NUMERICAL SIMULATION OF BLAST-INDUCED VIBRATION PROPAGATION AND DEVELOPMENT OF REPRESENTATIVE ATTENUATION CURVE

Abstract

Blasting is widely used in construction projects including tunneling, road construction, and excavation. A major concern is the high level of vibration, which may potentially damage adjacent structures and facilities. Empirical and theoretical far-field attenuation relationships, which do not capture the near-field response, are used to predict the peak amplitude of blast waves. Rigorous wave equations that simulates the near-field attenuation to spherical and cylindrical blast sources in damped and undamped media. However, the effect of loading frequency and velocity of the media have not yet been investigated. Additionally, the equations are difficult to use in practice because of their complex forms and the need to use dedicated computational code to calculate the response. This study performed a suite of axisymmetric, dynamic finite difference analyses to simulate the propagation of stress waves induced by spherical and cylindrical blast sources and to quantify the near-field attenuation. For a spherical source, a broad range of loading frequencies, wave velocities, and damping ratios are used in the simulations. The near-field effect is revealed to be proportional to the rise time of the impulse load and wave velocity. An empirical additive function to the theoretical far-field attenuation curve is proposed to predict the near-field range and attenuation. The proposed curve is validated against measurements recorded in a test blast. This study also performed a suite of analysis for various cylindrical sources. The ratios of fractured length and radius, depth of the blast source, and the damping ratio are varied. It is revealed that the stress attenuation is so different depending on the ratio of fractured length and radius, the damping ratio, and the load type. The attenuation curves in far-field are closely compared to those for a spherical source. The results are shown to be dependent on both fractured length and load