defined civil about hydro power building

8/18/2019 Defined Civil About Hydro Power Building

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DEFINED CIVIL,MECHANICAL

FEED MHPP Mamasa

1 DEFINED CIVIL

1.1 Hydrological data

The hydrological data is the most important data in a hydropower

project and all of the design depends on it. The data sets should have as

many years of registries as possible. The longer the data period, the more

accurate will be the results.

In ideal conditions there are two main data sets that must be

obtained before the design phase of the project:• Daily ows: Used to compute the ow duration curve !D"# from which

the project$s design ow is derived.

• %a&imum ood ows: Used to predict the ma&imum ood ow for a

given return period.

Usually the hydrological data is obtained from a gauging station.

'owever, in mini or micro hydropower projects, as they are located in

remote areas and have small catchment areas watershed#, often no

gauging stations are available. In the absence of hydrological data at the

site, two procedures should be considered:

• (dapting data from the nearest watershed with similar hydrological

characteristics where a gauging station has been established and long

term hydrological data is available. The watershed with the gauging

station considered should have similar average annual temperature

and rainfall, geology, and land cover

• The second procedure is to measure the river ows during various

seasons and speci)cally during low ow seasons. The more the

measurements the more reliable the data will be.

*. Daily !lows

PT.ARYAGUNA INTI RANU *


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To adapt a data set from a selected gauging station to the

watershed of the project the procedure is based on transposition

method that uses the ratio between the areas of the watersheds. Thus,

being

(gs + (rea of the watershed of the selected gauging station

gs + !low measurement of the selected gauging station

(p + (rea of the watershed of the project

p + "alculated ow for the watershed of the project

This method is widely used and can produce results that can be

considered accurate. There are however other methods. !or further

references the boo- %icro 'ydro Design %anual/ from (dam 'arvey

should be consulted. Depending on the aim of the project and site

conditions local measurements should also be carried out. If the aim of the

project is to optimi0e it according to the available ows, then daily ows

are needed in order to get data that will allow to calibrate the ow

duration curve obtained from the transposition method. 'owever, if the

aim of the project is to guarantee a constant supply of energy to a smallcommunity, then the main hydrological input will be the minimum ow

and the project should be designed for that. The local measurements of

minimum ow should be carried out during the low ow season.

There are several methods to measure the ows at a site. !or

further information on this subject the boo- 1%icro 'ydro Design %anual/

from (dam 'arvey should be consulted.

2. %a&imum ood ows

2


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The availability of ma&imum ood ows measurements is lower

than of daily ows and this is often the case in remote areas li-e the

ones where usually mini or micro hydro projects are implemented. To

come up with an estimation of the ma&imum ood ow, the nearest

gauged river data should be used to estimate the ood factor. The ratio

of the ma&imum ood value recorded by least daily ow measured for

various years can be computed and the average of such ratios can be

used as ood factor. !low and ood ow data ma-e a time series which

means they can undergo through a fre3uency analysis. This will allow to

determine the recurrence interval of the hydrologic event of a given

magnitude &. The average interval of time within which the magnitude y

of the event will be e3ualled or e&ceeded once is -nown as return

period, and is designated by T. If a hydrologic event e3ual to or greater

than & occurs once in T years, the probability 4 56 is e3ual to * in T

cases, or

This means that a return period will be the average time interval in

which a given ood ow is e3ual or e&ceeded. !or e&ample, if the ood

ow at a river station, for a *77 years return period, is 277 m8 9s, this

means that on average there will be at that river station a ood with a

ow of 277 m8 9s or more at every *77 years. Thus the concept of return

period can be used as a ris- management procedure. The higher the

return period of the adopted design ood ow, the lower the ris- of a ood

with a higher ow than the design one, and hence the lower the ris- of

damaging the hydraulic structures at the inta-e area. In order to compute

the ows for a given or several return periods statistical methods have to

be applied to the ow data series so that the fre3uency analysis can be

computed. The most common methods are the following statistical

distributions:

