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Back-Fill Calculations
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CALCULATING BACK-FILL FOR A SLOPE (REQUIRES KNOWN PERCENT GRADE)
Example: A retaining wall is being constructed at the base of a hillside that a path is being built along.
The length of wall is to be 50 Feet and the height will be 4 Feet 6 Inches. You need to fill in the space
up to 2 Inches from the top of the wall. The percent grade of the hill is 60% How much fill do you need?
This can be solved for by treating the fill space like a right triangle equation.
4' 6"
KEY INPUT & DISPLAY
1. Solve for the Rise of the triangular space.
On/C
On/C
4
6
Feet
Inch
2. Find the Run of the triangular space that the fill will occupy.
0
6
%
Pitch
4
4
Feet
Inch
Run
3. Find volume of fill required as if it was a rectangular space:
5
0
Feet
×
Rcl
Run
×
4
4
Feet
3. Divide in half to find volume of a right trianlge space:
÷
=
2
to clear entries in between problems.
On/C
On/C
2"
(?) Rise
=
–
2
Inch
Rise
Inch
(?) Run
60%
Grade
Page 32
0
4
4
Feet
Inch
%GRD 60
RISE 4
4
Feet
Inch
RUN 7
2-11/16
Feet
Inch
50
Feet
RUN 5
0
Feet
Inch
1564.815
CU Feet
782.4074
CU Feet
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