Title

Permeability characteristics of fibre-reinforced Perth sandy soil

Author Identifiers

Amal Dortaj
ORCID: 0000-0002-6574-9149

Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Engineering Science

School

School of Engineering

First Advisor

Associate Professor Sanjay Kumar Shukla

Second Advisor

Associate Professor Mehdi Khiadani

Field of Research Code

090501

Abstract

Fibres are mixed with soils to enhance their strength and hydraulic characteristics. Fibre-mixed soils are often known as the fibre-reinforced soils. In the past, both systematically and randomly reinforced soils have been used widely in civil and geotechnical structures. Randomly reinforced-soils using fibres exhibit advantages over systematically reinforced-soils because systematic reinforcements may result in weak planes within the soil mass. Randomly distributed reinforcements are also easier to apply and maintain for some applications.

Previous researchers have studied the strength, compaction and compressibility behaviour of fibre-reinforced soil. Study on characteristics of fibre-reinforced soils when saturated, however, is limited to piping resistance improvement. One of the main reasons for collapse of some of the hydraulic structures is soil piping that takes place on the downstream side as a result of upward seepage. Fibre-reinforced soils can be a solution in sustainable watershed management as they can be used in irrigation and drainage projects, such as river levees, contour bunds, temporary canal diversion works, temporary check dams, soil structures, stream restoration, etc., for seepage and permeability control.

This study focuses on permeability characteristics of fibre-reinforced soil. Permeability characteristics can vary depending on soil, fibre and methods used. Materials used in this study are Perth sandy soil, and locally available jute and waste tyre fibres. These materials were chosen because they are abundantly available in Perth area and surroundings. As for the waste tyre fibre, it was also chosen as a green approach to use waste materials in structures and solve their disposal problems. Fibre content varied from 0 to 10% with 1% intervals for tyre fibres and from 0 to 1.5% with 0.25% intervals for jute fibres. Fibre length varied from 5 to 25 mm with 5 mm intervals for jute fibres. Fibre length was constant in all experiments for tyre fibres as they come in a mixture of different lengths and studying the effect of length of permeability characteristics was not possible. Experimental tests were conducted on fibre-reinforced specimens in a constant-head permeameter. Experimental results suggest that the coefficient of permeability increases with an increase in fibre content for both fibre types (up to 100% for jute fibres and up to about 40% for tyre fibres). Also, it is observed that the coefficient of permeability increases with an increase in fibre length for jute fibres, as a general trend. As expected, water content increases and dry and saturated unit weights decrease with inclusion of higher fibre contents and longer fibres as a general trend.

Fibre-reinforced soil specimens and the water discharge were modelled numerically using the commercial software SEEP/W in order to study the effects of fibre inclusion on permeability characteristics. The findings from the developed numerical model agree well with the experimental observations.

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