ORCID Profile
0000-0002-3903-1125
Current Organisation
Western Sydney University
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Civil Engineering | Civil Geotechnical Engineering |
Civil Construction Design | Environmentally Sustainable Construction not elsewhere classified
Publisher: Thomas Telford Ltd.
Date: 09-2016
Abstract: This paper reports on a series of centrifuge model tests investigating the effect of shape on the penetration resistance of spudcan and conical footings on sand overlying clay. The effect of footing shape and geometry on single-layer soil has been studied intensely. However, there is still limited understanding for conical footings on sand over clay. In the present study, digital images were captured during penetration of various shapes of half-footing held against a transparent window of a strongbox. The images were then analysed using particle image velocimetry techniques. Experimental evidence has shown that, irrespective of the conical angle of the underside within the range of 7–21°, when the footing penetrates through sand into an underlying clay layer: (a) accumulated radial and deviatoric shear strains along the future failure surface counteract each other, resulting in similar peak resistance in the sand layer and (b) a trapped sand plug of constant height is pushed into the underlying clay layer. These observations serve to justify the previously proposed methods for predicting the full penetration resistance profile on sand overlying clay, which is required to predict the potential for, and severity of, punch-through failure.
Publisher: Thomas Telford Ltd.
Date: 09-2015
Abstract: Spudcans are the traditional footings used for offshore mobile jack-up rigs. However, the installation of spudcans in sand overlying clay may lead to punch-through failure, which can cause serious damage to the jack-up rig and endanger personnel. This article compares three new methods proposed in the literature and an interpretation of the International Organization for Standardization (ISO) guideline for predicting the full penetration resistance profile. The penetration resistance profile for each of the methods is characterised by two key calculations: the peak resistance in the sand and the bearing capacity within the underlying clay. The punch-through distance – an indicator of the potential for and severity of punch-through failure – is estimated from these calculations. In comparison with 71 geotechnical centrifuge tests, the ISO guideline provides poor predictions, consistently underestimating the peak resistance in the sand and the underlying bearing capacity in the clay. Although all three of the new methods provide a superior response, by assessing the accuracy, scatter and geometric skew of the predictions, two of the methods are shown to be biased in at least one of the key calculations used to define the penetration resistance profile, thus producing bias in the prediction of the punch-through distance. However, one method yields largely unbiased predictions.
Publisher: Springer International Publishing
Date: 2021
Publisher: Thomas Telford Ltd.
Date: 03-2017
Abstract: During offshore operations, the spudcan footings of mobile jack-ups are subjected to combined vertical, horizontal and moment (V, H, M) loading as a result of environmental wind, wave and currents acting on the platform. In seabeds of single-layer clay or sand it is now common to express spudcan capacity directly as a surface of allowable VHM loads. Although layered soil stratigraphies with sand overlying clay are encountered in the field, the effect of soil layering on the VHM surface is not well understood. Defining the VHM capacity of a spudcan when it has pushed a layer of sand into the underlying clay is the concern of this paper. Results from a series of centrifuge tests demonstrate that the general framework used in single layers is equally applicable in layered soils. Increases in vertical and moment capacity, compared with clay only soil, are similar in magnitude and arise from the sand plug being pushed into the clay layer by the penetrating spudcan. The most significant increase, however, was found in the horizontal capacity.
Publisher: Thomas Telford Ltd.
Date: 05-2020
Abstract: Spudcan punch-through in layered seabed sediments is one of the major concerns for the jack-up industry. This paper reports the results from a series of centrifuge model tests undertaken to assess the effect of various shapes of spudcan base at mitigating punch-through in sand-over-clay deposits. The experimental programme was carried out in a drum centrifuge by varying the spudcan base profile, skirt length on the periphery and number of holes through the spudcan. The large testing area of one soil s le prepared along the full drum channel enabled an extensive number of 13 spudcan penetration tests under consistent soil conditions. Additional large-deformation finite-element analyses were carried out to explore the soil failure mechanisms around each spudcan with different shapes. The spudcan base profile and number of holes through the spudcan showed no apparent influence on the spudcan penetration behaviours, as the sand blocked the spudcan holes during penetration. Only the skirt showed a positive influence at mitigating punch-through. The positive influence was greater with a longer skirt.
