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Chapter 3

Planning for Earthwork Construction

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Planning for Earthwork Construction

Every construction project is a unique undertaking. Therefore, planning is undertaken to understand the problems and to develop courses of action.

Planning Earthwork Construction

· · · · · Review the Contract Documents Study the plans Plan the Work Perform quantity take-off Determine costs

Planning Earthwork Construction

A site visit is strongly recommended to relate the physical site characteristics to the work details.

Planning Earthwork Construction

After the site visit is completed, the planner determines the quantity of materials that will have to be furnish or move. The takeoff or

"quantity survey."

Quantity Take-off

Must be as accurate as possible, and should be based on all

available engineering and design data.

Planning Earthwork Construction During the takeoff, the planner must make decisions concerning: ­ equipment needs ­ sequence of operations ­ and crew size

Graphical Presentation of Earthwork

Three kinds of views are presented in the contract documents to show earthwork construction features:

­ Plan view ­ Profile view ­ Cross section view

Plan View

The plan view is looking down on the proposed work and presents the horizontal alignment of features

Profile View

The profile view is a cut view typically along the centerline of the work. It presents the vertical alignment of features.

Cross Section View

A view formed by a plane cutting the work at a right angle to its long axis ­ When the ground surface is regular, sections are typically taken at every full station (100 ft) ­ When the ground is irregular, sections must be taken at closer intervals & at points of change

Earthwork Quantities

Earthwork computations involve:

· Calculation of earthwork volumes · Balancing of cuts and fills · Planning of the most economical material hauls.

End-Area Determination

Most organizations use commercial computer software and digitizing tablets to calculate cross section end areas. www.trimble.com/paydirt.html www.agtek.com/about.shtm

End-Area Determination

Other methods include the use of a planimeter, subdivision of the area into geometric figures with definite formulas for areas (rectangles, triangles, parallelograms and trapezoids), and the use of the trapezoidal formula.

Trapezoidal Computations

If the calculations must be made by hand, the area formula for a triangle and a trapezoid are used to compute the volume.

Area of a triangle = ½ hw

( h1 + h2 ) ×w Area of a trapezoid = 2

General Trapezoidal Formula

hn h0 Area = + h1 + h2 + ... + h( n -1 ) + × w 2 2

Average End Area Method

Volume [net cy] =

( A1 + A2 ) L × 2 27

Assumes that the ground between the two end areas changes in a linear fashion.

Average End Area

Average End Area

Average End Area

Net Volume

· Bank cubic yards (bcy) · Loose cubic yards (lcy) · Compacted cubic yards (ccy)

bcy

lcy

ccy

Mass Diagram

Earthmoving is basically an operation where material is removed from high spots and deposited in low spots with the "making up" of any deficit with borrow or the wasting of excess cut material.

Mass Diagram

The mass diagram is an excellent method of analyzing linear earthmoving operations. It is a graphical means for measuring haul distance (stations) in terms of earthwork volume (cubic yards).

Mass Diagram

Aids in identifying: · Where to utilize specific types of equipment, · Where quantities of material are required, · Average haul distance, · Haul grades.

Earthwork Volume Calculation Sheet

An earthwork volume sheet, can easily be constructed using a spreadsheet program. It permits a systematic recording of information and completing the necessary earthwork calculations

Earthwork Volume Calculation Sheet

Table 3.1, page 73

Stations. Column 1 is a listing of all stations at which cross-sectional areas have been recorded.

Area of cut. Column 2 is the crosssectional area of the cut at each station. Usually this area must be computed from the project cross sections.

Area of fill. Column 3 is the cross-sectional area of the fill at each station. Usually this area must be computed from the project cross sections. Note there can be both cut and fill at a station.

Volume of cut. Column 4 is the volume of cut between the adjacent preceding station and the station. This is a bank volume.

Volume of fill. Column 5 is the volume of fill between the adjacent preceding station and the station. The average-endarea formula, This is a compacted volume.

STRIPPING

For cut sections subtract the stripping.

STRIPPING

For fill sections the stripping is a cut quantity; plus an equal amount must be added to the embankment quantity.

Column 6 is the stripping volume of topsoil over the cut between the adjacent preceding station and the station. This represents a bank volume of cut material. Topsoil material is not suitable for use in the embankment.

Column 7 is the stripping volume of topsoil under the fill between the adjacent preceding station and the station. The stripping is a bank volume but it also represents an additional requirement for fill material, compacted volume of fill.

Column 8 is the total volume of cut material available for use in embankment construction. It is derived by subtracting the cut stripping (column 6) from the cut volume (column 4), both are bank volume quantities.

Column 9 is the total volume of fill required. It is derived by adding the fill stripping (column 7) to the fill volume (column 5), both are compacted volume quantities.

