In 1910, J.C. Meem conducted an experiment to see if sand could form a self-supporting arch. What did he find?
- Sand did not form an arch at all.
- Sand formed a very weak arch that collapsed under the slightest pressure.
- Sand formed an arch that could hold a significant amount of weight.
- The experiment was inconclusive.
Correct Answer: Sand formed an arch that could hold a significant amount of weight.
Correct Answer Explanation: Meem’s experiment demonstrated the surprising strength of sand arches. This discovery challenged conventional thinking about soil pressure and had significant implications for the design of underground structures like tunnels.
Meem’s research also focused on the behavior of subaqueous materials, like sand under water. How does water pressure act on sand?
- Water pressure acts directly on the sand grains, increasing the overall pressure.
- Water pressure is transmitted through the voids in the sand, affecting the pressure less directly.
- Water pressure doesn’t affect sand pressure at all.
- Water pressure acts as a unified liquid mass, pushing the sand grains apart.
Correct Answer: Water pressure is transmitted through the voids in the sand, affecting the pressure less directly.
Correct Answer Explanation: Meem’s experiments showed that water pressure doesn’t push directly on sand grains, but rather travels through the empty spaces (voids) between the particles. This understanding is critical for designing structures that can withstand both water pressure and the pressure of the surrounding soil.
Meem’s research highlights the importance of lateral earth pressure in foundation design. How does lateral pressure affect foundations?
- Lateral pressure only impacts the top of the foundation.
- Lateral pressure is a minor factor in foundation stability.
- Lateral pressure can be used to create more stable foundations.
- Lateral pressure acts in opposition to the load on a foundation.
Correct Answer: Lateral pressure can be used to create more stable foundations.
Correct Answer Explanation: Meem argued that lateral pressure, often overlooked, could be utilized to create more efficient and stable foundations. This concept challenged the traditional approach of simply spreading out foundations to distribute the load.
When designing piles to support structures, what should engineers focus on most?
- Skin friction along the entire length of the pile.
- The strength of the material at the tip of the pile.
- The length of the pile.
- The overall diameter of the pile.
Correct Answer: The strength of the material at the tip of the pile.
Correct Answer Explanation: Meem observed that piles driven in soft soil often relied heavily on the bearing value at the tip, while the friction along the sides (skin friction) played a less significant role. This emphasized the importance of selecting a strong material for the tip of a pile, even if the length or diameter of the pile is less.
What is the angle of repose?
- The angle at which a pile is driven into the ground.
- The angle at which a structure can withstand lateral pressure.
- The steepest angle at which a material can stand without collapsing.
- The angle of the ground surrounding a tunnel.
Correct Answer: The steepest angle at which a material can stand without collapsing.
Correct Answer Explanation: The angle of repose is a fundamental concept in soil mechanics. It determines how much a material like sand will naturally slope, which in turn affects how the material will respond to pressure.
In 1910, how much arch timber bracing was used in the Bay Ridge tunnel sewer?
- 1,000 feet.
- 2,000 feet.
- 4,000 feet.
- 8,000 feet.
Correct Answer: 4,000 feet.
Correct Answer Explanation: The Bay Ridge tunnel sewer project involved extensive timber bracing to support the tunnel walls and prevent collapse. This highlights the critical role of bracing in tunnel construction at the time.
Meem’s research highlighted the different behaviors of sand and clay. Which material is considered more resistant to pressure?
- Sand.
- Clay.
- They are both equally resistant to pressure.
- The resistance depends on the water content.
Correct Answer: Clay.
Correct Answer Explanation: Meem’s experiments showed that clay, although softer than sand, could exhibit greater resistance to pressure due to its cohesive properties. This means that clay particles are more attracted to each other, making the material less likely to collapse under load.
What is the “bearing value” of a pile?
- The strength of the material at the tip of the pile.
- The amount of friction between the pile and the soil.
- The overall weight a pile can support.
- The angle at which the pile is driven into the ground.
Correct Answer: The strength of the material at the tip of the pile.
Correct Answer Explanation: The bearing value represents the strength of the material the pile is resting on. This is a critical factor in determining the load-carrying capacity of the pile.
Meem’s research emphasized the importance of understanding soil behavior. What is one factor that can significantly affect soil behavior?
