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Past Questions — 2026
The maximum permissible shear stress is given in IS : 456-2000 is based on:
A)
Diagonal tension failure
B)
Diagonal compression failure
C)
Flexural tension failure
D)
Uniaxial compression
In reinforced concrete beams, shear forces create principal stresses. The combination of shear stress and longitudinal bending stress results in principal tensile stresses acting diagonally (typically at 45 degrees to the beam axis). Since concrete is weak in tension, it cracks perpendicular to these principal tensile stresses, leading to 'diagonal tension' cracks. IS 456:2000 defines the maximum permissible shear stress ($ au_{c,max}$) to ensure that the concrete does not fail by crushing of the 'compression struts' formed between the diagonal cracks, but the fundamental mechanism that governs the need for shear reinforcement and the limit of shear capacity in RCC is the prevention of diagonal tension failure. Specifically, the limit $ au_{c,max}$ is set to prevent the concrete from crushing in the compression zone (diagonal compression), but the overall shear design philosophy in IS 456 is based on the fact that shear failure in beams is essentially a diagonal tension failure.
A sewer which receives discharge of a number of house sewers is called a:
A)
Common sewer
B)
Trunk sewer
C)
Lateral sewer
D)
Branch sewer
In a sewerage system, sewers are categorized based on their position and the volume of discharge they carry.
1. **Lateral Sewer**: This is the smallest sewer that collects waste directly from a single house or building and carries it to a branch sewer.
2. **Branch Sewer (or Sub-main sewer)**: This sewer receives discharges from a number of lateral sewers (house sewers). Therefore, a sewer that receives discharge from several house sewers is defined as a branch sewer.
3. **Trunk Sewer**: These are larger sewers that collect discharge from several branch sewers and carry it toward the main sewer or treatment plant.
4. **Common Sewer**: This term generally refers to a combined sewer system that carries both sanitary sewage and storm water in a single pipe, rather than referring to a specific hierarchical level of collection.
Since the question asks for the sewer that receives discharge from a number of house (lateral) sewers, the correct answer is the Branch sewer.
The hydraulic mean depth or the hydraulic radius is the ratio of:
A)
Velocity of flow and area of flow
B)
Area of flow and wetted perimeter
C)
Wetted perimeter and diameter of pipe
D)
Area of flow and diameter of pipe
The hydraulic radius (R), also known as the hydraulic mean depth, is a fundamental parameter in open channel flow and pipe flow analysis. It is defined as the ratio of the cross-sectional area of the flow (A) to the wetted perimeter (P). Mathematically, it is expressed as R = A / P.
- Area of flow (A): The total cross-sectional area through which the fluid flows.
- Wetted perimeter (P): The length of the boundary of the cross-section that is in contact with the fluid.
Evaluating the options:
- Option (a) is incorrect because the ratio of velocity to area does not define a standard hydraulic property.
- Option (b) is correct as it matches the definition R = A/P.
- Option (c) is incorrect as the ratio of wetted perimeter to diameter is not the hydraulic radius.
- Option (d) is incorrect as the ratio of area to diameter is not the hydraulic radius.
The disposal of sewage into natural water courses such as streams, rivers, sea and lake is known as sewage disposal:
A)
By dilution
B)
By self purification
C)
By sedimentation
D)
By liquidification
Step-by-step reasoning: 1. Definition: Sewage disposal by dilution involves discharging untreated or partially treated sewage into a large body of water (like a river, lake, or sea). 2. Mechanism: The principle is that the large volume of the receiving water body dilutes the concentration of pollutants to a level where they are less harmful and can be processed by the natural environment. 3. Analysis of other options: (b) Self-purification is the natural process (physical, chemical, and biological) that occurs *after* the sewage has been diluted and discharged, but the act of disposal itself is called dilution. (c) Sedimentation is a primary treatment process where solids settle at the bottom; it is not a method of final disposal into water courses. (d) Liquefaction is a physical process (often related to soil or gas) and is not a term used for sewage disposal methods. Therefore, the correct term for the act of discharging sewage into natural water courses is disposal by dilution.
