Mechanical Behaviors of Cylindrical Retaining Structures ...cem.uaf.edu/media/138804/pengfei-xu.pdf · Mechanical Behaviors of Cylindrical Retaining Structures in Ultra-deep Excavation

ISSAEST, Fairbanks, AK, USA, August 2-5, 2015

Mechanical Behaviors of Cylindrical

Retaining Structures in

Ultra-deep Excavation

Pengfei Xu

Tongji University

August 4, 2015


Outline

2

Introduction

Two circular excavations for anchorage foundations

3D finite element analyses

FEM results versus field measurements

Influence factors

Conclusion


Introduction

3


Introduction

4

Suspension bridge

Anchorage foundation

Deep excavation with reinforced concrete retaining structures


Introduction

5

Two common types of retaining walls

Circular rectangular


Introduction

6

Arch effect

Have much stronger capabilities of resisting deformation

(Tan and Wang 2013)

The lateral earth pressure is much smaller than that calculated

by Rankine theory (Kim 2013)

Provide larger space for excavation

Structural superiority of circular retaining walls


Introduction

7

Zhou and Luo (2003)

Circular retaining wall——Elastic foundation-beam

Arch effect——Supporting structure

Song (2004)

Ring-beam load-distribution theory

Simplified methods to calculate the structural forces of circular

diaphragm walls


Introduction

8

Marten and Bourgeois (2006)

Prashar et al. (2007)

FEM to simulate the circular excavation process

Field data to verify theoretical and numerical results

Schwamb et al. (2014)


Introduction

9

Provide support to circular diaphragm wall

Enhance the integrality of the whole retaining structure

Lining walls

Research objective

The behaviors of cylindrical shafts and the interaction

between the diaphragm wall and the lining wall

3D FE analyses of two circular excavations for anchorage

foundations in suspension bridge engineering

Field measurements for verification

Research method


The south anchorage engineering of

yangluo yangtze river bridge

10

Yangluo Yangtze River Bridge in Wuhan is a double-tower

suspension bridge with a main span of 1280 m.

Circular diaphragm wall

External diameter: 73.0 m

Height: 54.5-60.5 m

Thickness: 1.5 m

ISSAEST, Fairbanks, AK, USA, August 2-5, 2015 11

Physico-mechanical parameters of soil and rock layers

(Yangluo Bridge)

Soil and Rock

Layers

Young’s

Modulus

(MPa)

Unit Weight

(kN/m3)

Cohesion

(kPa)

Friction

Angel

(º)

Layer

Thickness

(m)

Superficial

clay loam 4.5 18.9 26.8 15.4 1.5

Clay 3.5 18.8 10.0 8.0 6.0

Clay loam

interbedded with

sandy loam

5.5 19.0 12.4 9.1 7.5

Silty fine sand 13 19.3 — 33.0 28.0

Gravel sand 33 21.3 — 40.5 9.0

Strongly weathered

conglomerate 600 23.6 — — 5.0

Weakly weathered

conglomerate 7500 26.2 — — 33.0






12

Plan view with monitoring points

G1-A

G8-A

G7-A

G6-A

G3-A

G2-A

G4-A

G5-A

G1-B

G8-B

G2-B

G4-B

G5-B

G6-B

G3-BG7-B

WL1

WL2WL4

WL3

Di aphragm wal l

Li ni ng wal l

Di aphragm wal l

21.5m

-21.5m

1.5m

71.5m

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

Di aphragm wal l

5m

19m

6mx5

-16m

6mx5

3mx2

4m4m

-31m

Moni t or i ng poi nt s of ci r cumf erent i al st r essMoni t or i ng poi nt s of ver t i cal st r ess

Cappi ng beam

Li ni ng wal l

4m

1.5m

2m

2.5m

3mx2

3mx5

3mx6

4m

2.5m

3mx2

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

Profile with monitoring points and excavation

process



nanjing 4th yangtze river bridge

13

Nanjing 4th Yangtze River Bridge is the first double-tower and

three-span suspension bridge in China with a main span of 1418 m.

Double circular diaphragm wall

External diameter: 59.0 m

Length: 82.0 m

Width: 59.0 m

Height: 40.0-50.0 m

Thickness: 1.5 m

Distance between the centers of

the two circles: 23.0 m




14

Soil and Rock Layers

Calculation Thickness

(m) Young’s

Modulus

(Mpa)

Cohesion

(kPa) Friction

Angel (º) North Side

South

Side Silty clay 2.0 2.0 1.65 21 8.9

Soft muddy clay 4.1 4.1 2.16 21 4.6 Silty sand and regional

fine sand 1.9 1.9 11.26 7 31.8

Very soft silty clay

interbedded with silty

sand 9.0 7.0 8.5 20 14.1

Silty sand 3.0 - 29.4 6 33.2 Silty clay 13.0 18.0 14.26 23 13.5 Silty sand 6.0 - 52.46 6 33.2

Strongly weathered

conglomerate 1.0 1.0 5000 2940 46.3

Weakly weathered

sandstone 3.0 9.0 10000 2940 46.3




15

8200

AA

350 3675250 3675 250

4400 ~

5000

180

1320

1200

1320

400~

1000

150

200 4000 ~

4400

180

1320

1200

1000

300~

700

120

300x10

400

150

100100

B-B8200

D 5

900

A-A

N S

300

200 245

2341.4

280

784.3

150100 100

R29

50

R2800

367.5

B B

Schematic diagram


Finite element formulation

16

Type of analysis

General purpose finite element code ABAQUS

Hexahedral isoparametric element

Initial stress state——The gravity loads of the soil and

walls were introduced to the model in a geostatic step

Construction process simulation——remove the soil

elements and activate the lining elements


Finite element formulation

17

Plasticity model of soil

Mohr-Coulomb model

Elastic model of concrete

Retaining walls C35 E=3.15×104 N/mm2

Lining walls C30 E=3.00×104 N/mm2

Poisson’s ratio 0.2

Soil-wall interaction

Tangential direction——critical shear stress τcrit=μp

(Coulomb friction law)

