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Broadly graded aggregates, as typically used in granular base and sub-base layers of the road construction have relatively small pores as the large pores between the coarser particles are mostly filled with smaller particles. This means that coefficient of permeability values, as characterised by the Darcy coefficient, K, are relatively low. Laboratory testing of typical […]

Water flow in unsaturated soils is primarily dependent on the volumetric water con­tent, matric suction and on the gravitational potential. Due to the presence of air within part of the pores, water movements are obstructed and flow is only achieved through the finer pores or in films around the soil particles. The permeability (or “hydraulic […]

There is a number of parametric models that have been suggested in the literature for describing the matric potential’s dependency on water content (matric poten­tial being defined in Eq. 2.26). The models are all empirical and two frequently used are the power law model suggested by Brooks and Corey (1964) and the model suggested by […]

The soil water characteristic curve (SWCC) provides the relationship between the matric suction and water content for a given soil. In fact, calling the curve “character­istic” is something of a misnomer as the relationship is not solely a function of the soil type, but varies with (for example) temperature, pressure and pore water chemistry. A […]

The groundwater table is defined as the locus of points at atmospheric pressure. Below the water table the pore water pressure is positive and in a hydrostatic state, while the pore water pressure increases linearly with depth. Above the groundwater table, in the vadose zone, water only remains in the pores due to capillary action. […]

Pavement structures consist of material layers with different grain size gradations and different mechanical as well as permeability properties. As water will flow through the structure it is important that migration of a portion of the fines from one layer to the next will not take place. To achieve this, the principles of fil — […]

Predicting the saturated permeability of soils or aggregates based on theoretical con­siderations has turned out to be difficult as permeability is dependent on a number of factors such as grading, void ratio, soil texture and structure, density and water tem­perature (Cedergren, 1977). Therefore, several empirical equations for estimating the permeability have been proposed in the […]

Water flows though porous media from a point to which a given amount of energy can be associated to another point at which the energy will be lower (Cedergren, 1974, 1977). The energy involved is the kinetic energy plus the potential energy. The kinetic energy depends on the fluid velocity but the potential energy is […]

Porosity is defined as the space inside a rock or sediment (soil), consisting of pores. The total volume of pores is defined as the total porosity. For water, only those pores that are interconnected are important. The interconnected part of the pore system is defined as the effective porosity. The porosity can be described as […]

Roads and embankments are made up by a finite number of layers. They can be considered as porous media that consist of aggregates or granular materials and soils through which fluid can flow. The road layer can appear either unbound or stabilized with bitumen or cement to increase their strength. In roads, most surface layers […]