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to

GoIn paper the ice conditions in the Yellow Sea are estimated on the base of maps of boundaries of ice extending and ice concentration in the period of 1997-2004. The isograms of boundaries of ice extending in the Yellow Sea with probability of 0 %, 25 %, 50 %, 75 % and 100 % were received. The thickness of a fast ice at the end of 1997-2004 winters was calculated by different formulas and satellite maps.

The Yellow Sea is exposed to strong influence of solar radiation. However, the winter northwest monsoon brings cold masses from the central Asia. As a result, the average monthly temperature of air in January in the north of the sea reduces down to -10°C at an absolute minimum down to -30°C. Hence, there the intensive ice formation occurs. That complicates winter navigation, fishing, and also production of mineral resources and hydrocarbons from a seabed.

Literary information about the ice cover of the Yellow Sea practically is absent, and what the available data (Sea Atlas, 1950; Oceanographic Encyclopedia, 1974; Liu The-fu&Li Tong-kui, 2004) have fragmentary nature.

Use of the satellite information of the National Ice Centre of the USA, placed in Internet for period from 1997 till 2004, and also historical information about ice, has allowed to make a series maps (for ten-day periods) of boundaries of ice extending in the Yellow Sea in isograms of probability 0, 25, 50, 75 and 100%. The isograms of boundaries of ice extending in the Yellow Sea with probability of 0 %, 25 %, 50 %, 75 % and 100 % were received on the base of statistical methods of computer processing of data for ice season in the 1997-2004 periods.

ISOPE-I-06-001

The Sixteenth International Offshore and Polar Engineering Conference

Walker, Daniel A.G. (Department of Engineering Science, University of Oxford) | Taylor, Paul H. (Department of Engineering Science, University of Oxford) | Taylor, Rodney Eatock (Department of Engineering Science, University of Oxford) | Zang, Jun (Department of Engineering Science, University of Oxford)

This work investigates the feasibility of using diffraction solutions to predict extreme green water levels beneath multi-column gravity based structures. The ultimate aim is to provide improved design tools for predicting the height the deck structure must be raised above mean sea level (airgap) for the lower deck to avoid green water impact. Such tools, when fully validated, will replace the need to carry out model tests during preliminary design. Results for a real platform configuration are examined in this paper to highlight the key issues complicating the validation of diffraction based design tools for real structures. Incident regular waves are considered.

The interaction of large ocean waves with oil and gas production platforms remains a major design consideration. There is particular interest in the offshore industry in the prediction of the maximum height above mean sea level to which significant volumes of water are projected. Whilst not always threatening the overall integrity of the structure, water projection can damage equipment and lead to expensive production downtime. At present most platform designs incorporating large diameter columns (e.g. gravity based structures) are model tested in wave tanks with little idea beforehand as to the effect the wave-structure interaction will have on extreme water levels. Linear diffraction solutions, which are based on small amplitude wave theory, are commonly used by the offshore industry prior to model testing to obtain an estimate of the extreme free surface magnifications. There is a considerable need for a validated design methodology that enables the accurate prediction of extreme free surface magnifications in the vicinity of multi-column structures.

The proposed problem has been approached using linear and second order diffraction solutions. The important features of a nonlinear diffraction solution have been investigated by extending linear diffraction theory to a second order approximation using a Stokes

ISOPE-I-06-071

The Sixteenth International Offshore and Polar Engineering Conference

SPE Disciplines:

Lien-kwei, Chien (Dept. of Harbor and River Engineering and Coastal Disaster Prevention Research Center, National Taiwan Ocean University) | Tsung-shen, Feng (Dept. of Harbor and River Engineering and Coastal Disaster Prevention Research Center, National Taiwan Ocean University) | Ciou-yun, Chen (Dept. of Harbor and River Engineering and Coastal Disaster Prevention Research Center, National Taiwan Ocean University) | Chih-hsin, Chang (Dept. of Harbor and River Engineering and Coastal Disaster Prevention Research Center, National Taiwan Ocean University)

For providing more convenient analysis method of soil liquefaction evaluation, the local soil parameters with the liquefied case in 921 Chi- Chi earthquake was discussed. The earthquake force considered in this study was the active fault of Taiwan and the data processing in large areas were used in GIS window environment. The local simplified estimating mode for soil liquefaction in Taiwan was base on the method of parameter statistics, and generalizes parameters from the 300 sets liquefaction data in 921 Chi-Chi earthquake and 40 sets overseas cases in liquefied analysis discussion.

