Overview:
This paper provides a detailed account of the construction of the New York Tunnel Extension of the Pennsylvania Railroad, specifically focusing on the Terminal Station-West, which spanned approximately 6.3 acres. The project encompassed extensive house-wrecking, complex geological challenges, and meticulous underpinning of existing infrastructure. The construction involved the excavation of a massive volume of rock and earth, necessitating the creation of a material disposal system, including a trestle and pier.
A significant portion of the paper centers on the intricate process of underpinning the Ninth Avenue elevated railway structure, which involved the use of temporary and permanent steel girders, timber bents, and specialized jacking equipment. This intricate process ensured the continued operation of the elevated railway throughout the excavation. The remaining sections detail the construction of the retaining and face walls, which were designed to minimize space loss while providing stability and a finished appearance. The paper concludes with a description of the Tenth Avenue portal and the power-house used to supply compressed air for the project.
Key Findings:
- The project faced challenges related to the complex geology, requiring careful planning and adaptation.
- Innovative techniques were employed to underpin the existing infrastructure, ensuring the safe and efficient completion of the project.
- The extensive use of concrete and steel reflects the era’s advancements in construction materials and techniques.
- Detailed record-keeping and a robust engineering organization facilitated the successful execution of this complex undertaking.
Learning:
- Underpinning Techniques: The paper illustrates the complexities and ingenuity of supporting existing infrastructure during major construction projects. The use of temporary and permanent girders, timber bents, and precise jacking methods highlights the technical challenges and solutions.
- Rock Excavation Methods: The article provides insight into the various techniques used for rock excavation, such as drilling, blasting, and broaching. It also explores the challenges posed by unstable rock and the safety measures employed.
- Concrete Wall Construction: The description of the retaining and face wall construction emphasizes the importance of careful planning, drainage systems, and reinforcement techniques to ensure the durability and stability of these structures.
- Construction Project Management: The detailed information on the engineering organization, record-keeping, and cost accounting highlights the essential aspects of managing a large-scale construction project, emphasizing the need for meticulous planning, communication, and coordination.
Historical Context:
This document offers a glimpse into the rapid urban development of New York City at the turn of the 20th century. The construction of the New York Tunnel Extension of the Pennsylvania Railroad reflects the increasing demand for efficient transportation infrastructure to accommodate the city’s growing population and industrial activity. The project also highlights the technological advancements in construction materials and methods, such as the use of concrete and steel, which facilitated the building of complex structures.
Facts:
- Project scope: The Terminal Station-West covered approximately 6.3 acres.
- Geological challenges: The site encountered gneiss rock, ranging from granite to mica schist, with varying stability and susceptibility to slides.
- Infrastructure support: The project underpinned a three-track elevated railway, a two-track surface railway, and various pipes, sewers, and conduits.
- House-wrecking: 94 buildings were demolished to make way for the Terminal Station-West.
- Material disposal: Excavated materials were transported to a disposal pier via a trestle, showcasing the logistics of large-scale construction.
- Underpinning complexity: The Ninth Avenue elevated railway structure required independent supports for each track due to expansion joints and the lack of rigid attachments between track systems.
- Railway traffic: An average of 90,000 passengers used the Ninth Avenue Elevated Railway daily during the construction.
- Excavation volume: The project removed 521,000 cubic yards of earth and rock, with 87% being solid rock.
- Excavation methods: Drilling, blasting, broaching, and spring holes were employed for rock excavation.
- Concrete mixtures: 1:3:6 and 1:2:3 concrete mixtures were used for various structural elements.
- Concrete placement: Continuous day and night shifts were employed to ensure timely completion of concrete sections.
- Drainage system: Box drains were incorporated into the face walls to prevent water accumulation and pressure build-up.
- Tie-rods: Tie-rods were used to secure the concrete walls to the rock for enhanced stability.
- Forms: Large, movable forms were utilized for constructing the retaining and face walls.
- Tenth Avenue Portal: A close-grained granite from Millstone Point, Connecticut, was used for the portal.
- Power-house: A power-house, equipped with steam and electric air compressors, was established to provide compressed air for the project.
- Disposal pier: The disposal pier was extensively used for unloading materials and loading excavated materials onto scows.
