Experimental studies with frozen soil in an “ice sandwich” permeameter

Cold Regions 8cience and Technology, 3 ( 1 9 8 0 ) 1 7 7 - - 1 8 3 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

EXPERIMENTAL

177

STUDIES WITH FROZEN SOIL IN AN "ICE SANDWICH" PERMEAMETER.

K. Horiguchi* and R. D. Miller Department of Agronomy,

Cornell University,

Ithaca, NY

14853 (USA)**

SUMMARY

An "ice sandwich" apparatus can be used in

Williams and Burt (1974) have described a

a dilatometer mode to obtain data for un-

permeameter

for measuring the hydraulic

frozen water content and in a permeameter

conductivity of frozen soil at various

mode to obtain apparent hydraulic conduc-

temperatures.

In their permeameter,

frozen

tivity data for a frozen soil. Measurements

soil was positioned between two compartments

on a 4-8 ~m silt fraction confirmed expecta-

filled with an aqueous solution of lactose.

tions of strong hysteresis effects in both

Lactose concentration was adjusted in a

functions in the range 0 to -0.15°C.

In the

simple fashion to equalize soll temperature

ice sandwich mode (no soil), an imposed hyd-

and freezing point of the solution,

raulic gradient induced regelation and a

until flow across the sample was induced by

measurable temperature gradient.

pressure differentials

With

at least

between end chambers.

frozen soil (permeameter mode), however, the

Although their hydraulic conductivity

induced gradient, if present, was too small

measurements were in general accord with

to be detected with present apparatus.

expectations,

In

it seems inevitable that the

the ice sandwich mode, flow along grain

presence of significant

boundaries in polycrystalline ice was

lactose would compromise interpretation of

negligible, compared to regelation trans-

the results,

port, at-0.040°C.

of

to some unknown degree.

Miller, Loch and Bresler

(1975) analyzed

the expected behavior of a different kind of

INTRODUCTION It is generally believed that a continuous mobile liquid phase persists within lensfree domains in frozen soils at temperatures significantly below 0°C. incorporated

concentrations

This belief is

into various models intended to

explain the dynamics of soil freezing processes.

permeameter,

previously used in this labora-

tory (Sahln, 1973).

Except for the presence

of frozen soil (instead of pure ice) in the central chamber,

this device was physically

equivalent to an ice sandwich apparatus described earlier

(Miller, 1970).

The end

chambers contained pure supercooled water held in that state by porous phase barriers interposed between them and the frozen soil.

* On leave from Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.

Superficially,

at least, results obtained by

Sahin were very similar to those of Burr and Williams. The analysis by Miller, Loch and Bresler

178

presumed that a continuous liquid phase

To capillary,~

would not only allow transport in the liquid phase but transport resulting from regelation of rigid pore ice.

The result would be

coupling of the transports of matter and ice) and of thermal energy

(water

(sensible

and latent heat) within the permeameter/soil

Thermocoup

system. This paper is a progress report on experiments based on the Miller, Loch and Bresler analysis.

We seek, in due course,

to be

able to estimate two components of the apparent hydraulic conductivity,

one associ-

ated with hydraulic flow and one with regelation transport.

A proposed rigid ice

mechanism of frost heave

(c.f. companion

paper by Miller) requires separation of these components,

at least in principle.

APPARATUS AND I~TERIALS The permeameter assembly diagrammed Fig. 1 was used in three modes,

in

(i) as a

Fig. i. Ice sandwich/permeameter/dilatometer apparatus, in cross-section. Freezing of central chamber is nucleated by means of a side tube (top, center). From center chamber to either side, components are: (i) Phase barrier (Millipore filter); (ii) Support screen, stainless steel mesh; (iii) Copper screen support with ports and thermojunctions; (iv) Air gap (nominally 0.008 in.); (v) Copper end member with heater coil (not used). Shaded area represents members machined from nylon. Central chamber 3 mm x 32 mm.

dilatometer for measuring unfrozen water side was directed into a calibrated capil-

content of soil in the manner of Koopmans and Miller

(1966),

(ii) as a permeameter

for

measuring the apparent hydraulic conduc-

lary mounted on a finely divided scale and read with a travelling telescope.

