Experimental Study on Pore Structure and Triaxial Mechanical Properties of Shotcrete Damaged by Blasting Load
In order to explore the influence of blasting load on the pore structure and mechanical properties of shotcrete nuclear magnetic resonance(NMR)detection technology and triaxial loading device were used to conduct experimental re-search on the micro pore structure and macro mechanical properties of concrete damaged by blasting load.The effects of differ-ent confining pressures and blasting distances on the T2 spectrum distribution,pore structure change,porosity,compressive strength,crack initiation stress and dilatancy stress of the specimens were analyzed.The results show that:① the T2 spectrum of shotcrete specimens shows a 3-peak shape,and the intensity of peak 1 is much higher than that of peak 2 and peak 3.After blasting loading,the peak value of T2 spectrum of specimens increases and shifts to the right,the total area of T2 spectrum dis-tribution increases,and the number and diameter of pores inside the specimens increase.② The porosity of the undamaged specimen is 1.63%,and the porosity of the specimens at 80 mm,140 mm,200 mm and 260 mm from the blasting source is 3.78%,3.01%,2.55%and 1.89%,respectively.The blasting load increases the porosity of the specimen,and the increase of the distance from the blasting source decreases the increase of the internal porosity of the specimen.The proportion of micro-pores and mesopores in the specimens is more than 87.01%.After the blasting load,the proportion of micropores in the dam-aged specimens decreases,and the proportion of mesopores,macropores and cracks increases.③ The increase of confining pressure makes the peak stress,crack initiation stress and dilatancy stress of the specimen increase,and the confining pressure enhances the mechanical properties of the specimen.④ After the blasting load,the peak stress,crack initiation stress and dilat-ancy stress of the specimen are reduced to varying degrees,and the smaller the distance from the explosion source,the more significant the stress reduction of the specimen and the greater the porosity increase.In the process of bolting and shotcrete support and concrete lining,the influence of blasting stress wave on the mechanical properties of shotcrete should be fully con-sidered,and preventive measures should be taken in advance.
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