Non-Nuclear Alternatives to Monitoring Moisture-Density Response in Soils

Abstract

Abstract : During the period May-August 2010, researchers of the U.S. Army Engineer Research and Development Center in Vicksburg, MS, tested the effectiveness of various devices to determine the dry density, or modulus, of soils for horizontal construction. These tests were conducted to determine a usable alternative to the soil nuclear density gauge. The accuracy and precision of the different testing devices were compared to the density values obtained from the soil nuclear density gauge. The devices and techniques that were tested are grouped into four broad families: nuclear, electrical, volume replacement, and modulus-based. The nuclear device was the nuclear density gauge that was included for comparison purposes. Electrical devices that were tested were the electrical density gauge, the moisture + density indicator, and the soil density gauge. Volume replacement density-determining techniques; were the sand cone, the steel shot, and the water balloon tests. Modulus-based devices were two different lightweight deflectometers, a dynamic cone penetrometer, the Clegg hammer, and the GeoGauge. 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. The test results indicated that the soil density gauge corrected with a sand cone density measurement, demonstrated the optimal combination of precision and accuracy compared to the nuclear density gauge. Results of the tests are presented and include (a) comparisons of the dry densities of the various devices to the reported dry densities of the nuclear gauge, (b) ranking of the density devices according to agreement with the nuclear density gauge, and (c) field results of modulus-based devices. Results will be used to provide further guidance for selection of appropriate devices for field determination of soil density.