American Society of Civil Engineers

In-Place Stiffness and Modulus Measurements

by Scott A. Fiedler, (Humboldt Mfg. Co., 7300 West Agatite Avenue, Norridge, IL 60706 E-mail:, Melvin Main, (Main Associates, 16 Vegas Drive, Hanover, PA 17331 E-mail:, and Albert F. DiMillio, (FHWA, USDOT, Turner-Fairbanks Highway Research Center, McLean, VA 22101 E-mail:
Section: Performance and Evaluation of Roadways and Railways, pp. 365-376, (doi:

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Document type: Conference Proceeding Paper
Part of: Performance Confirmation of Constructed Geotechnical Facilities
Abstract: There is a broad interest and certain expectations in knowing the in- place engineering and performance properties of the compacted or stabilized soil. This has been the case since soil was thought of as an engineered structure. The processes of removing small numbers of specimens and then conditioning the specimens to represent the actual site are estimates at best. A great deal of skill is required to accurately prepare the specimens to approximate field conditions and provide meaningful and believable laboratory test results. Density based measurements have been surrogates for material modulus and structural stiffness. Available tests to measure the in-place properties are cumbersome, destructive and time consuming. Recently, a new device has been developed that does what the geotechnical community has desired, measure the in-place engineering and performance properties of the soil structure. Conceived and developed partially by funding from FHWA, it is now commercially available. Fast and immediate measurements of stiffness and modulus allow the compaction process to be controlled by the contractor without delay or outside feedback and should provide a more uniform structure. Control of the compaction process via stiffness and modulus permits construction to performance specifications derived directly from design. The use of one test method to link design, specification, construction, and maintenance appears to complete a loop that ultimately enables contractor warranties. This paper will examine the use of the device and the practical implementation of various functions or processes that the device offers.

ASCE Subject Headings:
Soil modulus
Soil structures