What is the purpose of backfilling?

Are you done with the excavation process in your particular construction project? Whether you are having a foundation built or having concrete work done on your property, backfilling may be something you do not know you need to do after the digging work is complete. But what does backfilling really mean and is it really essential to your project?

Backfilling is an important part of many construction projects. Although it is more common during trenching and the construction of foundations, it is the process of replacing the soil that has been removed during the excavation stage of the project. It mainly serves to strengthen the foundation work and increase its integrity for a much better result.

Why is backfilling important?

For many situations, backfilling is an essential step that should not be missed. This is because it can be extremely helpful for the success of the project and its overall condition in the future.

Of course, if we put it this way, backfilling is just technically the process of putting soil back into a cavity or excavated hole. How can doing it be productive and worth the spent resources?

The three main benefits of backfilling

1)    It enhances the strength of the foundation

To build a nice and solid structure, backfilling is certainly a procedure that can help with the strengthening of the foundation. Since it is important to establish a good and strong base that will keep the overall strength of the building, replacing the excavated soil around the property is one of the things that will keep the entire structure standing as the years pass.

2)    It lends support to a certain foundation or structure

Aside from making the foundation or structure stronger, the proper placement of excavated earth back to the cavity can lend support as it allows the correct layout of the latter. Just think of it this way: if the structure is rigid because it is securely placed, then it will not move around during a strong storm or earthquake.

3)    It increases the stability of the foundation or structure

Once a certain construction project is properly backfilled, it is also proven to be more stable and perform better compared to others who did not make use of earth compaction techniques. According to many experts, structures that have not been backfilled are prone to collapse or destabilize a lot faster than the normal rate.

When should you backfill?

Just like with other construction processes, it is important to follow the proper guides and timelines to ensure that the structure will be more stable after its completion. This also applies to the process of putting soil back into the excavated area in the property. When is the recommended time or stage where backfilling should be done?

Since the method requires the presence of a cavity, gap, or an excavated hole, backfilling should take place after the excavation work is complete. Usually, the exact timeline will depend on several factors such as the specific project that is being worked on. Some professionals may suggest backfilling days or weeks after the excavation depending on the existing conditions in the area.

As an example, for backfilling foundation work, it is crucial to wait for a curing period of at least a week (or more depending on the concrete mixture). This is done to prevent the cracking of the completed base or to avoid possible ruptures. It is important to remember that the timeline of backfilling may be longer or shorter as it will also depend on the area’s local temperature. Since weather conditions can affect the curing period, contractors often advise owners to be patient during the entire excavation and backfilling process.

Factors that affects the backfilling process

There are three primary factors that can affect the backfilling process, especially when it comes to foundations:

·      The matter of choosing the appropriate backfill material

As mentioned earlier, the method of backfilling requires the use of soil to cover an excavated hole. Depending on the project, there are certain types of soil or earth that can be used to fill the cavity. There are two options when choosing the backfill – either the excavated material is used or imported soil will be secured for the process.  Many types of soil, or earth, can be used including sand as a backfill.

When we talk about backfilling using excavated material, it is the soil that has been taken during the excavation process. For example, when a trenching hole is dug to install a utility line, the excavated soil is set aside and then returned after the installation process.

On the other hand, if backfilling is done with imported soil, this means that the latter is taken from another site or is specifically purchased for the procedure. This method is necessary when the excavated material is no longer useable or is unsuitable for the construction project.

·      The matter of compacting the backfill

After the appropriate material has been decided, it is now the time to choose the suitable compacting method for the backfilling process. Unfortunately, before the options are laid out, inspections are necessary in order to select the compacting technique. This is because some techniques work best in certain types of soil and projects.

There is also the matter of choosing the necessary equipment that will not mess with the current structure built on the property. Aside from this, contractors should also determine the amount of water necessary to keep the soil intact while preventing swelling or turning the fill into a slurry.

Some of the best-known compacting styles:

  1. Vibrating - This method drives a mechanical hammer or plate on the backfill to compact the area.
  2. Rolling – This method uses a large cylinder to roll it on the surface of the backfill.
  3. Kneading – This method applies alternating movement in different positions to compact the backfill.
  4. Impact – This method makes use of a large mass and drops it onto the soil to compact it.
  5. Static – This method slowly applies a heavy amount of stress until it completely releases and flattens the area.
  6. Gyrating – This method makes use of a gyrating motion while compacting a specific area.

·      And the period or timeline of backfilling

As said earlier, the weather during the backfilling process may hinder it from achieving the best results. Because of this, ample planning is necessary in order to avoid rains and storms that can wet the soil in extreme amounts. Owners are made to understand that backfilling should not be rushed or just inserted into a construction schedule. For example, if the worker backfills before the foundation have not yet cured, then they are sacrificing the quality and integrity of the entire structure.