ZONE TECH BMC + Environment + Survey 1 · ZONE TECH BMC + Environment + Survey 4 Q.15 Sol. Laying...

BMC + Environment + Survey 1ZONE TECH

Sol. List- I List-II

(Acceptable limit)

1. BOD of drinking water 0

2. Hardness 200

3. Nitrate 45 PPM

4. TDS 500

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TECH

BMC + Environment + Survey 2ZONE TECHQ.4

Sol. (i) DPD test

• Di-ethyl phy-ene di-omine

• Reagent Pallian DPD developed by british drug house

• Technique Colour matching.

(ii) Chloretex test

• Reagent BDH chloretex

• 50 ML water 45 ML chloretex — colour matched

• Corresponds to 0.2 ppm chlorine form pink colour.

Q.5

Sol. The various tests performed on bricks are as follows:

• Crushing strength • Absorption

• Shape and size • Efflorescence

• Sound test • Hardness test

Original scale 1 cm 15 m

Q.6

Sol. Ca OH 2 CO2 CaCO3 H2O ... (1)

Ca OH 2 Ca HCO3 2 CaCO3 H2O ... (2)

Ca OH 2 Mg HCO3 2 MgCO3 H2O ... (3)

Ca OH 2 MgCO3 CaCO3 Mg OH 2 ... (4)

Ca OH 2 MgSO4 CaSO4 Mg OH 2 ... (5)

Na2CO3 CaSO4 Na2SO4 CaCO3 ... (6)

Q.7

Sol. In plane surveying curvature of earth is not considered where as in geodetic surveying curvature ofa earth is considered plane surveying is suitable for less accurate survey work and small areas whilegeodetic survey is suitable for large area.

Q.8

Sol. These are considered undesirable as they undergo a large change in volume, which produce cracks inconcrete.

Q.9

Sol. Correction in Latitude (CL) and Departure (C

D) of a traverse line is given as

LC D

T T

– L – DL,C D

L D

L / D = Algebric Sum of latitudes/departures of all lines.

LT/D

T= Sum of latitudes/departures of lines without considering the sign.

L/D = Latitude/Departure of the line to be corrected.

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Sol. Shrunk scale S.F. × Original scale (R.F.)

1

1600

15

16×Original scale (R.F.)

Original scale (R.F.) 1

1500

Q.11

Sol. Water demand 50 × 1000 500000 l/day

bleaching powder 2Cl demand x

0.4 0.4

5 kg x

0.4 x 5 × 0.4 2 kg

Cl2 demand chlorination rate × water demand

2 × 106 mg x × 500000

x 62 10

500000

4 ppm. Ans.

Q.12

Sol. MHD 2.7 × 130 × 3500000 × 10–6

1228.5 MLD

Q.13

Sol. equivalents of Ca2+ 260

40 /2130

equivalent of Mg2+ 80

24 /2 6.66

total equivalent 130 + 6.66 136.66

total hardness in terms of CaCo3 136.66 × 50

6833 mg/lit

Q.14

Sol. • Defects due to conversion

• Defects due to fungi

• Defects due to insects

• Defects due to natural forces

• Defects due to seasoning

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Sol. Laying the concrete cover on the side slope and channel bed of canal, is called concrete lining ofcanal.

It improves the flow through the canal and reduces the seepage loss and maintanance cost of thecanal.

Q.16

Sol. Ply means thin layer. The plywoods are boards which are prepared from thin layers of wood orveneers. The three or more veneers in odd numbers are placed one above the other with the directionof grains of successive layers at right angles to each other. They are held in position by application ofsuitable adhesive all over veneers normal to each other because it increase the longitudinal andtransverse strengths of plywood.

Q.17

Sol. • Defective concrete, spalling or loose plaster in ceiling

• Water seepage from external wall, window, roof, or from ceilling.

• Structural cracks in columns & beams.

• Non-structural cracks (usually in plaster or other finishes with cement sand rendering as base)

• Defective external wall finishes/mosaic tiles/ceramic tiles/stone cladding/curtain wall.

