Study On Safety Impact Of Tunnel Blasting Construction On Adjacent Buildings

With the development of underground urban space and the increasing of urban rail construction,it is easy to have a great impact on adjacent buildings(structures)during blasting excavation of newly-built urban subway tunnels.Therefore,in order to ensure the safety of adjacent buildings(structures),it is necessary to formulate reasonable blasting construction plans and blasting parameters in combination by actual construction condition and surrounding environment.This paper takes the blasting construction section of Xin-xing Street to Bei-men Street Station of Xinjiang Metro Line 1 as the background.The combination of theoretical research,numerical simulation and on-site monitoring is used to study the vibration effects of tunnel blasting on adjacent buildings.The main research contents and conclusions are as follows:(1)Based on the blasting vibration wave theory,the causes and classification of vibration waves are studied,and the propagation and attenuation laws of stress waves are discussed.Meanwhile,the Group hole load simplified model and Blast hole wall initial pressure model are used to correct the formula of multi-hole blasting velocity under the influence of elevation.(2)Take the blasting construction section of Xin-xing Street to Bei-men Street Station of Xinjiang Metro Line 1 as an example,a detailed blasting construction plan is formulated for the construction section blasting by the surrounding environment,geological conditions and construction plan of the project.Meanwhile,the relevant technical parameters are determined and a blasting plan is formulated with the principles of “short footage,weak vibration,and low noise”.(3)According to the actual surrounding environment and construction plan,the Midas NX GTS finite element software is used to establish the building frame models and the geotechnical models,and the blasting excavation on the left line tunnel is simulated.The results show that the vibration velocity,displacement and stress of the building meet the requirements of the specification.(4)During the process of tunnel blasting excavation,vibration monitoring is carried out on the tunnel blasting section bythe blasting construction plan.The monitoring results are as follows: In the left-line blasting section ZDK5+335,the maximum vibration velocity in the X direction is 0.348 cm/s,in the Y direction is 0.455 cm/s,the in the Z direction is 0.633 cm/s,and the maximum value of the three vector combination speed is 0.853 cm/s,which the maximum combination speed is not more than 2.0cm/s as required by the specification.The ranges of frequency are mainly between 45 Hz and 60 Hz,which is quite different from the natural frequency of the building itself.Therefore,from the monitoring results,both the vibration speed and the frequency meet the requirements of the national specification,which has no impact on the safety of surrounding buildings.(5)The calculated value of the modified formula is compared with the monitoring value of the left-line blasting section ZDK5+380 and the calculated value of the traditional formula.The results show that the relative errors between the calculated values of the modified formula and the monitoring value are relatively close.The maximum relative errors of X,Y,Z and combined velocity are 14.965%,14.801%,13.524%,and 13.324% respectively.In the comparative analysis of calculated values of the traditional formula and monitored values,the relative error between them are quite different.The maximum relative errors of X,Y,Z and the combined velocity are 49.282%,33.692%,30.710%,and 33.1215% respectively.In the comparative analysis of the calculated values of modified formula and the traditional formula,the relative error between them are also quite different.The maximum relative errors of X,Y,Z and the combined velocity are 84.112%,29.670%,29.086%,and 33.095% respectively.At the same time,the distribution law of the revised formula is consistent with the actual monitoring value,which proves that the correction formula can reflect the influence of the elevation on the adjacent vibration velocity to a certain extent.In the distribution law of the traditional formula and the monitoring value,the two show opposite trends,indicating that the traditional formula does not have a clear reflection of the elevation effect.So the accuracy of the correction formula and the guiding role of similar engineering are verified.