Earthwork Introduction

1
Earthwork Introduction

• Definition of earthwork
• Goal

2
Introduction (contd)

• Application

3
Earthwork Process

• Issue
• Example

4
Terminology

• Excavation or cut
• Embankment or fill
• Borrow
• Waste

5
Terminology

• Earthwork units
• English
• Cubic feet, cubic yards, acre-feet
• Metric
• Cubic meters

6
Stages of Earthwork Design

• Earthwork generally includes
• Earthwork is followed by

7
Computing Volumes

• Issue
• Alternative methods for computing volumes
• Focus in ERE 371

8
Preliminary Study and Cross-section

• Locate preliminary zone in project direction
• Defining surface

9
Cross-sections on Trial Route Line
Plan view
10
Cross-sections

• Purpose
• Source
• Designing

11
Designing Alternatives
Proposed road
b
s
s
Existing terrain
Alternative A
Alternative B
12
Computing Volumes

• Estimate volume
• Two common approaches
• Average end areas method
• Prismoidal formula

13
Computing Volumes
Average end areas V ½ (A0 A1)L

• Where
• A0, A1 end cross-section areas
• L distance between cross-sections

Example A0 421.6 ft2 A1 392.3 ft2 L 100
ft V ½ (421.6 ft2 392.3 ft2)(100 ft) 40695
ft3 1507 yd3
14
Computing Volumes
A1
M
A0
L

• Where
• A0, A1 cross-section areas
• M area of middle section
• L distance between cross-sections

Prismoidal V L/6 (A0 4M A1)
15
Calculating End Areas

• Issue
• Approaches

16
Mass Distribution Analysis

• Analyze designs to select most economical
• Design must meet project requirements
• Estimate economical way to distribute mass
• Accomplished using mass diagrams

17
Mass Diagrams

• Definition
• Mass diagrams

18
Mass Diagrams
Profile
Grade points
Grade line
Stations
Elevation
Mass diagram
Volume
Stations
19
Mass Diagrams
Cut areas
Fill areas
Indicate grade points
Indicate points where ? cuts ? fills
Ground
Profile
Grade
Elevation
Mass diagram
Volume
20
Properties of Mass Diagrams

• On mass diagram
• Profile and mass diagram plotted for each design

21
Mass Diagrams
Fill areas
Cut areas
Any horizontal line on mass diagram is a balance
line within balance line cut fill
Profile
Elevation
Mass diagram
Volume
22
Mass Distribution Analysis

• Compare mass diagrams to select design
• Ideal
• However

23
Mass Distribution Analysis cont.

• More terminology
• Haul
• Free Haul
• Free Haul Distance
• Overhaul
• Optimal condition

24
Economic (Cost-based) Approach

• Issue
• Limit of Profitable Haul (LPH)
• Balance lines should never exceed LPH

25
Mass Diagrams
Profile
Grade line
Elevation
Mass diagram
Free Haul
LPH
LPH
Free Haul
Volume
26
Limit of Profitable Haul

• LPH depends on factors such as

27
Final Analysis and Design

• Confounding factors
• Final stages

28
Readings

• Chapter 26 sections 26.1 26.9, 26.13 26.14