| The karst problems often encountered during tunnel construction are a worldwide problem.Nearly one-third of China’s land area is soluble,and such a large-scale soluble rock division poses severe challenges for the development of China’s transportation industry.The blasting excavation method is often adopted in the tunneling process of mountain tunnels.The disturbance to the surrounding rock and the objectivity of the caverns will aggravate the phenomenon of water inrush and mud in the tunnel.The safety hazards have seriously threatened the safety of the construction personnel in the tunnel.This paper combines the engineering examples of drilling,blasting,and excavation of the new Shanshutuo tunnel in Chongqing’s Pengshui county,and through the on-site monitoring and Midas/GTS NX software and blasting rock breaking theory,the propagation of stress waves and the explosion source The vibration response characteristics of the surrounding rock between caves were studied and analyzed.The changes of the stress field,displacement field and vibration velocity of the surrounding rock of the ellipsoidal cavity in the upper,lateral and lower parts of the tunnel and the long axis of the ellipsoidal spherulite are parallel to the tunnel axis(Y-axis),X-axis and Z-axis are discussed.To find the safe distance between the cave and the tunnel.The research content and results mainly include:(1)Based on the related theory of blasting rock breakage and stress wave,the attenuation function of the blast hole explosive and the radius of the crushed zone and the rupture zone were calculated.After the analysis,the safe vibration velocity of the karst cave front rock on the karst area is 10cm/s.(2)In the numerical simulation,the optimized load-free model was used to calculate the equivalent load peak at the cut hole.Compare the finite element software with the data obtained from on-site monitoring.The peak velocity of each direction is less than 1cm/s.It can be seen that the numerical simulation is more reliable.(3)The static and dynamic responses of ellipsoidal karst caves under different conditions are analyzed.It is considered that the vertical karst caves on the upper and lower sides of the tunnel have the least disturbance to the surrounding rocks under the same conditions,and the vertical karst caves at the same location have the greatest disturbance to the surrounding rocks,and the lower part of the tunnel is longitudinal.The caverns are the most sensitive to the effects of stress waves.Therefore,in the actual project,sufficient attention should be paid to the same lower caverns as the tunnels.(4)By numerical simulation,the safe distance of the karst cave and the explosive source is 15 m.The corresponding safe distance is 16.5m when the excavation is measured in 2.4m.The q-r curves of two methods are obtained and compared. |
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