Blasting Vibration Safety Criterion Analysis with Equivalent Elastic Boundary: Based on Accurate Loading Model

Qingwen Li,Jianghui Dong,Gautam Dasgupta,Liping Wang,Siwei Ma,Lan Qiao

doi:10.1155/2015/604683

Abstract

In the tunnel and underground space engineering, the blasting wave will attenuate from shock wave to stress wave to elastic seismic wave in the host rock. Also, the host rock will form crushed zone, fractured zone, and elastic seismic zone under the blasting loading and waves. In this paper, an accurate mathematical dynamic loading model was built. And the crushed zone as well as fractured zone was considered as the blasting vibration source thus deducting the partial energy for cutting host rock. So this complicated dynamic problem of segmented differential blasting was regarded as an equivalent elastic boundary problem by taking advantage of Saint-Venant’s Theorem. At last, a 3D model in finite element software FLAC3D accepted the constitutive parameters, uniformly distributed mutative loading, and the cylindrical attenuation law to predict the velocity curves and effective tensile curves for calculating safety criterion formulas of surrounding rock and tunnel liner after verifying well with the in situ monitoring data.

Highlights

With the rapid infrastructure development in China, the improvement of control level on the blasting technique, and the well adaptability in various engineering, the blasting construction are used more and more widely; the drill and blast method has been becoming the most primary method in tunneling and underground space construction; in China, there are more than 95% mountain tunnel constructions which adopt the drill and blast method [1]
For the tunnel liner, it is easy to learn that the peak velocity is 2.719 and maximum effective tensile stress is 0.7434 from Figures 12 and 13
For the tunnel liner, because there was a damage zone caused by excavated stress resilience and before blasts, the damage scale was D = 0.2 which was calculated by Mazar damage model based on the field fracture surveyed, so the safety criterion formula of the damage tunnel liner is σt∗

Summary

Introduction

With the rapid infrastructure development in China, the improvement of control level on the blasting technique, and the well adaptability in various engineering, the blasting construction are used more and more widely; the drill and blast method has been becoming the most primary method in tunneling and underground space construction; in China, there are more than 95% mountain tunnel constructions which adopt the drill and blast method [1]. Some new methods are used to analyze the blasting problem, such as the soft computing method [19], artificial neural networks method [20], MEMS-based commutation module, [21] and RES-based model [22] It should be based on large number of in situ monitoring data, not considering the effect of vibration frequency and duration. The tensile stress tends to be greater than critical dynamic tensile strength which is usually less than 1/10 compression strength of rock masses, to lead to the radial fractures formed After those radial fractures connected with crushed zone, the blasting gas which looked like a wedge entered the radial fractures to make them enlarge. A 3D model in finite element software FLAC3D accepted the parameters to predict the velocity curve and effective tensile curve for confirming safety criterion after verifying well with the in situ monitoring data

Equivalent Boundary of Elastic Seismic Loading

Continuum Damage Mechanics

Equivalent Process of Blasting Loading

Project of Case Study

Numerical Simulation Analysis

Conclusion