Analysis of ice from medium-scale indentation tests

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Analysis of ice from medium-scale indentation tests

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National Research

Council Canada Conseil national de recherches Canada

Institute for lnstitut de

'lectian·cal Engineering genie mecanique

Cold Regions lngenierie des regions

Engirleering fro ides

taC·CtaC

Analysis of Ice From Medium-Scale

Indentation Tests

N.K. Sinna and B. Cai

!..aborato,y Memorandum ~992102 CONTROLLED UNCLASSIFIED

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Memoire de laboratoire IME-CRE-LM-002 CONTRCLEE NON CLASSIFIEE

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CONTROLLED UNCLASSJF1ED CONTROLEE NON CLASS1FlEE

ANALYSIS OF ICE FROM J\1EDIUM-SCALE INDENTATION TESTS

ANALYSE DE LA GLACE AU MOYEN D'ESSAIS D'INDENTATION

A

MOYENNE ECHELLE

N.K. Sinha and B. Cai

This memorandum is issued to furnish information in advance of a report. Il is preliminary in character,

has not received the careful editing of a report and is subject to review. Le present memoire est

a

caractere preliminaire.

renseignements et i1 sera sujet

a

revisions.

Institute for Mechanical Engineering Laboratory Memorandum

1992/02

R. Frederking, Head/Chef

Cold Regions E ngineering Program/ Programme J ngeni~rie des regions fro ides

Il est mis en circulation a.fin de fournir des

Institut de genie mecanique Memoire de laboratoire IME-CRE-LM-002 J. Ploeg Director General/ Directeur general Copy/Copie _

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IME-CRE-LM-002 ABSTRACT

Five blocks of ice, representing four medium scaJe indentation tests were examined. These blocks represent the following April, 1989 tests: (1) Test 4, Block 1; (2) Test 4, Block 2; (3) Test 6 and 7; (4) Test 8; and (5) Test 10. The analyses were made using double-microtomed thin-sections and observing them under polarised light and combined polarisecVscattered light technique. It is shown that the latter method is a powerful tool for the examinations of deformed and undefonned ice. Macro-crack damages, micro-crack damages and inclusions are revealed in a dramatic manner by the combined polarised/scattered light technique. Apparently undamaged ice, that was visible as 'blue zones' immediately after the indentation tests, are shown to have undergone severe microstructural modifications.

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ii Uvffi-CRE-CTR-002

RESU1VIE

On a examine cinq blocs de glace representant quatre essais d'i ndentation de moycnnc cchelle. Ccs blocs correspondent aux essais suivants conduits en avril 1989: (1) Essai 4, bloc l; (2) essai

4, bloc 2; (3) essais 6 et 7; (4) essai 8; et (5), essai 10. On a realise Jes analyses en employanl des coupes minces preparees avec un microtome double, et en les ohservant en lumiere diffusce. On dcmontre que la sec..xmde methode est un outil rr~s efficace pour examiner la glace deformce. Les dommages causes par des macrofissures, ceux causes par des microfissures, et les inclusions, sont mis en evidence de f~on excellente par la technique combinant la lumicrc diffusee. On montre que de la glace apparemment non endommagcc, visible sous forme de "zones bleues"

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L\fE-CRE-LM -002 lJ1 CONTENTS Page ABSTRACT . . . . . . . . . . . i RESUlvIE . . . . . . . ii LlST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii 1.0 INTRODUCTION . . . .. . . . 1 2.0 l\1ETHOD . . . . . . . 1

3.0 RESULTS AND ANALYSIS . ... . . ... . . .. . . .

3.1 Ice Characteristics . . . . 3.2 Microstructural Analysis . . . . 4.0 CONCLUSIONS . .' . . . ... . . .... ... . . ... . . . 5.0 REFERENCES APPENDIX 1 DOCUMENTATION FORM LIST OF FIGURES 2 2 3 6 7 56 Figure Page 1 2 3 4 5 6 7

The trench wall exhibiting ridged ice with 0.5m thick blocks of ice

Vertical density and salinity profile of Ice Island multi-year sea ice

sampled in 1989

Vertical salinity, density and grain structure profile of Ice Island multi-year sea ice sampled in 1990

Load time record of Test 4.1. Average indentation rate= 4rnm/s

Calculated pressure area curve for test 4.1. Average indentation rate= 4mm/s

Load time record of Test 4.2. Average indentation rate =15mm/s

Calculated pressure area curve for Test 4.2. Average indentation rate

=15mm/s 8 9 10 12 13 15 16

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27 28

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Schematic of truncated wedge ice face for Tests 6 and 7

