Method of Soil Backfill of Trenches

This method statement describes a proper work procedure shall be carried out during the backfill Work of soil. Earthwork forms a part of the installation procedures of box culverts, retaining walls, foundations, and substructures.

In order to ensure an adequate foundation for such structures, backfill material must meet certain specifications and be compacted by acceptable methods to adequate density.

The use of poor soils as a bed for a structure and the failure to adequately compact soils surrounding any foundation can lead to premature failure.

Backfill shall be of acceptable quality, free from large or frozen lumps, wood or other foreign material. No backfill shall be placed against a concrete abutment, wing wall or reinforced concrete box culvert until concrete has been in place at least 14 calendar days. 

Materials: Natural soil

Tools & Equipment :

• Excavator /JCB
• Roller

Backfill Procedure

• All the area to be backfilled with the soil will be properly cleaned from debris.
• Back filling shall commence using similar excavated material. Care shall be taken to remove bolder, vegetation’s and any other deleterious materials.
• Prior to back filling, the compacted surface shall be accepted by the consulting engineer.
• The thickness of the back fill shall not be greater than 300mm.
• The sub-grade once approved, the excavated materials or any material source approved by the engineer shall be placed in layers not more than 300 mm thick followed by compaction test when surface level is ready.
• In-situ dry density test (compaction test) shall be performed at the rate indicated in the specification.
• Back filling followed with compaction shall continue till final level is achieved.
• The filling shall be compacted by mechanical means using plate compactor or roller depending upon the surface available for the suitable equipment.
• All filled areas shall be left neat smooth and well compacted the top surface consisting of the normal site surface soil.

Backfill Tests

Field density test shall be performed on the final compacted layer of soil. All the field density tests shall be performed in the presence of Engineer or representative.

Above Procedure will be followed as per consultant/client approval.