Improved solutions and nondestructive methods for generating the geotechnical profiles used for project design.
Understanding how subsurface site conditions affect project design and construction is critical to ensuring safe and cost-effective projects. Implementing advanced geotechnical exploration methods will improve project decisions, leading to shortened project delivery times and cost savings that significantly benefit the traveling public.
Improved Subsurface Investigation Data
Differing site conditions represent a significant number of cost escalations and delays on highway and bridge construction projects. These problems arise when the site conditions encountered differ from those documented in the geotechnical reports and contract documents developed from prescriptive and minimal subsurface exploration programs. Currently, design engineers rely on limited investigation data for subsurface characterization and inference to generate the geotechnical profile used for the design. Unfortunately, since ground conditions influencing design and construction can vary widely within the project site, making decisions with incomplete or limited information can result in costly constructability issues and claims.
Issues resulting from inadequate subsurface investigations led the industry to develop nondestructive geophysical methods capable of efficiently measuring properties that can be correlated to the engineering properties required for design and construction. These methods, in combination with drilling, sampling, and testing techniques, improve the confidence in and reduce the uncertainty of the geotechnical characterization.
Nondestructive geophysical methods provide two-dimensional (2D) and three-dimensional (3D) subsurface images, distinguishing material and groundwater changes both laterally and with depth across a project site. Mischaracterized groundwater and other unanticipated “changed conditions” that delay projects and escalate costs can be reduced or altogether avoided. When coupled with rapid and reliable in-situ field testing, project designs become more efficient and less conservative.
- Reduced Risk. Reducing uncertainties in subsurface conditions mitigates design and construction risks.
- Improved Quality. Improving confidence in the geotechnical characterization reduces unnecessary conservatism in design and establishes a more reliable basis for design and construction of foundations and other geotechnical features impacting the highway system.
- Accelerated Project Delivery. Since a significant number of construction delays can be attributed to inadequate knowledge of subsurface site conditions, nondestructive geophysical methods improve decision making and constructability, providing time and cost savings for transportation agencies.
State of the Practice
Advancements in computer processing, data acquisition, data management, and hardware have improved the functionality and time requirements needed to progress geotechnical exploration methods. State departments of transportation currently incorporating these advanced methods within project geotechnical site characterizations include California, Florida, Minnesota, Missouri, and the Office of Federal Lands Highway.