Load time record of Test 6. Average indentation rate 19 mm/s

Calculated average pressure area curve for Test

6

Load time record of Test 7. Average indentation rate 68 mm/s

Calculated average pressure area curve for Test 7

View of contact face after Tests 6 and 7 (left) and the location of the sampled ice block (right)

Sketch of Block 1 of Test 6 and 7 showing locations of thick sections, with respect to the original ice cover, taken for thin sectioning: Horizontal Section (1), Mid-Vertical Section (2) and Longitudinal Vertical Section (3)

Top View of Block 1 (Test 6 and 7) before Cutting

Photograph of horizontal thin section (1) of Block 1 (Test 6 and 7) under cross-polarized light. The bottom end of the micrograph shows the contact surface and recrystallized crushed zone

Photograph of horizontal thin section (l) Block 1 (Test 6 and 7) under combination cross-polarized and scattered light. Note the microcracks and macrocracks on the right

Photograph of longitudinal vertical thin section (3) of Block I (Test 6 and 7) under cross-polarized light shows that the ice was columnar-grained and vertically oriented at that location

Photograph of mid-vertical thin section (2) of Block 1 (Test 6 and 7) through cross-polarized light

Photograph of mid-vertical thin section (2) of Block l (Test 6 and 7) under combination cross-polarized light and scattered light

Details of horizontal thin section (1) of Block 1 (Test 6 and 7) under parallel-polarized light. Note the concentration of minute air bubbles (or inclusions) trapped in the crushed zone at the bottom and along the macro-cracks

De.tails of mid-vertical thin section (2) of Block 1 (Test 6 and 7) through cross-polarized light

V 26

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31 32 32 33 33 34 34 34 35 35

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50 51 I:ME-CRE-CTR-002

Schematic of truncated wedge ice face for Test 8

Load time record of Test 8. Average indentation rate = 80 mm/s

Dis placement time record of Test 8. Average indentation rate = 80 mm/s

Ca1culated average pressure area curve for Test 8

View of contact face after Test 8 (top) and location of the sampled ice blocks (bottom)

Sketch of Bl ock 2 of Test 8 showing locations of thick sections, with respect to the original ice cover, taken for thin sectioning: Horizontal Se,tion (1), Mid-Vertical Section (2) and Longitudinal Vertical Section (3)

Top view of Block 2 (Test 8 on Face l 0) before cu tting

Photograph of horizontal thin section (1) of Block 2 (Test 8) under cross polarized light

Photograph of horizontal thin section (1) of Block 2 (Test 8) under combination cross-polarized and scattered light

Photograph of longitudinal vertical thin section (3) of B lock 2 (Test 8) under polarized light

Photograph of longitudinal vertical thin section (3) of Block 2 (test 8) under combination cross-polarized light and scattered light

Photograph of mid-vertical thin section (2) of Block 2 (Test 8) under cross polarized light

Photograph of mid-venical thin section (2) of Block 2 (Test 8) under combination cross-polarized light and scattered light

Schematic of truncated wedge ice face for Test 10

L oad time record of Test 10. Average indentation rate = 20 rnm/s

Displacement time record of Test 10. Average indentation rate= 20 mm/s

36

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40

4 1 42 42 43 43 44 44 45 45 47

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View of contact face after Test 10 (left) and location of the sampled ice block (right)

Sketch of Block 3 of Test 10, Face 12 showing locations of thick sections, with respect to the original ice cover, taken for thin sectioning: Horizontal Section (1), Mid-Vertical Section (2) and Longitudinal Vertical Section (3)

Top view of Block 3 (Test 10, Face 12) before cutting

Photograph of horizontal thin section (2) of Block 3 (Test 10) under cross polarized light

Photograph of horizontal thin section (2) of Block 3 (Test 10) under combination cross-polarized light and scattered light

Photograph of longitudinal vertical thin section (3) of Block 3 (Test 10) under cross-polarized light

Photograph of longitudinal vertical thin section (3) of Block 3 (Test 10) under combination cross-polarized light and scattered light

Photograph of mid-vertical thin section (2) of Block 3 (Test 10) under combination cross-polarized light and scattered light

