Improving The Characteristic of Collapsible Soil Using Pumice
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Date
2022
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Addis Ababa University
Abstract
Collapsible soils, which are sometimes referred to as metastable soils, are unsaturated soils that
undergo a large change in volume upon saturation with or without loading which pose problem
to civil engineering structure. Many researches have been done and variety of methods and
techniques have been proposed for improving the engineering property of this soil to make
suitable for civil engineering structure built on it. Some techniques used for improving
collapsible soils are partial excavation and replacement with compacted fill, dynamic compaction
and chemical stabilization. Alternatively, use of other local abundant available pumice material
as a means improving is one method which reduce damages on structure.
This study was undertaken on collapsible soil sample taken from Ziway-Adamitulu Woreda. The
change in engineering properties of this soil investigated with addition of increasing percentage
of pumice. Pumice is the most locally abundant available material around the aforementioned
area. The preliminary investigation of the soil to be improved initially characterized and
classified based on indicative tests and found to be A-4 according to AASHTO and SM class of
soil according to USCS systems. Compaction, direct shear, CBR and collapsible potential tests
were used to evaluate engineering properties the improved soil. Field density tests also
conducted to determine the in-situ densities of the soil.
Analysis of the results shows that the collapse index of natural and compacted untreated soil
6.720% with moderate severe disorder soil at bulk and 2.235% with moderate disorder soil at
OMC respectively. Treating this soil with pumice reduce collapsible index from moderate
disorder soil (2.235%) to slight disorder soil (0.329) % at optimum content of 25 % pumice
according to ASTM D5333. Similarly, MDD decrease and CBR, Shear strength and OMC values
increased as pumice content is increased. Curing has significant effect on the geotechnical
properties of pumice-stabilized soil. Therefore, this experimental result contributes in solving the
problems of soil collapse by treating to enhance its resistance.
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Keywords
Collapsible Soil, Pumice, unsaturated soils