RETAINING WALL TYPE

Gabion basket case study (3m high)

A gabion basket retaining wall was required for a 40m length 3m high shown in yellow of the drawing below.

 

Construction Sequence

The existing ground will be excavated to the proposed finished level with a stable temporary slope. The gabion baskets can then be installed as designed and the backfill installed.

Proposed Retaining Wall System

The gabion retaining wall consists of steel mesh baskets filled with large size stone. The stone must be large enough to prevent movement and prevent any stone from passing through the gaps in the steel mesh. The retaining wall is a gravity-type wall which resists the sliding and overturning forces from the retained material through the weight of the stone in the baskets.

To learn more about gabion basket retaining walls click here.

Design parameters

The following information provided by the client has been used to determine the correct design parameters;

The underlying soil is assumed to be a firm, sandy silt as described by the client. If this is found to be inaccurate during construction the design will need to be adjusted or the baskets taken down to a deeper level.

All other parameters have been taken as reasonably conservative values based on a typical firm sandy silt soil.

Surcharges of 5.0kN/m2 have been allowed for on the higher level ground. This assumes that the area is to be used only as a garden with no possible vehicular access as advised by the client.

Gabion basket retaining wall

Budget pricing

Supply and deliver of the gabion baskets 4mm gauge wire 1m x 1m x 2m £105 each. 1m x 1mx 1m £65 each

Make up the baskets £25 each

Excavate and concrete the foundation £40 per m

Stone fill the basket by machine £75 m3

Back fill the wall with stone £55 m3

Supply and lay land drain £8 m

The approximate rate for the wall designed 40m long x 3m high x 1m wide using the rates above £225 m2 for self build. Add 25% to cover risk, overheads and profit for the wall to be built by a specialist contractor.

Exclusions

The prices above do not include any excavation to form the retaining wall and no stone filling behind the retaining wall. The rate only includes the supply and construction of the retaining wall.

Note

Every project is different regarding soil type, scale, site access and location. Every project needs to be priced from the structural engineer’s calculations, specifications, and drawings. Budgets are July 2022 prices.

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