• ormal

• ;umbel

• 4earson III

•


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=ach distribution will produce di>erent results so the designer will

have to ma-e a decision on which design ood ow to use based on all the

computed ows he gets. !or further reference on this subject please chec-

the boo- 1'andboo- of (pplied 'ydrology/ from ?an Te "how. Typically the

return period to adopt for the design of a hydropower scheme will depend

on the ris- of human and material losses in its surroundings if the design

ood ow is e&ceeded. (s micro hydro schemes are often located in

remote areas, thus the ris- is low, the recommended return period for the

design of ood structures is *77 years. (s these methods are estimations,

during visits to the site the engineers should loo- in the area for mar-s of

former oods and also as- the local residents about former oods. (fter

getting an appro&imate cross section, the corresponding water level

during the ood considered, and the river$s longitudinal slope at this

stretch, the ood ow for that cross section can be computed. The

computed value should then be compared with the estimated values. It

has to be noted that given that oods with higher return periods are not

fre3uent it will be di@cult to )nd mar-s of those oods, thus the identi)ed

ood levels will li-ely correspond to ood ows with return periods of

about * to A years. This should be ta-en into account when comparing

these in situ estimation values with the ood ow values obtained from

the statistical methods. If there are any hydrological studies for other

projects in the area they should also be used. (s stated earlier, the more

hydrological data that can be gathered and used, the more accurate will

be the results.

1.2 Topographic survey

B


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Topography of the project area should be obtained. It should include

the areas predicted for the following structures: weir and inta-e, canal,

forebay, penstoc- and powerhouse. (reas around this structures should

also be included so that during the development of the project the

designer can also have available information when designing for e&ample

the ushing channel for the gravel trap or settling basin. It has to be noted

that the area around the inta-e and weir should be detailed so that there

is enough information for computing ood levels upstream and

downstream of the weir section.

1.3 Design Procedure

The design template spreadsheet %'44 %amasa contains the

following sheets:

• Ceir stilling basin

• Cater levels U9E D9E

• Inta-e

• Inta-e "anal

• ;ravel trap

• Eide Epillway

• (pproach canal

• Eettling Fasin

• Eettling Fasin + !lushing pipe

• 'eadrace "anal

• !orebay

• !orebay + !lushing pipe

• 4enstoc- design

• 'ead losses calculation

• 4ower calculations

A


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• (nchor bloc-s

• Ceir Etability

1.4 Execution of the design process

1.4.1Hydro desi !

The design process should be carried out accordingly to the

following instructions:

* Inta-e:

• Eet the design discharge d#.The inta-e design discharge din#

will then be *.2 d. This is for safety and to account for the seepage

losses on the canal, from the inta-e to the forebay. The din will be

the ow value used for the design of the upstream structures li-e

the canals.

• "hoose the position of the inta-e and set the river bed level F


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• !rom the governing e3uation of ow through submerged inta-es,

the di>erence between the water levels upstream and downstream

the inta-e, h# re3uired to allow the design flow to pass through

the inta-e ori)ce is computed. ote that the downstream water

level will be based on the inta-e canal geometry or other structures

such as gravel trap#. Thus, the design and calculation process will be

iterative.

2 Inta-e "anal:

• Eet the %anning coe@cient accordingly to the surface material of

the canal.• Eet slope of the vertical canal walls m# to 0ero. Eet a slope for the

canal. "ompute goal see- by setting dif to 0ero by changing h. If

the water depth in the canal is not at least A cm higher than the

height of the inta-e ori)ce then set a new slope and do goal see-

again. Gepeat the process as many times as necessary until the

water depth in the canal is at least A cm higher than the height of

the inta-e ori)ce. This is to assure the ori)ce is submerged.• "hec- if the ma&imum si0e of particles to be transported in the

canal is higher than the minimum si0e of particles to be settled in

the gravel trap. If not increase the slope and chec- if the

submergence condition of the ori)ce is still veri)ed.

8 Inta-e:

• The water level downstream of the inta-e, hD9E, ori)ce is now the

level set previously in the inta-e canal. !rom this level it is

calculated the water level upstream the inta-e, hU9E. which will set

the normal water level, Cerent canal widths.

B Ceir Etilling basin:

• Eet the ma&imum ood discharge ma& ood# and the normal ood

discharge norm ood# accordingly to the values obtained from ahydrological study.

J


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• Eet the length of the weir crest,


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• ;o to the line 1Giver regime downstream/. If the critical depth is

greater than the uniform depth hcLhu# then the river regime is

supercritical and no hydraulic jump will occur. In this case go to step

55. If hcM Mhu# then the regime in the river for ood conditions is

subcritical hence there will be a hydraulic jump downstream the

weir and a stilling basin must be provided.

