Which of the following engineering challenges did the Pennsylvania Railroad East River tunnel project face?
- Blow-outs
- Settlements
- Water ingress
- All of the above
Correct Answer: All of the above
Correct Answer Explanation: The East River tunnels faced all of these challenges. Blow-outs occurred when air escaped through porous ground, settlements involved ground movement, and water ingress was a constant threat due to the tunnels’ location beneath the East River.
What was the primary method used for excavating the East River tunnels?
- Open cut excavation
- Drill and blast
- Shield tunneling
- All of the above
Correct Answer: Shield tunneling
Correct Answer Explanation: Shield tunneling was the primary method used for excavating the East River tunnels. This method involved using a large, cylindrical structure to support the surrounding ground and prevent cave-ins.
What was the primary purpose of compressed air in the tunnel construction?
- To provide ventilation for workers
- To control ground conditions and prevent water ingress
- To power the excavation machinery
- To support the weight of the tunnel lining
Correct Answer: To control ground conditions and prevent water ingress
Correct Answer Explanation: Compressed air was essential for controlling ground conditions and preventing water ingress during the excavation of the East River tunnels. The air pressure kept the ground stable and prevented water from flowing into the tunnel.
What unique solution was employed to address blow-outs in the tunnels?
- Using a clay blanket
- Installing a drainage system
- Strengthening the tunnel lining
- Injecting grout into the ground
Correct Answer: Using a clay blanket
Correct Answer Explanation: To control air pressure and minimize blow-outs, a clay blanket was placed over the tunnel. This layer of clay helped to prevent air from escaping and reduced the frequency of blow-outs.
What was the average rate of lowering the caissons through solid rock?
- 0.7 ft per day
- 0.48 ft per day
- 0.39 ft per day
- 1.0 ft per day
Correct Answer: 0.48 ft per day
Correct Answer Explanation: The average rate of lowering the caissons through solid rock was slower than through earth, averaging 0.48 ft per day for the south caisson and 0.39 ft per day for the north caisson. This was due to the increased difficulty of excavating through rock.
What material was used to construct the tunnel lining?
- Concrete
- Brick
- Cast iron
- Steel
Correct Answer: Cast iron
Correct Answer Explanation: The East River tunnels were lined with cast iron segments, which were joined together to form a continuous ring. This type of lining provided strength and stability to the tunnels.
Which of the following was not a material encountered during the tunnel excavation?
- Hudson schist
- Fordham gneiss
- Granite
- Sand and gravel formations
Correct Answer: Granite
Correct Answer Explanation: The East River tunnels encountered various materials, including Hudson schist, Fordham gneiss, and sand and gravel formations, but granite was not one of them.
What was the total quantity of free air compressed for the tunnels and caissons?
- 34,109,000,000 cu. ft.
- 10,615,000,000 cu. ft.
- 220,000 cu. ft.
- 25,000 cu. ft.
Correct Answer: 34,109,000,000 cu. ft.
Correct Answer Explanation: A massive amount of air was needed to operate the compressed air system during the tunnel construction, reaching a total of 34,109,000,000 cu. ft. This included air used for both excavation and power purposes.
What was the primary method used to drain the tunnels?
- Gravity drainage
- Pumps
- Air pressure
- None of the above
Correct Answer: Pumps
Correct Answer Explanation: Sump and pump chambers were constructed in each pair of tunnels to collect water for drainage. Pumps were used to remove this water and keep the tunnels dry.
How many broken plates occurred in the river tunnels during construction?
- 319
- 42
- 249,647
- 10,615,000,000
Correct Answer: 319
Correct Answer Explanation: During the construction of the East River tunnels, 319 broken plates were documented, representing 0.42% of the total number erected. This highlights the challenges and potential for damage during the tunnel construction process.
What was the average cost of grout ejected outside of the river tunnels?
- 93 cents per bbl.
- $2.77 per bbl.
- $6.70 per cu. yd.
- $2.42 per cu. yd.
Correct Answer: $2.77 per bbl.
Correct Answer Explanation: The cost of grouting was a significant expense, and the average cost of grout ejected outside of the river tunnels was $2.77 per bbl. for top charges.
