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Earth Pressures of Overconsolidated Collapsible Soil Subjected to Inundation

Title:

Earth Pressures of Overconsolidated Collapsible Soil Subjected to Inundation

Nguyen, Phuoc Huy Nhut (2018) Earth Pressures of Overconsolidated Collapsible Soil Subjected to Inundation. PhD thesis, Concordia University.

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Abstract

Collapsible soils are known as problematic soils, which can be found in many regions around the world. Collapsible soils possess considerable strength when they are dry; however, when they are inundated, they lose their strength and exhibit excessive settlement. The amount of soil collapse increases with the increase of the so-called collapse potential “Cp”, the wetting zone, and the degree of saturation (S). Accordingly, maximum collapse will take place due to full saturation. Collapsible soils can be inundated by heavy and continuous rainfall, excessive irrigation, broken water/sewer lines, or by rising the ground water. Furthermore, collapsible soils can be also found in construction site, in compacted fine soils at low water content (less than the optimum water content). Consequently, it is impossible to avoid construction on collapsible soils, which are potential for excessive settlement, differential settlement, landslides and falls, earth cracks. This type of soil has been responsible for damaging variety of civil engineering structures, loss of lives. Construction on such kind of soil shows extraordinary geotechnical problems, retaining walls are not an exception. With civilization, backfills behind retaining walls made of collapsible soils are widely used in practice. The earth pressures acting on these walls experience radical changes when the backfills of collapsible soils are wetted.
In the literature, there are lack of theories/methods for estimating the earth pressures acting on walls retaining collapsible soils. In this study, experimental investigations on at-rest and passive earth pressures of overconsolidated collapsible soil on retaining walls were conducted.A prototype model of a vertical wall, retaining horizontal backfill of collapsible soil, was developed in the laboratory. Collapsible soil was prepared in the laboratory by mixing kaolin clay with fine sand. The model was instrumented to measure the earth pressure at strategic points on the wall, the total earth pressure acting on the wall, and the overconsolidation ratio (OCR) of the soil. Tests were conducted on the wall retaining collapsible soil at the dry and at fully saturated conditions for both the at-rest and passive earth pressures. The test results showed that both the at-rest and passive earth pressures increased with the increase of the collapse potential (Cp) and overconsolidation ratio (OCR) for the dry soil. At full saturation, the at-rest and passive earth pressures reduced considerably. Generally, the higher the collapse potential of the collapsible soil, the larger the decrease in the at-rest and passive earth pressures of the soil when the soil gets inundated.
In this investigation, for the case of at-rest earth pressure, empirical formulae were developed to determine the coefficient of at-rest earth pressure (K0) of the dry and saturated overconsolidated collapsible soil. For the case of passive earth pressure, analytical model was developed. Accordingly, design theory was presented for estimating the coefficient of passive earth pressure (Kp) of overconsolidated collapsible soil at the dry and saturated conditions. Moreover, considering for the case of presence of unsaturated states of collapsible soil in practice, design charts were developed to assist designers in approximating the coefficient of at-rest (K0) and passive (Kp) earth pressures of this soil at different degree of saturation.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Building, Civil and Environmental Engineering
Item Type:Thesis (PhD)
Authors:Nguyen, Phuoc Huy Nhut
Institution:Concordia University
Degree Name:Ph. D.
Program:Civil Engineering
Date:February 2018
Thesis Supervisor(s):Hanna, Adel
ID Code:983914
Deposited By: Phuoc Huy Nhut Nguyen
Deposited On:05 Jun 2018 13:56
Last Modified:05 Jun 2018 13:56

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