Q.18

Sol. C6H

12O

6 + 6O

2 6H

2O

+ 6

CO

2

(BOD)u COD and COD THOD

(BOD)u COD THOD 600 × 1.06 636 mg/C

Q.19

Sol. Permanent Adjustment of surveyor's Compass

Permanent adjestment are those adjustments which are does only when the fundamental relationsbetween the parts are disturbed. The are, therefore, not required to be repeated at every set up ofthe instrument. These consist of:

• Adjustment of level

• Adjustments of sight vanes

• Adjustments of needle

• Adjustments of pivot point.

Q.20

Sol. When the instrument is at A,

Apparent difference in elevation between A and B

2.860 – 1.285 1.575 m (A higher)

When the instrument is at B

Apparent difference in elevation between A and B

2.220 – 0.860 m (A higher)

True difference in elevation 1.575 1.360

2

1.468 m (A higher)

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Q.21

Sol. Total dry sludge content 0.068 × 1000000 6800 kg/day

84% moisture content means 16% dry sludge

16 kg dry sludge produce wet sluge 100 kg

6800 ________________________ 100

680016

42500 kg

42.50 t/day

Volume of wet sludge 42.50

1.02 41.66 m3/day

Capacity of digester Rf. 41.66 100

3.5

1190.28 m3

Provide 30% add. capacity 1.3 × 1190.28 1547.37m3

provie 6 m depth than c/s area 1548

6 258 m2

Dia of tank 2500

/418.12 m Ans.

Q.22

Sol. Gypsum is added to prevent the flash setting of the cement i.e. to delay the hydration or prevent thefast reaction for some time after adding the water to cement. The addition of calculated quantity ofgypsum retards and controls the setting times. This ensures that concrete will not set too quicklybefore it is placed and compacted at required place.

Q.23

Sol. Correction for temperature 20 × 6.2 × 10-6 (80 – 55) 0.0031 m (additive)

Correction for pull 0P – P L

AE

Now, weight of tape A (20 × 100) (7.86 × 10–3) kg 0.8 kg

A 0.8

7.86 20.051 sq. cm.

Hence,

Cp

6

16 – 10 20

0.051 2.109 10 0.00112 (Additive)

Correction for sag

2 2

1 1

2 2

w 20 0.8

24P 24 16

l l 0.00208 m (subtractive)

Total correction + 0.0031 + 0.00112 – 0.00208 +0.00214 m

5 Marks

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Sol. The ability of cement of maintain a constant volume is known as soundness of cement.

Causes of unsoundness of cement: Many a times in cement, certain constituents undergo undesirableexpansion. This volume change owing to expansion of cement constituents leads to disintegrationand cracking. Unsoundness in cement occur due to the presence of magnesia and free lime in cementand thus it hydrates very slowly. After setting of cement, moisture penetrates into the free limeresulting in hydration. The hydrated/ slacked lime being larger in volume, results in expansion ofcement causing thereby cracking and disintegration.

Q.25

Sol. In loose needle method, Magnetic meridian is established at each traverse station, it means at eachstation magnetic bearing is found out with the help of magnetic compass.

In fast needle method bearing of first line is determined with the help of magnetic compass andmagnetic bearing of other lines are find out by magnetic bearing first line and included angles.

Fast needle method is more accurate than loose needle method.

Q.26

Sol. Flase set: For OPC, the initial setting time is 30 min and final setting time 30 min and 600 min (10

hours). Within the first few minutes of mixing the water to cement, abnormal permeature hardeningof cement takes place. This is called as false set. Not much heat is evolved in this and remixing ofcement paste without further addition of water restores the original plasticity and then cement pastesets in a normal way.

Flash set: The compound tricalcium aluminate (C3A) is generally present in cement in a proportion of

about 8 to 12% by mass. C3A reacts very fast with water leading to an immediate hardening of paste

and this is called as flash set. Gypsum is added in cement to prevent such a fast reaction.

Q.27

Sol. When water is added to cement, a chemical reaction starts which is exothermic in nature and producesa signification amount of heat. This is known as hydration and the liberated heat is called the heat ofhydration.

• The temperature at which hydration takes place. Higher the temperature, rapid is the hydration.

• The fineness of cement. Finer the cement, rapid is the hydration.

• The proportion of ingredients of cement.

