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Q.1 भ्रष्टाचार निवारण ऐन, २०५९ का विशेषताहरु उल्लेख गर्नुहोस् । (5)

भ्रष्टचार निवारण ऐन २०५९ सर्वसाधरणको सुख,शान्ती र आर्थिक हितको निमित्त समाजमा आर्थिक अनुसाशन नैतिकता र सदाचार कायम राख्ने उदेश्यले मिति २०५९/०३/०५ मा प्रमाणित भई लागु भएको भ्रष्टचार निवारण ऐन २०५९ का मुख्य विशेषताहरु देहाय वमोजिम छन् :-

• १) ५ परिच्छेद ६५ दफाहरुमा सुचिवद्द गरिएको
• २) भ्रष्टचार सम्बन्धि कसुर र सजायको व्यवस्था गरेको
• ३) भ्रष्टचारको अनुसन्धान र तहकिकात गर्ने कार्यविधि तय गरिएको
• ४) झुटा उजुर दिने र अनुसन्धानमा वाधा विरोध गर्नेलाई सजायको व्यवस्था गरेको
• ५) अनुसन्धानमा सहयोग गर्नेलाई पुरस्कारको व्यवस्था गरेको
• ६) सार्वजनिक पद धारणा गरेको व्यक्तिले अनिवार्य रुपमा समपत्ति विवरण पेस गर्नुपर्ने प्रावधान रहेको
• ७) उच्च पदस्थ कर्मचारिलाई थप सजायको व्यवस्था गरिएको
• ८) राष्ट्रिय सतर्कता केन्द्रको व्यवस्था गरि काम कर्तव्य र अधिकार स्पस्ट तोकेको आदि ।

Q.2 What are the major reasons for using admixtures? Write its classification by function. (2+3)

Admixtures are chemical or mineral additives that are sometimes included in the concrete mix to enhance specific properties. Major reasons for using admixture are

Q.3 What do you mean by paint and varnish? Write down any six tests of bitumen. (1+1+3)

Paints are used to protect metals, timber or plastered surfaces from the corrosive effects of weather, heat, moisture, or gasses etc. and to improve their appearance. Paint is a substance used as a final finish to all surfaces and as a coating to protect or decorate the surfaces

Varnish is a type of paint in which resins are used instead of base. It is prepared by mixing suitable resins in a particular solvent. It is usually used for painting wooden furniture and other woodwork so as to give them a brightened ornamental look and to protect them from weather.

1. PENETRATION TEST: Penetration test is probably the most popular traditional test on binders, since used to classify bitumen by measuring the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds Penetration tests are used to determine how hard or soft bitumen is. A penetrometer is used to measure a penetration test on bitumen.

2. DUCTILITY TEST: The ability of bitumen to undergo significant deformation or elongation is known as ductility. It can also be defined as the distance in cm to which a standard sample or briquette of the material can be stretched without breaking.

3. SOFTENING POINT TEST: Softening point denotes the temperature at which the bitumen attains a particular degree of softening under the specified condition of the test. The test is conducted by using ring and ball apparatus. The term “softening point” refers to the temperature at which the bitumen softens to a specific degree under the given test conditions.

4. VISCOSITY TEST: The liquid quality of bituminous material is known as viscosity, and it serves as a gauge of flow resistance. This characteristic does have a substantial effect on the strength of the resulting pavement mixes at the application temperature. Lower stability values have been noted when mixing or compacting materials with low or high viscosities.

5. FLASH POINT TEST: The flash point is the lowest temperature at which a flame causes the vapors from a material to catch fire, as a flash, under specific test conditions. These volatiles ignite, which is extremely dangerous, so it is crucial to specify this temperature for each bitumen grade.

6. FLOAT TEST: Normally the consistency of bituminous material can be measured either by penetration test or viscosity test. But for certain range of consistencies, these tests are not applicable, and Float test is used. The apparatus consists of an aluminum float and a brass collar filled with bitumen to be tested.

7. LOSS ON HEATING TEST: When the bitumen is heated it loses the volatility and gets hardened. Bitumen used in pavement mixes should not indicate more than 1% loss in weight, but for bitumen having penetration values 150-200 up to 2% loss in weight is allowed.

