BUSI401 CHAPTER 2

Question 1

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

Answer 1

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

Question 2

This chapter focuses on building foundation systems — generally referred to as building ________. In providing support for the building’s structure, the substructure is crucial to a building’s ____________

Answer 2

This chapter focuses on building foundation systems — generally referred to as building substructures. In providing support for the building’s structure, the substructure is crucial to a building’s integrity and stability.

Question 3

The primary purpose of building substructures:

To ___________, and to _____________.

The loads include the weight of the building and its contents (________), plus the forces from occupants, wind, snow, earthquakes, temperature effects, and the weight of the soil adjacent to below-ground walls (___________).

Answer 3

The primary purpose of building substructures:

To transfer loads from the building to the ground, and to spread these loads evenly to prevent settlement or lateral movement of the building relative to the underlying soils. The loads include the weight of the building and its contents (dead loads), plus the forces from occupants, wind, snow, earthquakes, temperature effects, and the weight of the soil adjacent to below-ground walls (live loads).

Question 4

The building substructure must be designed to withstand the following effects:

Answer 4

The building substructure must be designed to withstand the following effects:

Compression or downward pressure

Tension or upward pressure

Lateral or sideways pressure

Torsion or twisting pressure

Question 5

How can building substructures be subject to upward pressure?

Answer 5

Light structures can be prone to wind suction pressures that will pull the building out of the ground.

Soil that is saturated with water will result in buoyancy pressures where the portion of the structure that is below grade displaces the fluid (like a ball held under water will want to rise to the surface).

Also, wind or earthquake forces will push sideways on the building — for tall, narrow buildings, one side of the building may lift up if not anchored into the ground properly.

Question 6

This force exerts upward pressure

Answer 6

Tension

Question 7

There are two main substructure categories. The first is a ___________ structure that primarily resists lateral or sideways loading. ___________ and ________ are common examples of retaining structures. The second is a _______ or ________ that primarily resists vertical loading. ____ and ______ are common examples of bearing structures.

Answer 7

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures.

Question 8

This is sideways pressure

Answer 8

Lateral pressure

Question 9

Lateral forces can occur as a result of _ _ _ _ _

Answer 9

Lateral forces can occur as a result of soil subsidence, hydraulic pressure, or seismic forces caused by earthquakes.

Question 10

______or downward pressure, also referred to as ______. The main compressive force is the weight of the building, furnishing and fixtures, and its occupants — together these are known as __________.

Answer 10

Compression or downward pressure, also referred to as bearing pressure. The main compressive force is the weight of the building, furnishing and fixtures, and its occupants — together these are known as gravity load effects.

Question 11

This force is twisting pressure exerted on the building.

Answer 11

Torsion

Question 12

Torsion may occur through seismic events or high wind acting on the building. Torsion usually occurs on asymmetrically shaped buildings. If the building is much taller on one side than on the other, there is greater mass resulting in higher seismic forces and a greater wind area resulting in higher wind forces on that side of the building. The soil must resist the imbalanced forces to prevent the building from rotating.

Answer 12

Torsion may occur through seismic events or high wind acting on the building. Torsion usually occurs on asymmetrically shaped buildings. If the building is much taller on one side than on the other, there is greater mass resulting in higher seismic forces and a greater wind area resulting in higher wind forces on that side of the building. The soil must resist the imbalanced forces to prevent the building from rotating.

Question 13

At any given time, there may be a combination of these forces acting simultaneously on the substructure. The National Building Code of Canada defines specific ___________ to properly account for these effects.

Answer 13

At any given time, there may be a combination of these forces acting simultaneously on the substructure. The National Building Code of Canada defines specific “load combinations” to properly account for these effects.

Question 14

The design of a build­ing’s substructure requires harmony between _ _ _ _ _ _

Answer 14

The design of a build­ing’s substructure requires harmony between architectural science, soil mechanics, and civil engineering.

