**IRRIGATION TECHNICS

Irrigation:-The science of artificial application of water to the land,in accordance with the 'Crop requirements' throughout the 'Crop period' for full-fledged nourisement of the crop is defined as a irrigation.


NECESSITY OF IRRIGATION IN INDIA:-

India is a tropical country with a vast diversity of climate,topography and vegetation.Rainfall in india,varies considerably in its place of occuaranc,as well as in its amount.Crops cannot,therefor,be,raised successfully,over the entire load,without providing artificial irrigation on fields.
More than seventy percent of our population directly depends on agricultur.Out of a total geographical area about 328 million hectares,about 184 million hectares is the cultivable area.

ADVANTAGES OF IRRIGATION:-

Irrigation project is designed,keeping in view of its economics benefits........likely to be occured or likely to be incurred.there is a big investment on the project and the future recuring changes for maintenence and operation.The project estimate is generally sanctioned when the benefit gives at least about 8% interest on the capital outlay.
The importance and advantages of irrigation during the times of acute food shortages and growing population of our country......
some of the advantages of irrigation......

(I)Increase in foode production.........(Irrigation helps in increasing crop yeilds,And hence,to attain self-sufficiency in food).
(II)Optimum quantity..............(Yeild will be smaller for any quantity lesser  than or in excess of this optimum quantity).
(III)Elemination of mixed cropping ...............(in the areas where irrigation is not assured,generally mixed cropping is adopted)....By mixed cropping,showing together of two or more crops in the same field.....If the weather condition are not favourable to one of the crops,they may be better suitable for the other,and thus the farmer may get at least some yeild.
(IV)General properity........Revenue returns with well developed irrigation helps in prosperity of the entire nation and community.
(V)Domestic water supply......helps in augmenting the water supply in near by villages and towns,where the sources of water are not available....its also helps in providing drinking water for animales,and water for swimming bathing etc.
(VI)Facilities of communication........(Irrigation channels are generally provided with embankments and inspection roads......these inspection paths provide goodroadways)
(VII)Inland nevigation ..........Larger irrigation canels can be used and developed for nevigation purposes
(VIII)Generation of hydro-electric power.........Cheaper power generation can be obtained from water development projects,primarily designed for irrigation alone........for example Ganga and sarda canels,constructed for irrigation,are new generating hydro-electric power as a side product up to about 80,000 kilo watts.

geometric design of highway video

                                                                                   GEOMETRIC DESIGN OF HIGHWAY VIDEO

levelling graph.....profile levelling

                                                                       /LEVELLING/
*Profile levelling with cross section:-

*RL=Reduced level
*M.S.L
*Bench mark=B.M............(Arbitary Benchmark)
                                              (Permanent Benchmark)
                                              (Temporary Benchmark)

APPROXIMATE ESTIMATE

                                                        : APPROXIMATE ESTIMATE:
=>Approximate estimate also no noch priliminary or rough estimate prepared to find out to estimate in a slost time and thus the responsible .........

*TYPES OF APPROXIMATE ESTIMATE:-
(i)Plinth area mathod
(ii)Cubic rate method
(iii)Approximaten quantities fifth bill method.
(iv)service unit method 
(v)Bay method 
(vi)cost compaire method 
(vii)Cost from material and sand laboan
*DIFFERENT TYPE OF ESTIMATE:-
(i)Approximate estimate
(ii)Quantity estimate or Quantity survey 
(iii)Revised estimate...
(iv)Supplymentary estimate'''
(v)Revised and supplymentary estimate due to reduction in cost..
(vi)A complete estimate...
(vii)Annual maintenance or repair estimate (AM or AR Estimate)
*ROI=Returred on investment
*BOI=Built operate transfer
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water cement ratio and compressive strength

                 -/ WATER CEMENT RATIO AND COMPRESSIVE STRENGTH/-

=>A cement of average composition requires about 25 percent of water by mass for chemical reaction.In addition,an amount of water is needed to fill the gel pores.The total amount of of water thus needed for chemical reaction and to fill the gel pores is about 42 percent.The general belief that a water-cement ratio of less than 0.40 or so should not be used in concretes------because for the process of hydration,the gel pores should be saturated---is not valid.This is because,even in the presence of excess water,the complete hydration of cement never takes place due to the decreasing porosity of the hydration products.As a matter of fact,a water ----cement ratio of less than 0.4 is quite common in high-strength structural concretes.
In concrete,as explained earlier,the hardened cement paste is a porous ensemble.Also,the concentration of the solid products of hydration in the total space or volume available(the original water and hydrate cement)is an index of porosity.Like any other porous solid,the compressive strength of cement paste(or concrete) is related to the parameter gel-space ratio or hydrate-space ratio.The water-cement ratio which governs the compressive strength ,is really an expression of the concentration of hydration products in the total volume at a particular age for the resultant degree of hydration.

