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Summary of Soil Value for Soft Soil Treatment Design 8.. Result of soft soil treatment embankment 10.. Noi Bai international airport to Nhat Tan bridge connecting road construction proje

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

10 Appendix

10.1 Summary of the result of soft soil treatment

10.2 Result calculate settlement and auditing falling stability of embankment 10.3 Treatment cross section

Noi Bai international airport to Nhat Tan bridge connecting road construction project

Stage: working drawings PACKAGE 2: Km1+539.48 -:- Km3+943.00 Report on soft soil treatment

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 road of Nhat Tan Bridge project and Nam Hong road in Van Noi commune, Dong Anh district The Ending point is conjunction road to T2 Station of Noi Bai Airport in Soc Son district, Ha Noi Capital

Features package 2:

Construction location: Dong Anh, Ha Noi

Beginning: Km1+539.48 The retaining wall abutment A10 of railway bridge over, endpoint package 1

Endpoint: Km3+943.00 The retaining wall abutment A0 Ca Lo bridge

The total length: L = 2403.52m

2 Legal basic for implementation

- Decree No 12/2009/NĐ-CP dated 12/02/2009 issued by the Government regarding structure construction management ;

- Circular No 03/2009/TT-BXD dated 26/3/2009 by the Government regarding regulating details of some agenda of Decree No 12/2009/NĐ-CP dated 12/02/2009 regarding structure construction investment project ;

- Pursuant to the Government Decree No 34/2003/NĐ-CP dated 04 April, 2003 stipulating the functions , tasks, powers and organizational structure of the Ministry of Transport;

- Pursuant to the Government Decree No 16/2005/NĐ-CP dated 07 February, 2005 on management and investment for construction of work and the Government Decree No; 1612/2005/NĐ-CP dated 29 June, 2006 on adjustment to some clauses of the Decree

No 131/2006/NĐ-CP dated 07 February, 2005;

- Pursuant to the Government Decree No 131/2006/NĐ-CP dated 09 November, 2006 stipulating Regulation on managing and using source of official development assistance;

- Pursuant to the Government Decree No 209/2004/NĐ-CP dated 16 December, 2004

on construction work quality management;

- 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 Standard used

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 22TCN262-2000 Viet Nam

4 Highway raute composition of geological layers and condition

4.1 Layer DR: Farm land.

This layer was encountered from surface, the thickness of sub-layer change from 0.50m to 0.70m

4.2 Sub- layer 2a: Yellowish grey, Brownish grey, whitest grey, stiff to very stiff, Clay.

It was encountered in BSDY1, BSDY2 and BSTC1 borehole with the top elevation is from 5.23m to 9.77m and from 3.30 to 6.90m of thickness The N value of SPT varies from from 12 to 17

Covention bearing capacity R = 1.70 kG/cm2

4.3 Sub- layer 4b: Brownish grey, soft to medium stiff, Sandy clay.

It was encountered in BSDY1, BSDY2 and BSTC1 (working drawing) with the top elevation is from 1.43m to 2.87m and from 5.20m to 8.00m of thickness The N value

of SPT varies from 4 to 8

4.4 Layer 5: Greenish grey, brownish grey, loose, clayey sand.

It was encountered in BSTC1 (working drawing) hole with the top elevation is -2.33m and 6.80m of thickness The N value of SPT varies from 7 to 9

Convention bearing capacity R = 1.25 kG/cm2

4.5 Sub - layer 6b: Greenish grey, medium dense, small sand.

It was encountered in BSDY1 and BSDY2 (working drawing) hole with the top elevation is from -6.031m to -3.97 and from 7.00 to 7.60m of thickness The N value

of SPT varies from 11 to 15

Convention bearing capacity R = 1.50 kG/cm2

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/cm2

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/cm2 (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/cm2 (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):

- Residual settlement (Sr) is less than: 10cm for approach sections, 20cm for culvert and under passing sections, and 30cm for other sections

- Highway under class 60 with surfacing class A: 20cm for approach sections, 30cm for culvert and under passing sections, and 40cm for other sections

- Consolidation degree is not less than 90% or speed of residual settlement is less than 2cm per year (TCVN5729-97-8.10.2)

5.2 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

5.3 Traffic load.

Traffic load is evaluated in accordance with 22TCN262-2000 from following equations:

l

B

G

n

q





b

n

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: q=1.59 t/m2 and will be distributed in the carriage ways as sketched for calculation as figure 1-2

l

B

Figure 1-1 Traffic load calculation diagram

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

e

e

e

c

0

1

1 



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

0

0 0

log

P P H

e

C

c







o

o o

s

c

P

P P H

e

C



 log

1 For over consolidation and Pc>P0+P (2-3)

c

c c o

s

c

P

P P H e

C P

P H

e

C







0 0

log 1

log

1 For overconsolidation and Pc<P0+P (2-4)

In the sand layer, the following formula can be used for immediately settlement (De Beer method)

o

o

i

P

P P H

N

P

1m

As designed

q=1.54 t/m 2 q=1.54 t/m 2

1.5m

Where as:

Sc: Consolidation settlement,

Si: Immediately settlement of sandy soil layer,

eo: Void ratio at pressure of P0 (Initial void ratio),

e1: Void ratio at pressure of P0+P,

P0: Overburden pressure,

P: Pressure caused by embankment,

Cc: Compression index,

Cs: Swell index,

Pc: Pre-consolidation pressure,

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:

2

H

Cv

t

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

2

100











T v  1 781  0 933  log 100  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:

 U v  U h

Where as:

Uv: Vertical component of consolidation being computed as mentioned above,

Uh: Horizontal component of consolidation being computed from Hansbo

recommendations as follow:











  





F

T

h

8 exp

2

e

h

h

d

t

C

r

F

n

F

2

2

2

2

4

1 3 ln 1

)

(

n

n n n

n

n



w

e

d

d





























w

s s

h

d k

k

 

w

h

k z L

z

Where as:

Th: Time factor,

Ch: Horizontal consolidation coefficient,

de: Effective drainage distance (=1.13ds for square pattern, =1.05ds 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 C due to consolidation being evaluated as follow:

Where as:

C: Increased amount of undrain shear strength due to consolidation,

m: Index of increase of undrain shear strength

m = tg CU (Show in table 3-1)

d) Sliding check

Bishop method as formulated below is recommended for sliding check









sin

tan 1

w

b u w b C

m

















Fs

m a   tan

tan 1

Where as (see figure 2-2):

C: Cohesion,

: Internal friction angle,

b: Width of slice,

u: Pore water pressure acting at the slice base,

W: Weight of slice,

 : Slice base angle to the horizontal direction



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 o  o

Pc

OCR Cc Cs Cv Ch/Cv    C 0

KN/m 2

Su KN/m 2 m

3b 18.80 0.832 12.60;

11.60 1

0.235;

0.600

0.044;

4b 18.40 0.926 9.90 >1 0.290;

0.600

0.032;

8 Soft soil treatment analysis

8.1 Summary of result no treatmeant

Please see result of settlement and stability embankment

8.2 Method of treatment

In the section, method of treatment as follows:

SD (Distance d = 1.80m, depth D = 12.00m, Diameter  = 40cm)

9 Result of soft soil treatment embankment

Please see result of settlement and stability embankment