Computational method of blasting charges under different vibration velocity limits of buildings and structures around tunnel

Vibration velocities allowed for different buildings and structures around tunnel which is excavated by blas- ting are different in urban area. The computation of blasting charge which could control different vibration velocities within the value allowed for all nearby buildings was very difficult for blasting design in the past. With a case study of the tunnel blasting engineering in Chongqing city,the space loci equations of tunnel and the building protected outline are established. The functional relationship of the blast charge and tunnel site are respectively studied under three safe vibration velocities corresponding to the subway,the historic building and other buildings. The tunnel curve is divided into several sections by lengthening the building outline,the function about blasting charge and tunnel location is de- duced for the historic building outside the tunnel. The blasting charge which vibration is controlled within safety stand- ard is obtained by formula on the basis of space distance from detonating site to the line of subway. The blasting charge for other buildings is calculated based on that the ground above tunnel is distant from blasting point on the condition of vibration speed allowed. These three charge values at every position of the tunnel are calculated by Matlab program, and the minimum of three values is selected as the design blasting charge.