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Testing the Soil Where It Lies

In Situ Services Bring Value, Efficiency to Transportation Projects

As the speed of business increases, today’s large transportation projects become reality via a design-build process to streamline and accelerate delivery.

This on-the-go method requires flexibility and versatility, and sometimes can’t slow down for soil testing data from traditional geotechnical methods and lab analysis. That’s why in situ testing can be a valuable resource.

In situ testing defined

In situ testing involves testing soils in place, as they exist in the subsurface. It provides a higher level of detail to site investigations, in many instances providing data that would normally be generated only after the time and costs associated with laboratory testing. Risk and uncertainty are characteristics of the subsurface and are never fully eliminated, however a robust exploration program with in situ testing can significantly increase our understanding of the site conditions and improve the ability to meet project design objectives and potential cost savings.

Terracon’s experts use a variety of methods, including cone penetration testing (CPT), dilatometer testing (DMT), field vane shear testing (FVST), and pressuremeter testing (PMT). Additionally, formations can be tested for hydraulic conductivity using inflatable packers. The subsurface conditions can be monitored with the installation of geotechnical instrumentation to include inclinometers, vibrating wire piezometers, magnetic extensometers, and other instrumentation placed in the ground to measure the strength and performance of the soil and rock during and after construction.

The advantages of in situ testing extend well beyond the time saved by not having to send samples off-site for analysis. CPT data, for example, provides a nearly continuous soil profile that includes correlations to the soil type, strength parameters, groundwater levels, settlement parameters, and permeability. The data and tests are repeatable, with a higher level of quality. Also, more data can be collected over the course of a day. Faster data collection means faster analysis, more data, and less client wait time for needed information. Turning around geotechnical data and laboratory testing data collected by traditional methods can take several weeks. In situ testing data, meanwhile, can be turned around in just days.

The value of accurate in situ data

In situ testing eliminates assumptions about soil performance. It tells our professionals exactly how soils will behave. With this information, foundations on transportation projects can be designed knowing the exact strength of the soil. If as little as 12 inches can be shaved off the length and embedment depth of bridge piles on a large project, the cost of materials and construction can be significantly reduced.

Terracon is committed to further growing our in situ testing capabilities for our clients. We’re investing in more training and resources for our nationwide network of professionals, as well as the equipment, tooling, and rigs needed to meet growing project demands. Contact us to learn how our in situ services can benefit your next project.

Tim Cleary is Terracon’s National Manager of In Situ services. He has more than 30 years of experience leading exploration operations serving consulting engineers and geologists.