Research On Vibration Response And Control Of Structures Under Blasting Excavation Of Metro Tunnel

In recent years,the drilling-blasting method has to be used when the hard rock stratum is encountered in the urban metro tunnel excavation in China.By using the drilling-blasting method,the blasting excavation of the tunnel will have an impact on the surrounding surface buildings and the adjacent tunnel structures and cause the vibration of the building structure.Therefore,it is necessary to study the vibration response law of the surrounding buildings and the control technology of the tunnel blasting construction.Based on the engineering background of Tong-Huo interval tunnel of Hangzhou Metro Line 5,this paper uses the method of theoretical analysis,numerical simulation and on-site monitoring to study the vibration response of metro tunnel blasting vibration to ground-sensitive buildings and the primary lining of the constructed tunnel.The main research work and conclusions are as follows:（1）Through the methods of literature research and theoretical analysis,this paper analyzes the mechanism of rock blasting fragmentation,expounds the influence division of rock failure,and analyzes the formation process and propagation characteristics of blasting seismic waves.At the same time,it defines the control standards of blasting vibration at home and abroad,and then puts forward the vibration reduction methods and control measures of building structures.（2）Based on actual engineering,the FLAC^3D numerical simulation method is used to study the vibration response law of surface structures caused by tunnel blasting excavations under different blast source distances,cyclic footage and maximum charge in a single section.The results show that the vertical velocity should be the main control index for the safety impact evaluation of the surface buildings,and the cyclic footage and the maximum charge of a single section should be the main control indexes for the blasting construction.（3）FLAC^3D is used to establish a three-dimensional numerical model and to study the vibration response of the primary lining of the constructed tunnel in different clear distance and different cyclic footage.The calculation shows that the vibration on the right side wall of the blasting side of the primary lining of the constructed tunnel is the most significant.The peak value of vibration velocity and displacement is the largest,which increases with the decrease of tunnel clear distance and the increase of cyclic footage.It should be the main monitoring part of tunnel blasting excavation.（4）Through the analysis and comparison of the blasting monitoring data and the numerical simulation results of the surface buildings,the feasibility of the numerical simulation method in the study of the blasting vibration effect of the tunnel is verified.Based on the safety vibration control standards of buildings at home and abroad,the technical indexes of tunnel blasting construction that meet the safety standards of vibration of surface buildings are put forward.The circulating footage of the constructed tunnel should be controlled within2.5m,and the maximum charge of a single section should not exceed 18kg.The circular footage of the following tunnel should be controlled within 1.0m,and the maximum charge of a single section should not exceed 10.8kg.