Hydrodynamic Pressure
| Hydrodynamic pressure |
The heel of a structure is sunk into permeable subsoil, which allows free water flow below the structure - see figure. The unit weight of soil lifted by uplift pressure γsu is modified to account for flow pressure. These modifications then depend on the direction of water flow.
Action of hydrodynamic pressure
When computing the earth pressure in the area of descending flow the program introduces the following value of the unit weight of soil:
and in the area of ascending flow the following value:
where: | γsu | - | unit weight of submerged soil |
Δγ | - | alteration of unit weight of soil | |
i | - | an average seepage gradient | |
γw | - | unit weight of water |
An average hydraulic slope is given:
where: | i | - | an average seepage gradient |
hw | - | water tables difference | |
dd | - | seepage path downwards | |
du | - | seepage path upwards |
If the change of unit weight of soil Δγ provided by:
where: | i | - | an average seepage gradient |
γw | - | unit weight of water |
Is greater than the unit weight of saturated soil γsu, then the leaching appears in front of structure - as a consequence of water flow the soil behaves as weightless and thus cannot transmit any load. The program then prompts a warning message and further assumes the value of γ = 0.