Q.4 Calculate the shear force FA, FB, FC, FD in the given diagram A. (5)

Q.5 Define dynamic viscosity of a liquid. Explain four types of hydraulic coefficients. (1+4)

Dynamic viscosity is a measure of a fluid’s resistance to flow when subjected to an external force. It quantifies the internal friction between layers of the fluid as they move relative to each other. Mathematically, it is expressed as:

$$\eta = \frac{\tau}{\frac{du}{dy}}$$

Where,

$$\tau \text{: Shear stress}$$
Velocity gradient: $$\frac{du}{dy} \text{ (rate of change of velocity with distance)}$$

Its SI unit is N-s/m² or Pa-s.
Its C.G.S unit is Poise.
1 Poise = 0.1 Pa-s = 0.1 Ns/m²

Four Types of Hydraulic Coefficients

Hydraulic coefficients are used to characterize the performance of orifices, weirs, and nozzles in fluid mechanics. They include:

1.COEFFICIENT OF DISCHARGE(C_d​): It is the ratio of the actual discharge to the theoretical discharge through an orifice or a hydraulic structure. It accounts for all energy losses in the system, including friction and contraction.

$$C_d = \frac{Q_{\text{actual}}}{Q_{\text{theoretical}}}$$

2. COEFFICIENT OF VELOCITY (C_v): It is the ratio of the actual velocity of the fluid jet at the vena contracta (narrowest section) to the theoretical velocity of the fluid. It measures how close the fluid’s velocity approaches the theoretical ideal velocity.

$$C_d = \frac{Q_{\text{actual}}}{Q_{\text{theoretical}}}$$

3. COEFFICIENT OF CONTRACTION (Cc​): It is the ratio of the area of the jet at the vena contracta to the area of the orifice. It accounts for the reduction in jet area due to the convergence of streamlines.

$$C_c = \frac{A_{\text{orifice}}}{A_{\text{jet}}}$$

4. COEFFICIENT OF RESISTANCE (C_r​): It represents the loss of head (energy) due to resistance in the system. It is defined as head lost by total head. This coefficient evaluates energy dissipation in the fluid flow.

$$C_r = \frac{\text{Head lost}}{\text{Total head}}$$

Q.6 Write any five assumptions and two limitations of Terzaghi’s general bearing capacity theory. (4+1)

Assumptions of Terzaghi’s bearing capacity Theory

1. The soil is homogeneous and isotropic and its shear strength is represented by Coulomb’s equation.
2. The strip footing has a rough base, and the problem is essentially two dimensional.
3. The elastic zone has straight boundaries inclined at ψ = ϕ to the horizontal, and the plastic zones fully develop.,
4. Pp consists of three components, which can be calculated separately and added, although the critical surface for these components is not identical.
5. Failure zones do not extend above the horizontal plane through the base of the footing, i.e. the shear resistance of soil above the base is neglected and the effect of soil around the footing is considered equivalent to a surcharge σ = γ × D [γ = unit weight of soil, D = Depth of foundation]

Limitations of Terzaghi’s bearing capacity Theory

1. Terzaghi’s analysis assumes the plastic zones develop fully before failure occurs. This is true only in the case of dense cohesionless soils and stiff cohesive soils.
2. The value of Φ is assumed to remain constant. But Φ can change as soil gets compressed.
3. The failure zones are assumed not to extend above the base level of footing. Thus the shearing resistance of soil surrounding it above its base level is neglected. The error due to this assumption increases as the depth of footing is increased.
4. The load is assumed to be vertical and acting concentrically with uniform pressure distribution at the base.

Q.7 Introduce and compare working stress and limit state philosophy for design of RCC structures. (5)

Introduction

The design of reinforced cement concrete (RCC) structures involves ensuring both safety and serviceability under applied loads. Two major design philosophies are widely recognized: Working Stress Method (WSM) and Limit State Method (LSM). While WSM is an older, traditional approach, LSM represents a more advanced and comprehensive design philosophy, addressing the limitations of WSM.