Question 15

Inadequately designed high-rise building foundations can lead to dramatic results. In areas with unstable clay or sandy soils with high moisture content, __________ can lead to foundation settlement and ultimately to deformation and failure of superstructure elements. The most famous example of this is the Leaning Tower of Pisa in Italy.

Answer 15

Inadequately designed high-rise building foundations can lead to dramatic results. In areas with unstable clay or sandy soils with high moisture content, soil subsidence can lead to foundation settlement and ultimately to deformation and failure of superstructure elements. The most famous example of this is the Leaning Tower of Pisa in Italy.

Question 16

In the structural design of a building, soil is treated similar to other construction materials like concrete or steel. Geotechnical engineers determine strength and stiffness properties of soils using standardized test methods. Soils are classified according to various characteristics such as density, moisture content, and silt content as a primary guide to determine the load carrying capacity. The effect of water on soils is significant and must be considered in foundation design.

Answer 16

In the structural design of a building, soil is treated similar to other construction materials like concrete or steel. Geotechnical engineers determine strength and stiffness properties of soils using standardized test methods. Soils are classified according to various characteristics such as density, moisture content, and silt content as a primary guide to determine the load carrying capacity. The effect of water on soils is significant and must be considered in foundation design.

Question 17

Soil capacity is defined in two primary ways:

Answer 17

Soil capacity is defined in two primary ways:

1. Serviceability - This condition is defined in the building code and is related to occupant comfort rather than public safety. A substructure must be designed such that total settlement and differential settle¬ment are kept below a minimum level (typically 25 mm).

2. Ultimate strength - This condition relates to safety of the occupants. In this case, if the soil were to become overloaded to the point of failure, the building would be placed at risk of collapse or overturning.

Question 18

To illustrate this difference, consider the soil as a marshmallow. If you place a light object on a marshmallow it will simply settle into it by a small amount. This is the serviceability condition. If you place a very heavy object on the marshmallow, it will sink very deep into it, it may pierce through the skin and it will likely tip over. This is the ultimate strength condition.

Answer 18

To illustrate this difference, consider the soil as a marshmallow. If you place a light object on a marshmallow it will simply settle into it by a small amount. This is the serviceability condition. If you place a very heavy object on the marshmallow, it will sink very deep into it, it may pierce through the skin and it will likely tip over. This is the ultimate strength condition.

Question 19

If a structure is placed on top of the soil such that it increases the pressure on the supporting soil, the soil will deform. When a load is imposed on soil there are several microscopic interactions that take place:

Answer 19

Contact pressure between granules

Friction between granules

Compaction

Consolidation

Question 20

When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of _________.

Answer 20

When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of consolidation.

Question 21

_________ of soil causes an increase in density by pushing the granules closer together and decreasing void space.

Answer 21

Compaction of soil causes an increase in density by pushing the granules closer together and decreasing void space.

Question 22

If you pour a jar of marbles on the ground, they will spread out and not form a pile, because their surfaces are smooth with little friction between them. In contrast, jagged rocks will form a pile and the more jagged the rocks, the steeper the sides of the pile can be. This property of the soil is referred to as the _________

Answer 22

If you pour a jar of marbles on the ground, they will spread out and not form a pile, because their surfaces are smooth with little friction between them. In contrast, jagged rocks will form a pile and the more jagged the rocks, the steeper the sides of the pile can be. This property of the soil is referred to as the “friction angle”.

Question 23

Other causes of soil deformation include _ _ _ _ _ _ _.

Answer 23

Other causes of soil deformation include frost movements and shrinkage. These deformations are the result of climatic changes.

Question 24

Extending the foun­dation below the zone of frost penetration will prevent frost effects; this is the primary reason that _ _ _ _ _ _ _

Answer 24

Extending the foun­dation below the zone of frost penetration will prevent frost effects; this is the primary reason that houses in Canada have basements

Question 25

______ is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement.

Answer 25

Shear is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement.

