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

• Numerical Modeling of Moisture Migration

in High-speed Railway Embankment

Hanlin Wang, Ph.D. Student

Zhejiang University

August 5, 2015

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

Outline

Background

Modeling

Material Parameter

Rainy Conditions

Initial and Boundary Conditions

Results and Analysis

Conclusions

2

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

Background

Rainwater infiltrates into the embankment through fissures in rainy days.

3

Dk

0.4 m

2.3 m

Subgrade

Subsoi l

I nf i l t rat i on of rai nwat er

Sat urat i on Zone

Roadbed

Fi ssure

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

Background

Water disease: mud pumping, differential settlement, landslide, etc.

4

Dk

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

Rainfall precipitation

Model Overview

Modeling on the basis of fissure development at the junction area between concrete base and concrete slab above the roadbed

Fissures Infiltration area

Raining duration

Dk

5

Infiltration area

Roadbed

Subgrade

Subsoil

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

Dk

Material Parameter

Four calculation conditions

Subgrade Category Subgrade

(0.85, 15.4%) Subgrade

(0.90, 15.4%) Subgrade

(0.93, 15.4%) Subgrade

(0.93, 30%)

Compaction Degree 0.85 0.90 0.93 0.93

Fine Particle Content （%） 15.4 15.4 15.4 30.0

100 10 1 0.10

20

40

60

80

100

Per

cen

t F

iner

(%

)

Particle Diameter, d (mm)

China Railway Standard (lower limit)

China Railway Standard (upper limit)

Rahardjo (2008)

Roadbed

100 10 1 0.1 0.01 1E-30

20

40

60

80

100

Perc

en

t F

iner

(%)

Particle Diameter (mm)

Subgrade material

Fine Particle Content=15.4%

Fine Particle Content=30.0%

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

Dk

Measurement of SWRC and

Permeability of Subgrade Materials

Large-scale infiltration column

TDR5

TDR4

TDR3

TDR2

TDR1

T5

T4

T3

T2

T1

300mm

150mm

100mm

100mm

100mm

100mm

100mm

30mm

Tensiometers

Infiltration

column

TDR 100

TDR

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

Dk

Material Parameter

SWRC and unsaturated permeability coefficient

8

0.01 0.1 1 10 100 10000.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Vo

lum

etr

ic W

ate

r C

on

ten

t

Matric Suction (kPa)

Roadbed

Subsoil

Fissure

Subgrade (0.85,15.4%)

Subgrade (0.90,15.4%)

Subgrade (0.93,15.4%)

Subgrade (0.93,30%)

0.01 0.1 1 10 100 10001E-18

1E-16

1E-14

1E-12

1E-10

1E-8

1E-6

1E-4

0.01

Pe

rmeab

ilit

y C

oeff

icie

nt

(m/s

)

Matric Suction (kPa)

Roadbed

Subsoil

Fissure

Subgrade (0.85,15.4%)

Subgrade (0.90,15.4%)

Subgrade (0.93,15.4%)

Subgrade (0.93,30%)

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

In rainy days, the process of raining is continuous （Zhou, 2005）

Relationship between maximum rainfall

intensity per unit time and daily precipitation

（Zhou, 2005）

Dk

Rainy Conditions

9

Relationship between rainfall intensity and raining duration

(Webster 1905)

/ ni S t 1/ nI it S t

i iS a I b

Relationship

between daily

precipitation and

raining duration

0.3622, 6.376, 0.565i ia b n

0 50 100 150 200 2500

2

4

6

8

10

Ra

inin

g D

ura

tio

n t

Daily Precipitation I (mm)

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

Parameters Roadbed Subsoil Crack Subgrade

(0.85,

15.4%)

Subgrade

(0.90,

15.4%)

Subgrade

(0.93,

15.4%)

Subgrade

(0.93,

30%) Volumetric

Moisture Content

(%) 10 29.52 10 13.70 13.70 13.70 15.19

Matric Suction

(kPa) 13.2 185.84 389.14 3.75 2.08 15.37 1.46

Dk

Initial and Boundary Conditions

Initial conditions

10

Boundary conditions

0.4

m2

.3 m4%

27m

2m

5m4.3m 4.3m

1:1.5 4%

1

2

3

4 56 7

89

10

11

12

13

14

Subsoil

Subgrade

Roadbed

Crack

Concrete BaseFree seepage

Impervious

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

Dk

Results (0.93,15.4%)

11

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

Dk

Results after 3 Year Cycle

12

0.85,15.4% 0.90,15.4%

0.93,15.4% 0.93,30%

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

Dk

Saturation Zone Comparison

13

Compaction degree↑

Saturaion zone↑

slightly

Fine particle content↑

Saturation zone↑

significantly

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

Dk

Volumetric Water Content

Variations with Time (Point A)

Roadbed, 0.1 m right below the lower edge of the crack

Not influenced by different subgrade fillings

14

0 200 400 600 800 10000.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.85-15.4%

0.90-15.4%

0.93-15.4%

0.93-30%h=4.6m

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

Dk

Volumetric Water Content Variations

with Time (Point B)

Close to the interface of roadbed and subgrade

15

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.85-15.4%

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.90-15.4%

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.93-15.4%

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.93-30%

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

Dk

Volumetric Water Content

Variations with Time (Point B)

Water arriving time is the longest for subgrade (0.93,15.4%)

Volumetric Water Content Range after Stabilization: subgrade (0.93,15.4%) and subgrade (0.93,30%) have comparatively low fluctuation.

