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Scientific bases A. Look-up tables for wave parameters in each cross-section along the coastline from Quang Ninh to Kien Giang B. Determination of dike crest freeboard as per design wave run-up D. Distribution of wave pressure on dike slope E. Negative wave pressure wave uplift pressure E. Types of soil foundation F. Determination of counter-pressure footing dimensions F.
But fc 3: But ic 4: Sa u khi lo? C ac nghifp vu phat sinh trong ky: Y eu cau: Xac djnh so du- cyoi ky cua c ic Tai khoan. Chiromg 3: Phan anh gia trj tai san hi? Phan anh gia trj ngudn vSn hi? B iitip 3: Hay dinh khoan cac nghiep vu kinh te phat sinh trong ky cua doanh nghiep. H in g hod: B ii tip 5: T ii khoan Trong Qui 2 nam c6 cic nghifp vy kinh te p hit sinh sau: Ye u cau: Related Papers. Principal failure mechanisms of sea dikes and revetments in Vietnam N.
Details of some dike slope protection elements N. This guideline is applied in designing new sea dikes, rehabilitating and upgrading various types of sea dikes and other related structures, such as: - Dikes protecting populated areas, coastal economic areas aquaculture, salt fields, tourism etc.
General bases and principles of sea dike design Conforming with the current regulations of Construction Investment Project management and provisions: - Law on Dykes and dyke-maintenance - Law on Basic Construction - Master plans for socio-economic development and natural disaster prevention and response in the area;, plans for coastal transportation and other related plans; - Applying other concerned Codes and Technical standards; - Applying new achievements of science and technology which are suitable for the dike conditions in Vietnam; - Active loads are calculated as per current stipulations in Hydraulic works design; - The elevation system and coordinate system used in sea dike design is the National Elevation System; - Technical solutions: Combination of structural and non-structural 20 21 solutions; appropriate to the scenarios of climate change impacts must be applied.
Safety standard is determined on the basis of risk based optimal results taking into account economic risk, potential loss of life in the protected area and the investment capability into consideration.
Safety standard is determined on the minimum acceptable value of flooding occurrence probability of protected area. It isn t homogeneous with structure incident probability and elements.
Structure safety have to observe by followed safety coefficients of Codes and Law in basic construction. Based on the features of protected area, safety standard SS is determined by following special characteristic protected region: Characteristic protected Region of Type 1: is coastal regions which have no potential inundated due to local rain or due to upstream rain water coming down.
SS for the Region of Type 2 is defined as per Table 3. Table 3. If the industrial rate is greater, then it is a developed industrial area and vice versa.
Then the two criteria are considered in order to determine the safety standard. In case the protected area meet only one criterion, the level is lowered by one. The spatial planning must take the planning for socio-economic development up to and vision for into consideration.
In addition, dike grade can also classified by potential inundation depth of protected area see Table 3. The construction volume and the capital cost should be compared in order to select the most appropriate dike route; - In case the dike route must be in concave shape, appropriate solutions to wave attenuation or dike resistance strengthening need to be adopted; - No weak chain links created at the connection with other nearby structures and no impacts on relevant areas; - In case of rehabilitated and upgraded sea dikes, the aforementioned requirements must be considered in order to adjust locally necessary sections.
This will help to narrow down the damages in case of failure of the main dike Dike route at the eroded coasts ingression General requirements - At the eroded coastal areas, the dike route is usually damaged due to the direct impacts of waves on the dike body, failure of outer slope and dike toe.
In this case, the evolution of the coastline, mechanism and causes of the coastal erosion and other influence factors need to be studied thoroughly in order to decide the appropriate alternative; 30 31 - Consideration of dike route must be related to the solutions for erosion restraining, accretion facilitating and foreshore stabilizing; When there are no eroding mitigrating solutions, - dike route position must comply with set back line of the region on basis of expected life time of the dike system.
Apart from the main dike, space must be reserved for dike set back. The secondary dike route can be built in combination with non-structural approaches in order to minimize the damage in case the main dike route has been destroyed Main dike route As per Article 4. The distance between them is at least 2 times of the design wave length.
Requirements of sea dike cross-section design General requirements Appropriate design cross-sections of sea dikes and other related structures on each section of sea dikes must be selected on the basis of geological conditions of foundation, embankment materials, active external loads, construction plan and service requirements.
In case the existing sea dike system is upgraded and rehabilitated, the cross-sections of current and supplementary dike routes must be appropriated to the natural conditions Technical requirements The most important requirements of sea dikes and revetments is the reliability in withstanding storms and floods, also coping with the problem of sea level rise as a result of global climate change.
In addition, sea dikes and revetments must be appropriate to local natural conditions in each area.
Attention should be focused to the selection of optimal cross-section of sea dikes and revetments in order to satisfy all of the above-mentioned requirements Environmentally-friendly requirements The design cross-section of sea dikes and revetments must be environmentally-friendly with appropriate structural solutions without disrupting the nearshore marine ecology as well as the local landscape, especially in case of the coastal tourism and densely populated areas.
