Numerical analysis of a longwall mining cycle and development of a composite longwall index

Longwall mining is the most profitable and safe coal extraction method from deep seated deposits. Understanding the interaction between powered supports, surrounding rock and coal strata is the key for successful operation. In this respect, numerical modelling techniques provide great insight into the behaviour of shield support especially loading behaviour of hydraulic leg and canopy under different geo-mining conditions. This study proposes a methodology to incorporate the process of web-cutting into the modelling environment with the application of user-defined setting pressure. As a result, displacements, strains and stresses those developed in the shield and surrounding rock strata after web-cutting can be obtained for any pre-defined setting load. All together 216 three dimensional numerical models are analysed by varying different roof parameters and setting pressures. The paper also develops a statistical procedure to combine all input parameters into an index termed as “Longwall Index” for determination of axial strain and load that may develop on hydraulic legs of the powered support.