Showing papers in "Hydro-Science and Engineering in 2013"

A study of sediment characteristics and riverbed erosion/deposition in Qiantang estuary

Abstract: In this paper,the distribution characteristics of sediment concentration and sediment grain size are introduced in brief,and the formulas of the sediment incipient velocity and the sediment carrying capacity in the estuary are establishedThe characteristics of the large variation amplitude of the riverbed,the rapid deposition after rapid erosion,the flood-induced eroding and the tide-induced silting in the upper reach,and the flood-induced silting and the tide-induced eroding in the lower reach are analyzedThe riverbed variation has a great impact on flood and tidesWhen tidal bore arrives,the flows of the tidal bore violently erode riverbed and result in sharply increased sediment concentration,which mostly reaches a peak value after twenty minutes,thus forming a high sediment concentration regionIn normal and dry periods,sediment discharge in flood tide is larger than that in ebb tide,resulting in silting in the upper reachThe tidal bore is one of the mechanisms for serious erosion and deposition of riverbed in the Qiantang estuary

Current situation and future prospect of dredged material disposal in the Yangtze estuary deepwater navigation channel

Abstract: There is a large amount of dredged materials produced stably in the Yangtze estuary deepwater navigation channel.How to dispose these dredged materials is a major technical problem in the field of port and waterway engineering.Using lots of engineering field data and proceeding from the basic features of the dredged material of the Yangtze estuary waterway,the current situation of disposal modes of dredged material is analyzed and compared,and a future development mode of dredged material under the new situation is presented.Major studies have shown that the dredging disposal modes at different stages of the Yangtze estuary deepwater channel regulation project can basically adapt to the characteristics of dredged materials under the conditions of corresponding dredging depths,and generally speaking,the dredged materials are still mainly dumped to the marine dumping sites.With the new situations such as the limitation of ocean dumping sites,the increasing demand of sediment resources supply and the erosion threat to the Yangtze estuary tidal wetlands,the principle should be followed that dredged material be used more and discarded less.And there are many kinds of ways of beneficial use of dredged materials including the blowing of dredgerfill to reclaim land and the feeding of sand for wetland protection,which will be the future development direction of dredged material disposal in the Yangtze estuary deepwater navigation channel.

A study of wave-current force acting on large scale cylinder structures

Abstract: Large scale deepwater structures often face some complex natural conditions such as deepwater,large wave height and strong current,and are subject to considerable horizontal wave-current forces.It is necessary to accurately consider the size of the wave-current forces in the engineering design.A series of wave-current forces experiments for cylindrical,square columns and rectangular columns are carried out in the wave-current flume.At the same time,boundary element method for solving the wave loads on a large scale cylinder is used,and the preparation of Fortran program is made.Comparing the model results with the calculated values,an engineering method for calculation of the wave-current forces is developed: for deepwater large scale cylinder structures,wave-current forces can be obtained by the wave force linear superposition current force multiplied by 1.04,wave element is considered under the influence of current,and current force is calculated by flow around cylinders theory.By using this method to calculate wave-current force,and comparing the physical model results,the error is relatively small,and the model accuracy satisfies the requirement of engineering design.

Tests and evaluation of structural concrete durability at Ningbo marine wharf

Abstract: In order to study the influence of environment factors on the structural concrete durability,the durability properties of concrete at different structural regions of the working platform of a marine wharf in Ningbo are tested.The test results show that the carbonation depth and the characteristic value and designed value of bar protective layer thickness change from high to low,namely those in the atmosphere zone are greater than those in the water level fluctuating zone,and those in the water level fluctuation zone are greater than those in the underwater zone.The change in the apparent chloride concentration and alkali content of the concrete is: that in the underwater zone is higher than that in the fluctuating water level zone and that in the fluctuating water level zone is higher than that in the atmosphere zone. In terms of the apparent chloride diffusion coefficients,the fluctuating water level zone is greater than the underwater zone and the underwater zone is greater than the atmosphere zone. Concrete in the atmosphere zone is much exposed to CO2,which results in deterioration of the protective layer thickness. The combined action of chloride ion with CO2erosion leads to deterioration of the protective layer thickness in the fluctuating water level zone. The limitation of operation time and bad environment lower the ability of reinforced protection,and a faster steel corrosion and the deterioration of the layer thickness can be found in the underwater zone.

