Hồ sơ xử lý nền đất yếu dự án Tân Vũ Lạch Huyện

project management unit NO.2
BAN QUảN Lý Dự áN 2
------------- o0o------------

JBIC Loan Agreement No.VNXII-3

LACH HUYEN PORT INFRASTRUCTURE CONSTRUCTION
PROJECT (ROAD AND BRIDGE PORTION)
D N XY DNG C S H TNG CNG LCH HUYN
(HP PHN NG V CU)
CONTRACT PACKAGE No.6: CONSTRUCTION OF KM0+000 - KM15+630
GểI THU S 6: XY LP ON T KM0 KM15+630

SHOP Drawing - BảN Vẽ THI CÔNG
Volume III: SOFT SOIL TREATMENT
Phần III: THIếT Kế Xử Lý NềN ĐấT YếU

Volume III.1: REPORT calculation FOR SOFT SOIL TREATMENT
Tập III.1: Hồ SƠ TíNH TOáN Xử Lý NềN ĐấT YếU
Volume III.1.3: Section km3+00 -:- km4+501
Tập III.1.3: ĐOạN km3+00 -:- km4+501
Rev 02 Chỉnh sửa lần 02.

Hai Phong, January 2015


project management unit NO.2
BAN QUảN Lý Dự áN 2
------------- o0o------------

JBIC Loan Agreement No.VNXII-3

LACH HUYEN PORT INFRASTRUCTURE CONSTRUCTION
PROJECT (ROAD AND BRIDGE PORTION)
D N XY DNG C S H TNG CNG LCH HUYN
(HP PHN NG V CU)
CONTRACT PACKAGE No.6: CONSTRUCTION OF KM0+000 - KM15+630
GểI THU S 6: XY LP ON T KM0 KM15+630

SHOP Drawing - BảN Vẽ THI CÔNG
Volume III: SOFT SOIL TREATMENT
Phần III: THIếT Kế Xử Lý NềN ĐấT YếU

Volume III.1: REPORT calculation FOR SOFT SOIL TREATMENT
Tập III.1: Hồ SƠ TíNH TOáN Xử Lý NềN ĐấT YếU
Volume III.1.3: Section km3+00 -:- km4+501
Tập III.1.3: ĐOạN km3+00 -:- km4+501
Rev 02 Chỉnh sửa lần 02.

STC.JV/
Liên danh nhà thầu

Hai Phong, January, 2015

APPROVED BY
CONSULTANT/
Tư vấn chấp thuận

TOTAL BLOCK LIST FOR SECTION SOFT SOIL TREATMENT
DANH SÁCH CÁC ĐOẠN XỬ LÝ
Block No.
Đoạn
EX10-16
HA-1
HA-2a
HA-2b
HA-3
HA-4
HA-5
HA-6a
HA-6b
HA-6c
HA-7
HA-7
HA-8
Cam River
Bridge
HA-9
HA-10
HA-10
HA-11a
HA-11b
HA-12
HA-13
HA-14
HA-15a
HA-15b
HA-16a

HA-16b
HA-17a
HA-17b
HA-17c
HA-18
HA-19
HA-20a
HA-20b1
HA-20b2
HA-20b2
HA-21

Sta- Lý Trình
From - Từ To - Tới
100+700
0+12.5
0+240
0+500
0+762
0+814
0+888
0+980
1+160
1+260
1+475

101+90
0+240
0+500
0+762

0+814
0+888
0+980
1+160
1+260
1+475
1+635.569

Length (m) Improvement
Dài (m)
Biện pháp xử lý
390
227
260
262
52
74
92
180
100
215
160.569

Longitude Abutment A1– Cam river Bridge

1+635.569

1+660.019

24.45

1+660.019

1+739.981

79.962

1+739.981
1+764.431

1+764.431
2+000

24.45
235.569

Longitude Abutment A2– Cam river Bridge

2+000
2+100
100
2+100
2+364
264
2+364
2+416
52
2+416
2+624
208

2+624
2+676
52
2+676
2+900
224
2+900
3+000
100
3+000
3+080
80
3+080
3+375
295
3+375
3+460
85
3+460
3+620
160
3+620
3+675
55
3+675
4+111
436
4+111
4+169
58

4+169
4+280
111
4+280
4+380
100
4+380
4+456
76
Longitude Abutment A1 - Main Bridge
4+456
4+497
41

