Design Alternatives
retaining block wall design options
Terraforce retaining blocks can be used either as part of a gravity system or as the fascia of a geosynthetic reinforced segmental retaining wall structure, or as a fascia for a cement stabilized backfill.
Download the Recommended specifications on the downloads page.
1. Gravity retaining walls
Gravity retaining walls rely on their self-weight to resist lateral earth pressure, and such walls have been in use for centuries. In a gravity system the Terraforce masonry units can be stacked several courses deep to provide support to the forces imposed by the retained soil; the weight and geometry of the stacked units prevent the constructed wall from sliding on its base or at an intermediate height, toppling over, or rotating out of position.
What are gravity retaining walls?
There are various types of these systems on the market with elevations ranging from open checkerboard appearance to closed vertical surface structure and many are plant supportive to varying degrees. Some systems are interlinked, while others interlock on the vertical and/or horizontal plane. All systems rely mostly on interblock friction to derive a measure of sliding resistance and under ideal conditions that is sufficient to prevent collapse when constructing a gravity retaining wall.
Yet, when substantial active lateral earth pressure occurs, considering the slender cross-section of these walls clearly no amount of interlocking or interlinking will prevent such a structure from collapsing. The most economical solution under such conditions is often found in constructing a multi-skin gravity retaining wall. Such a wall relies upon weight and frictional resistance to obtain stability. Alternatively, earth reinforcing or cement stabilised backfill techniques may be employed.
Design Tables for single skin gravity walls:
Information relating to the design of single-block-width gravity retaining walls will be given in these design charts for Terraforce blocks. Designs which feature multiple rows of blocks should be prepared on a site specific basis by an experienced professional engineer.
Click in the boxes below for the Design Tables of the different Terraforce blocks (in various sizes):
2. Geosynthetic reinforced soil segmental retaining walls
By virtue of their inherent flexibility, such walls are able to accommodate movement and some settlement without suffering distress. This makes the system particularly suitable for construction on (engineered) filled ground or in areas which may be prone to settlement effects. Also, the cost and difficulty of construction of such retaining walls is minimized as the need to provide full frost wall foundations can be waived in many circumstances.
The publication “Terraforce-design and installation manual for Geosynthetic Reinforced Soil Applications” by Colin Alston and Dr Richard Bathurst contains 24 design charts that cover a wide variety of situations. Request a copy from your nearest supplier
What are Geosynthetic reinforced soil segmental retaining walls?
Geosynthetic reinforced soil segmental retaining walls utilize reinforcing sheets of geogrid or suitable woven geotextile which are attached to the fascia and are embedded in a body of engineered fill.
The integrated nature of the fascia and the abutting large body of reinforced soil thereby supports the applied earth forces. In this case the “gravity” component of the retaining wall is provided by the reinforced soil mass, which acts as a monolithic unit.
3. Reinforced concrete-filled segmental retaining walls
Occasionally severe space limitations dictate the use of a double skin of Terraforce blocks in combination with reinforced concrete infill or stabilised backfill. This type of installation, while similar in nature to conventional reinforced concrete/masonry retaining walls, offers a number of added advantages:
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Ease and speed of construction – no shuttering and less specialised construction skills required.
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Aesthetic appeal – choose between split face blocks or smooth moulded appearance. It is even possible to retain a degree of plantibility in some cases.
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