Publisher: Elsevier BV
Date: 07-2021
Publisher: Springer Science and Business Media LLC
Date: 25-01-2016
Publisher: Canadian Science Publishing
Date: 10-2014
Abstract: Assessment of the risk of punch-through failure of spudcan foundations on sand overlying clay requires prediction of the full penetration resistance profile, from touchdown and through punch-through to equilibrium of the vertical resistance at depth in the underlying clay layer. This study uses the Coupled Eulerian–Lagrangian approach, a large deformation finite element analysis method, to model the complete penetration resistance profile of a spudcan on sand overlying clay. The sand is modeled using the Mohr–Coulomb model, while the clay is modeled using a modified Tresca model to account for strain softening. The numerical method is then used to simulate a series of spudcan penetration tests, performed in a geotechnical centrifuge, on medium dense sand overlying clay. The punch-through behavior observed in the experiments is replicated, and the penetration resistance profiles from numerical analyses are generally a reasonable match to the experimental measurements. The influences of the sand layer height to foundation diameter ratio, sand–clay interface shear strength, and strength gradient in clay on the penetration resistance profiles are explored in a complementary parametric study. The penetration resistance in the underlying clay layer is well predicted using a simple linear expression for the bearing capacity factor for the spudcan and underlying sand plug. This expression is combined with an existing failure stress dependent model for predicting peak resistance to form a simplified method for prediction of the full penetration resistance profile. This new method provides estimates of the vertical penetration that the spudcan will run during the punch-through event. It is validated against both medium dense and dense sand centrifuge tests.
Publisher: American Society of Civil Engineers
Date: 06-2017
Publisher: Elsevier BV
Date: 10-2022
Publisher: American Society of Mechanical Engineers
Date: 09-06-2013
Abstract: This paper, a product of an intensive eight-week Lloyd’s Register Educational Trust (LRET) Collegium held during July – September 2012 in South ton, UK, presents an innovative engineering system concept design for manganese nodule recovery. Issues associated with environmental impacts, such as insufficient or lack of transparent impact studies of any potential full-scale seabed mining, are identified as the key obstacles which could lead to public protest, thus prevent the mining project from taking place. Hence, the proposed system introduces an environmentally friendly solution with the innovative concept of a black box, which performs in-situ nodule-sediment separation and waste discharge, and allows recirculation of waste water. The use of a modularised mining system with small, active hydraulic, crawler-type collectors is proposed to minimise environmental footprint and increase system redundancy. This yields a comparable estimated sediment-to-dry nodule ratio with previous studies in sediment plume impact assessment. The proposed system is a big leap towards a more environmentally friendly solution for achieving (the first) full-scale manganese nodule recovery. Together with the intended small production scale of 0.5 millions dry nodules per year, the proposed system can also be considered as a full-scale experiment or field measurement: a platform for full-scale research concurrently, particularly in the area of environmental impacts. The proposed system, intended to spur more interest in environmental impact studies and to be more transparent to the public, could benefit both industry and research institutes, for the benefit of everybody.
Publisher: MDPI AG
Date: 02-08-2021
DOI: 10.3390/APP11157131
Abstract: Integral bridges are a class of bridges with integral or semi-integral abutments, designed without expansion joints in the bridge deck of the superstructure. The significance of an integral bridge design is that it avoids durability and recurring maintenance issues with bridge joints, and maybe bearings, which are prevalent in traditional bridges. Integral bridges are less costly to construct. They require less maintenance and therefore cause less traffic disruptions that incur socio-economic costs. As a consequence, integral bridges are becoming the first choice of bridge design for short-to-medium length bridges in many countries, including the UK, USA, Europe, Australia, New Zealand and many other Asian countries. However, integral bridge designs are not without challenges: issues that concern concrete creep, shrinkage, temperature effects, bridge skew, structural constraints, as well as soil–structure interactions are lified in integral bridges. The increased cyclic soil–structure interactions between the bridge structure and soil will lead to adverse soil ratcheting and settlement bump at the bridge approach. If movements from bridge superstructures were also transferred to pile-supported substructures, there is a risk that the pile–soil interactions may lead to pile fatigue failure. These issues complicate the geotechnical aspects of integral bridges. The aim of this paper is to present a comprehensive review of current geotechnical design practices and the amelioration of soil–structure interactions of integral bridges.
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2023
Publisher: MDPI AG
Date: 20-10-2022
DOI: 10.3390/JMSE10101551
Abstract: A floating oscillating water column (OWC) wave energy converter (WEC) supported by mooring lines can be modelled as an elastically supported OWC. The main objective of this paper is to investigate the effects of the frequency ratio on the performance of floating OWC (oscillating water column) devices that oscillate either vertically or horizontally at two different mass ratios (m = 2 and 3) through two-dimensional computational fluid dynamics simulations. The frequency ratio is the ratio of the natural frequency of the system to the wave frequency. Simulations are conducted for nine frequency ratios in the range between 1 and 10. The hydrodynamic efficiency achieves its maximum at the smallest frequency ratio of 1 if the OWC oscillates horizontally and at the largest frequency ratio of 10 if the OWC oscillates vertically. The frequency ratio affects the hydraulic efficiency of the vertical oscillating OWC significantly stronger than that of the horizontal oscillating OWC, especially when it is small. The air pressure and the volume oscillation in OWC is not affected much by the horizontal motion of the OWC but is significantly affected by the vertical motion, especially at small frequency ratios.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Society of Civil Engineers (ASCE)
Date: 02-2014
Publisher: International Society of Offshore and Polar Engineers
Date: 12-2020
Publisher: Thomas Telford Ltd.
