INTRODUCTION
ABSTRACT:

A PC based computer model has been developed by the authors for predicting the surface subsidence due to underground coal mining. Its reliability, comprehensiveness and user friendliness demonstrate that it is a good tool for the mine operators, government agencies and scientific researchers alike.

The problems induced by surface subsidence due to underground coal mining, especially when the highly productive longwall mining method is employed, have prompted the need for a reliable tool to predict the surface subsidence for mine operators, government agencies and scientific researchers. This paper introduces a PC based computer subsidence prediction model which has been developed by the authors. The model is called CISPM (Comprehensive, Integrated Subsidence Prediction Model). The computer model is comprehensive, reliable and user-friendly. It is comprehensive because the model predicts the final surface subsidence for rectangular or irregular underground extraction openings, predicts the dynamic subsidence for operating longwall panels, recommends subsidence parameters, which are critical to prediction accuracy, based on the available geological information or the collected subsidence data, and processes the subsidence survey data. The reliability of the model has been proven by a number of individual investigators. An in-depth knowledge on computer usage and subsidence theory is not required to use the model.

CISPM consists of six main programs, namely

MINIMUM HARDWARE REQUIREMENTS
LWSUB, SUBSDNC, DYNSUB, SURVEY, SUBDED and CONSULT

. All the programs are menu-driven.

  • An 80 column dot-matrix printer.

FINAL SUBSIDENCE ON FLAT OR MODERATE SURFACE

Theory

The extraction of a tiny element of underground coal seam will cause the surface to subside. The surface point directly above the extracted element receives the largest subsidence. The farther the surface point offsets this element horizontally, the less amount the surface point will subside. The mathematical function which describes the distribution of the subsidence influence to the surface due to the extraction of a tiny element is called the influence function. In our model, the normal probability distribution function is used as the influence function (Knothe 1957). The final subsidence at a surface point is the summation of the subsidence influence offered by extracting the entire mined-out area element by element, or calculated by integrating the influence function over the entire mined area (A), as

(available in full paper)

The spatial relationship among the subsidence parameters are shown in Fig. 1. The offset of the inflection point (d) is defined as the horizontal distance between the panel edge and the surface point where half of the maximum possible subsidence is observed and also the subsidence-induced curvature turns from concave to convex.

Fig. 1 Spatial Relationship Among the Subsidence Parameters (available in full paper)

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