Trenches and Other Excavations Backfilling

Backfilling is the process of returning dirt to a trench or foundation after it has been excavated and the associated work has been done. Backfilling demands expertise, heavy equipment, and a thorough understanding of the specifications, contract requirements, and soil conditions. Each type of soil has its own properties, necessitating the use of diverse construction approaches to achieve the best results.

When pouring and compacting backfill, backfill personnel must also take care to avoid impact loading any pipeline, shaft, structure, cabling, or other subterranean elements. Backfilling and compacting backfill can be done in a variety of ways. Special precautions must be taken while filling and compacting ditches for utility lines.

Trenching Compacting

Following the backfilling of earth into a trench, the loose material is crushed using a compactor, an excavator, or a “jumping jack”-type compactor. As a general rule, soils should be compacted to at least the ASTM D698 Method A minimum percentages of maximum dry density (Standard Proctor). 1

Backfilling soil is usually done in layers or lifts. The soil lift will be determined by the type of backfill utilized and the compaction equipment used. To aid compaction, water can be introduced at any time during the operation. The main procedure is broken down into three parts, which are repeated until the backfill reaches grade level:

• Backfill with non-organic fill material that is free of debris in 4 to 6-inch layers.
• Compact using a 1,000-pound compactor, or as needed.
• Thoroughly wet
• Using Water Jets

Backfilling with water jetting eliminates the need for mechanical compaction. Instead, a probe is used to apply pressured water to the bottom of the backfill, compacting it. Water jetting is excellent for sand or sandy soils, as well as the bedrock that is extensively fissured. Plastic soils and thick clay soils are not suited.

You utilize the jetting technique to shift bedding or backfill material around by pumping water under pressure and using the force of the jetted water. The material should be deposited gently and in lifts, just like any other backfilling. To improve compaction, the water is allowed to drain from the soil after it has been poured. Crews must take precautions to confine sediment-filled water and prevent it from entering drains and watercourses due to the mixing of water and soil, all in compliance with EPA guidelines. 2

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