ABSTRACT

: A new geomechanical modeling technique is presented in which the models can generate seismicity from induced cracks and fractures. Seismic source locations, magnitudes and mechanisms can be calculated presenting a unique possibility for model validation. The seismicity produced by the models can be compared directly with seismic source information recorded in field studies to assess whether or not the models are behaving in a realistic manner and could therefore be used in future analytical or predictive studies. Two example applications are presented: an underground excavation in granite, and a waste re-injection (hydrofracture) simulation in mudstone. Semi-quantitative comparisons are made between seismicity produced by the models and the actual seismicity recorded in the corresponding field studies. Although some discrepancies exist, the agreement between the modeled and the actual seismic source information is generally good, giving confidence that this technique could be used in further geomechanical investigations.

1 INTRODUCTION

Seismic monitoring is becoming an increasingly popular technique for remotely sensing cracking and fracture growth in rock. Microseismicity that is recorded during rock engineering endeavors can delineate areas of degradation in rock quality and can indicate areas of potential strength reduction, increased permeability, fracture growth and failure. However until recently, we have not had the capability to model these processes (analytically or numerically) and therefore explanation of the mechanisms leading to cracking and failure have been made only through seismological techniques or direct observation. A new micromechanical numerical modeling package (the Particle Flow Code, or PFC) now allows us to directly model cracking and failure in rock and the resulting seismicity so that comparisons can be made with actual microseismic data recorded in the field.

This content is only available via PDF.
You can access this article if you purchase or spend a download.