With the

tivity of frozen soil at various tempera-

input pathway closed, the dilatometer mode

tures in the manner of Sahin (1973) and

was achieved; water displaced by formation

(iii) as an ice sandwich apparatus

of pore ice in the soil could be measured in

measure the "apparent hydraulic

to

conduc-

the calibrated capillary;

unfrozen water

tivity" of ice filling the central chambers

content was calculated by deducting volume

in the manner of Miller

of ice formed from total pore volume.

(1970).

The permeameter assembly was used with a control and measurement in Fig. 2.

system diagrammed

The entire system was flushed,

when appropriate,

with deionized deaired

Millipore filters

(GSWP 04700; pore diam.

0.22 ~m) supported by wire mesh screens (Millipore #XX2004708) were used as phase barriers.

In principle,

these should ex-

water drawn from an actively boiling reser-

clude ice from supercooled water within the

voir.

A rigid network of brass stopcock

wire mesh at temperatures down to about

valves

(O-ring seals),

-0.5°C.

tees, and copper

In practice,

freeze-up often

tubing allowed water at elevated pressure

occurred nearer -0.2°C, perhaps due to over-

to be delivered to either side of the

sized pathways, perhaps as a result of

permeameter while outflow from the other

mechanical

shocks.

To avoid inconvenient

179

Richard Berg, USA Cold Regions Research and

RESERVOIR

Engineering Laboratory, Hanover, ~ .

M

CAPILLARY ~)

We are

indebted to Mr. V. A. Snyder for sharing with us this material which he had prepared

HOT PLATE

for other work.

WEIGHTED PISTON

PROCEDURE Soil was emplaced in the partially assembled permeameter by spooning sediment from a water-covered supply onto a wetted phase barrier.

HG MANOMETER

Gentle suction extracted

excess water and consolidated the relatively incompressible material to some degree. When the chamber was deemed to be exactly BATH

full, it was reflooded and the second wetted phase barrier was placed on top.

Fig. 2. Schematic diagram of measurement and control system. Note valves for flushing and flow reversal.

When the

permeameter had been fully assembled, it was connected to measuring and control components and flushed with deionized deaired

surprises, all experiments so far have been water. limited to the range 0 ° to -0.15°C.

Exten.

sion of this range will be attempted later.

Freezing of the central chamber was seeded by bringing the immersed assembly to a tem-

To minimize mechanical coupling of superperature slightly below 0°C. cooled water in the permeameter to vibrations of cooling and stirring mechanisms,

The tip of the

flexible water-filled side tube was lifted, momentarily, above the surface of the bath

the permeameter and associated rigid plumband chilled by a Jet of CO 2 from a pressuring were suspended from the laboratory ized can.

Successful nucleation could be

ceiling. detected by watching the capillary with the Bath temperature,

as sensed by a rapidsystem in the dilatometer mode.

response resistance thermometer, fluctuated Bath temperature was decreased stepwise, within a range of about ± 0.001°C over with measurements delayed for at least 6 periods of many hours with imperceptible hrs but often overnight to allow for redrift.

This performance was achieved with equilibration.

the surface of the bath fluid fully exposed Data for apparent hydraulic conductivity to the laboratory environment.

A complete calculations were collected with flow first

description of the bath and its control in one direction and then in the other. system will be provided on request. There seemed to be no significant difference The only soil material studied to date between the two but this avoided undue was a silt fraction, with sedimentation accumulation of unwanted solutes on the indiameters in the range 4-8 ~m, separated by flow side should they be present. repeated decantation from a supply of ~nchester

silt kindly provided by Dr.

180

6~10

5 ~CE

40

SANDWICH

xIC)3

\~,~/' °

L

u

o

~n

o o

o

E -~3 c u

- 0.04

2

30

O~C

i = 1020.0

o

i

r~ 0

Fig. 3. late.

~

L

I

,

,

,

~

I

0.5 ( Ao- A ) / A o

"~o 20

Test of grain boundary flow postu-

-l.-,

/

0

(1970) reported transport through

this transport to a form of regelation

/°

o/ , / . / o / O / /o/O

an ice sandwich apparatus and attributed in

which ice melted at the outflow phasebarrier,

/ ,o o

10

ICE SANDWICH EXPERII~NTS Miller

E u

1.0

00

I

I

10

20

discharging supercooled water into

I

, ,

30

I

I

40

50

Time(rain.)

the chamber beyond while fresh ice formed Fig. 4. Cumulative outflow with time, ice sandwich mode.

just inside the phase barrier on the inflow side.

