捷运工程之联络信道采压气工法辅助施工案例探讨

高雄捷运橘线CO1区段标统包工程潜盾隧道分别穿越高雄港第三船渠及仁爱河,且本工程4座联络信道中有3座位于水际,开挖地层又属高地下水位之疏松粉土质砂层,施工风险较高.本工程原有2座联络信道已依设计分析结果采JSG高压喷射搅拌工法进行地质改良并采压气辅助施工顺利完成,后续2座原规划仅采用隧挖方式施工,惟在施工前恰巧邻标联络通道内集水井施工发生重大意外事故,且从该地区之地层特性等因素分析,为进一步降低施工风险,仍续采压气工法辅助施工.本文旨在说明本工程采压气工法辅助施工之设计与施工问题点与解决对策,以提供类似工程之参考.     

Use of cyanobacterial pigments to characterize the ocean surface mixed layer in the western Pacific warm pool

We collected biological and physical oceanographic data simultaneously from shipboard observations and mooring buoys in the Pacific equatorial warm pool during the 2002–2003 El Niño event and found that the vertical profiles of cyanobacterial pigments reflected the turbulent kinetic energy (TKE) better than did analyses of the mixed layer by temperature and salinity profiling. Zeaxanthin, an accessory pigment of cyanobacteria, was abundant and almost homogeneous in the warm pool within the surface mixed layer, although chlorophyll a concentrations were low. The intracellular content of chlorophyll a increases with increasing depth and decreasing light in a photoprotective response, but the zeaxanthin content does not change with depth. Hence, we hypothesized that the profile of the ratio of zeaxanthin to chlorophyll a would decrease with increasing depth if the water column were stable, without vertical mixing. On the contrary, vertically constant ratios would indicate vertical mixing. Our analysis using a numerical model showed a good agreement between profiles of these ratios and the profiles of TKE and supported the hypothesis. However, a comparative analysis of the zeaxanthin:chlorophyll a ratio profiles with mixed layer depth based on temperature and salinity data revealed two distinct patterns. In the first pattern, the ratio was uniform in the mixed layer when TKE was strong. In the second, the ratio decreased with increasing depth, even in the mixed layer, because of reduced TKE.     

A study on improving the course-keeping ability of a pure car carrier in windy conditions

The course-keeping ability of a pure car carrier (PCC) in windy conditions is discussed in this article. Numerical simulations of two PCCs were carried out to compare their course-keeping abilities in wind. The two PCCs had the same hull form but different types of rudder. One PCC was fitted with a semispade rudder (hereinafter, the normal rudder), whereas the other was fitted with a spade-type Schilling rudder (hereinafter, the Schilling rudder). Both PCCs were designed to a new concept for the accommodation structure and hull form above the load water line. In this new design concept, there are no sharp corners in the superstructure so as to reduce wind resistance and improve steering performance. The limits of course keeping for the two PCCs were investigated through simulations. The course-keeping abilities of the two PCCs, each with two different types of autopilot system, were also investigated in wind. To develop the numerical simulation, the hydrodynamic coefficients of the two PCCs were predicted based on the data published for a third PCC having similar principal particulars. The numerical model of the two PCCs was validated by comparing its behavior with the respective full-scale trial results. Wind resistance coefficients were predicted by combining the results of wind tunnel experiments of the object PCCs and a regression model. Numerical simulations under steady wind conditions were also carried out and the results compared with some full-scale experiments to validate the mathematical model of the PCC.     

Measurements of hydrodynamic forces, surface pressure, and wake for obliquely towed tanker model and uncertainty analysis for CFD validation

This article presents hydrodynamic forces and moments, surface pressures, estimated side force distributions, and wakes under oblique towing conditions for a practical tanker model (model KVLCC2M), which was designed by the Korea Research Institute of Ships and Ocean Engineering (KRISO). Ship offset data is readily available and can be obtained from the Internet. The model ship has no appendages and no rudder. Trim and sinkage were adjusted to zero in the static condition and the model ship was constrained against any motion. Although the drift angle β was primarily set to 0°, 6°, and 12°, other settings were used in some experiments. All experimental results were processed using uncertainty analysis. The uncertainty analyzing method follows the ANSI/ASME Performance Test Code (PTC19.1-1985) and the AIAA Standard S-071-1995. Only a few error components were considered here and they were empirically chosen because they had a heavy weighting when used in the uncertainty calculation. The results of these towing tank experiments will contribute to the development of computational fluid dynamics (CFD) research in ship hydrodynamics.     

Possible remedies for intact stability hazards involving contemporary small inland passenger ferries in Bangladesh

On the basis of previous studies, a series of hazards involving the typical small inland passenger ferries operating in inland Bangladeshi waters have been identified. In particular, stormy weather conditions, overloading, and the risk of crowding to one side have been determined as the typical events that are likely to lead to capsizing in the intact condition. In this article, possible hazard mitigation measures are discussed, both from the regulatory and from the design point of view, for a small inland ferry that is very similar to one that actually capsized in the past. The addressed design options involve ballasting and hull modification by means of additional buoyancy above the waterline. From a regulatory point of view, it is proposed that the present weather criterion in force in Bangladesh be modified by increasing the wind speed to be accounted for and by considering the concurrent effects of wind, rolling, and the crowding of people to one side.     

