1 INTRODUCTION

Frozen saline soils are among the most common fea-tures of the Arctic coast (Velli 1980, Hivon & Sego1993). They are also distributed in other regions, suchas Central Siberia, where “continental” salinization iscaused by predominance of evaporation above precip-itation and is characterized by prevalence of the sul-phate and carbonate ions (Brouchkov 1998). It has beenshown that frozen saline soils have special propertiesand are characterized by low bearing capacity (Velli1980). They occupy the position between frozen andunfrozen soils because they freeze at lower tempera-tures and contain more unfrozen water than the samesoils without salts. Frozen saline soils are distin-guished by their physical characteristics, deformability,and other properties.

Frozen saline soils are identified as those containing0.05% by weight of soluble salt compared to a dry soil.The definition is based on the measurable change ofmechanical properties; an example is illustrated inFig. 1. Salinization is the accumulation (as an accu-mulated mass or quantity formed) of salts in the soil(Oxford English Dictionary 1989); “salinization” isalso a translation of the same term from Russian.

The term “salinization” (salt weight content in 1 gram of dry soil, %, Dsal) from our point of view ispreferable for use because the salt content of pore water(“salinity”) of the same soil varies with temperature.

The geotechnical conditions of the Arctic coast arecomplex due to low temperatures and wide distributionof saline and ice-saturated soils. Construction practicecould be observed in small settlements: some of themhave a long history. Construction of these settlementsbegan in the 1930s and 1940s.

The so-called first principle of construction is usedin territories with continuous distribution of frozensoils, i.e. the preservation of the frozen condition. Thisprinciple has obvious advantages in comparison to the

principle of preliminary thawing (principle two). Inthe majority of cases, frozen saline soils on the Arcticcoast are characterized by continuous long-term defor-mations. This was observed in a group of houses inAmderma, Dikson, Tiksi and Pevek; these housescontinued to deform over a period of 20 years. Super-vision of over 14 buildings was carried out in Tiksi.Design calculations should be made for both the bear-ing capacity and deformations. However, in practicethis certain requirement is not carried out due to absence of experimental work. This is one of the com-mon problems of design.

2 OCCURRENCE AND DISTRIBUTION OF FROZEN SALINE SOILS ON THE ARCTIC COAST

The formation of frozen saline soils occurs during theprocess of sedimentogenesis, through the redistributionof water and salts during the diagenesis of deposits andtheir freezing. In general, the origin of the salinizationis related to seashore processes. Sea incursions causethawing of frozen deposits under the sea and subse-quent saturation of pore solution by sea salts. These playa major role in the formation of saline soils.

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Frozen saline soils of the Arctic coast: their distribution and engineering properties

A. BrouchkovResearch Center for North Eurasia and North Pacific Regions, Hokkaido University, Sapporo, Japan

ABSTRACT: Frozen saline soils are widely distributed along the Arctic coast and have special engineeringproperties. They freeze at lower temperatures and contain more unfrozen water than other frozen soils. Frozensaline soils differ in their origins and chemical compositions. The origin of the salinity is related to marine sedi-mentation. However, continental processes are also involved. Changes in salinization alter creep capabilities ofsoil, and data on long-term creep is presented. Frozen marine deposits containing chloride ion have the lowestbearing capacity. Ice appears to be a bearing factor. Bearing capacity of fine-grained soils in a range of tempera-ture and salinity was studied. Statistical data on construction along the Arctic coast of Russia were analyzed.

Permafrost, Phillips, Springman & Arenson (eds)© 2003 Swets & Zeitlinger, Lisse, ISBN 90 5809 582 7

0

50

100

150

200

0 0.1 0.2 0.3 0.4 0.5

Salinization, %

Stre

ngth

, kPa

Figure 1. Long-term strength of adfreezing for concreteand marine sand at �3°C.

The marine, glacial-marine, shallow-water, andlagoon deposits prevail among the soils. The saltswithin pore solutions are partially taken out uponfreezing, and partially redistributed. Salt movestogether with water toward the freezing front in claydeposits, and, by contrast, away from the freezingfront in sand (Brouchkov 2002).

Basically, frozen saline deposits of up to 10–20 m indepth along the Arctic coast contain salts within thelimits of 0.05–2% and belong mainly to the “marine”type of salinization with prevalence of chloride ionabove all (Table 1). The active layer, except for someslope and coastal sites, is not saline (Brouchkov 1998).

