Current projects

• Lifting objects off seabed

  PhD student

  Mason (Sen) Mei

  Supervisors

  Assoc Prof Yinghui Tian, Prof Mark Cassidy

  Most of us have experienced the difficulty of lifting our shoes up from muddy ground (the quintessential ‘stuck in the mud’). This tells us that uplifting an object off the seabed requires much greater than its own submerged weight. This is termed as breakout phenomenon. The most significant component of the resistance force emanates from the ‘suction’ generated. During uplifting the ‘suction’ will dissipate and an abrupt and significant reduction in uplift resistance may occur.

  The research aims to improve the understanding of breakout process to enable offshore engineering operations, where a wide variety of applications, such as decommissioning of offshore infrastructures and securing offshore foundations, would require the knowledge of this problem.

• Behaviour of embedded anchor chains

  PhD student

  Wenlong Liu

  Supervisors

  Assoc Prof Yinghui Tian, Prof Mark Cassidy

  Offshore floating facilities are required to be secured through a mooring system, which comprises anchors and mooring lines. The segment of the mooring line, predominately using metallic chain, is embedded in the soil to connect the embedded anchor and takes a reversed catenary shape. The friction capacity of the anchor line itself can take up a major component of the overall anchor capacity. The bearing capacity of embedded anchors is controlled by the chain inclination and depth at the padeye. Most of existing research and current design practices consider the anchor line profile in a two-dimensional vertical plane. The friction and normal soil resistance to the anchor chain are not coupled in the existing analytical design method of embedded anchor line.

  The aim of this research is to gain in-depth knowledge about the soil resistance to the chain links and advance the fundamental understanding of three-dimensional performance of the embedded anchor line. This research mainly uses numerical simulation method to investigate the bearing capacity and combined yield surface of the chain link. A new numerical approach based on a force-resultant macroelement plasticity model will be developed to implement three-dimensional analysis of the anchor line.

• Securing submerged floating tunnels

  PhD student

  Wei Lin

  Supervisors

  Assoc Prof Yinghui Tian, Prof Mark Cassidy

  A submerged floating tunnel is a conceptual design of a tunnel that floats in water, supported by its buoyancy (specifically, by employing the hydrostatic thrust, or Archimedes' principle). Although the idea can be stemmed back to the late 19th century, none submerged floating tunnel has been built yet. One of the key barriers for this promising new infrastructure is how the tunnel can be securely moored to the seabed. This project aims to provide an efficient geotechnical solution through a loop of conceptual development, numerical modeling, centrifuge modelling and final verification using large scale model tests. Expected outcomes include a rigorously verified mooring system, quality first-hand observations and scientific knowledge advance, which are expected to pave the way for constructing the first submerged floating tunnel.

• Cyclic capacity of horizontal plate anchors in sand

  PhD student

  Rene Kurniadi

  Supervisors

  Dr Shiaohuey Chow, Prof Mark Cassidy, Dr Anamitra Roy (co-supervisor)

  The emergence of offshore floating renewable energy devices requires economic anchor solutions for sand. Plate anchors could represent such a solution due to their high efficiency in resisting tensile uplift loading. The monotonic capacity of plate anchors is relatively well investigated in sand. However their performance under realistic and long term offshore environmental or cyclic loading is not well understood. This project aims to investigate the performance of horizontal plate anchors under cyclic loading in sand. The project will involve numerical modelling using advanced constitutive model and model anchor tests using state-of-the-art centrifuge modelling. The outcomes of the project will be integrated into an accessible design tool to enable better predictability of the anchor cyclic capacity in practice.

• Effect of partial drainage on plate anchor capacity in sand

  PhD student

  Zhenyu Liu

  Supervisors

  Dr Shiaohuey Chow (The University of Melbourne), Assistant Professor, Dr Mason Ghafghazi (University of Toronto), Associate Professor Yinghui Tian (University of Melbourne)

  Plate anchors could be a cost-effective solution for mooring offshore renewable energy devices, although their response to realistic loading under offshore conditions still requires a more robust understanding, particularly under partially drained conditions imposed by rapid loading rates (e.g. under severe storm condition). Partial drainage (or the worst case scenario of undrained condition) occurs when the water in the porous sand skeleton is unable to drain away upon loading, resulting in a rapid increase of pore water pressure or generation of excess pore water pressures. The reduced drainage has a significant effect on the sand strength, which, in turn, affects the capacity of plate anchors. To date, there is limited numerical capability in simulating partially drained capacity of plate anchors in sand. This joint University of Melbourne (UoM) – University of Toronto (UoT) project aims to investigate effect of partial drainage on plate anchor capacity in sand using numerical and experimental approaches. The outcomes of the project will be integrated into an accessible design tool to enable better predictability of anchors capacity under partial drainage in sand in engineering practice.

• Assessment of offshore geo-hazard and failure prediction using AI-ML

  PhD student

  Farid Fazel Mojtahedi

  Supervisors

  Dr Negin Yousefpour, Dr Shiaohuey Chow, Professor Mark Cassidy

  Offshore systems and subsea infrastructures are vulnerable to different natural geo-hazards, including turbidity currents, submarine landslides (and events that trigger tsunami), scour (seabed sediment mobility), and fluid flow. Such geo-hazards are the features that are commonly found in deep-marine settings. It is essential to early characterize, predict, and assess the risk and impacts of geo-hazards, particularly in deep remote fields, for operation maintenance of these systems and minimizing the failure, damage, and environmental risks. Assessment of geo-hazards is traditionally based on site investigation data that are exposed to considerable uncertainties for such factors as variable ground and water (current) conditions, dynamic nature of seafloor condition, lack of resolution, and gaps in survey data. Our understanding of Mass-transport complexes (MTCs) in the submarine and offshore environments have been improved nowadays as a result of emerging technologies. Nevertheless, there are still uncertainties about the way of evolution of the flow and volume behavior of MTCs during their translation, the factors controlling these changes, the relationship with their internal geometry and architecture, and the implications of MTC emplacement processes for the assessment of geo-hazard risk in sedimentary basins. Innovative predictive modelling and probabilistic approaches allow maximizing the interpretations, decreasing the required frequency of seafloor data acquisitions, and capturing the uncertainties. The purpose of the current research is providing innovative solutions for better understanding the offshore geo-hazards triggers and signs and assessing the risk of future geo-hazard events according to real-time, dynamic data obtained from the seafloor.

• Development of a Soil-Specific CPT Interpretation Method for Partially Drained Penetration

  PhD student

  Xingyi Wu

  Supervisors

  Assistant Professor, Dr Mason Ghafghazi (University of Toronto), Associate Professor Yinghui Tian (University of Melbourne), Dr Shiaohuey Chow (The University of Melbourne)

  The Cone Penetration Test (CPT) is a predominant site characterization tool since it provides a wealth of information on soils (e.g. pore water pressure, bearing capacity, and so on) with the fast and inexpensive application. The cone penetration process has a complicated interaction with the pore water in soils because of the generation of excess pore water pressures due to the penetration. This makes interpretation of CPT results particularly challenging. The joint research topic focuses on producing soil-specific CPT interpretation methods by accounting for the complicated nature of the soil, and the interaction of soil, water and the advancing cone. This project will involve the numerical modelling of the interaction between the cone and the soil during the penetration by employing the advanced soil constitutive model under different drainage conditions. The results from the numerical modelling will be used to propose a new interpretation method of CPT results. The outcome of this project will assist engineers to get more precise soil properties from CPT results.