Civil and Mechanical first year syllabus for IOE, T.U. Nepal

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Characteristics strength,Grade of concrete and Nominal mixes

Characteristics strength:It is the minimum strength of concrete for which the designer has reasonable assurance. Mathematically it the compressive strength of material above which 95 percent of the test result of the 15 cm cube (after 28 days) are expected to exceed.
Grade of concrete: it is the number which denotes the characteristics strength expressed in MPa. The number is usually preceded by the letter M which refers to mix.
      Nominal mix is the fixed proportion of cement:sand:coarse aggregate(by mass or by volume).It is the approximation of grade of concrete and their nominal mix.The actual proportion for a grade of concrete can only be known from mix design method.Some grade of concrete and their respective nominal mixes are given below:
M10   -   1:3:6
M15  -    1:2:4
M20  -     1:1.5:3
M25  -     1:1:2

SOME TERMS RELATED TO MINERALS, ROCKS, STONES,CONCRETE

Cleavage: tendency of a mineral to split along a certain plane parallel to crystal face.

Hardness: it is the resistance offered to abrasion by a mineral. It is expressed in Moh’s scale. To know the hardness of the mineral, it is stretched with a series of substance of known hardness which is given below:

Talc-1   

Gypsum-2

Calcite-3

Fluorite-4

Apatite-5

Orthoclase-6

Quartz-7

Topaz-8

Sapphire,corundum-9

Diamond-10

Toughness: it measures the impact that a mineral can withstand.

Streak:It is defined as the colour of mineral in the powered form.

Lusture: it is the shine on the surface of a mineral and its appearance under reflected light.

Seasoning: it is the process of drying quarry sap. Quarry sap is the Freshly quarried stones which contain certain amount of moisture.

Dressing: it is the process of giving definite and regular shape with smooth faces to stone.

Weathering: It is the effect of atmospheric conditions on the stones, rocks. The atmospheric conditions refers to wind, rain, temperature, moisture content etc.

Texture:the feel, appearance, or consistency of a surface or a substance is called texture. It may be smooth, rough, slimy, fuzzy, honeycomb etc.

Fatigue:weakness in metal or concrete caused by repeated variation of load.

Creep:it is the permanent deformation under the influence of long term mechanical load. it can occur due to exposure with long term high stress, the stress may be below the yield strength of material.

Honeycomb: it represents the rough pitted surface resulting from incomplete filling of concrete against formwork or it represents voids in concrete resulting from incomplete filling of voids among the particles of coarse aggregate. it is caused due to the use of stiff concrete or due to insufficient vibration.

Angularity Number Test of Aggregate

It is a non- destructive quality test for aggregate. It is the test about the shape of the aggregate. It gives the qualitative representation of the shape of the aggregate. It is measured in terms of percentage of voids in excess of voids in perfectly rounded aggregate(33%). The more angular the aggregate is, the more is the Angularity number.The normal aggregate suitable for making concrete have angularity number lying between 0 and 10. The rounded aggregate has Angularity Number zero.
When rounded aggregate is filled in a vessel, it leaves about 33% void in it. If a well compacted Aggregate in the same vessel of rounded aggregate leaves 43% voids then its Angularity Number is 10. This test is not applied for the aggregates which gets crushed during compaction of this test.

Apparatus required:

• Metal cylinder of 3 litre capacity.
• Metal scoop
• Tamping rod.  

Procedure: 

• The test sample of the aggregate is sieved and specified size ranges such as 16-20 mm, are used for the test.
• The sample is then filled in the metal cylinder in three layers. Each layer is tamped 100 times with tamping rod before the next layer is put.
• The weight of the aggregate filled in the cylinder is determined. And then after emptying it, it is filled with water and weight of the water is also determined.

Then use the following formula to find the Angularity number:
Angularity Number= 67 - W*100/w*G
W=Aggregate weight filled in the cylinder.
w=Weight of the water filled in the cylinder.
G= Sp. gr. of aggregate.




 Fig. Metal scoop.

Balancing Canal depth

Balancing Canal depth:

Balancing canal depth comes when the canal is in partially embankment and partially in cutting.It is the depth of the canal(H) which gives equal amount of filling(i.e earth required for formation of Banks) and cutting(i.e earth from digging). For a given cross-section of a canal, it has only one balancing depth. For this depth the canal sectional will be economical.
B= Bed width.

b1,b2= width of embankment of left and right side respectively.

d= excavation depth.

h= embankment height.
H=height of embankment from the bed of the canal.

    X- sectional area in cutting =Bd+sd²

     ^{X- sectional area in embankment =} (b1+b2)h+2s1 h²

^{For balancing depth,}

^{Area in cutting= Area in embankment.}

^or,  Bd+sd^{2  =} (b1+b2)h+2s1 h²

or, Bd+sd^2=(b1+b2)(H-d)+2s1(H-d)^2.

From this equation 'd' can be calculated.

Appropriateness and sustainability of Micro- irrigation system in the hills of Nepal.

