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Erg Chebbi, Morocco. The effective stress can be defined as the stress, depending on the applied tension and pore pressure , which controls the strain or strength behaviour of soil and rock (or a generic porous body) for whatever pore pressure value or, in other terms, the stress which applied over a dry porous body (i.e. at =) provides the same strain or strength behaviour which is observed ...
Substantially, the effective stress definition is conventional and related to the problem being treated. [5] Among various effective stress formulations, Terzaghi's one seems particularly appropriate, for its simplicity and as it describes with excellent approximation a wide variety of real cases.
The shear strength of soil depends on the effective stress, the drainage conditions, the density of the particles, the rate of strain, and the direction of the strain. For undrained, constant volume shearing, the Tresca theory may be used to predict the shear strength, but for drained conditions, the Mohr–Coulomb theory may be used.
Realistically, the effective stress is greater than the total stress, as the pore water pressure in these partially saturated soils is actually negative. This is primarily due to the surface tension of pore water in voids throughout the vadose zone causing a suction effect on surrounding particles, i.e. matric suction.
The coefficient of lateral earth pressure, K, is defined as the ratio of the horizontal effective stress, σ’ h, to the vertical effective stress, σ’ v. The effective stress is the intergranular stress calculated by subtracting the pore water pressure from the total stress as described in soil mechanics. K for a particular soil deposit is ...
The first equation determines the magnitude of the deviatoric stress needed to keep the soil flowing continuously as the product of a frictional constant (capital ) and the mean effective stress ′. The second equation states that the specific volume ν {\displaystyle \ \nu } occupied by unit volume of flowing particles will decrease as the ...
At zero effective stress soil has very little strength and layers of relatively impermeable soil may heave up due to the underlying water pressures. The loss in strength due to upward seepage is a common contributor to levee failures.
Preconsolidation pressure is the maximum effective vertical overburden stress that a particular soil sample has sustained in the past. [1] This quantity is important in geotechnical engineering, particularly for finding the expected settlement of foundations and embankments.