leachate flow in leakage collection layers due to defects in ...

GIROUD et al. D Leachate Flow in Leakage Collection Layers Due to Geomembrane Defects
W
max
F
HG
tLCL
Q
= 1+
1
2
sinb
kt
LCL
L
I
+
KJ N
M
t
LCL
4 L sinb
F
HG
Q
1 +
2
kt
LCL
O
I
KJ
Q
P
12 /
(47)
4.2.5 Parametric Study
Widths of wetted zones calculated using equations given in Section 4.2 are presented
in Table 3. It appears that the width of the wetted zone increases for increasing rates of
flow through the geomembrane defect and for decreasing hydraulic conductivities and
slopes of the leakage collection layer.
4.3 Surface Area of the Wetted Zone
4.3.1 Expressions for the Surface Area of the Wetted Zone
The surface area of a parabola is given by the following equation:
A=( 23 / ) WX
(48)
Table 3. Width of the wetted zone at a 20 m horizontal distance from a defect in the
geomembrane primary liner for a 2% slope, W 20(2%) , and for a 1V:3H slope, W 20(1/3) .
Rate of flow
through the
geomembrane
defect
Geonet
t LCL =5mm
k =1× 10 -1 m/s
Leakage collection layer material
Gravel
t LCL = 300 mm
k =1× 10 -1 m/s
Sand
t LCL = 300 mm
k =1× 10 -3 m/s
10 lpd
(1.16 × 10 -7 m 3 /s)
Not full, t o
W 20(2%)
W 20(1/3)
= 1.1 mm
= 2.94 m
= 0.74 m
Not full, t o
W 20(2%)
W 20(1/3)
= 1.1 mm
= 2.94 m
= 0.74 m
Not full, t o
W 20(2%)
W 20(1/3)
= 11 mm
= 9.34 m
= 2.33 m
100 lpd
(1.16 × 10 -6 m 3 /s)
Not full, t o
W 20(2%)
W 20(1/3)
= 3.4 mm
= 5.23 m
= 1.31 m
Not full, t o
W 20(2%)
W 20(1/3)
= 3.4 mm
= 5.23 m
= 1.31 m
Not full, t o
W 20(2%)
W 20(1/3)
= 34 mm
= 16.84 m
= 4.15 m
1,000 lpd
(1.16 × 10 -5 m 3 /s)
Full,
W 20(2%)
W 20(1/3)
t o =14mm
= 10.70 m
= 2.67 m
Not full, t o
W 20(2%)
W 20(1/3)
= 11 mm
= 9.34 m
= 2.33 m
Not full, t o
W 20(2%)
W 20(1/3)
= 108 mm
= 31.24 m
= 7.41 m
10,000 lpd
(1.16 × 10 -4 m 3 /s)
Full,
W 20(2%)
W 20(1/3)
t o =118mm
= 32.94 m
= 7.77 m
Not full, t o
W 20(2%)
W 20(1/3)
= 34 mm
= 16.84 m
= 4.15 m
Full, t o = 343 mm
W 20(2%) = 62.28 m
= 13.29 m
W 20(1/3)
Notes: The values of t o were calculated using Equation 10 (when the leakage collection layer is not full) or
Equation 17 (when the leakage collection layer is full). Values of W 20 were calculated using Equation 36. They
could have been obtained using Equation 41 (when the leakage collection layer is not full) or Equation 45
(when the leakage collection layer is full). The leakage collection layer is full when t o > t LCL (Equation 13).
Units: lpd = liter per day = 1.16 × 10 -8 m 3 /s.
234 GEOSYNTHETICS INTERNATIONAL S 1997, VOL. 4, NOS. 3-4