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The coefficient of permeability can be determined as a function of vertical strain in an oedometer test (see Fig. 3.9). The method is normally used for fine-grained (frictionless) soils to estimate their consolidation characteristics. The oedometer test is usually performed either as a constant stress or constant-rate-of-strain test. In a one-dimensional constant stress test a […]

In the falling head test the head is a function of time during testing while water from a standpipe flows through the soil. The falling head test is preferably used for soils with low permeability, i. e. silty or clayey soils (see Fig. 3.8). For such soils the problem of excessively high hydraulic gradients (Fig. […]

Traditionally in geotechnical engineering, the saturated permeability is estimated in the laboratory in a constant head test for coarse grained soils whereas a falling head test is used for fine grained soils. An oedometer test can also provide a measure of the saturated permeability for fine grained soils in the laboratory. Field tests which provide […]

The permeability of soils is a material parameter that relates the rate of water flow to the hydraulic gradient in the soil and, therefore, determines the material’s suitabil­ity for drainage layers. An embankment usually consists of compacted materials. The compaction often results in anisotropy such that the vertical and the horizontal permeability properties are not […]

A number of other methods exist for estimating soil water content such as nuclear magnetic resonance (NMR), which can detect nuclear species that have a magnetic moment or spin. As hydrogen has a nuclear spin of 1/2 the NMR technique can be used to estimate water content in soils. This is a fast and non-destructive […]

Capacitive sensors measure the resonant frequency of an inductance-capacitance (LC) tuned circuit where the soil located in between two flat waveguides is the dielectric material. The inductance is kept constant and the resonant frequency f measured and therefore the capacitance can be calculated from 2n ^ e where Le is the inductance and Ce is […]

In Ground Penetrating Radar (GPR), electromagnetic waves are sent out from a transmitter on or above the ground surface and picked up by a receiver after pene­trating and returning from the soil. The velocity of the electromagnetic wave propa­gation in soils is dependent on the soil bulk permittivity modulus (Grote et al., 2003). Thus the […]

Time Domain Reflectometry (TDR) is a non-destructive electromagnetic technology that utilises the relationship between the relative permittivity (usually known as the dielectric constant, кг) of porous materials and their water content. Dry soils have values of dielectric constant of around 2-6 but water about 79-82 depending on wave frequency and water temperature. As the water […]

A number of methods exist for estimating the soil water content of road materials in a non-destructive way assuming that the instruments are placed in the road duringthe construction phase. They are all indirect methods as they involve measurements of some property of the material affected by the water content or they measure a property […]

A fundamental parameter that characterises the water movement in pavements is the water content. This provides information on the condition of the road layers regarding the moisture saturation stage, which controls the main parameters in the governing equations for water flow (see Chapter 2, Section 2.8). A number of meth­ods are available for measuring water […]