A theoretical analysis of the fluid-solid interactions governing the removal of woody debris jams from cylindrical bridge piers

This is the author accepted manuscript. The final version is avaialble from Cambridge University Press via the DOI in this recordThis paper proposes a theoretical model to describe previous laboratory observations of the dynamics of debris accumulations around bridge piers of cylindrical shape. The model is based on the assumption that the observed dynamics is mainly governed by dynamic changes of the point of application of the drag force exerted on the solid body formed by debris accumulated around the pier. A phase plane analysis of the resulting non-linear system of ODEs shows that the model captures the main patterns observed in previous laboratory experiments, including an oscillatory motion and the removal of debris from the pier by the flow. The model provides a theoretical basis for the analysis of the conditions required for debris jams to remain stable over long periods of exposure to impinging flow. Namely, the model indicates that stability of debris accumulations primarily depends on geometrical asymmetry and on the length of the extension downstream of the pier. The former induces the torque required to rotate the jam about the pier, while the latter produces a stabilising effect after the body rotates.Engineering and Physical Sciences Research Council (EPSRC

Embedding techniques for assessing debris-induced scour within practice

This is the final version.INTRODUCTION Background In the last decades, scientists, engineers and practitioners have become increasingly aware of the risks from debris blockage at bridge piers. Large wood is transported in rivers especially during flood events, in which debris could be entrapped by structures such as bridge piers, and may initiate an accumulation. The localised acceleration of the flow can substantially exacerbate the scour at the base of the pier that would normally occur with the pier alone, and consequently the risk of structural damage or collapse of the structure. Piers that have spread foundations, as most of the UK masonry bridge stock, are more prone to this problem. It was estimated that in the last century approximately more than a third of the bridge failures in the UK caused by scour involved the accumulation of woody debris (Benn, 2013). Similar figures were also observed in the US (Diehl, 1997). In 2015 the University of Exeter was awarded an EPSRC grant for the project Risk Assessment of Masonry Bridges Under Flood Conditions: Hydrodynamic Effects of Debris Blockage and Scour, the primary aim of which was the development of a robust method for estimating the scour depth at a bridge pier with debris accumulations. This research involved a comprehensive experimental investigation at the University of Exeter using a large flume. A total of 46 experiments was carried out. The results from these experiments along with those from others in literature were used to develop a functional relationship for predicting the maximum scour hole depth at a bridge pier. To implement the results from the research within the practice of non-academic partners, the University of Exeter in partnership with Devon County Council (DCC) started a project funded under an EPSRC Impact Accelerator Account (IAA) award. The IAA award focused specifically on trialling the methodology on DCC’s assets and using the knowledge to propose amendments to the current scour assessment practice, as recommended by the Highways England (HE) guidance document BD 97/12. BD 97/12, in its current form, acknowledges the importance of debris accumulations, but does not provide a systematic methodology to assess the effects of debris on scour. This report summarises the findings from the work undertaken as part of the IAA award. In particular, it summarises the proposed amendments to BD 97/12 and illustrates the impact of these changes on scour assessment practice via a number of full-scale case studies. [...]Engineering and Physical Sciences Research Council (EPSRC)Devon County Counci

An Experimental and Numerical Approach to Modeling Large Wood Displacement in Rivers (article)

This is the final version. Available on open access from Wiley via the DOI in this recordThe dataset associated with this article is available in ORE at https://doi.org/10.24378/exe.3383Large wood (LW) is used for river restoration, aquatic habitat conservation, and flood control; however, it can pose a threat to human life and the built environment. The formation of LW jams, river management strategies, and design of mitigation measures crucially all depend on how the large wood is transported along a river. This paper experimentally analyses at laboratory scale the motion of natural sticks in a long stretch of a straight channel (urn:x-wiley:00431397:media:wrcr25423:wrcr25423-math-000116 m), when LW is released at different locations and with different flow conditions. Results show that instream large wood, following a transient motion shortly after being released at the water surface, tends to follow preferential patterns along the channel. Froude number and location of large wood input may provide an estimation of the LW location in downstream reaches. Several mechanisms of motion were observed, some of which were very common, including a frequent tendency to assume a tilted position with respect to the direction parallel to the flow. The experiments also suggest that theories on secondary cells responsible for channeling LW in preferential directions are incomplete. A new model, based on acceleration induced by hydrodynamic actions, has been established and proposed in this work, showing promising results and paving the way for the development of a comprehensive model for transport of large wood at the river surface in full-scale applications.Natural Environment Research Council (NERC)Engineering and Physical Sciences Research Council (EPSRC

Intestinal endometriosis without evident pelvic foci treated with gonadotropin-releasing hormone agonist

[No abstract available

Trapping large wood debris in rivers: experimental study on a novel debris retention system (article)

This is the author accepted manuscript. The final version is available from the American Society of Civil Engineers via the DOI in this record.The dataset associated with this article is available in ORE at: https://doi.org/10.24378/exe.2703Large wood debris can cause critical damage to bridges and other riverine structures, and increase flood risk. Although their effects on hydrodynamic actions and flood levels have been investigated in recent research, little effort has been devoted to reducing the amount of debris that can accumulate at structures. This paper proposes and experimentally tests a new type of large wood debris retention system in which a series of alternating porous and rack-type modules, is placed in-line with the current. Laboratory tests illustrate that the proposed retention system can offer high levels of efficiency in trapping large wood in rivers. The geometrical features of the structure are observed to play a major role and can be carefully chosen to optimise trapping efficiency. Results also show that large wood debris trapped by these structures have limited effects on the increase of the upstream water levels. Further development of the solution proposed in this work can pave the way for use of low-cost, highly-effective debris retention systems for effective river management and large wood debris removal in practice.Engineering and Physical Sciences Research Council (EPSRC)Devon County Counci

