We will often have a client in the middle of a dilemma choosing which option to use to retain an embankment. Both offer excellent low, cost solutions as retaining structures. Both use the same design principals which incorporate mass and tension geotextiles behind the face. It is important that both are designed by a competent person with geotechnical and design qualifications.
Because they can do the same job equally well, the decision generally comes down to cost and aesthetics. Gabion baskets have existed, in one form or another, for hundreds, if not thousands, of years. They have been adapted more recently to be used as barriers to erosion in rivers, shorelines and breakwater situations. Their massive weight can withstand heavy turbulence and wave action. In these scenarios, they are generally more effective than concrete retaining block (CRB) walls.
Concrete Retaining Blocks are a fairly new concept from the late 20th Century. The early walls were usually gravity walls in which local soil was used to fill a hollow in the block so it would contribute the weight. This would significantly reduce costs in both materials and transport. Later walls incorporated a new breed of high tensile geotextiles which could incorporate the weight of soil behind the wall. This extra weight contributes to resistance against sliding, buckling and overturning.
Factors influencing Cost:
Cost comparison of the walls depends on the specific site location and conditions. Concrete blocks tend to be lower in cost in urban areas where concrete manufacturers are nearby and quarried rock is far. The exception to this rule is obviously in cases where the site is rocky and there is a need for on-site rock breaking. In these instances, there are substantial savings from not having to cart away broken rock and an aesthetic advantage in maintaining the natural visual environment. To improve the visual effect, the front face can be filled with high-quality expensive rock for visual effect. The hidden sections can then be filled with less expensive, but equally weighty materials. To find the most cost-effective solution, ask your specialist to price both options with price in mind and they may come up with an innovative solution which really works for you. If a low price is of primary importance, make this clear, but make sure your contractor is a specialist in retaining walls – Cutting costs by reducing important structural component will result in costly reconstruction and is extremely dangerous.
Aesthetically, concrete retaining blocks come in many shapes and styles. Most can be planted which can give a green landscape that can become a visual centrepiece of a small garden. Equally, gabion baskets can be filled with many rocks types and colours as well as pebbles and other building materials which can lift the colour and style of the visual environment.