Formation of frozen saline fine-grained soils is apart of sedimentary process in cryolithozone. The dis-tribution of salts is related to the structure of depositsand is determined by conditions at formation as wellas by the subsequent processes in the frozen state.

As field materials show, the marine type of salin-ization is characteristic of coast areas with absolutealtitudes of 150–200 m above sea level, and north ofthe border of thawed frozen soils during the climaticoptimum of the Holocene (Fig. 2). The continental typeof salinization is common in dry areas of modernriver, lake and slope sedimentation. The mixed type ofsalinization is typical for the “land–sea” zone of inter-action and is distributed throughout the area, where saltsof both sea and continental origin contribute to thesalinization of deposits (Brouchkov 2002).

The uniform distribution of salinization or its increase with depth is observed in most cases (Fig. 3).

The non-uniform distribution of salinization withdepth can be caused by conditions of formation. Salinechilled soils and cryopegs are common almost any-where on the Arctic coast.

An increase in salinization with depth (Fig. 3) is mostlikely caused by the process of salts being lost fromthe upper layer of permafrost due to the migration ofsalts and salts moving out in the active layer. There is

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Table 1. Average salinization of frozen soils along theRussian Arctic coast.

Area Sampling site Salinization, %

European part Haipudir Bay 0–0.3of Russia Amderma 0.1–1.5

Kolguev island 0.2–0.8Pechora river 0.1–0.2

Western Siberia Northern Yamal 0.5–2.0Southern Yamal 0.2–0.5Dikson 0.5–1Gidan 0.4–1.2

Eastern Siberia Chukotka 0.2–3Pevek 0.1–0.5Lena river 0.1–1Alazeya river 0.2–1.0

Figure 2. Distribution of frozen saline soils in the Arctic:-marine type -continental type.

0

3

6

9

0 0.2 0.4 0.6 0.8Salinization, Dsal, %

Dep

th, m

n.1 n.2 n.3 n.4

Figure 3. Distribution of salts in frozen deposits of thethird marine terrace in the Amderma area, Kara coast; num-bers represent boreholes.

seasonal movement of unfrozen water carrying saltsin frozen soils, which is directed according to a gradi-ent of seasonal temperature: upwards in the winter,downwards in the summer (Brouchkov 2000).Gradual removal of salts from upper permafrost occursin natural conditions, and sections of older deposits ofhigh marine terraces in Amderma area (Kara sea) arecharacterized by this salt distribution with depth.Therefore, the salt content of frozen soils is not stable.Salt transfer should be taken into account in design.

The temperature mode and the heat balance ofsaline soils is special because of their thermal proper-ties: high unfrozen water content and lower thermalconductivity.

3 MAJOR FEATURES OF COMPOSITIONOF FROZEN SALINE SOILS

The chemical and mineral composition of the frozensaline soils and grain size are similar to the composi-tion of other frozen soils of the Arctic coast. The valuesof salinization vary in the Russian Arctic (Table 1).Organic substances are characteristic of saline soils inrelation to low temperatures of sedimentation and fastfreezing of the deposits.

Chemical composition of pore waters (Velli 1980,Aksenov & Brouchkov 1993) is characterized by theconstancy and the dominance of sodium chloride, incase of marine type of salinization. The prevalence ofsulphur, carbon acid, and calcium ions is typical for thefrozen saline alluvial and other deposits of the CentralSiberia (“continental” type).

Salinization is normally increased with the increasein ice content, which is related to the replacement ofpore solution by ice during freezing.

The frozen saline soils of the Arctic coast are usuallycoastal deposits, and fine-grained composition is a typi-cal feature. Insufficient sorting of material, low densityand sand dust are observed in the saline deposits.

An essential characteristic of the structure of salinesoils is their heterogeneity: a mixture of frozen (iceinclusions) and unfrozen (saline mineral parts withunfrozen water) constituents is present in the structure.Unfrozen water content determinates the bearing capa-city (Tsytovich 1975, Williams & Smith 1989); there-fore, frozen saline soils are characterized by the relativeweakness.

4 MECHANICAL PROPERTIES OF FROZENSALINE SOILS

Mechanical properties of frozen soils depend on saltcontent (Fig. 1). The long-term creep properties ofsaline frozen soils have not been studied in depth(Velli 1980, Brouchkov 1998).

