the contact stiffness ratio and strength parameters.(4)Development of limestone particle flow model with calcite vein to study the microfracturing processes of rocks with other minerals.The influences of calcite vein in microfracturing processes are studied in controlling its relative strength,width and direction to the hosting rocks.