PVD
PVD
PVD
PVD
PVD
PVD
SD
PVD
PVD
PVD
SD
SD
LRS

Note - Ghi chú

Volum III.1.1:
Section Tan Vu Interchange
Km0+00 - Km0+240 and
Section Km0+240Km0+635.569

Scope of Cam River Bridge

LRS
SD
SD
SD
SD
SD
SD
SD
SD
SD
PVD
PVD
PVD
PVD
PVD
SD
SD
SD
SCP
SCP
SCP
LRS

Volume III.1.2: Section
Km1+764.431 - Km3+00

Volume III.1.3: Section
Km3+00 - Km4+501

Scope of Pile Slab


Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Contents
Introduction………………………………………..…………………………..2
1. Design criteria............................................................................................... 3
1.1 Settlement and consolidation........................................................................... 3
1.2 Stability against sliding.................................................................................... 3
1.3 Traffic load....................................................................................................... 3

2. Calculation methodology ............................................................................. 5
2.1 Theory and calculation for vertical drain ....................................................... 5
2.2 Theory and calculation for sand compaction pile .......................................... 9
2.3 Calculation for Coarse Sand Blanket Thickness .......................................... 12
2.4 Software ......................................................................................................... 12

3. Design soil value ......................................................................................... 12
3.1 Unit weight ..................................................................................................... 12
3.2 Initial undrain shear strength ....................................................................... 14
3.3 Factor of increase of undrain shear strength ............................................... 17

3.4 Pre-consolidation condition and consolidation soil parameters .................. 18
3.5 Summary of soil value for soft soil treatment design ................................... 24

4. Soft soil treatment analysis ........................................................................ 24
4.1 Time for soft soil treatment ........................................................................... 24
4.2 Necessity of soft soil treatment countermeasure .......................................... 25
4.3 Applicable countermeasure for soft soil treatment ...................................... 25
4.4 Sectioning ....................................................................................................... 29
4.5 Result of soft soil treatment design ............................................................... 30

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Soft Soil Treatment Calculation Report for Tan Vu - Lach Huyen Port
Infrastructure Construction Project (Km0+00 - Km4+501)
INTRODUCTION
The Lach Huyen Port Infrastructure Construction Project – Road and Bridge Portion
with the length is approximately 15,63Km of total will connects Lach Huyen port in Cat Hai
island with the Ha Noi – Hai Phong expressway. The project will develop potentiality of Lach
Huyen gate port, speed up transportation of goods through the ports in Northern, meet the
growth of goods according to forecast by 2020 and the need of economical – social
development in this area, create comprehensive traffic system in conformity with detail plan
of sea port group in Northern area, which were approved by the Government.
The geological investigation for project consists of 3 sections are as follows:
- Geological investigation for approach road in the Hai An side (L = 4,50 Km);
- Geological investigation for bridge area (L = 5,44 Km);

- Geological investigation for approach road in the Cat Hai side (L = 5.69 Km).

Figure 1 - Study area of the Project
- The Contractors calculate only calculation for soft soil treatment approach road in
the Hai An side (Km0+00 - Km4+501, L=4.50 Km). In this report are shown calculations
section Km3+00 – Km4+501.
- Due to the difficulty of Land acquisition area. So in this line section the Contractor
may use total acess road go to in the main line (details are shown in the method statement of
Contractors).
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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

1. DESIGN CRITERIA
The following standards are applied for soft soil treatment design:
- Standard for Investigation and Design of Embankment on Soft Ground 22TCN262-2000.
- Highway - Specifications for Design TCVN4504-2005.
- Flexible pavement design 22TCN211-06 (refference only).
Pursuant to the above Standard, followings are criteria for soft soil treatment design:
1.1 Settlement and Consolidation
Soft ground shall be treated to satisfy following conditions:
- Residual settlement (Sr) is decided to be less than: 10cm for section behind bridge abutment
and box culvert (H>2.0m), 20cm for sections including small size culvert (H 2.0m) and 30 cm
for normal embankment section.
- Consolidation degree is not less than 90% or speed of residual settlement is less than 2cm
per year. Value of allowable settlement for each section is summarized in Table 1.1-1
Table 1.1-1 Allowable residual settlement after construction of pavement

Highway classification
1. Expressway and
highway class 80
2. Highway under class 60
with surfacing class A1

Embankment location on soft soil
At the place of culverts
At normal
Near abutment
or under public
embankment
highway
≤ 10 cm

≤ 20 cm

≤ 30 cm

≤ 20 cm

≤ 30 cm

≤ 40 cm

(Source: Item II.2.3 standards 22TCN262-2000)
Note: Allowable residual settlement is reduced into 10cm for box culvert section in this
project, although 20cm is recommended in the standard (see table 1.1-1). The reason why
10cm is applied is to minimize the risk of differential settlement because shallow foundation
is applied for box culvert foundation instead of pile foundation.

