Contribution to the Study of Ice Lens Formation in the Ground

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Contribution to the Study of Ice Lens Formation in the Ground Daxelhofer, J. P.

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The mechanism involved at the frostline during frost action in soils is still not completely understood although much progress has been made in recent years. The Division of BUilding Research shares the view that such fundamental studies are ,necessary as a basis for establishing effective frost action criteria.

The research carried out' by the Division in the field of frost action has been guided largely by the principle and is currently .engaged in evaluating the forces involved and the mechanism at the ice-water interface in a freezing soil. The paper by Mr. Daxelhofer is therefore of interest, parti-cularly since the technique used in growing ice lenses is unique.

The Division is grateful to Mr. D.A. Sinclair of the National Research Council's translation staff for making the

translation.

Ottawa

Technical Translation-?2l

Title: Contribution to the study of ice lens formation

in the ground

(Contribution a ｬＧｾｴｵ､･ experimentale de la

formation de lentilles de glace dans Ie sol)

Author: -J.P. Daxelhofer

Reference: Bulletin Technique de la Suisse Romande, (22):

3 -

10, 1946

FOR}iATION IN TijE GROUND

Introduction

During the past ten years the Geotechnical Laboratory of the Ecole Polytechnique of Lausanne has frequently been asked to study the foundation soils of roads and aircraft landing strips.

By determining such properties of the soils as grain size composition, liquid limits, plastic limits, compress-ibility, cohesion, angle of internal friction, etc., it has been possible in almost all cases to advise the builders

fUlly of the inherent dangers to be encountered and the means of avoiding or minimizing the risks of having their work

ruined either by the harmful effects of water or ice or as a consequence of overloading*.

I

*

In this ·connection see: Ｂｐｲｯ｣ｾ､･ｳ modernes d'etude des sols de fondations des chaussees, gelivite des sols" (Modern methods of studying road foundation soils;

frost-suscept-ibility of soils) by A. Stucky and D. Bonnard, Bulletin

technique, 26th March, 1938; "Gelivite des sols et fondations des routes" (Frost-susceptibility of soils and road foundations", thesis presented to the Engineering School of the University of Lausanne in 1943 by R. Ruckli, engineer at the Federal Inspectorate of Public Works; "Les fondations des chaussees" (Road foundations) by L. Perret, chief engineer for the

Canton Road Service, Lausanne, Bulletin technique of the 23rd December, 1944; "Les travaux d1agrandissement de

l'aerodrome de Cointrin" (The Cointrin airfield expansion oper-ations) by E. Lacroix, Canton engineer, Geneva, Bulletin

Parallelling this development of cooperation between the laboratory and the builders (a cooperation which extends into other fields such as settlements, slides, location of embank-ments, etc.) our institute is striving to create the facilities and a favourable climate for research and to encourage research by making available the necessary materials and aid to those who wish to devote themselves steadfastly to the advanced study of special problems. Thus in recent years it has reserved a large part of its activity for the development of new methods and apparatus for studying the frost-susceptibility of soils. The laboratory has a large cold room in which samples of soil can be subjected to the action of frost under temperature and humidity conditions identical with those of nature.

For many years numerous authors have sought to explain the phenomenon of ice lens formation in soils and to develop a laboratory technique whereby accurate information on the extent of the danger might be derived from a simple and rapid examin-ation of samples.

The Geotechnical Laboratory of the E.P.U.L. during

1945

was fortunate in obtaining the assistance of Mr. J.P. Daxelhofer, an engineer whose work, undertaken under our direction and assisted by the personnel of the laboratory, and in particular by Mr. M.J. Bonjour, engineer, has produced decisive results. In our opinion this publication of an, extract from the report

written by Mr. Daxelhofer himself and giving a brief account of his researches is an obvious step. In it the author expresses

certain decidedly personal points of view and his conClusions, to some extent still provisional, will be subject to further checking. The Institute is currently engaged in these studies and will be happy to collaborate with any other institution or

individual Who may have' had occasion to carry out experiments or to make interesting new observations in this field.

