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predict the location of the inflection point in the <br />• subsidence profile over the rib side. <br />4. Influence functions: these were originally derived from <br />the earlier work in stochastic media. Their basis is in <br />evaluating the influence of extracting infinitessimal <br />elements of area. The subsidence at any given point on <br />the surface is determined as a function of the distance <br />to and its relative position with respect to the <br />extracted area. The initial problems with accurate <br />prediction of subsidence profile over the rib side have <br />been largely overcome with minor modifications to the <br />basic equation (Mary, 1975). <br />• 5. Phenomenological models: these models are generally <br />based on continuum theory and involve modelling of <br />either elastic or elasto-plastic deformation. Extended <br />to a higher degree, this would include the Finite <br />Element Numerical Methods. <br />6. Distinct element method: this is a numerical technique <br />which involves the modelling of the motion of discrete, <br />rigid blocks of material. <br />The empirical methods, although easy to use, have severe <br />limitations with respect to their use with complex mine <br />• geometries or complex topographic conditions. The <br />phenomenological models or continuum methods have severe <br />14 <br />