1.2 Stability against sliding
Following conditions shall be confirmed for stability against sliding:
- Factor of safety is not less than 1.2 in period of filling and waiting for consolidation, and
- Factor of safety is not less than 1.4 at the end of final period of waiting for consolidation.
1.3 Traffic load.
Traffic load is evaluated in accordance with 22TCN262-2000 from following equations:
q=

n´G
B´l

(1-1)

B = n ´ b + (n - 1) ´ d + e

(1-2)

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Where as (see Figure 1-1)
n: Number of vehicle,
G: Weight of vehicle (=30 ton in case of H30),
B: Width of traffic load (Max. 14.3m as designated, 1 side),
l: distance between front wheel and rear wheel (=6.6m, in case of H30),
b = 1.8 m, e = 0.5m, d = 1.3m

Results: B=11.6m, n=4, and q=1.57 t/m2 and will be distributed in the carriage ways as
sketched for calculation as figure 1-2.

e /2

b

d

b

e /2

B

l

Figure 1-1 Traffic load calculation diagram

W=29.5m
0.5m

1.0m

q=1.57 t/m 2

0.5m

q=1.57 t/m 2

Figure 1-2 Traffic load value and distribution

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

2. CALCULATION METHODOLOGY
2.1 Theory and Calculation for Vertical Drain
a)

Settlement

Due to variation of stress caused by embankment load by distribution depth of soil, a soil
layer will be divided into sub-layers thickness 1~2m for settlement and settlement of the soil
layer will be summed up from the settlement of the sub-layers.
It is possible to calculate consolidation settlement by using original formula as depicted below
(hereinafter referred to as De method):
Sc =

eo - e1
H
1 + e0

(2-1)

Or the following modified formulas (hereinafter referred to as Pc/Cc method):
Sc =

P + DP
Cc
H log 0
1 + e0
P0

For normal consolidation

(2-2)

Sc =

Cs
P + DP
H log o
1 + eo
Po

For over consolidation and Pc>P0+DP

(2-3)

Sc =

Cs
P
C
P + DP
H log c + c H log 0

1 + eo
P0 1 + e0
Pc

For overconsolidation and Pc
In the sand layer, the following formula can be used for immediately settlement (De Beer
method)
S i = 0.4

Po
P + DP
H log 0
N
Po

(2-5)

Where as:
Sc: Consolidation settlement,
Si: Immediately settlement of sandy soil layer,
eo: Void ratio at pressure of P 0 (Initial void ratio),
e1: Void ratio at pressure of P 0+DP,
P0: Overburden pressure,
DP: Pressure caused by embankment,
Cc: Compression index,
Cs: Swell index,
Pc: Pre-consolidation pressure,
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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

H: Soil thickness.
N: Standard penetration test value.
b)

Consolidation

In case of no vertical drain, time factor (Tv) will be calculated from formulas (2-6) as follow:
Tv =

t ´ Cv
H2

(2-6)

Then consolidation degree will be computed by Terzaghi Uv – Tv relationship as follow:

p æ U ö
Tv = ´ ç
÷
4 è 100 ø

2

Tv = 1.781 - 0.933 ´ log(100 - U )

in case 0
(2-7)

in case U>53%

(2-8)

Where as
t: Settlement time,
H: Drainage distance,
Tv: Time factor,
Uv: Consolidation degree,
Cv: Coefficient of Consolidation.
In case such vertical drain as PVD, sand drain, pack drain, etc. are installed for soft soil
treatment, consolidation degree will be evaluated from Carrillo expression:
U = 1 - (1 - U v ) * (1 - U h )

(2-9)

Where as:
U: Consolidation degree,
Uv: Vertical component of consolidation being computed as mentioned above,
Uh: Horizontal component of consolidation being computed from Hansbo
recommendations as follow:
æ - 8 ´ Th ö
U h = 1 - expç
÷
è F ø
Th =

(2-10)

C h .t
de

(2-11)

2

F = F (n) + Fs + Fr

(2-12)

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Soft Soil Treatment Calculation Report

