BPSC AE Civil Paper 6 (Civil) Mock Test - 1 - Civil Engineering (CE) MCQ

Concept:

Biochemical Oxygen demand (BOD):

It is the total amount of oxygen required to oxidize the biodegradable organic matter present in wastewater through microbial utilization of organics.

BOD = (Initial Dissolve Oxygen - Final Dissolve Oxygen) × Dilution Factor

where

Calculation:

Given:

DOInitial = 8 mg/L

DOFinal = 2 mg/L

Dilution Factor = 300/2

BOD = (8-2) x (300/2) = 900 mg/L 

According to Lacey's theory, the following formulae have been given below:

Hydraulic mean depth,

Area of the channel section,

A = Q / V

Wetted perimeter,

P = 4.75√Q

Regime mean velocity,

Bed Slope,

Calculation:

Given data,

Q = 100 m³/s

P = 4.75√Q = 4.75√100 = 47.5m

Concept:

Burmister’s Method:

Assumptions

• Materials in each layers are isotropic, homogeneous and elastic.
• Pavement forms a stiffer layer having higher value of E than that of subgrade.
• Layers are in constant contact.
• Surface layer is infinite in horizontal direction but finite in vertical direction.

This method gives the following design deflection values for pavements with different layers –

1. For flexible pavement –

1. For rigid pavement –

Where, p = contact pressure at road surface due to wheel load (kg/m²)

E_s = modulus of elasticity of subgrade (kg/cm²),

a = radius of contact area(cm) and

F₂ = deflection factor which depends upon Es/EP and h/a, for single layer system F₂ = 1.

Formula used:-

Design deflection for single-layered flexible pavement is given by,

Radius of contact area is given by,

Calculation:

Wheel Load, P = 40 kN

Modulus of elasticity for subgrade and pavement, ES = EP = 25 MPa

Tyre pressure, p = 0.60 MPa

Radius of contact (a)

Design deflection for flexible pavement

The correct statements are:-

(i) manometers are easy to operate

(ii) manometers do not require frequent calibration

Key Points :

• manometers are a device used to measure the pressure of the fluid by balancing of the fluid column
• They are generally made up of Glass
• They are generally a tube of Glass in U - Shape
• They are simple in construction and are easy to operate
• They do not require frequent calibration
• They are generally calibrated once a year.

Additional Information

Types of manometer :

• piezometer is wed to measure very low pressure
• Differential monometers are used to measure the difference of pressure between two points.

Time of concentration:

• Time of Concentration is the time required by the entire drainage area to contribute to the runoff is called the time of concentration or time required by the most extreme point in the drainage to reach the point of interest.
• In Other Words, it is the maximum time taken by the rainwater to reach the outlet of the basin.
• The rainfall intensity corresponding to a duration of T_c and desired period of exceedance, P is found from the rainfall frequency-duration relationship for the given catchment area.
• This relationship is given by

Where, I_C = Rainfall intensity, T_C = Time of concentration, T = Return period = 1/P, and K, a, x, n are coefficients corresponding to a particular location

Additional Information

Time of concentration is also given by Kirpich equation

T_C = 0.01947 x L^0.77 × S^-0.385

Where T_C = Time of concentration in minutes, L = Maximum length of travel of water in meters, S = Slope of the catchment = Δ H/L, Δ H = Head difference

Extra Widening

The extra width of carriageway that is required on a curved section of a road over and above that is required on a straight alignment is known as Extra Widening.

Extra widening of road is given by,

Where,

Wm = Mechanical widening, W_ps = Psychological widening, n = number of lanes, l = length of wheelbase, R = Radius of curve, V = Velocity of vehicle (in kmph)

Note:

Reasons to provide extra widening are:

(i) To avoid off tracking due to rigidity of wheelbase

(ii) To counteract transverse skidding

(iii) To increase the visibility at curves

(iv) To encounter psychological tendency while overtaking operation

Important Point:

IRC recommended values of extra widening for single and two-lane pavement are given below:

1) If R > 300 m, then extra widening is not provided.

2) If R < 50 m, Then extra widening is provided at the inner edge.

3) If 50 < R < 300 m, then extra widening is provided at both edges.