- The angle of the ground.
- The amount of water in the soil.
- The temperature of the soil.
- The color of the soil.
Correct Answer: The amount of water in the soil.
Correct Answer Explanation: Water content is a key factor influencing soil behavior. Moisture affects the strength, cohesion, and compressibility of soil, making it a crucial consideration for engineers.
What is quicksand?
- A type of sand that is very fine and easily compressed.
- A type of sand that is very dry and easily eroded.
- A type of sand that becomes unstable and fluid under water pressure.
- A type of sand that is very dense and difficult to excavate.
Correct Answer: A type of sand that becomes unstable and fluid under water pressure.
Correct Answer Explanation: Quicksand is a specific type of soil that behaves like a liquid when disturbed due to the presence of water pressure. This can create dangerous conditions for structures and construction workers.
Meem’s research challenged conventional theories about soil pressure. What did he argue was often overlooked?
- The weight of the soil.
- The depth of the soil.
- The lateral pressure of the soil.
- The angle of repose of the soil.
Correct Answer: The lateral pressure of the soil.
Correct Answer Explanation: Meem emphasized the importance of considering lateral pressure, the pressure exerted by the soil on the sides of a structure, as a crucial factor in foundation design and stability.
In 1910, what was a common method for raising the roof of a tunnel that had been built too low?
- Using explosives to break up the surrounding soil.
- Using heavy machinery to push the roof upward.
- Using hydraulic jacks to lift the roof.
- Using air pressure to inflate the roof.
Correct Answer: Using hydraulic jacks to lift the roof.
Correct Answer Explanation: Hydraulic jacks were commonly used in tunnel construction to adjust the height of the roof, demonstrating the ingenuity of engineers at the time.
How can the presence of voids in sand affect buoyancy?
- Buoyancy is increased.
- Buoyancy is reduced.
- Buoyancy is not affected.
- Buoyancy is unpredictable.
Correct Answer: Buoyancy is reduced.
Correct Answer Explanation: Buoyancy is related to the volume of water displaced. When voids are present, the volume of water displaced is less, resulting in reduced buoyancy.
What is the term for the frictional resistance between a pile and the surrounding soil?
- Bearing value.
- Skin friction.
- Lateral pressure.
- Angle of repose.
Correct Answer: Skin friction.
Correct Answer Explanation: Skin friction refers to the resistance between the surface of a pile and the soil surrounding it, which is an important factor in determining the load-carrying capacity of the pile.
What is one example of a structure that demonstrates the importance of understanding soil pressure?
- A bridge.
- A skyscraper.
- A tunnel.
- A dam.
Correct Answer: A tunnel.
Correct Answer Explanation: Tunnels are particularly vulnerable to soil pressure and instability, making understanding soil behavior essential for their design and construction.
What is a confined foundation?
- A foundation that is built on a very compact and solid base.
- A foundation that is built within a limited space or volume.
- A foundation that is designed to withstand high lateral pressure.
- A foundation that is designed to minimize its impact on the surrounding environment.
Correct Answer: A foundation that is built within a limited space or volume.
Correct Answer Explanation: Confined foundations, as proposed by Meem, are designed to utilize lateral pressure to distribute the load to deeper, more stable layers of soil. This is often a more efficient approach compared to spreading foundations.
In 1910, what was the typical percentage of voids in sand?
- 10%.
- 20%.
- 30%.
- 40%.
Correct Answer: 40%.
Correct Answer Explanation: Meem’s research used a typical value of 40% for the percentage of voids in sand, which is a commonly accepted value in soil mechanics.
What is one practical application of understanding the arching properties of sand?
- Designing foundations for tall buildings.
- Designing retaining walls for roadways.
- Designing tunnels for transportation.
- Designing bridges for traffic flow.
Correct Answer: Designing tunnels for transportation.
Correct Answer Explanation: The arching behavior of sand is particularly relevant for tunnel design, as it allows for the distribution of load and the creation of stable underground structures.
How does the pressure on a tunnel roof relate to water in the surrounding soil?
- Water pressure has no effect on the pressure on the tunnel roof.
- Water pressure adds to the pressure on the tunnel roof.
- Water pressure reduces the pressure on the tunnel roof.