Characterising the importance of porosity of large woody debris accumulations at single bridge piers on localised scour (article)

This is the author accepted manuscript.Data availability: The data used for supporting the results presented in this paper are openly available in ORE at: https://doi.org/10.24378/exe.4744The accumulation of large woody debris (LWD) at bridge piers is a serious hazard to the structural integrity of bridges across watercourses worldwide. The exacerbated scour that can directly result from LWD accumulations can lead to major structural damage or even catastrophic collapse. Recent research has led to empirical equations to estimate the scour depth for given LWD accumulation size; however these are mostly based on experimental tests with prismatic and impervious solid LWD accumulations, ignoring field observations that have shown that accumulations are neither impervious nor prismatic but are porous with inverted conical shapes. In this study, we therefore investigate the effects of porous LWD accumulations having shapes commonly observed in the field on scour holes. Results reveal that LWD size and shape, and flow characteristics are the primary factors influencing the erosion of sediments at the base of bridge piers. However, the porosity of accumulations is also observed to have a considerable effect on the size and maximum depth of scour holes. In particular, porous LWD reduce the maximum scour depth by up to 50% (and on average in the range of 5-25%) relative to the respective solid impervious accumulation. The results shown in this study also provide a practical tool for arriving at more realistic and less conservative estimates of scour depths at bridge piers when affected by LWD accumulations.Engineering and Physical Sciences Research Council (EPSRC)Devon County Counci

A Method for Evaluating Local Scour Depth at Bridge Piers due to Debris Accumulation

This is the author accepted manuscript. The final version is available from Thomas Telford via the DOI in this record This paper introduces a novel method for evaluating the effect of debris accumulation on local scour depth at bridge piers. The concept of a debris factor is proposed to replace the current effective and equivalent pier width approaches that have been shown to overestimate debris-induced scour in many instances. The concept enables a simpler, more direct and realistic estimation of the change in local scour depth due to debris since it accounts for (i) debris length (streamwise), width (spanwise) and thickness (depth wise), and (ii) the influence of debris elevation in flow, i.e. is applicable for free-surface debris, submerged debris, or debris resting on the stream bed. The concept works with all existing local scour equations alongside other factors that influence scour depth such as flow angle of attack and pier shape. The mathematical model that underpins the proposed concept is derived through multiple linear regression on experimental data obtained at Exeter and elsewhere. The proposed method is shown to improve accuracy by at least 24% and 5% in comparison to the effective and equivalent pier width approaches, respectively. More importantly, the method is shown to be robust, providing highly consistent results with significantly less uncertainty.Engineering and Physical Sciences Research Council (EPSRC

Efficacy and toxicity of bevacizumab in recurrent ovarian disease: an update meta-analysis on phase III trials

Background: To analyze the efficacy and toxicity of bevacizumab on survival outcomes in recurrent ovarian cancer. Results: Bevacizumab was associated with significant improvement of PFS and OS compared with standard treatment with HRs of 0.53 (95% CI 0.44 - 0.63; p < 0.00001) and 0.87 (95% CI, 0.77 to 0.99; p = 0.03), respectively. Bevacizumab increased the incidence of G3/G4 hypertension (RR 19.01, 95% CI 7.77 - 46.55; p < 0.00001), proteinuria (RR 17.31, 95% CI 5.42 - 55.25; p < 0.00001), arterial thromboembolic events (ATE) (RR 4.99, 95% CI 1.29 - 19.27; p = 0.02) and bleeding (RR 3.14, 95% CI 1.35 - 7.32; p = 0.008). Materials and Methods: Three randomized phase III trials representing 1502 patients were identified. Pooled hazard ratio (HR), odd ratio (OR), risk ratio (RR) with 95% confidence interval (CI) were calculated using fixed or random effects model. Conclusions: Adding bevacizumab to standard chemotherapy improved ORR, PFS and OS, and it had a higher, but manageable, incidence of toxicities graded 3 to 4

A practical method to assess risks from large wood debris accumulations at bridge piers

This is the author accepted manuscript. The final version is available on open access from Elsevier via the DOI in this recordAccumulations of large woody debris can worsen scour at a bridge pier and thereby lead to structural damage. Accumulations can also increase the flood risk in adjacent areas. These consequences can cause disruption to local communities and even pose a risk to human life. Current methodologies acknowledge the existence of these effects of debris but do not provide a practical method, usable by engineers and practitioners, to assess the potential for debris accumulation at a bridge structure based on readily available data. This work aims to address this practical need by proposing a methodology based on direct and indirect observations. Using this methodology, a desk-based analysis can be performed to assess whether a bridge is prone to the formation of debris accumulations. Direct observations may include information from inspection reports, satellite imagery and tree removal works, while indirect observations may use information related to the geographical location of the bridge such as on other structures that share the watercourse or the presence of forested areas in its proximity. This methodology has been applied to local authority-owned bridges in Devon, UK. Results show that a large number of the structures (100 out of over 3000 bridges) are liable to debris accumulations. Direct observations served as primary evidence for over 80% of the bridges liable to debris accumulations. For many cases, direct observations existed to corroborate indirect observations suggesting that indirect observations can also be relied upon. The proposed methodology has also been applied to the prioritisation of bridge inspections for scour assessment. Results showed that many of the bridges prone to debris accumulations would need to be prioritised for scour inspections over other bridges in the aftermath of floods due to their significantly higher risk to scour in the presence of debris.Engineering and Physical Sciences Research Council (EPSRC