" ••••• the remarkable phenomenon .•.• of water passing from a region of less than atmospheric pressure in the wet pores of the earth, into a place and con-dition in the base of the columns of ice where it was subject to more than atmospheric pressure •••.••

appear to involve considerations of scientific

interest and to afford scope for further experimental and theoretical researches."*

James Thomson, 1871 The formation of layers of pure ice in a water-soaked soil underlies the heaving of roads due to frost. The various

phenomena which accompany the freezing of soils or construction materials and produce changes in their physical 'and mechanical properties are known as frost-susceptibility.

Frost caUSes serious and costly damage every year to the surfaces of modern roads. It is also frequently the cause of surface slidings of natural or artificial slopes. It modifies certain constructional rocks and even certain concretes(l). Many tests have been made in laboratories allover the world With a view to isolating the various factors involved so that precau-tions might be taken against these harmful effects. .

S. Taber(2) was the first to obtain pure ice lenses experi-mentally (segregation phenomenon) (Fig. 1). There are various rules for judging whether a terrain is frost-susceptible or not and subsequently many research workers obtained lenses of ice or even of substances other than ｷ｡ｾ･ｲＮ However, the conditions of their formation are not yet well understood. It is not

possible to tell where and when an ice lens will form nor to pre-dict their thickness or number.

Taber has already given a tentative explanation of Why the formation of successive ice lenses is discontinuous while the observed heaving is continuous.

*

Collected Papers in Physics and Engineering. Cambridge, 1912. p.271

We were fortunate in being able to produce these lenses in certain special cases. It is thus possible hereafter to deter-mine the conditions of their formation and an important step has been made in the study of this complex phenomenon. This result was obtained with a new experimental apparatus. We therefore deem it useful to describe the apparatus most often used for these frost-susceptibility tests in the field and the new test which makes the observation of these phenomena easy.

All the tests since Taber have been carried out essentially on cylinders of soil, one of the bases of which, generally the upper one, is subjected to cold, while the ｯｴｨ･ｾ is kept at a temperature above 0°, depending on the case. The lower base is generally immer.sed in water in order to ensure a supply for the formation of the lenses. The soil cylinder is contained in a continuous or discontinuous (rings) tube of impermeable paste-board or glass (Fig. 1 to

5).

Continuous cylinders ,must be lub-ricated with a non-freezing substance. They have the advantage of maintaining the soil in a state of constant capillary

attraction. This is not the case if superimposed rings are

used. As soon as a ring is raised as a result of heaving of the soil which it contains, a lateral attraction sets in which is added to the preceding attractions.

These supplementary attractions appear to disturb the phenomenon and give rise to horizontal oracks

.

｣ｯｲｲｾｳｰｯｮ､ｩｮｧ to the rings, so that at the elld of the experiment it is difficult to say whether some of the ice lenses (Fig.

2,3,5)

were not produced in these pre-existing cracks.

Another disadvantage of this experimental system is the difficulty of filling the cylinders homogeneously. Generally speaking, the 'cylinder or stack of rings is filled carefully in successive layers and the powdery soil is then saturated by cap-illary action so as to eliminate air bubbles from the interior of the test cylinder as far as possible. In the case of fine, clayey soils the saturation process is extremely slow and may take

several weeks. It is quite possible that this system will produce discontinuities in the interior of the cylinder.

Finally, if compressed samples are used the state of attraction is modified when the sample is placed in contact with a sheet of water.

Observation of the ･ｸｰｾｮｳｩｯｮｳ and of the formation of any

lenses of pure ice can scarcely be carried out except in a

discontinuous manner. These tests take a long time (several days).

The sample is placed in a cold room where its observation is

neither conventent nor comfortable. If it is taken out for

ex-amination or, to take measurements the thermal conditions are

modified considerably. In general, the receptacle (cylinder or

ring) is not ｭ｡ｾ･ of transparent material, or if it is, it very

easily becomes covered ｾｊｩｴｨ frost or ice, which prevents or

hinders observation. It is easy to mark the position of the

various lenses, the depth attained by the ice and the heaving,

which are the principle elements involved in ｴｾ determination

of the coefficients of frost-susceptibility. However, it is very

difficult, if not impossible, to examine in detail the formation

and growth of a lens. Only the final state is perfectly clear

and well-defined, ｢ｾ｣｡ｵｳ･ in general the sample is cut along a

diameter. Owing to the nature of the experimental set-up itself

the tests can scarcely apply to any soils except those whose water

content is in the vicinity of or slightly higher than the liquid

,

limit. It is clear that if we wish to use the same experimental

apparatus for fluid soils or suspensions, then ､･｣｡ｮｴｾｴｬｯｮ on the

one hand, and consolidation of sediment on the other, would result in a certain heterogeneity of the sample·.

