Application of EPS for remedial work of bridge bearing unit on Bangkok Soft Clay : A

case study

By Dr. Sompote Youwai

Research Center of Geomechanics and Ground ImprovementKing Mongkut’s University of Technology Thonburi

Outline of the presentation

-Introduction of Bangkok Soft Clay-Project information-Design Concept -Material properties of EPS

Location of the project

Mouth of Chaopraya River

Kallaprapreuk road Constructed since 2002

Start

End

1

3

4

5

6

7

8

9 10,11

N

S2/1,S2/2

N2/1N2/2

In bound

Composed of 22 bridges in 10 km

Bangkok Flood Plane-Alluvial deposit by the river-Thick soft clay deposit

Bangkok Soft Clay Area

Zone I –very low strength

Zone II- Low strength

Bangkok Subsoil condition

Very soft clay

Ground subsidence in Bangkok area50 to 100 mm per year

-12 m

-20 m

-28 m

Very soft clay

Soft clay

Medium clay

Su =8-12 kPa

Su =12-28 kPa

Su >50 kPa

Typical soil profile of the project

0 5 10 15 20 25 30 351.0

0.8

0.6

0.4

0.2

0.0

Primary and Ground Subsidence

Sett

lem

ent,

s (

m)

Time, t (year)

Primary consolidation

Settlement of 2 m height-embankment on Bangkok Soft Clay

0 20 40 60 80 1001

2

3

4

(Proposed Profile Grade)

(Profile Grade)

Pro

file

Ele

vation (

m)

Distance from Abutment (m)

Settlement is higher than expected design value.

Tilting

การยกตวัของปลายคอสะพานบรเิวณตอมอ่

สะพาน

Parapet ดนักนัจนแตก

การยกตวัของปลายคอสะพานบรเิวณตอมอ่

สะพาน

โพรง

ตอมอ่

คอสะพานยกตวัข้ึน

โพรง

ตอมอ่สะพาน

วัสดถุมคอสะพาน

Structural damage

(d) รอยแตกของ abutment

เกดิรอยแยก

(d) รอยแตกของ abutment

เกดิรอยแยก

(d) รอยแตกของ abutment

Overlay

(d) รอยแตกของ abutment

พบการทรดุตวัอยา่งชดัเจน

Method Cost Time

Reconstruction High Long

Light weight material Moderate Short

Sett

lem

ent

Applied stress

Change sand backfill to EPS

Current state7 years after construction

Yield stress

Preloading concept-OCR increase-Soil foundation is in elastic range

0 10 20 30 40 501.0

1.5

2.0

2.5

3.0

3.5

4.0

Infinity (EPS)

3.56 %

Ele

va

tio

n,

z (

m)

Distance from abutment, d (m)

As-built

2.5 %

Infinity (original)

t = 9 yr

3.90 %

Settlement prediction

Material Testing

-Verification of deformation at loading at service state

LVDTLoad Cell

LDT

Clip gage

EPS specimen

Uniaxial cyclic testing of EPS

Density

Yield Point

Test Series:Uniaxial Cyclic Test (Unit weight = 0.22 kN/m3: DA = 10 kPa)

Stress-strain is highly reversible

Test Series:Uniaxial Cyclic Test (Unit weight = 0.31 kN/m3: DA = 10 kPa)

Stress-strain is highly reversible

EPS 0.22 kN/m3 EPS 0.31 kN/m3

Summary properties from present data

Density

(kN/m3)

E0 (kPa) Eeq@1st

level

(kPa)

Eeq@2nd

level

(kPa)

Eeq@3rd

level

(kPa)

Yield

point

(kPa)

Poisson’s

ratio

0.22 14888 13650 11780 10957 90 -0.1

0.31 21452 20880 19788 15955 203 -0.1

Engineering properties of EPSASTM D 1622 Density 0.22 kN/m3 (min.)

0.45 kN/m3 (max.)

ASTM D 1621 CompressiveStrength:

at 1% deformation 50 kPa

at 5 % deformation 115 kPa

at 10 %deformation

135 kPa

ASTM C 203 Flexural Strength 276 kPa

ASTM D 2863 Flammability (Oxygen Index) 24.0 %

Conclusion

1. The EPS was employed for replacement of existing backfill sand for remedial method of bridge approach structure on soft ground. The thickness of the EPS fill was varied with the distance from bridge structure.

2. The long term settlement was reduced due to unloading mechanism of soft clay foundation.

3. For laboratory testing, there was no significant permanent deformation of EPS subjected to cyclic loading for loading levels less than 60 % of the material yield stress.

http://www.set.ait.ac.th/acsig/GA2012/home.htm

5th Asian Regional Conference on Geosynthetics

10 to 14 December 2012Bangkok, Thailand