Photograph of mid-vertical thin section (2) of Block 3 (Test 10) under cross-polarized light

vii 51 52 52 53 53 54 54

55

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ICE CHARACTERIZATION WORK ON SAMPLES OF ICE

1.0 INTRODUCTION

The "Ice Island Research Station" commonly called "Hobson's Choice", is a 5 km wide and 8 km long tabular iceberg. The ice island broke off the East Ward Hunt Tee Shelf in 1982-83. Like a sandwich, the island consists of a 40 to 45 m thick strip of shelf ic.:e with 5 to 10 m thick multi-year ridged sea ice on either side. It is the largest natural ice island presently known in the Arctic Ocean' (Jeffries, et. al. , 1988). Since 1984

a

research station h·as been maintained on it by the Polar Continental Shelf Project (PCSP), an agency of the Federal Government of Canada. At the time of testing in April 1989, the island was located at (79° 23.S'N; 102° 20.2'W ), near the northern tip of E11ef Ringnes Island. The island did not move significantly from this position during the period from ApriJ 1989 to May 1990 when the second series of tests were earned out.

A series of medium scale indentation testc. were carried out on the multi-year sea ice, adjacent to the shelf ice, in April, 1989 (Frederking et al., 1990) and again in May,

1990. Several blocks of ice were recovered from the island after tests and were shipped to Ottawa. The present studies were carried out in Ottawa.

2.0 METHOD

The large-scale examination of the multi-year. ice was carried out making observations of the two walls of the trench prepared for the indentation tests. Vertical cores of ice (100 mm in diameter) were also taken from areas adjacent to the trench during each of the 1989 and 1990 field test series. These cores were used to detennine the vertical distribution of salinity and density, as well as the microstructure of the ice.

The microstructural studies, to be presented here, were carried out in Ottawa during the month of September, 1991. These studies were made on thin sections of ice blocks sampled after the medium-scale tests in April, 1989. In all, five blocks of ice were recovered from the trench wall. These blocks represent ice from the following April, 1989 tests: (1) Test 4.1 and 4.2 - left side (to be called as Block 4-1) ; (2) Test 4.1 and 4.2 - right side (to be called as Block 4-2); (3) Test 6 and 7; (4) Test 8 and (5) Test 10. The ice blocks were initially shipped in insulated boxes to Resolute, where the boxes were stored in a cold chamber at about -20°C for a few days, before subequent transport by air to Ottawa.

In Ottawa, the ice blocks were stored in deepfreezers at temperatures of about -30°C until they were taken out, one by one, to the cold room for examination. The examinations were carried out at temperatures in the range - I5°C to -20°C. The cold room temperature varied because the present investigation was carried at the same time mechanical tests were being conducted inside the same room.

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2 Irvffi-CRE-CTR-002

Each block was photographed and a sketch of it was made before cutting into smaller sections. In general three thin sections were prepared from each block: I) a horizontal section representing a plane parallel to the top surlace of the ice cover and nom1al to the surlace subjected to the indentation, 2) a vertical section from the middle of the block and representing a plane normal to the top smface of the ice cover and also normal to the smface subjected to the indentation, and 3) a vertical section parallel and about 100 mm away from the indented surlace. These sections will be referred later as Horizontal Section, Mid-Vertical Section and Longitudinal Vertical Section respectively.

Thin sections were prepared from 5 mm thick sections cut from the ice blocks using a band saw. A double-microtomed thin sectioning technique, developed earlier (Sinha, 1977), was used to prepare thin sections with thicknesses around 0.5 mm. The double-microtoming technique avoids the use of any hot plate and warm glass plates; thereby not affecting the microstructure in any manner, particularly for sea ice with complex sub-structure. The thin sections were photographed using cross-polarized light as well as using a technique of combining the cross-polarized light with scattered light. The latter method brings out the inclusions and cracks.

The details on each block, including descriptions of the medium-scale test conditions and test histories, are given in sequential order along with the photographs of the thin sections. Both vertical and horizontal sections, made parallel or perpendicular, respectively to the original ice surface and the axis of indentation, are shown.

3.0 RESULTS AND ANALYSIS

3.1 Ice Characteristics

The 65 m long, 3 m deep and 3 m wide trench, prepared for the medium scale indentation tests, provided two 65 m x 3 m surfaces, or a total smface area of 390 m2_,

for visual examination. The ditch walls showed that the ice was part of an old ridge or rubble field. Not a single large scale void, greater than a few millimetre in diameter, was noticed. The trench walls were deep blue in colour with cloudy patches. The outlines of ice blocks that could be seen at many places in the walls indicated that the ridging occun-ed when the thickness of the sea ice cover was about 0.5 m thick (Figure 1). The ice showed characteristics typical for old, consolidated, dense ridged sea ice examined in Mould Bay (Sinha, 1987).

