Ground response curves for longwall support assessment

Abstract

This paper presents the ground response curve concept as a means to provide graphical representation of longwall support and strata interaction processes. The approach was developed to address the requirement for a practical longwall support evaluation and selection tool that can take account of support load influences such as changes in roof geology or cover depth. Several factors can be investigated including different setting and yield loads, canopy tip-to-face distance, support width, coal seam strength influences, hydraulic supply pressure variations and load variance over the support life. An example is given for load specification of new longwall supports at an Australian underground mine. One major advantage of the approach is its ability to represent graphically typical longwall support response from real operating data. A rudimentary strata-support interaction diagram can usually be derived using measured support leg pressure values, leg stiffness test data and routine underground observations. Numerical modelling can also be used to assess the impact of variance on various support load influences. A key outcome of recent studies has revealed the importance of coal seam stiffness and strength and its role in strata deformation and load transfer about the longwall face.