Relationship Between Consolidation and Swelling Characteristics of Expansive Soils of Addis Ababa

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Date

2005-03

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Addis Ababa University

Abstract

Clay soils are usually subjected to a time dependant strain under load. This strain is mainly a function of the rate of pore water pressure dissipation which in turn depends on the permeability of the soil mass. Therefore, consolidation is a term used to describe the volume change of the soil mass due to pore water pressure dissipation. Among the clay soils in the world, expansive soils have a special mineralogical characteristic which leads to swelling when exposed to moisture change. This behavior is due to the presence of considerable amount of montmorillonite clay mineral. As a result of swelling, pressure is exerted by the soil on the structures built on it and causes an increase in volume of the soil mass which also lifts the structure. Consequently, cracking of buildings, breaking of pavements, damaging of utility pipes are common problems on structures built on such soils. But under the action of heavy loads, greater than the swelling pressure, the soil undergoes consolidation. Thus, this paper is mainly intended to evaluate the swelling and consolidation behavior of expansive soils of Addis Ababa and their interdependence using one dimensional consolidation theory of Terzaghi. In the course of the research work consolidation-swell test was carried out on a number of samples of expansive soil obtained from different parts of Addis Ababa. The swelling and consolidation characteristic of the soil is determined from the laboratory tests. Ranges of values of the consolidation parameters are also obtained. The swelling behavior is found to influence the consolidation characteristics of expansive soils.

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Keywords

Expansive ;Soils

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