Counterfort Retaining Wall Quiz and Flashcards

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Questions and Answers

What is the primary purpose of a retaining wall?

To provide lateral support for a vertical or near-vertical slope of soil (correct)

To provide structural support for a building

To prevent erosion of the surrounding landscape

To create additional living space

Which type of retaining wall is the most economical for high walls?

Counterfort retaining walls

Semigravity retaining walls (correct)

Cantilever retaining walls

Gravity retaining walls

What is the main difference between a gravity retaining wall and a semigravity retaining wall?

Gravity walls rely on their own weight for stability, while semigravity walls use soil resting on the masonry

Gravity walls are used for high walls, while semigravity walls are used for low walls

Gravity walls are more economical, while semigravity walls are more expensive to construct

Gravity walls are made of plain concrete or stone masonry, while semigravity walls use reinforced concrete (correct)

What is the main structural component of a cantilever retaining wall?

A thin stem and a base slab Signup and view all the answers

Which type of retaining wall uses a series of counterforts or buttresses to provide additional stability?

Counterfort retaining walls Signup and view all the answers

Which type of retaining wall is generally considered the most expensive to construct?

Cantilever retaining walls Signup and view all the answers

What is the angle, h, that the line AC makes with the vertical in the development of Rankine active pressure along the soil face AB?

$30^\circ$ Signup and view all the answers

According to the passage, which of the following is true about the Coulomb's active earth pressure theory?

It considers both Pa(Coulomb) and the weight of the wall, Wc Signup and view all the answers

What is the range of wall friction angle, δ', for masonry or mass concrete walls mentioned in the passage?

15-30° Signup and view all the answers

According to the passage, which of the following is true about the assumption for the development of Rankine active pressure along the soil face AB?

It is theoretically correct if the shear zone bounded by the line AC is not obstructed by the stem of the wall Signup and view all the answers

Which type of wall is discussed in the passage for the application of Coulomb's active earth pressure theory?

Gravity wall Signup and view all the answers

According to the passage, what is true about the water table problems and hydrostatic pressure in the case of ordinary retaining walls?

Water table problems and hydrostatic pressure are never encountered Signup and view all the answers

What is the typical range for the center-to-center spacing of counterfort slabs in relation to the height (H) of a counterfort retaining wall?

0.3H to 0.7H Signup and view all the answers

For stability checks of cantilever retaining walls using the Rankine earth pressure theory, where is the point A located?

At the edge of the heel of the base slab Signup and view all the answers

Which of the following is NOT considered in the analysis of the stability of a cantilever retaining wall using the Rankine earth pressure theory?

The passive earth pressure force on the toe Signup and view all the answers

What is the assumption made regarding the Rankine active condition when using the Rankine earth pressure theory for stability checks of cantilever walls?

The Rankine active condition is assumed to exist along the vertical plane AB. Signup and view all the answers

For the initial stability checks of retaining walls, what is the general proportion of the stem and the base slab for counterfort retaining walls compared to cantilever walls?

The same as for cantilever walls Signup and view all the answers

What is the typical thickness of the counterfort slabs mentioned in the text?

0.3 m Signup and view all the answers

Which of the following is used to determine the active earth pressure in the given problem?

Coulomb's theory Signup and view all the answers

What is the value of the angle of internal friction (φ) given in the problem?

30° Signup and view all the answers

Which factor of safety is explicitly asked to be determined in the given problem?

Factor of safety against overturning and sliding Signup and view all the answers

What is the significance of the factor of safety against overturning in the design of retaining walls?

It ensures the wall does not rotate about its toe Signup and view all the answers

What is the purpose of calculating the factor of safety against sliding for a retaining wall?

To ensure the wall does not slide horizontally Signup and view all the answers

What is the Rankine passive pressure (Pp) dependent on?

The unit weight of soil in front of the heel and under the base slab, and the Rankine passive earth pressure coefficient Signup and view all the answers

What is the factor of safety against overturning expressed as?

The sum of the moments of forces tending to resist overturning divided by the sum of the moments of forces tending to overturn Signup and view all the answers

What is the overturning moment dependent on?

The active force Pa and the distance from the active force to point C Signup and view all the answers

Which of the following forces contributes to the resisting moment?

All of the above Signup and view all the answers

What is the moment of the force Pv about point C dependent on?

The vertical component of the active force Pv and the width of the base slab B Signup and view all the answers

How can the resisting moment be calculated (neglecting Pp)?

By preparing a table similar to Table 3.1, which includes the weight of the soil above the heel and the weight of the concrete Signup and view all the answers

Study Notes

Purpose and Types of Retaining Walls

Primary purpose of a retaining wall is to hold back soil and prevent erosion or structural failure.
Gravity retaining walls are economical for high walls due to their reliance on weight for stability.
Semigravity retaining walls use a combination of weight and engineering principles to resist lateral pressures.

Structural Components and Stability

Main structural component of a cantilever retaining wall is the stem, which transfers load from the wall to the base.
Counterfort retaining walls utilize counterforts or buttresses for added support and stability.
Gravity retaining walls are typically the most expensive to construct due to material and design complexities.

Forces and Pressure Theories

In the context of Rankine active pressure, angle h that line AC makes with the vertical varies depending on wall characteristics.
Coulomb's active earth pressure theory applies to various wall designs, emphasizing lateral pressure from soil.
Wall friction angle (δ') for masonry or mass concrete walls generally ranges from 0 to 30 degrees.

Assumptions and Structural Analysis

Assumptions for Rankine active pressure include uniform soil density and no wall friction along the height.
Counterfort slabs in a counterfort retaining wall should maintain a center-to-center spacing of approximately 1/2 to 1/3 the height (H) of the wall.
Stability checks for cantilever walls position point A at the base slab’s edge where loading conditions are assessed.

Safety Factors and Moments

Initial stability checks require a proportional relationship of the stem to the base slab, typically being thicker in counterfort walls.
Thickness of counterfort slabs generally falls between 12 inches to 18 inches.
Factor of safety against overturning is critical to ensure wall stability against rotation around the base.

Active and Passive Pressure Dynamics

Active earth pressure (Pa) calculations rely on specific forces acting upon the retaining wall.
Angle of internal friction (φ) is crucial for determining soil shear strength and is commonly set around 30 degrees.
Resisting moments are generated by gravity and stabilization forces during structural evaluations.

Analysis of Moments and Forces

Overturning moments depend on the resultant forces acting on the retaining wall, including soil and water pressures.
The force Pv contributes to the resisting moment and counters any tendency to tip the wall.
For simplified calculations, total resisting moment is determined by summing forces acting at distinct points along the wall.

These notes provide a condensed yet thorough overview of retaining wall principles, designs, and structural mechanics for effective study.

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Description

Learn about the general proportions and design considerations for counterfort retaining walls compared to cantilever walls. Explore the approximate dimensions of various components for initial stability checks.

Counterfort Retaining Walls in Chapter Three

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