Special Topics in Structures

Single Abstract

340927 - Innovative Technologies to Combat Expansive Soils

Saturday, April 21
8:00 AM - 9:30 AM
Location: 204AB

As population centers grow in the central and coastal regions of Texas, structural engineers will have more interaction with expansive clay soils. Costly foundation damage can occur if the slab is not properly engineered for active soils. It will be essential to provide cost-effective, environmentally-friendly, and sustainable solutions.

The Central Texas corridor and the coastal region of Texas have some of the most expansive soils in the country. These regions are also the most populated. Houston and DFW are the 4th and 5th largest metropolitan area in the U.S. and these regions have 4 of the top 10 fastest growing counties in the U.S. As these regions grow, so will demand for new construction which will inevitably occur in the presence of expansive soils.

Currently, there are several solutions for dealing with expansive soils. Each has its own advantages and disadvantages. Void form products are susceptible to damage due to rain or unexpected foot traffic. Laying out carton forms can be time-consuming and create additional complications during the construction phase. Water-injection and moisture conditioning use chemicals and water to reduce the PVR, but these methods can be harmful to the environment and the initial moisture content may change over time. Not only does it affect the water supply, but it can also harm vegetation on the site. Importing select fill is expensive, time consuming and destroys all vegetation on the site as the old soil must be removed. For the ultimate performance, a suspended slab, which takes soil movement out of the equation, is preferred, but can be expensive and time consuming.

A new slab-lifting solution combines the structural quality and performance of a suspended slab with the construction ease of a slab-on-grade. By pairing a lifting bolt with an embedded lifting mechanism, a height-adjustable structural slab is created. The slab is poured on grade and after curing, the slab is lifted to its final elevation. This final lifted height is often 1.5x the potential vertical rise (PVR).

Combining slab-lifting technologies with helical piers provides additional benefits. Deep piers are often used to reach a stable bearing stratum. These piers, particularly belled piers, can be cost-prohibitive because of excessive material costs and labor. Steel helicals can achieve the same bearing capacities and stability, but at a shallower depth. Helicals provide additional flexibility because they can be removed and reinstalled in case there are construction complications. Faster installation leads to shorter construction schedules. These benefits provide a cheaper overall construction budget which saves the owner money. A county saves money for the expansion of a community college. The lower bond proposal saves taxpayers on their property taxes. A school district saves money on the construction of a new school, and puts that savings into the classrooms where it can directly improve the learning environments by implementing modern technology.

Expansive soils pose a significant problem for the future of structural engineering. However, these problems provide an opportunity for innovation – innovation that can improve our communities.

Jim Fontaine

CEO
Tella Firma Foundations

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Chase Gooding

Structural Engineer
Tella Firma Foundations

Chase Gooding received his Bachelor of Science in Civil Engineering, specializing in Structures, from Texas A&M University in 2007. He then earned his Masters of Engineering in Civil Engineering (Structures) in 2008. Chase received his P.E. license (TX #114287) in May 2013. During his 9 years of experience designing schools, churches, and retail buildings across the United States and the U.S. Virgin Islands, he has been involved in all phases of construction and client relations. He has extensive experience designing steel framing, reinforced masonry, retaining walls, footings, piers, and grade beams, as well as analyzing loads for wind, snow and seismic. In May 2017, Chase began working for Tella Firma Foundations developing products, assisting clients in their engineering designs, and researching new avenues in foundation engineering.

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Grant Russell

Director of Sales
Tella Firma LLC

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