Abstract
Soil water retention curves (SWRCs) form an essential component of frameworks coupling the hydromechanical behaviour of unsaturated soils. The curves describe how suction changes with variables such as degree of saturation, void ratio and volumetric/gravimetric water content. SWRCs can be determined from incrementally drying initially saturated reconstituted samples to a final residual state, thus developing the primary drying curve (PDC). The primary wetting curve (PWC) is established from subsequent incremental wetting from residual state and is hysteretic compared with the PDC. SWRCs for reconstituted, high-plasticity, tropical clays from Africa (Sudan, Tanzania and South Africa) will be produced using suction measuring instruments, a tensiometer, filter paper and a dew point potentiometer. The development of SWRCs under various subsequent cycles of drying will be presented and discussed along with details concerning volumetric changes and cracking during drying. In order to investigate the uniqueness of the PDC and PWC and the effect of initial void ratio, SWRCs will be determined for samples formed by reconstituted from slurry under different applied energy levels.
Highlights
A partially saturated soil is a complex multi-phase system consisting of air, water and solid material whose response is a function of the stress state, moisture condition and other internal variables present within the soil [9]
This paper presents the results of laboratory works conducted at Cambridge University on two natural soils from two locations in Africa: a black cotton clay from Sudan (Al Fao) and Atta clay from Steelpoort, South Africa (SA)
soil water retention curves (SWRC) has been produced by pairing of three suction measuring techniques, a tensiometer, a dew point potentiometer (WP4C) and filter paper
Summary
A partially saturated soil is a complex multi-phase system consisting of air, water and solid material whose response is a function of the stress state, moisture condition and other internal variables present within the soil [9]. SWRCs generally have a sigmoidal form and plays a key role in recently proposed constitutive models and have been used to predict the compressibility during virgin loading [10], shear strength [2] and volume change behaviour of unsaturated soil. Data for developing SWRCs are often obtained by incrementally drying initially saturated, reconstituted samples to a final residual state, at which Sr remains constant, developing what is often referred to as the primary drying curve (PDC). The wetting-up process can commence by adding small amounts of water to the sample in incremental stages. Both drying and wetting curves can be drawn (generally as log s versus Sr) from these measurements. The model given by van [15] is commonly used, for which the residual point needs to be defined
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