Strains of frozen saline soils of the marine typeunder constant uniaxial stress and at other conditions,as well as strains undergoing long-time deformation(more than 12 years) were examined. Three stages ofdeformation were observed: the stage of a dampingcreep, followed by the stage of a secondary creep, andthe final stage of a progressing creep, which was typ-ical for sand only at salinization of 0.03–0.2%.

Passage to the secondary creep happened at thestrain of 4–7%, and to the stage of increasing creeprate – at strain of 8–11%. However, the stages were notobserved for temperatures from �2 to �4°C for frozensaline silt (Dsal 0.09%; 0.2; and W 0.36–0.40).Damping creep was observed up to strain of 20%. Adecrease in creep rate with time is a characteristic fea-ture of the frozen saline soils. A value of strain, forexample 20% could be considered as the criterion offailure in such a case.

By this feature of creep the frozen saline soils differfrom non-saline frozen soils, where all three stages ofcreep are observed. There is also a difference betweenice-saturated soils, where creep with the constant ratepredominates.

An increase of water content decreases the strains(Fig. 4). Therefore, ice plays a bearing role, and thevalue of strength of ice-saturated frozen saline soils islarger.

Stresses of frozen saline soils are smaller with areduction of grain size of soil (Fig. 5).

Deformations are increased with salinization andtemeratures according to the increase in the unfro-zen water content. The type of salinization plays animportant role: silt containing Na2SO4 is about 1.5times stronger than silt with NaCl on average (Fig. 6).

One of the major problems of design calculations is the prognosis of long-time deformations of frozensaline soils. The engineering theories of the creep,based on a non-linear dependence between the rate of acreep and strain are simple and common (Vyalov 1986).

We carried out long-term (duration of more than 12years) experiments at the constant temperature andloads in the underground laboratory of Amderma per-mafrost station, which is located at the depth of 14 m

97

0

5

10

15

0 50 100 150Time, hours

Stra

in, %

W=0.3 W=0.5 W=0.7

Figure 4. Strains of marine sand at �2°C, salinizationDsal 0.5% under uniaxial stress of 0.01 MPa and water con-tent (W) of 0.3, 0.5 and 0.7.

underground. The temperature oscillations did notexceed 0.3° during the period of observation.

The long-term creep of saline silt is characterized bya decreasing rate (Fig. 7). Redistribution of ice andsome thickening of ice lenses took place in frozen saline

samples during the experiments. We have found that thebest correlation of calculated and experimental data hasbeen achieved by using the Vyalov’s formula (1986).

5 THE USE OF FROZEN SALINE SOILS ASBASES AND STATISTICS OF DAMAGES

In the majority of cases frozen bases in the Arctic coastare susceptible to slow deformations. The problem withdesign is the overestimation of bearing capacity offrozen saline soils, particularly of the marine type ofsalinization. Phase transfers of frozen saline soils are inthe range of negative temperatures, the period and depthof thawing increase, and this is often not taken intoaccount. Consequently, deformations of the bases occur.

Other reasons for deformations should be also con-sidered. An increase in soil temperature in many settle-ments of the Arctic coast has been occurred afterconstruction. For example, the mean annual soil tem-perature is about �7° inside, but �12°C outside of thesettlement in Tiksi; it is �3° inside, but �4.5° outsideof the settlement in Amderma. Thus, the bearing capac-ity of soils is normally overestimated before construc-tion begins because the temperature changes were notconsidered. Snowdrift on the Arctic coast is a signifi-cant problem since snow cover acts as a warming agent.Some buildings in small settlements are placed in dan-gerous proximity to the sea. Numerous examples ofdestructions, caused by the thermoabrasion are knownin Varandei, Amderma, Harasavei, and other places.

As the result of inspection of about 200 buildings ithas been established that the main reason for defor-mations is underestimation of bearing capacity offrozen soils and change of temperature mode after theconstruction, mostly because of thermal influence ofbuildings or wastewaters in the base. A poor manage-ment and departmental differences in the constructionpolicy resulted in the significant problems.