Question 26

________ is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called ________and is based on the molecular structure of the material. For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Answer 26

Shear is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called shear strength and is based on the molecular structure of the material. For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Question 27

Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called __________ and is based on the molecular structure of the material.

For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Answer 27

Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called shear strength and is based on the molecular structure of the material.

For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Question 28

The shear strength of a soil is dependent on _____ and _____.

The _____ of a soil is primarily dependent on the water content and is a measure of soil’s strength due to its particles adhering to one another.

The ______ component of shear strength is the measure of the ease with which individual soil particles can be forced to slide past each other.

Answer 28

The shear strength of a soil is dependent on cohesion and friction.

The cohesion of a soil is primarily dependent on the water content and is a measure of soil’s strength due to its particles adhering to one another.

The friction component of shear strength is the measure of the ease with which individual soil particles can be forced to slide past each other.

Question 29

The cohesion of a soil is primarily dependent on the ________ and is a measure of soil’s strength due to its particles adhering to one another.

Answer 29

The cohesion of a soil is primarily dependent on the water content and is a measure of soil’s strength due to its particles adhering to one another.

Question 30

Soils with smooth particles have a very low friction angle whereas soils with rough particles have a high friction angle. It is for this reason that ________ is synonymous with ________.

Answer 30

Soils with smooth particles have a very low friction angle whereas soils with rough particles have a high friction angle. It is for this reason that friction angle is synonymous with shear angle.

Question 31

In high seismic regions, soil stiffness is critical. Soil stiffness is categorized by a parameter called _______. This ranges from Site Class A —bedrock to Site Class F — weak, soft saturated soil. Because softer soils tend to amplify seismic ground motions, the site classification must be known prior to determining the design loads for a building in a seismic zone.

Answer 31

In high seismic regions, soil stiffness is critical. Soil stiffness is categorized by a parameter called site class. This ranges from Site Class A —bedrock to Site Class F — weak, soft saturated soil. Because softer soils tend to amplify seismic ground motions, the site classification must be known prior to determining the design loads for a building in a seismic zone.

Question 32

Another very important property of soil related to its structural capacity is the ______ or _____.

Answer 32

Another very important property of soil related to its structural capacity is the unit weight or density. The density of the soil will be related to the density of the actual soil particles (i.e., granules), as well as how closely packed together they are. Recall that fewer void spaces translates to increased density and, in turn, higher unit weight.

Question 33

With respect to foundation design, ______ and _____ influence the ability of the underlying soil to support the downward forces being exerted on it by the building foundation

Answer 33

With respect to foundation design, shear strength and unit weight influence the ability of the underlying soil to support the downward forces being exerted on it by the building foundation

Question 34

In order for a foundation to remain in static equilibrium (i.e., remain in one place), the resisting force of the soil has to be in equilibrium with the downward force of the foundation. The equal forces cancel each other out and as a result the foun­dation does not settle or heave. The resisting force of the soil is measured as ____________

Answer 34

In order for a foundation to remain in static equilibrium (i.e., remain in one place), the resisting force of the soil has to be in equilibrium with the downward force of the foundation. The equal forces cancel each other out and as a result the foun­dation does not settle or heave. The resisting force of the soil is measured as allowable bearing pressure.

Question 35

In seismic regions, determination of the Site Class is required before the seismic design loads can be established. There are several methods used to determine the soil properties of a given site. List 4

Answer 35

First, geological maps can provide general information regarding soils. However, this will give only an approximation of soil type —in an area of one type of geological formation there may be isolated pockets of a non-typical material.

Second, a local excavation contractor may be able to indicate the soil type fairly closely.

Third, a soils engineer will likely have historical knowledge of the soil properties within their region of practice.

The best and most accurate way to ascertain soil conditions is to employ a soils engineer to dig test pits, make test borings, and conduct standard penetration testing (SPT). Test pits and borings are the two most commonly used exploration methods to obtain soil samples for testing

Question 36

_______ are large, open excavations that allow undis­turbed (in-situ) samples to be taken from the wall of the excavation, and allow __________ tests to be carried out at the bottom of the pit.

