Statistic Analysis of the Annual Extreme Wave Parameters for the Coast of China

According to the need of project design for offshore engineering and coastal engineering, this paper statistically analyses the annual extreme data of waves acquired at 19 observation stations along the coast of China. Five kinds of distribution curves are adopted: Pearson III (P-III), Log-Extreme I (LE), Log-Normal(LN), Weibull(W) and Exponential Γ(EΓ) to check the adaptability to the long-term distribution of annual extreme of wave in the China Sea areas. The New Curve Fitting Method (NFIT) method and Probability Weighted Moments (PWM) method are used to estimate the distribution parameters and thereby to derive the design wave parameters with different return periods at 19 observation stations. The test results show that by combining EΓ distribution and NFIT parameter estimation and optimum seeking by computer, the design wave parameters can be estimated with high accuracy, high speed and high efficiency, and the randomness of the estimated results can be avoided.

Tracing Method of Natural Sediments by Neutron Activation and Its Application

A new method of Neutron Activation Analysis (NAA) for sediment movement study is presented in this paper. Through analyzing the natural sediment, the information about natural tracing agents has been obtained, which can show the direction of sediment movement and relative discharge of sediment transportation. Test results in some areas, such as Shanton Harbour and Hangzhou Bay, are in good agreement with those from normal hydrologic measurements and some results are not obtainable with the latter. The NAA is economical, practical and reliable, and should be widely used in engineering practice.

Water Wave Refraction and Diffraction over Frictional Topography

This paper considers the effect of wave energy dissipation induced by sea-bottom friction on the computational results of water wave refraction and diffraction with the parabolic equation method. The presented results show that the friction factor formula adopted in this paper is of higher numerical accuracy than that introduced by Dalrymphe (1984), and it can be used to compute wave propagation over large open areas.

SOIL PILE INTERACTION UNDER STATIC, DYNAMIC AND CYCLIC LATERAL LOADS AND A PROPOSAL OF p-y CURVE FORMULA

In this paper, the studies on soil-pile interaction behaviors in saturated sands under static, dynamic and cyclic lateral loads by model testing are described. By comparing with the field test results for piles in soft sandy clay, a formula of p-y curves based on constitutive relationship of soils applicable for both sandy and soft clays is proposed. Good agreements are obtained in comparison with the field test results performed by other investigators abroad. A p-y hysteresis curve formula based on the modified Masing's doubling criterion is also proposed, and the results are in satisfactory agreement with field test results.

SYNTHETIC ANALYSIS OF IMPACT LOADING OF SHIPS IN REGULAR WAVES ON PIERS

In this paper, the results of model tests of impact energy and forces and motions of moored ships from 20,000 dwt to 200,000 dwt in regular waves upon piers are synthetically analyzed. Based on the concept of wave energy transmission and the theory of vibration, a semi-empirical formula for evaluating impact energy and forces is proposed.

SOME REPAIR EXPERIENCES FOR REINFORCED CONCRETE STRUCTURES IN SEAPORT WORKS

Owing to the reinforcement corrosion, freezing action and external mechanical attack, some reinforced concrete structures of seaport works in China have been suffering severe damage. A survey showed that more than 40 reinforcement seaport structures and tide barriers had been damaged so that they had only a service period of 7 - 25 years. Therefore, the repair task is difficult. In the present paper, some principles and methods for repairing the reinforced concrete seaport structures are provided and some related technical requirements and materials as well as their preparation and properties are recommended.

CALCULATION AND PREDICTION FOR MUDDY BEACH PROTECTION AND SILTATION ACCELERATION

This paper firstly deals with the two different siltation patterns with siltation accelerating project on sandy beach and muddy beach, and then puts forward the calculation method for siltation of the project on muddy beach based on the behavior of suspension and settlement of fine sediment particles. This method not only can qualitatively explain quite a number of natural phenomena, but also is examined by practical projects. Therefore, this method is of important practical significance in the practice of foreshore reclamation and beach protection as well as siltation acceleration.

SILTATION INVESTIGATION IN LIANYUN HARBOR BY USING γ-RAY DENSITY GAUGE

The principle, method and mersuring equipment in studying siltaton in the Lianyun Harbor by using the γ-ray density gauge are described in this paper. From field observation and analyses, some primary principles concerning the infill rate, the distribution of silt density with depth and the consolidation rate and change of the shear strength of the silt have been found out.

Computation of Diffraction of Irregular Waves Behind Single Jetty

This paper presents a calculation method for the diffraction of both regular waves and irregular waves of the single directional frequency spectrum behind a single jetty with a theoretical analysis, which has been confirmed through the model experiments, derives a method of computing the diffracted irregular waves behind the single jetty with the theoretical analysis on the basis of computation of the field data and gives the formulas and the figures of the computation of wave diffractions behind the vertical wall or mound single jetties.

