When a SRW is exposed to additional loads, whether permanent or temporary, the overall wall design is affected. Usually, when a structure, building, roadway or top slope is within twice the height of the SRW wall face, its impact on the stability of the wall must be evaluated. This is only a general rule based on the most common soil types. Wall design engineers must consider many other factors which may adjust this proximity formula.
Surcharges may stabilize or destabilize a ReCon wall, depending on their type and / or relative proximity to the wall.
By definition, surcharges are usually classified as a “live load” or “dead load”. A live load is generally temporary in nature. An example might be a fully loaded semi truck traveling along a roadway within close proximity to the finished SRW. Because it is by definition temporary, any stabilizing contribution of a live-load surcharge is usually ignored. Ultimately, this results in a more conservative design with an improvement in the overall safety factors for certain aspects of the wall design.
A dead load, by contrast, is intended to be permanent. Although it will increase stresses on the wall depending on its type and proximity to the wall, it can also contribute to certain aspects of wall stability. Examples of a dead load could be a slope above the wall that adds the extra weight of the soil mass and must be accounted for in the wall design; or it may be a building exerting additional weight through its foundation or footing. Another common type of dead load found on SRW sites results from wall terracing. When a second (or third, etc.) SRW is built above another it needs to be evaluated to see if it is imposing additional stresses on the wall (or walls) beneath it.