Scour Protection of Underwater Pipelines

 A detailed literature review on the protection of local scour beneath a submarine pipeline is presented. The review covers two basic parts of countermeasures against the pipeline scour, namely preventing the onset of scour and stimulating the self-burial of a pipeline. The research progress on the methods of the two sections is discussed in detail separately. The methods preventing the onset of scour have been extensively studied, but the understanding on their mechanisms is yet to be improved. The progress in stimulating the self-burial of a pipeline mainly focuses on a spoiler attached to a pipeline, which is investigated comprehensively with both experiments and numerical simulations. Both parts of countermeasures have been applied in some practical engineering projects and the protection effects are generally satisfying

Scour Protection Effects of a Geotextile Mattress with Floating Plate on a Pipeline

Underwater pipelines are vital to the oil industry. Extending the service life of these pipelines is a key issue in improving the sustainability of oil transportation. A geotextile mattress with floating plate (GMFP) is a novel and sustainable countermeasure for scour and erosion control and is herein introduced to protect a partially buried pipeline from local scour in steady currents. A series of experiments was designed to verify the protection capabilities of the GMFP and investigate its parametric effects on protection. The average seepage hydraulic gradient under the pipeline was adopted to depict the protection effects of the GMFP, and was calculated with the pore pressure readings under the pipeline. The test results show that the GMFP is capable of protecting a pipeline from the onset of local scour in a unidirectional current. The average seepage hydraulic gradient below the pipeline decreases remarkably after a GMFP is installed. The average hydraulic gradient shows a descending trend with increased sloping angle &alpha when 0.64 &lt sin&alpha &lt 0.77. The hydraulic gradient hits a nadir at sin&alpha = 0.77 and climbs with the increasing sloping angle when sin&alpha &gt 0.82. The hydraulic gradient ascends when the bottom opening ratio &delta increases from 0.167 to 0.231, due to the decreased intensity of the bottom vortex. The hydraulic gradient drops with a rising plate height, except for a fluctuation at Hp = 0.12 m. An approximate negative correlation is found between the obstruction height of the floating plate and the average hydraulic gradient under the pipeline. This could be partially attributed to the extension and amplification of the bottom vortex on the leeside of the pipeline due to the increased plate obstruction height. Document type: Articl

Soil Microbial Communities and Mineralization Responses to Penicillin and Tetracycline Loads

ABSTRACT Residual effects of pharmaceutical antibiotics on soil microorganisms and turnover processes have merely been investigated. Therefore, this study explored the possible toxic effects of penicillin and tetracycline on indigenous bacterial communities and nitrogen mineralization in soil. Concentrations of 10 and 100 mg.kg -1 of penicillin and tetracycline antibiotics in soil affected the microbial community. The effect became apparent by a small tolerance increase and change in the phospholipids fatty acid (PLFA) pattern. The PLFA content revealed that most of the microbial groups decreased, while some specific microbial groups, e.g., 18:1ω9c, did not change in the soils even when soils were exposed to high concentrations of penicillin and tetracycline. Both antibiotics reduced the concentration of ammonium significantly, but that of nitrate was affected slightly. It was concluded that even at higher concentration, pharmaceutical antibiotics exert only a temporary pressure on soil microorganisms and selective processes in nitrogen turnover were negatively influenced

Emergency logistics for wildfire suppression based on forecasted disaster evolution

This paper aims to develop a two-layer emergency logistics system with a single depot and multiple demand sites for wildfire suppression and disaster relief. For the first layer, a fire propagation model is first built using both the flame-igniting attributes of wildfires and the factors affecting wildfire propagation and patterns. Second, based on the forecasted propagation behavior, the emergency levels of fire sites in terms of demand on suppression resources are evaluated and prioritized. For the second layer, considering the prioritized fire sites, the corresponding resource allocation problem and vehicle routing problem (VRP) are investigated and addressed. The former is approached using a model that can minimize the total forest loss (from multiple sites) and suppression costs incurred accordingly. This model is constructed and solved using principles of calculus. To address the latter, a multi-objective VRP model is developed to minimize both the travel time and cost of the resource delivery vehicles. A heuristic algorithm is designed to provide the associated solutions of the VRP model. As a result, this paper provides useful insights into effective wildfire suppression by rationalizing resources regarding different fire propagation rates. The supporting models can also be generalized and tailored to tackle logistics resource optimization issues in dynamic operational environments, particularly those sharing the same feature of single supply and multiple demands in logistics planning and operations (e.g., allocation of ambulances and police forces). © 2017 The Author(s

Scour Protection Effects of a Geotextile Mattress with Floating Plate on a Pipeline

Underwater pipelines are vital to the oil industry. Extending the service life of these pipelines is a key issue in improving the sustainability of oil transportation. A geotextile mattress with floating plate (GMFP) is a novel and sustainable countermeasure for scour and erosion control and is herein introduced to protect a partially buried pipeline from local scour in steady currents. A series of experiments was designed to verify the protection capabilities of the GMFP and investigate its parametric effects on protection. The average seepage hydraulic gradient under the pipeline was adopted to depict the protection effects of the GMFP, and was calculated with the pore pressure readings under the pipeline. The test results show that the GMFP is capable of protecting a pipeline from the onset of local scour in a unidirectional current. The average seepage hydraulic gradient below the pipeline decreases remarkably after a GMFP is installed. The average hydraulic gradient shows a descending trend with increased sloping angle α when 0.64 < sinα < 0.77. The hydraulic gradient hits a nadir at sinα = 0.77 and climbs with the increasing sloping angle when sinα > 0.82. The hydraulic gradient ascends when the bottom opening ratio δ increases from 0.167 to 0.231, due to the decreased intensity of the bottom vortex. The hydraulic gradient drops with a rising plate height, except for a fluctuation at Hp = 0.12 m. An approximate negative correlation is found between the obstruction height of the floating plate and the average hydraulic gradient under the pipeline. This could be partially attributed to the extension and amplification of the bottom vortex on the leeside of the pipeline due to the increased plate obstruction height

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