HomeMy WebLinkAboutMound Design Procedure E-20E-20
MOUND DESIGN T-20CEDURE (Continued)
(For Flows up tt 1200 gpd)
G.3. Calculate basal width ratio
by dividing rock layer
loading rate of '' .21 gpd/ft^
by allowable soil loading
rate;
1.20 gpd/ft2 1 g,j^gpd/ft2 = 2.0
Check this value on page E-16.
4. Multiply basal width ratio by
rock layer width to get
required basal width;
2.0 0 X 10 f t = t
H. Downslope Dike Width
1. If landslopc is 3% or more,
subtract rock layer width
froni basal width to obtain
nininum doOTslopo dike toe width
20 ft - 10 ft = /g> ft
2. Calculate mound height at edge
of rock layer on downslope side;
a. Determine depth of clean sand
fill at upslope edge of rock
layer: / feet
b. Multiply rock layer width by
landslopc to determine drop
in elevation;
/ X 3 7. 4 100 = 0.3 ft
c. Add drop in elevation to depth
of clean sand at upslope edge
of rock layer to get depth of
clean sand at downslope edge
of rock layer.
0,3 ft + / ft = /.3 ft
d. Add depth of clean sand at down-
slope edge to depth of rock
layer to depth of soil backfill
to get mound height at downslope
edge of rock layer;
A 3 ft +0.75 + A25ft = 9^3 ft
e. Enter table on page E-18 with
landslope and downslope dike
ratio. Select dike multiplier
of 3. 30
H.2.f. Multiply dike multiplier by
do\.mslopo mound height to get
downslope dike width;
3.20 X 2,3 = /o.7ft
g. Compare the values of step II. 1
and step H.2.f. Select the
greater of the two values as
the downslope dike width;
/«?. J feet
h. Calculate upslope dike width
using upslope mound height
and upslope dike multiplier
f,rom pa^-18; ^
i. Total mound width is the sum
of upslope dike width plus rock
layer width plus downslope dike
\7id th;
+ /O ft +/ojft Z9.2ft
3. If landslope is 2.9 percent or
loss, basal width includes both
the upslope and downslope dike
widths.
a. Calculate do:^islope dike width
using steps II.2.a. through
H.2.f; _ _ _ _ _ _^feet
b. Calculate upslope dike width
using upslope mound height and
dike multiplier from Page E-18;
_ _ X _ _ft = _ _ _ft
c. Add dovTnslope dike width to
upslope dike width to rock
layer width to get total mound
wid th;
_ _ft +_ _ft +_ _ft = _ _ft
d. Compare total mound width to
required basal width from step
G.4. If total mound width is
greater than required basal
width, use calculated dike
widths. If required basal
width is greater than total
mound width, increase downslope
dike width.