Although the density varied only slightly between 875 and 886 k m-3, the salinity varied significantly with depth and location (Figures 2 and 3). The ice core in Figure 2 was taken about 2 m from the wall in the central area of the trench prepared in 1989. Core I from 1990 in Figure 3 was situated approximately 20 m from the core used for the salinity and density determinatins. Both cores were taken about 2 m back from the 1990 trench wall. The ice conditions did not change during the one-year period between the two field project<;. In general, the ice salinity increased from zero at the surface level to

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lME-CRE-LM -002 3

about 3 parts per thousand

f

I ₀₀) at a depth of 4 m. The average salinity at the depths

for the medium scale indentation tests was about l to 2 °/ ₀₀• The rnicrostrucniral

analyses (Figure 3) of a 4 m long core showed that the ice consisted of fine grained granular ice, oriented and randomly oriented columnar-grained ke and oriented and randomly oriented frazil ice.

3.2 Microstructural Analysis

The details of microstructural studies carried out on indented ice

are

presented sequentially in the following subsections. The result5 for the Test No. 4 are presented in Figures 4 to 20. The ice characterization for Test No. 6/7 are presented in Figures 21 to 35. The results for Test 8 are presented in Figures 36 to 46. The work carried out on Test No. 10 are presented in Figures 49 to 61.

Tests 4.1 and 4.2

The time dependence of the actuator force generated during Test No. 4.1 is shown in Figure 4. For this test a spherical indentor impinged on a flat ice face. The dependence of the average plate pressure (calculated from the actuator force and the estimated contact area) on contact area is given in Figure 5. Neglecting the uncertainty of measurements during the initial period, the pressure increa,;ed rapidly to a maximum value and then dropped momentarily before rising again. In this case the system responded in such a manner that three pressure peaks, up to 18 MPa, were noted before the end of the test. Test No. 4.2 was a repeat of loading of the indentation created by Test No. 4.2. A monotonically increasing actuator force with time and a corresponding monotonically increasing average pressure with contact area were observed during the repeat test (Figs. 6 and 7). A maximum pressure of about 14 MPa wa~ reached during this test.

Figure 8 (top) shows the view of the contact face after the Test 4.2. The reddish part in the central area shows the paint that came off the indentor surface during the indentation process. Both radial and circumferential cracks are visible in the photograph. Note that the extensive cracking and crushing activities were limited to the ice around the central zone. The central zone seems to have retained some of the blue colour, the main characteristics of the untested trench wa11, and appears to be undamaged to the naked eye.

It

was, therefore, decided to take the sample blocks from the central area as shown in Figure

8

(bottom). For identification purposes, the block representing the left side will be referred to as Block 4-1. The block from the right hand side will be called Block 4-2. Each block was sectioned following the method described earlier. Figure 9 shows a sketch of Block 4-1 and Figure 15 describes sections taken from Block 4-2.

The top views of both B1ock 4-1 (Figure 10) and Block 4-2 (Figure 16) show the ice was oriented at about an angle of 30 degree to the surface that was indented. The rows of dark spots and streaks provide sufficient indications that the ice was oriented. This orientation in the ice can be seen very clearly in the horizontal thin section (section 1 in Figure 9) viewed through cross-polarized light, see Figure 11 . It is speculated that the

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4 IME-CRE-CTR-002

ice was originally columnar-grained. However, the vertical section in Figs. 19/20 give indications that the long axis of the columnar grains were oriented about 10° - 20° from the vertical plane. Figures 13 and 14, because of severe recrystallization in the ice by the loading down to a depth of about 200 mm, do not provide any clear indications of the type of original ice.

Figures 11/12 and 17/18, when viewed together side by side, represent a cross section of the entire central area subjected to indentation (about 550 mm in width). The edges at the bottom of these photographs represent the contact surfaces during the indentation. The area near the left-hand side of Figures 11/12 and the right-hand side of Figures 17/18 represent the areas near the outer edge of the coloured area in Figure 8. Note the curvature in the sections and the crushed wedge-shaped layer of very fine grains in the contact zone.