Answer 36

Test pits (trial holes) are large, open excavations that allow undis­turbed (in-situ) samples to be taken from the wall of the excavation, and allow load-bearing tests to be carried out at the bottom of the pit.

Question 37

_______ yield samples satisfactory for determining the soil layering, classification, moisture content, and compaction capabilities. A _______ enables the engineer to examine the soil to a far greater depth and to ensure that a satisfactory bottom is reached, not just a thin crust of rock or hardpan covering an unstable soil.

Answer 37

Borings (drilling) yield samples satisfactory for determining the soil layering, classification, moisture content, and compaction capabilities. A test boring enables the engineer to examine the soil to a far greater depth and to ensure that a satisfactory bottom is reached, not just a thin crust of rock or hardpan covering an unstable soil.

Question 38

_________ involves a thin-walled tube approximately 50mm in diameter that is driven into the ground at the bottom of a borehole by blows with a 63.5kg slide hammer. The test result yields the number of blows required to penetrate the soil each 150mm up to a depth of 450mm.

Answer 38

Standard penetration testing (SPT) involves a thin-walled tube approximately 50mm in diameter that is driven into the ground at the bottom of a borehole by blows with a 63.5kg slide hammer. The test result yields the number of blows required to penetrate the soil each 150mm up to a depth of 450mm.

Question 39

When properly performed, the results of a soil exploration and testing program provide the designer and construction professional with the information necessary to make decisions regarding the depth and type(s) of foundation required. One of the goals of this analysis is to determine the depth of the bearing layer or the soil layer that has sufficient strength to withstand the building’s loads. The deeper the foundations must extend to reach a soil bearing layer, the more difficult it is to build the substructure and hence the overall project cost is higher.

Answer 39

When properly performed, the results of a soil exploration and testing program provide the designer and construction professional with the information necessary to make decisions regarding the depth and type(s) of foundation required. One of the goals of this analysis is to determine the depth of the bearing layer or the soil layer that has sufficient strength to withstand the building’s loads. The deeper the foundations must extend to reach a soil bearing layer, the more difficult it is to build the substructure and hence the overall project cost is higher.

Question 40

List the two main substructure categories.

Answer 40

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures.

The second is a bearing or foundation structure that primarily resists vertical loading.

Question 41

________ are common examples of bearing structures.

Answer 41

Piles and pad footings are common examples of bearing structures.

Question 42

There are two main substructure categories.

The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading.

Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

Answer 42

There are two main substructure categories.

The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading.

Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

Question 43

________of soil causes an increase in density by pushing the granules closer together and decreasing void space.

Answer 43

Compaction of soil causes an increase in density by pushing the granules closer together and decreasing void space.

Question 44

Water that is held within a soil will occupy the void spaces between the granules. When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of ________.

Answer 44

Water that is held within a soil will occupy the void spaces between the granules. When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of consolidation.

Question 45

Shear is a strain produced in a material when _ _ _ _ _ _ _.

Answer 45

Shear is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction.

Question 46

Standard penetration testing (SPT) involves _ _ _ _ _ _ _ _

Answer 46

Standard penetration testing (SPT) involves a thin-walled tube approximately 50mm in diameter that is driven into the ground at the bottom of a borehole by blows with a 63.5kg slide hammer. The test result yields the number of blows required to penetrate the soil each 150mm up to a depth of 450mm. The final number is given as the “blow count” or “N-value” representing the sum of the number of blows for the second and third 150mm segments.

Question 47

Standard penetration testing (SPT) involves a _ _ _ _ _ that is driven into the ground at the bottom of a ______ by blows with a 63.5kg slide hammer. The test result yields the _ _ _ _ _required to penetrate the soil each 150mm up to a depth of 450mm. The final number is given as the “_______” or “______” representing the sum of the number of blows for the second and third 150mm segments.