- Water pressure can either increase or decrease the pressure on the tunnel roof.
Correct Answer: Water pressure adds to the pressure on the tunnel roof.
Correct Answer Explanation: The presence of water in the voids within the soil surrounding a tunnel contributes to the overall pressure on the tunnel roof, along with the weight of the soil itself.
What is a typical range for skin friction on caissons?
- 20 to 60 pounds per square foot.
- 100 to 200 pounds per square foot.
- 200 to 600 pounds per square foot.
- 600 to 1,000 pounds per square foot.
Correct Answer: 200 to 600 pounds per square foot.
Correct Answer Explanation: Skin friction on caissons, which are large, box-like foundations, is generally higher than skin friction on smaller piles, typically ranging from 200 to 600 pounds per square foot.
What is one example of a structure that may experience significant lateral pressure?
- A retaining wall.
- A bridge.
- A skyscraper.
- A dam.
Correct Answer: A retaining wall.
Correct Answer Explanation: Retaining walls are designed specifically to withstand lateral pressure from the soil behind them, making them a prime example of the importance of understanding this type of pressure.
What is the “bearing ring” of a pile?
- A ring of material around the top of the pile.
- A ring of material around the base of the pile.
- A ring of material around the middle of the pile.
- A ring of material that strengthens the pile tip.
Correct Answer: A ring of material around the base of the pile.
Correct Answer Explanation: A bearing ring is a structural element placed at the base of a pile to increase its bearing area and distribute the load more evenly.
What is one way to reduce the skin friction on a pile?
- Increase the length of the pile.
- Increase the diameter of the pile.
- Excavate the soil below the pile.
- Drive the pile faster.
Correct Answer: Excavate the soil below the pile.
Correct Answer Explanation: Removing soil below a pile reduces the contact area between the pile and the surrounding soil, thus decreasing skin friction.
What is a common example of a structure that uses arch timber bracing for support?
- A bridge.
- A tunnel.
- A skyscraper.
- A dam.
Correct Answer: A tunnel.
Correct Answer Explanation: Arch timber bracing is a traditional method of supporting tunnel roofs and walls, demonstrating the importance of arching action in underground structures.
In 1910, what was a common type of pile used in construction?
- California stove-pipe pile.
- Concrete pile.
- Steel pile.
- Timber pile.
Correct Answer: California stove-pipe pile.
Correct Answer Explanation: California stove-pipe piles, which were long, hollow cylinders, were commonly used in construction during the early 20th century.
What is one factor that can significantly affect the strength of timber used in construction?
- The species of the timber.
- The diameter of the timber.
- The age of the timber.
- The moisture content of the timber.
Correct Answer: The moisture content of the timber.
Correct Answer Explanation: Timber strength is greatly influenced by its moisture content. Wet timber is significantly weaker than dry timber, which is why proper drying and treatment are crucial for construction.
What is the primary force that drives water into voids in the surrounding soil during construction?
- Gravity.
- Atmospheric pressure.
- Hydrostatic pressure.
- Capillary action.
Correct Answer: Hydrostatic pressure.
Correct Answer Explanation: Hydrostatic pressure, the pressure exerted by water at rest, is the primary force that drives water into voids in the surrounding soil during construction, especially in saturated environments.
What is one way to reduce the impact of hydrostatic pressure on a structure during construction?
- Using pumps to remove water from the surrounding soil.
- Building the structure in a dry environment.
- Using waterproof materials for the structure.
- Using a foundation that is deep enough to avoid water pressure.
Correct Answer: Using pumps to remove water from the surrounding soil.
Correct Answer Explanation: Using pumps to dewater the construction site can significantly reduce hydrostatic pressure, making construction safer and more efficient.
What is a “sheeted trench”?
- A trench that is lined with timber or other material to prevent collapse.
- A trench that is excavated using a mechanical excavator.
- A trench that is dug in a very dry area.
- A trench that is dug in a very wet area.
Correct Answer: A trench that is lined with timber or other material to prevent collapse.
Correct Answer Explanation: Sheeted trenches are reinforced with timber or other materials to prevent the sides from collapsing under pressure, ensuring the safety of workers and the stability of the excavation.
What is the “thrust” of sand?