Model Study of Permeable Caisson Breakwater with Slanting Slabs

This paper describes the design of a permeable caisson breakwater with slanting slabs (Types I and II) and presents some preliminary experimental results, together with relevant figures and tables. Analysis is made of the reflection coefficient, transmission coefficient, acting wave pressures, water jetting at the crest of the breakwater, and wave overtopping. Experiments show conclusively that this type of breakwater has the advantages of light dead weight, good wave-absorbing performance, low coefficients of reflection and transmission, and small wave overtopping.

CALCULATION OF TWO-DIMENSIONAL TIDAL CURRENT AND ANALYSES OF EROSION AND SILTATION IN BEILUN HARBOR

ADI method is adopted to establish a two-dimensional tidal current numerical model for Beilun Harbor based on the hydrologic data and sediment data. The current conditions of the site where the second stage project is going to be carried out are described. The analysis and calculations for the deposition and erosion in the harbor basin are performed, which provides references for the construction of the harbor. The effect of the pile group on the current is simulated by increasing the sea bed roughness which can be determined with empirical equations of artificial roughness. The method is considered to be applicable after verification with field data. The test has provided experiences for future mathematical modelling to simulate the open type hydraulic structures.

NONLINEAR INTERACTIONS OF SQUARE CYLINDERS AND WAVES

The integration equation and time stepping method have been applied in this paper to discuss the nonlinear wave forces and moments acting on a square cylinder subjected to nonlinear waves based on the stream function theory. It is shown that the present results are in good agreement with the experimental ones. Some numerical results and an empirical formula are presented.

EFFECTIVE WIDTH AND DISTRIBUTION COEFFICIENTS OF MOMENT IN RC CONTINUOUS SLABS

Using effective width of load and distribution coefficient of moment is a kind of simplified method in the design of continuous reinforced concrete slabs, which is widely used in engineering design. In this paper, through the analysis of load-bearing states of continuous slabs restricted by the main beams under concentrated loads, the effective width of load and distribution coefficients of moment of a continuous slab are obtained with the principle of equivalent loads. On the basis of the data of a 5-span continuous reinforced concrete slab, the formula of effective width is deduced and the distribution coefficients of moment for the mid-span and supports are given.

PHYSICAL AND MATHEMATICAL MODELS OF POLLUTION DISPERSION IN THE YANGTZE ESTUARY

The method of combining a physical model with a mathematical model is described to study the concentration profile of pollutant dispersion in the Yangtze Estuary. the Experiments are described regarding a jet in a tidal physical model and two-dimensional calculations of diffusion using momentum and mass conservation equations of unsteady flow. The feature of dispersion in the tidal flow, which is different from that in the steady flow such as rivers, is explained. Dilution and dispersion mainly depend on the volume of runoff and tidal range. The results of the measurement and calculation are presented, and it can be seen that they are in good agreement.

SIMULATION AND ANALYSIS OF WAVE GROUPS IN A WAVE FLUME

Using the trial-error method, for a given wave spectrum, wave trains with different wave groupness, which is defined by the groupness factor GF have been simulated in a flume. The statistic characteristics are analyzed for some of these wave trains in this paper.

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.

Effects of Irregular Wave Groups on Pile Forces

The wave forces on 1,2 and 4 vertical circular piles under the action of several wave trains of the same wave parameters, such as Hs Tp and Mo, but different wave group factors GF are measured in the laboratory. After comparing these forces, it may be concluded that the mean and significant wave forces are almost of no difference for the wave trains with different GF. When GF is larger, the one-tenth of the wave force extreme is slightly increased and the maximum wave force is much larger than the ones with smaller GF, to which attention must be paid in engineering practice.

SETTLING TESTS FOR TRACER PARTICLES IN STATIC WATER

The production of fine sediments coated with radioisotopes to act as a tracer in studying the movement of dredging spoil involves some physical and chemical treatment of the sediment. The treatment can affect the electrochemical properties of the sediment and hence its behaviour in fresh and saline water. The effect of these changes on the degree of flocculation of the sediment has been studied by measuring the fall velocity distribution in a 4.4m settling column. The results of these tests show that the coating of inactive gold or silver on to natural sediment without any other pretreatment results in a tracer sediment having fall velocities similar to those of natural sediment. Other pretreatments result in variations in the fall velocity distributions owing to different degrees of flocculation induced by the chemical treatments. An artificial sediment consisting of finely ground scandium glass was also tested for comparison.

Long Waves Induced by Wave Groups over a Trench

The second order long waves of the mean water free surface displacement induced by the wave groups over a trench are discussed in this paper. The incident wave groups are supposed to be superposed by 2 linear waves with different amplitudes, phases and slightly different frequencies. Some of the theoretical formulas and numerical results are presented.

HYDRAULIC PERFORMANCES OF SKIMMING FLOW OVER STEPPED SPILLWAY

Hydraulic performances of skimming flow over stepped spillway was studied by means of hydraulic model experiments. The stepped spillway is a modification of the WES (Water Experiment Station) standard spillway. The experimental results indicated that the stepped spillway is more effective at dissipating energy, the dissipation ratio decreases with increasing discharge, and the free surface air entrainment on stepped spillway occurs much more upstream than on smooth spillway.