RETAINING WALL DESIGN PROCESS

Knowing the unique features and benefits of Keystone's products and understanding the effects of earth pressure and soil mechanics are the first steps toward properly designing an earth retaining wall system. To complete the design process, one also needs to understand the effects of soil design properties, surcharge loads, structure site geometry (i.e. terraced walls, toe slopes, water conditions, etc.) - as well as the engineering properties of the Keystone system components.

SOIL PROPERTIES

The very purpose of a retaining wall system is to safely hold soil in place to make a grade or elevation change in the shortest possible distance. The soil's shear strength (angle of internal friction [Ø] and cohesion [c]) and moist soil weight () determines the design characteristics of the soil for use within the wall structure. The design properties of the reinforced zone, the soil above and behind the wall structure, and of the foundation material under the structure, must be determined. A qualified geotechnical engineer should be consulted to establish site specific soil properties. Tall walls or difficult site conditions will typically require a more extensive geotechnical investigation including laboratory testing of soil.

Remember: the better the soil (more granular - higher friction angle and better drainage capability), the more efficient and cost effective the wall design and soil reinforcment solution will become. Better quality soils are more easily placed and compacted resulting in superior structure performance.

SURCHARGES

A surcharge is a load imposed on the soil directly behind the wall which exerts an additional loading on the structure. Examples of surcharges include sloping hillsides above retaining walls, roadways, parking lots, truck loading areas, buildings, foundations or rail lines. Seismic and hydrostatic (water) loads also need to be factored as transient surcharge conditions where applicable.

Typical live load surcharge loadings are: