Influence of initial dry density on soil-water characteristics of two compacted soils

Abstract

This article presents the results of a laboratory test programme on two different soils, conducted to examine the influence of the initial dry density on the soil-water characteristic curve elements along drying and wetting paths. Particular attention was paid to determine the contributions of the initial compaction effort to the rates of saturation and desaturation, size of hydraulic hysteresis, air entry and air expulsion values. Drying and wetting tests were performed on samples compacted to different dry densities with identical water contents. The general patterns observed are discussed and compared in relation to some available data from the literature in order to determine the applicability of the detected trends to other soils. Additionally, it is shown that the horizontal separation of the air entry and air expulsion values could be a suitable method for estimating the size of hydraulic hysteresis.

California bearing ratio of an unsaturated deformable pavement material along drying and wetting paths

“…The index properties of test material were again measured, and the results, summarised in Table 1, appeared to be consistent with the data in Mirzaii and Yasrobi (2012). The variation of degree of saturation versus matrix suction of test material, already obtained by Mirzaii and Yasrobi (2012), is presented in Table 2 for a range of initial void ratios (e 0 ) along wetting paths, and they are utilised in the current study.…”

“…This soil was previously used in Mirzaii and Yasrobi (2012) to examine the void ratio dependency of SWCC elements along drying and wetting paths.…”

“…The variation of degree of saturation versus matrix suction of test material, already obtained by Mirzaii and Yasrobi (2012), is presented in Table 2 for a range of initial void ratios (e 0 ) along wetting paths, and they are utilised in the current study.…”

“…During the compaction stage, the degree of saturation within the soil increased; therefore, the compacted soil samples were located on the wetting portion of the SWCC (Mirzaii & Yasrobi, 2012). Finally, 4.54 kg surcharge weights were placed above the compacted specimens and they were appropriately installed inside the CBR apparatus.…”

“…For instance, many of the road pavement materials are subjected to different drying and wetting hydraulic loadings, and the bearing ratio and any deformation of the subgrade layers are highly affected by the changes in degree of saturation or matrix suction of the soil. Another issue to be pointed out is the significant influence of hydraulic hysteresis on the mechanical behaviour of unsaturated soils, as already reported by Miller, Khoury, Muraleetharan, Liu, and Kibbey (2008), Khalili and Zargarbashi (2010), Nowamooz, Chazallon, Arsenie, Hornych, and Masrouri (2011), and Mirzaii and Yasrobi (2012, which has not received a level of attention in previous experimental studies on CBR.…”