It

should be mentioned that the outer zones were noted, immediately after the tests, to b~ the heavily crushed and contains exu-uded materials. Tt may be seen that the central area (right side of Figures 11/12 and the left side of Figures 17/18) is almost free from any crushed layer. This central area shows, however, extensive microstructural damage, primarily in the form of recrystallization, through the entire depth of about 200 mm represented by the thin sections (Figs. 13/14 and 19/20). Although Figure 13 shows the entire area as highly recrystallized, Figure 20, on the other hand, shows clearly the variation in the _degree of recrystallization with the distance away from the contact face. There were, therefore, large variations in the state of deformation. These observations indicate that the central zone (appears as blue in Figure 8 and apparently undamaged to the naked eye) are affected by subgrain-size microcracks an<l the associated recrystallization. Note that the grain size in the central zone are comparable to the width of the subgrains, often called platelet in sea ice. The platelet widths in sea ice are usually in the range of about I mm (see left side of Figures 11/12 or right side of Figures 17 /18). Almost intact ice can be seen at the left side of Figure 11 and at the right side of Figure 17.

Note the differences between the images taken under cross-polarized light and those taken using a combination of cross-polarized light and scattered light. Comparing the pairs of images; Figure I l with Figure 12; Figure 13 with Figure 14; Figure 17 with Figure 18, and Figure 20 with Figure 19; shows how scattered light brings out the voids and cracks in the material. Many of these details, however, are not revealed in the conventional images of thin sections observed with cross-polarized light. Figures 12 and 18 show the traces oflarge cracks as well as microcracks. The large crack in Figure 12 is transcrystalline. However, the microcracks that could not be seen in Figure 11 or Figure 17, for examples, are revealed in the form of white streaks in Figs. 12 and 18. These white streaks are of specific sizes and show some orientations. It can be seen that the spacings between the striations are in the range of 1-2 mm, equivalent to the platelet or subgrain spacings. The microcracks, therefore, are comparable to the size of the sub-grains. These tiny cracks tend to be at the subgrain boundaries and, consequently, they tend to follow the orientation of the sub-grains. The vertical sections in Figs. 13 and 19 give indications that the microcracks tend to be parallel to the long axis of the grains (slightly off the vertical axis). The presence of microcracks at the sub-grain boundaries

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indicate that the initiation of these cracks must be related to inter-sub-grain activities during loading and subsequent unloading.

Test 6 and 7

The geometry of the indenter and the indented ice for Test~ 6 and 7 (Figure 21) were different from Test No. 4. It may be seen that although Test No. 6 was carried out at an indentation rate of 19 mm/s, comparable to 15 mm/s of Test No. 4.2, Test No. 7 was made at a significantly higher speed of 68 mm/s. The loading and average ice pressure results for these tests are shown in figures 22, 23, 24 and 25. The ice block obtained after carrying out these two tests, perfonned on the same face or location, reflect primarily Test No. 7, which had an average pressure of about 12 MPa. This is again a case of testing previously loaded, and damaged ice.

The ice from Test Nos. 6 and 7 is of considerable interest because

of

the type

of

ice and the orientation of the ice with respect to the loading axis. Note that the ice was columnar grained (Figs.29 and 30) with the long axis of the grains oriented normal to the load axis or the direction of displacement. This is fortuitous for ridged ice, since the loading condition is similar to many laboratory tests. The loading condition is also similar to the in situ borehole indentation tests reported in Sinha (1987, 1991). The report on the borehole indentation of Ice-Island multi-year sea ice (Sinha, 1991) is reproduced as Appendix 1.

Both the horizontal sections (Figures 29/30) and the vertical sections (Figures 31, 32/33) show relatively little damage beyond the crushed layer. The crushed layer is indicated, as before , by the zone of granular ice with small grains. Note that the crushed layer is

not uniform and contains larger particles of ice. The demarkation boundary between the intact ice and the crushed layer is remarkably distinct. Similar observations were also reported in the Appendix. It should be pointed out that the boundary of the crushed layer follows some crystallographic surfaces. The micrographs in Figs. 34 and 35 illustrates this more clearly. Figure 34 also shows the trapped air/gas bubbles inside the crushed and sintered crushed zone.

Attention should be given to the secondary failure zone, bounded by a second front consisting of macrocracks, beyond the crushed layer, on the right hand side of Figure 30. Note that this zone is not

as

evident in Figure 30 taken through only cross-polarized light. The secondary zone indicates that crushing may occur in a sequential manner, macrocrack formation leading to a decrease in the degree of confinement and hence accelerated microcrack formation. A detailed description of the process is outside the scope of this report.

