earthwork

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HIGHWAY ENGINEERING

EARTHWORKS, CROSS-SECTIONS

AND MASS HAUL DIAGRAMS

OBJECTIVES

• ROUTE SELECTION – Estimation of cut and fill locations and quantities in order to approximately balance these values as a basis for selecting alternative routes and making preliminary costs.

• CONSTRUCTION – preparation of detailed earthwork quantities to establish economical haul distances, acquire borrow pit and disposal areas and to conduct cost and tender estimates.

a pit created to provide

earth that can be used as

fill at another site

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PRESENTATION OUTLINE

• Earthworks and Preliminary Route Selection

• Earthwork Analysis

• Cross-sections types

• Estimating volumes

• Shrinkage

• Location of cross-sections

• Earthworks tabulations

• Mass-Haul Diagrams

Earthworks and Preliminary Route Selection

Base mapping

Horizontal alignments

Vertical alignment (profile or longitudinal section)

Controls and constraints

Evaluation

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Earthworks and Preliminary Route Selection

Plan View

Profile View

Earthwork Analysis

Take cross sections (typically 50 - 200 m)

Plot natural ground level

Plot proposed grade profile

Indicate areas of cut and fill

Calculate volume between cross sections

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Cross-Sections Types

Cross-Section Area

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Cross-Section Area Example

= 53.68 + 45.88 + 131.57 + 19.47 – 16.00 – 45.70 = 188.90

Cross-Section Area

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Estimating Volumes

Average End Area Method

The area between the existing ground and proposed ground is calculated at each cross section.

The area between two consecutive cross sections is averaged.

This area is multiplied by the distance between two cross sections.

Estimating Volumes

Where:V = volume (m3)A1, A2 and A3 = area of end sections (m2)L = length between end sections (m)

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Shrinkage

Material volume increases during excavation (presence of air voids)

Volume decreases during compaction

This difference is defined as 'shrinkage'

Varies with

o soil type

o fill height

o cut depth

Location of Cross Sections

Sufficient to adequately estimate the earthworks

Hilly, undulating terrain requires more than flat terrain

Usually minimum of 20 m in rolling terrain (interval)

Possibly 100 to 200 m in flat terrain (interval)

Most highway departments have standardized intervals

More frequent spacing may be required at specific locations –e.g: at end and near bridges, culverts, etc.

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Mass Haul Computation

Usually in a tabular format with the following columns :

Station or distance Area of cross section • Excavation (cut) • Embankment (fill)

Average cross section area• Excavation• Embankment

Volume• Excavation• Embankment

Excess (+ for embankment, - for excavation) Mass Haul Ordinate

* cross-sections interval shall be within 15 m to 30 m, especially in the mountainous and hilly terrain areas.

Sample of cross section – cut area

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Sample of calculation

Shrinkage : 10%

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Stn/ Dist.

A REA(sq. m)

Shrinkage Average Area(sq. m)

Volume(cu. m)

EXCESS (EXC/EMB)

MassCurve

OrdinateEXC EMB EMB+10% EXC EMB EXC EMB

6 10 0

150 5 40

300 156 0

450 5 140

600 5 14

750 5 45

900 72 0

Stn/ Dist.

A REA(sq. m)

Shrinkage Average Area(sq. m)

Volume(cu. m)

EXCESS (EXC/EMB)

MassCurve

OrdinateEXC EMB EMB+10% EXC EMB EXC EMB

1050 107 0

1200 5 14

1350 5 34

1500 5 43

1650 5 40

1794 11 0

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Mass-Haul Ordinate