Study On The Influence Of Blasting Excavation Of A Tunnei On Surface Structure And Safety Assessment In Guangxi

The blasting operation belongs to the construction industry,the release of explosive energy in the process of blasting will bring many harmful factors,such as shock wave,flying rocks and surface ground motions,which cause great security risks and the impact to the nearby people and buildings.In view of the influence of tunnel blasting seismic wave on the surface of buildings is a serious problem,how to reduce the blasting impact of residential areas or the tunnel on personnel and buildings and the surrounding environment is extremely important,therefore,it is of great theoretical and practical significance to study the safety influence of tunnel blasting seismic wave on the surface of building engineering.Based on the research status and development of tunnel blasting technology,this paper points out the importance of safety control in tunnel blasting technology.Through mathematical model analysis,it studies the rock blasting mechanism,then analyzes the mechanism and safety control measures of blasting seismic waves and flying stone hazards.On this basis,it combines with the Guangxi tunnel blasting project,proposes blasting construction scheme,plan,process flow,blasting parameters and the corresponding safety measures.Based on the project example,it gets correlation of parameters and influence weight by using grey relational analysis model and AHP method and uses the fuzzy assessment to assess the impact of the tunnel blasting construction project to the buildings on the ground surface.The following conclusions are obtained:Including three aspects of blasting seismic wave,seismic flying rocks,noise in tunnel blasting hamful to surface buildings,it results in different security countermeasures combineing with the practice and the analysis of literature in view of the different harmful factors.Engineering examples of blasting scheme is to use drilling and blasting method of tunnel excavation,the new Austrian law theory construction and the technology of smooth blasting,blasting equipment with two rock emulsion explosive,32mm diameter cartridage and 25mm diameter cartridage.Engineering blasting plan is to use the hole inside and outside differential way as the object to be protected from the explosion area,and as much as possible so that the single dose will be minimized,using with low stage and high stage,with the use of low rank detonators used as hole sequence out to reduce the risk of stone damage initiation network.Based on the grey relational model,the influence degree of the tunnel blasting parameters on the surface buildings is sorted into:single hole charge,hole number,tensile strength,compressive strength,pore size,pore depth.The degree of larger influence of the blasting parameters on the surface building are the single charge,hole depth(round)and the number of holes,and the hole depth and hole number are relate to the single charge.The safety control effect of vibration velocity and vibration frequency on buildings is controlled by controlling the amount of explosive,and then realizing the safety evaluation.According to the theoretical analysis,the tunnel blasting construction along the surface buildings may get damaged,therefore,in the construction practice,through the change of the main blasting parameters such as the single charge control the blasting vibration speed,and achieve safety requirements.According to the monitoring data analysis,and the allowable blasting vibration velocity is less than 2.5cm/s,a and K can be calculated between the four protected and blasting distance R under the condition of maximum charge are 9.5kg,15.3kg,6.6kg,8.3kg.According to the requirements of the project,the safety evaluation of the influence of the tunnel blasting construction on the surface buildings is carried out.