Selection of a cross section must depend on the topographical, 34 35 geologic, hydrological and oceanographic conditions, as well as construction material, construction conditions and service requirements in order to analyse and decide. Some types of sea dike cross sections which can be selected are shown in Fig. Dikes in combination with transportation routes k.
Environmentally-friendly dikes superdikes Figure 5. Figure 5. Contents of sea dike design are as follows: 1 Design of crest level; 2 Design of dike body; 3 Design of filter layers; 4 Design of slope protection layers; 5 Design of toe protection; 6 Design of dike crest structures; 7 Design of crown wall if necessary ; 8 Design of transition structures; 9 Stability calculation Determination of dike crest level Crest level of sea dike is defined as the elevation of the dike crest after the 36 37 settlement has become stable.
The following notice must be taken when defining the dike crest level: - In the same dike route with different dike crest level at different segments, the highest level must be chosen as design level for the entire route; - In case the strong and stable crown wall is placed on seaward side, the dike crest level is that of the crown wall.
Methods for the determination of each term in the formula for dike crest level design in each specific case will be given in the following sections. The sea dike system is designed to protect urban areas with grade III and service life of 50 years.
The frequency curve of storm surge heights is established on the basis of observation data in a sufficiently long duration, at least 40 years. In this case, 1-D hydraulic model must be employed in order to determine the combined water levels of riverine and coastal factors. Boundary conditions of seaward water level are determined according to Section Riverward boundary condition is the water level and flood discharge in the river, in which the flood frequency corresponds to the design frequency Determination of required freeboard H lk : Seaward frontal dikes with no overtopping Seaward frontal dikes withstand direct impacts of waves on the outer slope, thus the required crest freeboard H lk is determined on the basis of wave run-up height.
In case no overtopping allowed, H lk is defined as the height of design wave run-up. This can be considerd a specific case, in which the allowable 40 41 overtopping discharge is very small, inconsiderable and, or non-overtopping waves.
In this case, the inner slope and crest of sea dike can be protected only by normal grass if no more specific requirement is considered. In addition, the selection of design overtopping discharge must take damage extent and impacts on the landward areas in case of design overtopping discharge. Allowable overtopping discharges are given in Table 5.
Based on this, the alternatives to protect the inner slope of sea dike, as well as the collection, storage and drainage of overtopping water can be proposed. Table 5. In case of openly-enlarged estuaries under impacts of waves, the determination of crest freeboard with reference to Design Water Level is performed in a similar way as given in Section or However, the wave parameters wave height and wave period used in design is the results of computing wave propagation from deepwater boundary to the construction sites in the estuarine areas.
In the design of dikes surrounding large estuaries or in combination with frequent navigation, the impacts of locally generated waves at the estuarine areas must be taken into consideration, such as: locally wind-generated waves see details in Appendix C or ship-induced waves etc. When the local wave height in these areas due to above-mentioned reasons is greater than or equal to 0.
In other cases when the impacts of the waves from the sea on the construction locations in estuarine areas are inconsiderale less than 0. The required crest freeboard H lk can be neglected in this case.
The wave parameters at the dike toe is determined by means of the propagation of design deepwater waves to the study location. In case the design dike route is shielded by the mangrove forests, waveattenuating effect of mangrove forests must be taken into consideration in the computation of wave propagation as explained in Section 8.
In this case, the design wave parameters at the dike toe include the impacts of mangrove forests. Due to difficulty and high costs in topographic survey and measurement, the representative crosssection and the available bathymetry can be combined in order to interpolate the depth contour or depth points down to 20 m deep so that the correct input wave parameters are in deepwater area.
In addition, other wave-propagating models are also recommended for the purpose of calibrating and comparing the results. For example, the graphic methods proposed by GODA and OWEN applicable to the foreshore slope in the range of to for gentler foreshore, the results achieved in case of foreshore slope of can be used. Design deepwater wave parameters at different locations along the coastline of Vietnam can be determined as a reference in Appendix B Section B Furthermore, for the purpose of comparison, the design wave parameters at the dike toe in each location in different cross-sections along the coastline of Vietnam can be directly determined according to Appendix B Section B In case the dike crest also functions as transportation route, it must be designed as per the technical standards of road ways see TCVN.
If not, protective solutions against erosion due to rain water and overtopping water must also be adopted. Transitional parts must meet the technical and aesthetic requirements.
The selection of preliminary slope coefficients of sea dikess must be examined by means of stability calculation and wave run-up height, from that appropriate values can be determined. However, if the outer slope is too gentle, the construction volume will be enormous.
Therefore, in case of large sea dikes, the selection of appropriate slope coefficients is usually performed by means of technical and economic analyses.
If the dikes are embanked on soft soil foundation, berms can be placed on both slopes for high dike body and for the purpose of stability enhancement. These berms can fulfil the requirements of transportation, maintenance and flood control Outer berm Seaward dike berms or wave-attenuating berms are applied in the areas with severe conditions of waves and wind in order to reduce the wave run-up height and to enhance the stability of dike body.
Outer dike berms are usually introduced at the Design Water Level. The width must be greater than 1. On outer dike berm, wave-attenuating blocks can be placed in order to attenuate wave run-up, to dissipate wave energy in front of dike crest, to enhance the stability and safety of the design dike route.