Concept:

NOTE: Length is not given in the question or given options, so we have to calculate discharge per unit length in the given weir

Weir or notch is a physical structure of masonry constructed across the channel width to calculate the discharge of the channel section.

Rectangular (suppressed) Notch:

The discharge through a rectangular notch weir is,

Where, Q = discharge of fluid, Cd = Coefficient of discharge and H = height of water above the notch

Additional Information

Triangular Notch:

A V-notch weir is also called the triangular notch or weir. The discharge over a triangular weir or notch is given by the:

Where, Q = discharge of fluid, Cd = Coefficient of discharge, θ = Notch angle and H = height of water above the notch

Trapezoidal weir (or) Notch:

Where, (θ/2) = weir angle of inclination with the vertical.

C_d1= Coefficient of discharge for rectangular portion.

C_d2= Coefficient of discharge for the triangular portion

Concept:

DAD curve:

• The areal characteristics of a rain storm are represented by a depth-area-duration curve. Once the sufficient rainfall records for the region are collected the basic or raw data can be analyzed and processed to produce useful information in the form of curves or statistical values for use in the planning of water resources development projects.
• Many hydrologic problems require an analysis of time as well as areal distribution of storm rainfall. Depth-Area-Duration (DAD) analysis of a storm is done to determine the maximum amounts of rainfall within various durations over areas of various sizes
• The depth area curve for a particular storm can be calculated with the equation

:

Where P is average depth of rainfall over an Area (in cm)

P0 is the highest amount of rainfall at the storm center (in cm)

A is area (km2)

K and n are constants for a particular region: n is < 1.

With increase in Area P value decreases.

To find out how much of rainfall will occur in an area by converting rainfall data to areal rainfall data, Depth area duration curve is used.

DAD curve expresses graphically the relation between progressively decreasing average depth of rainfall over a progressively increasing area from the centre of the storm outward to its edges for a given duration of rainfall.

For a given area the maximum average depth of rainfall increases with storm duration.

Concept:

Forms of the precipitation are as follows:

Concept:
PO value:

• The Odour in water changes with temperature. the water Odour is tested at 20^oC to 25^oC
• The apparatus used to measure Odour in water is known as osmoscope.
• A commercial osmoscope is graduated with a PO value from 0 - 5.

PO value is 4 then the interpretation is a very distinct Odour.

Readily available moisture-

• It is that portion of the available moisture that is most easily extracted by the plants and is approximately 75 to 80% of the available moisture.

Field Capacity-

• Immediately after a rain or irrigation water application, when all the gravity water has drained down to the water table, a certain amount of water is retained on the surfaces of soil grains by molecular attraction and by loose chemical bonds. This water cannot be easily drained under gravity and this is called field capacity.

Permanent wilting point-

• It is the water content at which the plant can no longer extract sufficient water for its growth, and wilts up.

Soil moisture deficiency-

• The water required to bring the soil moisture content of a given soil to its field capacity is called field moisture deficiency or soil moisture deficiency.

Concept:

In the case of a centrifugal pump, the power is transmitted from the shaft of the pump to the impeller and then from the impeller to the water. The following are the important efficiencies of a centrifugal pump:

Manometric Efficiency (ηman): It is the ratio of the manometric head to head imparted by the impeller to the water.

Mechanical Efficiency (ηm): It is the ratio of the power available at the impeller to the power at the shaft of the centrifugal pump.

Overall Efficiency (ηo): It is defined as a ratio of the power output of the pump to the power input to the pump.

ηo = ηman × ηm

Volumetric efficiency: It is the ratio of the quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller.

Concept-

Hazardous waste options:

A three-stage hierarchy of options for handling hazardous wastes is:

First stage:

• The top tier includes plant options such as process manipulation, recycling, and reuse options that reduce the production of hazardous waste in the first place. It also contains the most desirable options.

Middle stage:

The middle stage highlights processes that convert hazardous waste to less hazardous or non-hazardous substances include

• Incineration
• Land treatment
• Ocean and atmospheric assimilation
• Chemical, physical, and biological treatments
• Thermal treatments

Last stage:

• This is the stage that is the least preferred or desirable tier that is perpetual storage the cheapest alternative.
• A few processes include landfill, underground injection, arid region unsaturated zone, surface impoundments, salt formations, and waste piles.