• Eet the depth of stilling basin bed level from downstream bed level,

, to 0ero. This means that for the calculations of the hydraulic jump

it is considered that the bed level of the stilling basin is the same as

that of the river in the section immediately downstream.• !or the calculation of the hydraulic jump, the )rst step is to consider

that between the weir crest and the bottom of the weir the total

energy of the ow will remain constant because rapidly varied ow

will occur. The water depth at the end of the weir is computed in

accordance to this principle. !or this in the table named 1=nergy

conservation at weir/ the cell dif =, using goal see-, must be set to

0ero by changing D* which is the water depth at the end of the weir.• (fter the calculation of D* all of the calculations of the hydraulic

jump are automatic and the designer can go directly to chec- if the

water level at the river, TC


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• Gepeat the iterative process at the table 1=nergy conservation at

weir/ and chec- again the condition TC< TC


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• Eet the safety factor, E!. This is an oversi0ing factor for the design of

the gravel trap and its main purpose is to account for the turbulence

in the ow which will decrease the e@ciency of the settling process.

In comparison to a settling basin a gravel trap is usually a smaller

structure in length because the settling velocity of particles is

higher, thus they need a shorter distance from the beginning of

structure to settle. (s a result of this, for the same volume of

particles to store between ushing, a gravel trap will need a bigger

collection depth. 'owever this value should be -ept in a reasonable

range to prevent an e&cess of e&cavation. Increasing the safety

factor is a way to solve this problem because as the si0e of the

gravel trap increases the collection depth decreases.

• "hec- if the ratio


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• Eet the river carrying load of gravel. This -ind of data is very rare, so

usually depending on the characteristics of the river the designer

can assume a value between 7.A and 2.7 -g9m8 . & Eet the ushing

time. In ideal conditions this time should be e3ual to the ushing

fre3uency of the settling basin in order to ma-e easier and simpler

the operation of the scheme. 'owever this is not always possible

because it would lead to a high collection depth. It has also to be

noted that the design ushing fre3uency is for ood season which

means that during the remaining year when the river carrying load

is much lower the ushing fre3uency will decrease.

• Eet the density of gravel. Usually the value of 2H77 -g9m8 is

considered.

• !rom the previous inputs the dimensions and depths of the gravel

trap are de)ned. The settling depth is considered e3ual to the depth

of the ow in the inta-e canal. The freeboard is considered to be the

same used in the inta-e canal 7.87 m#.

K Eide spillway

• The design discharge, d, is lin-ed to the spreadsheet of the inta-e

• The minor ood discharge, minor ood, is computed considering

that it is e3ual to *.*A d. This will be the ow used to design the

spillway as it is considered to be an unfavorable situation for the

design of the inta-e. This happens because a small e&cess to the

design ow will produce a low head of water over the spillway crest

leading to a higher length of the crest than in a major e&cess over

the design ow where the head over the crest will be higher and

re3uire a shorter crest length re3uired.

• The height of the spillway crest is considered to be e3ual to the

normal water depth in the canal, which mean that any e&cess of

ow will be spilled.

*2


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• Eet the discharging coe@cient, ", accordingly to the pro)le of the

weir crest to be used.

•

Eet the safety factor, E!. This is to account for the appro&imationsconsidered in the design of the spillway. Usually it is used *.A but

this value can go up to 2. The designer must have in mind that the

higher the safety factor the higher the length of the crest.

N (pproach canal

• The %anning coe@cient is lin-ed to the to the inta-e canal sheet

because it is assumed that all of the canals are built with the same

material.

• The ow is the design ow and is lin-ed to the inta-e sheet

• Eet the slope of the canal. If possible ma-e it e3ual to the one of the

inta-e canal this is for easy of construction#.

• Eet the width of the canal. The approach canal will not have to

convey ood ow since ood ows are spilled from the side spillway

upstream#, but only the design ows and thus the canal can benarrowed. "hoose a width, b, which ma-es the height of the canal

walls including the freeboard#, hwalls, about double its si0e.