Working Stress Method (WSM)

WSM is based on the assumption that materials behave elastically under working loads. It ensures that the stresses in structural members remain within permissible limits, calculated by applying a global factor of safety to the material’s strength. This approach relies on the linear stress-strain relationship of materials and focuses on serviceability, ensuring that deflections, vibrations, and cracking are controlled under normal operating conditions. However, WSM often leads to conservative and overdesigned structures, as it does not account for material behavior under ultimate loads or failure scenarios.

Limit State Method (LSM)

LSM is a modern design philosophy that considers both the ultimate strength and serviceability of structures. It uses partial safety factors to account for uncertainties in material strength, loads, and construction practices. LSM recognizes the nonlinear behavior of materials, providing a realistic and efficient design. It ensures structural safety under extreme loading conditions (ultimate limit state) and adequate performance under regular service conditions (serviceability limit state). This method is less conservative than WSM, optimizing material use while maintaining safety and reliability.

Comparison

The primary difference between WSM and LSM lies in their treatment of safety and material behavior. WSM focuses on elastic behavior under working loads, leading to conservative designs, while LSM is based on a probabilistic approach, considering ultimate and serviceability conditions separately. LSM is more efficient, economical, and versatile, making it the preferred choice for modern RCC structures.

Q.8 Define contouring. Explain any nine characteristics of contour maps. (1+9)

Contouring in surveying is the process of identifying and mapping out contour lines on a land surface to represent areas of equal elevation. Contours are essential in creating topographic maps, which help visualize the terrain’s shape, such as hills, valleys, and slopes.

Characteristics of Contour Maps

1.  Contour lines must close, not necessarily in the limits of the plan.
2. Widely spaced contour indicates flat surface.
3. Closely spaced contour indicates steep ground.
4. Equally spaced contour indicates uniform slope.
5. Irregular contours indicate uneven surface.
6. Approximately concentric closed contours with decreasing values towards centre indicate a pond.
7. Approximately concentric closed contours with increasing values towards centre indicate hills.
8. Contour lines with U-shape with convexity towards lower ground indicate ridge.
9. Contour lines with V-shaped with convexity towards higher ground indicate valley.
10. Contour lines generally do not meet or intersect each other.
11. If contour lines are meeting in some portion, it shows existence of a vertical cliff.
12. If contour lines cross each other, it shows existence of overhanging cliffs or a cave.

Q.9 What do you mean by shoring and is dewatering associated with it? (5)

The preparation of temporary supports used to stabilize unsafe buildings is called shoring. Old buildings with weakened structural members can fall at any time due to their own instability or external dynamic loads, creating fear among local residents. To ensure safety until these buildings are demolished or dismantled, or rebuilt temporary supports must be provided. These supports known as shores. Generally, there are different types of shoring.

Types of Shoring

1. VERTICAL OR DEAD SHORING: These are the shores provided to support walls, roofs, floors etc. when lower part of wall has been removed. This consists of arrangement of beams and posts, which supports the weight of the structure. These are also called dead shores.

2. HORIZONTAL OR FLYING SHORING: The temporary supports provided for supporting the parallel walls of the adjacent building are called horizontal shores. These are also called flying shores. The flat plates are used to increase the area of contact on the adjacent walls.

3.INCLINED OR RACKING SHORING : Racking shores consists of one or more members sloping between the face of structure to be supported and the ground. If rackers are inclined at 60 to 70 degrees, the support will be most effective. A wall plate is used to increase the area of support. These are also called inclined shores.

Yes, dewatering is often associated with shoring. Dewatering refers to the process of removing water from an excavation site to ensure a dry and stable working environment. This is especially important in areas with a high water table or where groundwater or rainwater might collect in the excavation.

Dewatering is important when working with shoring because:

1. Water weakens the soil, making it less stable and increasing the risk of trench or wall collapse.
2. Water pressure can build up behind shoring systems, which could compromise their effectiveness and cause failure.
3. Dewatering reduces the risk of erosion and ensures the soil around the shoring remains firm and supportive.

Q.10 Explain concrete mix, laying, pouring and compaction. (2+1+1+1)

A. CONCRETE MIX

Concrete is a mixture of cement, water, fine aggregates (sand), and coarse aggregates (gravel or crushed stone). The proportions of these materials determine the concrete’s strength, durability, and workability. The most commonly used mix ratios for concrete are represented in terms of cement: sand: aggregates, for example, a 1:1.5:3 mix (1 part cement, 1.5 parts sand, 3 parts aggregates).

