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In the 1970’s and 1980’s, a number of grounded ice islands were used as drilling platforms in the Beaufort Sea. These islands were constructed by spraying sea water into the air to form ice, gradually building up a large platform area that eventually grounded on the seabed. One important factor in the feasibility of using ice in such a manner conce...
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The consequences of a large wind event occurring in the Southern California Bight on 31 January 2016, are analyzed using data from nearshore island and mainland seabed thermographs (10 to 20 m depths), NOAA meteorologic and wave-rider buoys, a CalCOFI cruise and SST and Chl a data products from satellite remote sensing. Discernible upwelling was di...
A need far detailed data on times, rates, and dynamies of sediment transport on the continental shelf has led to development of an instrument paekage (SWISH) whieh monitors sediment—water interaetion for periods of up to 30 days, and at depths to 200 m. The instrument has four sensing units: (a) a current meter to measure eurrent velocity 1 m above...
Punggur sea has many habitats, object, and structured of seabed with hight tide and wave. Side scan sonar is an underwater acoustic instrument for identification of seabed. This research aims to classify types of seabed and measure seabed identification into the sea water with grain size (dB), location, altitude (m) and target using side scan sonar...
Citations
An experimental set-up was constructed to study the friction behaviour of level ice and ice rubble on different seabeds at large scale and realistic stress levels. This paper presents the results of loading on a sand seabed. The tests were performed with a 4 m2 footprint with vertical stress levels up to 17 kPa. The ice was moved horizontally a distance of about 120 mm with displacement rates from 0.003 to 0.342 mm/s. Four position transducers measured vertical displacements. A total of 47 tests were conducted with level ice and another 24 with ice rubble. Friction coefficients of 0.47 and 0.39 for peak and steady shear stresses, respectively, were obtained with level ice. Those produced with ice rubble were 0.65 and 0.62 for the peak and steady shear resistance, respectively, which represents an increase of about 50% in shear resistance compared with level ice. Shear failure is believed to have occurred at the ice–sediment interface, although the sand's internal friction may have been fully mobilized by the ice rubble. Sediment freeze-up caused a substantial increase in sliding resistance. During this process, the failure plane is believed to have migrated downward and laterally along the freezing front, into the sand bed, with a concurrent increase in shear resistance up to levels comparable to the sand's internal friction. Sand compaction may have contributed also in increasing sliding resistance. These results may be useful for the design of spray ice pads and to assess the stability of grounded ice features.
In the Canadian Beaufort Sea, the design ice load can often govern the cost of gravity based (GBS) oil or gas production structures. By installing suitable ice barriers around the structure, the design ice load for the GBS and hence its cost may be reduced. The cost of three candidate GBS were calculated as a function of design ice load and soil strength. Similarly the cost of the ice barrier was estimated as a function of barrier type, design ice load and soil strength. It was found that for some of the production structures on cohesive soils, the overall cost of the GBS plus the cost of the barrier was less than designing the GBS for the full ice load.
Grounded spray ice pads have proven to be very suitable as drilling platforms in the Arctic’s shallow marine environment. To better understand the sliding resistance of ice pads, an experimental set-up was devised to measure ice-sand friction coefficients of a large block of saline ice. The experimental arrangement provided a “footprint” of 4 m2 with normal stresses up to 15 kPa. This represents realistic stress states for an ice pad in nature. The ice block was displaced over a distance of 0.12 m, at rates ranging from 0.0025 to 0.3 mm/sec, while recording the load required to do so. The average static and kinetic friction coefficients were 0.47 and 0.37, respectively, with an average cohesion of 0.5 kPa. These values did not vary with displacement rate. Sediment freeze-up at the ice-sand interface increased friction significantly.