• Use goal see- to set the cell dif to 0ero by changing h. If the

height of the canal walls including the freeboard#, hwalls, is not

about two times the si0e of the width of the canal, b, change the

width of the canal and repeat the goal see-.

• "hec- if the ma&imum si0e of particles to be transported in thecanal is greater than the minimum si0e of particles that were settled

in the gravel trap. This is to assure that there will not be settling of

sediments before the settling basin. If this is not veri)ed increase

the slope of the canal and repeat the previous steps.

*7 Eettling Fasin

• The settling basin is designed for the inta-e design discharge and

this value is lin-ed to the inta-e sheet.

*8


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• Eet the minimum si0e of particles to be settled in the settling basin

usually it is considered this si0e to be 7.2 mm#

•

(ccording to the Gouse graph which is in the spreadsheet# set thefall velocity of the particles for the selected si0e.

• Eet the width of the settling basin. This value should be 2 to A times

the width of the approach canal.

• Eet the safety factor, E!. This is an oversi0ing factor for the design of

the settling basin and its main purpose is to account for the

turbulence in the ow which will decrease the e@ciency of the

settling process. Usually the safety factor, E!, ranges between * and

2. & "hec- if the ratio


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• Eet the ushing time. In ideal conditions this time should be e3ual to

the ushing fre3uency of the gravel trap in order to ma-e easier and

simpler the operation of the scheme. 'owever this is not always

possible because the smaller dimensions of the gravel trap reduce

its storage capacity, thus leading to higher ushing fre3uencies. It

has also to be noted that the design ushing fre3uency is for ood

season, when the river carries a high sediment load, which means

that during the remaining year when the sediment load is much

lower, the emptying fre3uency will decrease.

•

Eet the density of sand. Usually the value of 2H77 -g9m8 isconsidered.

• !rom the previous inputs the dimensions and depths of the settling

basin are de)ned. The settling depth is considered e3ual to the

depth of the ow in the approach canal. The freeboard is considered

to be the same used in the approach canal 7.87 m#.

• ote that if the collection tan- has sloped side walls the computed

Dcollection is not the real depth to be used. In this case the designer

should decide on the longitudinal slope of the settling basin bottom

and then set the collection depths at the beginning and end of the

settling9collection area in a way that the volume for sediment

storage is at least e3ual to ?olsand.

** Eettling basin + !lushing pipe

• Eet the depth of ushing vertical distance between the bottom of

the gravel trap and the end of the ushing pipe#. If there is no

ushing pipe and the ushing system is a gate and downstream a

ushing canal, then set this value to 0ero. & Eet the ori)ce

coe@cient usually *.N#.

• =3uation * accounts for the situation when the basin is full and its

volume and the incoming ow will be totally ushed. =3uation 2

accounts for the situation when the basin is already empty and only

the incoming ow will be ushed.

*A


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• The diameter of the pipe is automatically computed. If h ush was

set to 0ero then only e3uation * will have a result.

•

If the ushing system to adopt has a pipe then its diameter will bed ushing. If the system is a gate and a downstream ushing canal

then the gate will be si0ed based on the area of the ori)ce. !or this,

set the width and the height will be automatically calculated.

*2 'eadrace canal



material.

• The ow is the design discharge and is lin-ed to the inta-e sheet

• Eet the slope of the canal. If possible ma-e it e3ual to the one of the

inta-e canal this is for easy of construction#.

• Eet the width of the canal. "hoose a width, b, which ma-e the height

of the canal walls including the freeboard#, hwalls, about double its

si0e.• Use goal see- to set the cell dif to 0ero by changing h. If the

height of the canal walls including the freeboard#, hwalls, is not

about two times the si0e of the width of the canal, b, change the

width of the canal and repeat the goal see-.

• "hec- if the ma&imum si0e of particles to be transported in the

canal is greater than the minimum si0e of particles that were settled

in the settling. This is to assure that the particles that failed to settlein the settling basin will not settle in the bed of the canal. If this is

not veri)ed increase the slope of the canal and repeat the previous

steps. ote that sometimes this will not be possible because of

topography or location of forebay and in such cases the particles

deposited along the headrace canal will have to be manually

cleaned after the ood seasons.

*8 4enstoc- design

*H


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• The design discharge of the penstoc- is the design discharge of the

hydropower scheme. This cell is lin-ed to the inta-e sheet.