F ( n) =

n=

Tan Vu - Lach Huyen Port Infrastructure Construction Project

n2
3n 2 - 1
ln
n
n2 -1

4n 2

(2-13)

de
dw

(2-14)

ö æd ö
æk
Fs = çç h - 1÷÷ lnçç s ÷÷
ø è dw ø
è ks
Fr = pz (2 L - z )

(2-15)

kh
qw

(2-16)

Where as:
Th: Time factor,
Ch: Horizontal consolidation coefficient,
de: Effective drainage distance (=1.13ds for square pattern, =1.05d s for triangular
pattern),
ds: Center to center spacing between vertical drain units,
dw: Diameter/equivalent diameter of vertical drain unit,

kh: Horizontal permeability,
ks: Permeability in smear zone,
ds: Diameter of smear zone in cross section,
L: Drainage length,
qw: Discharge capacity of vertical drain unit.
c)

Shear strength due to consolidation

Undrain shear strength of soft soil is considered to increase for an amount of DC due to
consolidation being evaluated as follow:
DC = (P0 - Pc + DP ) ´ U ´ m

(2-17)

Where as:
DC: Increased amount of undrain shear strength due to consolidation,
m: Index of increase of undrain shear strength.
d)

Sliding check

Bishop method as formulated below is recommended for sliding check.

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

1
å m [C ´ b + (w - u ´ b ) tan j ]
Fs =
å w sin a

(2-18)

tan j ö
æ
ma = cos a ç1 + tan a
÷
Fs ø
è

(2-19)

a

Where as (see figure 2-1):
C: Cohesion,
j: Internal friction angle,
b: Width of slice,
u: Pore water pressure acting at the slice base,
W: Weight of slice,

a : Slice base angle to the horizontal direction.

a

Figure 2-1 Sliding check model
In case reinforced geotextile is used, the resistance mobilized from the geotextile will be
computed as follow:

[

T = max Tbreak , T pullout

]

(2-20)

In which (see figure 2-2),
Tbreak =

Tensile
k

T pullout = b ´ t

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

2
é
ù

t = 2 ´ k '´êgh ´ tan (j) ú
3
ë
û
Tensile: Tensile Strength of geotextile (=200KN hoặc =400KN)
k: safety factor (=2 for polyester made geotextile as 22TCN262-2000 recommended)
k’: Reservation factor (=0.66 as 22TCN262-2000 recommended)

g, f
t

t

t

t

t

t

Figure 2-2 Resistant force mobilized from reinforced geotextile
2.2 Theory and Calculation for Sand Compaction Pile
a)

Overview

Sand Compaction Pile (SCP) method uses vibration load to penetrate a casing for making
sand compaction pile on soft soil. It shall contrive increase of bearing capacity, decrease of
consolidation settlement, increase of horizontal resistance, uniformity of ground,

consolidation drainage effect due to increase density of ground. This method is used almost
soil condition including sand soil, clay soil and organic soil.
b)

design
·

Replacement ratio

Replacement ratio is defined by the following expression and will be calculated for square
and triangular pattern as follow (figure 2-3):

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 2-3 Arrangement and design concept of SCP

Fv =

As As
=
A d2

in case of square pattern

(2-21)

Fv =

As
3 As
=
A
2 d2

in case of triangular pattern

(2-22)

Where,
As: Cross-sectional area of SCP
d: Center-to-Center spacing
·

Shear strength

Soft ground after being treated by SCP will be considered a composite ground comprising of
SCP and surrounding soft soil. Shear strength of the composite ground tSC is calculated as
follow:
τsc=(1-Fv)(Co+Cu/p• (Po-Pc+μc•sz)•U+ Fv • (gs'•Z+μs•sz)tanjs• (cosθ)²

(2-23)

τsc=(1- Fv)(Co+Cu/p• (Po-Pc+μc•sz )·U+(g'm•Z+sz )•μs •Fv •tanjs •(cosθ)²

(2-24)

Where,
mc: Reduction coefficient of stress,mc =

ms: Increase coefficient of stress,ms =

sc
1
=
s 1 + (n - 1) Fv

ss
n
=
s 1 + (n - 1) Fv

=2.5~3.5 typically, (3.0 in average).
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Soft Soil Treatment Calculation Report

n: Ratio of stress division, n =

Tan Vu - Lach Huyen Port Infrastructure Construction Project

ss
sc

Cu/p: Ratio of strength increase

gs': Sub water unit weight of sand
Z: Depth to the failure surface
js: Friction angle of sand
q: Angle between acting surface and horizontal surface
sz: Increased stress at failure surface due to embankment loading
s: Average stress
sc: Stress acting on surrounding soil
ss: Stress acting on SCP
γm' = Average sub water unit weight of composite soil
Friction angle of sand (of SCP) and ratio of stress division depending on replacement ratio is
shown in table 2-1 below:
Table 2-1 Friction angle and Ratio of stress division depending on replacement ratio
Replacement Ratio, Fv

