RESEARCH ON BLASTING VIBRATION EFFECT AND MECHANICAL CHARACTERISTICS OF SMALL SPACING AND LARGE SPAN TUNNEL BASED ON SAFETY AND ENVIRONMENTAL PROTECTION PRINCIPLES

摘要

Tunnel blasting is the basis for ensuring the safety, quality and schedule of construction. Adopting practical blasting technology w ill effectively reduce the adverse effects caused by tunnel blasting v ibration. In this paper, taking the Tuanshan Tunnel of the East Lake Passage in China as an example, the vibration effects and mechanical characteristics of the surrounding rock and the in itia l support structure of the small-spacing, large-span tunnel under the blasting dynamic load are system atically studied. According to the on-site stratum characteristics, a blasting construction plan is made. This method takes into account the mechanical behaviors such as vibration velocity, distribution of surrounding plastic zone, displacement, and internal force of the in itia l supporting structure. FLAC3D software is used to perform two-dim ensional elastoplastic analysis of tunnel blasting dynamic response. The dynamic response of tunnel surrounding rock and in itia l supporting structure under blasting vibration is analyzed. In addition, based on the experiment of controlling blasting vibration, the safety of the surrounding rock against vibration is evaluated based on the field measurement results. The research results show that the numerical sim ulation and field measurement results are in good agreement. The surrounding rock of the tunnel s till has good stability under the blast v ibration disturbance. The maximum vibration speed of the in itia l support of the tunnel is 4.92 cm/s, which meets the requirements of the specification and the structure has good anti-vibration stability. The maxim um vibration velocity measured at the controlled blasting site was 1.16cm/s. Through long-term monitoring of the subsidence of the tunnel arch, the maxim um subsidence of the tunnel arch is 25.2 mm, so the project has achieved good results.