DESIGN OF SAND DRAINS FOR CONTAINER YARD.

Date : 01.05.2003
Project : Container Freight Stataion at Village Dutum, Dronagiri Node, Navi Mumbai.
Client : M/s Seabird Marine Services Private Limited.
Architect : Mr Sanjeev Mhatre.
Struct. Consultant : M/s Sahani & Associates.

Data / Information Available

Diameter of Drain d : 100 mm
Tentative Length of Drain, L : 14 m
Depth of Ground Water Table : 0 m Below EGL ( Assumed Conservatively )
Thickness of Granular Pad, t : 0.3 m above Drain for Drainage ( Varies )
Density of Granular Pad, g gran : 1.8 T/m3

From To Thickness of Design SPT Cu gsub

Stratum No. Description of Soil
m m Stratum (m) 'N' Value T/m2 T/m3
I Backfilled Soil 0 2.5 2.5 0.0 1
II Soft Clay 2.5 14.5 12 3 2.0 0.95

This data has been taken from Geotechnical investigation carried out by SEABIRD. It represent
the average ground conditions for the area of container Yard and is proposed to be supported
by stone columns

Value of Coefficient of
Consolidation has been Cv = 2.00 m2/year
used based on past
Ch/Cv = 10.0
experience.
Ch = 20.00 m2/year

It is possible to acieve strength gain using sand-drains.

Refer to Geotechnical investigation data, which gives
L.L. = 100
PL. = 40
PI = 60

Magnitude of strength gain can be computed by Skempton's Formula

Cu / Pc = 0.11 + 0.0037 PI
DCu /Pc = 0.332

This means strength gain by installing drains and preloading is of

the order of 0.332 times preloading intensity

Existing Preloading Intensity is 7.75 T/m2

Maximum Strength Gain = 2.6 T/m
- 2

Time for 90% Consolidation Without Treatment

Cv t
Tv =
d2
Cv = Coefficient of Consolidation = 2.00 m2/year
t = Time of Consolidation
d = Drainage Length = 6.00 m
Tv = Time Factor of Consolidation = 0.933
for Double Drainage
t = 16.79 years For U = 90%
This is too long time period even after considering favourable condition of double drainage.

To reduce the time required for 90% consolidation ground improvement technique such as
Sand Wicks / Sand Drains etc. will be needed.

1
Trial 1
Considering a typical design 75 mm diameter, calculation is carried out
Time for 90% consolidation
Using Sand Wicks of 75 mm dia installed at 2.10 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 2.1 m
let dw = diameter of drain = 75 mm
de = 2 re = 1.14 S m
de = 2.394 m

2.394
n = d e / dw =
0.075
n = 31.92
For U = 90% Ur 0.1
=
Uo 1

Degree of consolidation of three dimensional system

8T n

U r e F( n )
(
−
1 1
)
Uo
=
F (n)
2
log e n− +
2 2 n2
2
[ ]
n 3 n −1
F (n)= log e n−
For n = n 2−1
31.92 4 n2
F(n) = 2.7169
Ur 0.1 e -(8Tn/F(n)) x 2.9637
= =
Uo 2.717

e -(8Tn/F(n)) = 0.092
-(8Tn/F(n)) = -2.39
(8Tn/F(n)) = 2.39
=

Th = 0.812
C xt
Th = h 2
de
20.00 xt
Th =
5.731
t = 0.233 Year
t = 2.791 Months
t = 84.88 Days

For 50 percent consolidation time taken will be about 25 days

Therefore first drains will be installed and followed by stone column installation.
after about 20 days time.