Friction Angle of sand, js

Ratio of stress division, n

0 ~ 0.4

30

3

0.4 ~ 0.7

30

2

0.7 ~ 1

30~35

1

Cohesion and internal friction angle of the composite soil being used for slope stability
analysis are evaluated from following equation (2-25) and (2-26) respectively, which is
derived from equation (2-23).

j = tan -1 (m ´ tan js )

(2-25)

C=(1-Fv)(Co+Cu/p· (Po-Pc+μc·DP)·U

(2-26)

Where,
m= Fv×ms
Po : Effective overburden pressure
Pc : Preconsolidation pressure
DP: Embankment pressure

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Soft Soil Treatment Calculation Report

·

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Settlement

Settlement of the composite ground is less than non-treated ground because SCP shares load
acting upon the ground and, accordingly, SCP reduces stress acting upon soil. Following
equation is used to get settlement of the composite ground.
S=

Cc
æ Po + mc ´ DP ö
H logç
÷
1 + eo
Po
è
ø

For soil normal consolidation

(2-27)

Sc =

Cs
P + mc ´ DP
H log o
1 + eo
Po

Sc =

Cs
P
C
P + mc ´ DP
H log c + c H log 0
For soil over consolidation and Pc1 + eo
P0 1 + e0
Pc

For soil over consolidation and Pc>P0+DP (2-28)

2.3 Calculation for Coarse Sand Blanket Thickness
The thickness of CSB is estimated based on the ground water head caused by
embankment loading, which is calculated from the following equation:
L2 ´ S
Dh =
K ´h

(2-34)

In which:
Dh: Ground water head,
h: Thickness of CSB,
K: Permeability of CSB,
L: Horizontal drain length,
S: Settlement velocity.

In order to ensure the drainage capacity, the thickness of CSB tested gradually ensure
shall not be less than the above Dh value and 50cm.
2.4 Software
All calculation has been computed with assistance of software: K-Embankment for
calculation of settlement and consolidation, and Geoslope for sliding check.
3. DESIGN SOIL VALUE
Detail of the soil condition and soil properties are presented in the Soil Investigation Report.
The following paragraphs will only be of analysis of soil values for soft soil treatment.
3.1 Unit Weight
- Unit weight of sand embankment is taken in Bat Trang sand mining - An Lao - TP. Hai
Phong g=1.84t/m3. But the fact embankment including road surface structure is as follows:
Thickness and unit weight of materials for pavement:
+ Asphalt h =23cm; γ1 =2.4 T/m3
+ Macadam as pavement: h=0.81m, γ2 =2.25 T/m3
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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

+ Filling by sand K98 : h=0.3m;γ3 =1.9 T/m3
Calculated parameters of the road embankment materials:
+ Filling by sand:γd = 1.84T/m3; C=0, φ = 300
Embankment height calculations: He= Htk + Δh
In wich:
He: Embankment height calculations.
Htk: Height embankment design in final step.
Δh: Height differences due to the unit weight of pavement layers and embankment by sand.
γtd =

γ 1h1 * γ 2 h2 * γ 3 h3 2.4 * 0.23 * 2.25 * 0.81 *1.9 * 0.3
=
= 2.165
h1 + h2 + h3
0.23 + 0.81 + 0.3

Dh = (

γ td
2.165
- 1) * (h1 + h2 + h3) = (
- 1) * (0.23 + 0.81 + 0.3) = 0.25m
1.84
γd

- According to testing data, variation of unit weight (g) with depth of soil 3, 4, 6, 7b and 8 are
plotted in figure 3-1.