ASTM CLASSIFICATION

types of foundation/-shallow foundation

                                              //  TYPES OF FOUNDATION//
**/Foundation may be broadly classified under two heads :-

(a)Shallow foundation               (b)Deep foundations

=>According to Terzaghi,a foundation is shallow if its depth is equal to or less than its width.In case of deep foundations,the depth is equal to or greater than its width.

(A) SHALLOW FOUNDATIONS:-
From the point of view of design,shallow foiundations may be of the following types:
1.Spread footings                               2.Combined footings
3.Strap footings                                 4.Mat foundations

Various types of shallow foundations describe below :
Details about the design requirements etc........ are described

1.##Spread footings:-Spread footing are those which spread the super-imposed load of wall or column over a large area.Spread footings support either a column or a wall.Spread footings may be of the following kinds :-

(a)Single footing for a column  or(simple footing)   
(b)Stepped footing for a column
(c)Slopped footing for a column
(d)Wall footing without step
(e)Stepped footing for a wall
(f)Grillage foundations

FIG.2.2  SPREAD FOOTINGS FOR COLUMNS

FIG.2.2/(a)Shows single footing for a column,in which the loaded area (b*b)of the column has been spread to the size B*B through a single spread.The base is generally made of concrete.FIG.2.2/(b) shows the stepped footing for a heavily loadedcolumn,which requires greater spread.the base of column made of concrete.FIG.2.2(c) shows the case in which the concrete base does not have uniform thickness but its made slopped,with greater thickness at its junction with the column and smaller thickness at the ends.......
##/SPREAD FOOTING FOR WALLS:STRIP FOOTING--

          FIG.2.3  SPREAD FOOTING FOR WALLS:STRIP FOOTING
FIG.2.3 (a)Shows the spread footing for a wall,consisting of concrete base without any steps.Usually,masonry walls have stepped footing as shoen in FIG.2.3(b),with a concrete base

##/GRILLAGE FOUNDATION:-

FIG.Steel Grillage Foundations for a steel stanchion carying heavy load.It is special type of isolated footing generally provided for heavily loaded steel stanchion and used in those locations where bearing capacity of soil is poor.The depth of such a foundation is limited to 1 to 1.5m .The load of the stanchion is distributed or spread to a very large area by means of two or more tiers of rolled steel joints,each layer bearing laid at right angles to the layer below it.Both the tier if the joints are thgan embeded in cement concrete to keep the joints in position and to prevent their corrosion.

(2)##COMBINED FOOTINGS:-
A spread footing which supports two or more columns is termed as combined footing.The combined footings may be of the following kinds:-
(A)Rectangular combined footing
(B)Trapezodial combined footing
(C)Combined column wall footings

Combined footings are in variable constructed of reinforced concrete .
The combined footing for columns will be rectangular in shape if they carry equal loads.The design of rigid rectangular combined footing should be done in such a way that centre of gravity of column loads coincide with the centroide of the footing area.If the columns carry unequal loads,the footing is of trapezodial shape.
##COMBINED FOOTINGS FOR COLUMNS AND WALL:-

Sometimes it may be required to provide a combined footing for columns and a wall.Such combined footings are shown in fig....[When the columns carry equal loads ]
and (b)[When the columns carry unequal loads].The design principles of these footings have been discussed later....

3.## STRAP FOOTING:-If the independent footings of two columns are connected by a beam,it is called strap footing.A strap footing may be used where the distance between the columns is so great that a combined trapezodial footings becomes quite narrow,with high bending moments.

FIG.2.7/-shows the strap footing for two columns A and B.Column A is so near to an existing wall that the footing of the wall does not permit the independent footing of column A spread out towards the wall,though it has freedom in other directions.

4.##MAT FOUNDATIONS:-A raft or mat is a combined footing that covers the entier area beneath a structure and supports all the walls and columns.When the allowable soil pressure is low,or the building loads are heavy,the use of spread footing would cover more than one half the area and it may prove more economical to use mat or raft foundation

Rafts may be divided into three types based on their design and construction:-//
(A)Solid slab system                             (B)Beam slab system
(C)Cellular system
All the three types are basically the same,consisting of a large,generally unbroken area of slab covering the whole or the large part of the structures.The thickness of the slab and the size of beams (if any) will be governed by the specing and loading of the column and degree of rigidity required in the raft.