Flood routing: It is the technique of determining the flood hydrograph at a section of a river by utilizing the data of flood flow at one or more upstream sections.

Hydrologic routing methods employ the equation of continuity.

In its simplest form, inflow to river reach is equal to the outflow of the river reach plus the change of storage.

I = O + (ΔS/Δt)

Where,

I = Average inflow to the reach during ∆t,

O = Average outflow to the reach during ∆t, and

ΔS = Change in storage

Note:

In the case of hydraulic routing, the continuity equation together with the equation of momentum is used.

Weep holes are provided in masonry walls, parapets, wing walls and earth retaining structures for safe drainage of rain water

Weep holes serve the purpose in the following ways.

1. Relieving hydrostatic pressure on the walls.
2. Reducing water pressure, thus reducing the reinforcement requirements and thickness of walls
3. Providing ventilation facility

Canal drop:

It is a structure constructed across a channel to permit lowering down of water level in order to dissipate the surplus energy possessed by the falling water which may otherwise scour the bed and banks of the channel.

Canal Escape:

During floods/rains, when the canal carries water beyond its full capacity, water is released through Canal Escapes.

Canal Cross regulators:

It is provided to admit water into the off taking canal and to regulate the supplies into the canal ( Depth of flow). It also regulated the discharge to be passed into the canal and controls the silt entry into the canal.

Canal outlets:

A canal outlet or a module is a small structure built at the head of the watercourse so as to connect it with a minor or a distributary channel. In other words, canal outlets are devices to regulate the flow of water from a bigger channel into a smaller one.

Specific energy

In open channel flow, specific energy ( E ) is the energy length, or head, relative to the channel bottom. Specific energy is expressed in terms of kinetic, potential, and internal energy.

E = y + v²/2g

Q=A x V ,Q = Discharge in m³/s , V = velocity of water , y = depth

Q = B x y x V

Calculation:

Given data;

Width = 6 m

depth of water = 3 m and

discharge = 18 m³/s

The specific energy ( E ) is

Note:

The most appropriate answer is option 1.

Catch basin:

• Catch basins are provided to stop the entry of heavy debris present in the storm water into the sewers.
• At the bottom of the basin, space is provided for the accumulation of impurities.
• The perforated cover is provided at the top of the basin to admit rainwater into the basin.

• A hood is provided to prevent the escape of sewer gas.

Lamp hole:

• It is an opening or hole constructed in a sewer for the purpose of lowering a lamp inside it.

• It consists of stoneware or concrete pipe, which is connected to a sewer line through a T-junction.

Flushing tank:

• An arrangement to hold and throw water into the sewer for the purpose of flushing.

• When the gradient of the sewers is flat and the velocity of sewage is low, the suspended matter starts settling and causes clogging of the sewer, at such places, where self-cleansing velocity is not available, a flushing tank is provided to flush the sewer.

Gullies:

• Gully is a type of drainage inlet of the drainage system. Though it is designed to catch stormwater, road gullies and catch pits are intended to catch stormwater at different locations.

Deep beams are structural elements loaded as simple beams in which a significant amount of the load is carried to the supports by a compression force combining the load and the reaction. As a result, the strain distribution is no longer considered linear, and the shear deformations become significant when compared to pure flexure.

In view of ample shear strength, deep beams are primarily recommended as transfer girders. These members transfer loads through-loading face to supports in the transverse direction. The deep horizontal members predominantly fail in shear rather than flexure. These beams are characterized with small span-to-depth ratio. Pile caps, corbel, brackets, foundation walls and off-shore structures are few examples of RC deep beams.

According to IS 456-2000 a beam shall be deemed to be a deep beam when the ratio of effective span-to-overall depth, l/D is less than:

1) 2.0, for simply supported beam; and

2) 2.5, for a continuous beam.

Though different codes define deep beams in different clear span-to-depth ratios, as a general rule deep beams are recognized by their relatively small span-to-depth ratio.

Hence, Deep beams are designed for bending moment and checked for shear.