What was the average labor cost chargeable against caulking the joints between segments?
- 12 cents per lin. ft.
- 0.039 cents per ft. of duct
- 0.083 cents per ft. of duct
- $6.70 per cu. yd.
Correct Answer: 12 cents per lin. ft.
Correct Answer Explanation: Caulking the joints between segments was an important part of ensuring the watertightness of the tunnels, and the average labor cost for this task was 12 cents per lin. ft., in addition to top charges.
Which of the following was not a method used for excavating the tunnels?
- Bottom headings
- Full-face methods
- Center headings
- Top headings
Correct Answer: Top headings
Correct Answer Explanation: The East River tunnels employed various excavation methods within the shield, including bottom headings, full-face methods, and center headings, but not top headings. The choice of excavation method was influenced by the geological conditions encountered.
What was the average rate of rock excavation in the Long Island caissons?
- 44.5 cu. yd. per day
- 0.48 ft per day
- 1.05 cu. yd. per ft. of tunnel
- 1-1/2 cu. yd. per ft. of tunnel
Correct Answer: 44.5 cu. yd. per day
Correct Answer Explanation: The rate of rock excavation was significantly slower than the rate of earth excavation in the Long Island caissons, averaging 44.5 cu. yd. per day. This difference is attributed to the increased difficulty of excavating through rock.
What was the primary purpose of the concrete cradles in the East Avenue tunnel?
- To support the tunnel lining
- To provide drainage
- To protect the workers
- To prevent blow-outs
Correct Answer: To support the tunnel lining
Correct Answer Explanation: Concrete cradles were used in the East Avenue tunnel to support the iron lining and reduce the amount of grout required to fill the voids. This proved to be a cost-effective solution compared to filling the voids with grout.
What was the primary cause of the unsuccessful trial of a shield in Tunnel C without compressed air?
- The shield flattened due to lack of support from the surrounding material
- The shield was too small for the tunnel
- The shield malfunctioned
- The workers were not properly trained
Correct Answer: The shield flattened due to lack of support from the surrounding material
Correct Answer Explanation: The shield in Tunnel C flattened due to the lack of support from the surrounding material when compressed air was not used. This demonstrates the importance of compressed air in supporting the shield and preventing it from collapsing.
What was the average cost of labor directly chargeable to concrete in the tunnels?
- $1.80 per cu. yd.
- $3.92 per cu. yd.
- $6.70 per cu. yd.
- $2.42 per cu. yd.
Correct Answer: $1.80 per cu. yd.
Correct Answer Explanation: The cost of concrete work in the tunnels was a significant expense, with the average cost of labor directly chargeable to concrete being $1.80 per cu. yd., in addition to top charges.
What was the purpose of the special junctions at the meeting points of the shields?
- To connect the tunnel lining
- To provide ventilation
- To facilitate drainage
- To protect the workers
Correct Answer: To connect the tunnel lining
Correct Answer Explanation: Special junctions were used at the meeting points of the shields to connect the tunnel lining seamlessly. This ensured the structural integrity and watertightness of the tunnels.
What was the primary method used to place the concrete lining in the tunnels?
- Using a mixing plant in each of the five shafts
- Using a concrete pump
- Using a conveyor belt
- Using a crane
Correct Answer: Using a mixing plant in each of the five shafts
Correct Answer Explanation: The concrete lining for the East River tunnels was placed using a mixing plant in each of the five shafts. The concrete was mixed and transported to the tunnels, where it was placed in normal air.
What was the total length of the four East River tunnels?
- 6,000 ft
- 3,900 ft
- 2,000 ft
- 127 ft
Correct Answer: 6,000 ft
Correct Answer Explanation: The total length of the four East River tunnels was approximately 6,000 ft, including 3,900 ft. under the river and 2,000 ft. in Long Island City. This massive project required sophisticated engineering and construction methods.
What was the purpose of the electric conduits in the tunnel walls?
