290
Coastal Engineering: Theory and Practice
Solution
Part a
Water table
Ai
Sand
c' =0
Dredge line
.
• A- :
l4
A3
D
A4 v
Sand
e' = 0
Calculating coefficient of earth pressure
Ka = tan2(45 - 32/2) = 0.307
Kp = tan2 (45 + 32/2) = 3.25
Calculation of active pressure
Active pressure above the water table (cr^) = ^dryffiKa
= (15.9)(2)(0.307) = 9.763 kN/m2
Active pressure above the dredge line (cr^) = ffidryL^ +
= [(15.9)(2) + (19.33 - 9.81)(3)(0.307)] = 18.53 kN/m2
In order to find the total pressure (P), L3 need to be calculated,
T
ct2
18-53
_
L3 = —--------------=--------------------------------------= 0.66 m.
'Y(Kp-Ka)
(19.33- 9.81)(3.25 -0.307)
Total pressure P = criL2 + |( 2
= 9.763 + 29.289 + 13.151 + 6.115 = 58.32 kN/m