New methodology for soil characterization using time domain reflectometry (TDR)
Abstract
Engineering properties of geomaterials used in fills and backfills predominantly influence the performance of earth structures such as roads, retaining walls and embankments. In order to assess adequate strength and compressibility of fill materials, specifications call for a minimum acceptable dry density and water content within a defined range. Field compaction control is a check on whether or not the geomaterials meet the specifications. Therefore, the dry density and water content of the fill materials need to be obtained in the field. The Time Domain Reflectometry (TDR) method is a leading electromagnetic wave method that has been widely used as field compaction control. The main objective of this research is to develop the next generation of TDR methodology for use in compaction quality control by: developing new calibration equations to replace the existing relationship between the soil bulk electrical conductivity (ECb) and water content from ASTM D 6780-05; checking the effects of compaction energy, temperature, pore fluid conductivity, and probe geometry on the performance of the newly proposed calibration equations; investigating the applicability of the calibration coefficients obtained from the controlled laboratory tests to be used in the field; validating the newly proposed calibration equations with determining the apparent dielectric constant (Ka) in lossy soils; exploring the potential for the self-calibrating TDR system. The newly proposed method and parameters are validated with a variety of laboratory and field tests from ASTM Reference Soils and other soils. The results from this research suggest that the newly proposed method could replace the relationships in ASTM D 6780-05. Furthermore, it suggests future directions for implementing the self-calibrating TDR system.
Degree
Ph.D.
Advisors
Drnevich, Purdue University.
Subject Area
Geotechnology|Civil engineering
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