Relationships between Field, Experimental Strengths or Their Ratios and Excavating Depths of Rock Masses in Datun Coal Mining Area

摘要

By experimental results for mudstone under the seventh coal seam and sand mudstone of the eighth coal seam In Datun mining area, their uniaxial compression strengths have no relationship with mining depth. Field compression strengths of these strata are not only no more than their experimental strengths, but also all descending with Increasing excavation depths. Especially, the rock masses will represent soft rock in engineering as mining depth has been beyond 800 meters. That determining compression strength ratios of rock masses in situ to that In laboratory is an important reference for experimental results being used In real engineering, especially in deeper underground engineering. Strength ratios of rock masses in Datun coal mining area are about 75% In depth range from 300 to 600 meters and only 30% in depth range from 800 to 900 meters respectively. To mudstone under the seventh coal seam which mining depth is particularly deep or property is relatively weak, characteristic of strength ratio's decline with mining depth's increase should be more distinct. Studying results involving rock strata under coal seams In Datun coal mining area may be used to determine their strengths in situ.