Experimental study on dynamic response characteristics of rocks under high water pressures and high stresses
Deep rock mass engineering is in high water pressure and high stress environment,its response characteristics are significantly influenced by the environmental conditions,which is an important basis for deep rock mass engineering blasting design and construction.In order to investigate the dynamic response characteristics of the rock under deep high water pressure environment,impact tests were carried out on red sandstone based on a self-developed high water pressure and high stress rock dynamic testing system,and 4 axial static stresses and 9 water pressure levels were set to simulate the occurrence environment of engineering rock mass.The effects of water pressure and axial static stress on the dynamic stress-strain curve and dynamic peak stress of rock were investigated by calculating dynamic stress and strain data of rock based on incident,reflected and transmitted waves.The pre-peak and post-peak energy conversion characteristics of stress-strain curves were considered comprehensively,and the water-inrush tendency index of rocks was defined by energy evolution parameters.The relationships between rock dynamic residual stress,residual strain,water inrush tendency index and wave impedance with water pressure were analyzed,the empirical models of dynamic peak stress strengthening coefficient,residual stress,residual strain,water inrush tendency index,wave impedance and water pressure,as well as dynamic peak stress and axial static stress were constructed.The influence mechanisms of high water pressure and high stress on the dynamic strength and deformation characteristics of rock were explored.The results show that the dynamic stress-strain curves of rock gradually change from type Ⅰ to type Ⅱ with the rise of water pressure.Under the same axial static stress,the dynamic peak stress strengthening coefficient,residual stress and wave impedance of the rock increase rapidly at first and then slowly with increasing water pressure,and the water inrush tendency index and residual strain decrease with the increase of water pressure.Under the same water pressure,the peak dynamic stress of the rock decreases as the axial static stress increases.High-pressure water has dual effects on rock dynamic strength,that is,the water wedge effect promotes crack propagation and reduces rock strength,while the Stefan effect and other viscous effects and external confining water hinder the destruction of pore structure and enhance the dynamic strength.The two effects play a game with each other and jointly affect the dynamic response characteristics of rock under deep high water pressure environment.The results of the study are favorable for blasting and excavation of engineering rock mass and stability analysis of surrounding rock under deep high water pressure environment.
rock mechanicshigh water pressurestress-strain curvestrength and deformationenergy evolutionwave impedance
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