The area of longitudinal steel reinforcement in column should not be:
A)
Less than 0.8% of the area of concrete section required for direct load alone
B)
More than 6% of gross sectional area of column
C)
Less than 1 % of the area of concrete section
D)
Both (a) & (b)
According to IS 456:2000 (the Indian Standard code of practice for Plain and Reinforced Concrete), the requirements for longitudinal reinforcement in columns are as follows:
1. Minimum Reinforcement: Clause 26.5.3.1 states that the area of longitudinal reinforcement shall not be less than 0.8% of the gross cross-sectional area of the column. This is to prevent sudden failure and to handle accidental eccentricity.
2. Maximum Reinforcement: Clause 26.5.3.1 also specifies that the maximum area of longitudinal reinforcement shall not exceed 6% of the gross cross-sectional area of the column. However, in practice, it is often limited to 4% to avoid congestion of reinforcement at lap joints.
Evaluating the options:
- Option (a) refers to the minimum limit of 0.8% (though the phrasing 'required for direct load alone' is a slightly older way of describing the gross area requirement).
- Option (b) refers to the maximum limit of 6% of the gross sectional area.
- Option (c) is incorrect because the minimum is 0.8%, not 1%.
Since both (a) and (b) represent the regulatory limits (minimum and maximum) set by the code, the correct answer is (d).
The percentage ratio of the oxygen available in sewage to the oxygen required to satisfy one stage of bio-chemical oxygen demand(BOD) is termed as:
A)
Bio-oxygen demand
B)
Oxygen consumed
C)
Chemical oxygen demand
D)
Relative stability
In environmental engineering and wastewater treatment, 'Relative Stability' is a parameter used to assess the stability of sewage. It is defined as the ratio of the oxygen available in the sewage to the oxygen required to satisfy the biochemical oxygen demand (BOD) of the sewage, expressed as a percentage.
Formula: Relative Stability (%) = (Dissolved Oxygen / BOD) × 100.
Why other options are incorrect:
- a. Bio-oxygen demand: This is a misnomer for Biochemical Oxygen Demand (BOD), which is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material, not a ratio.
- b. Oxygen consumed: This refers to the actual amount of oxygen used up during the degradation process, not a percentage ratio.
- c. Chemical oxygen demand (COD): This is the measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals via chemical oxidants, not a ratio of available to required oxygen.
The maximum free water cement ratio in RCC water tank is:
A)
0.35
B)
0.40
C)
0.45
D)
0.50
In the design of water-retaining structures (RCC water tanks), the primary objective is to ensure 'watertightness' and durability against seepage. According to standard codes of practice (such as IS 3370), the permeability of the concrete must be kept very low to prevent leakage and protect the reinforcement from corrosion. To achieve a dense, impermeable concrete matrix, the water-cement (w/c) ratio must be strictly limited. While very low ratios (0.35-0.40) are excellent for durability, the standard maximum permissible free water-cement ratio generally accepted for RCC water tanks to balance workability and impermeability is 0.45. Ratios higher than 0.45 (like 0.50) increase the porosity of the concrete, leading to higher permeability and a higher risk of leakage, making them unsuitable for liquid-retaining structures.
Curing of concrete for ___________ is satisfactory for normal Portland cement under normal temperature conditions.
A)
24 hrs
B)
7 days
C)
14 days
D)
30 days
Curing is the process of maintaining moisture and temperature conditions in freshly placed concrete to allow the hydration of cement to proceed, ensuring the concrete reaches its intended strength and durability. For Ordinary Portland Cement (OPC) under normal temperature conditions, the standard minimum curing period is generally accepted as 7 days. During this period, the majority of the initial strength gain occurs. While longer curing (14 or 28 days) is beneficial for higher strength or specific environmental conditions (like hot/dry weather), 7 days is considered the satisfactory minimum for standard applications. Option (a) 24 hours is only sufficient for the initial setting phase; options (c) and (d) are ideal for specialized high-strength requirements but exceed the standard 'satisfactory' minimum for normal conditions.