2
 T
x / =
m
2

If preloading charge can be increased then the qa can be brought to desired value
Trial 2
Time for 90% consolidation
Using Sand Wic150 mmnstalled @ 2 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 150 mm
de = 2 r 1.14 S
= 1.14 x 2.1
de = 2.394 m
2.394
n = d e / dw =
0.15
n = 15.96
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n

Ur e
−
F( n )( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 15.96 n −1 4 n2
F(n) = 2.032
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 2.032
e -(8Tn/F(n)) = 0.089
-(8Tn/F(n)) = -2.414
(8Tn/F(n)) = 2.414
8 Tn
= 2.414
2.032
C xt
Th = ### = h 2
de
t = 0.176 yea
2.109 months 63.26 days
r= say 14 da
Trial 3 ys
Time for 90% consolidation
Using Sand Wic200 mmnstalled @ 2 m c/c in equilateral triangular grid

3
 Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 200 mm
de = 2 r 1.05 S
= 1.05 x 1.5
de = 1.575 m
1.575
n = d e / dw =
0.2

4
 n = 7.875
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n
−
U r e F( n )
( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 7.875 n −1 4 n2
F(n) = 1.352
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 1.352
e -(8Tn/F(n)) = 0.086
-(8Tn/F(n)) = -2.454
(8Tn/F(n)) = 2.454
8 Tn
= 2.454
1.352
C xt
Th = ### = h 2
de
t = 0.051 yea
0.617 months 18.51 days
r= say 12 da
ys

5
 DESIGN OF SAND DRAINS FOR CONTAINER YARD.
Date : 01.05.2003
Project : Container Freight Stataion at Village Dutum, Dronagiri Node, Navi Mumbai.
Client : M/s Seabird Marine Services Private Limited.
Architect : Mr Sanjeev Mhatre.
Struct. Consultant : M/s Sahani & Associates.

Data / Information Available

Diameter of Drain d : 75 mm
Tentative Length of Drain, L : 14 m
Depth of Ground Water Table : 0 m Below EGL ( Assumed Conservatively )
Thickness of Granular Pad, t : 0.3 m above Drain for Drainage ( Varies )
Density of Granular Pad, ggran : 1.8 T/m3

From To Thickness of Design SPT Cu gsub

Stratum No. Description of Soil
m m Stratum (m) 'N' Value T/m2 T/m3
I Backfilled Soil 0 2.5 2.5 0.0 1
II Soft Clay 2.5 14.5 12 3 2.0 0.95

This data has been taken from Geotechnical investigation carried out by SEABIRD. It represent
the average ground conditions for the area of container Yard and is proposed to be supported
by stone columns

Value of Coefficient of
Consolidation has been Cv = 2.00 m2/year
used based on past
Ch/Cv = 10.0
experience.
Ch = 20.00 m2/year

It is possible to acieve strength gain using sand-drains.

Refer to Geotechnical investigation data, which gives
L.L. = 100
PL. = 40
PI = 60

Magnitude of strength gain can be computed by Skempton's Formula

Cu / Pc = 0.11 + 0.0037 PI
DCu /Pc = 0.332

This means strength gain by installing drains and preloading is of

the order of 0.332 times preloading intensity

Existing Preloading Intensity is 4.75 T/m2

Maximum Strength Gain = 1.6 -T/m2

Time for 90% Consolidation Without Treatment

Cv t
Tv =
d2
Cv = Coefficient of Consolidation = 2.00 m2/year
t = Time of Consolidation
d = Drainage Length = 6.00 m
Tv = Time Factor of Consolidation = 0.933
for Double Drainage
t = 16.79 years For U = 90%
This is too long time period even after considering favourable condition of double drainage.

To reduce the time required for 90% consolidation ground improvement technique such as
Sand Wicks / Sand Drains etc. will be needed.

6
Trial 1
Considering a typical design 75 mm diameter, calculation is carried out
Time for 90% consolidation
Using Sand Wicks of 75 mm dia installed at 1.40 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.4 m
let dw = diameter of drain = 75 mm
de = 2 re = 1.14 S m
de = 1.596 m

1.596
n = d e / dw =
0.075
n = 21.28
For U = 90% Ur 0.1
=
Uo 1

Degree of consolidation of three dimensional system

8T n

U r e F( n )
(
−
1 1
)
Uo
=
F (n)
2
log e n− + 2
2 2n
2
[ ]
n 3 n −1
F (n)= log e n−
For n = n 2−1
21.28 4 n2
F(n) = 2.3151
Ur 0.1 e -(8Tn/F(n)) x 2.5589
= =
Uo 2.315

e -(8Tn/F(n)) = 0.09
-(8Tn/F(n)) = -2.403
(8Tn/F(n)) = 2.403
=

Th = 0.695
C xt
Th = h 2
de
20.00 xt
Th =
2.547
t = 0.089 Year
t = 1.063 Months
t = 32.32 Days

For 50 percent consolidation time taken will be about 10 days

Therefore first drains will be installed and followed by stone column installation.
after about 20 days time.

