Study On Mechanical Response And Vibration Effect Of Layered Rock Mass Under High-pressure Gas Impact

China is a vast country with complex and changeable geological conditions.The vertical section of the rock stratum generally presents the significant layered structure characteristics of soft rock in the upper part and hard rock in the lower part.With the large-scale development of urban tunnels and underground projects in China,a large number of rock excavation projects constructed by blasting method involve layered rock mass.In the blasting projects carried out in the complex surrounding environment such as dense buildings,the traditional explosive blasting technology is limited or even can not be used.High-pressure gas blasting with physical rock-breaking method has been more and more widely used because of its high safety,environmental protection and stability.Under the background of adhering to the road of green,low-carbon and environmental protection during the 14 th Five-Year Plan period,in view of the current situation that the theoretical research of high-pressure gas blasting lags far behind the practice,it is necessary to carry out the research on the mechanical response and vibration caused by high-pressure gas impact in layered rock mass.This study has important theoretical guiding significance and practical value for revealing the mechanism of blasting breaking rock and blasting vibration effect under the impact of high-pressure gas,forecasting and controlling the harm of vibration effect caused by high-pressure gas impact,optimizing the design of high-pressure gas blasting schemes and further popularizing the application of micro vibration technology of high-pressure gas blasting.In this paper,the research methods of theoretical analysis,laboratory test and numerical simulation were comprehensively adopted to deeply and systematically study the stress wave propagation law and vibration effect of layered rock mass under high-pressure gas blasting.The main research work and conclusions are as follows:(1)The multi loads and multi-media flow in the hole under the action of high-pressure gas blasting were simplified as a multi-media compressible flow field with initial discontinuity.The whole process of the interaction between the multi-media flow field and the hole-wall interface was systematically analyzed.And the calculation models of hole-wall pressure caused by high-pressure gas impact with the discontinuous-interface conditions of pressure and particle velocity were deduced respectively,which provides theoretical models of impact load source for studying the rock-breaking mechanism of high-pressure gas blasting.(2)Based on the physical mechanical tests and high-pressure gas impact tests,the characteristics of hole-wall pressure and stress wave propagation in layered rock mass under high-pressure gas blasting were studied.The test results show that hole-wall pressure caused by high-pressure gas blasting has low peak value and longer duration;The crushing area near the hole wall is very small,and the impact energy is mainly used for crack expansion,so the energy utilization is high;Due to the effects of reflection tension and transmission rarefaction at the interface of soft rock and hard rock in layered rock mass,the peak value of the stress wave of layered rock mass under the impact of high-pressure gas is significantly lower than that of single rock mass,and the stress wave has obvious amplitude-attenuation characteristics when passing through the interface.In addition,the piecewise exponential model of hole-wall pressure,exponential decay model of the stress wave caused by single-hole impact and polynomial-exponential decay model of the stress wave caused by double-hole impact were put forward.The study reveals the dynamic characteristics of mechanical response in layered rock mass under high-pressure gas impact.(3)Based on the high-pressure gas impact tests,the characteristics of blasting vibration propagation in layered rock mass under high-pressure gas impact were studied.The test results show that the peak velocity and dominant frequency of blasting vibration gradually decrease with the increase of distance from explosion source,and there are vibration reduction and high-frequency filtering at the interface of soft rock and hard rock in layered rock mass.The models of the peak velocity and dominant frequency of blasting vibration with the influencing factors in layered rock mass under high-pressure gas impact were deduced by using the dimensional analysis method,and the specific model expressions corresponding to test conditions were regressed.The study reveals the propagation law of blasting vibration in layered rock mass under high-pressure gas impact.(4)Based on the numerical simulation tests of the excavation case for an underground project constructed by double-hole impact,the propagation characteristics of the stress wave and vibration effect in layered rock mass under high-pressure gas impact were studied.The results show that the stress state of rock mass is significantly affected by the effect of stress superposition in the direction of the connecting line between the two holes;The X direction of rock mass is mainly tensile stress,and the Y direction is mainly compressive stress in the perpendicular direction of the connecting line between the two holes.The influence of hole spacing on the propagation characteristics of the stress wave and vibration effect was analyzed,and the optimal hole spacing in the calculation example was determined as 100 cm considering the high-pressure gas impact effect and the allowable standard of vibration effect.This study provides theoretical guidance for the optimization of high-pressure gas impact schemes.(5)By the determination of the equivalent elastic-vibration load and elastic boundary under single-hole and multi-hole high-pressure gas impact,the prediction models of the ground vibration effect in layered rock mass under multi-hole high-pressure gas impact were proposed and their feasibility were verified.Moreover,the vibration effect data under high-pressure gas impact and explosive blasting were compared and analyzed.The results show that high-pressure gas impact can significantly reduce the vibration effect in layered rock mass than explosive blasting.This study reveals the mechanism of vibration effect in layered rock mass caused by high-pressure gas impact.There are 84 figures,22 tables and 272 references in this paper.