- To provide electrical wiring
- To support the tunnel lining
- To facilitate drainage
- To protect the workers
Correct Answer: To provide electrical wiring
Correct Answer Explanation: Electric conduits were placed in the tunnel walls to provide electrical wiring for lighting, power, and communication systems within the tunnels. The careful placement and sealing of the conduits were crucial to prevent grout and mortar from entering the duct openings.
What was the name of the company that contracted to construct the East River tunnels?
- S. Pearson and Son, Incorporated
- Pennsylvania Railroad
- Hudson River Construction
- East River Tunnel Construction
Correct Answer: S. Pearson and Son, Incorporated
Correct Answer Explanation: The contract for the construction of the East River tunnels was awarded to S. Pearson and Son, Incorporated. This company employed a profit-sharing model with the Pennsylvania Railroad.
What was the average rate of lowering the caissons through earth?
- 0.7 ft per day
- 0.48 ft per day
- 0.39 ft per day
- 1.0 ft per day
Correct Answer: 0.7 ft per day
Correct Answer Explanation: The average rate of lowering the caissons through earth was 0.7 ft per day. This was significantly faster than the rate of lowering through rock. The sinking process was a complex operation involving hydraulic jacks and blocking.
What was the purpose of the temporary shaft at East Avenue, Long Island City?
- To excavate the land section of the tunnels
- To provide ventilation for workers
- To provide access for construction materials
- To provide a staging area for the construction
Correct Answer: To excavate the land section of the tunnels
Correct Answer Explanation: The temporary shaft at East Avenue was sunk to a depth of 55 ft and used for excavating the land section of the tunnels. This shaft was necessary for the construction process.
What was the primary type of geological formation encountered during the tunnel excavation?
- Sand and gravel
- Rock
- Clay
- Peat
Correct Answer: Rock
Correct Answer Explanation: While the tunnel project encountered various geological formations, including sand and gravel, a significant portion of the excavation was through rock formations like Hudson schist and Fordham gneiss. The presence of these rock formations presented unique challenges for the tunnel construction.
What was the primary design element of the shields used for the river tunnels?
- Sliding hoods and extensions
- Fixed hoods
- Open-face design
- Telescopic design
Correct Answer: Sliding hoods and extensions
Correct Answer Explanation: The shields used for the river tunnels were equipped with sliding hoods and extensions, which were used to support the roof and sides during excavation in mixed earth and rock sections. This design proved to be less effective than fixed hoods.
What was the primary type of lime used as a grouting material in the early stages of the project?
- English Blue Lias lime
- Portland cement
- Quick-setting natural cement
- Hydraulic lime
Correct Answer: English Blue Lias lime
Correct Answer Explanation: The engineers initially experimented with English Blue Lias lime as a grouting material, but it proved unsuitable for supporting the tunnel and was later replaced with a modified quick-setting natural cement. This change was crucial for the structural integrity of the tunnels.
What was the average cost of hand-packed stone used in the East Avenue tunnel?
- $6.70 per cu. yd.
- $2.42 per cu. yd.
- $1.80 per cu. yd.
- $3.92 per cu. yd.
Correct Answer: $2.42 per cu. yd.
Correct Answer Explanation: Hand-packed stone was used in the East Avenue tunnel, and the average cost of this material, including labor and top charges, was $2.42 per cu. yd. This cost reflects the labor involved in placing and packing the stone.
What was the total cost of placing and removing the clay blanket?
- $304,056
- $249,647
- $10,615,000,000
- $34,109,000,000
Correct Answer: $304,056
Correct Answer Explanation: The clay blanket was a crucial element in the project, and the total cost of placing and removing this layer of clay was $304,056. The effectiveness of the clay blanket in controlling air pressure and minimizing blow-outs justified its significant cost.
What was the primary method used for repairing broken plates in the tunnel lining?
- Using steel segments, long bolts, and twisted steel rods
- Replacing the broken plates with new ones
- Injecting grout into the broken plates
- Using a sealant to repair the broken plates
Correct Answer: Using steel segments, long bolts, and twisted steel rods
Correct Answer Explanation: Broken plates were a common issue, particularly in the bottom segments, and repairs were made using steel segments, long bolts, and twisted steel rods. This repair process was crucial for maintaining the structural integrity and watertightness of the tunnels.