Answer 47

Standard penetration testing (SPT) involves a thin-walled tube approximately 50mm in diameter that is driven into the ground at the bottom of a borehole by blows with a 63.5kg slide hammer. The test result yields the number of blows required to penetrate the soil each 150mm up to a depth of 450mm. The final number is given as the “blow count” or “N-value” representing the sum of the number of blows for the second and third 150mm segments.

Question 48

This is a mixture of cement, sand, and water applied through a pressure hose, producing a dense hard layer of concrete used in building for lining tunnels and structural. repairs.

Answer 48

Gunite

Question 49

There are a variety of retaining wall systems intended to shore or brace the walls of the excavation during excavation, but not intended to be permanent. Such measures may be removed after construction or may remain in place but not form part of the final structure.

Banks may be protected from water action by polyethylene film spread from a point approximately six feet outside the bank and continuing over the face of the bank to the bottom of the footing.

Answer 49

There are a variety of retaining wall systems intended to shore or brace the walls of the excavation during excavation, but not intended to be permanent. Such measures may be removed after construction or may remain in place but not form part of the final structure.

Banks may be protected from water action by polyethylene film spread from a point approximately six feet outside the bank and continuing over the face of the bank to the bottom of the footing.

Question 50

In a small site, horizontal struts may be used to brace the lateral loads of the opposite walls against each other. This allows work to take place within a protected prefabricated steel trench shield or trench box enclosure. Such systems are commonly used in civil works that involve the installation of underground pipes where the work area is comprised of a deep narrow trench. Once the pipes have been installed, the trench is backfilled while the trench shield is pulled out.

Answer 50

In a small site, horizontal struts may be used to brace the lateral loads of the opposite walls against each other. This allows work to take place within a protected prefabricated steel trench shield or trench box enclosure. Such systems are commonly used in civil works that involve the installation of underground pipes where the work area is comprised of a deep narrow trench. Once the pipes have been installed, the trench is backfilled while the trench shield is pulled out.

Question 51

A ________ system is a series of horizontal reinforcing bars that are driven or bored into sides of the foundation and encased in concrete grout. A ________ is then applied to the vertical walls of the excavation and sprayed with shotcrete.

A _______ wall is constructed in tandem with the excavation of the substructure beginning at the existing grade and proceeding down in 0.5 to 2.0-metre segments. Drainage must be incorpor­ated into the structure through ______ or a ________

Answer 51

A soil-nailing system is a series of horizontal reinforcing bars that are driven or bored into sides of the foundation and encased in concrete grout. A steel mesh is then applied to the vertical walls of the excavation and sprayed with shotcrete. A soil-nailed wall is constructed in tandem with the excavation of the substructure beginning at the existing grade and proceeding down in 0.5 to 2.0-metre segments. Drainage must be incorpor­ated into the structure through weep-holes or a drainage element to relieve water pressure.

Question 52

Retaining Structures

When excavating to construct a foundation, the stability of the side slopes must be maintained. If the excavation is more than _______ (as a rule of thumb) or is adjacent to other properties or roadways, some type of shoring may be required. The type of soil will largely govern the require­ment. In solid rock or hardpan, shoring is seldom required.

Answer 52

Retaining Structures

When excavating to construct a foundation, the stability of the side slopes must be maintained. If the excavation is more than five feet deep (as a rule of thumb) or is adjacent to other properties or roadways, some type of shoring may be required. The type of soil will largely govern the require­ment. In solid rock or hardpan, shoring is seldom required.

Question 53

There are several techniques commonly used for retaining walls:

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Answer 53

There are several techniques commonly used for retaining walls:

• Temporary retaining walls
• Soil nailing and grouting the excavation walls
• Sheet piling
• Soldier piles and cross bracing
• Cantilever supports

Question 54

In a small site, ________ may be used to brace the lateral loads of the opposite walls against each other. This allows work to take place within a protected prefabricated steel trench shield or trench box enclosure.

Answer 54

In a small site, horizontal struts may be used to brace the lateral loads of the opposite walls against each other. This allows work to take place within a protected prefabricated steel trench shield or trench box enclosure.

