Overview:
This paper delves into the construction of the Bergen Hill Tunnels, a crucial part of the Pennsylvania Railroad’s New York Tunnel Extension. The project, completed in 1908, presented significant challenges due to the varied geology of the terrain, including a fault zone, sandstone, and diabase (trap rock). Excavation was achieved through the center top heading method, which required extensive timbering in the fault zone. The engineers utilized innovative drilling techniques with multiple drills per heading, employing a variety of methods for blasting and advancing the tunnel faces.
The paper highlights the unique ventilation problems encountered, particularly due to smoke from blasting and locomotives. The engineers employed a series of fans and blowers to improve air circulation and mitigate the smoke and fog issues. The construction of the concrete lining was another significant challenge, requiring careful planning to maintain track access and accommodate the conduit lines. A traveling gantry system was used to hoist concrete buckets, and innovative methods were employed for water-proofing and laying conduits. The paper provides detailed descriptions of the construction methods, plant equipment, organization, and cost estimations.
Key Findings:
- The Bergen Hill Tunnels presented unique geological challenges, necessitating adaptable construction methods.
- The use of multiple drills per heading significantly increased drilling speed and efficiency.
- Ventilation was crucial due to the smoke and fog generated by blasting and locomotives.
- The construction of the concrete lining required innovative techniques to maintain track access and accommodate conduits.
- The paper emphasizes the importance of meticulous planning and efficient organization in large-scale construction projects.
Learning:
- Geological Challenges in Tunneling: The paper reveals the diverse geological formations encountered during tunnel construction, highlighting the importance of understanding and adapting to variable conditions.
- Fault Zones: The fault zone presented challenges due to unstable ground, requiring extensive timbering.
- Sandstone and Diabase: The difference in hardness between sandstone and diabase led to variations in drilling speed and blasting methods.
- Innovations in Tunnel Excavation: This paper provides a detailed look at various drilling methods, highlighting how technological advancements and engineering ingenuity were utilized to overcome obstacles.
- Multiple-Drill Headings: The use of multiple drills per heading significantly increased excavation speed and efficiency.
- Drill Sharpener and Steel Usage: The introduction of the “Ajax” drill sharpener and the detailed analysis of steel consumption demonstrates the importance of efficient maintenance and material management.
- Ventilation in Tunnel Construction: The paper explores the challenges of ventilation in tunnel construction, emphasizing the need for effective systems to mitigate smoke, fumes, and fog.
- Fan and Blower Systems: The use of fans and blowers to improve air circulation highlights the importance of ensuring safe and healthy working conditions for laborers.
- Ventilation Challenges in Ascending Tunnels: The paper discusses the unique ventilation problems presented by the ascending grade of the Hackensack tunnel.
- Concrete Lining Techniques: The paper delves into the complexities of building the concrete lining, emphasizing the need for precise planning and coordination.
- Traveling Gantry Systems: The use of traveling gantries to hoist and move concrete buckets illustrates the importance of efficient material handling systems in large-scale construction projects.
- Sand-Walls and Water-Proofing: The use of sand-walls and water-proofing in the wet sections of the tunnel showcases the need to adapt to varying moisture conditions.
- Expanding Mandrels for Conduit Installation: The innovative use of expanding mandrels for installing conduit lines demonstrates the importance of finding efficient and precise solutions for specific challenges.
- Project Organization and Cost Management: The paper emphasizes the importance of careful planning, effective organization, and diligent cost management in large-scale construction projects.
- Staff Organization: The detailed diagrams of the engineering staff organization highlight the importance of having a well-structured team for successful project implementation.
- Cost Estimates: The inclusion of detailed cost estimations and the analysis of factors influencing cost provide valuable insights into project budgeting and resource management.
Historical Context:
This paper was written in 1910, during a period of rapid industrialization and expansion in the United States. The construction of the Bergen Hill Tunnels represents the growing need for efficient transportation infrastructure to accommodate the expanding urban centers and burgeoning economy. The paper sheds light on the state-of-the-art construction techniques and engineering practices of the time, highlighting the challenges and innovations faced by engineers in building large-scale infrastructure projects.
Facts:
- The Bergen Hill Tunnels are part of the Pennsylvania Railroad’s New York Tunnel Extension.
- The tunnels are located west of the Hudson River and pass through a trap dike known as Bergen Hill.
- The tunnels are two parallel single-track tunnels with a center line aligned with 32nd Street, New York City.
- The tunnels have a grade of 1.3% ascending from east to west.
- The length of each tunnel between the portals is 5,920 feet.
- A shaft 212 feet deep was sunk at Central Avenue, located 3,620 feet from the Weehawken Shaft.
- The excavation was completed by December 31st, 1908.
- The tunnels pass through a fault zone for a distance of nearly 400 feet.
- The trap rock encountered in the tunnels varied in texture and color due to different amounts of quartz and feldspar.
- The temperature in the tunnels remained nearly stationary between 50° in winter and 60° in summer.
- The tunnels were excavated entirely by the center top heading method.
- The specific gravity of the hardest trap rock found was 2.98.
- The average time to drill a 10-foot hole in the hardest trap rock was almost 10 hours.
- The normal trap rock in the tunnels had a specific gravity ranging from 2.85 to 3.04.
- The normal trap rock in the tunnels weighed from 179 to 190 pounds per cubic foot.
- The average quantity of powder used on the entire work was about 2.9 pounds per cubic yard.
- A depth of 205 feet was sunk in the Central Shaft in 6 months.
- The average time the drills were “actually working” was 5.2 hours per shift.
- The average depth drilled per hour, during the time the drills were “actually working”, was 2.66 feet.
- The excavation was taken out 10% more than what was paid for and 28% more than what the contractor was required to excavate.