7
 T
x / =
m
2

If preloading charge can be increased then the qa can be brought to desired value
Trial 2
Time for 90% consolidation
Using Sand Wic150 mmnstalled @ 2 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 150 mm
de = 2 r 1.14 S
= 1.14 x 2.1
de = 2.394 m
2.394
n = d e / dw =
0.15
n = 15.96
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n

Ur e
−
F( n )( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 15.96 n −1 4 n2
F(n) = 2.032
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 2.032
e -(8Tn/F(n)) = 0.089
-(8Tn/F(n)) = -2.414
(8Tn/F(n)) = 2.414
8 Tn
= 2.414
2.032
Ch x t
Th = ### = 2
de
t = 0.176 yea
2.109 months 63.26 days
r= say 14 da
Trial 3 ys
Time for 90% consolidation
Using Sand Wic200 mmnstalled @ 2 m c/c in equilateral triangular grid

8
 Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 200 mm
de = 2 r 1.05 S
= 1.05 x 1.5
de = 1.575 m
1.575
n = d e / dw =
0.2

9
 n = 7.875
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n
−
U r e F( n )
( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 7.875 n −1 4 n2
F(n) = 1.352
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 1.352
e -(8Tn/F(n)) = 0.086
-(8Tn/F(n)) = -2.454
(8Tn/F(n)) = 2.454
8 Tn
= 2.454
1.352
Ch x t
Th = ### = 2
de
t = 0.051 yea
0.617 months 18.51 days
r= say 12 da
ys

10
 DESIGN OF SAND DRAINS FOR CONTAINER YARD.
Date : 01.05.2003
Project : Container Freight Stataion at Village Dutum, Dronagiri Node, Navi Mumbai.
Client : M/s Seabird Marine Services Private Limited.
Architect : Mr Sanjeev Mhatre.
Struct. Consultant : M/s Sahani & Associates.

Data / Information Available

Diameter of Drain d : 75 mm
Tentative Length of Drain, L : 14 m
Depth of Ground Water Table : 0 m Below EGL ( Assumed Conservatively )
Thickness of Granular Pad, t : 0.3 m above Drain for Drainage ( Varies )
Density of Granular Pad, ggran : 1.8 T/m3

From To Thickness of Design SPT Cu gsub

Stratum No. Description of Soil
m m Stratum (m) 'N' Value T/m2 T/m3
I Backfilled Soil 0 2.5 2.5 0.0 1
II Soft Clay 2.5 14.5 12 3 2.0 0.95

This data has been taken from Geotechnical investigation carried out by SEABIRD. It represent
the average ground conditions for the area of container Yard and is proposed to be supported
by stone columns

Value of Coefficient of
Consolidation has been Cv = 2.00 m2/year
used based on past
Ch/Cv = 10.0
experience.
Ch = 20.00 m2/year

It is possible to acieve strength gain using sand-drains.

Refer to Geotechnical investigation data, which gives
L.L. = 100
PL. = 40
PI = 60

Magnitude of strength gain can be computed by Skempton's Formula

Cu / Pc = 0.11 + 0.0037 PI
DCu /Pc = 0.332

This means strength gain by installing drains and preloading is of

the order of 0.332 times preloading intensity

Existing Preloading Intensity is 4.75 T/m2

Maximum Strength Gain = 1.6 -T/m2

Time for 90% Consolidation Without Treatment

Cv t
Tv =
d2
Cv = Coefficient of Consolidation = 2.00 m2/year
t = Time of Consolidation
d = Drainage Length = 6.00 m
Tv = Time Factor of Consolidation = 0.933
for Double Drainage
t = 16.79 years For U = 90%
This is too long time period even after considering favourable condition of double drainage.