A rational analysis of intact stability hazards involving small inland passenger ferries in Bangladesh

The safety of inland passenger vessels operating in Bangladesh has been investigated. By thorough analysis of past accident data, the main causes of intact stability failures have been determined: adverse weather conditions and overloading, likely resulting in crowding to one side. Historical series of wind data were gathered and their analysis suggests that an increase in the wind speed presently used in the Weather Criterion in force in Bangladesh could be advisable. A model of a small passenger ship typically operated in Bangladesh has been analyzed in order to identify the most relevant hazards under intact ship conditions. A strongly jeopardizing effect of overloading under intact ship conditions has been detected when analyzing the hazard from the crowding of people to one side.     

Prediction method of hydrodynamic forces acting on the hull of a blunt-body ship in the even keel condition

The mathematical modeling group (MMG) model is well known and is widely used in the field of ship maneuverability. However, the MMG model can be applied only after determination of the hydrodynamic coefficients either from comprehensive captive model tests or from general empirical data. Around the cruising speed, when a ship's drift angle is relatively small, several methods have been developed to predict hydrodynamic coefficients from the ship's principal particulars, e.g., Kijima's method. Kijima's method is efficient in predicting the ship's maneuverability at the initial design stage and is even able to assess the effect of changes in stern design. Similarly, for the low speed range when a ship's drift angle is relatively large, several methods for predicting the ship's hydrodynamic coefficients have been proposed, based on captive model tests, such as those by Kose, Kobayashi, and Yumuro. However, most of the methods developed for low speeds cannot be applied to general ship types without additional experiments being performed. In contrast, Karasuno's method uses theoretical and empirical approaches to predict the hydrodynamic forces, even for large drift motions. Although Karasuno's model utilizes the ship's principal particulars and is applicable to a general vessel, it has not been widely used. This is because the form of Karasuno's model is relatively complicated and its accuracy around the cruising speed is less than that for other methods that have been specifically developed for the cruising speed range. A practical method for predicting hydrodynamic forces for the entire operating speed range of blunt-body ships is proposed in this article. It is based on the MMG model and predicts hydrodynamic coefficients based on a ship's principal particulars. A regression model for the proposed method has also been proposed by analyzing 21 different blunt-body ships. Finally, simulations of a very large 4-m crude carrier (VLCC) model using the proposed method were carried out and the results compared with free-running experiments (both at the cruising speed and at low speeds) to validate the efficacy of the model.     

与磁悬浮车辆现有超导磁体合为一体的线性发电机

为使用超导磁体(SCM)的磁悬浮运输系统开发不需接触地面的车上电源,对减少环境污染(噪声和废气的排放)是非常重要的.文章提出了将线性发电机(LG)并入现有SCM以提高输出功率、改善功率因数和测量系统的可行性,并在山梨磁悬浮试验线进行了试验.装在转向架左侧的线性发电机,在400km/h和500km/h的速度范围内,能为磁悬浮车辆提供25kW的电力.分析和运行试验测量的结果有良好的相关性.因此可望将线性发电机投入实际应用.     

Study on the maneuverability of a large vessel installed with a mariner type Super VecTwin rudder

The suitability of the Mariner type Super VecTwin rudder (hereinafter, the MSV rudder) for a large vessel is assessed in this article. Several experiments in a maneuvering pond were carried out and their results analyzed and summarized. Free-running tests such as turning, zigzag, and stopping tests were carried out with a 4-m free-running model of a very large crude carrier (VLCC) ship with the MSV rudder and the Mariner rudder. The results were compared to validate the maneuverability of a VLCC-sized a ship installed with the MSV rudder. A mathematical model of an MSV rudder is proposed for maneuvering simulation of a large vessel. To develop a maneuvering simulation for the model ship that was used in the free-running tests, hydrodynamic coefficients were estimated based on Kijima's regression formula. The coefficients of interaction between the hull and rudder (t_R, a_H, x_H) were obtained from a self-propulsion test in a towing tank. The complicated flow around the rudders is simplified to model the flow speed around the rudders. This simplified flow speed is utilized to compare the time histories of the free-running tests with the simulations. The mathematical model of the MSV rudder was further improved using the results of this comparison.     

Development of ocean carriers' behaviour model focusing on their 'cost and tariff' based on the spatial general equilibrium

Spatial computable general equilibrium (SCGE) theory has been applied to an international trade model to evaluate tariff and fiscal policies of a country. Those models can not be applied for the evaluation of transport policies such as port development and tax/subsidy policy against transportation sectors, since they do not deal with ocean freight and ocean carriers explicitly in the model. Ocean freight often varies with the changes of competitive conditions and/or demand/ supply balances in the short run, while it should reflect the actual expenditure of the carriers in the long run. The model proposed here considers the profit maximization behaviour of ocean carriers, and deals with ocean freight explicitly. The model is applied to four major economic regions; Japan, USA, EU and Asia. A multi-level function composed of the Cobb-Douglas function is adopted to produce reliable parameters of the production function for many industries.