The damage to buildings from deformations alongthe Arctic coast is very extensive and has costs of atleast few billions of rubles, valued in 1990. Repairand restoration of buildings cost about 25–100% ofthe initial price of construction in the Russian Arctic.The number of deformed objects reaches 25–50% oftheir total number. Some typical examples follow.

1. Apartment building in Amderma has a ventilatedbasement (Fig. 8). An increase in the mean soiltemperature occurred from �3°C up to �1.5°C sothe building began to deform.

2. A high school in Amderma is a 3-storeyed, brickbuilding on piles. Marine sandy silt is in the base;salt content increases with depth and reaches0.6–0.9% at depths of 4–9 m. The design engineersof this building have not taken into account thesalinization of soils. The building has many cracks.

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0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Sand Sandy silt Silt

Stre

ngth

, MPa

Figure 5. Long-term strength of frozen saline soils underconstant uniaxial stress at �2°C, salinization Dsal 0.2%.

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Sodiumchloride

Calciumchloride

Sodiumsulphate

Stre

ngth

, MPa

Figure 6. Long-term strength found in the ball test ofmarine silt at �2°C, salinization Dsal 0.5%; chemicalcomposition of salts is different.

0

2

4

6

8

10

12

14

16

0 2000 3000Days

Stra

in, %

S1 S2 S4

1000

Figure 7. Long-term strains of marine frozen saline siltunder constant uniaxial stress of 0.1 MPa, at �3°C; salin-ization Dsal 0.5%; specimens are numbered.

3. Deformations are observed in one building locatedon 32 Polar Street in Amderma. This heavy brick 4-storey building has some cracks in outside walls.The base is frozen saline (up to 1%) sandy silt.

4. The boiler building on Lenin Street in Amderma(Fig. 9) has deformations exceeding 1.5 m due tolong-term creep and an increase of soil temperatures.

Catastrophic deformations were also observed inother buildings of the Arctic settlements, power linesand heat pipelines in Dikson, and the sewer networks ofAmderma. Due to flooding by the subpermafrost salinewaters the construction of 48-room apartment buildingand kindergarten in Amderma and a 125-room condo-minium in Pyramid (Spitsbergen) were terminated.

Twelve percent of all buildings in Amderma are aban-doned or in the state of emergency, while 32 of a total of66 stone buildings are deformed. Only 2 of 19 thermaland power plants have insignificant deformations, and10 are in an emergency state. The majority of buildingswere constructed in the last 10–12 years; a significantnumber of the deformed old buildings are disassembled.

The total number of deformed buildings (Table 2) isabout 40% and above (Brouchkov, 1997; Velli, 1980).Inspections of buildings in Amderma have shown that108 of 268 buildings were deformed and cracked.

The incorrect estimation of the bearing capacity ofthe bases is among the major reasons for the occurrenceof deformations. Research has revealed a significantdivergence between experimental data on strength ofthe frozen saline soils (R) and their resistance to shear-ing load (Raf) and data recommended by ConstructionsNorms and Regulations (CNR) 2.02. 04-88. The CNRwere applied in the design of all settlements on theRussian Arctic coast. The CNR include mean values ofstrength for all types of salinization. Confirmation ofthe data obtained in the laboratory has been obtained bypile testing in Amderma (Table 3).

It has been established by laboratory tests that thefrozen saline soils in the Arctic coast of Russia haveextremely low strengths. The recommended bearingcapacity values are given in Table 4.

The study of the frozen saline soils has resulted in anumber of recommendations:

1. The common method consisting of tests on uniax-ial compression by step loadings does not allow forthe determination the bearing capacity of salinesoils because of the creep characteristics; testingby constant loads is necessary;

2. The duration of tests should be at least 3 days forthe estimation of the stress characteristics;

3. An increase in ice content of frozen saline soilsleads to an increase in their bearing capacity; in somecases icy bases are preferable;

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Figure 9. Damaged boiler building, Amderma town.

Table 2. Statistic of damages in areas of frozen salinesoils distribution.

Town Total deformation rate, %

Amderma, Kara sea coast 40Dikson, Kara sea coast 33Tiksi, Laptev’s sea coast 22Pevek, 50Yakutsk, Lena river valley 27

Figure 8. Damaged apartment building, Amderma town,Kara Sea coast.

Table 3. Results of tests of concrete piles in frozen salinedeposits by static loading in Amderma.