Q.28

Sol. QD A × V

S

A D

S

Q

V 1.5 24 60 60

80.5

1609.93 m2

Volume of tank QD × t

l 1.5 × 80 × 60 7200 m3

Depth of tank 7200

1609.93 4.47 m

assume L

B3

(B × L) 1609.93

(B × 3B) 1609.93

B 23.16 m

L 3B 3 × 23.16 69.49 80 m safe of .

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Sol. Bulking of sand: The presence of moisture in sand increase the volume of sand. This is due to thefact that moisture creates a thin film of water around the sand particles which results in the increaseof volume of sand. For a moisture content of about 5 to 8 percent, this increase of volume may be asmuch as 20 to 40 percent, depending upon the grading of sand. The finer the material, the more willbe the increase in volume for a given moisture content. This phenomena is known as the bulking ofsand. The graph below shows the variation of percentage increase in volume of sand with moisturecontent.

0

10

20

30

40

5 10 15 20

Per

cen

tag

e in

crea

se i

n v

olu

me

Percentage by Weight of Moisture

Coarse

Medium

Fine

Q.30

Sol. Trapezoidal rule :-

The interval is constant from first offset to 5th offset. There is another interval betweenthe 5th and 7th

offset and a third interval between 7th offset and 10th offset. The total area can, there fore, bedivided into three sections.

1 2 3

where 1 area of first section, 2 area of second section

3 area of third section, d1 interval for first section 15 m

Now 1 7.60 10.68.5 10.7 12.8

2

15 616.3 m2

2 10.6 8.3

9.52

10 189.5 m2

3 8.3 4.4

7.9 6.42

20 413 m2

616.5 + 183.5 + 413 1219 m2 12.19 ares.

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Sol. Nitrogen Content:

The presence of nitrogen in water may be found to occur in one or more of the following forms.

• Presence of nitrogen in water indicates presence of organic matter.

• Presence of free ammonia in water indicates its recent pollution. Free ammonia should not bemore than 0.15 mg/l and it can be measured by simply boiling the water and measuring byboiling a sample of already boiled water plus strong alkaline like KMnO

4 and measuring the

ammonia so liberated.

• The presence of organic ammonia indicates decomposition has just started and limiting value inpotable water is 0.3 mg/l it is measured by boiling a sample of already boiled water plus strongalkaline like KMnO

4 and measuring the ammonia so liberated.

• Among all form of nitrogen, nitrite is highly dangerous, hence its permissible limit is zero and itis measured by colour matching technique. The colour for nitrite is developed by sulphuric acid+ Napthamine.

• Nitrate is not harmful because it is fully oxidised. But too much of nitrate of affects infants. Thereason behind this is it causes blue baby diseases or mathemoglobinemia, Nitrate concentrationshould not be more than 45 mg/l.

• Nitrate concentration is measured by colour matching techinque. Colour is formed by phenol-disulphonic + Potassium hydroxide.

• Free Ammonia + Organic Ammonia = Kjeldahl Ammonia.

Q.32

Sol. Quantity of sewage treated 25000 × 420 10500000 lit.

10500 m3

The BOD content per day 800 × 10.5 8400 kg

assume organic loading in pond as say 75 kg/hec/day

8400

75001.12 × 104 11200 m2

L

B4

L × B 11200

4B2 11200

B 52.90 m

L 211 m

H 4 m

detention time in days 211 52.90 4

10500

4.25 days

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Q.33

Sol. For the effective removal of BOD either trickling filter or oxidation pond may be designed. Thewaster water treatment plant should be without any power supply as given in the problem. Hence,oxidation pond may be designed as given below.

The quantity of water supplied per day 20000 × 150 = 3 × 106 litres

Assuming 80% of the water supplied is converted in sewage

Quantity of sewage produced 0.80 × 3 × 106 = 2.4 × 106 litres

BOD content of waste water 6 –62.4 10 150 10 360 kg /day

Assuming the organic loading in the pond is 300 kg/ha/day.

