Abstract:

Estimating the height of longwall mining induced strata fracturing and the height of complete groundwater drainage is a contentious issue and there seems to be some misconception and misunderstanding among the practicing engineers and groundwater modelers. With the introduction of the longwall top coal caving (LTCC) in a number of mines in Australia in recent times, this knowledge gap has significantly widened, creating extra demand for rigorous study and the development of more sophisticated and reliable assessment tools. The extent of mining induced subsurface deformation, fracturing, surface subsidence, and aquifer interference is largely controlled by local lithological conditions, mining methods and mine layouts. Thus it is imperative to develop methods/tools that, unlike empirically based strata desaturation height estimation methods, can properly consider all factors and accurately predict strata deformation and subsequent fracturing (particularly connective fracturing) in varied hydrogeologic environment to assess the impact of mining on groundwater.

The demand for more sophisticated and detailed mining impact assessment tools is ever increasing. This paper will describe the use of mine site monitoring data and a coupled Distinct Element / Finite Element (DEM/FEM) model to assess strata fracturing during longwall extractions. The approach of coupling FEM and DEM methods significantly extends the capability of DEM codes, allowing large scale simulations of practical problems such as longwall mining.

Introduction

Predicting the height of connective fracturing and complete water drainage above mined longwall panels is not well understood and still remains a strongly contested topic among the practicing hydrogeologists, mining engineers and groundwater modelling professionals. The increasing need for rigorous environmental impact assessments creates a demand for the study and development of more sophisticated and reliable groundwater tools. The extent of mining induced subsurface deformation, fracturing, surface subsidence, and aquifer interference is largely controlled by local lithological conditions, mining methods and mine layouts. Thus it is imperative to develop methods/tools that, unlike empirically based strata desaturation height estimation methods, can properly consider all factors and accurately predict strata deformation and subsequent fracturing (particularly connective fracturing) in varied hydrogeologic environments to consider the impact of mining on groundwater.

This content is only available via PDF.
You can access this article if you purchase or spend a download.