COASTAL AND PORT ENGINEERING IN CHINA

In this paper, a brief account of the characteristic features of the coast of China is given, followed by the present status and future prospects of coastal and port engineering in China, experiences gained and problems encountered. China has attached much importance to the rehabilitation and modernization of war damaged existing ports and the construction of new ports, as well as the maintenance and strengthening of coast protection works.

Morphodynamic Processes of Tidal Inlet and Ebb-Tidal Delta of Shuidong Bay

Based on the observed data in 1982 approximately 1985 at Shuidong Bay area, west Guangdong Province, the morphodynamic processes of tidal inlet and ebb-tidal delta in the barrier-lagoon system are presented, including the dynamic features of tides and in the tidal inlet, the regional dynamics and longshore sediment transport in the ebb-tidal delta, the genesis of the entrance bar, the recent erosion and deposition in the ebb-tidal delta and so on. The paper attempts to answer two questions, i.e., the stability of the tidal inlet and the feasibility of dredging on the entrance bar for the course of Shuidong Harbour. The results show that the stability of the tidal inlet is ideal and that dredging action on the entrance bar may be successful if dredging is deep enough and the course position reasonable.

An overview of seismic ground motion design criteria for transportation infrastructures in USA

This paper provides an overview of current seismic ground motion criteria for transportation infrastructures in USA. This is to facilitate an understanding of current seismic performance levels and design practices in USA for transportation professionals world-wide, especially those in Asian and Pacific regions. Seismic vulnerability of a transportation infrastructure is determined by the risk associated with the seismic ground motion and specified performance criteria. Determining an acceptable seismic risk is a very complex task that must consider both social and economic aspects. Obviously, the amount of risk that a railway bridge can accept may be different from that of a highway bridge. The economic tolerance in one country may be different from that in another country for the same type of infrastructure. In this paper, seismic performance levels and design criteria of ground motion for highway bridges, railway bridges and ports＇ container wharves in USA are reviewed, and design examples are presented to demonstrate how to develop the code-based and site-specific design acceleration response spectra and time histories.

EXPERIMENTAL STUDY AND APPLICATION OF VIBROFLOTATION METHOD AT SEA BOTTOM

The vibroflotation technique has now become a comparatively perfect method. However, the stone column driving at the sea bottom, which is liable to ebb and flood tides, is seldom tried abroad and has been tried for the first time at home. We have designed a set of construction techniques for driving and installing stone columns at sea. These techniques have been proved successful and highly efficient by practice. At the sea bottom were conducted three groups of large-scale loading tests and the allowable bearing capacity of the composite foundation was obtained as 130 kPa, against that of the natural foundation: 50 kPa. The allowable bearing capacity of the composite foundation showed 2.6 times as much as that of the natural foundation. Also obtained was the distribution ratio of stress, n = 3. The experience and indexes, obtained from the Yantai Harbour Project, have already been justified in the application in reinforcing the coastal highway at the Huaneng Power Plant of Fuzhou City, Fujian Province.

Wind-Wave Frequency Spectra of New Dalian Port

This paper, based on wave data measured with Type 956 Directional WAVE-TRACK Buoy System at new Dalian Port for a whole year, analyses the properties of the wave frequency spectra, and derives the formula for the frequency spectrum of wind-waves.

APPLICATION OF VACUUM PRELOADING IN GRAVITY PLATFORM DESIGN

Vacuum preloading has been widely used in harbour engineering to accelerate the consolidation of soft clay. The mechanism of the method is discussed in this paper by presenting a consolidation model under the action of negative pressure. A scheme of using vacuum preloading in designing a gravity platform is proposed to strengthen the soft clay layer on which the platform will be placed. Details of a drainage system are described and the functions of the system are also discussed.

MATHEMATICAL MODEL FOR WAVE DIFFRACTION WITH ARBITRARY RATE OF REFLECTION

The boundaries of a natural harbor or artificial harbor are very complex as far as its shape and reflection condition are concerned. The schemes available for solving wave diffraction in a harbor are not very accurate due to the simplification of realistic boundaries into a single jetty, a gap breakwater and a detached breakwater, neglecting the reflection effect of boundaries along the quays and the shore line whose shapes are rather irregular. Physical models turn to be quite helpful and valid in this case. In the present paper a mathematical model for wave diffraction in a harbor is introduced by using the singularity distribution method which can take into account the boundaries with arbitrary rate of reflection. The present model has been applied to the estimation of wave diffraction in the harbor basin of Guangdong Dayawan Nuclear Plant, and verifications with corresponding physical models are quite favorable.

MULTI-DIRECTIONAL WAVE SUPERPOSITION OF WAVE DIFFRACTION

Characteristics of a natural wave cannot be successfully described by only using wave frequency spectra. In the laboratory, natural wave conditions cannot be simulated exactly by a harbor sheltering experiment with irregular long-crested waves, especially since the results of diffraction tests with reflection source are often inaccurate. Only a small number of laboratories in the world have possessed a directional spectrum wave producer because of its complication and expension. This paper describes the experiment for multi-directional wave superposition of wave diffraction, with the conventional regular wave producer and one-direction irregular wave producer. The test results are of equal value with that from a directional spectra wave. This method is suitable for rational design of harbor engineering projects and can be adopted in future practice.

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution （QKD） system. A new idea is put up to design a quick single-photon detector. This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes （APDs）. All of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal. The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector. The single-photon prompt detection can come true for high repetition-rate pulses. The applying of this detector will largely raise the code rate of the OKD. and boost the commercial use.