Question 55

A ______ system is a series of horizontal reinforcing bars that are driven or bored into sides of the foundation and encased in concrete grout.

A ______ is then applied to the vertical walls of the excavation and sprayed with shotcrete.

A soil-nailed wall is constructed in tandem with the excavation of the substructure beginning at the existing grade and proceeding down in 0.5 to 2.0-metre segments.

Answer 55

A soil-nailing system is a series of horizontal reinforcing bars that are driven or bored into sides of the foundation and encased in concrete grout. A steel mesh is then applied to the vertical walls of the excavation and sprayed with shotcrete. A soil-nailed wall is constructed in tandem with the excavation of the substructure beginning at the existing grade and proceeding down in 0.5 to 2.0-metre segments.

Question 56

Soil nailing systems offers several advantages for substructure retaining walls:

Answer 56

Soil nailing systems offers several advantages for substructure retaining walls:

The most significant advantage is that the retaining system can be installed in areas with limited space, a common problem in urban areas where buildings often extend to the lot lines and the land under adjacent buildings must be supported during excavation.

Soil nailing systems can follow an irregular curvilinear boundary.

Soil nailing systems can be modified as required to meet different soil conditions as the excavation progresses - for example, the spacing of the nails can be changed as soils become weaker or stronger.

The installation usually requires less labour and equipment than other retaining systems.

Question 57

_______ are a soil nailing application that adds additional stability and strength.

____________are placed into drilled holes in the surrounding soil or rock and the rods are set into the soil/rock with a grout.

Answer 57

Tie-backs are a soil nailing application that adds additional stability and strength. Threaded metal rods are placed into drilled holes in the surrounding soil or rock and the rods are set into the soil/rock with a grout.

Question 58

_________ consist of a series of corrugated steel plates driven or vibrated into the ground vertically into the edge of the excavation and act as cantilevers to hold back the soil.

Answer 58

Sheet piling systems consist of a series of corrugated steel plates driven or vibrated into the ground vertically into the edge of the excavation and act as cantilevers to hold back the soil.

Question 59

Sheet piling systems offer the following advantages:

Answer 59

Sheet piling systems offer the following advantages:

Ideal for situations where adjoining soils are weak or have high moisture content or for substructures excavated below the water table.

Sheet piling will maintain its shape during installation.

Since the installation of sheet piling involves displacement of soil rather than excavation, the risk to loss of integrity of the adjoining soils is reduced.

Sheet piling can be made to be corrosion resistant so that it can be left in place after construction is completed.

Question 60

The key disadvantage of sheet piling is _ _ _ _ _. The other problem is _ _ _ _ _

Answer 60

The key disadvantage of sheet piling is the greater expense relative to soil nailing. The other problem is that the installation of sheet piling to retain deep excavation walls must be staggered since there is a practical depth that this type of piling can be driven

Question 61

NOTE ON SHEET PILES

The sequence of construction is different with sheet piles when compared to the use of soil nails. With sheet piles, the piles are driven first. The excav­ation occurs adjacent to the piles to the required depth. The sheets must be driven to a depth that is much greater than the depth of the excavation.

Answer 61

NOTE ON SHEET PILES

The sequence of construction is different with sheet piles when compared to the use of soil nails. With sheet piles, the piles are driven first. The excav­ation occurs adjacent to the piles to the required depth. The sheets must be driven to a depth that is much greater than the depth of the excavation.

Question 62

This system is also known as a sleeper wall or Berlin wall.

Answer 62

Soldier Piling

Question 63

________ retaining walls are usually associated with shallow foundations or free-standing applications, such as perimeter site retaining walls

Answer 63

Cantilever designed retaining walls are usually associated with shallow foundations or free-standing applications, such as perimeter site retaining walls

Question 64

Cantilever Retaining Wall

A variation of this retaining system is a wide concrete pad that extends horizontally beyond the retaining wall. The wall is then poured and attached to the concrete pad through steel reinforcing. The pad system uses the weight of the soil above it to create a cantilever to resist the lateral forces of the adjoining soils.

