1. Site Grading Site Grading Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Site Grading
Project Lead The Way, Inc.
Copyright 2010

2. TABLE OF CONTENTS Site Grading Creating a Profile
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
TABLE OF CONTENTS
Site Grading
Creating a Profile
Calculating Cut and Fill Volumes
Project Lead The Way, Inc.
Copyright 2010

3. Site Grading Construction requires preparation of the site
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Site Grading
Construction requires preparation of the site
Top soil removed and stored for later final grading
Cut and fill may be required
Cut – The removal of natural soil or rock
Fill – The addition of soil or rock
Final grading involves adjusting the slope of the site to provide adequate drainage
All structures are supported on the ground. Therefore the earth must be prepared so that it is capable of supporting the imposed loads.
The top soil is typically organic in nature and will not provide adequate support. It must be removed before a structure can be built. Once the top soil is removed, additional soil may need to be removed, or appropriate soil may need to be added to the site in order to provide an acceptable surface for construction. We refer to this subtracting and adding of soil as “cut and fill”.
After the structure is built and the pavement is placed, final grading involves replacing top soil in areas that will support plant life and adjusting the grade of the site to provide adequate drainage.
photo courtesy of constructionphotographs.com
Project Lead The Way, Inc.
Copyright 2010

4. Cut and Fill Cut and fill should be balanced
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Cut and Fill
Cut and fill should be balanced
May require several iterations
Because it is expensive to move soil and because purchasing soil can add significantly to the cost of a project, engineers often attempt to minimize the movement of soil and balance the volume of cut and fill. During the design process, the engineer may alter the site design in order to equalize the cut volume with the fill volume.
photo courtesy of constructionphotographs.com
photo courtesy of constructionphotographs.com
Project Lead The Way, Inc.
Copyright 2010

5. Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Site Grading
Calculations are performed to estimate the volume of soil to be added and the volume of soil to be removed
Profile views document the difference between the existing grade and the final grade
photo courtesy of constructionphotographs.com
Project Lead The Way, Inc.
Copyright 2010

6. Creating a Profile 104 100 96 Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Creating a Profile
To create a profile view, select the cutting plane line at which you would like a profile. [click]
Next project the elevation of each contour line to a grid [click] and indicate the elevation with a point. [click]
Only a few of the contour line elevations are projected here for illustration, but you should project the elevation of every contour line. [click]
Once you have plotted all of the elevation points, connect the points with a line. This is the grade line. In this case, it is an existing grade and is therefore shown as a dashed line. [click]
104
100 96
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Copyright 2010

7. Profile FINISH GRADE FILL CUT EXISTING GRADE 104 100 96 Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Profile
FINISH GRADE
FILL
CUT
104
As with contour lines on a site plan, the existing grade is shown with a dashed line. [click]
The proposed grade can be added to the profile and is typically shown with a solid line. [click]
The area between the proposed and existing grade lines represents material that must either be added (fill) or excavated (cut). [click]
In the profile shown here, fill is shaded blue and cut is shaded red.
Remember that this is a 2D view. The areas of cut and fill shown here have depth as well and represent a volume of soil. In practice, engineers try to balance the volume of cut with the volume of fill so that all of the material removed from an area can be reused as fill somewhere else on the site.
100 96
EXISTING GRADE
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Copyright 2010

8. Calculating Cut and Fill Volumes
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Calculating Cut and Fill Volumes
Let’s look at placing a 20 ft by 60 ft parking lot on the lot. Assume that the base course of gravel will extend down to an elevation of 100 ft.
Sketch the pavement in plan view. [click]
Create a profile through the center of the pavement area to be graded. [click]
Sketch the pavement at the appropriate elevation in the profile view. [click]
104
100 96
Project Lead The Way, Inc.
Copyright 2010

9. Calculating Cut and Fill Volumes
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Calculating Cut and Fill Volumes
Shade the areas of cut and fill. Note that when the pavement is constructed, there must be a gradual slope at the edge of the pavement [click] because the soil cannot hold a vertical slope. We will neglect this volume of soil for simplicity.[click]
Project Lead The Way, Inc.
Copyright 2010

10. Calculating Cut and Fill Volumes
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Calculating Cut and Fill Volumes A1 A2 A3 A4 A5 A6 B1 B2 B3 B4 B5 B6
Sketch a grid on the pavement area. We will use a 10 ft x 10 ft grid. [click]
Label each grid area so that you can refer to it later. [click]
Project Lead The Way, Inc.
Copyright 2010

11. Calculating Cut and Fill Volumes
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Calculating Cut and Fill Volumes
101'
98'
98'
99.5'
100.5'
100'
100'
Indicate the approximate elevation of each grid intersection on the plan view. [click]
For the existing grade elevation, take the average of the four corners of the grid area. For area A1, the average is 98 feet. Tabulate this data in a table (next slide).
98'
98'
99'
100.5'
102.5'
101'
100'
98'
98'
99'
100.5'
101'
101'
100'
Project Lead The Way, Inc.
Copyright 2010

12. Calculating Cut and Fill Volumes
Site Grading
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Calculating Cut and Fill Volumes
Create a table to record the existing grade and finish grade in each square area and the information necessary to calculate the volume of cut or fill. The difference between the existing grade and finish grade is either cut (if existing is greater than finished grade) or fill (if existing is less than finish grade).
For area A1, the average existing grade is at an elevation of 98 ft. [click]
The finished grade (under the pavement) is at an elevation of 100 ft. [click]
The difference is 2 feet. This must be added to bring the existing grade up to 100 feet.
Since the grid is 10 ft x 10 ft, the area is 100 sq. ft.
The fill volume, then, is 2 ft times 100 sq ft, or 200 sq ft.
Continue recording the average grade elevation and calculating the cut or fill volume for each area under the pavement.
When the cut or fill volume is calculated for all areas, total the cut volumes and the fill volumes. [click] [click]
Find the difference between cut volume and fill volume. In this case the contractor would have to purchase 180 cubic feet of soil to equalize the cut and fill.
At this point the engineer may decide to adjust the elevation of the pavement in order to bring the cut and fill volume closer together.
540 ft3
720 ft3
Project Lead The Way, Inc.
Copyright 2010

13. TABLE OF CONTENTS Site Grading Creating a Profile
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
TABLE OF CONTENTS
Site Grading
Creating a Profile
Calculating Cut and Fill Volumes
Project Lead The Way, Inc.
Copyright 2010

14. Site Grading Site Grading Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Site Grading
Project Lead The Way, Inc.
Copyright 2010