- The excavation in the sandstone required a much larger quantity of powder per cubic yard than the trap rock.
Statistics:
- 5,920 feet: The length of each tunnel between the portals
- 212 feet: The depth of the shaft sunk at Central Avenue
- 3,620 feet: The distance between the Weehawken Shaft and Central Avenue
- 940 days: The total number of days worked on the tunnels
- 6.26 feet: The average progress per working day in each tunnel
- 3.13 feet: The average rate of progress for each working face per day
- 40 days: The amount of time lost when work was stopped by the Receiver of the Shields Company
- 1,000 feet: The distance from the Weehawken Shaft where hand mucking was used
- 159 cubic yards: The maximum output of a steam shovel in one shift
- 60 cubic yards: The best average monthly output of a steam shovel
- 90 cubic yards: The average quantity actually handled by a steam shovel per shift
- 2.5 pounds: The average quantity of dynamite used for advancing the main working faces
- 186 pounds: The weight per cubic foot of the hardest trap rock
- 10 hours: The average time required to drill a 10-foot hole in the hardest trap rock
- 179 to 190 pounds: The weight per cubic foot of the normal trap rock
- 20 to 25 minutes: The average time to drill one foot of normal trap rock
- 2.9 pounds: The average quantity of powder used per cubic yard for the entire project
- 3,826 hours: The total “actual working time” of drills over 736 shifts
- 36.6 minutes: The average time per foot drilled in the bench
- 1.64 feet: The average depth drilled per hour in the bench
- 75 gallons per minute: The quantity of water flowing out of the tunnel drains after the completion of the lining
- 2.3 feet: The average rate of progress per day in the timbered section at Weehawken
- 3.2 feet: The average rate of progress per day in the hard sandstone section at Weehawken
- 2.4 feet: The average rate of progress per day in the hard trap rock section at Weehawken
- 4.55 feet: The average rate of progress per day in the ordinary trap rock section at Weehawken
- 4.5 feet: The average length of heading driven per day worked in the North East section of the Central Shaft
- 7.2 feet: The average actual advance per day worked in the bench and enlargement of the Central Shaft headings
- 4.4 feet: The average length of heading driven per day worked in the North West section of the Central Shaft
- 41.8 linear feet: The best week’s work at a working face, equivalent to 803 cubic yards
- 56.6 linear feet: The largest number of yards taken out in any one week from one working face, equivalent to 1,087 cubic yards
- 168.4 linear feet: The total linear feet of full-section tunnel equivalent to 3,238 cubic yards taken out in one week from four working faces
Terms:
- Trap Dike: A geological formation where igneous rock has intruded into sedimentary rock, creating a vertical wall of hard rock.
- Diabase: A type of igneous rock, also known as trap rock, often found in trap dikes.
- Heading: The forward portion of a tunnel, where excavation takes place.
- Bench: The lower portion of a tunnel, excavated after the heading.
- Segmental Timbering: A method of supporting a tunnel using timber beams arranged in a semicircular shape.
- Slugger Drill: A type of jackhammer used for drilling rock.
- Hardpan: A very hard and compacted layer of soil, often found above bedrock.
- Cut-and-Cover: A method of tunnel construction where an open trench is excavated and then covered with a roof.
- Gantries: Overhead structures that support equipment and provide access to areas within a tunnel.
- Conduit Lines: Pipes or tubes that carry electrical cables.
- Water-Proofing: A layer of material applied to prevent water from entering a structure.
Examples:
- Fault Zone: The tunnels pass through a fault zone for nearly 400 feet, presenting challenges due to unstable ground and requiring extensive timbering.
- Hardest Trap Rock: The hardest trap rock encountered in the tunnels had a specific gravity of 2.98, making it extremely difficult to drill. The average time to drill a 10-foot hole in this rock was almost 10 hours.
- Multiple-Drill Headings: To increase excavation speed, the engineers employed multiple-drill headings, with as many as eight drills working simultaneously.
- Ventilation Challenges: Smoke from blasting and locomotives created a significant ventilation challenge, especially in the Hackensack tunnel with its ascending grade.
- Traveling Gantries: Traveling gantries were used to hoist concrete buckets from rail cars to the platform above, allowing for efficient placement of concrete in the arch and bench walls.
- Expanding Mandrels for Conduit Installation: The use of expanding mandrels proved highly effective in installing conduit lines, ensuring a tight fit and preventing grout from entering the ducts.
- Sand-Walls: Sand-walls were constructed in wet sections of the tunnel to provide a smooth surface against which water-proofing could be placed.
- Water-Proofing: To prevent water infiltration, the tunnels were water-proofed using six-ply felt and seven layers of pitch, especially in the wet sections near the river.
- Cut-and-Cover Method: The tunnel was constructed using the cut-and-cover method near the Hackensack portal, where the arch section was widened to accommodate the transition from tunnel to open cut.
- Cost Management: The paper provides detailed cost estimations for labor, materials, and plant operation, highlighting the importance of efficient project budgeting and resource management.
Conclusion:
The construction of the Bergen Hill Tunnels for the Pennsylvania Railroad’s New York Tunnel Extension presented significant engineering challenges due to varied geology, ventilation issues, and the need for efficient concrete lining techniques. The paper highlights the importance of adapting construction methods, embracing innovative drilling techniques, and designing effective ventilation systems to ensure safe and efficient tunnel construction. Furthermore, the paper emphasizes the crucial role of meticulous planning, effective organization, and diligent cost management in achieving success in large-scale infrastructure projects. By providing detailed insights into the construction processes, challenges, and innovations of the Bergen Hill Tunnels, this paper offers valuable lessons for contemporary engineers and underscores the ongoing evolution of engineering practices in building vital transportation infrastructure.