Measurement of Ground Deformations during Geohazards using Magnetic Trackers

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dc.contributor.advisor Orense, RP en
dc.contributor.advisor Wotherspoon, L en
dc.contributor.author Chen, Xiaoyu en
dc.date.accessioned 2020-05-21T00:13:00Z en
dc.date.issued 2020 en
dc.identifier.uri http://hdl.handle.net/2292/50757 en
dc.description.abstract Engineering behaviour of earth materials is one of the major preoccupations in geotechnical engineering. Kinematic of earth materials describes the particle and body motions using kinematic quantities including displacement, velocity and acceleration. They are considered to be the key parameters in the monitoring and analysis of the complicated behaviour of earth materials. Capturing those kinematic quantities have been conducted by researchers and practitioners in both laboratory and field applications. Nowadays, electronic devices are developed into sophisticated equipment to detect the motions of objects. For example, magnets have been used to track movements within the human body for medical applications. The principle of magnetic tracking is translated to the geotechnical environment in this thesis, with necessary alterations and improvements, for acquiring the kinematic quantities of soil under geotechnical processes. Development details are shown in this thesis using permanent magnets as tracker and magnetometers as receiver. To ensure the effectiveness when used for geotechnical related purposes, validations of the tracking system are performed, including the evaluation of the influence on tracking accuracy due to the presence of soil, performance of capturing cyclic motions and multi-object tracking. Small-scale laboratory experiments, making use of the proposed tracking system, are conducted to investigate the mechanism of the downslope motions of rigid blocks. Laboratory experiments, such as flume tests, play a very important role in investigating the involved mechanism since they provide idealised conditions in which each parameter of interest can be studied accordingly. The experiment consists of releasing dry rigid blocks on an inclined chute. The blocks are made of mortar, in which one of them is implanted with a permanent magnet inside as a tracker. By detecting the magnetic flux density generated by the permanent magnet, time histories of positions and orientations of the tracker block can be calculated and thereafter used in a kinematic analysis to quantify the dynamic behaviour of the tracker within the moving mass; those kinematic quantities considered include the linear and angular displacements, velocities and accelerations, and also kinetic energy and frequency of collision. Observations obtained from the magnetic tracking system highlight the influence of the initial volume on runout distance from the analysis of the distributions of tracker’s velocity and acceleration. The movement of the block is divided into two phases based on the distributions of translational kinetic energy. Results show that larger volume increases the runout, and the influence of volume becomes more prominent when the particles enter the deposit area. The proposed magnetic tracking system is proved to have great potential in geotechnical physical modelling to bring a new perspective in understanding the downslope motions of granular materials. Finally, the potential field applications of the magnetic tracking system are discussed, including a recommendation on the optimised number and geometry of the magnetometer array and the corresponding strength of the magnetic tracker. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ en
dc.title Measurement of Ground Deformations during Geohazards using Magnetic Trackers en
dc.type Thesis en
thesis.degree.discipline Civil and Environmental Engineering en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Doctoral en
thesis.degree.name PhD en
dc.rights.holder Copyright: The author en
dc.rights.accessrights http://purl.org/eprint/accessRights/OpenAccess en
pubs.elements-id 802191 en
pubs.record-created-at-source-date 2020-05-21 en


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