Prediction of seawall settlement based on ARIMA-RTA model

Abstract: Analysis and prediction of seawall foundation settlement are very important for engineering maintenance and disaster prevention,but there is no unified analytical model because of too many factors influencing the settlement. Based on the seawall monitoring data,the paper makes full use of the good fitness of Autoregressive Integrated Moving Average Model( ARIMA) and dimension-fixed and cursion-compensated idea of Realtime Tracing Algorithm( RTA),and a new model named ARIMA-RTA is developed. As a test,the prediction model is applied to calculating a case of the seawall monitoring data,and the results show that the model has carefullydefined physical conception and thus opens up broad prospects for application to engineering data analysis for high precision and noise immunity.

Hydraulic characteristics of backward-facing step flow based on k-ε turbulence model

Abstract: The backward-facing step flow is a simple structure but has complex flow patterns.In this paper,the backward-facing step flow is simulated by a 2D k-e turbulence model.And based on the test results measured by PIV system,we analyzed the flow field data of the backward-facing step for Reynold number from 500 to 50,000.The research results show that the flow field structure has a steady recirculation zone,and that the length of the recirculation zone increases rapidly with the increace of Re in the front,then rapidly declines,and finally slowly rebounds and becomes stable.The cross section velocity is affected greatly by the recirculation zone,and the peak value decreases slowly with the increase of Re.The pressure and turbulence kinetic energy are also affected by the recirculation zone,but the turbulence kinetic energy is less affected in low Reynolds.

3-D numerical simulation of flow in natural meandering channel

Abstract: In order to study the flow movement,bed evolution and sediment erosion and deposition of the natural rivers,a 3-D numerical model is established in body-fitling coordinates by a finite volume method,and SIMPLEC algorithm is used to calculate the 3-D velocity fields. The simulated results of the model are compared with the measured data. The findings indicate that the calculated results agree well with the measured data and reflect the 3-D flow characteristics in the natural meadering channels. The surface water particles will move towards the concave bank,while the bottom water particles will be towards the convex bank. It is shown that the model can be used to simulate the flow movement along the natural meadering channels.

Experimental studies on influence factors of permeability coefficients of coarse-grained soil

Abstract: The permeability coefficients of coarse-grained soil are closely related to soil types, material composition,grain composition,particle shapes and density. Based on laboratory tests,the effects of particle shapes,grain composition and density on the permeability coefficients of the coarse-grained soil have been studied. In order to analize these influencing factors,nine groups of constant head experiments are designed by use of orthogonal test approaches. The influences of three factors on the permeability coefficients of the coarse-grained soil are determined by range analysis and variance analysis. Research results show that the permeability coefficients are increased with increasing of grain composition characteristic value d 20 and increasing of curvature coefficient Cc, and decreased with increasing of dry density and increasing of sphericity.

A study of concrete early mechanical properties

Abstract: The concrete mechanical properties of 1 d-7 d have very important effects on the durability of concrete structure.In order to explore the early mechanical property law of concrete,the mechanical properties of concrete in the first seven days are tested on the basis of four proportions.The research findings and conclusions are as follows:(1) the growth rate of cubic compressive strength,axial tensile strength,splitting tensile strength and ultimate tensile strain of concrete in the first three days is higher than the growth rate in 3 d～7d;(2) the axial tensile strength of concrete is greater than its splitting tensile strength in the first seven days;and(3) the pressure ratio of concrete based on splitting tensile strength and the pressure ratio of concrete based on axial tensile strength both tend to decrease firstly and then increase slowly,but the pressure ratio of concrete based on splitting tensile strength is greater than the pressure ratio of concrete based on axial tensile strength.