The quantity of surface water depends mainly upon:
A)
Permeability of soil
B)
Rainfall
C)
Snow
D)
Climate change
Step-by-step reasoning: 1. Surface water refers to water that collects on the ground surface, including rivers, lakes, streams, and runoff. 2. The primary source of input for the hydrological cycle on land is precipitation. 3. Among the given options, rainfall is the most direct and primary source of water that feeds surface water bodies. 4. While 'Permeability of soil' (Option a) determines how much of that rainfall becomes surface runoff versus infiltration, it does not provide the water itself. 5. 'Snow' (Option c) is a form of precipitation, but rainfall is the more general and dominant driver of surface water quantity globally. 6. 'Climate change' (Option d) is a long-term driver that affects patterns of rainfall, but it is not the immediate source of the water quantity. Therefore, the quantity of surface water depends mainly upon the amount of rainfall received in a catchment area.
For house drainage and lateral connections we shall use:
A)
Cast iron sewers
B)
Concrete sewers
C)
Masonry sewers
D)
Stone ware sewers
In environmental engineering and urban drainage design, the selection of sewer material depends on the location, load, and chemical nature of the effluent.
1. **Stoneware (Vitrified Clay) Sewers**: These are the preferred choice for house drainage and lateral connections. They are highly resistant to chemical corrosion (especially from domestic sewage), have a smooth internal surface to prevent clogging, and are cost-effective for smaller diameters typically used in residential connections.
2. **Cast Iron Sewers (Option a)**: While very strong and leak-proof, they are expensive and primarily used for building drains (vertical stacks) or in areas where high structural strength is required, rather than standard lateral connections.
3. **Concrete Sewers (Option b)**: These are generally used for larger main sewers or trunk sewers due to their size and strength. They are more prone to corrosion by sulfuric acid (H2S) produced in sewage compared to stoneware.
4. **Masonry Sewers (Option c)**: These are outdated and used only for very large, old trunk sewers. They are not suitable for small-diameter house drainage due to leakage issues and high construction effort.
The structure constructed in the form of a chamber and provided along the sewer line to admit clear rain water free from suspended and floating materials into the combined sewer is called:
A)
Manhole
B)
Flushing tanks
C)
Catch basin
D)
Drainage trap
A catch basin is a specialized structure used in combined sewer systems. It consists of a chamber (sump) constructed at the inlet of the sewer line from the street. Its primary function is to act as a grit chamber; as rainwater enters, the heavier suspended solids, floating debris, and grit settle to the bottom of the basin, allowing only the relatively clear water to enter the main sewer line. This prevents the sewer from becoming clogged with street debris.
Why other options are incorrect:
- a. Manhole: These are access points used for inspection, cleaning, and maintenance of the sewer line, not specifically for filtering rainwater.
- b. Flushing tanks: These are used in sewers with flat gradients to provide a sudden surge of water to flush out accumulated solids.
- d. Drainage trap: Traps are used in plumbing to prevent sewer gases from entering buildings by maintaining a water seal; they are not used for admitting rainwater into combined sewers.
Which of the following statement is wrong?
A)
The water carriage system is more hygienic
B)
There is no smell or sight nuisance in the case of water carriage system
C)
The sewers in the water carriage system being all underground do not impair the beauty of the place
D)
The initial cost of construction of water carriage system is very low
The question asks to identify the WRONG statement regarding the water carriage system of sewerage.
1. Statement (a) is correct: The water carriage system is considered the most hygienic because waste is transported quickly via water to a treatment plant, minimizing human contact with sewage.
2. Statement (b) is correct: Because the waste is enclosed in pipes and transported rapidly, there is minimal smell or sight nuisance compared to dry systems or open drains.
3. Statement (c) is correct: Since the network of sewers is laid underground, it does not interfere with the surface aesthetics or the beauty of the urban landscape.
4. Statement (d) is incorrect: The water carriage system requires extensive excavation, the laying of high-quality pipes, the construction of manholes, and the establishment of a sewage treatment plant (STP). Consequently, the initial capital investment (construction cost) is very high compared to simpler systems like the dry system or pit latrines. Therefore, stating that the cost is 'very low' is factually wrong.
The chemical reaction between cement and water is called:
A)
Watering
B)
Cement hydration
C)
Cement paste
D)
Cementing
The chemical process that occurs when cement is mixed with water is known as hydration. During this process, the compounds in the cement (primarily tricalcium silicate and dicalcium silicate) react chemically with water to form a hard, stone-like mass of hydrated compounds (such as Calcium Silicate Hydrate or C-S-H gel) and calcium hydroxide. This reaction is exothermic and is responsible for the setting and hardening of concrete.
