Other Industrial Engineering & Manufacturing Subjects
Tunnelling - Industrial Engineering & Manufacturing
Practice questions to test your knowledge and improve your understanding.
In the wooded bulk-head, used for mucking in steep grade tunnels,
Explanation:
In steep grade tunnels, a wooded bulk-head is specifically designed with two openings to facilitate the efficient removal of muck. These dual apertures allow mucking cars to pass through sequentially while simultaneously enabling the entry of fresh air and the exit of exhaust fumes from locomotives. This configuration ensures continuous operational flow and maintains necessary ventilation without requiring the complete removal of the bulk-head structure.
For full face method, the excavation to be done is generally divided into
Explanation:
In the full face method of tunneling, the entire tunnel face is excavated in a single continuous operation to maintain stability and efficiency. This process is systematically divided into four distinct sections, typically arranged in a cross pattern, to ensure balanced removal of earth. This four-section approach allows for uniform support installation and minimizes the risk of face collapse during the digging phase.
Railway tunnels, are generally
Explanation:
Railway tunnels are generally designed with a circular or horseshoe cross-section to maximize structural strength against the immense lateral pressure of surrounding earth and rock. This shape distributes stress evenly around the perimeter, preventing collapse and ensuring long-term stability without requiring excessive reinforcement. While rectangular shapes are sometimes used for specific urban contexts, the circular form remains the standard engineering solution for deep underground passages. Consequently, the term "polycentric," referring to a multi-centered or complex structural arrangement, accurately describes this robust, load-bearing geometry in this specific context.
Pick up the mechanical ventilation method used for tunnels from the following:
Explanation:
Mechanical ventilation in tunnels primarily relies on supplying fresh air directly to the tunnel face to ensure adequate oxygen levels for workers and dilute harmful gases. This method, known as face pressurization, involves installing ducts that blow fresh air into the excavation front while exhaust systems handle contaminated air separately. By prioritizing the delivery of clean air to the working face, this technique effectively maintains a safe atmosphere and prevents the accumulation of toxic fumes or dust. Consequently, it is the standard and most effective approach for ensuring safety during tunnel construction operations.
To attain the required shape of the tunnel section, we use:
Explanation:
Trimmers are specialized tools designed to precisely remove small amounts of material from the edges of a workpiece. In tunnel construction, they are essential for refining the rough outline into the exact required cross-sectional shape. By allowing for fine adjustments and smooth finishing, they ensure the tunnel dimensions match the engineering specifications perfectly. This process is critical for maintaining structural integrity and proper fit within the surrounding geological environment.
Which one of the following methods of tunnelling does not require the use of time bearing:
Explanation:
The mole method, also known as the mechanical tunneler, operates by advancing a shielded cutter head that simultaneously excavates soil and supports the tunnel face with a steel shield. This continuous process allows the machine to move forward without needing to pause for time-bearing operations, as the structural integrity is maintained by the shield itself rather than temporary supports. Consequently, this method eliminates the requirement for time-bearing, distinguishing it from techniques that rely on compressed air or specific shield configurations where such pauses might be necessary for safety or stability.
For B.G. single track, the section of the tunnel must have a width
Explanation:
For a Broad Gauge (B.G.) single track railway tunnel, the required width is determined by the standard gauge of 1.676 meters plus necessary clearances for the track structure and safety margins. Engineering standards specify that the tunnel section must be between 4.9 meters and 5.5 meters wide to safely accommodate the train, overhead equipment, and ventilation systems without compromising structural integrity or operational safety. This specific range ensures sufficient space for the rolling stock while maintaining the necessary clearance from the tunnel walls.
Which one of the following statements is not correct with regard to heading and hench-ing method of tunnelling.
Explanation:
In the heading and benching method, the tunnel face is advanced in two distinct stages: the upper heading and the lower bench. Holes are drilled in both sections, but the explosive charges are loaded separately rather than together. Crucially, the heading holes are fired first to create a free face, which significantly reduces the burden and stress on the rock mass before the bench holes are subsequently blasted. This sequential firing sequence ensures safer and more controlled excavation, making the statement about simultaneous firing incorrect.
The tunnels, the artificial underground passages are constructed for:
Explanation:
Artificial underground tunnels are versatile structures designed to accommodate various essential infrastructure needs within urban environments. They serve as critical conduits for sewerage systems to manage wastewater, act as protective channels for water supply pipelines to ensure safe delivery, and function as subterranean highways for efficient traffic flow. Since these passages are fundamentally constructed to support all these distinct yet vital functions simultaneously, the comprehensive option accurately reflects their broad utility in modern civil engineering and city planning.
The concentration of the dust particles of the size 0.5 to 5 microns adjacent to the working face should not be more than
Explanation:
This limit ensures that dust particles between 0.5 and 5 microns, which are most hazardous to lung health, remain at safe levels near the working face. Regulatory standards set this maximum concentration at 450 particles per cubic centimeter to protect miners from pneumoconiosis and other respiratory diseases. Maintaining this threshold is critical for occupational safety and compliance with mining health regulations. By adhering to this specific value, the environment remains breathable and reduces long-term health risks for workers. This standard balances operational needs with strict health protection requirements.
Which one of the following linings is suitable for shield driven tunnels particularly in the subaqueous regions:
Explanation:
Cast iron linings are specifically chosen for shield-driven tunnels in subaqueous regions due to their exceptional resistance to water pressure and corrosion. The material's inherent strength allows it to withstand the immense hydrostatic forces exerted by surrounding water without deforming. Additionally, cast iron provides a smooth, impermeable surface that prevents water infiltration and protects the underlying soil structure. This durability ensures long-term stability and safety in underwater environments where other materials might degrade or fail under constant moisture exposure. Consequently, it remains the standard choice for maintaining structural integrity in submerged tunnel sections.