In recent 40 years, the disaster with soil liquefaction was become the important geotechnical problem. The liquefaction mechanism, potential evaluation and disaster protection were the category in research process. The evaluation of vibrating force considered the parameters with the maximum ground acceleration (PGA) and earthquake magnitude (M) when discussed the liquefaction mechanism. Moreover, many researchers advanced the criteria to evaluate the liquefaction potential. After 921 Chi-Chi earthquake, many researchers predicted that the possibly liquefied areas and demonstrated the applicability by applying the established criteria to the local areas in Taiwan. For the reason of lacking local liquefaction criteria in Taiwan and avoiding disaster happened diffusely, the Taiwan local liquefaction criteria established was indispensable and important research topic.

According to the present simplify evaluation methods of liquefaction potential, the results of one site show only one-point potential after analyzing from field or laboratory experiments. However, the stratum was non-homogenous greatly. The result of liquefaction potential analysis on one location could not indicate the potential of a boring hole. To avoid the difference of soil properties, the geology statistics method were adopted to analysis liquefaction potential that considered the related parameters of soil by probability and displays the results with regional map.

ISOPE-I-06-296

The Sixteenth International Offshore and Polar Engineering Conference

acceleration, accuracy, analysis, Artificial Intelligence, classification, Earthquake, GIS, grade, ilp, information technology software, IT software, layer, liquefaction, liquefaction case, liquefaction evaluation, liquefaction potential, management and information, model, PGA, Soil Liquefaction, spatial reasoning, study

Technology: Information Technology > Artificial Intelligence > Representation & Reasoning > Spatial Reasoning (0.47)

Ochi, Hiizu (Osaka Institute of Technology) | Sawai, Takeshi (Osaka Sangyo University) | Kawai, Gosaku (Osaka Sangyo University) | Ogawa, Koichi (Osaka Prefecture University) | Yamamoto, Yoshiaki (Setsunan University) | Suga, Yasuo (Keio University)

The relationships between tensile strength and deformation heat input in the upset stage or upset burn-off length was examined on the friction welding of copper to various metals. It was found that in Cu/Cu, Cu/S35C, Cu/SNC631, Cu/SUS304 and Cu/Ni joints, a stable tensile strength was obtained when the deformation heat input in the upset stage or the upset burn-off length exceeded a certain value. In Cu/Ti joint, it was not possible to classify joints into sound and poor by the deformation heat input in the upset stage or the upset burn-off length.

Friction welding is used in many fields because the procedure is easily automated and it is possible to weld dissimilar materials. However, there are still unresolved issues with this method, such as the difficulty in setting the appropriate welding conditions for some materials, and the variance of optimum welding conditions depending on the different friction welding machines. Recently, the authors began examining a method of evaluating joint strength by analyzing heat input, which is the mechanical work done during friction welding, in order to logically set the appropriate welding condition. Heat input consists of friction heat input by friction (Japan Friction Weld. Assoc. edition, 1979) and deformation heat input by deformation of the weld material (Ochi et al., 2000: Ochi et al., 2002: Ochi et al, 2003a). In the friction welding of similar joints of 5056 and 6061 aluminum alloys, and SUS304 stainless steel (Ochi et al., 2000, Ochi et al., 2002, Ochi et al, 2003a), the authors previously examined the relationships between joint strength and heat input (friction heat input, deformation heat input and total heat input in the friction stage, the upset stage and total stage), and revealed that tensile strength and fatigue strength could be evaluated deformation heat input in the upset stage.

ISOPE-I-06-082

The Sixteenth International Offshore and Polar Engineering Conference

Beng-Chun, Lee (Department of Environmental & Hazards-Resistant Design, Huafan University) | Hui-Lan, Xu (Department of Environmental & Hazards-Resistant Design, Huafan University) | Shun-Ping, Tsao (Department of Environmental & Hazards-Resistant Design, Huafan University)

On the basis of the observed groundwater level and rainfall data from 2002 to 2004, this paper finds out that there is a positive relationship between the rainfall and groundwater level. The result also shows that the peak patterns of rainfall and groundwater level with unimodal and multimodal is very unanimous. In 33 cases of peak of rainfall and groundwater level, the rainfall duration of Northeast monsoon is relatively long and makes 3.39m of maximum relative water level for 6~7 days. The rainfall produces 2.78m of maximum relative water during the typhoon season for 2~3 days. Moreover, it is show that the variation energy is stronger in winter than that of summer with the dominant period in the range between 5 to 10 days.

The researches toward surface water are plentiful in Taiwan, including various formulas, statistic analysis, time-series analysis and mathematic models etc. For the groundwater level study, most topics are related to the contain water layer simulation (Jeng, 2002), pollution of groundwater (Chiang et al., 1990), which use less statistic method or time-series analysis to study the relationship between the groundwater level and rainfall... As a result of the lack of empirical data, there is less finding on groundwater on the up stream of watershed. The source of groundwater usually comes from the permeation of surface water, especially when typhoon accompanies a lot of rainwater. When soil water increases up to a limit, the pore water pressure arises and correspondingly slips the stratum. After a period of permeation, in the wake of gravity, the level of groundwater will rise, and made the ground softens and expands, which decrease the strength of the resistance of shear force, and finally collapse and slip land mass.