• Water-cement ratio: This is critical in determining the concrete’s workability and strength. Too much water weakens the concrete, while too little makes it difficult to work with and compact.
• Admixtures: Additional substances such as plasticizers, accelerators, or retarders can be added to the mix to alter its properties, such as improving workability, reducing curing time, or enhancing strength.

B. LAYING CONCRETE

Laying concrete refers to the process of placing the freshly mixed concrete into its final position within a formwork or designated area where it will set and harden. Proper laying techniques are essential to ensure uniformity and prevent segregation of the mix. Steps in laying concrete:

C. POURING CONCRETE

Pouring concrete refers to the actual process of transferring the concrete mix from the container (e.g., truck or mixer) into the formwork or designated area. Proper techniques are important to ensure the strength and durability of the structure. Important considerations during pouring:

• Avoid segregation: Concrete should be poured close to its final location to prevent segregation. Dropping the concrete from excessive heights can cause the heavier aggregates to separate from the cement paste.
• Even distribution: Distribute the concrete evenly and systematically to minimize the need for shifting large amounts manually, which could lead to weak spots.
• Layering: In large pours, concrete is often placed in layers, ensuring each layer is compacted before the next is added to avoid creating air pockets or cold joints.
• Proper placement: Pouring should be done carefully, particularly in forms with rebar, to ensure the concrete fills all voids and fully encapsulates the reinforcement without leaving gaps.

D. Compaction of Concrete

Compaction is the process of removing trapped air from the freshly placed concrete, which helps achieve maximum density and strength. If air bubbles remain in the concrete, they can create weak spots, reducing the overall strength and durability of the structure. Methods of compaction:

• Manual compaction: For small areas or thin slabs, manual tools such as rods, rammers, or tampers are used to compact the concrete.
• Vibrating compaction: For larger projects, mechanical vibrators are used to compact the concrete more effectively. These vibrators help the concrete settle and fill voids by removing entrapped air.
• Surface vibrators: Also known as screeds, these are used on the surface of the concrete to compact slabs and floors while leveling the top layer.

Importance of Compaction

• Strength: Properly compacted concrete is denser, leading to higher strength and durability.
• Durability: Compaction reduces the number of voids, which can weaken the structure or allow water infiltration, causing long-term damage.
• Surface finish: Well-compacted concrete has a smoother and more uniform finish, which is important for aesthetic and functional purposes.

Q.11 Why are rate analysis and specification crucial in estimation? (2.5+2.5)

Rate analysis and specification are critical components in the estimation process for any construction project. They play a vital role in determining the overall cost, quality, and scope of the work involved. Here’s why they are crucial:

A. Rate Analysis:

Rate analysis is the process of calculating the cost per unit of a particular item of work (e.g., per cubic meter of concrete, per square meter of plaster). It involves breaking down the costs of materials, labor, equipment, and other factors required to complete the work.

Importance of Rate Analysis in Estimation:

•  Accurate Cost Prediction: It helps in determining the accurate cost of individual construction activities by considering current market rates for materials and labor, transportation, wastage, and overheads.
•  Budgeting: With a detailed rate analysis, contractors can create a realistic budget for the project and avoid cost overruns.
•  Profit Margins: By understanding the actual cost of each work item, contractors can set appropriate profit margins.
•  Comparison with Market Rates: It allows the estimator to compare project rates with local market conditions, ensuring that the rates are competitive and up to date.
•  Tendering and Bidding: In competitive bidding, accurate rate analysis helps contractors prepare comprehensive bids, ensuring profitability while remaining competitive.

B. Specification:

Specifications describe the standards and quality of materials, workmanship, and construction methods to be used in the project. They provide detailed technical information about how work should be executed.