- Engineering force: The project was overseen by a dedicated team of engineers, including a Chief Engineer, Chief Assistant Engineer, and Resident Engineer.
Statistics:
- Excavation: Approximately 502,000 cubic yards of excavation, about 90% being rock.
- Concrete walls: 17,820 cubic yards of concrete walls.
- Structural steel: 1,320,000 pounds of structural steel.
- Timber: 638,000 board feet of framed timber.
- Structural steel used for underpinning: 1,475,000 pounds.
- Weight supported during Ninth Avenue underpinning: 5,000 tons.
- Passengers carried during construction: 100,000,000 passengers.
- Earth excavation: Approximately 57,000 cubic yards of earth.
- Steam shovel performance: An average of 180 cubic yards of earth excavated per 10-hour shift.
- Drill performance: 33 linear feet of drilling per 8-hour shift.
- Excavation per drill shift: 13.9 cubic yards.
- Drilling per cubic yard of excavation: 2.4 feet.
- Excavation per pound of dynamite: 2.2 cubic yards.
- Excavation per derrick shift: 50 cubic yards.
- Derrick force per shift: 13 men.
- Engineering cost: 2.8% of the project cost, with 2.7% attributed to engineering salaries alone.
Terms:
- Gneiss: A metamorphic rock formed from granite or other igneous rocks.
- Contortions: A geological term describing the twisting and bending of rock formations.
- Glacial marks: Scratches or grooves left on rock surfaces by the movement of glaciers.
- Stratification: The arrangement of layers or strata in rocks.
- Batter: The slope or inclination of a wall or other structure.
- Bridge seat: A level surface on a bridge abutment that supports the bridge structure.
- Water-proofing: A process to make a structure resistant to water penetration.
- Tie-rods: Steel rods used to connect concrete walls to the surrounding rock for added stability.
- Diaphragms: Thin, vertical plates inserted into concrete forms to create weak sections, preventing cracking along specific lines.
Examples:
- House-wrecking: The demolition of the Church of St. Michael, fronting on Ninth Avenue, 31st and 32d Streets, involved the Railroad Company building a new church on a different property, showcasing the project’s commitment to minimizing disruption to the community.
- Underpinning: The elaborate process of supporting the Ninth Avenue elevated railway structure involved the use of overhead girders (“B”) and transverse girders (“C”), highlighting the technical expertise and engineering precision required.
- Rock excavation: The slide of approximately 200 cubic yards of rock at Station 188 + 50 illustrates the challenges of working with unstable rock formations.
- Concrete wall construction: The decision to limit the length of the concrete wall sections to 50 feet, despite initial suggestions for 100-foot sections, showcases the ongoing adjustments and decisions made during construction.
- Drainage system: The use of box drains placed behind the face walls, connected to pipes leading through the wall at its base, exemplifies the attention to detail in preventing water damage.
- Tie-rods: The installation of tie-rods, drilled into the rock and secured to the concrete walls, demonstrates the efforts to ensure long-term stability.
- Forms: The use of large, movable forms for constructing the retaining and face walls demonstrates the efficiency and economy of using reusable construction elements.
- Tenth Avenue Portal: The use of close-grained granite from Millstone Point, Connecticut, for the Tenth Avenue Portal showcases the selection of durable and aesthetically pleasing materials for important architectural features.
- Power-house: The establishment of a power-house with a capacity of 19,000 cubic feet of free air per minute highlights the significant energy requirements of such a large-scale construction project.
- Disposal pier: The use of the disposal pier for unloading materials and loading excavated materials onto scows showcases the complex logistics and material management required for successful construction.
Conclusion:
The construction of the New York Tunnel Extension of the Pennsylvania Railroad, particularly the Terminal Station-West, was a monumental undertaking, showcasing the innovative engineering and construction techniques of its time. The project involved extensive excavation, meticulous underpinning of existing infrastructure, and the construction of durable concrete retaining and face walls. This paper provides a valuable record of the project, highlighting the complexities and ingenuity required to navigate geological challenges, manage a large workforce, and ensure the safe and efficient execution of this ambitious project. The detailed description of the methods used, the engineering organization, and the cost accounting provides valuable insights for future construction projects of similar scale and complexity. The paper serves as a testament to the human ingenuity and collaboration that enabled the transformation of the urban landscape and the advancement of transportation infrastructure in New York City.