•

Eet the length of the penstoc-,


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• Eet the surge head factor. This will depend on the selected turbine.

!or 4elton and "ross !low *7 27P, and for !rancis turbines 87 B7P.

& "hec- the safety factor, E!. If the value is less than 8.A then

increase the e>ective thic-ness, te>, until it the E! is at least 8.A.

*B !orebay

• The design discharge for power generation is lin-ed to the inta-e

sheet and the diameter of the pipe and the velocity of the ow in

the penstoc- lin-ed to the penstoc- design sheet.

• Eet the width of the forebay. (s a thumb rule, to start the design, it

can be assumed that the length of the forebay will be 2 to 2.A timesthis si0e. 'owever according to the re3uired volume of water above

the penstoc- and to meet the site conditions the designer may have

to change this ratio.

• Eet the clearance of the penstoc- from the bottom of the forebay.

This is to avoid that particles and sediments settled in the forebay

get in the penstoc-. The minimum clearance is 7.87 m. 7.A7 m is a

common and reasonable value to use.

• The minimum submergence of the penstoc- is automatically

calculated because it depends only on the diameter of the pipe and

ow velocity.

• !or the design of the forebay it is considered that it should be

available to cope with the ow variations in the turbine during

normal operation conditions# a bu>er volume e3uivalent to *A

seconds of supply at the design ow. This is also automatically

calculated as well as its corresponding depth of water.

• Eet the discharger coe@cient of the spillway. This depends on the

shape of the crest and spillway.

*K


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• Eet the depth of water over the crest of the spillway. 'ave in mind

that the higher the water depth the smaller will be the crest length

of the spillway. The spillway is designed to spill all the design ow in

case the powerhouse is shut down and no ow is going through the

penstoc-.

• Eet the freeboard for the spillway. This is a safety margin in case

higher ows than the design ow arrive to the forebay. "onsider a

value that is half the water depth over the weir crest. This will

increase, if necessary, in A7P of the discharge capacity of the

spillway.• The length of the spillway is automatically calculated using the

previous input data and the weir e3uation. It has to be noted that

this value must be smaller than the length of the forebay.

• Eet the angle of the transition walls at the entrance of the penstoc-.

This transition must be smooth so mild angles are recommended

around 27P#. 'owever to )t site conditions the values can be

adjusted.

• !or the )nal placing of the forebay the designer has to set the

normal water level C


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• The input data for penstoc- and ow characteristics is lin-ed to

other sheets.

•

(ccording to the material of the penstoc- set the roughness, -. forsteel - *.A&*7 B m#. & Use goal see- to set the cell "olebroo-

Chite, " C, to 0ero by changing the cell f. Cith this the continuous

head loss is automatically calculated.

• Eet the thic-ness of the trash rac- bars, t typically * to 2 cm#.

• Eet the distance between bars, s this value will depend on the

selected turbine and the speci)cations of the manufacturer. In a

preliminary design consider this value around 2 or 8 cm. ote that

the smaller the spacing between bars the more protected the

turbine will be, but the head loss will increase as well as the

clogging and the conse3uently the cleaning fre3uency#.

• Eet the angle of the trash rac- with the hori0ontal, , typically it is

used J2 degrees which is e3uivalent to a slope of *:8 ':?#.

• Eet the cross section shape factor, V, accordingly to the shape of the

bar cross section. & (fter all the mentioned inputs the head loss in

the trash rac- is calculated

• Eet the entrance factor, -e, factor accordingly to the shape of the

transition between the forebay and the penstoc-. The head loss is

calculated after this values is set.

• !or the head loss in a bend, set the angle of the bend, W, and the

bend factor, X use the table for bends on the right as reference#,the head loss is then computed. (dd as many bends as necessary. If

the bend has two components hori0ontal and vertical# then

calculate them separately accordingly to the bending angles.

• !or the head loss due to contraction reduction of the pipe si0e at

the joint between the penstoc- and the turbine# set the diameter of

the smaller pipe, D2 usually this value depends on the dimensions

of the turbine, but in a preliminary phase can be considered 7.B mfor low power !rancis turbines.

27


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• Eet the loss factor, -e. !or this type of transition -e 7.7A. The head

loss is then calculated.

•

(ll of the losses are resumed in point 8 and the total head loss iscalculated.