*

Actually road foundation soils are not fluid - except during a

thaw if they are frost-susceptible - but it is interesting to be

able to make tests with very variable water contents and to examine what takes place in the limiting cases.

New Experimental ApparatuB

The apparatus used for our tests is extremely simple. It consists essentially of a kind of a cylindrical saucer about

20 cm. in diameter and

4

to 5 cm. deep. A freezing tube (Fig.

6)

is attached along its axis. This tube is attached with aid of a layer of material which conducts heat rather well, so as to ensure a regular thermal flux around the tube. The soil to be studied is placed above this layer. A freeZing mixture is introduced into the central tube (which is made of metal and is a good conductor of heat). Depending on the case, the layer of so'LL mayor may not be covered by a layer of water, i.e., the test may be made \'li th or without 1nvolving capillary phenomena.

The rate of propagation of the ice radially around the tube is noted (Fig.

6).

This experimental system affords the following advantages:

1. Easy filling with any degree of homogeneity desired (thin layer) •

2. The possibility of following the progress of the frost con-tinuously and noting the appearance of lenses or cracks at any point in the sample under examination.

3.

Rapid testing if a freezing mixture of very low temperature is used. (It takes from two to three hours to freeze a thick-ness of approximately

5

cm. around the tube, depending on the nature of the soil being considered.)

4.

Possibility of observing the effect of any discontinuity or foreign body (Fig.

7, 8

and

9)

within the test soil.

5.

Possibility of carrying out tests with very high water contents and stable suspensions, as well as with comparatively compact

sotl.s ,

6.

By slightly modifying the set-up previously employed it is possible to make freezing tests with a soil placed in a given state of attraction while assuring a supply of water.

Chief Results Obtained to Date

A. The most interesting result is the obtaining of ice lenses at a definite point (Fig.

6).

The occurrence of an ice lens appears to be associated with a short period of thaw.

Measurements of the temperature will enable us to elucidate this very important point and to determine the optimum thermal gradient for the formation of an ice lens.

B. The study of the effect of suction of water on the formation of cracks. We have observed four types of cracking:

(a) The radial shrinkage cracks which begin at the boundary of the ｾ｣･ are propagated to a ｣･ｲｴｾｩｮ distance beyond, corresponding to the zone affected by the water suction. These cracks may occur just as well under water as when the soil is more or less saturated (Fig. 10 and 14). (b) The radial shrinkage cracks which occur in the

peri-pheral frozen zone. These cracks, which are much finer and much more uniformly distributed than the above cracks, also ｯｲｩｧｩｮｾｴ･ as a result of a shrinkage phenomenon

which must be related to the fact that only part of the water contained in the soil is frozen at a certain temp-erature; as the ice expands, the temperature decreases and an even greater proportion of interstitial water

freezes (Fig. 12). This wat'er is bound more firmly by the molecular forces (adsorbed water) to the grains of soil and apparently does not behave like natural water with respect to heaving following the transformation from the liquid to the solid state.

(c) Radial cracks due to heaving produced by the frost appear at the perimeter of the sample in question at the points where the relative elongation is a maximum (centripetal cracks) .

(d) Radial cracks which tend to grow gradually and which originate immediately outside the frozen zone, but are not propagated far beyond it. These cracks are noted

in the frozen zone and increase as freezing progresses. This phenomenon is particularly evident in laminated soils with a high water content (Fig. 14).

c.

The formation of layers of pure water in soils with a high water content following a thaw (Fig.

15

and 16). ｾｨ･ｮ

freezing has reached a certain limit and refrigeration is stopped the following phenomenon is observed:

At the edge of the frozen zone, as soon as thawing occurs, a separation ｴ｡ｫｾｳ place between the frozen zone and the adjacent

soil with the appearance of a layer of water. If melting is per-mitted this separation increases gradually. Everything takes place as if the solid particles contained in the ice can no longer escape.