ISOPE-I-06-310

The Sixteenth International Offshore and Polar Engineering Conference

Pollio, A. (D. I. A. S. S. , Technical University of Bari) | Marano, G.C. (D. I. A. S. S. , Technical University of Bari) | Mossa, M. (D. I. A. S. S. , Technical University of Bari) | Langley, R.L. (Department of Engineering, University of Cambridge) | Low, Y.M. (Department of Engineering, University of Cambridge)

A comparison of time domain and frequency domain analysis of a flexible marine riser undergoing large deformations by using a lumped mass approach is described in this paper. The riser is modeled as a set of lumped masses connected by axial springs with a structural axial damping and the external forces acting on it are due to the surface waves, the hydrodynamic loads represented by a modified form of the Morison’s equation, and to the top end motion of the pipe due to the vessel’s motion. The effect of the shear force along the riser is also considered.

This work describes the non linear dynamic behavior of the riser in the time domain, obtained by using an implementation of the Runge-Kutta 113 algorithm provided in Matlab. Moreover the natural frequencies and the natural mode shapes of the riser are obtained by using a tangent stiffness matrix due to the sum of the axial stiffness and the bending stiffness.

The main aim of the paper is to compare results from the time domain analysis with those yielded by a linearised frequency domain analysis.

Oil industry uses various type of coal oil extraction systems depending on ocean depth at which it is possible to find new oilfields; flexible marine risers are flexible pipes widely used in the offshore engineering field when sea depths greater than a few hundred meters are involved in the extraction operations; in this case the risers are used to transfer crude oil and gas from the seabed to a recovery and production platform (properly modified tankers or extraction equipment).

Because of the high depths involved these pipes, considered as slender members since their diameter is smaller than the ocean wave height, are subjected to external forces that may induce high internal stresses into the same pipe.

ISOPE-I-06-132

The Sixteenth International Offshore and Polar Engineering Conference

SPE Disciplines: Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Risers (1.00)

Hirose, T. (Department of Food Systems and Field Science, Graduate School of Science and Technology, Kobe University) | Tanaka, T. (Department of Agricultural and Environmental Engineering, Faculty of Agriculture, Kobe University) | Inoue, K. (Department of Agricultural and Environmental Engineering, Faculty of Agriculture, Kobe University) | Sakaida, T. (Tango Public Works and Construction Office, Department of Construction, Kyoto Prefecture)

This paper discusses the decrease in the safety factor for seepage failure of subsoil due to bridge abutment construction within a cofferdam for two cases: (1) where piping occurred in the subsoil under a downstream bridge abutment, in which gravel was overlaid with silty sand of low permeability and (2) where piping did not occur in the upstream subsoil, where gravel prevailed. Analyses of seepage flow and stability against seepage failure were conducted before and after the abutment construction for these cases, and the following results were obtained: The safety factor against seepage failure of subsoil decreased to Fs=0.809 (1/1.81) after the abutment construction for the downstream case, and to Fs=2.700 (1/2.30) for the upstream case.

When the I-River bridge abutments were constructed in a cofferdam, piping occurred in the subsoil under the downstream abutment on the left bank. Settlement of the abutment was observed one week after placement of stem concrete. At this location, a gravel layer was overlain by a silty sand layer of low permeability and the hydraulic head difference inside and outside the cofferdam was 2.225 m. On the other hand, piping did not occur in subsoil under the upstream abutment on the left bank, where there was no silty sand layer.

Analyses of seepage flow by FEM and stability against seepage failure were conducted before and after the abutment construction for these cases. Characteristics of the seepage flow, causes of piping and the decrease in the safety factor for seepage failure of the subsoil due to abutment construction are discussed.

Geology and bridge abutment construction Fig. 1 shows the site of the I-River road bridge, which is located on an alluvial plain in the southern part of Lake Biwa in Shiga Prefecture, Japan.

ISOPE-I-06-161

The Sixteenth International Offshore and Polar Engineering Conference

SPE Disciplines:

Flat dilatometer test (DMT) was carried out at Ariake site in Japan. As a result, results from DMT gave reasonably accurate predictions of soil parameters in geotechnical engineering design except for undrained shear strength of cohesive soils. At this stage, we used modified equations of undrained shear strength and over-consolidation ratio of cohesive soils proposed Kamei and Iwasaki. Finally, we reconfirm that DMT has an important role to play as a profiling tool to provide useful information for in-situ soil parameter predictions.

