Excavation unloading of foundation pit will lead to additional stress in adjacent subway tunnels. Excessive additional stress will cause instability of subway tunnel, and then affect the safety of subway operation. In order to study the influence law of additional stress on tunnels, the calculation formula of tunnel additional stress caused by foundation pit excavation is derived by using Mindlin theoretical solution and is verified based on the excavation project of a foundation pit group near a subway tunnel in Hangzhou. Then, the influence of three factors, including tunnel depth, horizontal distance between tunnel and foundation pit, and angle between tunnel and foundation pit, on additional stress in tunnel is analyzed. The research results show that: (1) with the increase of tunnel depth, the vertical additional stress of tunnel increase while the horizontal additional stress decrease, and the vertical and horizontal additional stress will decrease with the increase of the horizontal distance between tunnel axis and foundation pit; (2) during excavation of foundation pits, with the increase of horizontal distance between tunnel and foundation pit, the influence coefficient of tunnel depth on vertical additional stress decreases gradually, while the influence coefficient of tunnel depth on horizontal additional stress decreases first and then increases; (3) the vertical and horizontal additional stresses increase with the increase of the angle between tunnel axis and foundation axis, and the additional stress of the tunnel is mainly caused by excavation of the foundation pit which is the closest; (4) with the increase of the distance between tunnel axis and foundation pit axis, the reduction rate of vertical additional stress caused by pit group excavation is smaller than that caused by single pit excavation, while the reduction rate of horizontal additional stress caused by pit group excavation is larger than that caused by single pit excavation.

In order to reduce the dynamic disturbance of adjacent structures caused by blasting construction of foundation pit by using blasting, field test to study the vibration reduction law of the blasting barrier holes was conducted relying on the blasting construction project of foundation pit of No. 1 comprehensive well of Shenzhen Metro Line 16. Based on monitoring of the ground vibration under different blasting barrier hole parameters, influence of blasting barrier hole on peak velocity and dominant frequency of particle vibration on the ground and the influence of parameters of blasting barrier hole on its vibration barrier effect were analyzed. It is found that when the diameter of the blasting barrier hole increases, the vibration isolation rate of vibration barrier hole (VIR) in horizontal radial and horizontal tangential directions increase first and then decrease, the VIR in vertical direction increases and the VIR based on resultant velocity increases. Furthermore the VIR decreases first and then tends to be stable with increase of the row spacing of the damping vibration barrier holes. In addition, when the proportion of water filling in the blasting barrier hole increases, the VIR in horizontal radial direction decreases, the VIR in horizontal tangential and vertical directions increase first and then decrease, and the VIR based on resultant velocity increases first and then decreases.