Zheng J.,National University of Singapore |
Palmer A.,National University of Singapore |
Brunning P.,Subsea 7 |
Gan C.T.,Geomarine Ltd.
Ocean Engineering | Year: 2014
A trawl gear impact on an underwater pipeline can create a dent that pushes part of the pipe wall inward. External pressure also tends to push the wall inward. Because of that interaction, an impact under external pressure dents the pipeline more severely than the same impact with no external pressure. The interaction has been investigated as part of a wider study of overtrawlability of pipe-in-pipe systems carried out by the National University of Singapore. The problem is important because the need to protect pipelines against trawl gear impact leads to a requirement to trench medium and small-diameter pipelines. Trenching is costly and a frequent source of delays and disputes, and so it is worthwhile to search for ways to eliminate unnecessary trenching. A finite-element model of denting under external pressure for single wall pipe and pipe-in-pipe using hydrostatic fluid element has been established and verified by comparison against published data and current experiment data. Parametric study of different external pressures shows the effect of external pressure on the denting process. The combinations of the internal pressure, external pressure and indentation are considered. The study shows that when the internal pressure of a dented subsea pipe is decreasing, the possibility of buckle propagation for the single wall pipe is higher than it is for the pipe-in-pipe. © 2014 Elsevier Ltd. All rights reserved.
Lauder K.D.,University of Dundee |
Lauder K.D.,Lloyd's Register |
Brown M.J.,University of Dundee |
Bransby M.F.,University of Dundee |
And 2 more authors.
Canadian Geotechnical Journal | Year: 2012
Pipeline plough behaviour has been investigated by means of reduced scale physical model testing. A testing programme was devised to investigate the influence of permeability, relative density, and plough depth on the associated tow force measured during ploughing over a range of velocities in saturated granular material. An increase in tow force with velocity was found during all of the tests and the results have been compared to previously developed analytical models. A new empirical equation has been developed to describe the change in tow force with velocity for a variety of model siliceous sand conditions. Application of this new approach to full-scale ploughing requires consideration of scaling effects and the use of appropriate input parameters determined to replicate field conditions.
Dudzinski K.M.,Geo Marine Inc. |
Brown S.J.,Geo Marine Inc. |
Lammers M.,Hawaii Institute of Marine Biology |
Lucke K.,University of Kiel |
And 7 more authors.
Journal of the Acoustical Society of America | Year: 2011
Deployment of any type of measuring device into the ocean, whether to shallow or deeper depths, is accompanied by the hope that this equipment and associated data will be recovered. The ocean is harsh on gear. Salt water corrodes. Currents, tides, surge, storms, and winds collaborate to increase the severity of the conditions that monitoring devices will endure. All ocean-related research has encountered the situations described in this paper. In collating the details of various deployment and recovery scenarios related to stationary passive acoustic monitoring use in the ocean, it is the intent of this paper to share trouble-shooting successes and failures to guide future work with this gear to monitor marine mammal, fish, and ambient (biologic and anthropogenic) sounds in the ocean-in both coastal and open waters. © 2011 Acoustical Society of America.
Hall S.A.,Red Rock Geological Enterprises |
Miller M.R.,Geo Marine Inc. |
Goble R.J.,University of Nebraska - Lincoln
Bulletin of the Geological Society of America | Year: 2010
The Bolson sand sheet occurs in the Tularosa Valley, New Mexico, and the Hueco Bolson, Texas and consists of two principal eolian sand units. Optically stimulated luminescence (OSL) dating provides a new chronology of the sand sheet that relates as well to the formation, preservation, and visibility of the local archaeological record. The lower sand (unit Q2) (44.8 ± 2.9 ka) and the upper sand (unit Q3) (22.2 ± 1.6-5.2 ± 0.3 ka) have a combined thickness of less than 2 m. The Q2 sand is characterized by a red Bt paleosol, and the Q3 sand has a weak calcic paleosol with stage I carbonate morphology. Elevated amounts of airborne silt were incorporated in the Q3 sand during the period 24-14.5 ka, representing higher amounts of dust in the atmosphere during glacial and lateglacial time. Multiple OSL ages from the Q3 sand indicate a slow net sedimentation rate of 0.06-0.09 mm/yr, similar to other OSL-dated sand sheets in the region; sand deposits in dune fields have higher accumulation rates. The McGregor A horizon soil, radiocarbon-dated to younger than 0.5 ka, occurs at the top of the sand sheet and likely formed with desert grassland vegetation. Thousands of recent mesquite coppice dunes (unit Q4d) mantle the sand sheet, and two are dated to the twentieth century by OSL and 137Cs. Archaeological sites that postdate 3000 B.C. are concentrated, sometimes together, on the surface of the sand sheet, while sites that predate 3000 B.C., although rare, may be buried within the Q3 eolian sand. The Q2 sand is too old to contain archaeological sites, although site features may intrude into the sand. Previous chronologies of the sand sheet are based on radiocarbon dates of charcoal from archaeo logical sites, on radiocarbon dates of soil carbonate, and on soil-geomorphology correlations with Rio Grande Valley alluvium. The optical chronology does not support these various correlations. We recommend that the alluvial names Isaacks' Ranch, Fillmore, and Organ no longer be applied to the Bolson sand sheet. © 2010 Geological Society of America.
