30th GFWA Prize in Geomechanics

Andrew Chilufya, Milan Kukadia, Ming Hui Gao and Neethu Valsaraj

The GFWA Prize in Geomechanics is a prize sponsored by the engineering firm GFWA Pty Ltd and awarded by the Australian Geomechanics Society (AGS) for the best presentation by a final year student in the area of Geomechanics at Universities in Western Australia.

Prizes

Presentations

Two students from The University of Western Australia and two students from Curtin University, each present a short (15-minute max) presentation on their work in geomechanics followed by a brief (5-minute max) question session. The presentations are judged by a selection of experienced industry professionals, with the winner being awarded the 30th Annual Prize in Geomechanics.

Presenters

Andrew Chilufya Curtin University

“Performance Analysis of Road Pavement Stabilised with Biochar”

Abstract

Carbon footprint reduction and the need for sustainability have become areas of increased global significance. Due to the rise in greenhouse gases being emitted, there is a push for a move to more net-zero approaches in the implementation of construction projects. In an attempt to control the rate of climate change, innovations for reducing the carbon footprints associated with traditional methods of road construction are encouraged. One such innovation of sustainable road construction is the use of biochar in conjunction with a chemically modified emulsion for the stabilisation of a road pavement. Biochar is a charcoal-like substance produced in a zero-oxygen environment that is capable of storing carbon in a stable state for decades. The production of biochar converts biomass that would otherwise have decomposed and produced carbon dioxide into a stable carbon state, hence, the carbon sink created from the production of biochar produces a net carbon dioxide reduction.
This research project investigates the performance of laterite road base material stabilised with biochar, including the tensile strength, resilient modulus, flexural stiffness, fatigue life and rutting. Such performance properties are analysed to determine the viability of the use of biochar in pavement construction. The methodology used in evaluating the performance properties will be centred around laboratory testing results against existing chemical stabilisation techniques such as the use of Portland cement. Additionally, this research was able to establish the optimum ratio of biochar to an emulsion that is required to achieve the highest performance. Analysis of the results from the performance properties showed that the use of biochar in pavement stabilisation provides high pavement performance and is competitive and environmentally friendly compared to other traditional stabilisation techniques.

Biography

Andrew Chilufya is a Civil and Construction Engineering student currently in the last year of his bachelor’s degree at Curtin University. Whilst being a student, he participated in a number of extracurricular such as volunteering work with Study Perth and working as a student peer for Curtin. He is currently employed at new world laboratories, where he worked in pavement materials analysis. His role at new world laboratories allowed him to be able to gain a unique understanding of pavement behaviour, geotechnical data analysis and understanding of the various pavement installation techniques. His previous place of employment was at Liquid labs WA where he worked as a geotechnical lab technician and was able to have a hands-on experience in geotechnical laboratory testing. The experience gained from these roles has given him a well-rounded perspective of geotechnical and pavement engineering and provided him with a sense of personal gratification and the ability to work in well-functioning teams.

Outside of his studies, he has a keen interest in web design and photography and also enjoys taking part in some sports such as soccer, golf and tennis in his free time. His career vision is to work in a civil engineering role that provides opportunities to be creative and at times explore innovative alternatives to traditional engineering practices. He also has a keen long-term interest in sharing and encouraging sustainable engineering practices gained from his work and studies.

Milan Kukadia Curtin University

“An Investigation on the Performance of Rutting and Fatigue of Hot Mix Asphalt with the Combination of Hydrated Lime and Fly Ash as Mineral Fillers.”

Abstract

In order to improve material performance, the combination of fly ash with another material in the building industry is becoming increasingly common but there is very minimal research on using fly ash combined with another material in the asphalt industry. Keeping this at the forefront, the aim of this research was to investigate the effects on rutting and fatigue of hot mix asphalt when a combination of fly ash and hydrated lime were added as mineral filler. The combination of fly ash and hydrated lime was added as a percentage of mass of aggregates and a maximum of 1.5% mineral filler was added as per MRWA standards. Fly ash was added in 0.5% increments to a maximum of 1.5% while hydrated lime content was reduced by 0.5% from 1.5% to 0%. The Hamburg Wheel Tracker was used to evaluate the rutting performance of the mixes while the four-point bending test was used to investigate the fatigue properties. AMPT tests were carried out on all mixes to determine the performance of each mixture. Rutting tests showed that the mixture with 0.5% fly ash and 1.0% fly ash gave the lowest rutting depths. Analysis of all other tests is currently ongoing.

Biography

Milan has extensive construction experience in the building industry from Kenya, the country of his birth. During his time as an intern with the British Army in Kenya, Milan was exposed to tough military construction and was first exposed to British Standards. Milan independently led a number of construction projects at their family business in Kenya before travelling across the world to settle in Perth Western Australia in 2016 with his family. He is currently employed as an Undergraduate Engineer at Ertech, looking to develop his experience in the infrastructure sector.