In this way we obtained layers of water up to 4 mm. thick. The same phenomenon occurs around the tube provided it is made of a metal of high thermal conduction and the test is carried out at room temperature.

D. Frost exerts a very clear physico-chemical effect on

soils. This must involve a very marked deflocculation (Fig. 16a). The texture of the frozen part is no longer the same as before and if this soil is refrozen different phenomena are observed.

E. Effect of discontinuities. Various foreign bodies were placed perpendicular or parallel to the isotherms. The following observations were made:

In the presence of frost-susceptible materials having a

structure which. is probably laminated in a certain direction, the observed heaving is very considerable when the body is parallel to the isotherms (Fig. 17). If it is placed radially to the isotherms the heaving is much less evident or it is zero, but a crack or

rupture occurs perpendicular to the la'linations. If the foreign body is of a homogeneous nature and a good conductor of heat,

placed radially the direction of the isotherms is modified and a segregation of pure water gradually takes place (Fig. 8). However, when the same metallic object is placed perpendicular nothing special happens. If the metallic object is fairly large, the deformation of the isotherms is considerable and the foreign body is gradually pushed away until the amount of cold is suffi-cient for the frozen zone to be surrounded (Fig.

9).

In certain frost-susceptible soils a cylindrical hole

develops and becomes elongated in the direction of propagation of the cold (a phenomenon already observed by Taber). This i8 the start of a crack. A hole of 2 mm. diameter becomes 4 mm. long. A groove occurring at the frost limit parallel to the isotherms becomes Wider and gives rise to shrinkage cracks. (The width of the groove grows from 1 mm. to

5

mm.).

F. The freezing of suspensions or colloidal solutions. Various experiments have been undertaken to discover whether the phenomena are not clearer or exaggerated in. the presence of more or less dense dispersions. The following are some results ob-tained with more or less dilute suspensions or gels:

(a) A suspension of 10% bentonite freezes and forms a clearly visible radial crystal structure. The surface of the

frozen part does not remain smooth; it is finely creased. While freeZing continues, no interruption is observed, but the cessation of freezing produces very clear rings

(Fig. 18 and l8a). A separation also appears to take place in the radial direction and the texture has a characteristic appearance (Fig. 19 and 13).

(b) Pure ice lenses were obtained with a liqUid paste of slaked lime consisting of very fine particles (-50% ＼ｬｾＩＮ

(c) A silica gel was destroyed by freezing, but despite its fragility no crack appeared.

(d) The presence of grains of sand does not prevent the form-ation of discontinuities (Fig. 20).

crnst takes place and tangential phenomena occur which involve only this crust (Fig. 21).

A similar phenomenon was observed on the surface of the slaked lime.

(f) The deflocculating effect of freezing is very clear in dilute suspensions. After thawing, an original thickness of 10 mm. is reduced to 3 mm., but only in the thswed portion. The intersection of the two zones remains per-fectly clear and vertical, showing that the heat propa-gation-is uniform (Fig. 16a).

(g) When a layer of pure water has been obtatned by thawing and then the system is refrozen, we note that the outer wall marking the extreme limit attained by the frost cracks slightly before the ice has rejoined this wall. There is a sort of repulsion produced by the pure ice.

In this way a groove of

4

mm. was widened to 5.5 mm., i.e., an increase of 1.5 mm. This repulsion effect 1s probably

responsible for the pure ice rings observed at the bottom of the frozen "cakes'! (Fig. 22). In fact, on thawing the solid grains flow out of the groove as a result of the deflocculating action of the frost. When the sample is refrozen this repulsion phenomenon is observed to a cer-tain degree which no doubt also depends on the thermal gradient, and this also explains the formation of the lower rings.

The Mechanism of the Formation of Ice Lenses

We do not wish here to give a complete explanation of this mechanism. As ｾ｢･ｲ already remarked in 1930 a more accurate know-ledge of the constitution of water and its properties near the

freezing point, as well as in the thin lIfilms" adsorbed at the sur-face of solid grains, is needed in order to get at the heart of the mechanism.

