Noi Bai International Airport to Nhat Tan Bridge Connecting Road Construction Project
Stage: Working drawing Package 2: Km1+539.48 -:- Km3+943.00
Conten ts
1. Introduction
2. Legal basic for implementation
3. Standard used
4. Highway raute composition of geological layers and condition
5. Design criteria
6. Calculation methodology
7. Summary of Soil Value for Soft Soil Treatment Design
8. Soft soil treatment analysis
9. Result of soft soil treatment embankment
1. Introduction 2
5.1 Settleme n t and C on solida t ion . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2 S tabilit y again st sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3 T raffic lo ad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Calculation methodology 7
6.1 T h eory a n d Calcu lation fo r Vertical Drai n . . . . . . . . . . . . 7
6.2 S oftware . . . . . . . . . . . . . . . . . . . . . . . 11
1
Noi Bai International Airport to Nhat Tan Bridge Connecting Road Construction Project
Stage: Working drawing Package 2: Km1+539.48 -:- Km3+943.00
Noi Ba i internat ional a irport to Nhat T an brid ge
connect ing ro a d const ruction p roject
S t a g e : w or k i n g d r a w i n g s
PACKA G E 2: Km 1+539.4 8 -:- K m3+943.0 0
Report on sof t so il treat ment
1. Introduction
Nhat Tan Bridge to Noi Bai Airport connecting road construction project is priority
project, which was received interests of Government, Ministry of Transport and Ha
Noi people’s Committee. Starting point of the project is intersection between approach

- Pursuant to the Government Decree No. 99/2007/NĐ-CP dated 13 June, 2007 on
managing investment for construction of work;
- Pursuant to the Government Decree No. 78/2007/NĐ-CP dated 11/05/2007 on
Investment of Building - Operation - Transfer; Building - Transfer - Operation;
Building - Transfer;
- Pursuant to the Government Decree No. 162/2002/QĐ-TTg dated 15/11/2004 of
Prime Ministry on validation of Viet Nam Highway Traffic development and planning
updating to 2010 and direction to 2020;
- Pursuant to the Government Decree No. 206/2004 QĐ-TTg dated 10/12/2004 of
Prime Ministry on validation of development strategy for Transport updating to 2020;
- Pursuant to the decision of Ministry of Transport No. 252/QĐ-BGTVT dated
25/01/2008 on Feasibility study for Nhat Tan bridge to Noi Bai Airport connecting
road construction project;
- Pursuant to the decision of Ministry of Transport No.3996/QĐ-BGTVT dated
31/12/2008 on validation of investment in construction of Nhat Tan bridge to Noi Bai
Airport connecting road construction project - Sub-project1(Km00+000) to
(Km7+850);
- Geological survey method for shop drawings consultation has been approved by letter
SC-CTI/K-0020A, dated 13 june 2012.
- Project's survey techniques request.
3
Noi Bai International Airport to Nhat Tan Bridge Connecting Road Construction Project
Stage: Working drawing Package 2: Km1+539.48 -:- Km3+943.00
3. Standard used
No Standards/Procedure Code/date Remarks
1 Exploratory boring procedure 22TCN259-2000 Viet Nam
2 Term of reference for soft soil investigation for
prepering of shop drawing of the package 1A
3 Specification for survey and design of highway
embankment on soft ground are

