Study On The Stability Of Surrounding Rock And Supporting Structure In Tunnel Drilling

During the drilling and blasting construction of the tunnel,the surrounding rocks in the blasting mid-range area will not be destroyed by one blasting,but due to the limitations of the construction conditions,the tunnel must undergo multiple blasting constructions.Therefore,the vibration damage caused by multiple blasting will gradually accumulate,and even the original cracks in the rock body will continue to expand and connect,which will promote the surrounding rock-support structure to gradually change from the state of slight disturbance to the state of strong disturbance,and eventually cause local Or the whole surrounding rock-supporting structure fails.In this paper,based on the unique geological and construction conditions of the CuBuLing Station of Qingdao Metro Line 4,the research method of theoretical analysis and finite element software numerical simulation is used to investigate the blasting mechanism of rock and the initial support structure under blasting vibration.The dynamic response,the stability of the surrounding rock-supporting structure under short blasting load were studied,and the damage of the surrounding rock-supporting structure under different excavation footage and surrounding rock strength was analyzed and compared,which was the fault of Qingdao Metro Line 4 The construction of Buling Station provides scientific and theoretical support.The main research results of this article are as follows:(1)By theoretically deducing the initial velocity formula of the detonation wave,the crack expansion displacement formula is obtained.Based on the attenuation formula of blasting vibration wave,under the condition of equal pressure and no support,the cumulative effect of multiple blasting loads is considered,a mechanical model is established,and the radial displacement formula of surrounding rock mass points is derived.(2)Through the analysis of the vibration velocity of different sections of grade III surrounding rock,it can be seen that the surrounding rocks of each section have cumulative damage effects during blasting construction,of which the accumulation at the bottom of the arch is still the largest.According to the actual support situation,For Grade III surrounding rock,in the actual blasting excavation process,it is optional to start the surrounding rock support work after the two excavation footage ends.(3)After analyzing the increase of each vibration velocity of the surrounding rock of grade IV,with the increase of the blasting distance,the damage of the stress wave to the surrounding rock gradually decreases,and the damage accumulation of the second blast also has a sudden effect,and the subsequent gradually Slowing down is the same as the trend of grade Ⅲsurrounding rock.According to the analysis of the vibration velocity of the surrounding rock of grade Ⅳ,for the surrounding rock of grade Ⅳ,in the actual blasting excavation process,the surrounding rock support work can be started after the end of the first excavation.(4)Through the analysis of the blasting displacement changes of the V-grade surrounding rock,it can be seen that for the V-grade surrounding rock,advance support work should be carried out during the actual blasting and excavation process,and the footage should be shortened appropriately to strengthen the initial support.(5)For different levels of surrounding rock,select concrete spray layers with different thicknesses for analysis.Concrete support can reduce the damage and displacement of surrounding rock,and as the thickness of the support increases,the cumulative value of displacement at each measurement point gradually decreases;when performing blasting construction of Ⅲ,Ⅳ,and V-level surrounding rock,you can choose Spray layer with thickness of 150mm,250mm and 350mm.