UBC Undergraduate Research

Retaining walls : an overview of the characteristics and design of gravity, Mechanically Stabilized Earth (MSE) and Geosynthetic Reinforced Soil (GRS) retaining walls White, Michael


[Partial Introduction - see PDF file for the rest] The objective of this essay is to provide a general overview of three types of retaining walls through review of current literature. The scope of this essay encompasses basic retaining wall theory and design. There are three common types of retaining walls that will be discussed in this essay. The first type is gravity retaining walls. This is a general term for walls that use the self-weight of the wall to support the soil behind the wall, called backfill which may be undistirubed natural soil or disturbed soil that is placed and compacted behind the wall. Gravity walls are a classic example of the externally stabilized wall system. The walls are constructed using heavy materials that must be sufficient to resist the vertical and lateral stresses imposed on the wall from the soil mass (Criag, 1992). Mechanically Stabilized Earth (MSE) walls are the second type of retaining walls to be discussed. MSE walls consist of a rigid face tied-back with reinforcements to elements embedded behind the wall with the purpose of “mechanically” stabilizing the soil mass (VanBuskirk, 2010). The horizontal reinforcements are spaced and connected to the rigid face throughout the height of the wall, with the primary design considerations being vertical distance between layers of reinforcement, strength of the reinforcements themselves, and connection strength between the reinforcements and the rigid face (Elias et al, 2001). Triaxial test results show that the addition of reinforcement results in increased peak strength, larger axial strain at failure, and reduced or limited post-peak loss of strength (Elton and Patawaran, 2005).Although MSE walls use reinforcements within the soil mass, MSE walls are technically classified as externally stabilized walls because the explicit purpose of the reinforcements is to prevent deformation of the wall face and current design standards ignore the soil-reinforcement interaction (Wu, 2001). The third type of retaining wall is a relatively new technology called Geosynethic Reinforced Soil (GRS); GRS walls are an example of internally stabilized walls and are different than MSE walls. The concept of reinforced soil is not new; evidence of reinforcing soil for stability can traced back as early as the construction of the Great Wall of China (Bradley and VanBuskirk, 2009). Although the theory of reinforcing soil remains the same, GRS uses new technology that provides improvements over other reinforced soil walls such as MSE walls. GRS walls are constructed using well-compacted soil between closely spaced reinforcement layers (VanBuskirk, 2010). The close spacing between reinforcement layers allows the face of GRS walls to be flexible, non-rigid and non-load bearing (Wu, 2007). This essay will display the similarities and differences of gravity, MSE and GRS walls.

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