Plane Water Pressure
To include Water Pressure in the analysis, select the Water Pressure check box in the Input Data dialog. The following Pressure Distribution options will be available:
- Peak Pressure – Mid Height
- Peak Pressure – Toe
- Peak Pressure – Tension Crack Base
- Custom Pressure
These distributions are illustrated below, for models with and without a tension crack.
Peak Pressure Mid Height
The Peak Pressure Mid Height option assumes that the maximum water pressure occurs at the mid height of the water level in the slope. The pressure is assumed to be zero at the toe of the slope, with linear pressure variation between zero and the maximum pressure.
B 
Peak Pressure Mid Height water pressure option, without tension crack (A) and with tension crack (B).
Peak Pressure Toe
The Peak Pressure Toe option assumes that the maximum water pressure occurs at the toe of the wedge. This is the worst case scenario, since it will result in the maximum hydrostatic force being applied to the wedge. This may occur if drainage at the toe of the slope becomes blocked, for example by freezing of water. The pressure variation is linear from the maximum at the toe, to zero at the top of the water level in the slope.
B 
Peak Pressure Toe water pressure option, without tension crack (A) and with tension crack (B).
Peak Pressure Tension Crack Base
The Peak Pressure Tension Crack Base option assumes that the maximum water pressure occurs at the base of the tension crack. This model is only applicable if your model includes a tension crack. The pressure is assumed to be zero at the toe of the slope, with linear pressure variation between zero and the maximum pressure, on both the failure plane and the tension crack.
NOTE: with this model, you may choose to turn OFF the water pressure on the failure plane, by selecting the "No Failure Plane Pressure" check box. In this case, water pressure will only be applied on the tension crack. This can be used to model the case where the failure plane is impermeable.
B 
Peak Pressure Tension Crack Base option. Pressure on both tension crack and failure plane (A) and pressure on tension crack only (B).
Custom Pressure
The Custom Pressure water pressure option, allows the user to specify the actual (average) water pressure on the failure plane and the tension crack. This is useful if actual water pressure data is available. Remember that these values represent the AVERAGE water pressure on the wedge planes, and that only a single value can be entered for the failure plane, and a single value for the tension crack.
B 
Custom Pressure water pressure option, without tension crack (A) and with tension crack (B).
NOTE: For the Custom Pressure option, the Unit Weight and Percent Filled options are not applicable, since the actual (average) pressure is being entered.
Unit Weight
The Unit Weight option for water pressure allows the user to specify the unit weight of water. The Unit Weight of water is used to calculate the value of Peak Pressure for the following water pressure distribution options:
- Peak Pressure Mid Height
- Peak Pressure Toe
- Peak Pressure Tension Crack Base
The Unit Weight option is not applicable for the Custom Pressure option, since the water pressure is entered directly by the user for this option.
Percent Filled
The Percent Filled option allows the user to specify the water level in the slope. Note:
- For the Peak Pressure Mid Height and Peak Pressure Toe options, the Percent Filled is relative to the total height of the wedge (see figures A and B)
- For the Peak Pressure Tension Crack Base option, the Percent Filled TC represents the level of water in the tension crack (see figure C)
- Percent Filled is not applicable for the Custom Pressure option.
B 
C 
Percent Filled = 50% for Peak Pressure Mid Height (A), Peak Pressure Toe (B) and Peak Pressure TC Base (C).