Susan Gourvenec

An evaluation of the PoLiSh smoothed regression and the Monte Carlo Cross-Validation for the determination of the complexity of a PLS model

Abstract A crucial point of the PLS algorithm is the selection of the right number of factors or components (i.e., the determination of the optimal complexity of the system to avoid overfitting). The leave-one-out cross-validation is usually used to determine the optimal complexity of a PLS model, but in practice, it is found that often too many components are retained with this method. In this study, the Monte Carlo Cross-Validation (MCCV) and the PoLiSh smoothed regression are used and compared with the better known adjusted Wolds R criterion.

Undrained Bearing Capacity of Deeply Buried Flat Circular Footings under General Loading

Estimation of a footing’s bearing capacity under general loading is a topic of wide interest, especially for the offshore energy industry. Although there have been several studies in the past few decades on shallow footings under general loading, limited work has been done for deeply buried footings. This paper presents results of a numerical investigation into the undrained bearing capacity of deeply buried flat circular footings in clay of both uniform and linearly increasing shear strength profiles. The footings’ uniaxial bearing capacities and failure surfaces under combined vertical, horizontal, and moment loading are reported. The results are analyzed in the context of application by the mobile jack-up industry, for which understanding of the circular spudcan footing’s bearing capacity under general loading is required for site-specific assessments. The paper also presents a parametric study on the effect of a footing’s aspect ratio (thickness/diameter) on its bearing capacity. To conclude, a closed...

Determination of the number of components during mixture analysis using the Durbin–Watson criterion in the Orthogonal Projection Approach and in the SIMPLe-to-use Interactive Self-modelling Mixture Analysis approach

Abstract The Orthogonal Projection Approach (OPA) and the SIMPLe-to-use Interactive Self-modelling Mixture Analysis approach (SIMPLISMA) are widely employed during process monitoring to obtain concentration profiles and/or pure spectra of a mixture. In the first step of these methods, it is extremely important to select the right number of components present in the mixture. This selection is not always obvious, and in this paper, the Durbin–Watson criterion was applied to dissimilarity values in OPA and to purity values in SIMPLISMA as a tool for the decision of the number of components. It is shown that this yields more objective results than visual interpretation.

Critical skirt spacing for shallow foundations under general loading

AbstractFinite-element limit analysis is used to identify the critical internal skirt spacing for the undrained failure of shallow skirted foundations under conditions of plane strain based on the criterion that the confined soil plug should ideally displace as a rigid block, such that optimal bearing capacity is realized. General loading (vertical, horizontal, and moment) is considered for foundations with skirt embedments ranging from 5 to 50% of the foundation breadth in soil having either uniform strength or strength proportional to depth. The results explicitly identify the number of internal skirts required to ensure soil plug rigidity under arbitrary combinations of horizontal and moment loading expressed as a function of the normalized skirt embedment and the maximum expected level of vertical loading as a fraction of the ultimate vertical bearing capacity. It is shown that fewer internal skirts are required with increasing normalized foundation embedment, but more internal skirts are required wit...

Use of the orthogonal projection approach (OPA) to monitor batch processes.

The orthogonal projection approach (OPA) and multivariate curve resolution (MCR) are presented as a way to monitor batch processes using spectroscopic data. Curve resolution allows one to look within a batch and predict on-line real concentration profiles of the different species appearing during reactions. Taking into account the variations of the process by using an augmented matrix of complete batches, the procedure explained here calculates some prediction coefficients that can afterwards be applied for a new batch.

Large-Deformation Numerical Modeling of Short-Term Compression and Uplift Capacity of Offshore Shallow Foundations

AbstractLarge-deformation finite-element analysis has been used to model the undrained response of skirted shallow foundations in uplift and compression. Large-deformation effects involve changes in embedment ratio and operative local soil shear strength with increasing foundation displacement—either in tension or compression. Centrifuge model testing has shown that these changes in geometry affect the mobilized bearing capacity and the kinematic mechanisms governing failure in undrained uplift and compression. Small-strain finite-element analysis cannot by definition capture the effects of changing foundation embedment ratio and variation in local soil strength with foundation displacement. In this paper, load-displacement relationships, ultimate capacities, and kinematic mechanisms governing failure from large-deformation finite-element analyses are compared with centrifuge model test results for circular skirted foundations with a range of embedment between 10 and 50% of the foundation diameter. The re...

