NRC Publications Archive Archives des publications du CNRC Soil sampling in permafrost areas Johnston, G. H. For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous. Publisher’s version / Version de l'éditeur: https://doi.org/10.4224/20375580 Technical Paper (National Research Council of Canada. Division of Building Research), 1963-07 NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=f93d9669-41db-43e7-b87e-72319ff4da7c https://publications-cnrc.canada.ca/fra/voir/objet/?id=f93d9669-41db-43e7-b87e-72319ff4da7c Access and use of this website and the material on it are subject to the Terms and Conditions set forth at https://nrc-publications.canada.ca/eng/copyright READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site https://publications-cnrc.canada.ca/fra/droits LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB. Questions? Contact the NRC Publications Archive team at [email protected]. If you wish to email the authors directly, please see the first page of the publication for their contact information. Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à [email protected]. NnrroNeL ResEARcH CouNclt- CANADA . DIVISION OF BUILDING RESEARCH SOILSAMPLINC IN t, PERMAFROSTAREAS + i BUILDIi,,JGRESEARCH I F,- { -\, - | i-':- il AUG13 1963 NATIONAL RESEARCH COUNCIL ANATYZED G. H. Johnston Northern ResearchCroup, Soil Mechnnics Section, Diuision of Buildine Research, National Research Courwil, Ottausa, Canada TECHNICAL PAPER NO. 155 OF THE DIVISION OF BUILDING RESEARCH Permission to publish this article must be obtained from the Engineering Institute of Canada, 2050 Mansfield Street, Montreal, Canada. : o:'^1ffi OTTAWA PRICE 10 CENTS JULY 1963 NRC 7417 _z 61.3 cc5 r-l-'tHE OCCURRENCE of perenni- perennially frozen ground, the depth -l ally {r'ozen ground, more common- of the active layer and the depth of ly known as permafrost, throughout seasonal frost penetration should be much of northern Canada creates determined durine the course of sub- special problems for engineering ron- surface investigati,ons. This is of par- struction. With the great increase in ticular importance in the region at construction activity in Arctic and the southern boundaly of permafrost Subarctic regions, the diificulties rn'here perennially frozen ground may encountered in both the construction occur at several feet below the and maintenance of buildings, roads, ground surface. airstrips and other structures have The relative inaccessibility of many emphasized the need for thorough Fig. 3, Test pit excavation by natural northern areas and climatic limita- thawing. Removing thawed material site investigations prior to the design tions may dictate to a large extent from test pit excavated in gravel. of such structures in areas underlain what fornl a subsurface investigation, by permafrost. may take.uThe purpose of this papei- natural exposures such as those occur- Permafrost is not a new material is to outline the various nlocedures ring along stream and lake banks, in but is simply the frozen equivalent of and techniques that *"y b" used in gullies and, as a result of local slump- materials found in more southerly engineering soil surveys to obtain ing, (Figs. I and 2) on steep, gener- regions. It is a thermal condition of representative samples of perennially ally south-facing slopes. By late sum- the ground, and the engineering prob- frozen ground in northern areas, so mer, thawing has usually penetrated lems associated with it arise mainll, that subsurface conditions may be well into the face of the exposure because of the variable nature of soil adequately determined. so that representative samples can be properties from the frozen to thb easily obtained. thawed state. Perennially frozen If a complete profile of the ex- ground which may contain a great posule is required, colluvial material deal of moisture in the form of ice must be removed by digging a narrow may, upon thawing, Iose much of its trench down the slope. Deeper supporting stlength, resulting in large ex- cavation into the slope is carried out settlements and even failures of vari- at intelvals when the soil type ous structures erected upon it. changes, and samples for classification A knowledge o{ the ice phase in and identificatior-r testine are taken. {rozen soils is most important to the Colluvial material is uiually easilv engineer for it is this factor that has recognized because it is a heterogene- the greatest effect on the perforrn- ous mixture of most of the soils ance of any structure. Ice segregation Fig. 2. Natural exposure following a Iocal slide in side of hill showing large found in the exposure. It is. most may occur in many ways ranging masses or lenses of ice. Note large easily t'ecognized by its disturbed from coatings on individual soil par- boulders in the predominantly fine- structure rvhile the parent material is ticles and minute hairline lenses, grained soil. more orderly. scarcely visible to the naked eye, to On large (deep) exposures, exca- large inclusions of ice up to several vating to obtain a continuous profile feet thick. These different forms of METHODS OF'OBTAINING is a tedious and time-consuming task. icc segregation can and do occur in SOIL SAMPLES Frequently, colluvial material is only all types of soil, even in gravel and Engineering soils and permafrost removed at the top, middle and bot- coarse sand. The most serious diffi- investigations may be carried out to tom of the slope with small test pits culties. however. arise from fine- depths of only 10 ft. or as much as at each of these locations. Where grained soils in which the moisture 100 ft. depending on the purpose of irregularities or distinct changes oc- content may be very large but where the survey. Such investigations may cur: on the slope, additional excava- the ice segregation may be difficult use one or more of the following tion should be carried out at these to discern. All soils must be ex- methods to obtain representative points. amined and sampled, therefore, to samples for the determination of soil determine the form and distribution In all soil exposure excavations, :rnd permafrost characteristics: of ice in them, in addition to the soil the slope orientation and depth to (a) type. sampling natural exposlrres, frozen ground (at right angles to (b) hand borings, the slope) should be noted. In many Although it is not always easy to (c) cases, frozen soil may be encountered distinguish between seasonally and test pits, (d) core drilling. relatively close to the face of the slope and a careful examination Fig, 1. Natural exposure on bank of The first two methods are generally should be made to determine the stream-thawing occurring accompanied applicable for shallower depths and ertent and types of ice segregation for general information, while the occurring in the material. Caution last trvo will give detailed information should be exercised, however, in de- to greater depths. Each method will scribing the ice phase for it has been be discussed separatelv. A list of found that the ice structure in these equipment requiled to carry out each locations is often disturbed and modi- of the above methods of erplolation fied by its proximity to and the effect is given in Appendir A. o{ the slope. If frozen soil is not en- countered in the excavation, then its Sampling Natural Exposures location u'ith reference to the face of N{uch irrfolmation irborrt soil cal l;c the slope should be established by gainell with little effort by examining means of probing. The expenditure of much energy to obtain frozen Drioing Pipe samples from an exposure is not usu- Core samples of frozen fine-grained ally iustified. materials can sometimes be obtained Accepting the limitations of this by driving a heavy walled steel pipe method in providing reliable informa- into the ground with a sledge ham- tion on ice segregation, the investiga- mer. The pipe used should be about tion of natural soil exposures is still I to 2 in. in diameter and about 5 ft. one of the most effective means of in length. The upper or striking end obtaining much exploratory soil in- of the p,pe shoutrd be fitted with an formation in northern areas with a extra heavy coupling or pipe cap to minimum of effort. The method plevent splaying of the pipe when should be used wherever possible for struck. The cutting edge of the pipe a preliminary assessment of soil and can be specially hard tipped but permafrost conditions in any area generally this is not warranted. The under consideration as a consuuc- cutting edge can be kept relatively tion site. sharp using a file. As the pipe is struck, it is rotated by pipe wrenches. Hand Borings It should not be driven more than Obtaining soil samples of perenni- 6 to 9 in. into the ground at one time, ally frozen ground using conventionarl since the removal of the pipe can be hand-boring equipment is difficult difficult. The soil core is removed and at times impossible because of from inside the pipe by gently tap- its rock-like nature. Hand borings ping the outer wall with the hammer'. are not practicable in frozen granular Holes have been produced by this Fig.