Investigation on the evolution and control of surrounding rock fracture under different supporting conditions in deep roadway during excavation period

Abstract

This paper presents an investigation of fracture evolution of surrounding rock with different supporting conditions during excavation period in Hulusu coal mine, Inner Mongolia, China. Fractures of surrounding rock were measured by borehole images obtained with a digital panoramic borehole camera, and surface displacement of roadway was measured using the intersection point method. Based on the rock properties, original support method and constructional process of bolter miner, a simple and fast support system was proposed, which realized the complete parallel operation between bolt support and coal cutting. According to the data obtained from field monitoring and construction situation, the array pitch was extended from 1.0 m to 1.5 m gradually. Field measurements indicated that the overall effect of roadway under new support was more satisfactory than under original support, with no exception in all the five test stages. When the array pitch extended up to 1.5 m, the roof and rib convergence were 11 mm and 16 mm, a reduction of 66.7% and 57.9%, respectively. Under new supporting condition, fractures were distributed only within the bolt anchorage zone and both the number and opening of fractures were small. By contrast, under original supporting condition, fractures were distributed both in and out of the bolt anchorage zone. New support can make full use of deep strata by constructing thick anchorage rock beam, and large displacement of shallow strata can be inhibited through small displacement of deep strata. The realization of co-movement between large-small displacements ensures the safety control of roadway. New support can greatly improve support efficiency, providing a solution to the imbalance between excavation speed and production needs widely existing in coal mines producing 10 million tons a year. New support has already been successful applied in another roadway with top coal in Hulusu coal mine.