Concept:

According to Clause, 3.2.2.1 of IS: 4111 (Part 1) - 1986:

The spacing of manholes above 90 to 150 m may be allowed on straight runs for sewers of diameter above 900 to 1500 mm and above 150 to 200 m the spacing of manholes may be on straight runs for sewers of 1.5 to 2.0 m dia, which may further be increased up to 300 m for sewers of over 2.0 m diameter. A spacing allowance of 100 m per 1 m dia of sewer is a general rule in the case of very large sewers.

Additional Information:

According to Clause 3.2.1 of IS: 4111 (Part 1) - 1986:

• Manholes should be built at every change of alignment, gradient, or diameter, at the head of all sewers and branches, and at every junction of two or more sewers.
• On sewers that are to be cleaned manually which cannot be entered for cleaning or inspection the maximum distance between manholes should be 30 m.

Concept:
Elastic modulus of concrete,

E_c = 5000 x √f_ck

where, fck = grade of concrete

Long-term elastic modulus of concrete

E_θ = E_c / (1 + θ)

θ = creep coefficient

Calculation:

Modulus of elasticity as per IS 456: 2000 is given by

E = 5000√65 = 40311 MPa = 40.311 GPa ≈ 40GPa

Feeder canals: It is constructed with the idea of feeding two or more canals. When the main canal is divided into two canals then it is called a feeder canal. e.g. Lower Chenab canal feeder.

Irrigation canal: A canal aligned along the boundaries of cultivatable areas in order to supply water for the purpose of agriculture is said to be an irrigation canal.

Inundation canals: These are long canals taken off from large rivers. They receive water when the river stage is high especially during the flood. Thus they are used to divert the flood water of rivers.

Perennial Canals: These canals are lined to dams and barrages and receive or carry water throughout the year. They never dry and able to irrigate vast areas.

Carrier canals: It is the one which besides doing irrigation carries water for another canal. It’s a link canal and has an outlet e.g. Upper Chenab Canal in Punjab.

Navigation canal: A canal that is constructed especially for navigational purposes is known as a navigation canal. The water level required in a navigation canal is generally a lot higher to accommodate large ships, vessels, etc.

Flanged joint:

• This joint is commonly used for joining pipes in pumping stations, filter plants, hydraulic laboratories, boiler houses, etc.
• These joints are preferred due to the easy process of assembly and disassembly, however, these connections are costly.
• These joints can be disassembled and re-assembled when required.
• A pipe has flanged ends on both sides of the pipe length. Both ends of pipes are joined at a proper level near one another. A hard rubber washer is placed between flanges and bolted. Flanges are generally fixed to the pipe by welding or threading.
• In certain cases, a flange-type joint is also called a lap joint. It may also be made by forging the process and machining the pipe end. There is no leakage in flanged joints even after rapid temperature fluctuations.

Additional Information

Pipe Joints

Pipes are connected with the help of joints. A variety of joints are used in the assembly of pipes. Connecting two or more pipes together is called a fitting. Various types of joints could be used in a pipe as per the requirement. Joints are also used for multiple pipe connections and are an important component of the plumbing system. Generally, the pipe joint fitted can easily sustain the pressure created in the pipe.

Types of pipe joints Various types of pipe joints are as follows:

1. Threaded joint
2. Welded joint (butt welded, socket welded)
3. Brazed joint
4. Soldered joint
5. Grooved joint
6. Flanged joint
7. Compression joint

Gross Head:

• The gross head is the difference between the water level at the reservoir and the water level at the tailrace.

Additional Information

Net or Effective Head:

• The head available at the inlet of the turbine is known as the net or effective head.

The hardness of water:

• Hardness in water is that characteristic which prevents the formation of sufficient leather or foam when such hard water is mixed with soap.
• It is usually caused by the presence of calcium and magnesium salts present in water, which form scum by reaction with soap.

Water softening:

• The process of removal of hardness from water is known as Water softening.

Removal of hardness;

1. Temporary hardness:

• The temporary or carbonate hardness is caused by carbonates and bicarbonates of Ca and Mg or bivalent cations.

The methods of removing temporary hardness:

• Boiling
• Addition of lime.

2. Permanent hardness:

The permanent or non-carbonate hardness, which is caused by the sulphates, chlorides and nitrates of Ca and Mg is removed by special methods.

