IN SITU STRENGTH AND DEFORMATION CHARACTERISTICS OF COAL

This paper contains details of in situ large scale tests conducted on coal specimens measuring up to 5 × 5 ft. in cross-section and up to 5 ft. in height. Experimental techniques used are described and results of tests aimed at determining the in situ strength and deformation characteristics of coal are given. Stress-strain behaviour of coal is discussed and practical applications of this study to the design of full size coal pillars are dealt with in detail. It is shown that the strength of pillars cannot be expressed by a power function of their width and height as there exists a critical pillar size above which the strength of coal does not change with an increase in pillar dimensions. A new relationship describing the strength of full size coal pillars is presented and its validity verified by experimental data. © 1968.