Guideline for QCVN xxxx : 2013/BXD

lch: Characteristic length (m) (= GF ×Ec / fck 2 ) ; Ec : Modulus of elasticity (kN/mm2) ;

GF : Failure energy (N/m) (=10×(dmax )1/ 3 × fck1/ 3 ) ; dmax : Maximum size of coarse aggregate (mm) ;

f’ck : Compressive strength (N/mm2) ; and

ftk : Tensile strength (N/mm2) ( ftk = 0.23× f 'ck 2 / 3 )

As shown in the above formulae, bending strength varies with compressive strength of concrete,f’ck , maximum size of coarse aggregate, dmax , and height of component, h.Assuming dmax as 20mm, and h as 0.20m and 1.00m, Table 8 is revised as follows.

Table 8 – Example of calculated minimum bending strength of concrete structure corresponding to its compressive strength

Major technical standards and codes regarding concrete are as shown in Appendix D.

7.2Reservoir

7.2.1. Technical Regulation Article 7.2.1 describes the requirements for reservoirs.

Technical requirements are described quoting provisions of Articlef QCVN8.1o 04 - 05 : 2012/BNNPTN.

8.1 Reservoir

8.1.1General regulation

8.1.1.1 Apart from stipulations in the article 4, the following requirements should be met in the design calculation for a reservoir:

a)Supply enough water according to the water consumption diagram and the committed guarantee level of water supply;

b)Obtain enough flood-prevention volume so as to guarantee the flood protection requirements for downstream and for the construction itself when the design floods and checked floods occur.

A reservoir shall have effective capacity to supply sufficient amount of water to users and flood control volume in case a dam has a floodcontrol function. A daily, monthly andannual reservoir operation plan shall be prepared to satisfy demand of each water user and capacity for each water user shall be allocated after due consultation with water users.

8.1.1.2 The sedimentation volume of a reservoir is considered to be filled when the surface elevation of settled sediment in front of the pressured alignment equals the sill elevation of the major receiving

gate. The exploitation time, calculating from the first year of storage until the time when the sedimentation volume of a reservoir is filled, is not lower than stipulations in theable 11 in case of

normal working condition.

A reservoir shall have sedimentation volume according to its class as shown in Table 11of QCVN 04 - 05 : 2012/BNNPTN below:

8.1.1.3 In case there is an abundance excess water volume in flood flow, the sluicingoutlet should be considered to place in order to reduce the sedimentation volume and increase the useful volume. This

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culvert is combined with the additional task of constructional diversion and water discharge if a reservoir faces with failures.

Sufficient amount of inflow can be used forsediment flushing, and a sluicing outlet and reservoir operation plan for sediment flushing shall be prepared.

8.1.1.4 Flow, velocity and operating regime of the sluicing outlet dependon the characteristics of discharged sludge, allowanced extraction rate of a reservoir in order to guarantee to remove settled sludge in front of a culvert to downstream without the falling problems of inclined earth work and side slope.

Specifications of a sluicing outlet andsediment flushing operation plan shall be established after due investigation of characteristics of sediment.

Table 11 – The allowance time for the fill of sedimentation volume of a reservoir

8.1.2Calculation requirements to determine typical water levels of a reservoir

8.1.2.1Death level

The death level of a reservoir must guarantee the normal exploitation condition, is required to store the whole volume of settled sludge during the exploitation time stipulating in the table 11. It must also have stably hydraulic state through the intake works and provide enough water for water consumers:

a) Regarding to a reservoir having only one task of water supply (without electrical generation task): the death level must ensure to store the whole sludge settling during the exploitation time, which is

b)Regarding to a reservoir having only one task of electricity generation: apart from requirements stipulating in the point ‘a’ of this article, the death level must satisfy the technical and economic conditions of hydro-electric equipment: working at that elevation, turbine will operate normally and

in the allowed efficiency zone. The death level can be higher on the ground of optimum calculation for economy and energy;

c)Regarding to a reservoir having water supply and electricity generation tasks: stipulations in point

a and b of this article must be implemented;

d) Regarding to a reservoir having the additional task of aquaculture: apart from regulation in the point c of this article, the death level must satisfy the normal grow and development condition of kept species;

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Guideline for QCVN xxxx : 2013/BXD

e) Regarding to a reservoir having the additional task of tourist and convalescence: apart from requirements stipulating in the point c of this article, the death level must be maintained at the necessary elevation to guarantee the tourist landscape;

g) Regarding to a reservoir having the additional task of navigation: apart from requirements stipulating in the point c of this article, the death level must satisfy requirements of adequate depth,

that guarantees the normal operation of the largest allowed load of water transportation during the dry season.

The dead water level of a reservoir shall be established considering the purpose of the reservoir.

8.1.2.2 Retention level

A reservoir is guaranteed to have required volume at this water elevation to provide enough water to meet the demand of consumers in accordance with the water supply guarantee level.

