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

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

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

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

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

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 Project Lead The Way, Inc. Copyright 2010

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 Project Lead The Way, Inc. Copyright 2010

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

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

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

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

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

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

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