Importance of Specification in Estimation:

• Quality Control: Specifications ensure that the correct quality of materials and construction methods are used. This helps avoid low quality work that could lead to structural failures or repairs in the future.
• Scope Definition: Specifications clearly define the scope of work, reducing the risk of misunderstandings or discrepancies between the client and the contractor regarding what is included in the estimate.
• Cost Estimation Accuracy: The quality and type of materials specified will directly affect the costs. For example, using high grade cement or steel increases the cost, while basic materials might reduce it. Without clear specifications, an estimate may be inaccurate.
• Contractual Clarity: Specifications serve as part of the legal contract between the contractor and client, setting expectations for performance and quality.
• Consistency across Projects: They ensure that similar types of projects maintain uniform quality and standards by adhering to predefined requirements.

 How They Work Together:

• Rate analysis uses the specifications to determine the required quality of materials and the construction process, ensuring that costs are based on the correct standards.
• Specifications provide the detailed description of work that must be followed, while rate analysis calculates the financial impact of adhering to those specifications.
• Both ensure that the estimate reflects the actual cost and quality requirements of the project.

Q.12 State various types of contracts and explain its disadvantages. (2+3)

The agreement between two or more parties to do or to not do any work within certain period of time and condition enforced by law is called contract. All contracts are agreement but all agreement are not contract.  

1. LUMP SUM CONTRACT (FIXED PRICE CONTRACT): In a lump sum contract, the contractor agrees to complete the entire project for a fixed price that covers all labor, materials, and services.

 Advantages:

•  Cost Certainty: The client knows the total cost upfront, making it easier to budget.
•  Simplicity: Clear agreement on price and scope reduces the need for detailed tracking of individual expenses.
•  Incentive for Efficiency: The contractor is motivated to complete the project efficiently since cost overruns are their responsibility.

 Disadvantages:

•  Risk for Contractor: The contractor bears all the risk if there are unexpected costs, such as price fluctuations for materials or labor.
•  Limited Flexibility: Any changes in the project scope usually lead to contract amendments, potentially delaying the project.
•  Quality Concerns: Contractors may cut costs or quality to protect their profit margins.

 2. UNIT RATE CONTRACT (MEASUREMENT CONTRACT): In a unit rate contract, payment is made based on the actual quantities of work done at predetermined rates for each unit of work.

 Advantages:

•  Flexibility: The final cost can adjust according to the actual quantities of work done.
•  Fair Payment: Contractors are paid for the exact amount of work completed, which is beneficial if the project scope is uncertain.
•  Ease of Variations: Changes in work scope are easier to manage and reflect in payments.

 Disadvantages:

•  Cost Uncertainty: The final cost remains uncertain until the project is complete, which can complicate budgeting.
•  Potential for Disputes: Disagreements may arise over the measurement of completed work.
•  Time Consuming: Ongoing measurement and verification of work take time, potentially delaying the project.

 3. COST PLUS CONTRACT: In a cost-plus contract, the client agrees to pay the contractor for the actual costs incurred, plus an additional fee for overhead and profit. It is often used in projects where the scope is not fully defined.

 Advantages:

•  Transparency: The client has visibility into the actual costs of materials and labor.
•  Scope Flexibility: Works well when the exact scope of the project is difficult to define upfront.
•  No Price Risk to Contractor: The contractor is assured that all costs will be covered.

 Disadvantages:

•  Lack of Cost Control: Since the contractor is reimbursed for costs, there is little incentive to keep expenses down.
•  Budget Uncertainty: The final project cost can exceed initial estimates.
•  Close Monitoring Required: The client needs to supervise expenditures closely to ensure costs are reasonable.

 4. TIME AND MATERIAL CONTRACT: A time and material contract pays the contractor based on the time spent and materials used, with rates for both agreed upon upfront.

 Advantages:

•  Flexibility: Ideal for projects where the scope is unclear, as it allows adjustments as the project progresses.
•  Fair Compensation: The contractor is paid for actual time and materials, ensuring they are compensated for the work done.

 Disadvantages:

•  Cost Uncertainty: There is no fixed price, making it difficult to estimate the final project cost.
•  Risk of Inefficiency: Contractors may not be incentivized to complete the work quickly or efficiently.
•  Client Supervision: The client must monitor time and material usage to ensure the project remains within a reasonable cost.

 5. DESIGNBUILD CONTRACT: In a DesignBuild contract, a single entity is responsible for both the design and construction of the project.