Normal direction——the rigidity is infinite


Finite element model

18

Size of the modelling region

Width of the soil outside the

diaphragm wall 3-4He

Depth of soil mass 2.5He

—(He is the excavation depth)

Entire FE mesh

FE mesh of the diaphragm and lining walls

400 m (diameter)×150 m (depth)


Finite element model

19

Entire FE mesh FE mesh of the diaphragm and lining walls

400 m (length)×300 m (width)×100 m (depth)

Boundary conditions

Base Horizontal and vertical displacements

Side Normal displacements

Top Free


FEM results

20

Maximum principal

tensile stress

Maximum principal

compressive stress

Diaphragm wall (Yangluo Bridge)


FEM results

21

Lining walls (Yangluo Bridge)

Maximum principal

tensile stress

Maximum principal

compressive stress


FEM results

22

Maximum principal

tensile stress

Maximum principal

compressive stress

Diaphragm wall (Nanjing 4th Yangtze River Bridge)


FEM results

23

Maximum principal

tensile stress

Maximum principal

compressive stress

Lining walls (Nanjing 4th Yangtze River Bridge)


FEM results versus field

measurements

24

Di aphragm wal l

21.5m

-21.5m

1.5m

71.5m

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

Di aphragm wal l

5m

19m

6mx5

-16m

6mx5

3mx2

4m4m

-31m


Cappi ng beam

Li ni ng wal l

4m

1.5m

2m

2.5m

3mx2

3mx5

3mx6

4m

2.5m

3mx2

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)

G1-A

G8-A

G7-A

G6-A

G3-A

G2-A

G4-A

G5-A

G1-B

G8-B

G2-B

G4-B

G5-B

G6-B

G3-BG7-B

WL1

WL2WL4

WL3

Di aphragm wal l

Li ni ng wal l



measurements

25

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-70

-60

-50

-40

-30

-20

-10

0

10

Dep

th (

m)

Vercital stress (MPa)

FEM results

Measurements at G7-B

Measurements at G1-A

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2-40

-35

-30

-25

-20

-15

-10

-5

0

5

Dep

th (

m)

Circumferential stress (MPa)

FEM results

Measurements

at WL3-B

Measurements

at WL1-B

Yangluo Bridge



measurements

26


-35m

-39m~-45m



measurements

27

-5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5-50

-45

-40

-35

-30

-25

-20

-15

Dep

th (

m)

Circumferential and vertical stress (MPa)

FEM results

Measurements at GJ06-A

Measurements at GJ06-B

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5-34

-32

-30

-28

-26

-24

-22

-20

Dep

th (

m)

Circumferential stress (MPa)

FEM results

Measurements at NC01-A

Measurements at NC01-B

Nanjing 4th Yangtze River Bridge


Influence factors

28

Results of analysis of influence factors of the mechanical

characteristics of retaining structures

(Yangluo Bridge)

Model Numbel

Maximum Principal Stress of

Diaphragm Wall (MPa) Maximum Principal Stress of

Lining Walls (MPa)

Tensile Stress Compressive

Stress Tensile Stress Compressive

Stress

original 0.430 11.41 0.039 6.389

1 0.652 11.72 - -

2 0.652 11.43 0.039 6.868

3 0.648 11.62 0.058 6.406

4 0.652 11.50 5.714 0.899


Influence factors

29

Results of analysis of influence factors of the mechanical

characteristics of retaining structures

(Nanjing 4th Yangtze River Bridge)

Model Numbel

Maximum Principal Stress of

Diaphragm Wall (MPa) Maximum Principal Stress of

Lining Walls (MPa)

Tensile Stress Compressive

Stress Tensile Stress Compressive

Stress

original 0.969 5.084 1.017 1.783

1 1.207 6.217 1.260 2.046

2 0.797 5.132 1.176 2.787

3 4.802 2.430 - -


Conclusion

30

1. Cylindrical or double cylindrical shafts have strong structural

superiorities.

2. The proposed 3D finite element method well simulated the

entire construction processes of both circular and double circular

excavations.

3. The stresses in both the diaphragm walls and lining walls are

relatively small, indicating that the arching effects of circular and

double circular retaining structures are significant.


Conclusion

31

4. The main function of the lining walls is to enhance the rigidity

of the diaphragm wall and to constrain its displacements, so the

decrease in the lining wall thickness, the shape variation of the

retaining structures and asymmetrical excavation make little

difference to the structure stress.

5. The temperature change during circular or double circular

excavation has a great influence on the stresses of the retaining

structures.


Acknowledgement

32

The financial support from Department of

Transportation of Hubei Province and CCCC Second

Harbor Engineering Co., Ltd. was gratefully

acknowledged.


Thank you!

Documents

Mechanical Behaviors of Cylindrical Retaining Structures ...cem.uaf.edu/media/138804/pengfei-xu.pdf · Mechanical Behaviors of Cylindrical Retaining Structures in Ultra-deep Excavation