• The net head, 'net is then calculated:'net 'gross htot.

• (s stated earlier, if the head loss is too high repeat the calculations

assuming a larger pipe diameter.

*H Tailrace canal



material.

• The ow is the design discharge and is lin-ed to the 4enstoc- Design

sheet.

• Eet the slope of the canal. If the tailrace canal is stepped then set

the slope to 0ero.

• If the canal is made of steps then it is assumed that the ow will be

critical, hence the water depth will be e3ual to the critical depth.

• Eet the width of the canal. "hoose a width, b, which ma-e the height

of the canal walls including the freeboard#, hwalls, about double its

si0e.

• If the canal has a slope then use goal see- to set the cell dif to

0ero by changing h. If the height of the canal walls including the

freeboard#, hwalls, is not about two times the si0e of the width of

the canal, b, change the width of the canal and repeat the goal

see-.

• ote that for safety if the ow regime in the tailrace canal is

supercritical the )rst A7 meters of the tailrace canal should always

have the height of the vertical walls determined by the critical

depth.*J Giver water level at tailrace

2*


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• De)ne a cross section on the river at the end of the tailrace.

• Eet the %anning coe@cient accordingly to the river bed

characteristics• 4ic- a point some meters upstream the selected cross section and

other a few meter downstream and compute the longitudinal slope

of the river. Input the value in cell Elope.

• !rom the cross section pro)le get the slope from the river ban-s m

left ban- and m right ban-#

• Eet the width of the river canal on that cross section, b.

• Gun goal see- by setting cell dif to 0ero by changing h. This will

compute the uniform water depth for the appro&imate cross section

of the river.

• The computed river water level will be used to decide the location of

the end of the tailrace canal.

*K 4ower calculations

• Eet the basic data inputs: density of water and gravity acceleration.

• The design discharge and net head are lin-ed to respectively the

penstoc- design and head loss calculations sheets.

• Eet the e@ciency of the turbine. !or a preliminary phase of the

study before the turbine manufacturer is selected and the

characteristics of the turbine de)ned# use 7.KA for !rancis 7.JA for

4elton turbines and 7.HA for "ross ow.

1.4." #im$%i&ed s'r()'(ra% desi !

The simpli)ed structural design includes two procedures: verifying

the stability of the weir and of the anchor bloc-s.

It has to be noted that anchor bloc-s should be placed at:

• "onnections of the penstoc- to other structures !orebay#

• =&pansion joints

• Fends vertical in plan and9or pro)le#

22


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• "hanges in the diameter of the penstoc-

* (nchor bloc-s

• Input the basic data: density of water, speci)c weight of water,speci)c weight of concrete, speci)c weight of soil and soil friction

angle. The soil friction angle, Y, should be obtained from samples at

the site, however when this data is not available a value between 2A

and 87 degrees can be assumed. The friction angle between soil and

concrete is considered to be 298 of the soil friction angle.

• Eet the dimensions of each of the anchor bloc-s. (dd as many

columns corresponding to anchor bloc-s as necessary. The volume

and weight of the anchor bloc-s are automatically computed.

• Input the hydraulic data: set the water head in the penstoc- for

each of the anchor bloc-s the surge head will be automatically

computed accordingly to the type of turbine that was set in the

sheet 14enstoc- Design/R set the upstream diameter of the

penstoc-, D*, this can be understood as the diameter of the

penstoc- that goes in the anchor bloc-#R set the plan and pro)le

angles of the upstream penstoc- *h and *v#, set the downstream

diameter of the penstoc-, D2, this can be understood as the

diameter of the penstoc- that goes out of the anchor bloc-#R set the

plan and profile angles of the downstream penstoc- 2h and 2v#.

• (fter inputting the previous data all of the hydraulic forces are

automatically computed using the =uler Theorem.

• "hec- the safety factors for sliding and overturning. These factors

must be at least e3ual to 8. ote also that the resultant force should

be in the middle third of the base for stability against overturning. If

these conditions are not veri)ed then go bac- to the dimensions of

the anchor bloc-s and change them. Usually the solution will be to

increase the anchor bloc- dimensions, and if this does not wor- or

the )nal dimensions of the anchor bloc- are too big, then consider

changing the alignment of the penstoc- in plan and9or pro)le#

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• !or the bearing capacity: set the depth of the base of the foundation

this depth is measured in relation to the )nal ground level above

the anchor bloc- foundation#. In accordance to the friction angle of

the soil, Y, input the bearing capacity factors 3 and Z obtain

these values from the table that is in the spreadsheet template on

the right of the calculation for bearing capacity#.

