Study the Physical Characteristics and Severity to Collapse of Collapsible Soils: A Case of Turmi – Omo Road Project
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Date
2019-11
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Addis Ababa University
Abstract
Collapsible soils present significant geotechnical and structural engineering challenges for
different types of constructions. These soils suffer volume changes and collapse deformation
upon wetting. Situations in arid and semi-arid climates favor the formation of the most
problematic collapsible soils. Almost all naturally occurring collapsible soil deposits are debris
flows, rapid alluvial depositions, and wind-blown deposits (loess). If unrecognized, it may cause
pumps or deep sinkholes, which leads to traffic accidents and loss of lives. Hence, this research
was conducted to investigate the physical properties and the severity of collapse of the soils
found in the road project of Turmi - Omo.
To achieve the objective of this research, papers, journals, actual design reports, contract
document of the project and different books have been scrutinized under literature review,
samples from the research area were collected from different test pits below the natural ground
level, and then laboratory tests for index properties and oedometer tests have been carried out
using disturbed and remolded samples.
From the test results the subgrade soil classes fall in A-4, A-6 and A-7-6 according to AASHTO
classification. In addition, according to USCS the soils under investigation are classified as ML
(group of inorganic silt of medium compressibility). The evaluation of susceptibility of soil to
collapse was measured by performing single oedometer tests on samples remolded at their in-situ
densities and at maximum dry densities.
The oedometer test results at the investigated depth of soil showed that, the collapse potential of
samples remolded at their in-situ densities and natural moisture contents is within the range of
1.49 % to 5.93 % and that indicates that the severity of collapse is slight to moderate. And also,
the collapse potential of samples remolded at their maximum dry densities and optimum
moisture contents is within the range of 0.19 % to 0.495 % and thus the severity of collapse is
very slight. Though the results indicated that the severity to collapse is very slight, the soil in the
investigated section is collapsible and the collapse potential could be significantly reduced by
compaction during construction.
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Keywords
Turmi – Omo Road Project, Physical Characteristics, Collapsible Soils, Severity