Modeling cave propagation in deep block caving by incorporating the fracture zone inferred from seismic tomography

Purpose. This study aims to enhance the monitoring of cave propagation in block caving developments by integrating microseismic tomography for numerical modeling of rock mass evolution due to mining and displacement distribution. Methods. This study used the low-velocity zone identified by four-dimensional tomography as a fracturing or loosening zone near the cave boundary. The elastic properties of the fractured zone were adjusted to analyze their impacts on stress and displacement distribution. The displacement models for each scenario were validated using observed time-domain reflectometry (TDR). Findings. The reduction in rock mass deformation modulus, inferred from decreased seismic wave velocity, produced a displacement distribution consistent with Time Domain Reflectometer (TDR) measurements. The quantified reduction in rock mass deformation modulus within the zone of loosening or low velocity (4.5 km/s) was approximately 0.5 times the intact rock modulus. The northwestern cave boundary, predicted to expand, was accurately modelled as the rock mass zone with the highest displacement (19 cm), coinciding with the induced stress concentration and high stress-strain localization in that area. Originality. Conventional stress – strain – displacement numerical modeling typically assumes constant rock mass properties. However, during the caving process, extensive fracture growth and extension transform the rock mass from intact to highly jointed, significantly altering its mechanical behavior. This study proposes a new integrated method utilizing rock velocity models from microseismic monitoring to modify the rock mass deformation modulus in numerical modeling, during the fracturing stage under high cave-mining-induced stress conditions. Practical implications. This study successfully optimized the use of microseismic monitoring data to update rock mass conditions within the fracturing zone. This approach allows the elastic properties used in numerical modeling to be time-lapse representative and to incorporate the effects of fracturing progression.