 Advantages:

•  Single Point of Responsibility: The client deals with one contractor for both design and construction, simplifying communication and coordination.
•  Faster Project Delivery: Design and construction can occur simultaneously, reducing the project timeline.
•  Cost Savings: Contractors can optimize design to reduce construction costs.

 Disadvantages:

•  Less Control for Client: The client has less control over the design and construction processes compared to traditional contracts.
•  Quality Concerns: The contractor may prioritize cost savings over design quality, leading to suboptimal results.
•  Potential for Conflicts of Interest: The design and construction arms may prioritize their interests over the project’s needs.

 6. TURNKEY CONTRACT: In a turnkey contract, the contractor is responsible for the entire project, from design to construction, and delivers it fully completed and ready for use.

 Advantages:

•  Minimal Client Involvement: The client is not deeply involved in the day-to-day management of the project, which can be convenient.
•  Time Savings: Since the contractor handles everything, the project can often be completed more quickly.
•  Cost Certainty: The contractor takes on most of the risk, ensuring a more predictable final cost.

 Disadvantages:

•  Lack of Control: The client has little say in the design and construction details once the contract is signed.
•  Higher Cost: Since the contractor assumes most of the risk, the contract price is often higher to cover contingencies.
•  Risk of Lower Quality: The contractor may compromise on quality to meet deadlines or reduce costs.

 7. ITEM RATE CONTRACT: In an item rate contract, the contractor is paid based on a predetermined rate for each item of work completed.

 Advantages:

•  Clear Pricing: Item rates are agreed upon upfront, providing clarity for both parties.
•  Fair Compensation: The contractor is paid according to the exact work completed.
•  Easy Variations: Changes in the scope of work can be managed by adjusting the quantities for each item.

 Disadvantages:

•  Time Consuming Measurements: Like unit rate contracts, frequent measurement of work done is required.
•  Cost Uncertainty: Since the total amount of work may vary, the final cost remains uncertain.
•  Potential for Disputes: Differences in opinion regarding the actual quantities of work can lead to conflicts.

Q.13 Define runway, taxiway, and apron of an airport. (5)

Q.14 How would you use shallow and deep tube wells for water supply in Terai? Under what conditions is each used and why? (5+5)

Shallow Tube Wells

Definition and Use in Water Supply: Shallow tube wells are wells that tap into groundwater sources that are relatively close to the surface, usually within a depth range of 10 to 50 meters. In the Terai region, these wells are commonly used for accessing shallow aquifers that provide an adequate water supply for domestic, agricultural, and small-scale industrial purposes. These wells are typically drilled into areas with abundant and accessible groundwater at shallow depths.

Conditions for Use: Shallow tube wells are most suitable for areas where the water table is high, making the groundwater easily accessible. In the Terai, which often has a high water table due to its alluvial soil and proximity to rivers, shallow tube wells are effective in providing water for irrigation, domestic use, and small-scale industrial operations. They are also ideal for regions with moderate water demand where the shallow aquifers can meet the requirements.

Advantages:

• Lower Construction Costs: Shallow tube wells are cheaper to construct than deep tube wells because they require less drilling and simpler pump systems.
• Energy Efficiency: Since the water table is close to the surface, less energy is required to pump the water, making these wells more energy-efficient and cost-effective to operate.
• Quick Installation: These wells can be installed faster compared to deep wells, making them more accessible for areas with urgent water needs.

Limitations:

• Seasonal Variations in Water Table: Shallow tube wells are more vulnerable to seasonal fluctuations in the water table, especially during dry seasons when water levels may drop significantly.
• Risk of Depletion: Over-extraction of water from shallow wells can lead to the depletion of the aquifer, causing the well to run dry or yield lower amounts of water.

Deep Tube Wells

Definition and Use in Water Supply: Deep tube wells are wells that tap into deeper groundwater sources, typically drilled to depths greater than 50 meters. These wells are used to access confined aquifers or deeper layers of groundwater that are more reliable and less affected by seasonal fluctuations. In the Terai, deep tube wells are often employed in areas where the water table is deep, or where shallow aquifers have been over-exploited or have poor water quality.

