Backfilling is simply the process of refilling or replacing the soil that was removed during the construction works. It is highly essential as they offer strength and support to the entire structure as a foundation. There are different backfilling materials and methods utilized according to the requirements.
Some of the trench backfilling materials include:
- Coarse-grained soils such as sandy soils, clayey sands, gravel-sand mixtures etc.
- Fine graded soils of low to medium plasticity
- Commercial by-products such as furnace slag or fly ash
- CLSM cementitious material
Now we could look at the main techniques of backfilling trenches used by construction industries:
- Water Jetting Method: This backfilling method makes use of a long rod metal device that is connected to an efficient pressurized water supply, so that the ground soil flows and fills the trench. As the water dissipation decreases the trench volume, this method is highly recommended while dealing with granular soil types, whereas it is not ideal for clay grounds.
- Filling Method: Here a fragile concrete mix with a low water/cement ratio is being used to fill the trenches. This cementitious material is directly dropped from the concrete mixer truck straight into the trenches, simplifying the process and manual workload.
- Mechanical Compaction Method: It is actually the process of densifying the loose, unconsolidated soil materials deep into the ground by repeated passing of mechanical equipment. Since there are various compaction techniques, a clear idea of the soil type is absolutely necessary before applying them on soil grounds.
- Deep Dynamic Compaction: The underlying soils are compacted with heavy weights dropped from heights using crane or some other lifting device.
- Vibro Compaction: Performed by inserting a vibrating probe or vibrating plate into the ground to loosen the native materials. This vibration method is often used in the rolling compaction.
- Roller Compaction: A heavy cylinder-like mechanics is rolled over the ground, along with vibrating devices to enhance their effectiveness and soil strength.
The best geotechnical engineers of the civil construction companies in Saudi Arabia have abundant subject matter expertise and they accurately know which is the most suited backfilling method according to the existing subsurface conditions.