Calculations for
open pits inflow are based on published analytical solutions
for
the following hydrogeological conceptual schemes:
·Confined
aquifer;
·Unconfined
aquifer;
·Confinedunconfined
aquifer; and
·Leaky
aquifer
Most schemes
account for Ist or IInd types of boundary
impacts. The aquifer
can be modelled as infinite, bounded, stripped or radial
(circlebounded).
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, if pit inflow is entered. When entering values in text
box "Q,
m^3/d" and
"t,
d"), you can
convert inflow rate and time in other units using
SHIFT (or CTRL)
+ MB.
To access this
module, use "Model
> Quick estimates> Pit inflow" or button
"Quick
estimates of pit inflow" in tab
"InPit
sumps" of dialog
window "Pit"
(use button "Pit"
on a dialog window AMWELLS).
a
b
c
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 confinedunconfined 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
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 1st boundary (for aquifers with two
boundaries)

"L"
text box

Width of strip
aquifer

"L2,
m" text
box

Distance from
the pit center to the 2nd aquifer boundary (for aquifers with two
boundaries) or to the center of the aquifer (for aquifer with
radial boundary)

"Conceptual
scheme" list

Conceptual
scheme of the aquifer (i.e. confined, unconfined,
confinedunconfined 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 nonelongated 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

Select 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
calculated using hydrraulic conductivity (text box
"a")
and time
(text box "t").
Use
this parameter for infinite aquifers and also for aquifers with
boundaries that can not be modelled in steady state

Analytical solutions for calculations of pit inflow
(Q)
and pit drawdown (so)
for confined, unconfined and confinedunconfined aquifers
Boundaries

Confined
aquifer

Unconfined
aquifer

Confinedunconfined
aquifer

Unlimited
aquifer (radius of influence is required)




Radius of
influence can be estimated outside of the module and entered
manually. Other option is to use inbuilt formulas of the dialogue
window:
1) general
formula for transient groundwater flow:
2) general
formula with recharge:

Unlimited
aquifer(drawdown in observation well is required )




One boundary of
the Ist type (Dirichlet)


One boundary of
the IInd type (Neumann)


Strip aquifer
with two Dirichlet boundaries


Strip aquifer
with two Neumann boundaries


Strip aquifer
with one Neumann boundary and one Dirichlet boundary


Square aquifer
with Dirichlet boundaries


Square aquifer
with Neumann boundaries


Square aquifer
with Dirichlet and Neumann boundaries


Aquifer with
radial boundary (Dirichlet)


Aquifer with
radial boundary (Neumann)





Analytical solutions for calculations of pit inflow
(Q)
and pit drawdown (so)
for leaky aquifers
Pit inflow is
calculated using formula for unlimited aquifer and drawdown
formulas for each type of boundary
Boundaries

Leaky aquifer
formula

Unlimited
aquifer


One boundary of
the Ist type (Dirichlet)


One boundary of
the IInd type (Neumann)


Strip aquifer
with two Dirichlet boundaries


Strip aquifer
with two Neumann boundaries


Strip aquifer
with one Neumann boundary and one Dirichlet boundary


Square aquifer
with Dirichlet boundaries


Square aquifer
with Neumann boundaries


Square aquifer
with Dirichlet boundaries


Aquifer with
radial boundary (Dirichlet)


Aquifer with
radial boundary (Neumann)


