### Pavement Design Problem#### Problem Statement:A flexible pavement has the following initial design specifications:- **Asphalt Wearing Surface:** 4 inches of sand-mix asphalt.- **Base Layer:** 6 inches of dense-graded crushed stone.- **Subbase Layer:** 8 inches of crushed stone.Additional parameters include:- **Drainage Coefficients (All Layers):** 1.0.- **Initial Present Serviceability Index (PSI):** 4.5.- **Terminal Serviceability Index (TSI):** 2.5.- **Soil Resilient Modulus:** 12,000 lb/in².- **Reliability:** 90%.- **Overall Standard Deviation:** 0.4.- **Design Life:** 15 years.During the design process, a mistake was identified: the design had ignored the impact of 100 daily passes of trucks with 22-kip single axles and 30-kip tandem axles. #### Engineering Question:Given these parameters and the identified design error, what should the thickness of the crushed stone subbase be? (Note: Avoid interpolating axle equivalency factors; use the closest available values).#### Explanation:The problem involves recalculating the necessary thickness of the subbase layer to properly support the pavement under the new loading conditions (increased truck load due to the previously ignored truck passes).This involves analyzing the equivalent single-axle load (ESAL) values and considering the increased load from the additional truck traffic. The result will determine the updated subbase thickness needed to maintain the design's integrity over the specified design life.

Thickness of sand-mix asphalt wearing surface = 4 inThickness of dense-graded crushed stone base = 6…

A flexible pavement is designed with 4 inches of sand-mix asphalt wearing surface, 6 inches of dense-graded crushed stone base, and 8 inches of crushed stone subbase. All drainage coefficients are 1.0. The initial PSI is 4.5, the TSI is 2.5, the soil resilient modulus is 12,000 lb/in², reliability is 90%, the overall standard deviation is 0.4, and the design life is 15 years. A design mistake was made that ignored 100 daily passes of trucks with 22-kip single and 30-kip tandem axles. What crushed stone subbase thickness should have been used? [Do not interpolate the axle equivalency factors, use the closest values]

A flexible pavement is designed with 4 inches of sand-mix asphalt wearing surface, 6 inches of dense-graded crushed stone base, and 8 inches of crushed stone subbase. All drainage coefficients are 1.0. The initial PSI is 4.5, the TSI is 2.5, the soil resilient modulus is 12,000 lb/in², reliability is 90%, the overall standard deviation is 0.4, and the design life is 15 years. A design mistake was made that ignored 100 daily passes of trucks with 22-kip single and 30-kip tandem axles. What crushed stone subbase thickness should have been used? [Do not interpolate the axle equivalency factors, use the closest values]

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Concept explainers

Design of pavements

Pavement is a structure that is made up of different layers such as sub-base course layer, base course layer, binder course, and a surface course formed with different materials such as gravel, above the subgrade soil constructed to act as a path or carriageway enabling the movement of vehicles. The surface of the pavement should possess characteristics such as adequate friction, light reflection, and drainage. The pavements are classified based on structural design into rigid pavements, flexible pavements, composite pavements, and unpaved pavements. The process of determining a suitable pavement type, its constituent layers, and its thickness is called pavement design.

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### Pavement Design Problem

#### Problem Statement:

A flexible pavement has the following initial design specifications:

- **Asphalt Wearing Surface:** 4 inches of sand-mix asphalt.
- **Base Layer:** 6 inches of dense-graded crushed stone.
- **Subbase Layer:** 8 inches of crushed stone.

Additional parameters include:
- **Drainage Coefficients (All Layers):** 1.0.
- **Initial Present Serviceability Index (PSI):** 4.5.
- **Terminal Serviceability Index (TSI):** 2.5.
- **Soil Resilient Modulus:** 12,000 lb/in².
- **Reliability:** 90%.
- **Overall Standard Deviation:** 0.4.
- **Design Life:** 15 years.

During the design process, a mistake was identified: the design had ignored the impact of 100 daily passes of trucks with 22-kip single axles and 30-kip tandem axles.

#### Engineering Question:

Given these parameters and the identified design error, what should the thickness of the crushed stone subbase be? (Note: Avoid interpolating axle equivalency factors; use the closest available values).

#### Explanation:

The problem involves recalculating the necessary thickness of the subbase layer to properly support the pavement under the new loading conditions (increased truck load due to the previously ignored truck passes).

This involves analyzing the equivalent single-axle load (ESAL) values and considering the increased load from the additional truck traffic. The result will determine the updated subbase thickness needed to maintain the design's integrity over the specified design life.

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Step 2: Structural number, SN

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Step 3: Calculation of ESAL

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Step 4: Ignored traffic calculations

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Step 5: Crushed stone sub-base thickness

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