Observations on soil permeability, moulding moisture content and dry density relationships

Abstract

Increasing use of the coefficient of permeability as a quality control parameter for earthworks, in particular for landfilling, has resulted in many engineers looking to predict coefficients of permeability for clays from more widely available but often widely scattered data. In a number of cases this has led erroneously to the interpretation of the moisture contentcoefficient of permeability relationship as the direct inverse of the moisture content-density relationship. This paper reexamines the original theories proposed for movement of water through soils of differing grain size and goes on to show that extrapolation of the permeability-density relationship for granular soils to finer grained soils is incorrect. Laboratory permeability tests were conducted on four different soil types using the falling head permeameter to investigate the relationships between permeability, dry density and moulding moisture content for each soil. Coefficients of permeability were determined for moisture contents up to the liquid limit of the soil. It is shown that a minimum value of permeability is obtained close to optimum moisture content and that this is maintained to within sensible engineering limits for moisture contents up to that of the liquid limit. Results obtained for predominantly granular soils confirm that permeability is a function of density but, for more cohesive soils, permeability is unaffected by changes in moisture content wet of optimum. Conclusions emphasise that to achieve minimum possible coefficients of permeability there is a need for soil water content at placement to be at or slightly above optimum moisture content and for pelletization of clay material.

The Influence of Fine Fractions Content in Non-Cohesive Soils on Their Compactibility and the CBR Value

“…Laboratory tests, that were carried out have shown that further enhancement of the content of fine fractions, when the maximum soil compaction have been reached, contribute to the increase of the amount of water in the soil sample, that is necessary to obtain the optimal moisture content (OMC), while the dry density decreases (MDD) -see Figures 5 and 6. Non-linear dependence between the compactibility parameters (the maximum dry density and optimum moisture content), that were obtained in the Proctor Compaction and the fine fraction content was also confirmed by many papers regarding both natural and stabilized soils (Hossain et al, 2016;Sulewska & Tymosiak, 2018;Gupta & Thomas, 2013;Wright et al, 1996;Zhemchuzhnikov et al, 2016;Osouli, Salam, Tutumluer, & Shoup, 2017). This clear relationship developed between the compactibility parameters and the CBR value causes that numerous scientific studies attempt to predict the CBR value based on Maximum Dry Density (MDD), Optimum Moisture Content (OMC), the content of sand, clay or silt fractions (Sreelekshmypillai & Vinod, 2017;Katte, Mfoyet, Manefouet, Wouatong, & Bezeng, 2019).…”

“…The results are presented in Table 1. Conducted research, as well as analysis performed by other authors, point to some regularities in changes of the compactibility parameters of tested soil samples (Sulewska & Tymosiak, 2018;Gupta & Thomas, 2013;Wright, Walden, Sangha, & Langdon, 1996;Zhemchuzhnikov, Ghavami, & Casagrande, 2016;Roy, 2013). Mentioned changes depending on the content of fines and sands in testes soil are clearly visible (Satyaveni, Sridevi, Sivanarayana, & Prasad, 2018).…”

Prediction of overland flow and seepage zones associated with the interaction of multiple infiltration devices (cascading infiltration devices)

“…Clod theory predicts (e.g. Wright et al, 1996;Trenter, 1999;Osinubi and Eberemu, 2006) that the fluid flow through the clay will remould and aggregate the clay clod particles (through partial fluidization and flocculation) and that the dominant flow during recharge will be inter-clod. Experimental evaluation of clod theory has established (e.g.…”

Insights into the hydraulic performance of landfill-lining clays during deformation

“…Exactly how the microstructure changes will depend on the conditions of placement, e.g. compactive effort, moisture content and the size of clods being compacted to form the liner (Wright et al 1996).…”