Milan has just completed his Bachelors with Honours in Civil and Construction Engineering from Curtin University. After failing a core unit in the second year of his studies, Milan has worked his way up from a 50% student to achieving a high distinction Semester Weighted Average within only a few semesters. Alongside his studies, Milan has been invited to sit on several advisory committees including the review of the Civil & Construction engineering course at Curtin University as well as faculty consultative committees. Milan was elected to be both the Secretary and Treasurer of the Curtin Civil Engineering Association last year, selected as a Mentor Leader at New to Curtin Mentoring, nominated as Events Team Leader at the Young Builders Alliance and is a key member of the logistics team at the Shree Jalaram Mandal WA. Milan is also a scholar of the John Curtin Leadership Academy and has also won awards such as the Road Engineering Association of Asia & Australia prize for outstanding performance in Traffic and Pavement engineering.

Ming Hui Gao University of Western Australia

“Repurposing Flexible Flowlines as Torpedo Anchors”

Abstract

Flexible pipes are tubes made of corrosion resistant steel cocooned in a leakproof thermoplastic jacket. The pipes are used in oil and gas production, at the end of which, their design and composition make recycling challenging. One idea is to turn the flexible pipes into torpedo anchors for mooring offshore floating renewable devices.

In general, flexible pipes are half as small in diameter and ten times lighter by mass per length than conventional torpedo anchors. Four designs were created: two based on the geometry of torpedo anchors with proven performance (Deep Penetrating Anchor, T-98 torpedo anchor) but scaled to the body of an OD 15-inch flexible pipes. Two novel designs build on DPA and each sport one change unique to the flexible pipe: semicylindrical fins created by cutting a flexible pipe in half lengthwise, and serrations carved into the plastic jacket of the flexible pipe.

The designs were then tested for their efficacy as mooring solutions, particularly to assess how features unique to the flexible pipe would compare with the conventional geometry. Firstly, 3D printed designs were released to freefall through still water in the UWA Large O-Tube to measure the drag coefficient and location accuracy. Favourable performance warranted four designs (DPA, ring finned, serrated, hybrid) to be fabricated in steel, then undergo dynamic installation at 50G to measure the tip embedment and resistance to vertical monotonic loading in preconsolidated kaolin clay. Anchor tip embedment ranged from 1.64 – 2.49 times the anchor length, with the ring finned and hybrid design achieving the deepest embedment. Anchor efficiencies ranged from 2.22 – 2.96, led by the DPA and serrated design in normalised holding capacities. These results provide an initial estimate for the holding capacities generated by a torpedo anchor repurposed from material much lighter and smaller than convention. Moreover, leading performance by the three ringed and hybrid, and comparable performance by the serrated design to the DPA suggest that opportunity exists for these ideas to be developed and for the stockpile of flexible pipes to have their service life extended after decommissioning.

Biography

Ming Hui Gao is a student in the Master of Professional Engineering (Civil) at the University of Western Australia. For her thesis, she is investigating the potential to fabricate torpedo anchors from sections of decommissioned flexible pipes, kilometres of which are likely to be retrieved from Australian oceans over the next thirty years with no further use on land. As a proof of concept, her research has focused on creating several designs of torpedo anchors from the specifications of the flexible pipes, then testing those designs to measure their hydrodynamic and geotechnical performance.

Neethu Valsaraj University of Western Australia

“Evaluating the influence of constitutive model inputs on soil behaviour: a parametric study”

Abstract

The structural stability of tailings storage facilities is largely governed by the material properties of the mine waste residue (i.e., tailings) that they contain. Understanding and quantifying the behaviour of tailings in terms of strength, stiffness, compressibility, state parameter is essential for the proper management of the TSFs. Tailings samples collected from site provide information about the tailings collected from that singular location, but there is wide variability on terms of strength, stiffness, compressibility, state parameter of the tailings throughout the impoundment.
Starting from the element testing lab data, the tailings behaviour can be modelled using finite element analyses. A number of commercially available software packages that incorporate soil constitutive models can be used to virtually simulate the lab data.

The current thesis is using the Plaxis 2D software and a number of constitutive models to both replicate the lab data (i.e., calibration) and to investigate the effect of varying elastic moduli, initial void ratio, confining stresses and strength parameters on the behaviour of tailings. The student also investigated the differences in tailings behaviour resulted from comparing Plaxis results to FLAC 3D analyses (performed by a different research student).

The effect of varying soil parameters was quantified and presented in the form of p’-q, q –εa and e – log(p’) curves. The effect of each changing parameter was then interpreted and where available, compared to available litdrature.
Differences were observed at the baseline calibration between Plaxis 2D and FLAC 3D in the implementation of these constitutive models. Hence, a comparison is made with the parametric study done on FLAC software with similar parameters for evaluating the differences between the two software.

Biography

Neethu Valsaraj is a final year student in Master of Professional Engineering (Civil Engineering specialization) at the University of Western Australia. As a part of her final year thesis, she is conducting a parametric study using Plaxis 2D for evaluating the influence of constitutive model inputs on soil behaviour. Her research mainly focuses on Mohr-Coulomb, Modified Cam Clay, and Nor Sand soil models. Recently, she joined WSP- Golder as a tailing engineer.

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