Volume 28, Issue 2 (March 2005)
Blast-Induced Stress Wave Propagation and Attenuation: Centrifuge Model Versus Prototype Tests
This paper presents results of centrifuge model studies and full-scale field (prototype) studies designed to provide insights into the influence of water content and the degree of saturation during compaction and testing on high-strain rate loading response of medium dense sand. Objectives of the study were to determine the influence of moisture content at the time of compaction on blast-induced ground shock and stress wave propagation and to compare centrifuge model explosive tests with prototype explosive tests. Model testing was conducted using a geotechnical centrifuge to simulate prototype testing conducted at a field explosives test site. Centrifuge models were constructed at scales of 1/26.3 and 1/18.9 and tested at acceleration levels of 26.3 and 18.9 times earth's gravity. Explosives consisting of 3.50 × 10−4 kg (350 mg) and 1.031 × 10−3 kg (1031 mg) of PBX 9407 were buried at depths of 76 mm and 54 mm, respectively. These scaled model tests simulated prototype tests in which 7-kg TNT equivalent explosive charges were detonated at a depth of 1.4 m. Specimens were compacted to a dry density of 1635 kg/m3 at degrees of saturation ranging from 0 to 60 % (water contents from 0 to 14.4 %). Centrifuge model tests and the prototype tests showed similar results. Peak particle velocity, peak stress, and peak scaled acceleration were found to be a function of the degree of saturation with the lowest values at 0 % saturation. Lowest attenuation coefficients occurred in the sand compacted at degrees of saturation of 13 % for the centrifuge tests and 20 % for the prototype tests. Highest attenuation coefficients occurred in the sand compacted dry and at 60 % saturation for all the prototype tests and most of the centrifuge tests. Attenuation coefficients generally decreased with increasing seismic velocities.