Active soil pressures are generally used for soil load calculations. Active pressures are applied loads induced by the soil onto the contained environment. Passive pressures are forces induced by the soil’s resistance to applied loads. Passive pressures are generally not conservative for calculations. This is because there will be a worst case scenarios if the soil mass is removed or when an empty space develops between the wall and the soil due to hydration. There will be no passive resistance due to lack of forces induced by soil resistance and there will only be passive resistance until the wall moves towards and is in direct contact with the soil for the soil to resist the wall mass. Constants used to determine soil pressures include the angle of repose and soil/wall friction.

Soil load calculations are often calculated for soil pressure induced onto retaining walls and basement walls. Here are some typical loads used:

Uniform surchage load = 10 kPa

Soil load = 20 kPa using dead load factors

Hydrostatic water pressure should also be designed for, assuming it acts onto ⅓ height of the wall. However, full hydrostatic head will be used for soils with high water table.

Propped retaining wall     Ko = 0.7

Overconsolidated clays   Ko = 1.5

Overconsolidated sands  Ko = 1.0

​​Other pressures

Pressures that need to be considered when constructing retaining walls, basement walls or any other substructures include the following.

1.    Earth pressure

2.    Water pressure (accounting for extreme flood conditions, buoyancy where groundwater is taken the full basement depth)

3.    Surcharge from adjacent structures

Fluid Loads

Fluid loads should be calculated by using the static pressure of liquid and its effect on its containment (pressure = density x height of fluid in the contained environment).

Common uses include water tanks and basement walls.

Vehicle Loads

Vehicle loads should be incorporated into the structure’s design, when the structure consist of parking lots, ramps, highways, loading bays at industrial buildings, bridges, and any other structure that has vehicles moving on it. Not only do self-weight of the vehicles should be included in the design, vehicle impact loads should be included, as well as, the design of kerbs and rails and other protective and preventative measures for vehicle impact.

Normally, 2.5 kPa should be used for uniformly distributed loads for a car parking area and 5 kpa  should be used for uniformly distributed loads for a commercial vehicle area.