Research On Blasting Dynamic Response And Impact Zoning Of New Tunnels Under Hard Rock Formations Approaching Existing Tunnels

With the implementation of my country’s strategy of strengthening the country in transportation,a series of close tunnel projects usually appear near large transportation hubs.In order to absolutely guarantee the safety of the existing operating lines,such access tunnels often require non-blasting excavation methods or strictly limit the blasting vibration speed,but simply using mechanical excavation or strictly limiting the blasting vibration speed will cause serious delays in the project.There is even a dilemma of being unable to excavate under hard rock formations.In view of this,this paper relies on the downlink connecting line of Fuxia passenger train entering the island—the new Tai Mo Shan No.1 and No.2 tunnels pass through the existing new Liutang No.1 tunnel as the project support.From the perspective of energy method,combined with concrete Material properties and failure criteria of surrounding rock,comprehensively using theoretical analysis,numerical calculation,laboratory test,field test and other research methods to study the blasting vibration response and impact partition of hard rock formation close to tunnel.The main research contents and research results are as follows:(1)Based on the energy principle,the energy input,conversion and release process of concrete lining structure under the action of blasting seismic wave are deeply studied.The theoretical result of using twice the peak kinetic energy to replace the maximum elastic strain energy is proposed,which is referred to as "twice the peak kinetic energy method",and the correctness of the theoretical result is verified by numerical calculation.Combined with the characteristics of concrete materials,the blasting vibration safety criteria of concrete without damage and damage are put forward.(2)Based on the "double peak kinetic energy method",according to the design value of tensile strength of different types of concrete,the blasting vibration speed control threshold of different types of concrete suitable for engineering judgment is calculated through the formula.(3)According to the blasting vibration speed control threshold of different types of concrete,this paper gives the blasting vibration influence zoning standard applicable to the supporting project,which is divided into three categories: strong influence area,weak influence area and no influence area.The supporting project is divided into influence areas,it is determined that the supporting project belongs to the scope of weak influence area,and the blasting vibration influence zoning of single track railway tunnel under different charge quantities is calculated,Finally,the blasting vibration influence zoning of single track railway tunnel in hard rock stratum is obtained.(4)The physical and mechanical parameters of the on-site rock mass are obtained through the rock mechanics test,and the blasting vibration response law of the supporting project is studied.The research shows that the blasting of the new tunnel has a great impact on the existing tunnel above the excavated section,and the vibration velocity attenuation of the existing tunnel above the excavated section is slower than that of the unfinished section.The research results have guiding significance for the on-site construction and monitoring.(5)The field tests of "single hole and single sound control blasting + damping hole" and "single hole and single sound control blasting + rope saw cutting" above xindamaoshan No.1tunnel are carried out,and the damping efficiency and blasting parameters of the two methods are obtained.The research results can be used in xindamaoshan No.1 Tunnel and xindamaoshan No.2 tunnel under the existing xinliutang No.1 tunnel.