Temporary retaining walls are often used during construction, such as for the support of the sides of an excavation that is made below-grade in order to construct the building foundation. If the temporary retaining wall has the ability to develop the active wedge, then the basic active earth pressure principles described in the previous sections can be used for the design of the temporary retaining walls.
Especially in urban areas, movement of the temporary retaining wall may have to be restricted to prevent damage to adjacent property. If movement of there taining wall is restricted, the earth pressures will typically be between the active (kA) and at-rest (k0) values.
For some projects, the temporary retaining wall may be constructed of sheeting (such as sheet piles) that are supported byhorizontalbraces, also known asstruts. Near or at the top of the temporary retaining wall, the struts restrict movement of the retaining wall and prevent the development of the active wedge. Because of this inability of the retaining wall to deform at the top, earth pressures near the top of the wall are in excess of the active (kA) pressures. At the bottom of the wall, the soil is usually able to deform into the excavation, which results in a reduction in earth pressure, and the earth pressures at the bottom of the excavation tend to be
constant or even decrease.
The earth pressure distributions shown in above Fig. were developed from actual measurements of the forces in struts during the construction of braced excavations. case a shows the earth pressure distribution for braced excavations in sand and cases b and c show the earth pressure distribution for clays.
the distanceH represents the depth of the excavation (i.e., the height of the exposed wall surface). The earth pressure distribution is applied over the exposed height (H) of the wall surface with the earth pressures transferred from the wall sheeting to the struts (the struts are labeled with the forcesF1,F2, etc.).