Experimental And Particle Flow Simulation Studies Of Red Sandstone Containing A Single Non-straight Fissure Under Uniaxial Compression

Rock is a widely existing complex medium in nature.After a long period of geological age,various defects(straight fissures,non-straight fissures,etc.)have occurred inside it.After these internal defects have initiated,propagated and coalesced,they often lead to instability and destruction of rock engineering.In this regard,many studies on cracked rock masses have been carried out by many scholars.But most of them focus on the research of straight fissures,the research on non-fissures is very scarce.Therefore,the study of the influence of non-straight fissure on the mechanical properties of rocks and the law of crack initiation and propagation is essential.In this paper,non-straight fissure and straight fissure are taken as the research object,and systematic uniaxial compression tests and simulation studies are carried out through laboratory tests and numerical simulations.The specific research content is as follows:(1)A series of red sandstone samples containing a single straight fissure or a single non-straight fissure was designed and processed,and a uniaxial compression test was performed on them.There are 7 inclination angles designed for both fractures.At the same time,the acoustic emission(AE)characteristics,full strain field characteristics and local strain field characteristics of the specimens during the test were recorded using AE equipment,digital photography technology and strain gauges.The effects of crack inclination on the strength and deformation characteristics,AE characteristics and crack initiation and propagation of two types of crack samples were analyzed in detail.(2)Based on the study of two types of crack specimens,taking into account the mechanical properties and the fracture mode,as the fracture inclination angle changes,the similarities and differences of the effects of non-straight fissure and straight fissure on the specimen under uniaxial compression are compared and analyzed.(3)With reference to the laboratory test scheme,the Particle Flow Code-PFC~3DD was used to build numerical models of the specimens containing a single straight fissure or containing a single non-straight fissure.Both types of fissures contained 7inclination angles.Referring to the results of the sensitivity analysis of the mesoparameters,a set of mesoparameters that can accurately reflect the results of the complete sample in the laboratory test are obtained by adjusting the parameters,and then uniaxial compression numerical simulation studies are performed on two types of fractured samples.It was found that the simulation results verified the uniaxial compression test results of the two types of crack samples,and the deformation and failure mechanisms of the two types of crack samples were respectively studied from the microcracks and velocity fields generated inside the samples.In addition,a further comparative study of two cracked samples was carried out.This thesis includes 95 figures,13 tables and 110 references.