Development of an Entry-Scale Modeling Methodology to Provide Ground Reaction Curves for Longwall Gateroad Support Evaluation

Abstract

Longwall gateroad entries are generally subjected to severe mining-induced stress changes and deformations; they are prone to large roof falls, floor heaves, and rib sloughing. The standing support system in underground mines needs to be carefully designed to compensate for the mining-induced deformation of the surrounding rock mass and consecutively protect the integrity of gateroad entries. Local geology, together with mining-induced stress redistribution, influences the ground response and plays a major role in the performance of a standing support design. In the US, Support Technology Optimization Program (STOP) and its Ground Reaction Curve (GRC) design criteria have been applied to evaluate the performance of the standing support systems. The ground reaction curve of a gateroad entry is a function of geology and stress states, and it can be used to assess the influence of local geology and stress states on standing support performance. However, at present, measuring GRC in an underground mine remains impractical, and only a few GRC samples are available in STOP. In this research, to extend the GRC database and develop local geology and stress-dependent GRC for various geological and operational conditions, an entry-scale modeling methodology was developed. Four field measurement case studies, including the tailgate, track entry, and crosscut in different underground mines, were used for constructing and calibrating the modeling procedure. Two cases, which are not included in the previous database, were used to verify the modeling procedure. Results from the models were compared to the results measured at the field monitoring sites and, it is concluded that the proposed modeling methodology could simulate the ground response of a gateroad entry and plot a GRC for a specific stress state and geology conditions. Then, the geology and stress-dependent GRC developed for different case study mines were integrated into STOP to evaluate standing support design and verify the approach.