Decommissioning – the next Australian oil and gas boom?

In the Oil and Gas Competitiveness Assessment recently published by National Energy Resources Australia (NERA), Australia ranked at the bottom of the group of 30 oil and gas producing nations in abandonment and decommissioning (NERA 2016). With the recent focus on the massive investment in liquefied natural gas (LNG), it is easy to forget that the Australian oil and gas industry is nearly 100 years old and many assets are reaching the end of their producing life. Liabilities are estimated at more than US

Failure envelope approach for consolidated undrained capacity of shallow foundations

21billion over the next 50 years (Wood Mackenzie 2016a). With nearly 70% of producing assets located offshore, this problem is complex and costly. The industry must develop strategies to address this looming challenge, however Australia has completed few large-scale decommissioning projects and currently lacks the required experience. This paper explores how Australia must: evaluate a range of approaches from complete removal to allowing assets to remain in situ; develop multi- and interdisciplinary solutions based on the collaborative input of all stakeholders and ocean users to develop a framework suited to our geographic location and environment; develop fit-for-purpose policies and regulations to support the most appropriate decommissioning framework for Australia, by learning from other countries, while recognising local uniqueness; and build workforce capability and capacity to support efficient and economical decommissioning activities and stimulate economic growth, which is more challenging than in other regions given our remoteness and high cost structure. The upcoming decommissioning wave represents a perfect ‘greenfield’ opportunity to apply innovative thinking, new technologies and collaborative approaches as well as an opportunity for Australia to demonstrate global leadership in this inevitable final stage of the lifecycle.

Optimal shear key interval for offshore shallow foundations

AbstractA generalized framework is applied to predict consolidated undrained VHM failure envelopes for surface circular and strip foundations. The failure envelopes for consolidated undrained conditions are shown to be scaled from those for unconsolidated undrained conditions by the uniaxial consolidated undrained capacities, which are predicted through a theoretical framework based on fundamental critical state soil mechanics. The framework is applied to results from small-strain finite-element analyses for a strip and circular foundation of selected foundation dimension and soil conditions, and the versatility of the framework is validated through a parametric study. The generalized theoretical framework enables consolidated undrained VHM failure envelopes to be determined for a practical range of foundation sizes and linearly increasing soil shear-strength profiles through the expressions presented in this paper.

Bearing capacity of a skirted foundation under VMH loading

Embedment of offshore shallow foundations is typically achieved by ‘skirts’, i.e. thin vertical plates that protrude from the underside of a foundation top plate and penetrate the seabed confining a soil plug. Skirted shallow foundations are often idealized as a solid, rigid element for geotechnical analysis of the foundation, on the assumption that sufficient skirts, or ‘shear keys’ will be provided to ensure that the deformable soil plug displaces as a rigid body. Should too few shear keys be provided, failure mechanisms involving deformation within the soil plug may occur, leading to a reduction in load-carrying capacity.There is currently no formal guidance regarding the optimal spacing of shear keys to ensure rigid body displacement of the soil plug. The absence of guidance may lead to unconservative designs if the number of shear keys is under estimated to save on fabrication or to conservative designs if additional shear keys are provided to minimize the risk associated with the uncertainty. Either case is undesirable and clear benefit is to be gained from a better understanding of shear key spacing.This paper presents guidance on the minimum number of shear keys required to achieve optimal capacity of square and rectangular skirted foundations (i.e. equivalent to that of a solid rigid foundation) under undrained generalized six degree-of-freedom loading in soft soils with linearly increasing shear strength with depth.Copyright