To reduce the time required for 90% consolidation ground improvement technique such as
Sand Wicks / Sand Drains etc. will be needed.

11
Trial 1
Considering a typical design 75 mm diameter, calculation is carried out
Time for 90% consolidation
Using Sand Wicks of 75 mm dia installed at 1.50 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 75 mm
de = 2 re = 1.14 S m
de = 1.71 m

1.71
n = d e / dw =
0.075
n = 22.8
For U = 90% Ur 0.1
=
Uo 1

Degree of consolidation of three dimensional system

8T n

U r e F( n )
− ( 1 1
)
Uo
=
F (n)
2
log e n− + 2
2 2n
2
[ ]
n 3 n −1
F (n)= log e n−
For n = n 2−1
22.8 4 n2
F(n) = 2.3833
Ur 0.1 e -(8Tn/F(n)) x 2.6277
= =
Uo 2.383

e -(8Tn/F(n)) = 0.091
-(8Tn/F(n)) = -2.4
(8Tn/F(n)) = 2.4
=

Th = 0.715
C xt
Th = h 2
de
20.00 xt
Th =
2.924
t = 0.105 Year
t = 1.255 Months
t = 38.16 Days

12
 T
x / =
m
2

If preloading charge can be increased then the qa can be brought to desired value
Trial 2
Time for 90% consolidation
Using Sand Wic150 mmnstalled @ 2 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 150 mm
de = 2 r 1.14 S
= 1.14 x 2.1
de = 2.394 m
2.394
n = d e / dw =
0.15
n = 15.96
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n

Ur e
−
F( n )( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 15.96 n −1 4 n2
F(n) = 2.032
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 2.032
e -(8Tn/F(n)) = 0.089
-(8Tn/F(n)) = -2.414
(8Tn/F(n)) = 2.414
8 Tn
= 2.414
2.032
Ch x t
Th = ### = 2
de
t = 0.176 yea
2.109 months 63.26 days
r= say 14 da
Trial 3 ys
Time for 90% consolidation
Using Sand Wic200 mmnstalled @ 2 m c/c in equilateral triangular grid

13
 Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 200 mm
de = 2 r 1.05 S
= 1.05 x 1.5
de = 1.575 m
1.575
n = d e / dw =
0.2

14
 n = 7.875
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n
−
U r e F( n )
( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 7.875 n −1 4 n2
F(n) = 1.352
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 1.352
e -(8Tn/F(n)) = 0.086
-(8Tn/F(n)) = -2.454
(8Tn/F(n)) = 2.454
8 Tn
= 2.454
1.352
Ch x t
Th = ### = 2
de
t = 0.051 yea
0.617 months 18.51 days
r= say 12 da
ys

15
 DESIGN OF SAND DRAINS FOR CONTAINER YARD.
Date : 01.05.2003
Project : Container Freight Stataion at Village Dutum, Dronagiri Node, Navi Mumbai.
Client : M/s Seabird Marine Services Private Limited.
Architect : Mr Sanjeev Mhatre.
Struct. Consultant : M/s Sahani & Associates.

Data / Information Available

Diameter of Drain d : 75 mm
Tentative Length of Drain, L : 14 m
Depth of Ground Water Table : 0 m Below EGL ( Assumed Conservatively )
Thickness of Granular Pad, t : 0.3 m above Drain for Drainage ( Varies )
Density of Granular Pad, ggran : 1.8 T/m3

From To Thickness of Design SPT Cu gsub

Stratum No. Description of Soil
m m Stratum (m) 'N' Value T/m2 T/m3
I Backfilled Soil 0 2.5 2.5 0.0 1
II Soft Clay 2.5 14.5 12 3 2.0 0.95

This data has been taken from Geotechnical investigation carried out by SEABIRD. It represent
the average ground conditions for the area of container Yard and is proposed to be supported
by stone columns

Value of Coefficient of
Consolidation has been Cv = 2.00 m2/year
used based on past
Ch/Cv = 10.0
experience.
Ch = 20.00 m2/year

It is possible to acieve strength gain using sand-drains.