Surface area required 2BOD content 3601.2 ha 12000m

Organicloading 300

Assuming length of the pond (L) as twice of its width (B)

L B 12000

2 B B 12000

B 77.46m say77.50m

L 2 B 2 77.50 155m

Using a pond with effective depth as 1.2 m, we get

Capacity of pond 3155 77.5 1.2 14415 m

But Capacity Sewage flow per day × Detention time in days

144156

3

2.4 10Detention timein days

10

Detention time3

6

14415 106days

2.4 10

Hence using an oxidation pond with length 155 m; width = 77.5 m

and over all depth 1.2 + 1 2.2 m and a detention period of 6 days.

Design of inlet and outlet pipe

Assuming an average velocity of sewage as 0.9 m/s and daily flow for 8 hrs only

Discharge6

3

3

2.4 100.0833 m /sec

10 8 60 60

Area of inlet pipe required 2Discharge 0.08330.09 m

Velocity 0.9

Diameter of inlet pipe44 0.09 10

33.85 cm 34cm

20 Marks


Sol. Rapid hardening cement (IS : 8041)

• This cement is manufactured by grinding OPC more finely.

• It contains more C3S (more than 50%) and less C

2S.

• It is used in situations where a rapid development of strength is desired (example when formwork is to be removed early for reuse.)

Sulphate Resisting Portland Cement (SRPC) (IS : 12330)

• It is similar to ordinary portland cement except that it contains very low C3A content and ground

finer than OPC.

• Amount of C2S & C

3S will be same & C

3A is restricted to low value (< 5%).

• It is used in those structure which are in contact with soil such as foundation, basement, retainingwall etc.

• It is used in canal lining.

• It is strongly recommended for structures in sea water, coastal area and marshy lands.

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BMC + Environment + Survey 11ZONE TECHPortland Pozzolana Cement (IS : 1489)

• Manufactured by grinding portland cement clinker and pozzolana (usually fly ash 10 to 30% bymass of PPC).

• Pozzolana reduces heat of hydration.

• Pozzolana (burnt clay, shale, or fly ash) has no cementing properties itself but has the property ofcombining with lime to produce a stable lime-pozzolana compound which has definite cementitiousproperties.

• Fineness should not be less than 3000 cm2/gm.

• It has low heat evolution and is used in the places of mass concrete such as dams and in places ofhigh temperature.

Q.35

Sol. Given

Population 150 ; Discharge, Q 135 l.p.c.d.

So, design discharge, dQ 135 150 20250 /d l

Let us assume : detention time, dt 24hours

Cleaning period 12 months

and rate of accumulation of sludge 40 /c /year l

Now, 1V dQ t

320250 1 day 20250 /20.25 m l

2V Rate of accumulation×Cleaing period

40 150 1 year

36000 6 m l

Total volume of tank equired 31 2V V 20.25 6 26.25 m

Let us assume depth H 1.5m

Surface area, A 2V 26.2517.5 m

H 1.5

Let L

B ratio be 2.

A2L.B. 2B

17.5 22B

B 2.95 m 0.9m

Hence result is okay.

Desing parameters L 2B 2 2.95 5.9m

B 2.95 m

H 1.5 m

and also we provice a free board of 0.3 m.


Sol.

Q.37

Sol. Fundamental Lines and Desired Relations:The fundamental lines of a transit are:1. The vertical axis.

2. The horizontal axis (or trunnion axis or trasnit axis)3. The line of collimation (or line of sight)

4. Axis of plate level.5. Axis of altitude level.

6. Axis of the striding level, if provided.

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BMC + Environment + Survey 13ZONE TECHDesired Relations: Figure shows the relation ship bteween the line of sight, the axes and the circlesof the theodolite. The following relationship should exist.

90°

90°

Transit axis

(Horizontal axis)

Line of sight

Intersectionof cross-hairs

Vertical axis

Horizontal circle

Horizontalcircle index

Vertical

circle

Vertical circle index

Optical centre of objective

Point to which all theodolite observationsare referred

90°

1. The axis of the plae level must lie in a plane perpendicular to the vertical axis.

It this condition exists, the vertical axis will be truly vertical when the bubble is in the centre ofits run.

2. The line of collimation must be perpendicular to the horizontal axis at its intersection with thevertical axis. Also, if the telescope is external focusing type, the optical axis, the axis of the objectiveslide and the line of collimation must coincide.