The methods of removing permanent hardness

• Lime soda process
• Base exchange process
• Demineralization​

Lime Soda Process

• Chemicals normally used are lime {calcium hydroxide, Ca(OH)₂} and soda ash (sodium carbonate, Na₂CO₃).
• Lime is used to remove chemicals that cause carbonate hardness.
• Soda ash is used to remove chemicals that cause non-carbonate hardness.
• Lime soda softening cannot produce water completely free of hardness because of the solubility of CaCO₃ and Mg(OH)₂.
• Thus the minimum calcium hardness that can be achieved is about 30 mg/L as CaCO₃, and the magnesium hardness is about 10 mg/L as CaCO₃.

Ion-exchange method:

• ​This method is also called the zeolite/permutit process.
• In this method, the permanent hardness of water is removed by using resins.
• Ca⁺⁺/Mg⁺⁺ ions are exchanged with Cl^-, SO^-2₄ ions are exchanged with anion exchange resin (RNH₂OH).
• Demineralized water is formed in this process.
• Hydrated sodium aluminium silicate is zeolite/permutit.
• For the sake of simplicity, sodium aluminium silicate (NaAlSiO₄) can be written as NaZ.
• When this is added to hard water, exchange reactions take place.

Permanent hardness can also be removed by:-

Treatment with washing soda (sodium carbonate):-

• Washing soda reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates.
• Sodium carbonate is water-soluble in nature and hence, adds a large number of carbonate ions to the water.
• Because of this, the calcium ions come from hard water and the carbonate ions from sodium carbonate.

Note: Permanent Hardness is not removed by Boiling.

Acceptable Indoor noise levels for various types of buildings

Important Points

Acceptable outdoor noise levels in residential areas

Grade compensation:

• The grade compensation is the reduction in gradient on a horizontal curve.
• As per IRC, grade compensation is given by (30 + R)/R % and limited to maximum of 75/R % , where R = Radius of the curve in 'm'.
• Grade compensation is not required for the grades flatter than 4%.

And the given gradient is 4% only, so we can't do any grade compensation to it, as the value will go less than 4 % and it will fail the above criteria

The unit hydrograph (UH) of a catchment is defined as the hydrograph resulting from an effective rainfall of 1 cm evenly distributed over the basin during the time T. We can plot any no. of UHs for a given basin by changing the duration of rainfall i.e. we may have 2 hr UH, 3hr UH, 4 hr UH… so on.

Therefore, theoretically an infinite number of unit graphs are possible for a given basin.

Hydrograph is the graphical representation of discharge Vs time at any given point on stream.

The following are some factors which affect the hydrograph:

1. Rainfall characteristics: rain fall duration, its distribution over the basin, rainfall intensity.

2. Catchment characteristics: slope of basin, basin area, shape of basin.

3. Land use pattern

4. Soil moisture conditions

Traffic Density

• It can be defined as the number of vehicles per unit length.
• Unit - Veh/Km

Traffic Capacity

• the maximum number of vehicles in a lane or a road that can pass a given point in unit time, usually an hour, i.e., vehicles per hour per lane or roadway.
• Unit - Veh/Hr/lane

Traffic volume:

The number of vehicles moving in a specified direction on a roadway that passes a given point during a specific unit of time is called traffic volume.

The relation between traffic (density, volume, and speed) is given by:
Traffic volume(q) = Speed(v) x Traffic density(k)

Where,

q is in veh/hr, v is in km/hr, k is in veh/km

Important PointsThe relationship between the three different fundamental quantities are depicted below:

Flow-through hump:

​

• When ΔZ is equal to ΔZm (ΔZm is the minimum height of hump for critical flow or maximum height of hump for which upstream flow is not affected) then point Q corresponding to the depth of flow y2 shift to point C corresponding to the depth of flow yc, E1 = Ec + ΔZm, it means at ΔZm, the flow at downstream becomes critical and at ΔZ < ΔZm, the flow over hump remains subcritical.

For avoiding the afflux at downstream, apply energy equation u/s and d/s, we get

E1 = Ec + ΔZm

Where, E₁ = Energy at U/S, E_c = Energy at D/S and ΔZ_m = Change in hump height

ΔZm = 3 - 2.5 = 0.5 m