Abstract

Deformation induced at roadway's roof depends on many factors such as: rock properties, roadway dimensions, excavation method, stress field existing in rock layers above the roadway, etc. The present paper analyses the relationship between the state of stresses and deformation induced in the roof of roadways, which driven through layered strata, in cases of the roadways excavated in conventional conditions and closed to an exploited area with small width of coal pillar, where pressures in the collapsed area has been stabilized.

Analysis results indicate that the increase in the width of the roadway and strata pressure acting from surrounding rock cause the increase in deflection and strain in rock mass at the roof, and vice versa. Without considering the influence of lateral pressures and with the same roadway's dimensions and strata pressures, deformation estimated at the middle point of the roadway's roof in case of excavating through exploited area is twice larger than that observed in case of excavating in conventional condition.

Due to the different deflection of rock layers, observed deformations are also different depending on rock mass parameters. Small deflection resistance of weak rock mass causes the large deformation and vice versa.

1. Introduction

Thin coal seam and rock stratification is one of the most popular forms during excavation of the roadway to serve the coal mining activity. Rock layer is considered as thick layered when its thickness is greater than 0.4m. The roadways excavated in the thick layered rocks are often relatively stability. Rock strata is considered as thin layers when its thickness is less than 0.4m [1]. The width of serving roadways in coal mining are usually of about 3 ÷ 6m. When the ratio between the thickness of rock layer and the width of serving roadway is less than 1/7, the roadway is designed to excavate through thin-bedded layered rocks [2].

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