Laserfiche WebLink
of infinite extent because no boundaries are contacted. radial ground-water flow toward a circular mine pit. <br /> Numerical simulations are useful for evaluating more The analytical solution for head in the aquifer adjacent <br /> complex flow systems such as heterogeneous or aniso- to a circular pit of radius rp is given as: <br /> tropic hydraulic-conductivity distributions, multiple <br /> boundary conditions, and transient conditions. Numer- <br /> ical methods may be required during advanced stages r , —r <br /> of mine planning when more detailed geologic and h= h 2 + W r.2 In r — n (2) <br /> hydrologic data are available for a site (Marinelli and Kh P 2 <br /> Niccoli, 2000). Analytical and numerical methods can <br /> be coded into computer programs to facilitate their <br /> use. where <br /> Both analytical and numerical simulation <br /> methods were used in this study to evaluate the steady- h is saturated thickness above the pit base at r(radial <br /> state (time-invariant)effects of mining aggregate on distance from pit center) [LJ, <br /> water-table conditions. A steady-state two-dimen- hp is saturated thickness above the pit base at rp(at <br /> sional analytical solution to the ground-water flow the mine wall) [L], <br /> equation by Marinelli and Niccoli (2000) and a steady- W is distributed recharge flux [L/T], <br /> state one-dimensional analytical solution derived KI, is horizontal hydraulic conductivity of <br /> during this study were used to estimate the extent of surrounding geologic materials [UT], <br /> drawdown around a mine in a homogeneous, isotropic r; is radius of influence(maximum extent of the <br /> aquifer of infinite extent. The U.S. Geological Survey cone of depression) [L], <br /> modular ground-water model, MODFLOW-2000 r is radial distance from pit center [L], <br /> (Harbaugh and others, 2000), was used to evaluate rp is effective pit radius [L] (fig. 3). <br /> steady-state effects of aggregate mining under more <br /> Given input values of hp W, KI2, rp, and initial <br /> complex hydrogeologic conditions. (premining) saturated thickness above the pit base <br /> The steady-state two-dimensional analytical (h=ho), the radius of influence(r)can be determined <br /> solution of Marinelli and Niccoli (2000)estimates through iteration by setting r equal to r; . Once rl is <br /> Land Surface <br /> Center W <br /> of Pit 1 1 1 1 <br /> ho h <br /> h <br /> Kh ho <br /> 4 <br /> Mine Pit hp 4- Q <br /> ~ No-Flow Boundary <br /> Radial Distance from Center of Piti - r <br /> 0 rp ri <br /> Figure 3. Conceptual diagram of the Marinelli and Niccoli analytical solution <br /> (modified from Marinelli and Niccoli, 2000). <br /> GROUND-WATER HYDRAULICS AND MATHEMATICAL METHODS 7 <br />