The explanations proposed by various authors are convenient pictures where very often different names are given to the same things. Only the mathematical expression changes. We shall leave it to the physicists to decide whether these are forces of co-hesion, capillarity, crystallization, adsorption, etc.

On the basis of the facts observed we may state here that: 1. For a lens to form and segregation of ice to take place apparently a period of melting, however brief, is necessary, at least under our experimental conditions. Perhaps only a very slight thermal gradient is involved which we hope one day to measure.

2. This melting, because of the ability of ice to adsorb particles, salts Qr gases when it melts and to repulse them when it freezes, gives rise to a film of water which we have observed re-peatedly in the course of our many tests.

If freezing is resumed a layer of pure ice is formed and tends to grow if favourable thermal conditions are satisfied.

3.

In certain soils it is not possible to obtain a unique, well-defined lens. A series of more or less fine adjacent lenses is produced, resulting in a ｭｯｲｾ or less tightly packed striated texture

(Fig. 23). This appears to be associated with the grain size of the material under consideration. Since coarse grains are not affected by ice no continuous layer of water can form. All research workers have noted that the finer the soil, the easier it is to obtain the

segregation of pure ice. Taber states' that below 21.J. (except in the case of quartz) the formation of pure ice lenses is easily obtained in the laboratory provided the thermal and hydraulic conditions are favourable. (It may be stated for the sake of accuracy that they form by themselves and that they can be observed, but to date it has not been possible to reproduce their formation.)

Another factor which is involved as soon as the grains exceed a certain size relative to the ice crystals, is that of heat transfer; while it is uniformly propagated in a fine soil, this is no longer the case, even locally, when there are grains. The latter are

generally better conductors of heat than water; their temperature

attains 0° before the pore water. They become surrounded by a

layer of ice and the transfer of cold then takes ｰｬｾ｣･ radially

about the grains, and no longer in a single dimension.

4.

The finer and more permeable the soil, the easier it

is to produce the formation of lenses.

It is apparent that the theory of the growth of lenses by feeding through films of adsorbed water leads to false conclusions.

In fact, if the circulation of the water molecules is due to

the films of water adsorbed at the surface of the fine grains it must follow quite naturally that the thicker the film thp easier will be

the formation of lenses and their growth. However, this result of

the hypothesis is 'contradicted by the results of our experiments and by those of Ducker.

It is difficult to obtain ｬ･ｮｳ･ｾ in a bentonite suspension of

10% solid matter. Very thin ones do form (see Fig. 18 and 18a) but

they do not grow. This is because the adsorbed water is molecularly

bound to the solid grains. This particular structure is broken only

by mechanical agitation (thixotropic effect). These gels have little

permeability, despite their water content of 1000% (by weight, rela-tive to the solid matter).

The same observation is made with silica gels.

The fatter a clay is, and the thicker the water films

ad-sorbed at the surface of the grains, ｴｾ･ more impermeable it will be.

Ducker has also shown, in reiteration of certain results of Endell and his co-workers, that the heave due to freezing is greater

for quartz powder than for kaolin, and greater for calcium bentonite

than for sodium bentonite. For a given grain size, the thinner the

water films or, what amounts to the same thins, the smaller the chem-ical activity of the grains of the soil, the more frost-susceptible the soil will be.

Ducker carried out freezing tests on various mixtures contain-ing nine parts of ground quartz to which was added one part of kaolin,

or one part calcium or sodium bentonite. The heaving decreases quite noticeably from kaolin to sodium bentonite.

Our type of experiment makes it possible to follow this phenomenon quite easily. If the soil is permea.ble a lustreless ring forms around the frozen zone due to the water suction. This aureole is absent in a suspension of bentonite, is a maximum with quartz powder and is very noticeable with kaolin.

ThuG in our opinion it is not possible to explain the feed-ing of water to the ice lenses by the adsorbed films of water around the grains. Rather, it must be the free water which is ｡ｴｴｲｾ｣ｴ･､

and the less adsorbed wat.er- there is the easier will be the forma-tion of the lenses.

This fact, moreover, is supported by common sense consider-ations. The finer a soil is, and at the same time the more permeable, the more frost-susceptible it will be.·

This explains why calcareous soils are more frost-susceptible than others. Calcium has a very marked flocculating effect. Agri-culturists are very familiar with the effects of a lime on the so11. A clay is more permeable and less plastic if 1t is saturated with lime; it is therefore more frost-susceptible.