- The force exerted by sand against a structure.
- The weight of the sand above a structure.
- The angle of repose of the sand.
- The friction between the sand and the structure.
Correct Answer: The force exerted by sand against a structure.
Correct Answer Explanation: The thrust of sand is the force it exerts against the sides of a structure, a significant factor in foundation design and stability, especially in retaining walls and excavations.
How does the strength of a soft clay arch compare to a sand arch?
- Soft clay arches are weaker than sand arches.
- Soft clay arches are stronger than sand arches.
- Soft clay arches have similar strength to sand arches.
- The strength depends on the water content.
Correct Answer: Soft clay arches have similar strength to sand arches.
Correct Answer Explanation: Despite being softer than sand, clay can also exhibit surprising arching strength due to its cohesive properties, demonstrating the importance of considering the specific characteristics of different soil types.
What is one way to determine if a pile has encountered solid material at its tip?
- The pile sinks quickly and easily.
- The pile sinks slowly and with resistance.
- The pile distorts under heavy hammering.
- The pile breaks or shatters.
Correct Answer: The pile distorts under heavy hammering.
Correct Answer Explanation: Distortion at the tip of a pile is often a sign that it has encountered solid material, indicating that it is resting on a stable base.
What is a common term used to describe the process of removing water from a construction site?
- Dewatering.
- Draining.
- Pumping.
- All of the above.
Correct Answer: All of the above.
Correct Answer Explanation: Dewatering, draining, and pumping are all terms used to describe the process of removing water from a construction site to improve stability and safety.
What is one factor that can impact the load-carrying capacity of a pile in silt?
- The length of the pile.
- The diameter of the pile.
- The strength of the material at the tip of the pile.
- The presence of a solid bearing layer beneath the silt.
Correct Answer: The presence of a solid bearing layer beneath the silt.
Correct Answer Explanation: Piles driven in silt often rely on the presence of a solid bearing layer at their tip for adequate support. Without a solid layer, the pile may rely mainly on skin friction, which can be insufficient in silt.
What is one way to improve the stability of a retaining wall?
- Increase the height of the wall.
- Increase the angle of the wall.
- Reduce the lateral pressure on the wall.
- Increase the lateral pressure on the wall.
Correct Answer: Reduce the lateral pressure on the wall.
Correct Answer Explanation: Reducing lateral pressure on a retaining wall by altering the angle of the wall or using drainage techniques can improve stability and prevent failure.
What is one example of a structure that may experience pressure from both water and soil?
- A dam.
- A bridge.
- A tunnel.
- A skyscraper.
Correct Answer: A dam.
Correct Answer Explanation: Dams are often built in water-saturated environments and are subject to pressure from both the weight of the water they hold back and the pressure of the surrounding soil.
What is one way to determine the bearing value of a pile?
- Measuring the length of the pile.
- Measuring the diameter of the pile.
- Performing a load test on the pile.
- Observing the behavior of the pile as it is driven.
Correct Answer: Performing a load test on the pile.
Correct Answer Explanation: Load tests are performed to determine the maximum load a pile can safely support, which is directly related to its bearing value.
What is one way to reduce the risk of a tunnel collapsing due to soil pressure?
- Building the tunnel in a dry area.
- Building the tunnel in a stable area.
- Using arching action to distribute the load.
- Using reinforced concrete for the tunnel structure.
Correct Answer: Using arching action to distribute the load.
Correct Answer Explanation: Arching action is a natural phenomenon in granular soils that can be utilized to distribute load and reduce the pressure on tunnel walls, enhancing stability.
What is one factor that can significantly affect the pressure on a foundation?
- The weight of the structure.
- The depth of the foundation.
- The type of soil the foundation is built on.
- All of the above.
Correct Answer: All of the above.
Correct Answer Explanation: The weight of the structure, the depth of the foundation, and the type of soil all play a significant role in determining the pressure on a foundation.
What is one example of a structure that may be particularly vulnerable to soil erosion?
- A bridge.
- A tunnel.
- A dam.
- A retaining wall.
Correct Answer: A retaining wall.
Correct Answer Explanation: Retaining walls, especially those built in erodible soil types, are particularly vulnerable to soil erosion, which can compromise their stability and lead to failure.