AGS NSW Research Award 2016
for Research in Geotechnical Engineering or Engineering Geology Presentations
Danielle Griffani, Lam Dinh Nguyen and Sinniah Navaratnarajah
As part of the ongoing support of academic institutions and students, the Sydney Chapter of the Australian Geomechanics Society is offering the prestigious AGS NSW Research Award for research in Geotechnical Engineering or Engineering Geology.
The award aims to provide a forum for research students from NSW universities to showcase their research to the wider Geotechnical Community. Abstracts for the presentations can be viewed below.
This year three (3) research award finalists have been chosen to provide their presentations to the wider geotechnical community and they are:
Lam Dinh Nguyen
Establishing a practical framework to predict heat and contaminant transfers in fractured geological media
When it comes to predicting the transfer of heat or spread of contaminants through fractured geological media, how much information about the soil and rock microstructure do we need? How do the physical properties of the fractures influence the rate of transfers and which matter the most? Can they be measured practicably?
By considering such questions and the results of recent numerical and analytical findings, this talk will introduce a general framework to predict the rate of transfers in fractured geological media. This framework may potentially aid the assessment of groundwater contamination risks as well as inform the design of improved processes such as geothermal heat recovery techniques.
Lam Dinh Nguyen
Developing constitutive model to simulate behavior of cement treated clay composite capturing effect of cementation degradation
Stabilising soft clays with cement has become an effective ground modification method to improve the properties of the soft soils. However, a typical stress-strain relationship shows brittle failure behaviour of the soil treated with cement where the shear strength decreases rapidly after the peak strength state. Hence, in recent years, the inclusion of fibre into soil treated with cement has become increasingly popular to overcome the challenge of the unfavourable brittle behaviour of the cement treated soil. In this study, a constitutive model was developed to simulate the behaviour of cement treated clay with fibre reinforcement. The proposed model includes the formulation of the modified mean effective stress considering the effect of cement and fibre inclusion, together with the cementation degradation and fibre failure due to volumetric and shear deformation. The performance of the proposed model was evaluated by comparing the model predictions with the undrained triaxial test results conducted on natural clay treated with cement and fibre. The laboratory results indicated that the combined effects of cementation and fibre reinforcement increase the shear strength and ductility of the treated soft clay. By capturing the main features of the cement treated clay with fibre reinforcement, the proposed model provides reliable predictions that agree well with the experimental results.
Energy absorbing synthetic mats to enhance the stability of ballasted railways subjected to cyclic load
The rail transportation system in Australia plays a significant role in the conveyance of bulk freight and passengers. Increasing demand for high speed rail and fast heavy haul poses a serious challenge for stability of tracks on problematic ground. Ballast is a key foundation material placed underneath the sleepers which provides structural support against high cyclic and impact stresses imparted by moving trains. Degradation of ballast contributes to a large percentage of maintenance costs, apart from affecting the longevity and stability of track. In recent years, use of synthetic soft pads in track foundation has become increasingly popular as means of reducing track damage. A synthetic mat placed under a sleeper is traditionally called as Under Sleeper Pad (USP), and when it is placed under ballast, the term Under Ballast Mat (UBM) is often used. Currently there is lack of comprehensive assessment on the geotechnical behaviour of ballast using these artificial inclusions under cyclic loading. In this study, a series of large-scale laboratory tests were carried out to verify the performance of ballasted track and understand the use of energy absorbing synthetic mats in the attenuation of cyclic stresses and subsequent mitigation of ballast degradation. The synthetic mats can be manufactured from recycled waste rubber tyres which reduce the amount of waste tyres sent to spoil tips and contributing to effective land use especially in expensive urban suburbs of major cities. Cyclic loads were simulated using a large-scale process simulation prismoidal triaxial apparatus (PSPTA). This research presents a state-of-the-art review of laboratory and numerical studies that demonstrate the benefits of USPs and UBMs for the rail industry.
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