Based on Xiannüyan tunnel blasting engineering of the high-speed railway from Xi’an to Chengdu passing through a buried gas pipeline, the 3-D dynamic finite element model for tunnel blasting including the empty zone of the pipeline was established. Under the action of blasting seismic waves, the dynamic response law of buried gas pipeline with different lengths of empty caused was studied thoroughly and comprehensively. The results show that when there is clearance between the lower part of the buried pipeline and the surrounding soil, the peaks of vibration velocity and displacement at the bottom of the pipeline are greater than that of the top of the pipeline and these two parameter values are gradually decreasing along the axis of the pipeline with the center point of the empty zone as the point of symmetry. With the increase of the length of empty zone, the maximum vibration velocity of the pipeline decreases slowly, but the maximum vibration displacement shows a rapid increase. Under the blasting vibration, the peaks of the effective stress and the maximum principal stress occur at the bottom of the pipeline near the center of the empty zone and both of them increase almost linearly with the increase of the length of the longitudinal empty zone of pipeline. Under the condition of the operating internal pressure 6 MPa and the tunnel depth 40 m as well as the maximum charge per delay interval 17 kg, when the length of the empty zone is 5 m, the blasting vibration does not affect the operation safety of the pipeline. When the long-distance gas pipeline is operated at a high pressure of 10~12 MPa, the blasting vibration will reduce the safety reserve of the pipeline.

In order to control the forming effect of excavation profile and reduce the disturbance of preserving rock mass caused by blasting, the foundation pit blasting at the Yunnan bank of the large arch bridge across Jinsha river, whose total depth is about 51 m and one-time excavation depth is about 20 m, is taken as the engineering background. Reinforced loose blasting with hole-by-hole initiation was applied to the main blasting holes and smooth blasting was used for the contour holes. A kind of deep hole smooth blasting technology which can be applied to foundation pit excavation of the deep and steep arch bridge is presented. In addition, the action process of gas, the expansion pressure at the hole wall and the damage range of the smooth blasting hole were theoretically calculated and analyzed. The blasting results show that a flat excavation profile, with more than 90% half-hole ratio of relatively intact rock mass and less reserved hole marks of relatively cracked rock mass whose overbreak and underbreak can still be controlled, can be formed by using the deep hole smooth blasting technology, which greatly reduces the stress concentration on the rock wall surface. The crushing zone will not be formed near the charge section in the smooth blasting and the maximum damage range of the reserved rock mass was about 49cm, which fully ensured the rock wall stability and construction safety. In the process of smooth blasting construction, engineering measures were also taken to ensure the reliability, safety and economy, including slowly tilting the excavation surface at the bottom of the bench to the free surface, tying the explosive charge with cotton rope for traction, and setting detonators inside and outside the hole every 5~7 smooth blast holes.