The flat dilatometer in-situ testing device (Marchetti, 1980) has been used frequently in North America and Europe during the brief period since its introduction. The DMT has several significant advantages: (i) the equipment is relatively simple and rugged, (ii) the procedure is easy to carry out and can be used repetitively and rapidly, (iii) tests can be carried out for most soil types, and (iv) many useful correlations have been developed. The procedure consists of a potential in-situ penetration plus dilation (expansion) test (Kamei and Enomoto, 1998).

The DMT test consists of forcing the steel dilatometer blade vertically into the soil to a desired test depth, measuring the thrust to accomplish this penetration, and then using gas pressure to expand a circular steel membrane located on one side of the blade. Figure 1 shows a schematic diagram of DMT system. More detailed schematic diagrams of DMT system have also been described elsewhere (Marchetti, 1980; Kamei and Enomoto, 1998; Schmertmann, 1986).

Beneath the membrane is a measuring device which turns a buzzer off in the control box at the surface when the membrane starts to lift off the sensing disc, and turns a buzzer on again after a deflection of 1mm at the center of the membrane has occurred.

ISOPE-I-06-083

The Sixteenth International Offshore and Polar Engineering Conference

Li, Xin (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University) | Yang, Jianmin (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University) | Xiao, Longfei (State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University)

The motion performance of the soft yoke mooring FPSO system in shallow water is investigated. Both numerical simulations and experiments are performed to model the soft yoke mooring of an FPSO. A time-domain algorithm based on Cummins impulse response technique is used to calculate the motion prediction of the system. By using the multi-rigid analysis method, the static restoring force and dynamic mooring force of the tower-yoke system are analyzed and the dynamic equations of the soft yoke mooring system are obtained. The body motion equations in time domain have been coupled with the dynamic equations of FPSO mooring system. This time-domain method enables adding the environment conditions as to predict the motions and mooring forces on the entire FPSO system. The numerical simulations agree well with the results obtained from the model tests, hence this time domain, multi-rigid analysis method is capable of predicting well the motion performance of a large FPSO in shallow water.

Soft yoke mooring FPSO system is usually used in shallow water with water depth less than 50m. In China, six FPSOs have been put into productions which use soft yoke mooring system in the Bohai Bay (Mao,1998). In the coming future, several large FPSOs will be use in this area with the water depth from 15m to 30m. In such shallow water, the motion performance of large FPSO and mooring system become important safety problems (Yang and Xiao, 2000).

The FPSO is permanently moored by a soft yoke mooring system, which consists of tower, yoke, ballast, pendants and support frame. The yoke is designed to interface with the tower and vessel while transmitting mooring forces into the bearing. All the parts of the mooring system are rigid bodies and the weight of the ballast provide the restoring force of all the system.

ISOPE-I-06-063

The Sixteenth International Offshore and Polar Engineering Conference

SPE Disciplines:

Araki, Susumu (Dept. of Civil Engineering, Osaka University) | Miyoshi, Hirokazu (Dept. of Civil Engineering, Osaka University) | Deguchi, Ichiro (Dept. of Civil Engineering, Osaka University) | Fumoto, Hiroshi (Ministry of Land Infrastructure and Transport)

This paper describes topography change in the vicinity of submerged breakwaters and deformation of the submerged breakwater body measured in two-dimensional experiments. Water particle velocity was also measured in the experiments in order to investigate the relationship between the fluid motion and the topography change in the vicinity of the submerged breakwater. The authors show that offshore-directed mean velocity above the seaward slope and the crest of the submerged breakwater has an influence on the topography change in the vicinity of the submerged breakwater.

Sea bottom topography change in the vicinity of and under coastal structures is one of the important factors in the stability of the structures. Topography change in the vicinity of a coastal structure can cause a decrease in its hydraulic performances of the coastal structure even if the body of the structure itself is not damaged. Wave-dissipating blocks or armor units covering rubble mounds are sometimes scattered after a sever storm. The scattering of the blocks or the armor units causes a decrease in their hydraulic performances. One of the reasons for the scattering of the blocks or the armor units is lack of weight. However, Gomyoh et al. (1995) pointed out the instability of breakwaters caused by local scouring or wave-induced liquefied sand bed from field observations of damaged breakwaters.

Topography change (including local scouring) in the vicinity of typical coastal structures has been investigated. Irie and Nadaoka (1984) investigated the relationship between the wave height distribution of partial standing waves and the sea bottom topography change in front of a vertical breakwater. Sawaragi (1995) conducted several studies on local scouring at sea dikes and summarized the influence of sea dikes on beach deformation. Suzuki and Takahashi (1998) investigated local scouring at the toe of a wave-dissipating type of breakwater.

ISOPE-I-06-333

The Sixteenth International Offshore and Polar Engineering Conference

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