If this condition exists, the line of sight will generate a vertical plane when the telescope isrotated about the horizontal axis.

3. The horizontal axis must be perpendicular to the vertical axis.

If this conditions exists, the line of sight will generate a vertical plane when the telescope isplunged.

4. The axis of the altitude level (or telescope level) must be parallel to line of collimation.

If this condition exists, the vertical angles will be free from index error due to lack of parallelism.

5. The vertical circle vernier must read zero when the line of collimation is horizontal.

If this condition exists, the vertical angles will be free from index error due to displacement ofthe vernier.

6. The axis of the starting level (if provided) must be parallel to the horizontal axis.

If this condition exists, the line of sight (if in adjustment) will generate a vertical plane when thetelescope is plunged, the bubble or striding level being in the centre of its run.

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Sol. Preservation of Timber

1. Objects of preservation of timber

The preservation of timber is carried out to achieve the following three objects:

• To increase the life of timber structures,

• To make the timber structures durable, and

• To protect the timber structures from the attack of destroying agencies such as fungi, insects, etc.

2. Requirements of a good preservative : Following are the requirements of a good preservative :

• It should be capable of covering a large area with small quantity.

• It should be cheap and easily available.

• It should be durable and should not be affected by light, heat etc.

• It should be free from unpleasant smell.

• It should be non-inflammable.

• It should be quite efficient in killing fungi, insects, etc.

• It should be safe and harmless for persons and animals.

• It should give pleasant appearance to the timber after being applied over it.

• It should not affect the strength characteristics of timber.

• It should not be easily washed away by water.

• It should not corrode the metals with which it comes into contact.

• It should offer high resistance to the moisture and dampness.

• Its penetrating power into wood fibres should be high. It is necessary for the preservative to thepenetrate at least for a depth of 6 mm to 25 mm.

3. Types of preservatives

Following preservatives are commonly used for the preservation of timber.

• Ascu treatment

• Creosote oil

• Chemical salts

• Oil Paints

• Coal tar

• Solignum paints

(i) Ascu treatment

• The Ascu is special preservative which is developed at the Forest Research Institute, Dehradun.

• Its composition is as follows:

(a) Parts by weight of hydrated arsenic pentoxide, (As2O

5, 2H

2O)

(b) Parts by weight of blue vitroil or copper sulphate, (CuSO4, 5H

2O)

(c) Parts by weight of potassium dichromate, (K2Cr

2O

7) or sodium dichromate (Na

2Cr

2O

7, 2H

2O).

• This material is available in powder form. To prepare a solution of this material, six parts byweight of Ascu are mixed in 100 parts by weight of water. The solution is then sprayed orapplied on timber surface.

• This preservative gives timber protection against the attack of white ants. The surface treatedwith this preservative can be painted, polished, varnished or waxed. The solution is odourless.

(ii) Chemical salts

• These are water-borne preservatives and they are mostly salts dissolved in water. The usualsalts used are copper sulphate, mercury chloride, sodium flouride and zinc chloride.

• The solutions are prepared from these salts and they are applied on the timber surface. Thesepreservatives are odourless and non-inflammable.

• The treated surface can be painted or varnished after drying. These preservatives have goodpenetration.

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BMC + Environment + Survey 15ZONE TECH(iii) Coal tar

• The timber surface is coated with hot coal tar with the help of brush. The coal tar becomesworkable when heated. The process is known as the tarring.

• The coal tar has unpleasant smell and appearance. It makes timber unsuitable for painting. Hencethe tarring is adopted for frames of doors and windows, rough timber work, etc. and it is foundto be most useful for parts embedded in ground because of its cheapness and effective resistance.The coal tar is fire-resistant.

(iv) Creosote oil

• In this case, the timber surface is coated with creosote oil. The process is known as the creosoting.The creosote oil is obtained by the distillation of tar.

• The creosote oil is one of the best antiseptic i.e., substance poisonous for wood-attacking fungi.

• It is a black or brown liquid, weakly affected by water, harmless to wood or metal, inflammable,with an unpleasant odour and having low wood-penetrating ability to the extent of 1 mm to 2mm only.

