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The information below serves as a guideline: Please contact RECO for a comprehensive Technical Specification.
Placing and compaction of the select backfill
The select backfill is placed and compacted in layers. Steel tracked equipment should not come into direct contact with the reinforcing strips. Heavy equipment should not come within 1.5 metres of the wall face. Compact close to the wall with hand operated vibrating plates or rollers.
The degree of compaction required is stated in the project specification, but in any case should not be less than 95 percent of the maximum dry density (Standard Compaction).
The backfill should never be placed with a moisture content higher than Optimum Moisture Content.
Choice of select backfill
A Reinforced Earth wall requires a select, non-plastic, granular backfill material for dry land structures (see table below).
Physical characteristics
The grading curve for select backfill must be within the limits of the non-shaded zones shown in the diagrams below.
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Backfill Chart for Select Backfill for TerraClass®, TerraPlus®, TerraMet® and TerraTrel®
Backfill Chart for Select Backfill for TerraTilt®
Chemical and electrochemical properties
The pH value, as determined by the Australian Standards, should lie between 5 and 10 for galvanised steel reinforcements. For polyester reinforcements pH shall be between 4 and 9.
For galvanised steel reinforcements the electrical resistivity, as determined by the Australian Standards, should be greater than 50-ohm metres. If the resistivity is between 10 and 50 ohm metres then the material is acceptable only if:
- the chloride (CI-) content is less than 200mg per kg (0.02 percent); and
- the sulphate (SO) content is less than 1000mg per kg (0.10 percent).
Details of the selection criteria can be obtained from RECO.
Earth backfill, which does not meet the standard criteria, may be acceptable subject to design review and additional testing. All backfill, which is proposed for use in Reinforced Earth structures should be tested to confirm that the criteria specified is satisfied and test results should be sent to RECO for approval.
NOTE: The chemical and electrochemical properties stated describe the standard requirements of RECO for the Reinforced Earth structure using steel soil reinforcement. In the event of any conflict with the Head Contract Specification, the Head Contract Specification shall govern provided that the minimum requirements of RECO are met. Backfill requirements using synthetic soil reinforcement may differ.