| China’s mining engineering has gradually shifted to the deep.The extreme geological conditions and complex hydrological conditions are the biggest problems we are facing at present.The seepage pressure of fractured rock mass is one of the important factors affecting the stability and failure of rock mass.In the process of blasting construction of underground engineering,the dynamic load generated by blasting will pass through the seepage rock mass in the form of stress wave and act on the internal seepage water,which will change its internal water pressure and act on the rock mass to aggravate the fracture of rock mass.Therefore,the study of its mechanical characteristics provides an analysis basis for the stability of surrounding rock of roadway(tunnel)excavated by blasting,and has certain guiding significance for engineering construction..In order to analyze the change law of water pressure under the action of crack and the failure mode of rock itself under the action of crack,this paper carried out the following research work on the impact failure properties of rock under the action of crack water pressure through theoretical analysis,laboratory experiment and numerical simulation:1.Based on the summary and in-depth study of the relevant theoretical knowledge of hydrodynamic pressure,seepage pressure and surrounding rock failure at the present stage,the calculation formula of fracture water pressure in rock mass under impact load is obtained,and a water pressure adding device is made on the original SHPB experimental device.2.SHPB experimental device was used to conduct impact tests on rock specimens with hollow cylinders of different diameters 50 mm in length and 50 mm in diameter under the action of simulated crack water pressure,and to determine the factors influencing the change of internal water pressure,change rules and rock failure modes:(1)Impact tests were carried out on 5mm and 10 mm inner diameter cylinder specimens under different initial water pressure conditions.It was found that the initial water pressure in cracks directly affected the change of water pressure in cracks under blasting impact.The higher the initial water pressure was,the greater the maximum water pressure in cracks under impact load was,and the growth rate also increased.Meanwhile,the strength of specimen increases first and then decreases with the increase of initial water pressure.(2)Impact tests were carried out on cylinder specimens with different inner diameters under the initial water pressure of 1.0mpa,and it was found that the strength of specimens decreased with the increase of inner diameters.Under the combined action of impact load and initial water pressure,the size of seepage channel or water storage space affects the strength of rock mass,and the strength of rock mass decreases with the larger internal space.(3)When the high pressure small disturbance impact test was carried out on the cylinder specimen with 10 mm inner diameter,it was found that the specimen without water pressure under the impact of low load would not be destroyed,and the specimen under the impact of the same low load under the action of 85% cracking water pressure would be tensile failure.3.ABAQUS simulation software was used to simulate the experimental part,and the simulation results were compared with the experimental results.It was found that the simulation results were similar to the experimental results,which proved that the experimental conclusions were true and reliable.4.Based on the engineering example background,a numerical model was established on the Flac3 D software platform,and the prevention and control measures were put forward,such as setting a safe and reasonable thickness of water-resistant rock layer,adopting net shotcrete support and grouting reinforcement technology to improve the strength of surrounding rock. |
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