Answer 64

Cantilever Retaining Wall

A variation of this retaining system is a wide concrete pad that extends horizontally beyond the retaining wall. The wall is then poured and attached to the concrete pad through steel reinforcing. The pad system uses the weight of the soil above it to create a cantilever to resist the lateral forces of the adjoining soils.

Question 65

Building substructures may be either shallow or deep.

A shallow foundation is suitable where _________________ In this case, the foundation is located just below the zone of frost penetration, typically 1.5 to 2m below grade. This type of foundation is generally associated with single storey or low-rise commercial and industrial buildings.

Answer 65

Building substructures may be either shallow or deep.

A shallow foundation is suitable where the bearing capacity of the soil near the surface is sufficient to support the building’s loads. In this case, the foundation is located just below the zone of frost penetration, typically 1.5 to 2m below grade. This type of foundation is generally associated with single storey or low-rise commercial and industrial buildings.

Question 66

In contrast, a deep foundation is needed where __________. Piles, piers, or caissons (defined in the following section) are used to develop the required soil capacities. In some situations, a deep foundation is required to accommo­date multiple levels of below-grade use, such as underground parking.

Answer 66

In contrast, a deep foundation is needed where competent bearing material is not available near the ground surface. Piles, piers, or caissons (defined in the following section) are used to develop the required soil capacities. In some situations, a deep foundation is required to accommo­date multiple levels of below-grade use, such as underground parking.

Question 67

With either type of foundation (shallow or deep), the building superstructure must be anchored to the foundation. A steel frame building would use ________, while a concrete frame building would simply __________.

Shallow foundations are usually composed of square or strip concrete footings with steel reinforcing. The footings are called spread footings as they “spread” the load from the relatively small columns or piers to the larger footing surfaces.

Answer 67

With either type of foundation, the building superstructure must be anchored to the foundation. A steel frame building would use anchor bolts, while a concrete frame building would simply become an extension of the reinforced concrete foundation walls.

Shallow foundations are usually composed of square or strip concrete footings with steel reinforcing. The footings are called spread footings as they “spread” the load from the relatively small columns or piers to the larger footing surfaces.

Question 68

Shallow foundations are usually composed of _ _ _ _ _ footings with steel reinforcing. The footings are called ________ as they “spread” the load from the relatively small columns or piers to the larger footing surfaces.

Answer 68

Shallow foundations are usually composed of square or strip concrete footings with steel reinforcing. The footings are called spread footings as they “spread” the load from the relatively small columns or piers to the larger footing surfaces.

Question 69

When individual footings become large enough, it is more economical to merge them into a single ________. ______ foundations, sometimes known as _________, consist of one continuous footing placed under the entire building area. The ____ is generally a thick, heavily reinforced slab. ____ are generally used where bearing capacity of the soil is low, compared to the weight of the building, and where pilings are not feasible. They are commonly used for soils that have high moisture content.

Answer 69

When individual footings become large enough, it is more economical to merge them into a single mat or a raft foundation. Raft foundations, sometimes known as floating foundations, consist of one continuous footing placed under the entire building area. The raft is generally a thick, heavily reinforced slab. Rafts are generally used where bearing capacity of the soil is low, compared to the weight of the building, and where pilings are not feasible. They are commonly used for soils that have high moisture content.

Question 70

Raft foundations have greater limitations in the loads that can be supported relative to conventional deep substructures. However, a raft foundation may be suitable for a parking garage or light steel low-rise building.

Answer 70

Raft foundations have greater limitations in the loads that can be supported relative to conventional deep substructures. However, a raft foundation may be suitable for a parking garage or light steel low-rise building.