• "hec- the safety factor for the bearing capacity. This value must be

e3ual or greater than 8. If not then change de dimensions of the

anchor bloc- in a way that the ma&imum bearing load is reduced

increase the length and width, and decrease the height#.2 Ceir

• Eet the speci)c weights of water, soil, saturated soil, and weir. Eet

also the friction angle of the soil,Y. The soil characteristics should be

obtained from samples collected at the site, however if this data is

not available values of *J - 9m8 for the speci)c weight of the soil,

*N - 9m8 for the saturated speci)c weight of the soil, and between

2A and 87 degrees for the friction angle should be considered.• (ccording to the shape of the weir divide its cross section in simple

geometric )gures and input the areas of each one of them as well as

the length of their base.

• Eet the factor for calculating the hori0ontal coordinate of the center

of gravity, ";factor, for each of the internal shapes of the weir.

• Eet the depth for the high ood level hf#. This depth is measured

from the point where the upstream weir apron intersects the ground

level.

• Eet the height between the turning point the point in the

downstream e&tremity of the weir body that is in contact with the

foundation# and the upstream river bed level.

• (fter the previous input data all of the loads are automatically

calculated.

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• "hec- the safety factors for sliding and overturning. These factors

must be at least e3ual to 8. ote also that the resultant force should

be in the middle third of the base for stability against overturning. If

these conditions are not veri)ed then go bac- to the dimensions of

the weir and change them. If the problem is safety against sliding

then increase the weight of the weir and increase the contact

surface between the weir and the foundation soil. If the problem is

in the safety against the overturning then increase the length of the

weir, F, and particularly increase the length and cross section area

of the upstream section of the weir by upstream section of the weir

shall be understood the section of the weir upstream the crest#.

• !or the bearing capacity: set the depth of the base of the foundation

this depth is measured in relation to the )nal river bed level above

the weir foundationR if the river slope is too high and the depth of

the foundation cannot be considered the same upstream and

downstream the use an average value#. In accordance to the friction

angle of the soil, Y, input the bearing capacity factors 3 and Zobtain these values from the table that is in the spreadsheet

template on the right of the calculation for bearing capacity#.

• "hec- the safety factor for the bearing capacity. This value must be

e3ual or greater than 8. If not then change de dimensions of the

weir in a way that the ma&imum bearing load is reduced increase

the length#.

1.4.* G(ide%i!es +or $o er-o(se %ayo('

The design of the powerhouse layout should ta-e into account the

following:

• The powerhouse should be safe from not only annual oods but also

rare ood events. Discussions should be held with the local

community members to ensure that ood waters have not reached

the proposed powerhouse site within at least the past 27 years.

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• if possible the powerhouse should be located on the ground level to

minimi0e e&cavation wor-s.

•

The proposed location should be accessible throughout the year.• The powerhouse should be located close to the community that it

serves, provided that the penstoc- alignment and other parameters

are feasible and economical. This will reduce the transmission line

cost, and if agro processing units are also installed in the

powerhouse, the community will not have to carry their grain for a

long distance.

• !or each turbine a plan area of *7 m & K m is re3uired.

• The clear height of the building should be at least 8 m.

• ( control room is re3uired. It should have an area that is enough to

accommodate the control panels typical dimensions are * m width

by 7.H m depth and re3uiring a minimum bac-space of 7.K m, also

note that for each turbine are re3uired about 8 to B control panels#,

and a des- for the operator as well as a storage area for documentsand operation manuals. The control room should also have a window

that allows the operator a direct view to the machinery.

• ( toilet room is re3uired.

• There should be a clear spacing of at least * m around each item of

e3uipment that has moving parts such as the generator, turbine

and the belt drive#

• (de3uate windows should be provided for lighting and ventilation.

ote that the door and windows need to be located such that they

do not obstruct access to the e3uipment. This re3uires coordinating

the locations of the e3uipment, windows and the door.

defined civil about hydro power building

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