What was the maximum loss of free air during a blow-out?
- 220,000 cu. ft.
- 10,615,000,000 cu. ft.
- 34,109,000,000 cu. ft.
- 25,000 cu. ft.
Correct Answer: 220,000 cu. ft.
Correct Answer Explanation: During a blow-out, air escaped through porous ground, leading to a significant loss of air pressure. The maximum loss of free air during a blow-out was 220,000 cu. ft., which occurred over a 10-minute period.
What was the average labor cost chargeable to duct laying in the tunnels?
- $0.039 per ft. of duct
- $0.083 per ft. of duct
- $1.80 per cu. yd.
- $3.92 per cu. yd.
Correct Answer: $0.039 per ft. of duct
Correct Answer Explanation: The laying of electric conduits in the tunnel walls was a specialized task, and the average labor cost chargeable to duct laying was $0.039 per ft. of duct, in addition to top charges.
What was the primary reason for discontinuing the use of compressed air in the tunnel headings?
- The headings reached solid rock
- The air supply was insufficient
- The compressed air system malfunctioned
- The air pressure was too high
Correct Answer: The headings reached solid rock
Correct Answer Explanation: Compressed air was initially used to drive the tunnel headings through soft ground. However, once the headings reached solid rock, the use of compressed air was discontinued. The solid rock provided sufficient support and did not require the use of compressed air.
What was the primary purpose of the shafts on both sides of the East River?
- To provide access for construction materials
- To provide ventilation for workers
- To provide a staging area for the construction
- To provide access to the tunnels
Correct Answer: To provide access to the tunnels
Correct Answer Explanation: The shafts on both sides of the East River were essential for providing access to the tunnels during the construction process. These shafts facilitated the sinking of caissons, the placement of concrete lining, and the removal of excavated material.
What was the average leakage in each tunnel after the rigorous repair process?
- 0.002 cu. ft. per sec.
- 0.00000051 cu. ft. per sec. per lin. ft.
- 220,000 cu. ft.
- 34,109,000,000 cu. ft.
Correct Answer: 0.002 cu. ft. per sec.
Correct Answer Explanation: The tunnels were designed to be watertight, and a rigorous repair process reduced the average leakage in each tunnel to about 0.002 cu. ft. per sec., or 0.00000051 cu. ft. per sec. per lin. ft. This achievement demonstrated the effectiveness of the repair techniques used.
When did construction of the East River tunnels begin?
- May 17th, 1904
- May 17th, 1909
- September 1910
- June 9th, 1904
Correct Answer: May 17th, 1904
Correct Answer Explanation: Construction of the East River tunnels began on May 17th, 1904, and was completed on May 17th, 1909. The project took five years to complete, showcasing the complexity and scale of this engineering feat.
What was the primary reason for the sinking of the Long Island shafts?
- To provide access to the tunnels
- To provide a staging area for the construction
- To provide ventilation for workers
- To provide a source of water for the construction
Correct Answer: To provide access to the tunnels
Correct Answer Explanation: The Long Island shafts were sunk to provide access to the tunnels during construction. These shafts facilitated the sinking of caissons, the placement of concrete lining, and the removal of excavated material.
How many permanent shafts were built on each side of the East River?
- One
- Two
- Three
- Four
Correct Answer: Two
Correct Answer Explanation: The East River tunnel project involved two permanent shafts on each side of the East River, a total of four shafts. These shafts were crucial for access and construction operations.
What was the primary purpose of the shutters used in the shield?
- To control the flow of material and minimize air loss
- To provide ventilation
- To protect the workers
- To support the tunnel lining
Correct Answer: To control the flow of material and minimize air loss
Correct Answer Explanation: Shutters were used in the face of the shield to facilitate excavation in soft ground. These panels helped to control the flow of material and minimize air loss, which was important for maintaining air pressure and safety.
What was the approximate diameter of the tunnel openings in the caissons?
