Since my article on Retaining Walls, I received queries regarding the components of a modular block retaining wall. So I deceided to write this post to supplemnt my earlier article.
A modular block (or segmental) retaining wall consists of the following components:
- Modular blocks (Facing Unit)
- Levelling pad
- Drainage Material
- Engineered Fill
- Geosynthetic Reinforcement
- Impervious Fill
- Retained Backfill
Modular blocks are the facing units – the aesthetic component of the wall that meets the eye. There are several companies like VERSA-LOK, KEYSTONE, ALLAN BLOCK, MESA BLOCK , etc that sell these inter-locking units.
Levelling Pad refers to the base of the “founding” element of the retaining wall. It provides a level base for the retaining blocks.
Drainage material is placed immediately behind the facing units to ensure that any moisture or groundwater is drained away and doesn’t exert excess pressure on the facing units.
Engineered Fill refers to the soil that replaces the material excavated from the natural slope. Typically a silty sand is used as engineered fill.
Geosynthetic Reinforcement are the sheets or grids of geosynthetic reinforcement that are used to strengthen the system. Tensar and Mirafi are two of the popular companies that manufacture geosynthetic reinforcement sheets and grids in the US, while Techfab India provides these materials in India,
Impervious fill is used to cap the backfill behind the facing units so that rain water or other surficial water doesn’t permeate into it.
Retained backfill is the part of the natural slope or natural terrain that is still undisturbed.
Geogrid Retaining Wall Systems, Incorported has an excellent series of photographs showing the step-by-step construction of a segmental retaining wall.
Copyright Kshitija Nadgouda.