Analysis of other options:
- (a) Watering: This is a general term for adding water and not a technical chemical term for the reaction.
- (c) Cement paste: This refers to the physical mixture of cement and water, not the chemical reaction itself.
- (d) Cementing: This is a general term for the act of joining materials together using cement, not the specific chemical process.
The centre to centre spacing of vertical stirrups , in a rectangular beam is:
A)
Increased towards the centre of the span of the beam
B)
Decreased towards the centre of the span of the beam
C)
Increased at the ends
D)
Decreased at the ends
In a reinforced concrete rectangular beam, vertical stirrups are provided primarily to resist shear forces. According to the shear force diagram (SFD) for a simply supported beam under uniform or point loads, the shear force is maximum at the supports (ends) and minimum (often zero) at the center of the span. Since the requirement for shear reinforcement is proportional to the magnitude of the shear force, stirrups are placed closer together (decreased spacing) near the supports to handle the high shear stress and further apart (increased spacing) towards the center of the span where the shear force is lower. Therefore, the spacing increases as you move from the ends toward the center.
The natural processed in which the oxygen of water of streams is consumed by sewage and at the same time, it is replenish by the atmosphere this process is known as:
A)
Oxidation
B)
Deoxidation
C)
Self purification
D)
Sedimentation
The process described is known as 'Self Purification' of a stream. When sewage is discharged into a water body, aerobic bacteria decompose the organic matter, which consumes the dissolved oxygen (DO) in the water (a process called deoxygenation). Simultaneously, oxygen from the atmosphere is absorbed into the water through the surface (a process called reaeration). The balance between the rate of deoxygenation and the rate of reaeration allows the stream to naturally recover its quality over time and distance. This overall cycle is termed self-purification.
Why other options are incorrect:
- Oxidation (a): This is a chemical reaction part of the process, but not the name of the overall natural cycle of recovery.
- Deoxidation (b): This refers only to the removal or consumption of oxygen, not the replenishment part.
- Sedimentation (d): This is a physical process where suspended solids settle at the bottom due to gravity; it does not involve the oxygen exchange cycle described.
The weight of footings is assumed as ___________ of the weight transferred to the column.
A)
5 %
B)
10 %
C)
15 %
D)
20 %
In foundation engineering, when calculating the total load acting on the soil (the bearing pressure), the total load consists of the dead load and live load transferred from the column plus the self-weight of the footing and the weight of the soil overburden resting on the footing. Since the exact dimensions and volume of the footing are often not finalized during the preliminary design phase, a standard empirical value is used to account for the self-weight of the concrete footing and the soil above it. It is a widely accepted engineering convention to assume the weight of the footing and the soil surcharge to be approximately 10% of the axial load transferred from the column. This provides a reasonable safety margin for the bearing capacity calculations without requiring iterative calculations for every minor change in footing size.
A pipe installed for ventilation purpose is called:
A)
Waste pipe
B)
Soil pipe
C)
Vent pipe
D)
Anti-siphonage pipe
In plumbing and environmental engineering, different pipes serve specific functions within a drainage system:
1. **Vent Pipe (Correct):** A vent pipe is specifically installed to provide ventilation to the drainage system. Its primary purpose is to allow sewer gases to escape to the atmosphere and to admit fresh air into the system, which prevents the buildup of pressure and ensures the smooth flow of waste.
2. **Waste Pipe:** This pipe is used to carry liquid waste (greywater) from fixtures like washbasins, sinks, and baths, but it does not carry human excreta.
3. **Soil Pipe:** This pipe is designed to carry human excreta (blackwater) from water closets (WCs) and urinals to the main sewer line.
4. **Anti-siphonage Pipe:** While this is a type of vent pipe, it is a specialized pipe used specifically to prevent the 'siphoning' (suction) of water seals in traps, ensuring that sewer gases do not enter the building. However, the general term for a pipe installed for ventilation purpose is the 'Vent pipe'.
One cubic metre of water weighs:
A)
100 litres
B)
250 litres
C)
500 litres
D)
1000 litres
Step-by-step reasoning:
1. Understanding the units: The question asks for the 'weight' (though it uses volume units in the options) of one cubic metre (1 m³) of water.