Some have suggested that all

or part of the observed transport in temper-

of the chamber.

During construction of a

ate glacier near its melting point could be

new permeameter

for future use, we made two

attributed

to liquid flow along grain

interchangeable members whereby the diameter

boundaries

in polycrystalline

of the central chamber could be either 1.6

and Frank (1973), Osterkamp, Wakahama et al.

ice (cf. Nye (1975),

cm or 3.2 cm, with all else remaining un-

(1973)). We investigated

this possibility at -0.040°C.

changed.

We reasoned

Doubling chamber diameter should

double observed transport if peripheral

that such flow could be interdicted by em-

leakage were the sole mechanism of transport

bedding a non-permeable

but should quadruple transport by either

within the ice.

thin foil barrier

If the cross-sectional

area

of the chamber is Ao, and foil area is A, transport should be proportional

to (Ao-A)/A o.

regelation or grain boundary flow. at -0.040°C,

In tests

both with hydraulic gradients

of 1740, transport with the smaller chamber

Results of such a test are shown in Fig. 3.

was 1.49xi0 -5 cm3"sec -I, with the large

and are interpreted

chamber it was 5.89 x 10 -5 cm3"sec -I, almost

to mean that flow at

grain boundaries was negligible in compari-

exactly four times that with the smaller

son with other modes in this experiment at

chamber.

this temperature.

was dismissed.

It might also be suggested that observed

"The peripheral

leakage question

As pointed out by Miller, Loch and Bresler

transport was due to leakage of water a-

(1975), the regelation-transport

round the ice, between it and the sidewall

should be accompanied by development

mechanism of a

181

~ 1o-7

15

_ ICE

o ~~--/o /~

ICE SANDWICH

,/

u

~

c~, 10 E u

ld 8

-

o

O

O

O

o A "o

E

u v X

SANDWICH

i

h

%

L

,

,

,

I

L

,

,

- 0050 - QIOO Temperature ('C)

o

5

,

- Q150

Fig. 6. "Apparent hydraulic conductivity" of ice in ice sandwich as a function of temperature.

/ 500

1o(o)

1500

Hydraulic Gradient(cm H20/cm)

~en Fig. 5. Transport data at various temperatures and hydraulic gradients in ice sandwich mode.

distilled water from the laboratory tap

was used, flow rates tended to decay with time.

This water, condensed from heating-

plant steam, temperature peak at the inflowrface and a temperature

trough at the outflow face.

induced temperature differential proportional

to ice-flux.

organic solutes added as anticorrosion The

should be

Ice-flux,

is known to contain volatile

on the

other hand, would begin only when the

agents.

These are presumably removed when

the water is passed through deionizing cartridges. Hydraulic conductivity data

(shown in Fig.

applied pressure differential was large

i0) from two freezing sequences and an inter-

enough to overcome static friction at the

vening thawing sequence showed strong

ice/sidewall

hysteresis

interface.

Since ice pressure

effects and, perhaps,

evidence of

would increase as temperature was reduced

the appearance and persistence of small a-

(with water pressures held constant)

mounts of segregated ice at temperatures

the

threshold gradient for transport should become higher as temperature was lowered and the rate of transport, be lower.

once initiated, should

very close to O°C. Data for unfrozen water content, obtained in the dilatometer mode also show strong

The transport could be related to

imposed gradient by an "apparent hydraulic conductivity"

coefficient

0.~5

~CE S A N D W I C H

that would become

smaller as temperature was lowered.

Experi-

~o.~o

mental data illustrating all these effects are shown in Figs. 4, 5, 6, and 7. PEntAmETER

the permeameter mode.

0.~5

E w

EXPERIMENTS

Fig. 8 illustrates

¢ L

~

flow-data obtained in Fluxes at a given

gradient remained stable with time when deionlzed deaired water was used, Fig. 9. In contrast to Fig. 5, there was no detectable threshold gradient with soil present.

5 ~IUX

10x16 6 ( cm3/cm2,

se¢)

Fig. 7. Temperature differentials observed by thermocouples outside phase barriers in ice sandwich mode as a function of observed fluxes at various temperatures and with various hydraulic gradients.

