Foundation System Retaining walls can be provided with a variety of different foundation support systems depending upon the soil conditions and local topography. The geologist and soils engineer must evaluate site conditions and provide the structural engineer with a recommendation of the foundation system to use and the bearing material which is to provide support for the foundation system.

Conventional Foundations - The most common form of support of retaining walls is conventional footings.  The geologist and soils engineer must determine the foundation bearing material and the minimum depth of embedment.  The structural engineer will determine the actual depth of embedment and the width of the footing needed to support the wall.  A keyway is also sometimes employed in a conventional retaining wall foundation.

Deepened Foundations - Deepened foundations, consisting of either friction piles or caissons are commonly used to support hillside retaining walls.  Deepened foundations are necessary when retaining walls are located over or near descending slopes or when necessary to penetrate deep unsuitable earth materials.  Deepened foundations are also sometimes used to avoid surcharging lower walls or structures.

Tie Back Anchors  - Tie back anchors are sometimes employed to resist lateral forces imposed on retaining walls.  Tie back anchors are drilled at an angle into the slope and spaced at pre-determined intervals. Tie back anchors are commonly used in construction of temporary shoring for high excavations.  The Los Angeles Department of Building and Safety does not allow the use of tie back anchors in the permanent design and construction of retaining walls.