Refer to Geotechnical investigation data, which gives
L.L. = 100
PL. = 40
PI = 60

Magnitude of strength gain can be computed by Skempton's Formula

Cu / Pc = 0.11 + 0.0037 PI
DCu /Pc = 0.332

This means strength gain by installing drains and preloading is of

the order of 0.332 times preloading intensity

Existing Preloading Intensity is 4.75 T/m2

Maximum Strength Gain = 1.6 -T/m2

Time for 90% Consolidation Without Treatment

Cv t
Tv =
d2
Cv = Coefficient of Consolidation = 2.00 m2/year
t = Time of Consolidation
d = Drainage Length = 6.00 m
Tv = Time Factor of Consolidation = 0.933
for Double Drainage
t = 16.79 years For U = 90%
This is too long time period even after considering favourable condition of double drainage.

To reduce the time required for 90% consolidation ground improvement technique such as
Sand Wicks / Sand Drains etc. will be needed.

16
Trial 1
Considering a typical design 75 mm diameter, calculation is carried out
Time for 90% consolidation
Using Sand Wicks of 75 mm dia installed at 1.80 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.8 m
let dw = diameter of drain = 75 mm
de = 2 re = 1.14 S m
de = 2.052 m

2.052
n = d e / dw =
0.075
n = 27.36
For U = 90% Ur 0.1
=
Uo 1

Degree of consolidation of three dimensional system

8T n

U r e F( n )
− ( 1 1
)
Uo
=
F (n)
2
log e n− + 2
2 2n
2
[ ]
n 3 n −1
F (n)= log e n−
For n = n 2−1
27.36 4 n2
F(n) = 2.5638
Ur 0.1 e -(8Tn/F(n)) x 2.8098
= =
Uo 2.564

e -(8Tn/F(n)) = 0.091
-(8Tn/F(n)) = -2.394
(8Tn/F(n)) = 2.394
=

Th = 0.767
C xt
Th = h 2
de
20.00 xt
Th =
4.211
t = 0.162 Year
t = 1.938 Months
t = 58.96 Days

17
 T
x / =
m
2

If preloading charge can be increased then the qa can be brought to desired value
Trial 2
Time for 90% consolidation
Using Sand Wic150 mmnstalled @ 2 m c/c in equilateral triangular grid
Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 150 mm
de = 2 r 1.14 S
= 1.14 x 2.1
de = 2.394 m
2.394
n = d e / dw =
0.15
n = 15.96
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n

Ur e
−
F( n )( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 15.96 n −1 4 n2
F(n) = 2.032
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 2.032
e -(8Tn/F(n)) = 0.089
-(8Tn/F(n)) = -2.414
(8Tn/F(n)) = 2.414
8 Tn
= 2.414
2.032
Ch x t
Th = ### = 2
de
t = 0.176 yea
2.109 months 63.26 days
r= say 14 da
Trial 3 ys
Time for 90% consolidation
Using Sand Wic200 mmnstalled @ 2 m c/c in equilateral triangular grid

18
 Cv = 2.00 m2/ year
Ch = 20.00 m2/ year
d = 12.00 m
S = Spacing = 1.5 m
let dw = diameter of drain = 200 mm
de = 2 r 1.05 S
= 1.05 x 1.5
de = 1.575 m
1.575
n = d e / dw =
0.2

19
 n = 7.875
For U = 90% Ur 0.1
= 0.1
Uo 1
Degree of consolidation of three dimensional system
8T n
−
U r e F( n )
( ) 1 1
Uo
=
F (n)
2
[ log e n− + 2
2 2n
2
]
n 3 n −1
F (n)= 2
log e n−
For n 7.875 n −1 4 n2
F(n) = 1.352
Ur e -(8Tn/F(n)) ###
0.1 x
Uo 1.352
e -(8Tn/F(n)) = 0.086
-(8Tn/F(n)) = -2.454
(8Tn/F(n)) = 2.454
8 Tn
= 2.454
1.352
Ch x t
Th = ### = 2
de
t = 0.051 yea
0.617 months 18.51 days
r= say 12 da
ys

20