Quantification of Rock Damage from Small Explosions and its Effect on Shear-Wave Generation: Phase I - Homogeneous Crystalline Rock
Abstract
We are currently conducting a one-year feasibility study to determine the most efficient way to characterize the damage from an explosive source and to identity the source(s) of shear wave generation. We hope to quantify crack nucleation and growth (Ashby and Sammis, 1990) as an S-wave generation mechanism in the far-field (Sammis, 2002) and to map the cone of damage (Patton et. al. 2005; Stevens et. al. 2003) above a source, modeled by a compensated linear vector dipole (CLVD). This study is being conducted at a quarry in Barre, Vermont, in a granite body that has a low fracture density and typically forms large blocks used for monuments. In this study, we are detonating five small (<200 lb) explosions at depths of approximately 9, 12, and 17 m each separated by at least 20 m so the damage zones do not overlap. We plan to use two different types of explosives in order to provide different fracturing in the rocks. An ammonium nitrate fuel oil (ANFO)-Emulsion mixture with a slow velocity of detonation (VOD) should produce larger length cracks while a molecular explosive with a high VOD should produce a large rubble zone near the borehole and cracks of smaller lengths. We are quantitatively and qualitatively defining the damage around the source using coring, cross-borehole seismic tomography, and borehole televiewers before and after the explosions. We will also deploy a large network of accelerometers and seismometers from S m to 30km from each blast. These Stations will include near-source (<1 km) accelerometers and short-period seismometers that will record the physical characteristics of the primary seismic pulse created by the explosions. We will also deploy two linear arrays of intermediate and short-period sensors in order to track the P- and S-waves energy partitioning from the explosions with hopes of relating the observables hack to the variation in damage caused by the explosions. The explosions are planned for July 2008.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2008
- Accession Number
- ADA487736
Entities
People
- Dorothy Richter
- James F. Lewkowicz
- Jeffrey A. Reid
- Jessie L. Bonner
- Mark Leidig
- Peter Boyd
- Randolph J. Martin
- Robert Garfield