Exploring the Ground Beneath
Pavement Investigation
Roadways are the backbone of our communities. They connect us to where we live, work, learn, and gather—forming the foundation of daily life. But before a new road can be designed or built, or an existing distressed road can be rehabilitated, engineers need to understand what’s already there. That begins with testing the existing pavement and uncovering the conditions beneath the surface.
This critical step helps ensure that the new road, or rehabilitated road will be safe, durable, and tailored to meet the specific needs of the site.
Coring for the Turlock Capital Improvement Program
As part of our ongoing work with the City of Turlock on existing distressed roadways, Siegfried’s Geotechnical team performed pavement investigations. The pavement investigations typically comprised extracting field cores, laboratory testing, and engineering analysis—a vital process in understanding how to rebuild or rehabilitate existing roads.
Coredrilling into existing pavement to extract cylindrical samples, called cores, allow for a direct measurement of thickness and evaluation to assess the current pavement structure and the conditions below. Using our specialized core rig attached to a standard pickup truck, our team can extract from 8 to 15 cores per day along a roadway alignment. The production rate of extracted cores depends on mobilization from location to location, sampling, in-situ testing performed, and traffic control requirements.
But the work doesn’t stop there.
Once the core is removed, our team goes a step further by using a hand auger to sample the layers of roadbase, if encountered, and underlying soil subgrade that supports the pavement. These samples are tested in the certified laboratory, where we determine the routine index parameters and/or R-value of the underlying materials. We also perform a detailed observation and grading of the roadway and note the type and magnitude of distress noted along with any potential constructability challenges that should be considered in design.
Where distressed pavement needs rehabilitation or reconstruction to improve the performance or extend pavements life cycle, a pavement investigation is a necessary component for evaluation of the many forms of rehabilitation and reconstruction methods that are appropriate for the project. While certain rehabilitation methods are appropriate for various subsurface conditions, they are not always constructable without any obstacles. For example, subsurface conditions in Turlock were suitable for conventional asphalt concrete (AC) over aggregate base (AB), full depth asphalt concrete, or full depth recycling with cement (FDR-C). Based on our observations and knowledge gained from the pavement study and given the presence of numerous shallow utilities that would limit production rates, preference was given to using a full-depth asphalt concrete section to reduce the amount of invasive work. Understanding what’s below the surface allows our engineers to design a roadway that is constructable and won’t just look new—it will function reliably for years to come.
Designing with Confidence
At Siegfried, we believe that lasting infrastructure starts with informed decisions. By combining field expertise with detailed lab analysis, we provide our clients with creative and innovative solutions rooted in real-world data. Our work in Turlock is just one example of how we explore the ground beneath to build the future above.