The greatest heaves obtained in our work occurred with a powder originating from the decomposition of a calcareous Jura rock known as "pierre morte" (apnroximately 85% carbonate attacked by Hel - heaVing, 4.5 mm. per hour - water content of frozen part up to 177% - heave factor 120%). The length of the shrinkage cracks in

Fig. 10 shows the distance at which the water 1s attracted by the ice. Erlenbach* notes that soils in which maximum heaves of 50 to 60 cm. have been observed are calcareous. With respect to the initiation and cessation of the formation of an ice lens, i.e., the explanation of the discontinuity of the phenomenon, only the cessation was ade-quately explained by Taber.

*

See Bodenmechanik und neuzeitlicher strassenbau no. 3, 1936,

page 55, rood over embankment of 0.80 ID. water table at 1.40 m. depth; muddy "Wiesenkalk" SOil, 60% calcareous content. Drains at a depth of 0.50 m. were quite ineffective.

The water attracted by the ice lens is under tension**.

When the resistance to traction exceeds a certain value g break

in the liquid phase occurs and a gaseous phase is formed resulting in menisci, and consequently the circulation of the water ceases. The tensile stress decreases instantaneously to the point where

there are no lonGer any losses of load. The tests made with liquids

other than water appear to confirm this hypothesis.

Besl{ow arrived at a similar result. However, he does not

consider that it is the resistance to traction of a liquid which is

involved, but rather the maximum height of capillary ascent. Since

the idea of maximum of capillary ascent is difficult to define,

there being both an active and a passive height of capillary ascent, and hence a certain lack of definiteness which is difficult to ro-solve from experience in this case, it is very possible that the explanations are basically the same.

What is less satisfactory, however, is the explanation of the

origin of a lens. The ｦｯｲｾｾｴｩｯｮ of crystallization nuclei,

pre-existing continuities in the soil, etc., are offered as possibilities. But all these explanations relate only to the formation of a single

lens and not a succession of them.

In our opinion, and on the basis of our own observations, we think that the formation of a lens is due to a modification of thermal state alone, provided all the other conditions are equally favourable.

All the lenses which we succeeded in producing and causing to ,

grow were associated with a rise in temperature, or, ｾｬｨ｡ｴ amounts to

the same thing, vlith a basic modification of the thermal gradient at

the boundary of the frost zone. The ice itself becomes stratified if

the temperature is sUbjected to fluctuations (Fig. 24).

It would be of very great importance to obtain more accurate detail on the treatment to which the samples cited in the literature and showing very fine lenses were subjected, in order to know whether there was any possibility of warming during the observations.

COl1clusions

The type of test described with a central freezing tube

｡ｰｰ･ｾｲｳ to us capable of rendering useful service in studying the

frost-susceptibility of soils;

To the best of our knowledge this means has enabled us for the first time to cause the formation of ice lenses.

The formation of successive lenses appears to depend on

thermal variations Nhich bring about thawing at the boundary of the frozen zone. This thawing apparently promotes the formation of a discont inui ty. The phenomenon is probably a s soc i.at.ed ..1ith the properties of melting ice.

It does not .seem possible to attribute the supply of water for the ice lens to the presence of films of adsorbed water around the grains.

Some tests seem to indicate that vibrations favour the form-

,-H' Jon of discontinuities, and sy-stematic tests on this point are

desirable, since this is an important factor in connection with modern roads.

The results of tests of this kind also contribute to a better knowledge of the behaviour of soils for the case of artificial

freezing of soils, in particular for the excavation of mine pits. We are not unaware of the fragmentary and ｱｵ｡ｬｩｴｾｴｩｶ･ nature of these experiments, but we are making them accessible to all labor-atories in the belief that they constitute a useful basis for later researches of a more systematic nature.

The author of the present article Wishes to express his gratitude to the director of the Ecole Polytechnique, Mr. A. Stucky, for haVing given him the opportunity and means of carrying out some very interest-ing experiments and for haVinterest-ing authorized publication of these pre-liminary results.