4.6. Sub - layer 8a: Brownish grey, greenish grey, Medium stiff - stiff, Clay.
It was encountered in BSDY1, BSDY2, and BSTC1 (working drawing) holes with the
top elevation is from -13.031m to -9.13m and from 1.20m to 7.60m of thickness. The
N value of SPT varies from 7 to 14.
Convention bearing capacity R < 1.00 kG/cm
2
4.7. Sub - layer 11b: Whitest grey, very dense, Coarse sand with gravel.
It was encountered in BSTC1 (working drawing) holes with the top elevation is
-16.73m and 0.50m of thickness. The N value of SPT is 51.
Convention bearing capacity R = 4.50 kG/cm
2
(under the table standards 22TCN260-
2000).
4.8. Layer 12: Whitest grey, yellowish grey, Very dense, Gravel.
This layer was encountered in BSTC1 holes.The elevation of layer top is -17.23m, the
thickness of layer was not defined yet, the maximum thickness, which was drilled into
layer is 4.60m (BSTC1). The N value of SPT is more than 50.
Convention bearing capacity R = 8.00 kG/cm
2
(under the table standards 22TCN260-
2000).
5. Design criteria
The following standards shall be recommended to apply for soft soil treatment design:
- Standard for Investigation and Design of Embankment on Soft Ground 22TCN262-
2000,
- Expressway – Requirement for Design TCVN5729-1997.
Pursuant to the above Standard, followings are criteria for soft soil treatment design:
5.1 Settlement and Consolidation
Soft ground shall be treated to ensure both conditions as depicted below (22TCN262-2000-
II.2.3):

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: q=1.59 t/m
2
and will be distributed in the carriage ways as sketched for calculation as
figure 1-2.
l
e /2
b
b
d
e /2
B
Figure 1-1 Traffic load calculation diagram
6
Noi Bai International Airport to Nhat Tan Bridge Connecting Road Construction Project
Stage: Working drawing Package 2: Km1+539.48 -:- Km3+943.00
Figure 1-2 Traffic load value and distribution
6. Calculation methodology
6.1 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 for settlement calculation 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
∆
e method):
H

o
s
c
P
PP
H
e
C
S
∆+
+
= log
1
For over consolidation and P
c
>P
0
+
∆
P (2-3)
c
cc
o
s
c
P
PP
H
e
C

PP
H
N
P
S
∆+
=
0
log4.0
(2-5)
1m
As designed
1.5m 1m
q=1.54 t/m
2
q=1.54 t/m
2
1.5m
7
Noi Bai International Airport to Nhat Tan Bridge Connecting Road Construction Project
Stage: Working drawing Package 2: Km1+539.48 -:- Km3+943.00
Where as:
Sc: Consolidation settlement,
Si: Immediately settlement of sandy soil layer,
e
o
: Void ratio at pressure of P
0
(Initial void ratio),
e

– T
v
relationship as follow:
2
1004






×=
U
T
v
π
in case 0<U<53% (2-7)
( )
UT
v
−×−= 100log933.0781.1
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, etc. are installed for soft soil treatment,
consolidation degree will be evaluated from Carrillo expression:

exp1
(2-10)
2
.
e
h
h
d
tC
T =
(2-11)
rs
FFnFF ++= )(
(2-12)
2
2
2
2
4
13
ln
1
)(
n
n
n
n
n
nF
−

h
s
d
d
k
k
F ln1
(2-15)
( )
w
h
r
q
k
zLzF −= 2
π
(2-16)
Where as:
T
h
: Time factor,
C
h
: Horizontal consolidation coefficient,
d
e
: Effective drainage distance (=1.13d
s
for square pattern, =1.05d
s

mUPPPC
c
××∆+−=∆
0
(2-24)
Where as:
∆
C: Increased amount of undrain shear strength due to consolidation,
m: Index of increase of undrain shear strength.
m = tg
ϕ
CU
(Show in table 3-1)
d) Sliding check
Bishop method as formulated below is recommended for sliding check.
( )
[ ]
∑
∑
×−+×
=
α
ϕ
sin
tan
1
w
buwbC
m
Fs

Figure 2-2 Sliding check model
6.2 Software
All calculation has been computed with assistance of software: Microsoft Exell for calculation
of settlement and consolidation, and Geoslope for sliding check.
7. Summary of Soil Value for Soft Soil Treatment Design
According to laboratory testing, values of the soil recommended for soft soil treatment design
are summarized in the following table 3-2.
Table 7-1. Summary of Soil Parameters Recommended for Soft Soil Treatment Design
Layer soil
γ
o
ε
o
Pc OCR Cc Cs Cv
KN/m
3
KN/m
2
10
-4
cm
2
/s
Borrow material
18.50 30
o
00’ 0.00
3b 18.80 0.832 12.60;
11.60
1 0.235;