182

15 - x l ( ) 3

///

-,I(~ 7

FROZEN SOIL ( 4 - 8 H) - 0.1 1 7°C

....10

FROZEN SOl L ( 4 - 8 ~J) - 0.117°C

7

.// " ¢/

,,/.~_,,~

o/ ,/,o

6

,-j

E

U v

//i~ "~'~

0

~:3 0

7°../°

E E

5

u v

// o /

><.3

E 2~ [#~

0

a"O"'O

0

I

I

I

I

I

30 Time ( mi n.)

60

I

/

o

I

hysteresis, possible sion.

Fig. ii, and again evidence of

ice segregation prior to ice intru-

I

I

5OO 1000 1500 Hydraulic Gradient(cm HL=~)/crn)

Fig. 8. Cumulative outflow vs time, frozen 4-8 um silt.

Fig. 9. Transport data at various hydraulic gradients in permeameter mode.

This evidence is the failure to

either hysteresis

loops to close at some

temperature significantly above 0°C together

opposite sides of an incompletely ted sample.

consolida-

A redesigned permeameter is

with a slight decrease in bath water content

intended to allow substantial preconsolida-

and hydraulic conductivity before ice intru-

tion of the sample during the filling

sion at the knees of the curves.

process but this design has not been tested.

In the permeameter mode, induced tempera-

On the whole, however,

first order behavior

ture differentials were observed whenever

of the system was satisfying,

flow direction was reversed but the signal

suspected second order effects could not

diminished rapidly and after a time became

have been noticed.

lost in the noise. ~y

We do not understand

this should be true.

be substantially

otherwise

The signal should

smaller than that observed

CLOSURE A permeameter based on the ice-sandwich

in the ice-sandwich mode but if it appears

principle,

at all it ought to remain constant unless

cooled water is practical at temperatures

we have problems with segregation of un-

in the range 0 to -0.15°C and perhaps to

wanted solutes or unless, perhaps,

much lower temperatures.

the

very thin lenses of segregated ice on

Results to date

confirm some aspects of an analysis of ex-

initial signal is associated with the formation and concurrent disappearance

using phase barriers and super-

of

pected permeameter behavior

(Miller, Loch

188

i(~~

FROZEN Seeded ~. ,L ~q-Ao- A - o--A--A-o-,~-"-~

40 -

SOIL

(4-$

FROZEN SOl L

Seeded

•

H)

o

(4

o

-

8

~)

i

i

E 30 -

\

E u

Unfrozen o

T, 157

:

•

o 0

1st c o o l i n g : o

\

2nd c o o l i n g :

E

Warming

o

:a

20-

u

g

1D tO

°\\

O 16@_ u_

"o

a

@

~

O

10-

0

I

Oo

,

,

,

Temperature

~#0

I i

I I i

ii

0

I

- Q050

Temperature

, t -0.100

-0.150

[

*

i

I

i

(°C)

Fig. ii. Unfrozen water content, 4-8 ~m silt, as determined with permeameter in the dilatometer mode.

(°C)

Fig. i0. Apparent hydraulic conductivity as a function of temperature, 4-8 ~m silt fraction.

MILLER, R. D., J.P.G. LOCH and E. BRESLER (1975).

Transport and heat in a frozen

permeameter. and Bresler, 1975) but other aspects remain unconfirmed.

,

-0.100

Further development and

Soll Scl. Soc. Amer. Proc.,

39:1029-1036. NYE, J. E. and F. C. FRANK (1973). Hydrology

testing of the system is necessary and is

of the intergranular veins in a temperate

now underway.

glacier.

Publ. No. 95, Int. Assoc. Scl.

Hydrology, 157-161. OSTERKA}~, T. E. (1975).

Structure and

properties of ice lenses in frozen ground. REFERENCES

Proc. Conf. on Soil-Water Problems in

BURT, T. P. and J. P. WILLIAMS (1974).

Cold Regions, Calgary, Alberta, Canada.

Measurement of hydraulic conductivity of frozen soils.

Can. Geotech. J. Ii,

647-650. MILLER, R. D. (1970).

WAKAHAMA, G., D. KUROIWA, D. KOBAYASHI, K. TANUMA, Y. ENDO, Y. MIZUNO and S.

Ice sandwich: Func-

tional semipermeable membrane. 169:584-585.

89-111.

Science,

KOBAYASHI (1973).

Observation of perme-

ating water through a glacier body.

Low

Temperature Science, Ser. A. 31:219-221.