Accuracy and Bias of TDR Measurements in Compacted Sands

• Main Author: White, Newel Kimball
• Format: Others
• Published: Scholar Commons 2004
• Subjects: water content; dry density; dielectric constant; electrical conductivity; nuclear; American Studies; Arts and Humanities
• Online Access: https://scholarcommons.usf.edu/etd/1300; https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2299&context=etd

It is essential to properly monitor in-situ soil compaction properties during most earthwork construction projects. Traditional in-situ soil compaction monitoring methods are often limited in their application. As a result, new methods are being developed to more accurately measure in-situ compaction parameters. Time domain reflectometry (TDR) is one such method. Relying on the propagation of an electromagnetic wave through the soil sample, TDR can be used to measure both in-situ moisture content as well as soil dry density. Although TDR is relatively new to the field of geotechnical engineering, it has previously been implemented in other fields with success. Researchers at Purdue University have made several advances to further incorporate the use of TDR technology into the field of geotechnical engineering and as a result an innovative TDR measurement system has been developed for compaction control monitoring. The method was standardized in the form of ASTM D 6780 in 2002. Further advancements led to an improved method referred to as the Purdue one-step TDR method. Research has indicated that the ASTM TDR method is sufficiently accurate for application in compaction monitoring applications. A comparison between the ASTM TDR method and traditional methods was carried out to evaluate the accuracy of the TDR method to traditional methods. To further expand the application of the TDR method, a correlation was developed between the TDR spike driving process with the in-situ CBR test. A comprehensive review of previous research was conducted to examine recent advancements leading to the improved Purdue one-step method. A study was also performed to evaluate the effect of variable pore fluid conductivity on the calibration of the Purdue one-step method.