He is particularly grateful to Mr. D. Bannard, engineer, supervisor of courses at the Ecole Poly technique and associate director of the Geotechnical and Hydraulic Laboratories, for his kind and persistent support as well as for facilities of all kinds granted him in the course of work, and also to Mr. J. Bonjour, engineer, as well as all their co-workers.

References

1. Bo10mey, J. "Recherches et essais sur 1es ｢ｾｴｯｮｳｮ

(Researches and experiments on concretes). Bulletin Technique de 1a Suisse Romande, July 28, 1945, p.206. 2. Taber, Stephen. 1 - Ice forming in clay 'soils will lift

surface weights. Eng. News Rec. 80: 262, 1918;

2 - Frost heaving. J. geology 37: 428, 19 29. 3 - The mechanics of frost heaving. J. geology, 37: 303, 1930. 3. Bishop, D. Particle size and pasticity of lime. Journal

Fig. 1

Ice lenses obtained by Taber in 1930. The

sample was placed in an ｾｭｩｮｴ･ｲｲｵｰｴ･､ cardboard cylinder. I:: 0

ｽｾ

.... ｾＩ ,j III v ｾ .r. » ... 1Il-t

..,

_.... ... c! Ul oJ .ri ｾ I::; ... o oM III IJC ｾｾ lot ...._,., <I, o 0 0

...

M Fig. 2

Heaving obtained in the Lausanne laboratory with a "Pierre Morte" (calcareous Jura rock) sample placed in a lubricated, transparent cylinder. Moisture content in the unfrozen part

28.5%;

in the lower frozen zone 177%; in the central frozen zone 100%;

ｾ ｣ｲｾ｣ｫ

Fig.

3

Experiment with some quartz powder placed in a

cylinder made of superimposed ｲｬｮｾｳ the heights

of which are 1 em. Note the crack. Initial

thickness

3

em., final thickness

-4

em.

Fig.

4

Detail of Fig.

3.

Note the ice lens and the

irregularity of the shearing surface corresponding to the fissure.

Fig.

5

Heaving of "Pierre Morte" (calcareous Jura rock). Thickness of the rings 1 em.; the arrow points to

a crack in which ice crystals are developing.

Fig. 6

General view of the new testing apparatus.

1,2,

3,4:

successive lenses 8 mm., 15-16 mm., 22 mm., and

39

mm. from the tube (width of the 2nd lens = 1 mm.) -

5:

radial shrinkage crack - 6: influence limit.

-7:

frost limit,

Fig.

7

Freezing experiment with a bentonite suspension containing frost-susceptible heterogeneous particles which were already

laminated. On the left-hand side the sample, parallel to

the isotherms, heaved from 8 mm. to 14.5 mm. The right-hand

sample, which was placed radially, showed a very small heave

from

6

mm. to

7.5

mm.

Fig. 8

Effect of a metal blade (aluminium a good conductor)

placed radially. Note the ､･ｦｯｲｭｾｴｩｯｮ of isotherms.

Fig. 9

The ice has pushed the metal blade back. Note the sliding beyond. Near it the lenses are de-formed and are parallel to the blade. Shrinkage

cracks towards the centre.

\

.I

Fig. 10

"Pierre Marte". Radial and centrifugal shrinkage cracks. Lenses 11 mm. from tube; ice limit at

15•

.5 mm. WL

=

22·3% W L = liquid limit W_p = 21.4% W

=

plastic limit p

Fig. 11

Kaolin. Radial and centrifugal shrinkage cracks and pure ice lenses.

w

_p

=

34%

ｾｬ･ｮｳ

Fig. 12

Kaolin. Radial shrinkage cracks in the frozen zone

•.·••.•,.·•.··:'.'•..•.•.·.•·tf..•.•·.··: ·•...••.,..••..-....••...•.".\t..'},,,,

ｾ

' .•••:.'.).•••.. '....•..'

Ｚｾ｜

｜Ｇｾ .•...•..

ＧＮ｜Ｎ｜ｾ

.v ,..\..

ｾ

" \ > '.•...•\ •...•

ｾ

....•... ,lｾＢＢｾＢＱＭ r:rl ,,' ''\- \ \ , . j ( ' . \ \ \ ' ",' i - \ • J .J \ V · , " " , , I f ｾ .. ;, Ｎ｜ＬＬＬＮｾ '• . •ｾ

•.