The retention water level shall be established considering water demand.

8.1.2.3 The maximum design level and maximum examined level

In case of discharging the design floods and checked floods, the water level in a reservoir does not excess the maximum design and examined level. These two water elevations of a reservoir are determined basing on the flood regulation in the storage volume above the retention level. If there is

a flood prevention volume, this water elevation is determined on the ground of the flood regulation in the storage volume above the flood-prevention level. The discharge flow through constructions in the pressure alignment of a reservoir must be calculated basing on the most disadvantage flood model regarding to the peak flow or the mass volume of flood and in accordance with the occurring ability of compound floods as a result of storms (if occurred in the project area).

The design flood level and check flood level shall be established

8.1.2.4 Flood prevention level

Regarding to this elevation, a reservoir will obtain adequate volume to implement the flood control task for the construction and downstream in accordance with the design frequency. Depending on the specific conditions, the flood prevention level can be equal or lower than the retention level or even equal the death level.

In case a reservoir has a flood control function, flood control volume shall be establishedconsidering a share of reservoir capacity for each purpose and the reservoir water level shall be lowered to the level which can store designated flood inflow before the flood season.

8.1.3Determination of the in-undated boundary causing by a reservoir

Constructions placed in the reservoir area from the retention level to the maximum examined level

contact with water) in order to make decision for migrant or protective options or allowance for submergence. Applicable solutions for the undatedinareas and man-made constructions in the submerged zones must be in accordance with the design flood but not higher than the frequency of 1%.

An inundated boundary of a reservoir shall beprepared between the retention water level and the check flood level.

8.1.4Requirements for the environmental assessment

8.1.4.1The design for construction of reservoir assures requirements on the environmental protection regarding to current provisions.

8.1.4.2The design and construction of a reservoir must assess and evaluate negative impacts

and suggest protection or relief solutions for below disadvantages:

a) Physical damage causing by floods such as land loss especially agricultural land, losses of natural conservation area, specialized forest, mineral resources, socio-economic infrastructure, geographic

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name, historical and cultural monuments and famous landscape as well as the extinction of exhausted fauna and flora species;

b) It can lead to the reduction or loss of residential areas, which have been settled stably for hundreds

of years. There are security, society and defense disadvantages as well as hazard consequences resulting from the broken dam, which can occur in the future;

c)The reliability and feasibility of the migrant and-srettlement activities so asto guarantee the better living conditions in all aspects in a new living areas comparing to the old ones;

d)Downstream area can be influenced by the changes of flow and sedimentation regimes; Forecast the impacts of these changes to the riverbed, dikes or estuaries;

e)Assessment on the socio-economic and environmental benefits after the construction.

floristic composition in the catchment area to guarantee the water quality in a reservoir during the management and exploitation periods.

A hydropower and water use project shall follows andlaw ordinances regarding environmental preservation, and an environmental impact assessment shall be conducted and a social safeguard program and compensation plan shall be established.

8.1.6 Exploitation in the semi-inundated area

Researches should be implemented to take advantages ofthe semi-flood area for production and in accordance with the submerged state. However, it will not reduce the design volume and water quality of a reservoir as well as not increase the volume of erosion soil above the permission level.

Semi-flooded area can be used for some purposes in the dry season, however, land use shall not reduce effective capacity, pollute reservoir water or erode soil on the slope.

7.2.2. Technical Regulation Article 7.2.2 describes the rule before start of impoundment stipulatedin Article 8.1.5 of QCVN 04 - 05 : 2012/BNNPTNT:

8.1.5Works must be done before the accumulation of a reservoir

8.1.5.1 Determine the submerged area of a reservoir, including permanent and semi inundated areas which can be exploited.

The Dam Owner shall conduct site survey and decide submerged area of a reservoir corresponding to the normal high water level and freeboard.

8.1.5.2 Slash and clean up forest and reservoir foundation, absolute excavation of mineral resources or protection of useful mineral mines (if existed), conservation of agriculture land at the highest level (if possible) as well as protection or replacement of cultural works and valuable historical and cultural monuments in the in-undated area of a reservoir foundation.

The Dam Owner shall clear trees, excavate or preserve mineral resources, conserve agricultural lands, and protect cultural heritage in the estimated reservoir area.

8.1.5.3 Having solutions to protect aquatic product resources, gene and other biological resources.

The Dam Owner shall take proper measures to protect aquatic life following the process shown in Guideline for Technical Regulation Article 7.1.5.

8.1.5.4. Creation of appropriate conditions to meet requirement of navigation (if existed).

The Dam Owner shall take proper measures to ensure navigation following the process shown in the Guideline for Technical Regulation Article 7.1.5.

8.1.5.5 Prepare solutions in dealing with peat blocks and other physical blocks being floated when a reservoir is stored.

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