frost heave properties in ballast tracks tc202/archive... · lead sphere +tc 0 ℃ frozen fringe ts...

Frost Heave Properties in Ballast Tracks Field Observations and Laboratory Experiments

Satoshi AKAGAWA Cryosphere Engineering Laboratory

1/41 Cryosphere Engineering Laboratory

Topics

What is Frost Heaving

Field Works Monitoring at railway tracks

Laboratory Works Frost heave tests of crushed rock with different fines content

2/41 Cryosphere Engineering Laboratory

Topics

What is Frost Heaving

Field Works Monitoring at railway tracks

Laboratory Works Frost heave tests of crushed rock with different fines content

Cryosphere Engineering Laboratory 3/41

What is frost heaving.

Cryosphere Engineering Laboratory 4/41

Ice Lens Segregates at Negative Temp.

Cryosphere Engineering Laboratory

Frozen

Unfrozen

Surface of

Segregating Ice Lens

Lead sphere +TC

0 ℃ Frozen Fringe

Ts

5/41

Crystal Structure of Ice Lens

Cryosphere Engineering Laboratory 6/41

Schematic Drawing of Ice Lens

Cryosphere Engineering Laboratory 7/41

How Pore Water Freezes

Cryosphere Engineering Laboratory 8/41

Distribution and Thickness of Unfrozen Water

Cryosphere Engineering Laboratory 9/41

Field Observation

Cryosphere Engineering Laboratory 10/41

Our Test Fields

Cryosphere Engineering Laboratory 11/41

Ballast Track Structure

Cryosphere Engineering Laboratory 12/41

What is the uncertainty?

Dose ballast which contains fines frost heave?

Cryosphere Engineering Laboratory 13/41

Temperature Measurement in Railway Track Layers

Cryosphere Engineering Laboratory 14/41

Frost Heave Measurement in Railway Track Layers

Truncated cone

Cryosphere Engineering Laboratory 15/41

What items have monitored

Cryosphere Engineering Laboratory 16/41

Frost Heave Monitored in Ballast Track

Data of Furen Cryosphere Engineering Laboratory

17/41

Laboratory Observation

Cryosphere Engineering Laboratory 18/41

Grain Size Distribution of Ballast Track

Fhuren

Shizukuishi

12/20 Cryosphere Engineering Laboratory

19/41

Textures of Real Ballast

Cryosphere Engineering Laboratory 20/41

Mineral compositions of ballast and subgrade at Fhuren and Shizukuishi

Cryosphere Engineering Laboratory 21/41

Frost Heave Test Results (Shizukuishi)

Cryosphere Engineering Laboratory 22/41

A Model for Prediction

of Ballast Frost Susceptibility

Cryosphere Engineering Laboratory 23/41

An Empirical Formula has been used in Japan

for Frost Heave Susceptibility Prediction

,

,

0

0

1 0UU

where, ; heave ratio,

; confining pressure,

; freezing speed,

; test constants

U

0

0

0U

h

H Original

height

Heave amount

Hh

Cryosphere Engineering Laboratory 24/41

How the Ballast Layer Frost Heaves

17/20

Cryosphere Engineering Laboratory 25/41

Confirmation of

Proposed Formula

Cryosphere Engineering Laboratory 26/41

Utilized Ideal Ballast which contains Fines

Kaolinite Gs=2.54 g/cm3 Crushed Rock I Grain Size Distribution; 2.5mm to 5.0mm Crushed Rock II Grain Size Distribution; 13mm to 20mm

Cryosphere Engineering Laboratory 27/41

Frost Heave Test Apparatus−I

Thermal Bath

Valve

LVDT

Valve

Pt Temp.

Φ=200mm

Cryosphere Engineering Laboratory 28/41

Frost Heave Test Apparatus−II

ϕ=50mm

L=20 to 100mm LVDT

Weight

Thermal Bath

Φ=50mm

Pt Temp.

Valve for PW

Cryosphere Engineering Laboratory 29/41

Frost Heave Test Conditions

Overburden Pressure:33.9(kPa)

Pore Water Pressure：0kPa

Confining Pressure

Height：38～47(mm)

Diameter：50(mm)

Specimen Size

Height：92～111(mm)

Diameter：200(mm)

Temperature Gradient:

2.4

0

-2.4

Tw

Tc

0 48

Freezing Speed：0.10（cm/hr）

Thermal Condition

Example: Specimen Height = 48 mm

Apparatus I

Apparatus II

0.5(℃/cm）

Time (hr) Bo

un

dar

y T

emp

. (o

C)

Cryosphere Engineering Laboratory 30/41

Frost Heave Tests Result

Cryosphere Engineering Laboratory 31/41

How the Ballast Layer Frost Heaves

Cryosphere Engineering Laboratory 32/41

Anticipated Result F

rost

Heave R

ate

(ξ)

Because of the unsaturated

pore condition with fines, frost

heave of the fines may not

contribute the macroscopic frost

heave in CASE-3.

In the CASE-3, steeper reduction of HEAVE RATE was expected.

Pores are not saturated with fines

Pore

3

V

V fCASE-3

Finds

Ballast

Piece of ballasts are floating in the pore fines

CASE-2

Cryosphere Engineering Laboratory 33/41

Vertical Section of frozen Fines (CASE-1) H

eat

Flo

w D

irection

Horizontally elongated ice lenses

which are normal to the heat flow are

observed. Vertical ice veins which are

developed by the shrinkage due to

pore water pressure depression in

frozen fringe is also observed.

Normal frost heaving has happend

Cryosphere Engineering Laboratory 34/41

Vertical section of frozen Ballast (CASE-3)

⇒Even in the CASE-3, pores are filled with fines and ice lenses but no frozen balk water.

Mac

rosc

opi

c H

eat

Flo

w D

irection

57.03 =V

V f÷÷ø

öççè

æ= 19.0

V

V f

Cryosphere Engineering Laboratory 35/41

Fines between Piece of Ballasts

may Segregate Thick Ice Lenses M

acro

scopi

c H

eat

Flo

w D

irection

0 isotherm in rock advances faster.

Thermal conductivity of rock is

higher than soil.

Thick ice lens may segregate.

Heave at the rock-fines boundary last

longer.

Thick ice lenses have developed

at the upper part of piece of

ballasts (=cold side of piece of

ballasts)

Cryosphere Engineering Laboratory 36/41

Fins in pores frost heave higher than

total heave M

acro

scopi

c H

eat

Flo

w

Direction

Fines in pores show higher

frost heave ratio.

Microscopic heat flow

may meander due to

inhomogeneity of thermal

conductivity

Microscopic frost heave

ratio along the white dotted

line was 32%, whereas

average was 14%.

Cryosphere Engineering Laboratory

37/41

Cause of Thick Ice Lenses in Pore in CASE-3 M

acro

scopi

c H

eat

Flo

w D

irection

Then fins suffer almost no

confinement.

Initially total stress was supported

by rock skeleton.

Heave rate of fines under very low

confinement is very high.

Cryosphere Engineering Laboratory 38/41

Again what was happened

Rock

Fines

Initial Condition

Final Condition

Ice Lens

Cryosphere Engineering Laboratory 39/41

One Evidence

Cryosphere Engineering Laboratory 40/41

Conclusions

Ballast which contains fines may frost heave.

Proposed empirical formula provides frost heave susceptibility of ballast which contains fines.

However farther researches will be required to refine the reliability of the proposed formula.

Cryosphere Engineering Laboratory 41/41

Thank you for your attention

Cryosphere Engineering Laboratory