Device Comparison for Determining Field Soil Moisture Content

Abstract

Abstract : During the period May 2010-August 2010, researchers of the U.S. Army Engineer Research and Development Center in Vicksburg, MS tested the effectiveness of various devices in determining the moisture content of soil for horizontal construction. These tests were conducted to determine a usable alternative to the nuclear soil density gauge. The accuracy and precision of the different testing devices was compared to the standard laboratory oven soil moisture determination. The devices and techniques tested are grouped into four broad families: gravimetric, electrical, chemical, and nuclear. Gravimetric devices and techniques tested were the laboratory oven, gas stove and fry pan, standard microwave oven, battery-powered field microwave oven, and moisture analyzer. Electrical devices tested were the electrical density gauge, and the soil density gauge. The chemical device tested was the Speedy Calcium Carbide soil moisture test. The nuclear device tested was the nuclear density gauge, included for comparison purposes. This investigation consisted of full-scale construction of seven soils representing a range of materials encountered in operational construction activities. Soils ranged from fine-grained silts and clays to coarse-grained gravels and crushed limestone. This testing showed that the devices showing the optimal combination of precision and accuracy compared to the laboratory oven are the soil density gauge and the gas stove with fry pan technique. Results of the moisture content tests are presented and include (a) comparison of the individual moisture contents to the results obtained using the standard laboratory oven, and (b) ranking of devices versus laboratory oven. Results will be used to provide further guidance for selection of appropriate devices for field determination of soil moisture content.