2. Volume Conversion: By definition, 1 cubic metre is equal to 1,000 litres (1 m³ = 1000 L).
3. Mass/Weight Relationship: For pure water at standard temperature and pressure, the density is approximately 1000 kg/m³. Therefore, 1 m³ of water has a mass of 1000 kg.
4. Litre-to-Mass Correlation: Since 1 litre of water weighs approximately 1 kilogram, 1000 litres of water weigh 1000 kilograms.
5. Analysis of Options: The options provided are in 'litres', which is a unit of volume. In the context of basic fluid mechanics questions of this type, the question is testing the fundamental conversion between cubic metres and litres.
- Option a (100 L), b (250 L), and c (500 L) are mathematically incorrect conversions of 1 m³.
- Option d (1000 L) correctly identifies the volume equivalent of 1 m³ of water.
In preliminary treatment of sewage , the operation which takes place is:
A)
Removal of fine suspended particles
B)
Removal of fine dissolved organic material
C)
Removal of lighter floating material
D)
Removal of harmful bacteria and other organism
Sewage treatment is typically divided into preliminary, primary, secondary, and tertiary stages.
1. **Preliminary Treatment**: This stage is designed to protect the plant equipment (pumps and pipes) and remove large, coarse materials. It involves operations such as screening (to remove large floating debris like plastics, rags, and sticks) and grit removal (to remove heavy inorganic solids like sand and gravel). Therefore, the removal of lighter floating material (via screening) and heavy grit is the primary goal of this stage.
2. **Why other options are incorrect**:
- **Option (a)**: Removal of fine suspended particles occurs during **Primary Treatment** (via sedimentation tanks/clarifiers).
- **Option (b)**: Removal of dissolved organic material occurs during **Secondary Treatment** (via biological processes like activated sludge or trickling filters).
- **Option (d)**: Removal of harmful bacteria and other organisms occurs during **Tertiary Treatment** or Disinfection (using chlorine, UV, or ozone).
For large sewers , the maximum distance between manholes should be:
A)
75 m
B)
100 m
C)
200 m
D)
300 m
In environmental engineering and sewage system design, manholes are provided at regular intervals to allow for inspection, cleaning, and removal of obstructions. The spacing of manholes depends primarily on the diameter of the sewer pipe. For small sewers (typically diameters up to 600mm or 900mm), the spacing is shorter (often 30m to 100m). However, for large sewers (trunk sewers or intercepting sewers), the distance can be increased because they are less prone to frequent localized blockages and are often constructed with materials and gradients that facilitate easier flow. According to standard engineering practice and various municipal codes (such as CPHEEO manuals), the maximum distance between manholes for large sewers is generally taken as 300 meters. Options a, b, and c are typical spacings for smaller diameter lateral or branch sewers.
The quantity of liquid waste which flows in sewers during rainy season is called:
A)
Storm sewage
B)
Dry weather flow
C)
Sanitary sewage
D)
Domestic waste
In environmental engineering and wastewater management, sewage is categorized based on its source and the weather conditions.
1. **Storm Sewage (Correct):** This refers to the wastewater that enters the sewer system specifically due to precipitation (rain or melting snow). In combined sewer systems, the total flow during the rainy season is the sum of dry weather flow and storm sewage.
2. **Dry Weather Flow (DWF):** This is the average flow of sewage in a sewer during periods of no rainfall. It consists primarily of domestic sewage and industrial waste.
3. **Sanitary Sewage:** This is a general term for wastewater from toilets, sinks, and showers (domestic waste), regardless of the season. While it flows during the rainy season, it is not the specific term for the *additional* liquid waste caused by rain.
4. **Domestic Waste:** This refers to the waste generated from residential activities, which is a component of sanitary sewage, not the rain-induced flow.
Therefore, the liquid waste that flows specifically due to the rainy season is termed 'Storm sewage'.
