America’s Foundations – Deep Foundations

America’s Foundation with Gary Seider: Deep Foundations

In this edition of America’s Foundation, Gary Seider leads a discussion of deep foundations. Brent Chisholm, Russel Adkins and Phil Schied break down the processes behind driven piles, pile capacity, and elaborate on the types of foundations. Read a summary of this video below, and watch the full version to learn all about deep foundations from the industry’s top professionals.

What is a Deep Foundation?

A deep foundation is a foundation that is installed to significant depth so as to handle a specific load. Defined by its depth to length ratio, the depth will usually have to go beyond 10 feet deep in order for the foundation to truly be a deep foundation.

How Deep Can Driven Piles Go in a Deep Foundation?

That depends on the type of soil you have. Soils can vary, and piles should be installed to the load bearing strata of the soil. In some parts of the country, like New Orleans, this can be up to 100 feet. However in other parts of the country, such as Texas, it can be 7-10 feet.

Why Use a Deep Foundation?

From the upper Midwest to Colorado, deep foundations are used to get the weight of a structure deeper into the soil. Whether it’s in the Midwest where it’s 20 feet, or the Rocky Mountain Region where you’re reaching up to 50 feet, installing a helix to depth in a load bearing level of soil requires a deep foundation.

When Should You Choose a Deep Foundation?

An engineer will make the decision on whether or not to use a deep foundation based on existing site conditions. You don’t always have to use a deep foundation, and engineers will have a database of the various foundations at their disposal. They will be able to select the appropriate foundation for the relative application using their resources. If you have expansive clay for example, an engineer would help you determine that you can use a helical pile with less shaft surface area to reduce the potential for swelling soils to cause foundation problems.

How To Handle Expansive Soils

Helical piles and resistance piers are advantageous in expansive soils. When soil starts to swell from moisture, it can grab onto deep foundations and they can potentially be upheaved out of the ground. Concrete piles or drilled shafts were used in the past for expansive soils, but with the expansive nature of soil helical piles are much more reliable because the surface area is less making it harder for the soil to grab. Piling, sheet piling, pipe piling and other conventional means of installation that people are familiar with changed in the 1980’s when CHANCE developed helical piles.

Watch the full video to see Gary and his team explain driven piles, pile capacity and soil modification techniques.