Experimental study on strength and deformation characteristics of sandstone damaged by blasting under triaxial compressive loading
In order to explore the strength,deformation and damage characteristics of the roof sandstone damaged by blasting load under different confining pressure conditions,triaxial compression tests were carried out on three sandstone specimens with different damage degrees by triaxial loading system,and the microstructure of the specimens with different damage degrees was obtained by electronic digital microscope.The effects of blasting load damage and confining pressure on the strength,cohesion,volume strain,fracture morphology and microstructure of sandstone specimens are analyzed.The results showed as follows:(1)Compared with the undamaged specimens,the damage degree of vibration damage and blast damage specimens at 0 MPa perimeter pressure is 5.53％and 18.87％,respectively.The peak stress,cohesion and internal friction angle of undamaged specimens are higher than those of vibration-damaged specimens and blasting damaged specimens.The blasting load causes obvious deterioration of sandstone strength,and the damage degree of blasting damaged specimens is higher than that of vibrating damaged specimens.(2)The peak stress of specimens with different damage degrees increased linearly with the increase of confining pressure,and the existence of confining pressure limited the deformation of specimens,and the deformation degree of specimens subjected to confining pressure was smaller when they reached the same stress.(3)The ultimate volume strain of the undamaged specimen at 0 MPa confining pressure is 1.65 and 1.46 times that of the vibration-damaged specimen and the blasting damaged specimen,and 1.85 and 1.49 times that of the vibration-damaged specimen and the blasting damaged specimen at 10 MPa confining pressure.The whole homogeneity and bearing capacity of undamaged specimens are higher,and the deformation degree of undamaged specimens under load is greater.(4)With the increase of confining pressure,the fracture degree of the specimen decreases first and then increases,and the specimen shows multiple failure modes of shear failure,tensile failure and compression failure co-existing.A large number of new joints,cracks and faults are generated in sandstone damaged by blasting load at the mesostructural level,and the damage degree in the blasting damage area is higher than that in the vibration damage area.
rock mechanicstriaxial compressionblast damagetop sandstonepeak strengthvolumetric strainfracture crushingfine structure
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