Civil Pp12

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CHAPTER 12

Earthwork

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Civil Drafting Technology, 7thedition

Madsen, Shumaker, and Madsen

2010 Pearson Higher Education,

Upper Saddle River, NJ 07458. All Rights Reserved.2

Earthwork

Earthwork cutting (excavating) and filling areasof earth.

Cut removing earth from hillsides and high

spots. Fill adding earth to valleys and low spots. Borrow pit a cut that provides fill material. Cut from areas of higher elevation, fill areas of

lower elevation.

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Why Layout Earthwork?

Determine how much material will be cut and

filled during a construction project.

Calculate construction costs: Building sites.

Fill material may need to be purchased.

Determine the proper amount of land to purchase for

roadway right-of-way. Analyze environmental impact.

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Level Road Cut-and-Fill Layout:

Traditional Method

1. Layout the proposed road plan view.

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Traditional Method

2. Determine the desired road elevation.

3. Identify the angle of repose: The slope of the cut and fill from the road. A ratio of run to rise.

For example, a 2:1 angle of repose means that for every 2 ofhorizontal distance, the slope rises or drops 1 vertically.

Determined based on the type of earth. Can be different angles for cut and fill.

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Traditional Method

4. Generate the cut and fill layout. Use the angle of repose and contour lines to show

which areas are cut, and which areas are filled.

Cross-section method shown in Figure 12-1b and

Figure 12-1c

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Level Road Cut-and-Fill Layout

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Level Road Cut-and-Fill Layout: CADD

(AutoCAD)

1. Open the highway layout plan drawing.

2. Identify the angle of repose for the fill and cut areas.Example: both cut and fill have an angle of repose of2:1

3. Identify the contour interval. Example: 104. Multiply the angle of repose by the contour interval.

Example: 2 1 = 2 so 2 X 10 = 20

5. Use the distances calculated during step 4 to offset

both edges of the road, away from the centerlineseveral times. Example: offset distance is 20

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Level Road Cut-and-Fill Layout: CADD

(AutoCAD)

6. Plot the outline of the cut and fill using a

spline. Spline points are located at the intersection of

contour lines, and the offset construction lines. The selected points represent locations of equal

elevation.

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Inclined Road Cut-and-Fill Layout1. Layout the proposed road plan view.

2. Generate a profile view. Project the intersections of each contour line, and the road centerline from the

plan view, to the profile.

3. Identify the angle of repose. Example: 2:1

4. At a vertical projection line, subtract the elevation of the proposed roadfrom the elevation of the existing slope, and multiply the number by theangle of repose. Example: 185 - 180 = 5 so 5 X 2 = 10

5. Use the value determined in step 4 to identify the distance from verticalconstruction line, and the contour line. Example: 10 from the verticalconstruction line, along the 185 contour line identifies a cut and fill

outline point.6. Repeat steps 4 and 5 to define each point along the cut and fill outline.

7. Connect the points with a spline.

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Inclined Road Cut-and-Fill Layout

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Cross Sections

Display cut and fill characteristics

perpendicular to the road centerline.

Sectioned side view.

Provide measurements that can be used for

calculating the amounts of earth to be removed

from hills and filled into areas below the road

grade.

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Cross Sections

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Cross Sections with a CADD System

Demonstrate using a specialized CADD system

to generate cross sections.

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Site Plan Cut-and-Fill Layout

1. Layout the site plan view.

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2. Identify the angle of repose (the slope of the cutand fill from each of the site boundary lines).Example: Cut angle of repose = 2:1 Fill angle of repose = 1:1

3. Identify the contour interval. Example: 2

4. Multiply the angle of repose by the contour

interval. Example: Cut: 2 1 = 2 so 2 X 2 = 4 Fill: 11 = 1.5 so 1.5 X 2 = 3

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5. Use the cut distancescalculated during step 4to offset all of the siteedges, away from the site

boundary several times.Example: cut offsetdistance is 4 fill offsetdistance is 3

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6. Plot the outline of the cut and fill using a spline. Spline points are located at the intersection of contour

lines, and the offset construction lines.

The selected points represent locations of equalelevation. Areas above the desired level elevation are cut, and

areas below the desired level are filled.

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Site Plan Cut-and-Fill with a CADD System

Demonstrate using a specialized CADD system

to generate site plan grading and contour lines.

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Earthwork Calculations

Calculating how much earth must be cut and/or

filled for a specific project.

Allows for cost approximations and better

layout design.

Primary concern is to predict drainage

requirements.

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Hydrologic study type of soils and ground

cover present, how water flows on the site, how

much water is absorbed, and the volume and

direction of water leaving the site. Borrow pit an area from which quantities of

earth is excavated to construct embankments

and fills.

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Study the figures and follow the informationpresented in the Earthwork Calculations sectionof Chapter 12 to better understand how to estimate

barrow pit quantities, and other earth workvolumes. Specialized CADD programs and application

software can contain enough data for calculating

earthwork volumes.

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