Date: 11-2015
Abstract: A complete analytical method to describe the full load-penetration resistance profile of a mobile jack-up spudcan footing penetrating a sand over clay stratigraphy is described. It is based on both large deformation finite-element analyses and geotechnical centrifuge experiments. The coupled Eulerian–Lagrangian (CEL) approach is used to accommodate the large deformations of a spudcan footing penetrating sand overlying clay. Modified Mohr–Coulomb and Tresca models describe the sand and clay behaviour, with modifications accounting for the effects of strain softening on the response of the soil. The CEL results are shown to match centrifuge tests well, allowing the numerical study to be extended parametrically, and with confidence, to cover the range of layer geometries, sand relative densities and footing shapes that are of practical interest to offshore jack-ups. The results are used to (a) assess the performance of an existing model to predict the peak resistance in the sand layer (extending its range of application to medium dense to dense sands and to conical footings of angle 0° to 21°), and (b) develop an expression for the bearing capacity factor when the footing penetrates into the underlying clay. Using the analytical formulas proposed, retrospective simulations of centrifuge tests show that the method provides a reasonable estimate of the peak punch-through load, the behaviour in the underlying clay, as well as the punch-through distance the latter being a basic reflection of the severity of a potential punch-through failure.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 04-2020
Publisher: MDPI AG
Date: 07-05-2023
DOI: 10.3390/JMSE11050996
Abstract: Since concrete is cheaper and more resistant to corrosion than steel, the wide-shallow concrete bucket foundation is being used extensively in ocean engineering. By adding the inner bucket and cruciform skirts, both the bearing capacity and rigidity of the wide-shallow concrete bucket foundation increase significantly. When compared to the hollow steel bucket foundation, the inclusion of thicker skirts, as well as the addition of inner bucket and cruciform skirts, would cause changes to the soil flow mechanism, resulting in soil heave within each compartment and changes in soil strength evolution and penetration resistance during installation in clay. In order to study the influence of the addition of the inner bucket and cruciform skirts on the soil heaving inside each compartment, soil softening and penetration resistance, three-dimensional large deformation finite element (LDFE) models for the bucket foundation with and without inner bucket, and cruciform skirts considering soil remolding were established using the Coupled Eulerian–Lagrangian (CEL) approach. It was found that the inner bucket significantly changes the soil flow and softening of the soil during penetration of the bucket foundation. According to the theoretical analysis and numerical results, the diameter of the optimal inner bucket is equal to 5/8 of the outer diameter. The adhesion coefficient observed in this study falls within the range of 0.5 to 0.8, which is higher than the theoretical value of 0.25 that assumes the soil is fully remolded. The reason for this discrepancy is that the soil is only partially remolded during the actual installation of the bucket foundation. The neglect of the softening of the soil or considering the soil as completely softened will result in significant variation in the predicted penetration resistance hence, partial softening of the soil should be taken into account.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: Thomas Telford Ltd.
Date: 10-2018
Abstract: Assessing the potential for a punch-through failure during spudcan installation in sand-over-clay is crucial for reducing risk in the operations of mobile jack-up platforms. Typically, in the offshore industry, the peak penetration resistance and the depth at which it occurs are determined deterministically without rigorously considering the uncertainties in the soil. This paper proposes a probabilistic approach to estimate the peak resistance and the corresponding depth, as well as a Bayesian method of incorporating installation data to update the predictions. Instead of a single value in the deterministic analysis, a range of the potential peak resistances and depths can be estimated by accounting for the uncertainties in the soil, the spudcan's geometry and in the calculation method itself, with a database of 66 geotechnical centrifuge tests characterising the model. This prior probability is then updated using the monitored data, allowing a real-time update of the probabilities associated with candidate values of peak resistance and depth during the installation. The advantage of such a probabilistic updating model is shown in a retrospective simulation of a mobile jack-up platform in sand-over-clay conditions in the Gulf of Mexico. The results show that the prior estimation can be effectively refined by incorporating the monitored data. The proposed method provides a powerful tool for assisting decision-making during the installation of jack-ups offshore.
Publisher: MDPI AG
Date: 27-06-2022
DOI: 10.3390/JMSE10070885
Abstract: This paper proposes the penetration displacement solutions of large-diameter open-ended steel pipe piles (LOSPs) with the diameter exceeding 2 m subjected to hammering load. The ultimate forcing equilibrium relationships between LOSP and soil are analyzed, and the calculated formula for self-sinking depth is derived. Next, a partial differential equation of pile hammering by single blow in soft soil is developed based on wave equation incorporating the kinematic method. A dynamic coefficient of frictional resistance (DCFR) is implemented in the process of derivation, and then the displacement Fourier analytical expression of LOSP under hammering load is presented. The parameters sensitivity of the analytical solution is investigated, and the displacement curve is compared with the numerical result. The new method presented in this paper could be used to assess the penetration development of driven piles under impact loading to predict the punching through or hammer refusal during penetration.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: Elsevier BV
Date: 12-2017
Start Date: 05-2022
End Date: 04-2026
Amount: $283,353.00
Funder: Australian Research Council
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