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Point B Subgrade

(0.85, 15.4%) Subgrade

(0.90, 15.4%) Subgrade

(0.93, 15.4%) Subgrade

(0.93, 30%)

Initial Matric Suction

(kPa) 3.75 2.08 15.37 1.46

Initial Permeability

Coefficient (m/s) 1.24e-9 1.44e-9 2.38e-12 1.88e-10

Water Arriving Time

(day) 48 48 71 59

Volumetric Water

Content Range after

Stabilization 0.13-0.30 0.13-0.25 0.20-0.28 0.15-0.23

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

Dk

Volumetric Water Content Variations

with Time (Point C) Middle area of subgrade

High-elevation saturation zone for subgrade (0.93,30%)

17

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.85-15.4%

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.90-15.4%

0 200 400 600 800 10000.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.93-15.4%

0 200 400 600 800 10000.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.93-30%

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

Saturation zone development

Dk

Volumetric Water Content

Variations with Time (Point D)

No long-term saturation zone for subgrade (0.85,15.4%)

Compaction degree↑, water arriving time↑significantly

18

0 200 400 600 800 10000.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.85-15.4%

0.90-15.4%

0.93-15.4%

0.93-30%

h=2.9m

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

Dk

Volumetric Water Content

Variations with Time (Point C and D)

Longest water arriving time from C to D: subgrade (0.93, 30%)

Point C Subgrade

(0.85, 15.4%) Subgrade

(0.90, 15.4%) Subgrade

(0.93, 15.4%) Subgrade

(0.93, 30%) Water Arriving

Time (day) 60 60 125 89

Volumetric Water

Content Range

after Stabilization 0.15-0.3 0.14-0.25 0.20-0.28

“Saturation zone”

after 496 days

Point D Subgrade

(0.85, 15.4%)

Subgrade

(0.90, 15.4%)

Subgrade

(0.93, 15.4%)

Subgrade

(0.93, 30%) Water Arriving

Time (day) 62 67 133 140

Volumetric Water

Content Range

after Stabilization 0.17-0.30

“Saturation zone”

after 122 days “Saturation zone”

after 158 days “Saturation zone”

after 180 days

From C to D Subgrade

(0.85, 15.4%)

Subgrade

(0.90, 15.4%)

Subgrade

(0.93, 15.4%)

Subgrade

(0.93, 30%) Water Migrating

Time (day) 2 7 8 51

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

Dk

Volumetric Water Content

Variations with Time (Point E)

20

0 200 400 600 800 10000.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Vo

lum

etr

ic W

ate

r C

on

ten

t

Time (day)

0.85-15.4%

0.90-15.4%

0.93-15.4%

0.93-30%

h=2.3m

Point E Subgrade

(0.85, 15.4%) Subgrade

(0.90, 15.4%) Subgrade

(0.93, 15.4%) Subgrade

(0.93, 30%) Formation Time of

“Saturation Zone” (day) 71 73 152 160

Water accumulates at the interface of subgrade and subsoil. Infiltration velocity to the subsoil is extremely low.

Compaction degree↑, formation time of saturation zone↑significantly. Fine particle content has little effect.

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

Dk

Threat to the Embankment with the

Presence of “Saturation Zone”

21

Matric suction↓ Shear strength↓

Unsaturated Saturated

instability

Cumulative settlement of Shijiazhuang-

Taiyuan Railway Line reaches 64.2 cm with

infiltration of rainwater and it

causes instability failure.

Stiffness↓ Settlement↑

The running speed of Japanese shinkansen reduces to 110~180

km/h due to settlement caused by

water infiltration

Mud pumping disease

Shanghai-Nanjing Railway

Line

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

Dk

Conclusions

After 3 year cycle, “saturation zone” develops for each condition. The size increases with compaction degree (little influence ) and fine particle content.

Subgrade (0.93, 15.4%) has the longest time for water to pass the interface of roadbed and subgrade.

Subgrade (0.93, 15.4%) and (0.93, 30%) have comparatively small fluctuation of volumetric water content.

Subgrade (0.93, 30%) has the largest “saturation zone” and it develops at high elevation.

Formation time of “saturation zone” at the interface of subgrade and subsoil increases significantly with compaction degree. Fine particle content has little effect.

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

Thank you!

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

Q & A

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