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Calculations for open pits inflow are based on published analytical solutions for the following hydrogeological conceptual schemes:
•Confined aquifer;
•Unconfined aquifer;
•Confined-unconfined aquifer; and
•Leaky aquifer
Most schemes account for I-st or II-nd types of boundary impacts. The aquifer can be modelled as infinite, bounded, stripped or radial (circle-bounded).
The calculations are performed from the graphical window dialog "Pit Inflow". The dialog contains pit sketches in plan and profile as well as required fields for inflow calculations. The module will determine drawdown in a pit, when pit inflow is entered. When entering values in text box "Q, m^3/d" and "t, d"), inflow rate and time can be converted to other units using SHIFT (or CTRL) + MB.
To access this module, use "Hydrogeologist workbench > Pit inflow" or the button "Quick estimates of pit inflow" in the tab "In-Pit sumps" of the dialog window "Pit" (use button "Pit" on the dialog window AMWELLS).
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Dialog window "Pit inflow"
"Q, m^3/d" text box |
Information field showing the result of pit inflow calculations. If pit inflow is entered manually in this field, the calculations are conducted for drawdown |
"so, m" text box |
Drawdown in the pit (the same drawdown is assumed for the whole pit area) |
"ε, m/d" text box |
Recharge rate. This field is required for calculation of Radius of influence using the formula with recharge input |
"Q', m^3/d" text box |
Additional inflow. Use for circle aquifer for Neumann boundary |
"s, m" text box |
Drawdown in an observation well. This field is required for calculation of Radius of influence using the formula with drawdown in the observation well |
"k, m/d" text box |
Hydraulic conductivity |
"B, m" text box |
Leakage factor that is required for the "leaky aquifer scheme |
"H, m" text box |
Hydraulic head that is calculated in meters above the aquifer bottom. This field is required for calculations of confined-unconfined hydrodynamic conditions |
"m, m" text box |
Thickness of confined aquifer or initial saturated thickness of unconfined aquifer |
"ro, m" text box |
Effective radius of the pit. Can be entered manually or calculated (see frame "Pit radius") |
"R, m" text box |
Effective radius of the pit. Can be entered manually or calculated (see frame "Radius of influence"). This field is required for infinite aquifers. For an aquifer with circular boundary the entered value should correspond to the aquifer radius |
"r, m" text box |
Distance from the pit center to an observation well. This field is required for calculations of Radius of influence using the formula with drawdown in an observation well |
"L1, m" text box |
Distance from the pit center to the aquifer boundary (for aquifers with one boundary) or to the 1-st boundary (for aquifers with two boundaries) |
"L" text box |
Width of strip aquifer |
"L2, m" text box |
Distance from the pit center to the 2-nd aquifer boundary (for aquifers with two boundaries) or to the center of the aquifer (for aquifer with radial boundary) |
"Conceptual scheme" list |
Conceptual scheme for an aquifer (i.e. confined, unconfined, confined-unconfined or leaky aquifer) |
"Boundaries" list |
Hydrodynamic boundaries (infinite aquifer, stripped aquifer, square aquifer etc.) and boundary types (Neumann or Dirichlet) |
"Pit radius (ro)" frame |
Options to calculate pit radius using pit area, length and perimeter |
"Area", "Perimeter" text box |
Pit area (perimeter) that is required for calculations of Radius of influence for the non-elongated pits (ratio Width/Length > 0.5) |
"Length", "W / L" text box |
Pit length and its ratio to pit width. These fields are required for elongated pits with Width/Length ratio less than 0.5 |
"Radius of influence" list |
Selects the method of calculation for Radius of influence: manually, using formula with recharge input, water level in observation well or storage properties |
"Transient conditions" frame |
This field is required when Radius of influence is changing with time and is calculated using hydraulic diffusivity (text box "a") or specific yield (text box "Sy") and time (text box "t"). Use this parameter for infinite aquifers and also for aquifers with boundaries that can not be modeled in steady state |
Button "Heterogeneous stratified aquifer" |
For unconfined aquifers. See section "Heterogeneous stratified aquifer" |
Button "Report" |
Creates report. This option is available in Russian language only |
Analytical solutions for calculations of pit inflow (Q) and pit drawdown (so) for confined, unconfined and confined-unconfined aquifers
Boundaries |
Confined aquifer |
Unconfined aquifer |
Confined-unconfined aquifer |
Unlimited aquifer (radius of influence is required) |
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Radius of influence can be estimated outside of the module and entered manually. Other option is to use in-built formulas of the dialogue window: 1) general formula for transient groundwater flow:
2) general formula with recharge: |
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Unlimited aquifer(drawdown in observation well is required ) |
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One boundary of the I-st type (Dirichlet) |
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One boundary of the II-nd type (Neumann) |
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Strip aquifer with two Dirichlet boundaries |
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Strip aquifer with two Neumann boundaries |
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Strip aquifer with one Neumann boundary and one Dirichlet boundary |
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Square aquifer with Dirichlet boundaries |
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Square aquifer with Neumann boundaries |
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Square aquifer with Dirichlet and Neumann boundaries |
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Aquifer with radial boundary (Dirichlet) |
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Aquifer with radial boundary (Neumann) |
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Analytical solutions for calculations of pit inflow (Q) and pit drawdown (so) for leaky aquifers
The pit inflow is calculated using the formula for unlimited aquifer and drawdown formulas for each type of boundary
Boundaries |
Leaky aquifer formula |
Unlimited aquifer |
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One boundary of the I-st type (Dirichlet) |
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One boundary of the II-nd type (Neumann) |
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Strip aquifer with two Dirichlet boundaries |
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Strip aquifer with two Neumann boundaries |
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Strip aquifer with one Neumann boundary and one Dirichlet boundary |
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Square aquifer with Dirichlet boundaries |
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Square aquifer with Neumann boundaries |
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Square aquifer with Dirichlet boundaries |
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Aquifer with radial boundary (Dirichlet) |
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Aquifer with radial boundary (Neumann) |