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-1 Variation of unit weight with depth
From the above figure, the following values will be recommended:
- Sand embankment: g=1.84t/m3
- Soil 3: g=1.69t/m3

- Soil 4: g=1.75t/m3
- Soil 6: g=1.85t/m3
- Soil 7B: g=1.74t/m3
- Soil 8: g=1.84t/m3
3.2 Initial Undrain Shear Strength
Initial undrain shear strength of soft soil (Co) will be evaluated from the following basis:
- Field vane shear test (FVST): in situ Co value will be directly estimated from FVST being
conducted during embankment boring (Boring),
- Triaxial test, UU-diagram (UU Test): Co value is also directly evaluated from this laboratory
UU test conducted on undisturbed samples,
- Unconfined Compression test (qu): following empirical relationship will be used to estimate
Co value from Unconfined Compression test qu
Co =

qu
(kg / cm 2)
2

(3-1)

Data range and Co typical value of these testing is shown in figures 3-2, 3-3, 3-4, 3-5 and 3-6.

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-2 Summary of Co value of soil 3 (kg/cm2) estimated from VST, qu/2 and UU test

Figure 3-3 Summary of Co (kg/cm2) value of soil 4 estimated from VST, qu/2 and UU test
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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-4 Summary of Co (kg/cm2) value of soil 6 estimated from VST, qu/2 and UU test

Figure 3-5 Summary of Co (kg/cm2) value of soil 7B estimated from VST, qu/2 and UU test
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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-6 Summary of Co (kg/cm2) value of soil 8 estimated from VST, qu/2 and UU test
As for soil 10A and 10B, which were detected as sand, sand with silt and/or clay (SC, SCSM) and will behave mostly like sandy soil, in which internal friction angle will be critical for
the soil strength and will be estimated from Dunham (1954) empirical relationship:

j = 12 ´ N + 15

(3-2)

Which: N: SPT value.
Accordingly, internal friction angles are respectively ofj=35o, and 40o will be recommended,
of which value of SPT is in the common range of 21 ~40.

3.3 Factor of Increase of Undrain Shear Strength
Undrain shear strength of soft soil will be increase due to consolidation with a factor called
“Factor of Increase of undrain shear strength” – m, which is basically evaluated from Triaxial
test, CU scheme – CU test and, as instructed in the Standard 22TCN262-2000, m equals to
tan(jcu).
The CU tests were conducted only for soft soil layer 3, 4, 6, 7B, 8 and m-values are plotted in
following figure 3-7.

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-7 values m from CU test and recommended value for design of soil 3, 6, 7B
Soil 4, 8 there is no experimental data Triaxial compression test (CU); m values were
calculated using the methods of the following experience:
m = 0.11+0.0037.PI
In that: PI is Plastic Index.
According to the above equation, the following m values were calculated and used to propose:
Soil
Ip (%)
m value
recommendations
4
13.20
0.25
8
19.12

0.30

3.4 Pre-Consolidation Condition and Consolidation Soil Parameters
Figure 3-8 plots all values of pre-consolidation pressure, stratigraphic effective pressure and
coefficient of over consolidation with depth of soil 3, 4, 6, 7B, 8.

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Soft Soil Treatment Calculation Report

Tan Vu - Lach Huyen Port Infrastructure Construction Project

Figure 3-8 Variation of Pc, Po with depth and stratigraphic pressure of soil 3, 4, 6, 7B, 8
The data show that almost all the deposit is over consolidated and the pre-consolidation
pressure of soil, except soil 8, will be evaluated from consolidation test as listed below:
- Soil 3: Pc=7.4 t/m2,
- Soil 4: Pc=13.9 t/m2,
- Soil 6: Pc=16.0 t/m2,
- Soil 7B: Pc=14.4 t/m2,
- Soil 8: Pc=19.6 t/m2.
As for soil 9, for which there is no consolidation test was conducted, pre-consolidation
pressure will be estimated from the relation m=Co/Pcà Pc=Co/m=19.60 t/m2.
Testing curves of compression, consolidation coefficient and permeability of soil 3, 4, 6, 7B, 8
from consolidation test is summarized in following figure 3-9 as well as typical values thereof,
which will be recommended for design.

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Soft Soil Treatment Calculation Report

0.000
1.379

0.000
1.230

0.250
1.262

0.250
1.123

0.500
1.201

e-p
1.000
1.115

0.500
1.067

e-p
1.000
1.011

2.000
1.006

2.000
0.948

Tan Vu - Lach Huyen Port Infrastructure Construction Project

4.000
0.884

4.000
0.868

8.000
0.754

8.000
0.750

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0.125
2.437

0.125
1.780

Cv*10E-3-p (cm2/s)
0.375 0.750 1.500 3.000
2.181 1.930 1.559 1.361

6.000
1.204

Cv*10E-3-p (cm2/s)
0.375 0.750 1.500 3.000
1.510 1.270 1.110 0.950

6.000
0.830