Bishop parameter χ from static equilibrium

Andrzej Niemunis

doi:10.1007/s11440-022-01639-w

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Bishop parameter χ from static equilibrium

2022-09-09

Andrzej Niemunis *

DOI：10.1007/s11440-022-01639-w

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Abstract

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For unsaturated soils, Terzaghi's effective stress sigma = sigma(tot) - u has been generalized by Bishop to the form sigma(B) = sigma(tot) - chi u. Factor chi, for example chi(S) approximate to S, takes into account the degree of saturation S. However, sigma(B) is unable to characterize strength and deformation of soil unless applied with suction. A new stress sigma(E) = sigma(tot) - chi(E)u with chi(E)(S, n) is proposed. It is likewise insufficient if applied without suction, but it has (at least) a clear physical meaning: sigma(E) represents contact forces between grains in the static equilibrium in the same manner as the effective stress does in saturated soils. All grains must be entirely surrounded by free or capillary water.

Keywords:

Air bubbles

Bishop stress

Capillarity

Effective stress

Unsaturated soil