Crack Propagation Law Of Weakly Cemented Rock Based On 3D Reconstruction

Weak cemented rock layers are widely present in the western mining areas of China.The rock layers are mainly weakly cemented sandstones with low maturity,which have the characteristics of low cementation degree,large porosity,and sensitivity to disturbances.Sex has a big impact.In this study,weakly cemented sandstone is selected for analysis and processing,aiming at its mineral information and microstructure of the weakly cemented sandstone are studied by combining the techniques of electron microscopy,X-ray diffraction,uniaxial compression experiment,acoustic emission experiment,CT scanning experiment and PFC numerical simulation.The change rule of acoustic emission during uniaxial compression treatment of weakly cemented sandstone is explored;explored the influence of initial damage on the crack propagation to the final failure form of the specimen;intuitively analyzed the contact force during the loading of weakly cemented sandstone through PFC numerical simulation And the change of force chain,displacement,and number of micro-cracks,and explore the influence of different porosity and different degrees of cementation on the crack propagation process of weakly cemented sandstone.This paper mainly made the following research results and progress:(1)The microstructure and mineral composition of weakly cemented rock were analyzed by means of electron microscopy and X-ray diffraction.The results show that the weakly cemented rock has a low degree of cementation and high porosity,and its mechanical parameters are lower than those of conventional sandstone.(2)Conduct joint uniaxial compression and acoustic emission experiments to study the mechanical properties and acoustic emission properties of weakly cemented sandstone.The average stress level of the AE mutation point is 0.86,and the average level of the damage value mutation point is 0.7.It can be known from the acoustic emission localization technology that the linear elastic stage and the plastic deformation stage are important stages for the generation of microcracks in weakly cemented rocks.(3)Three-dimensional reconstruction of the pores and fissures of weakly cemented sandstone before and after uniaxial compression using CT scanning technology,and the evolution process of fissures is deduced from the perspectives of total volume,surface area,porosity,and fractal dimension.The results show that the porosity and fractal dimension of the weakly cemented sandstone increase after loading;and from CT slices,it can be seen that the crack initiation position of the specimen generally occurs in the area of large initial damage and low density,and then the cracks respectively The expansion to the two wings eventually caused the entire specimen to break.(4)The PFC numerical specimen loading experiment was carried out.The results showed that the specimen changed rapidly in the post-peak period,and expanded and penetrated rapidly along the original damaged area of the specimen.The mechanical parameters of the weakly cemented specimen are positively correlated with the porosity and negatively correlated with the degree of cementation.The porosity and the degree of cementation have no significant effect on the type of fracture.This paper has 60 pictures,18 tables,and 84 references.