Column 10 is the total fill volume converted from compacted volume to bank volume

Column 11 is the difference between column 10 and column 8. This indicates the volume of material that is available (cut is positive) or required (fill is negative) within station increments after intrastation balancing.

Mass Ordinate

Column 12 is the running total of column 11 values from some point of beginning on the project profile.

MASS DIAGRAM PLOTTING

1000 500 0 - 500 - 1000

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

Horizontal scale (stations)

MASS DIAGRAM PLOTTING

1000 500 0 - 500 - 1000

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

STATION 0+50 - 138 CY

MASS DIAGRAM PLOTTING

1000 500 0 - 500 - 1000

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

STATION 1 +00 - 405 CY

MASS DIAGRAM PLOTTING

1000 500 0 - 500 - 1000

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

STATION 3 +50 518 CY

MASS DIAGRAM PLOTTING

1000 500 0 - 500 - 1000

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

CONNECT THE POINTS

MASS DIAGRAM

1000

500

Embankment requirements exceeds excavation quantity.

0

-500

- 1000

Descending lines

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

MASS DIAGRAM

1000 500

Ascending lines

0

-500

- 1000

Excavation exceeds embankment requirements

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

MASS DIAGRAM

1000 500

V O C L C U Y M E

CUT

FILL

0

-500 -1000

FILL

CUT

1+00

2+00

3+00

4+00

5+00

6+00

7+00

8+00

S TATIONS

MASS DIAGRAM

1000 500

Zero balance line

0 -500

- 1000

0 + 00

1 + 00

Excavation quantity equals embankment requirement. .

2 + 00 3 + 00 4 +00 5 + 00 6 + 00

MASS DIAGRAM

Maximum and minimum points

Maximum is where the cut transitions into fill. Minimum is where the fill transitions into cut.

MASS DIAGRAM

1000

Maximum and minimum points

500 0

-500

- 1000

Transition point

0 + 00 1 + 00 2 + 00 3 + 00 4 +00 5 + 00 6 + 00

MASS DIAGRAM

Final position

500 cy 0 0 1 2 3 4 5 6

410 cy waste

7

Stations

90 cy borrow

Above the zero line indicates waste. Below the zero line indicates borrow.

MASS DIAGRAM

Is a graphical means for measuring haul in terms of station yards. · Ascending lines?

· · · ·

Descending lines? Crossing the zero volume line? Max. and min. points? Final position?

Economical Haul Distances

Machine type Economical haul distance

Large dozers, Up to 300 ft pushing material Push-loaded scrapers 300 to 5,000 ft Trucks > than 5,000 ft

Mass Diagram With a Balance Line

Haul Distances

Page 81

Haul Distances

Average haul = area / quantity (cy)

Haul No. 3 quantity -17,080 Haul No. 1 quantity?

Haul Distance

0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+00 12+00 13+00 14+00 15+00 h0 h1 h2 h3 h4 h5 h6 h7 h8 h9 h10 h11 h12 h13 h14 h15 0 -3,631 -13,641 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -8,502 0 -3,631 -17,272 -30,721 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -25,582 -8,502 -1,816 -8,636 -15,361 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -12,791 -4,251

Haul Distance

213 ,654sta. - cy 17 ,080cy

0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+00 12+00 13+00 14+00 15+00

h0 h1 h2 h3 h4 h5 h6 h7 h8 h9 h10 h11 h12 h13 h14 h15

0 -3,631 -13,641 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -8,502 0

-3,631 -17,272 -30,721 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -34,160 -25,582 -8,502

Area under diagram Average haul No. 3 stations

-1,816 -8,636 -15,361 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -17,080 -12,791 -4,251 -213,654 12.51

Consolidated Average Hauls

Using the individual average hauls and the quantity associated with each, a project average haul can be calculated. Consider the three hauls and their sum of vertical's average haul distances. By multiplying each haul quantity by its respective haul distance a station-yard value can be determined.

Consolidated Average Hauls

Stations Haul 1 11,459 bcy 3+51 40,221 sta-cy Haul 2 5,590 bcy 3+35 18,727 sta-cy Haul 3 17,080 bcy 12+51 213,654 sta-cy 34,129 bcy 272,602 sta-cy 272,602 sta-cy = 8.0 stations 34,129 bcy

Consolidated Average Hauls Stations Haul 1 11,459 bcy 3+51 40,221 sta-cy Haul 2 5,590 bcy 3+35 18,727 sta-cy 17,049 bcy 58,948 sta-cy 58,948 sta-cy = 3.5 stations 17,049 bcy Haul 3 17,080 bcy 12.5 stations

Pricing Earthwork Operations

The cost of earthwork operations will vary with the kind of soil or rock encountered and the methods used to excavate, haul, and place the material in its final deposition.

Spreading Dumped Embankment Material with a Dozer

Water Truck and Roller used to Compaction Embankment Material

Three-link Earthwork System

Excavate & load Spread & compact

Haul, dump, return

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