ｻＬＮｉｫＮﾷＮｾ

..•

J1

..

ｾﾷＢ

...

ｾｾﾷ ＮｾＮｾＮｾＮＢ

";1.

ｾｦＮＬＮｾＮＬ｜

.•

Ｚ［ｾ

.•••.•...•...

ｾ［

.... -.... s.,

ｾＮＧＧＧｙ

•.

??J.{

t,

ＬＮ｜ｾＮｾＺＮｾ

ｾＧ｜ＩＧ｜ｾＮＬＮｊｾＢＧｾ ...A'\'•..

ＬＮＬＮＮ｜［ｾＬ｜ｾＮＬｾｾＮ

··.w

x..'..

ｾ

•.

ｾﾷＺＺﾷｾＺｉＺｾﾷｾＮ｜ＮＧ

1

ｾｾｾＧＮ｜Ｇ

.•• , .•ｾＮＢ ·.1 """-:" .. ｾ ｜｜ｾＧｉ［

..

.'

, .... ,*"., '

.. .'\ \\

\,

Ｇ｜ｾ｜Ｌ｜ ｜ｾ ( ..-...., ...,., . . . . ... .;; \

.' ' ,'"

\"" .

Ｇｾ｜ｾ Ｈ｜ｊｾ

",

....•.•.iJ::::-.

_;J.-l_-"t"'"...., ) I . j

ＮＺｾ

_ｾ

.. " '"

_{::<"<1'7 ,'.' .'- ,-}

t···.·'.'-"". '.'- -.

_ｾｾ. . , )_{ｾＧＭＧＬｊＮ ...-ｾｲ} .r.,_{ＧＺＧｾ y-\." --}····M·....ｾ｜Ｎ•....•.' .•

ＢｾｾＺＭＮＧｋＺ , ＬＮＡｾＬ

_l! 'I_{\ "'.}..'•...•.•

.'.". -_..

ｾＮＬＺＬ

... " "1 .'....

ＢＧＮ｜Ｎｾ ｾ｜Ｎ｜ＮＧ

.. '. "..

... ' .. \...,---) ..•, '1."\ j ..." '(" \ \ .•｜ｾ｜＾Ｎ , " , ",- .. -\. .o , -'''I':.; ' , , ' ｟ＭＢＧＭＺＬ｜ｾ｟ｾ［ＧＭＬＮｬＭＧＭＺＭＬＮｦ ＧＨＩｾＧ \ ,I ' ｟ＮＬｾＮＬ ｾＢ｜｜Ｌ｜Ｌ｜ｾ｜｜Ｎﾥ Fig.

13

Typical structure of a suspension of bentonite (section normal to direction of propagation of

the cold). Black zones are pure ice.

Fig. 14

Fig.

15

Lenses and cracks obtained under water.

Fig. 16

Pure ice lenses resulting from thawing and refreezing. Variable width

6.5

to

7

mm.

Fig. 16a

Experimental sample after air drying, showing:

1) Deflocculating effect of the ice on a

kaolin paste, 100% water.

2) Uniform radial propagation of the cold. The difference in the two levels corres-ponds to the frost limit.

3)

The crack seen beyond shows the limit of the zone affected by the water suction towards the frozen zone (test performed

with a thin layer of water over the kaolin).

Fig. 17

Hetergeneous body placed in a suspension of bentonite, radially and at the circumference. The 2 mm. crack outlines the frozen zone. Note the irregularity of the

Fig. 18

Very thick thixotropic suspension containing

5%

bentonite and

5%

Portland cement.

Fig. l8a Freezing and formation

suspension rings

of bentonite

(10%)

Fig. 19

Side view at frost line (test Fig. 18a)

Fig. 20

Discontinuity obtained in a bentonite suspension containing coarse sand

Fig. 21

When there is a crust, freezing produces a displacement. Below the undulation the surface of the soil remained horizontal.

Fig. 22

Fig.

23

Soil in which there are no well-defined lenses.

Fig. 24

Stratification obtained in ice due to thermal variations.

on the left hand side: distilled water on the right hand side: drinking water