- 25 ft
- 40 ft
- 74 ft
- 127 ft
Correct Answer: 25 ft
Correct Answer Explanation: The Long Island shafts consisted of two steel caissons, each 40 by 74 ft in plan, with walls 5 ft thick. Circular openings for the tunnels, 25 ft in diameter, were provided in the sides of the caissons. These openings were closed by bulkheads during the sinking process.
What was the average cost of concrete cradles used in the East Avenue tunnel?
- $6.70 per cu. yd.
- $2.42 per cu. yd.
- $1.80 per cu. yd.
- $3.92 per cu. yd.
Correct Answer: $6.70 per cu. yd.
Correct Answer Explanation: The concrete cradles used in the East Avenue tunnel averaged 1.05 cu. yd. per ft. of tunnel and cost $6.70 per cu. yd. This cost included labor and top charges. The cost of the concrete cradles reflects the labor and materials involved in their construction and placement.
What was the primary reason for the contractor’s use of a profit-sharing model with the Pennsylvania Railroad?
- To reduce the risk of the project
- To increase the efficiency of the construction
- To incentivize the contractor to complete the project on time and within budget
- All of the above
Correct Answer: All of the above
Correct Answer Explanation: The use of a profit-sharing model between S. Pearson and Son, Incorporated and the Pennsylvania Railroad was a strategic decision to reduce project risk, increase efficiency, and incentivize the contractor to complete the project on time and within budget. This model aligned the interests of both parties and contributed to the success of the project.
What was the primary purpose of the grout dams placed behind the iron lining?
- To retain grout and prevent its loss
- To support the tunnel lining
- To provide drainage
- To prevent blow-outs
Correct Answer: To retain grout and prevent its loss
Correct Answer Explanation: Grout dams were placed behind the iron lining to retain grout and prevent its loss. This ensured the stability and water-tightness of the tunnels. The grout filled voids and sealed spaces in the tunnels, preventing water seepage and maintaining structural integrity.
What was the primary method used to control air pressure during the tunnel excavation?
- Using a clay blanket
- Using a drainage system
- Using a ventilation system
- Using a compressed air system
Correct Answer: Using a clay blanket
Correct Answer Explanation: The clay blanket was the primary method used to control air pressure during the tunnel excavation. This layer of clay helped to prevent air from escaping and reduced the frequency of blow-outs, which was a significant challenge during the project.
What was the primary reason for the sinking of the Manhattan shafts?
- To provide access to the tunnels
- To provide a staging area for the construction
- To provide ventilation for workers
- To provide a source of water for the construction
Correct Answer: To provide access to the tunnels
Correct Answer Explanation: The Manhattan shafts were similar to the Long Island shafts and were sunk to provide access to the tunnels during construction. These shafts facilitated the sinking of caissons, the placement of concrete lining, and the removal of excavated material.
What was the primary reason for the use of a temporary shaft at East Avenue?
- To provide access to the land section of the tunnels
- To provide a staging area for the construction
- To provide ventilation for workers
- To provide a source of water for the construction
Correct Answer: To provide access to the land section of the tunnels
Correct Answer Explanation: A temporary shaft was sunk at East Avenue, Long Island City, to a depth of 55 ft. This shaft was used for excavating the land section of the tunnels, connecting the underwater tunnels to the land-based sections.
What was the primary reason for the use of pneumatic caissons for the construction of the Long Island shafts?
- To sink the shafts through solid rock
- To provide ventilation for workers
- To provide a staging area for the construction
- To provide a source of water for the construction
Correct Answer: To sink the shafts through solid rock
Correct Answer Explanation: Pneumatic caissons were used for the construction of the Long Island shafts because they were designed to sink through solid rock. This method allowed for the construction of deep shafts in a controlled and efficient manner.
What was the primary purpose of the concrete lining in the tunnels?
- To provide support and watertightness
- To protect the workers
- To provide ventilation
- To provide a smooth surface for the trains
Correct Answer: To provide support and watertightness
Correct Answer Explanation: The concrete lining in the tunnels served multiple purposes, primarily to provide support and watertightness. The concrete lining strengthened the tunnel walls, prevented water seepage, and provided a smooth surface for the trains.