Pick up the correct statement regarding drilling a tunnel from the following:
Explanation:
Pneumatically operated rock drills are the standard tool for creating boreholes in tunneling projects due to their efficiency and power. The borehole diameter is specifically designed to be slightly larger than the cartridge to ensure proper fit and safety during blasting operations. Furthermore, the spacing between drill holes is calculated based on the force area, typically requiring one drill for every 4 to 5 square meters to achieve uniform rock fragmentation. Since all these technical specifications accurately describe the drilling process, the comprehensive option is the correct choice.
Which one of the following statements is not correct in respect of setting of an inclined tunnel:
Explanation:
In inclined tunnel construction, reference points are strategically placed on the roof at regular intervals, typically every 300 meters, to ensure accurate alignment and elevation control throughout the drive. The specific level of the invert at the current heading is precisely marked using a tape measure or laser level, allowing surveyors to verify progress against the design profile. This method ensures that the tunnel follows the intended gradient without deviation. Therefore, the statement claiming that reference points are constructed on the roof is the correct description of the standard practice, making it the valid option in this context.
The length of the needle beam used in needle beam method of tunnelling is usually
Explanation:
In the needle beam tunnelling method, the needle beam is a temporary support system designed to maintain the stability of the tunnel face during excavation. The typical length of these beams ranges from 5 to 6 meters, which provides an optimal balance between structural integrity and practical installation constraints. This specific dimension allows the beams to effectively span the unsupported distance while accommodating the necessary spacing between injection points. Consequently, this length ensures that the ground remains stable without causing excessive deformation or requiring overly complex handling procedures.
In case of railways,
Explanation:
In railway engineering, tunnelling is the preferred method when a hill or mountain must be crossed because it provides a direct, level path that avoids the steep gradients and sharp curves required for surface routes. This approach ensures safer and more efficient train operations by maintaining consistent speeds and reducing wear on the track. Additionally, tunnels offer better protection against adverse weather conditions and landslides, ensuring year-round reliability. While open cuts or detours are alternatives, they often result in higher construction costs or significant land acquisition issues. Therefore, tunnelling is the optimal solution for overcoming significant elevation changes in mountainous terrain.
The following operations are required for tunnelling in rocky terrain:1. Removing the foul gases2. Marking the tunnel profile3. Setting up and drilling4. Checking misfire5. Mucking The correct sequence is:
Explanation:
In rocky terrain tunnelling, safety and precision dictate that marking the tunnel profile must come first to establish the excavation path. Once the profile is marked, setting up and drilling the blast holes follows immediately to prepare for blasting. After the blast, foul gases generated by the explosion must be removed to ensure a safe working environment before any further activity. Checking for misfires is then critical to identify any unexploded charges that need to be safely detonated. Finally, mucking, or removing the blasted rock debris, is the last step to clear the way for the next cycle of operations.
Which one of the following methods is generally adopted for tunnelling in firm ground
Explanation:
The full face method is the standard technique for tunnelling in firm ground because the stable soil or rock can support the entire tunnel cross-section being excavated simultaneously. This approach allows for faster progress and eliminates the need for temporary supports like timbering or steel sets, which are required in weaker ground conditions. By removing the whole face at once, the risk of collapse is minimized when the surrounding material possesses sufficient inherent strength to maintain stability. Consequently, this method is most efficient and widely adopted specifically for projects involving hard, competent geological formations.
For B.G. single track railway, the height of the tunnel above top of rails should be
Explanation:
In a Broad Gauge single track railway, a clear height of 6.7 m to 7.3 m above the rail level is mandated to ensure safe passage for standard locomotives and freight wagons. This specific range accommodates the maximum permissible load height while providing sufficient vertical clearance for overhead signaling equipment and catenary wires. Maintaining this dimension prevents collisions with the tunnel roof and allows for the necessary safety margins during train operations. The design balances structural integrity with operational efficiency to handle heavy traffic loads effectively. Adhering to these standards is critical for preventing derailments and ensuring passenger safety in confined tunnel environments.
The following operations are generally employed for tunnelling in hard rock.1. Removing ground water,2. Loading holes and firing the explosive3. Setting up and drilling4. Grouting and lining5. Removing muck6. Ventilation and removing explosion dustThe correct sequence is:
Explanation:
The tunnelling process in hard rock begins with setting up and drilling (3) to create blast holes, followed immediately by loading explosives and firing (2) to break the rock. After blasting, ventilation (6) is critical to clear toxic gases and dust before workers can enter. Once the area is safe, muck removal (5) clears the debris, and ground water must be removed (1) to ensure stability and visibility for the next cycle. Finally, grouting and lining (4) are performed to support the tunnel walls and prevent collapse, completing the sequence.
Pick up the correct statement from the following during tunnel excavation,
Explanation:
Maintaining safe atmospheric conditions is critical during tunnel excavation to protect worker health and prevent asphyxiation or poisoning. Hydrogen sulphide limits prevent respiratory irritation, carbon monoxide thresholds avoid hemoglobin binding that causes oxygen deprivation, and ensuring oxygen levels stay above 19.5% guarantees sufficient breathing capacity. Since all these specific concentration limits are standard safety requirements for underground environments, the statement encompassing all of them is the correct choice.