Method of Investigations, Estimation and Classification of Roofs in Mines in the United States of America for the Selection of Suitable Mechanized Support for Longwalls. Report No. 2. State-of-the-ART Report on Roof Rock Stability

摘要

The survey of methods presented in this report covers: tests and classifications of rocks with respect to their stability in underground workings, principles of selection of longwall-face supports adjusted to roof rocks and the classification of roofs for natural mining hazards evaluation. It is argued that tests on bed separation resistance of roof rocks are necessary for prediction of roof behavior at longwall faces. As rock resistance to falling due to gravity action is an important roof parameter, a method and apparatus were developed at the Central Mining Institute for detailed measurements of bed separation resistance. On account of the fact that in US coal mines the average roof rock strength is considered higher than in Polish mines, development of a penetrometer redesigned to work under high pressure conditions is fundamental. The range of the pressures required should be determined by preliminary measurements of rock strength in US coal mines. (ERA citation 08:022978)