Levesque J.C.,Geo Marine Inc |
Levesque J.C.,Environmental Resources Management Inc.
Wildlife Biology in Practice | Year: 2013
Marine fish are among the most challenging type of wildlife to examine in the field given their expansive range, spatial and temporal distribution, and specific early life-history traits. Different researchers have investigated the catch efficiency of various sampling gears and techniques; however, field-sampling information is mostly unavailable for ladyfish (Elops saurus), an economically valuable species in the southeastern United States. The main purpose of this investigation was to evaluate, for the first time, various sampling gears potentially useful for targeting ladyfish. The specific objectives were to examine and compare differences in capture efficiency and size selectivity of different sampling gears useful for collecting ladyfish in nine Florida water bodies. This investigation found that ladyfish relative abundance, size, and length-frequency distribution varied significantly by sampling gear and geographical location. The findings revealed the most efficient gear for collecting ladyfish smaller than 100 mm SL were seines with an offshore deployment method and the least effective were otter trawls. Overall, seine catch efficiency decreased and gillnet efficiency increased with ladyfish size. These finding indicate it's essential that researchers use a variety of sampling gears to reduce any potential gear or sampling bias when designing field studies. © 2013 J.C. Levesque.
Precht W.F.,Dial Cordy and Associates |
Deslarzes K.J.P.,Geo Marine Inc. |
Hickerson E.L.,National Oceanic and Atmospheric Administration |
Schmahl G.P.,National Oceanic and Atmospheric Administration |
And 2 more authors.
Marine Geology | Year: 2014
Fossil elkhorn corals, Acropora palmata, were discovered at the Flower Garden Banks (FGB) on the shelf-margin off the Texas coast in 2006. Radiocarbon dating revealed an A. palmata-dominated community aged 10,157-6838. cal BP. The Acropora reefs correspond in time to an interval of warmer-than-present sea-surface temperatures (SSTs) during the Holocene thermal maximum (HTM). The subsequent demise of A. palmata in the middle Holocene was a consequence of the inability of the shallowest reef facies to keep pace with rising sea level following complete submergence of the banks, possibly coupled with decreasing SSTs following the HTM. In 2007, the first fossil staghorn corals, Acropora cervicornis, were discovered at the FGB. Based on radiocarbon dating of these corals to 1027-211. cal BP, it appears that populations of A. cervicornis flourished in deeper waters (~. 25-32. m depth) on the edges of the banks until the peak of the Little Ice Age (LIA) when they died, presumably from cold-water exposure. The recent return of A. palmata to reefs of the FGB associated with increasing sea temperatures appears to be both an echo of the past and a harbinger of the future. © 2014 The Authors.
Whitt A.D.,Geo Marine Inc. |
Dudzinski K.,Geo Marine Inc. |
Laliberte J.R.,Geo Marine Inc.