Experimental simulation and validation of the tidal bore in the flume

Abstract: The frequencies of the transverters at both ends of the glass flume which control the flows of water pumps are adjusted to create a steady water depth and ebb velocity before the tidal bore arrival.Under this condition,the different frequencies of the downstream transverter have been used to produce the tidal bores with various heights.And the celerities,bore heights,vertical distributions of the velocities and bore shapes of the tidal bores have been measured under different water depths and ebb velocities before the tidal bore arrival with various tidal bore heights.The comparisons of the experimental results with the field data at the Yanguan reach in the Qiantang River Estuary in October 2010 show that the experimental results have agreed well with the measurements on site,which indicates that successfully simulated tidal bores in the flume demonstrate that the flume experiment is a good tool to study the tidal bore.

Remote sensing mornitoring and environmental impact analysis of reclamation in Caofeidian sea area

Abstract: Detection of the coastline change caused by reclamation projects and hydrodynamic environmental impact analysis of the Caofeidian sea area for nearly 20 years are conducted by means of ArcGIS,and using 4 satellite images including Landsat TM and HJ-1A /1B,and the underwater geomorphologic map in 2003Analysis results show that in the first 10 years,the coastline advances slowly,and the maximum distance to the sea in some areas is only about 13 km;and the reclamation scale is small,and is more limited within 0 m contourThe coastline has advanced towards the sea significantly in the last 10 years,and the reclamation area has been deepened into the 0 m contour but within the-5 m isobathThe current reclamation has little impact on the hydrodynamic environment aroundDeep troughs show good stability though there is scouring and silting between the internal and external of offshore barsAccording to the reclamation plan for the next decade,there is a need to strengthen the monitoring,including remote sensing meansResearch of cumulative impact of several reclamation projects in Bohai Bay on the Caofeidian sea area also should be carried out in the future

Finite element analysis for a wing wall of a large scale dock in construction period

Abstract: The wing wall with anchor rod is widely used in the large scale dock.But there are varieties of assumptions which are introduced in the calculation of the dock structure,so that ideal answers can′t be obtained.In order to find out the characteristics of deformation and force of the wing wall,this paper focuses on the realities of the wing wall engineering in Qidong Fengshun dockyard.Finite element calculating models are set up to calculate the displacement and stress of the dock wall structure for typical working conditions respectively with the aid of the large-scale software MSC.Marc and a sufficiently large foundation is selected to reduce the impact of the foundation.Then the calculation results of the finite element method are compared with the measured data to analyze how the construction process affects the force of the wing wall.The anchor structure can enhance the stability of the system by reducing the horizontal displacement of the wing wall and effective stress of solum and concrete structure effectively.The stress that part solum was originally subjected to give by the load difference before and after the wall almost through the steel bars are transmitted to anchorage pile bear after the system had been formed.Thus the dock chamber wall and overall deformation are significantly improved.

Simplified methods for reliability index calculation of gravity quay stability without wave force

Abstract: The simplified methods for reliability index calculation and design of the gravity quay against sliding and overturning without wave force is investigated in the study. Probabilistic distribution and statistical parameters of the load and resistance regarding sliding and overturning are established through Monte-Carlo simulation and statistical analysis; and the simplified methods and expressions for the reliability index calculation of the gravity quay against sliding and overturning are put forward. Coefficients in the simplified reliability index expressions are determined through reliability analysis of 11 block quays,8 buttressed quays and 25 caisson quays using JC method. The research results indicate that for the same type of the gravity quay,the bias and variation coefficients of the load effects and resistances for sliding and overturning are approximately identical. The results of reliability index obtained by simplified expressions are very close to the results obtained by JC method.

A real-time dynamic coupling model for flood routing and its application to flood risk charting

Abstract: Floods caused by dike break and overtop can be simulated with a dynamically coupling model of 1D and2D hydraulic model Generally,the traditional 1D and 2D flood routing models are operated separately Moreover,the traditional model would take a great amount of time to simulate,and the given results are not accurate In this paper,a 1D-2D dynamic coupling model for the flood routing is developed through time synchronization and corresponding of space nodes According to dry depth and wet depth theory,the traditional flood routing model is optimized,which saves much time for simulation An example of Guduiwei flood detention basin is shown for rerifying the 1D-2D dynamic coupling model Historical floods are simulated with the 1D-2D dynamic coupling model,which has verified the correctness of the model Based on the results,a flood risk chart is established with standards The results show that the 1D-2D dynamic coupling model is reasonable in simulating dike break-induced floods with much time saved