Hardscapes - Retaining Wall Systems
Types of Retaining Wall Systems
Two of the most commonly used retailing wall systems are Mechanically Stabilized Earth (MSE) and Segmental Retailing Wall system (SRW).
Mechanically Stabilized Earth
Mechanically Stabilized Earth (MSE) also known as Reinforced Soil Retaining Wall is a gravity retaining wall designed to withstand lateral earth and water pressures. The wall is built from individual panel sections. Panels are interlocked and supported by steel straps that are mechanically attached to the back of the panel and extends back from the panel into the retained soil, resulting in a reinforced soil zone behind the wall. Instead of regarding soil as a mass to be contained by force, the earth itself is reinforced to become an integral part of the structure. The wall behaves as a gravity structure in an integral unit and provides structural flexibility. Welded wire mats placed within layers of compacted backfill provide the necessary tensile strength. Segmental Retaining Wall
Segmental Retaining Wall (SRW) is a dry-stacked wall made of low-absorption, high-strength concrete units. It requires no heavy equipment, mortar or form work, less excavation and can actually be constructed by hand. The rugged, rock-solid durability enables the wall to outlast railroad ties and timbers while remaining environmentally safe. The segmental nature affords the wall a permeability to relieve hydrostatic pressure, so less material is required for resistance. This system provides design flexibility such as curved walls and it can be overlaid onto existing older retaining walls. The system not only retains soil and supports loads but also provide aesthetic treatments thus making it an attractive and structurally sound wall system. Choosing the Correct Retaining Wall System
Retaining walls stabilize soil and/or rock from down slope movement or erosion and provides support for vertical or near-vertical grade changes. As such, it is very important that a correct retaining wall system is used to ensure a successful long term wall performance. A retaining wall system needs to be versatile and flexible in order to accommodate the unique needs of the particular project site. Location geometry most often dictates the selection of a retaining wall system. It is very important to choose the system that is most appropriate to the location or the project site. The locations’ field condition must be carefully observed and analyzed. Things to consider are soil that are soft or wet, areas that are producing groundwater, and areas that exhibit slope failures during excavation. Each of these factors indicates potential stability problems that have to be considered in choosing the most appropriate retaining wall system.
Protecting the Retaining Wall System
Proper drainage behind the wall is critical to the performance of retaining walls. Drainage materials will reduce or eliminate the hydraulic pressure and increase the stability of the fill material behind the wall; therefore, providing proper drainage is a must.
If the retaining wall system is used in home construction, it is even more important to protect it against moisture. Hydrostatic headwater pressure will force moisture in soil into the home. If there is a crack in the retaining wall, then moisture will easily see through. This can cause not only visual problems, like green slime efflorescence, mineral deposits and rust, but also health problems such as mold, mildew and asthma. Periodically inspect walls for evidence of backfill loss, loss of joint seals, or movement, especially after heavy rainfalls. Rain can soften or loosen the compacted backfill, and any rain that seeps into the backfill can increase pressures on the wall panels. Reseal joints, particularly those that may allow surface water to enter the wall backfill.