• The creosoting practically doubles the life of timber and it is generally adopted for piles, poles,railway sleepers, etc.

• The process of creosoting proves to be costly.

(v) Oil paints

• The timber surface is coated with 2 or 3 coats of oil paint. The wood should be seasoned. Otherwisesap will lead to the decay of timber.

• The oil paints preserve timber from moisture and make it durable.

Q.39

Sol. Derivation of stoke's law:

When a solid particle settles down in water, its downward settlement is opposed by the drag forceoffered by the water. The effective weight of the particles (i.e. actual weight-buoyancy) causes theparticle to accelerate in the beginning, till it attains a sufficient velocity (V

s) at which the drag force

becomes equal to the effective weight of the particle. After attaining that velocity, the particle fallsdown with that constant velocity (V

s).

Now, the drag force offered by the fluid is given by Newton's law, as

Drag force CD .A. w .

2V

2...(i)

where CD Coefficient of drag

A area of particle

w Density of water

V Velocity of fall

Note: This drag force increases with the increasing velocity, till it becomes equal to the effectiveweight of the particle, at that time, V becomes equal to V

S.

The effective weight of the particle

Total weight – Buoyancy 4 3

s w

4 4r . r

3 3

4s w

4r –

3 ...(ii)

[Weight Volume × Unit weight]

Where, r radius of particle

s unit weight of particle

w unit weight of water

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BMC + Environment + Survey 16ZONE TECHequation (i) and (ii) will become equal when V becomes equal to V

S in eqution (i).

CD.A. w .

2sV

2 3

s w

4r –

3

But, A 2r

CD. 2r . w .

2sV

2 3

s w

4r –

3

2sV

s w

w

–4.

3 .D

Now, s s .g

w w .g

s w– s wg – se

w

g. 1

s w– wg. G – 1

Equation (iii) then becomes.

2sV w

w D

g G – 1 .d4.

3 .C

or V

s

1/2

D

4gd G – 1

3C

The drag coefficient CD changes and depends upon the flow regime surrounding the particle.

The drag coefficient CD) has been emparically connected with reynolds number (Re) by thomas camp

by a curve.

The value of CD is calculated by

104

103

102

10

1

10–2

10–3 10–2 10–1 1 10 102 103 104 105 106

Stokes'law

D

24 3Equation C 0.34

Re Re

Spheres (Observed) Disks (observed)

Cylinders (observed)length = 5 diameters

D

24C

Re

New

ton

's D

rag

Co

effi

cien

t (C

) D

Reynold's number, Re

Curve showing relation between C and Re D

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(i) If Re < 1, CD

24

Re

(ii) If 1 < Re < 1000, CD

24 30.34

Re Re

(iii) If Re > 104, CD 0.4 (constant)

where Re V.d

v

Re Reynold number

d spherical diamter of the particle

V Velocity of sphere (m/sec)

v kinematic viscosity of water (m2/sec)

So, setting velocity for small particle falling under laminar (quiscent condition)

VS

4.g G 1 .d

324

Re

2sV 4

g G – 13

. sg V .dRed. G 1 .d

24 18 v

Vs

2g dG 1 .

18 v

• Since the viscosity (v) is dependent upon the temperature, the above equation can be furthermodified and written as

Vs 2 3T 70

418 G 1 .d100

for d < 0.1 m

where, T Temperature of water in °C;

Vs is in mm/sec.

d is in mm.

• The above stokes equation are valid particle size less than 0.1 mm; in whcih the viscous force ispredominant over the inertial force. This is called stream line setting.

• If however, the setting particles are larger than 1.0 mm, the nature of setting becomes turbulentsetting. and is governed by Newton's equation given by

Vs 1.8 g.d G 1 for d > 1.0 mm

• For particle size between 0.1 mm and lie in the transition zone setting velocity given as

Vs 3T 70

418 G 1100

for 0.1 mm < d < 1 mm

ZONE TECH BMC + Environment + Survey 1 · ZONE TECH BMC + Environment + Survey 4 Q.15 Sol. Laying...

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Transcript of ZONE TECH BMC + Environment + Survey 1 · ZONE TECH BMC + Environment + Survey 4 Q.15 Sol. Laying...