What Is Compaction Grouting?

Compaction grouting, or pressure grouting, is a way to consolidate foundation soil by injecting grout into it. This process is used to provide stability for structures that have settled and for improving the ground underneath new construction before it begins.

How Is It Done?

First, an analysis of the ground is made and plans are drawn up. Then a series of grout injection pipes are installed in the ground to the required depth by either drilling or driving them in using a sacrificial point. They are usually placed in a grid pattern of 6 to twelve feet. The depth of the holes depends on the demands of the project, but grouting can be injected up to about 80 feet below ground.

Next, usually starting from the perimeter and working their way in, the workers begin injecting a low slump grout using a low volume, high pressure pump. Filling of the hole is done in stages. The pipe is withdrawn at a controlled rate (a few feet at a time) to give the grout a globular shape. Injection of the grout continues until a pre-determined pressure is reached or the ground begins to heave up. When all of the holes are filled, the ground will be more stable and you can begin your construction or have peace of mind that your foundation will not collapse on you anytime soon. This entire process can also be used in combination with underpinning to rise up a home that has sunken in.

Do not attempt to follow these steps yourself. They are just an overview of a complex process. It is important that you contract with a fully licensed and bonded professional who specializes in this type of work. This method of soil consolidation is a costly and sometimes risky procedure–especially if you don’t know what you are doing–that requires equipment designed specifically for it.

Why Does Compaction Grouting Work?

Let’s start by defining soil consolidation. Consolidation refers to the process of decreasing soil by volume. In our application, that is usually done by first compressing the soil with heavy equipment (like a roller, for example). When pressure, or stress, is applied to the soil it causes the particles to squeeze together tightly, reducing the volume and creating a more stable foundation. If that pressure is lessened or removed, the soil will rebound and regain some of its volume. This can be caused by a variety of things, including water absorption. Compaction grouting will fill any voids and reapply pressure to the soil so it stays more compact.

If you would like to find out if compaction grouting is the solution to your problems, contact a local company to have an analysis done.