Laserfiche WebLink
<br />24 <br />represent the permeability of an appror.imately 2 ft. thick fracture zone • <br />and is on the order of 10,000 times greater than the permeability measured <br />on core plugs (Table 1). The storage coefficients shown in Table 2 are <br />typical values for thin, well confined aquifers. <br />No bedrock pumping tests were conducted at the Allen Mine and there <br />is, therefore, no direct way to compare coal seam permabilities at the two <br />locations. However, it is possible to mathematically estimate Inflows to <br />the t•taxwell Mine using the hydraulic properties discussed above and, by <br />comparing with measured inflows at the Allen, establish some insight to the <br />relative magnitudes of the controlling hydraulic properties at the two <br />sites. <br />Mathematical Estimate of Maxwell Mine Inflows <br />The plan-view geometry of the Maxwell Mine will be complex, both during <br />and after mining, and the changing geometry will affect the inflows to the <br />mine. However, the advance of the mine and the precise geometry at a <br />particular time consitute second-order considerations; the length of peri- <br />meter separating the mine workings from the undisturbed ground being the <br />most important aspect. A simple model whereby the total inflow is calcu- <br />lated as the product of the length of perimeter and the inflow at points on <br />the perimeter, obtained by assuming planar flow normal to the perimeter, <br />retains the effects of first order importance. Flow to the mine is derived <br />from storage in the water-bearing zones and is transmitted to the mine <br />primarily through the undisturbed coal seam. <br />Figure 6 is a schematic representation of the flow to the face at a <br />particular point on the perimeter. The steady state distribution of drawdown <br />is given by <br />s=soexp(-8 ) <br />where s = drawdown at a point located a distance x from the face <br />s =drawdown at the face <br />o <br />