BearingBearing capacitycapacity accordingaccording tests of

Test Soils CNR, kN piles, kN

1 Sand up to 4 m, then sandy 410 310silt; T �2°C,salinization 0.1%

2 Sandy silt with T �2°C, 810 680salinization 0.1–0.2%,water content 30–50%

3 Sandy silt, T �3.5°C, 640 290salinization 0.6–0.9%, water content 30–50%

4. For design calculations, it is necessary to take intoaccount the long-term migration of salts in thesaline frozen soils under temperature and salt con-tent gradients.

6 CONCLUSIONS

1. Frozen saline soils are widely distributed along the Arctic coast and are characterized by low bear-ing capacity. Chemical composition of salts isimportant: frozen deposits of the marine type havethe lowest strength. Ice normally plays a bear-ing role.

2. Salts change creep capabilities of soil: creep ratedecreases with time, as confirmed by long-termexperiments lasting 12 years.

3. Almost half of all buildings along the Russian Arcticcost have been damaged, and the major reasons forthe damages were the following: underestimatingof the influence of salinization of soils; uncon-trolled heat emission due to water leaking andsnow redistribution. Existing construction regula-tions concerning bearing capacity calculations offrozen saline soils need to be reviewed.

ACKNOWLEDGEMENTS

I am grateful to the former staff members of Amdermapermafrost station, Dr. V. Aksenov and Dr. Y. Velli forthe assistance in the research.

REFERENCES

Aksenov, V.I. & Brouchkov, A.V. 1993. Plastic Frozen (Saline)Soil as Base. Proceedings of the Sixth InternationalConference on Permafrost, Beijing, China: 1–5.

Brouchkov, A.V. 1998. Frozen saline soils of the Arcticcoast, their origin and properties, Moscow: MoscowUniversity Press. 330 p. (in Russian).

Brouchkov, A.V. 2000. Salt and water transfer in frozensoils induced by gradients of temperature and saltcontent. Permafrost and Periglacial Processes 11(2):153–160.

Brouchkov, A.V. 2002. Nature and distribution of frozensaline sediments on the Russian Arctic coast.Permafrost and Periglacial Processes 13(2): 83–90.

Hivon, E.G. & Sego, D.C. 1993. Distribution of SalinePermafrost in the Northwest Territories, Canada.Canadian Geotechnical Journal, 30: 506–514.

Tsytovich, N.A. 1975. The mechanics of frozen ground.New York: Scripta, McGraw-Hill, 426 p.

Velli, Y.Y. 1980. Foundations on complex permafrost soils,In: “U.S. Army Cold Regions Research and EngineeringLaboratory, SR 80-40 and Building under cold climatesand on permafrost; collection of papers from a U.S.-Soviet joint seminar”, Leningrad, USSR, Dec. 1980:204–217.

Vyalov, S.S. 1986. Rheological foundations of soil mechan-ics. Amsterdam: Elsevier, 564 p.

Williams, P.J. & Smith, M.W. 1989. The Frozen Earth,Cambridge: Cambridge University Press, 306 p.

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Table 4. Bearing capacity of frozen saline soils of marine type.

Salinization Bearing capacity R, kPa (kg/cm2), at temperature °C(Depth of foundation 4 m)

Dsal, % �1 �2 �3 �4

Sands0.05 700 (7.0) 900 (9.0) 1100 (11.0) 1200 (12.0)0.1 400 (4.0) 500 (5.0) 600 (6.0) 750 (7.5)0.15 200 (2.0) 350 (3.5) 450 (4.5) 550 (5.5)0.2 250 (2.5) 300 (3.0) 400 (4.0)0.3 200 (2.0) 300 (3.0)0.5 200 (2.0)

Silty sands0.1 900 (9.0) 1000 (10.0) 1200 (12.0) 1350 (13.5)0.2 400 (4.0) 550 (5.5) 900 (9.0) 1100 (11.0)0.3 250 (2.5) 500 (5.0) 700 (7.0) 800 (8.0)0.5 250 (2.5) 300 (3.0) 400 (4.0)0.8 200 (2.0)

Sandy silts and silts0.2 450 (4.5) 700 (7.0) 950 (9.5) 1150 (11.5)0.5 150 (1.5) 300 (3.0) 400 (4.0) 750 (7.5)1.0 150 (1.5) 250 (2.5) 400 (4.0)