Vibration influence on adjacent subway tunnel excited by blasting of brace system of foundation pit

To study the vibration influence on adjacent subway tunnel excited by blasting of brace system of foundation pit,a blasting model is established by dynamic finite element method,which includes the location,magnitude and time history properties of blasting force.Nonlinear analysis on subway tunnel vibration excited by blasting of brace system of adjacent foundation pit is done under the conditions such as different surrounding rocks,different spacing between foundation pit and tunnel,and so on.The analysis shows:the maximal vibration value is on the side wall of the tunnel lining towards the blasting location;the vibration velocities of tunnel lining decrease along with the increase of spacing between foundation pit and tunnel;the relation between the vibration velocities of surrounding rocks and the distance from foundation pit to tunnel is non-linear,which is related with the rock types and blasting conditions;the stabilities of surrounding rocks have a significant damping effect on the vibration waves;when the triangular distribution load achieves its peak value,the time that tunnel achieves its peak response has a delay,and the more stable surrounding rocks are,the more longer the delay time is;when the blasting load is unloaded,the tunnel's free vibration is related with the types of surrounding rock,and the more stable surrounding rocks are,the faster vibration attenuates.