The nature of changes in bulk density with water content in a cracking clay

Abstract

The effect of changing water content on the bulk density of undisturbed cores of a cracking clay was examined in laboratory experiments. The results were compared with the relationship between bulk density and water content established by core sampling the same soil in the field. Over the water content range measured in the field soil, the laboratory cores shrank three-dimensionally and normally. Small departures from normal shrinkage were attributed to the formation of cracks within the cores, and to the occurrence of some structural shrinkage in cores previously wet to high water contents. Swelling of cores was approximately three-dimensional, except for some unconfined swelling which occurred in the core surface. Unidimensional swelling was induced by confining dry cores to reduce the void ratio before wetting. Subsequent shrinkage was three-dimensional, indicating that the soil particles were reoriented during the unidimensional swelling phase. While the laboratory measurements showed that the soil volume changes were essentially three-dimensional and normal, the field data indicated that unidimensional shrinkage occurred at water contents greater than 0.47 g g-1. These field results were attributed to sampling inaccuracies associated with the use of a small-diameter core sampler, the actual field bulk density relationship being considered three-dimensional.

Measuring and modelling the soil shrinkage characteristic curve

“…Berndt and Coughlan (1976) recorded the height and diameter of undisturbed soil cores as they dried out. A similar procedure was followed by Yule and Ritchie (1980a,b).…”

Physics of the soil medium organization part 2: pedostructure characterization through measurement and modeling of the soil moisture characteristic curves

“…While, in the rubber balloon method, reconstituted soil cores were used in most studies (Tariq and Durnford, 1993a;Cornelis et al, 2006). In this approach, the soil samples were submerged into water and then the change in the sample volume was determined from the volume of displaced fluid; (ii) physical measurement-based approach: where the soil cores "disturbed or undisturbed" dimensions were measured directly using a vernier caliper (Berndt and Coughlan, 1977;Huang et al, 2011), a linear displacement transducer (Boivin et al, 2004;Braudeau and Mohtar, 2004) or a thin metal stick (Kim et al, 1992); (iii) laser sensors-based approach: where the soil core diameter and height were determined through laser beams such as the retractometer apparatus (Braudeau et al, 1999), (iv) imagebased approach: where the volume of the soil sample (either clod or core) was either scanned with a 3-D optical scanner (Sander and Gerke, 2007) or by a simple standard digital camera (Stewart et al, 2012). Several studies have discussed and compared these methods, Cornelis et al (2006) showed that there were significant differences between the Archimedes' principlebased methods "paraffin-coated and rubber balloon methods" and the physical measurement-based methods "vernier caliper method" where the former produced more accurate and reliable data; however, Sander and Gerke (2007) observed some errors in the resin-coated method that affects the measured volume due to inadequate coating or penetration of the coating materials.…”

Mechanical, hydraulic, and dielectric characterisation of fine-grained soils during densification

“…Similar to [131], Schafer and Singer [132] measured the length of a rod-shaped soil sample under shrinkage using a calliper. The major disadvantage of measuring the soil sample dimension is that axis-symmetric volume changes are typically assumed [130]; hence, the volume determination of the irregular sample shapes is complicated.…”

“…Other techniques found in the literature are based on direct determination of the soil volume by measuring the sample dimensions in height and diameter [131,132,133,134,135].…”

“…Berndt and Coughlan [131] measured the dimension of soil cores during shrinkage by measuring the sample height using a dial gauge and the diameter using a flexible ruler. Similar to [131], Schafer and Singer [132] measured the length of a rod-shaped soil sample under shrinkage using a calliper.…”