Study On Failure Mechanism Of Red Sandstone Based On Discrete Element Method

In recent years,with the continuous improvement of China's urbanization level and the expansion of development area,all kinds of geological disasters are inevitable.It is very important to study the failure mechanism of rock for engineering development and geological disaster control.According to a large number of literature research,the discrete element software PFC has unique advantages in the study of rock failure mechanism,and is widely used in geotechnical engineering.Its main problem is the calibration of meso parameters.At present,most scholars use the "trial and error method" which has a large workload and blindness,and the research of rock failure mechanism also needs to be developed.The main research methods of this paper are laboratory test and computer numerical simulation.The research contents are mainly divided into five parts: sensitivity analysis of PFC micro parameters,indoor test of red sandstone,intelligent identification of micro parameters,discrete element study of failure mechanism of red sandstone with holes,and Simulation of rock blasting conditions.The results are as follows:(1)In PFC,the more advantageous constitutive model of straight joint is selected to simulate red sandstone,and the sensitivity analysis of the micro parameters in the constitutive model is carried out to select the micro parameters that have significant influence on the stress-strain curve,and it is proved that the straight joint model can meet the UCS / TS value.(2)The uniaxial loading test of red sandstone is carried out,and the physical parameters of red sandstone and the strain nephogram made by software vic-2d are obtained by digital speckle technology,which are used for the next numerical simulation and analysis.The selected BP neural network algorithm can accurately establish the macro micro parameter mapping relationship,with small error.The simulated stress-strain curve is highly consistent with the physical test stress-strain curve.(3)The failure mechanism of red sandstone with different hole shapes is studied.Under the condition of unidirectional stress,the existence of holes causes the peak stress of the test piece to decrease obviously,and the shape of holes also directly affects the peak stress intensity of the test piece.The horseshoe hole test piece has the largest strength,followed by the round hole test piece,and finally the rectangular hole test piece.Under the condition of bidirectional stress,the influence of confining pressure is further studied The failure mechanism of different void specimens is different from that of unidirectional stress,which is that confining pressure mainly limits crack growth.(4)Combined with the actual engineering study of smooth blasting,the paper introduces the artificial boundary to establish the discrete element model,and analyzes the impact on blasting from three aspects: the depth of the explosive,the amount of charge and the time of explosion.According to the general situation of the project,the smooth controlled blasting is simulated.The simulation results show that the model can effectively ensure that the rock in the excavation area is blasted and the rock around the blasting hole is completely preserved.