Micro-irrigations(i.e.Sprinkler and Drip) are the alternative method specially in the hilly areas. Sprinkler and Drip are appropriate and sustainable in the hills of Nepal due to the following reasons:

• Micro- irrigation system requires relatively high pressure which can be easily provided through gravity in the hills.
• It needs clean sediment free water, to avoid clogging of its component, which can be obtained from springs.
• The hill slopes are steep and can be eroded with other method of water application such as: canal irrigation.
• Micro irrigation systems require relatively less amount of water and in the hills, at the higher altitude water shortage may occur but by pumping of water from rivers this irrigation system can be enhanced for better crop yield. This means it suitable even in the area of water shortage.
• Crops in the hills can be sown in rows having appropriate lateral spacing(rows spacing) and spacing between them itself and they can be irrigated by Sprinkler and Drip with less amount of water for better yield. 
• Light soils in the hills are poorly suited to growing rice hence trying to provide irrigation system for growing rice may be proved uneconomic. Hence promoting for growing vegetables or other high value crops can be done with micro- irrigation system.
• Portable micro-irrigation systems are preferable to the farmers in the hills of Nepal because they live in uphills which is several hours walking distance away from the cultivated land. So portable irrigation system is appropriate and sustainable as it can be taken to the any desired place by the farmers.

Delta of a crop and Duty of water and their relation

Delta:

Some quantity of water is required for any crop to come to its maturity. The total quantity of water required for any crop during its base period(B) for its full fledged nourishment when expressed in depth of water(i.e. in 'cm' or in 'inches') is called its Delta. The total quantity of water(i.e. volume of water) is divided by the total irrigated area to obtain Delta of crop of the irrigated area.

     We have talked about base period(B), it is the time period between the first watering of the crop during its sowing to last watering before its harvesting. It is generally expressed in 'days'. 

   The another related term is Crop period. For practical purpose Base period and Crop period are taken as same but they have a little difference. Crop period is the time period between sowing of a crop to its harvesting. In this manner, Crop period is slightly greater than the Base period. 

Duty:

 Duty of a water simply expresses the number of hectare of land that can be irrigated for the full growth of the given crop by supplying 1 cumec water continuously during the entire base period of that crop. It is generally represented by 'D'. Its unit is hectare/cumec. For example, if water flowing at the rate of 1 cumec, runs continuously for B days of the crop matures 100 hectares then Duty of that crop is 100 hectare/cumec to the base of B days.

  Duty varies from point to point. It increases as one moves to downstream from the head of main canal to the head of branches. It is due to the transmission losses in the channels.

Relation between Delta and Duty:

Let a crop of Base period B for which 1 cumec water is supplied continuously for its full growth.

Then the total volume of water supplied during B days for that Crop = (1*B*24*60*60) cubic meter.

By the definition of duty, it is clear that it matures D hectares of land.

Then the total depth of water supplied during base period B = (1*B*24*60*60)/(D*10000)

                                                                                           =8.64B/D meters

We know total depth of water supplied during base period of a crop is Delta.

Then, Delta= 8.64B/D meters.

Crop water requirement, Operational water requirement and Irrigation water requirement.

 Crop water requirement is the water used by the crop for its survival. Plants use water for photosynthesis by which it produces carbohydrates which serves as food for the plants. Water is transfered into the leaves through roots of the plants, after utilization of some amount of water for photosynthesis the rest of the water comes at the surface of the leaves and finally it gets vaporized into the atmosphere which is known as transpiration. While transpiration occurs at the same time Evaporation from the surrounding surfaces such as: open water surfaces, bare soil or vegetative cover occurs. These two contributes for the crop water requirement which is generally measured under the name called 'Evapotranspiration' or 'Consumptive use'.

Operational water requirement is the water used for land preparation, percolation losses in flooded paddy fields. For irrigation water requirement, it must be supplied in addition to the crop water requirement.

Field water requirement:  It is the sum of crop water requirement and the Operational water requirement.

Net irrigation water requirement(NIR): It is the amount of water obtained after deducting the Effective rainfall from the Field water requirement. Effective rainfall is the portion of reliable rainfall that contributes to meeting the water requirement of the crop. It is generally taken as the 80% reliable rainfall multiplied by suitable factor.
          P-eff = f* P(80%)
f=0.70 for upland crops
f=0 if p(80%)<5 mm
f = .85 if 5mm < p(80%) < 100mm
f = .70 if p(80%) > 100mm

Gross irrigation water requirement, commonly said as irrigation water requirement, is the amount of water needed at the diversion intake.
 Irrigation system while conveying water losses water in the form of seepage, spillage and evaporation.
From the intake to the field application, water irrigation system has different efficiencies in its different component. It has field applicaton efficiency (E- field), on- farm distribution channel efficiency(E-farm), and the main canal efficiency(E-main).
Gross irrigation water requirement( I-gross)= NIR/ (E-field*E-farm*E-main).