Venturimeter is used to:
A)
Measure the velocity of a flowing liquid
B)
Measure the pressure of a flowing liquid
C)
Measure the discharge of liquid flowing in a pipe
D)
Measure the pressure of difference of liquid flowing between two points in a pipe line
A Venturimeter is a device used for measuring the discharge (volumetric flow rate) of a fluid flowing through a pipeline. It works on the principle of Bernoulli's Equation. The device consists of a converging section, a throat, and a diverging section. As the fluid passes through the throat (the narrowest part), its velocity increases and its pressure decreases. By measuring the pressure difference between the inlet and the throat using a manometer, the flow rate (discharge) can be calculated using the formula: Q = Cd * A1 * sqrt((2gh) / (1 - (A1/A2)^2)), where Cd is the coefficient of discharge, A1 is the inlet area, and h is the differential pressure head.
Why other options are incorrect:
- Option (a): While velocity changes within the meter, the primary purpose of the device is to find the total discharge (Q), not just the velocity at a point.
- Option (b): A pressure gauge or manometer is used to measure pressure; the Venturimeter uses pressure differences as a means to find flow rate.
- Option (d): While the Venturimeter creates a pressure difference, it is not used to 'measure the pressure difference' as its end goal, but rather uses that difference to calculate the discharge.
For the sewers of diameter less than 600mm, the type of joint preferred is:
A)
Spigot and socket joint
B)
Collar joint
C)
Bandage joint
D)
Mechanical joint
In environmental engineering and sewerage design, the choice of joint depends on the pipe diameter and the required flexibility/watertightness.
1. **Spigot and Socket Joint**: This is the most common and preferred joint for smaller diameter sewers (typically less than 600mm). It consists of one end of the pipe being expanded (socket) and the other end being slightly tapered (spigot). The spigot is inserted into the socket and sealed with a gasket or cement mortar, providing a secure, watertight seal suitable for smaller pipes.
2. **Collar Joint**: These are generally used for larger pipes or for connecting two pipes of the same diameter where a socket is not provided. They are less common for small-diameter residential or branch sewers compared to spigot and socket joints.
3. **Bandage Joint**: These are typically used for repairs or temporary fixes rather than as a standard installation joint for new sewer lines.
4. **Mechanical Joint**: While highly secure, mechanical joints are more expensive and complex to install. They are typically reserved for larger diameter pipes, high-pressure lines, or areas subject to significant ground movement, rather than standard small-diameter sewers.
The activated sludge process of sewage treatment:
A)
Requires large area for construction of whole unit
B)
Requires higher water head for operation than trickling filters
C)
Has high efficiency
D)
Has low output
The Activated Sludge Process (ASP) is a biological wastewater treatment method that uses a mass of microorganisms (activated sludge) to decompose organic matter.
1. **Why Option (c) is correct:** ASP is known for its high efficiency in removing Biochemical Oxygen Demand (BOD) and suspended solids, often achieving removal rates of 90-95% or higher, which is generally superior to traditional trickling filters.
2. **Why Option (a) is incorrect:** Compared to waste stabilization ponds or extensive trickling filter beds, ASP is more compact and requires a smaller land area for the same volume of sewage treated.
3. **Why Option (b) is incorrect:** Trickling filters often rely on gravity flow through a medium, whereas ASP requires mechanical aeration (blowers/pumps). While ASP has higher energy requirements, it does not necessarily require a 'higher water head' for operation in the way a gravity-fed filter system does.
4. **Why Option (d) is incorrect:** ASP is designed for high-capacity treatment and can handle large volumes of sewage efficiently, meaning it has a high output capacity rather than a low one.
The minimum depth of septic tank is considered to be:
A)
0.5 m
B)
1.0 m
C)
1.2 m
D)
1.5 m
In Environmental Engineering, a septic tank is designed to provide sufficient detention time for the settling of solids and anaerobic digestion of organic matter. According to standard engineering guidelines (such as IS 2470 in the Indian context), the liquid depth of a septic tank is typically maintained between 1.0 m and 1.8 m. The minimum liquid depth is specified as 1.0 m to ensure that there is enough space for the accumulation of sludge at the bottom and the formation of a scum layer at the top without compromising the hydraulic retention time or causing premature solids carry-over into the soak pit or drainage field. Options a (0.5 m) is too shallow to prevent turbulence and allow settling; options c (1.2 m) and d (1.5 m) are common design depths but are not the absolute minimum threshold.