Endangered Species Research | Year: 2013
The presence of endangered North Atlantic right whales Eubalaena glacialis in the mid-Atlantic region of the USA is not well understood. Adequate protection of right whales in the face of plans to develop offshore renewable energy requires more information about this species' distribution and occurrence in this region. We present findings from the first year-round study dedicated to marine mammals in New Jersey's nearshore waters using line transect surveys and passive acoustic monitoring. Four groups of right whales, including a cow-calf pair, were sighted. Right whales were detected acoustically during all seasons. Sightings of females and subsequent confirmations of these same individuals in the calving grounds a month or less later illustrate that these waters are part of this species' migratory corridor. Observations of skim-feeding behavior suggest that feeding may also occur in areas farther south than the main feeding grounds. Based on the year-round occurrence of right whales offNew Jersey, we recommend that presumed seasonal migratory patterns not be used alone to determine the timing of construction activities or monitoring/mitigation efforts for offshore development. Our results also provide support for the expansion of existing critical habitat to include nearshore waters of the mid-Atlantic. © Inter-Research 2013.
Machin J.B.,Geomarine Ltd |
Allan P.A.,Geomarine Ltd
Frontiers in Offshore Geotechnics II - Proceedings of the 2nd International Symposium on Frontiers in Offshore Geotechnics | Year: 2011
Apparently simple upon first inspection, following careful analysis the water jet excavation of stiff clay soils is found to be a complex process. Due to the early lack of technical data, engineers working in the field of soil jetting first used empirical approaches and rules-of-thumb to quantify and model the process. Over the last ten years or so more data has become available, both from research work and actual field operations. As a result, a more scientific approach to the problem is now available. A design methodology is described in this paper. It has recently been applied by the authors to the design of a number of jet trenching and excavation machines and in the assessment of a number of jet trenching and excavation projects in stiff clay soils. © 2011 Taylor & Francis Group, London.
Levesque J.C.,Geo Marine Inc. |
Richardson A.,Geo Marine Inc.
Wildlife Biology in Practice | Year: 2011
The demand on our marine resources is increasing at unsustainable rates at the same time that many fish stocks are overfished, already collapsed or at risk of extinction. In 2006, recreational anglers landed about 4,809 mt of coastal pelagic species in the Gulf of Mexico, which was above the Maximum Sustainable Yield estimate (4,702 mt). Despite this urgency, marine policy and management is complex, controversial, and time consuming. One tool that resource managers use for managing, protecting, and conserving marine resources is designating Marine Protected Areas (MPAs). Presently, the public is concerned with the impacts of fishing on the status of fish stocks associated with the Flower Garden Banks National Marine Sanctuary (FGBNMS). Recreational fishing is among the most popular marine activities associated with MPAs; however, few studies have evaluated the impact of this activity on the local resources. Given these conservation and social issues, the main goal of this study was to provide a characterization of the recreational fisheries associated with the FGBNMS. Findings showed that recreational landings were dominated by red snapper, vermilion snapper, and gray triggerfish. Cumulative landings and catch rates varied significantly by species, month and location. Overall, the highest fishing effort was in summer, and the highest catch rates were in winter. The greatest catch rates for reef fish and coastal pelagic species were in the southernmost (Laguna Madre) and northernmost (Galveston) origination ports, respectively. Based on monthly catches, there was some evidence that recreational anglers target spawning snapper aggregations. The annual mean weight for gray triggerfish was stable, but the mean weight of both red and vermilion snapper declined between 1986 and 2006. Copyright © 2011 J.C.Levesque; A.Richardson.
Bozhilova M.,GeoMarine Ltd |
Georgiev V.,GeoMarine Ltd |
Georgieva A.,GeoMarine Ltd |
Kostadinova R.,GeoMarine Ltd
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM | Year: 2015
The aim of the article is to present the methodological approach for execution of monitoring of the marine and terrestrial environment during the preconstruction, construction and operational phases of a large scale infrastructure project located partly onshore and mainly offshore in the territorial water and the exclusive economic zone (EEZ) of Bulgaria. The environmental monitoring is planned for all phases of the project in order to determine the baseline conditions in the project area, to assess the consequences (impacts) of the project’s realization (propose corrective measures if necessary) and to timely plan and conduct the necessary mitigation measures, as well to monitor and register the recovery of the environment after the construction phase. Subject to monitoring are the main components of the marine (water quality, sediment quality, phytoplankton, phytobenthos, zoobenthos, ichthyofauna, cetaceans, sea birds) and terrestrial environment (air quality, noise, surface and ground water, protected plant species, invertebrates, amphibians, reptiles, birds, mammals, bats). The article presents the general considerations, taken into account in the designing of a complex monitoring program for physical and biological, marine and terrestrial environment and the methods, applied for the specific project. © SGEM2015.