Question 71

Deep foundations are generally used to reach deeper, competent founda­tion material. This may be necessary:

Answer 71

Deep foundations are generally used to reach deeper, competent founda­tion material. This may be necessary:

when there is a lack of adequate soil strength for the bearing of shallow footings;

when building underwater or in marine environments;

when building very close to an existing structure;

to increase the structure’s resistance to wind loads that push hori­zontally and tend to overturn the building; or

to support structures that are highly sensitive to settlement.

Question 72

List three types of deep foundations:

Answer 72

Three types of deep foundations include:

• piles;
• piers; and
• caissons.

Question 73

A _____ is basically a long cylinder of a strong material such as concrete that is pushed into the ground to act as a steady support for structures built on top of it.

Answer 73

A pile is basically a long cylinder of a strong material such as concrete that is pushed into the ground to act as a steady support for structures built on top of it.

Question 74

Pile foundations are used in the following situations:

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Answer 74

Pile foundations are used in the following situations:

When there is a layer of weak soil at the surface. This layer cannot support the weight of the building, so the loads of the building have to bypass this layer and be transferred to the layer of stronger soil or rock that is below the weak layer.

When a building has very heavy, concentrated loads, such as in a high rise structure, bridge, or water tank.

Question 75

Piles can transfer building loads by either _ _ _ _ _ _

Answer 75

Piles can transfer building loads by either friction or end-bearing.

Friction piles are designed to transfer their load into the soil through the friction they develop along their length.

End-bearing piles rest on a bearing stratum, transferring their load onto this end-point, usually a hard layer such as rock.

Question 76

Friction piles are designed to _ _ _ _ _

Answer 76

Friction piles are designed to transfer their load into the soil through the friction they develop along their length.

Question 77

________ rest on a bearing stratum, transferring their load onto this end-point, usually a hard layer such as rock.

Answer 77

End-bearing piles rest on a bearing stratum, transferring their load onto this end-point, usually a hard layer such as rock.

Question 78

Civil engineers design piling systems to work as distinct groups of associated piles. These piles are intended to work in tandem as a unified structural element to support building loads. The grouping of piles is tied together with a stiff reinforced concrete cap to transfer loads from a superstructure column to a foundation pile group. Pile caps serve three main goals:

1. The building load is distributed equally over the pile group —meaning a broader area of bearing soil than a single pile installation.

2. Each pile connected to the pile cap is stabilized, increasing overall stability of the piling group.

3. The pile cap provides the necessary combined resistance to the loads and stresses imposed by the soils adjoining the foundation and building superstructure.’

Answer 78

Civil engineers design piling systems to work as distinct groups of associated piles. These piles are intended to work in tandem as a unified structural element to support building loads. The grouping of piles is tied together with a stiff reinforced concrete cap to transfer loads from a superstructure column to a foundation pile group. Pile caps serve three main goals:

1. The building load is distributed equally over the pile group —meaning a broader area of bearing soil than a single pile installation.

2. Each pile connected to the pile cap is stabilized, increasing overall stability of the piling group.

3. The pile cap provides the necessary combined resistance to the loads and stresses imposed by the soils adjoining the foundation and building superstructure.’

Question 79

PIERS

Piers (or shafts) are end-bearing vertical elements placed by drilling or excavating soil down to the bearing level and then filling with cast-in-place reinforced concrete. A casing may be necessary for stabilization and to allow for inspection of the bearing surface.

Answer 79

PIERS

Piers (or shafts) are end-bearing vertical elements placed by drilling or excavating soil down to the bearing level and then filling with cast-in-place reinforced concrete. A casing may be necessary for stabilization and to allow for inspection of the bearing surface.

Question 80

A ______ is a cylindrical site-cast concrete foundation that penetrates through unsatisfactory soil to rest upon an underlying stratum of rock or satisfactory soil.

Answer 80

A caisson is a cylindrical site-cast concrete foundation that penetrates through unsatisfactory soil to rest upon an underlying stratum of rock or satisfactory soil.

Question 81

This is a shaft of concrete placed under a building column or wall and extending down to hardpan or rock.

Answer 81

caisson