Conditions for Use: Deep tube wells are most suitable for regions with a low water table or areas where shallow aquifers have been depleted or are unable to meet water demand. These wells are often used in areas with high water demands such as large-scale agricultural irrigation, urban water supply, or industrial use. In the Terai, they are particularly useful where the groundwater at shallow depths is either insufficient or has become contaminated.

Advantages:

• Access to Reliable Aquifers: Deep tube wells provide access to deeper, more stable aquifers that are less likely to be impacted by seasonal water table fluctuations.
• Higher Yield: These wells are capable of providing larger volumes of water, making them suitable for regions with high water demand, such as agricultural fields or urban areas.
• Suitable for High Water Demand: They are often the only viable solution in areas where shallow wells can no longer meet the growing water needs.

Limitations:

• Higher Construction Costs: Deep tube wells are more expensive to construct due to the increased drilling depth and more complex pumping systems required.
• Energy-Intensive: Pumping water from greater depths requires more energy, leading to higher operational costs.
• Risk of Over-Exploitation: Over-reliance on deep tube wells can lead to the depletion of deeper aquifers, causing long-term environmental issues such as land subsidence or intrusion of saline water into freshwater sources.

Comparison Between Shallow and Deep Tube Wells

Aspect	Shallow Tube Wells	Deep Tube Wells
Water Table Depth	Shallow (10-50 meters)	Deep (more than 50 meters)
Water Availability	Suitable for areas with high water table and moderate demand	Suitable for areas with low water table or insufficient shallow aquifers
Construction Cost	Low	High
Energy Requirement	Low	High
Seasonal Vulnerability	Prone to drying up during dry seasons	More reliable and stable throughout the year
Water Yield	Lower yield, suitable for small-scale use	Higher yield, suitable for large-scale irrigation and urban supply
Maintenance	Easier to maintain	More complex and costly to maintain

Q.15 What do you understand by crop-water requirement? Explain various factors affecting crop-water requirement. (5+5)

Crop-Water Requirement (CWR)

Definition: Crop-water requirement refers to the total amount of water needed by a crop for its growth during the growing season. This includes water for evapotranspiration (the combined process of evaporation from soil and transpiration by plants), as well as water required for other factors like soil moisture maintenance and leaching of salts. The crop-water requirement varies from crop to crop, depending on factors such as the crop type, local climate conditions, and the stage of growth.

Crop-water requirement is typically expressed in terms of millimeters (mm) or liters per hectare (L/ha) for a given period (e.g., per day, month, or growing season). It is crucial for efficient irrigation management, ensuring that crops receive the appropriate amount of water needed to maximize yield without over-irrigating or wasting water.

Factors Affecting Crop-Water Requirement (CWR)

1. Climate and Weather Conditions: Temperature, humidity, wind speed, and rainfall all affect CWR. Higher temperatures and wind speeds increase water loss through evaporation and transpiration, raising water needs. Low humidity also accelerates water loss, while adequate rainfall reduces the need for irrigation.
2. Soil Characteristics: Soil texture and structure determine how well the soil retains water. Sandy soils drain quickly, requiring more frequent irrigation, while clay soils retain moisture, reducing irrigation needs. Fertile soils with good organic content hold water better, reducing overall water requirements.
3. Crop Type and Growth Stage: Different crops have varying water needs. Crops like rice require more water than crops like maize. Additionally, water demand changes during different growth stages, with higher needs during flowering, fruiting, and maturity.
4. Irrigation Method: Water-efficient methods like drip or sprinkler irrigation reduce wastage and optimize water use. Traditional flood irrigation can result in significant water loss. Proper irrigation timing and frequency are crucial for meeting crop-water requirements efficiently.
5. Water Management Practices: Techniques like mulching and soil conservation help retain soil moisture and reduce evaporation, lowering the overall crop-water requirement. The availability of water resources and efficient water distribution also impact how much water crops need.
6. Evapotranspiration (ET): Evapotranspiration, the sum of evaporation and transpiration, is a key factor. Higher evapotranspiration due to hot, dry, or windy conditions increases crop-water demand, while cooler, more humid conditions reduce it. Calculating ET helps in managing irrigation needs.

Q.16 Draw a cross-section of a highway of Nepal and define all the elements. (10)

Cross sectional elements of highway pavement are