Test 8

Figures 36 to 48 represent the test conditions and microstructural analyses of indented ice from Test No . 8. This was a rapid test and the displacement rate of the actuator with

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6 II\1E-CRE-CTR-002

respect to the ice was not constant (Figure 38) and considerable fluctuations in the stress history can be seen in Figure 39. In this case macrocracks, making an angle of about 45 degrees with the indentation axis, can be seen in the photographs of the block shown in Figure 42. Note that these cracks are not readily visible, as in Figure 43 , when a horizontal thin section is observed through usual cross-polarized light. Scattered light brings out these cracks and the combined scattered-polarized light (Figures 44, 46 and 48) shows their locations with respect to the grain su·ucture and the grain orientations. Crushed layers often contain islands ·of ice or blocks representing the original ice. A number of such examples can be seen Figs. 43 and 47.

Test 10

The results of Test No. 10 are presented in Figs. 49 to 61. Comparison of the load-time record (Figure 50) with the con-esponding displacement-time record with respect to ice ( curve 'wrt ICE' in Figure 51) clearly shows that the fluctuations in the pressure history (Figure 52) were related to the variations in the indentation history. It is therefore necessary to consider the time dependent system response in any mechanical test. The processes of failure in ice is related to the history of loading and the end product, in this case the indented surface (Figure 53) represent the state of the ice body immediately after the instant of unloading. Such a postmortem is presented in Figures 55 to 61. The dark regions in Figure 55 corresponds to the highly cracked or crushed zone. The details of these regions can be seen in Figs. 56 and 57. As pointed out earlier, the scattered-polarized light method enhances delineation of the crushed zone. It also brings out the details inside the crushed zone and the area outside this zone.

4.0 CONCLUSIONS

The method of observing thin sections using cross-polarized light and the combined polarized-scattered light technique, in conjunction with double-microtoming method of making thin sections, allowed microstructural analyses of defonned ice from the ice island. Microstructural details, significantly beyond the resolution of the cross-polarized-light method can be seen when cross-polruized cross-polarized-light is combined with scattered cross-polarized-light. The traces of large cracks and other inclusions including microcracks, voids and brine pockets are made visible by the increased light intensity at these defects. Crushed and extruded or sheared layers near an indented surface consist primarily of small and equiaxed grains. These layers are visibly distinct from the neighbouring materials when observed using the combined scattered-polarized light technique. The boundary between crushed and intact ice tends to follow grain- or subgrain-boundaries.

Crushing process occurs in stages. Formation of macrocracks and their branching seems to be the first stage of crushing. The so-called 'blue' zone is not necessarily undamaged ice. Severe grain modification, primarily recrystallization, is the major feature of these zones and can reach depths of more than 100 mm.

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IME-CRE-LM-002 7

5.0 REFERENCES

Frederking, R. , Jordaan, I.J., and McCallum, J.S . (1990a). Field Tests of Tee Indentation at Medium Scale Hobson ' s Choice Ice Island, 1989. Proc. IAHR International Symposium on Ice, August 20-23, 1990, Espoo, Finland, Vol.2, pp. 931-944.

Frederking, R. , B lanchet, D., Jordaan, I.J., Kennedy, K., Sinha, N.K., and Stander, E.

(1990b). Field Tests of Ice Indentation at Medium Scale, Ice Island, April 1989. October

1990, Report No. CR-5866.1 , Prepared for Canadian Coast Guard and Transportation Development Centre.

Jeffries, M.O., Sackinger, W.M., and Shoemaker, H.D. (1988). Geometry and Physical Properties of lee Islands. Proc. POAC-88, Geophysical Institute of Alaska Fairbanks, U.S.A., Vol.I, pp. 69-83.

Sinha N.K. (1 977) . Technique for studying structure of sea ice. Journal of Glaciology, Vol. 18, No. 79, 1977, p. 315-323.

Sinha, N.K. (1987). The borehole jack - is it a useful Arctic tool? Journal of Offshore

Mechanics and Arctic Engineering, Transactions of the ASME, Vol.

109, No.4,

November 1987, pp. 391-397.

Sinha, N.K. (1991). In Situ Multi-Year Sea Ice Strength Using NRCC Borehole lndentor. Proc. 10th. Int. Conf. Offshore Mechanics and Arctic Eng. (O:MAE/ASME), Stavanger, Norway, June 23-29, 1991, Vol.4, pp. 229-236.

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8 TME-CRE-CTR-002

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100 ,_

u

' - . _ /

::r

I- _{1 50} Q_

w

0 200 250 JOO

o .oo o.5o 1 .uo 1 .~o 2.00

S/\Llr\J ITY

(p ot)

Fig.2 Vertical density and salinity profile of Ice Island multi-year sea ice in 1989.

I ~ I

,s

I t'"" ｾ＠I

g ·

1 N '-0

(19)

E

I

...

a. w 0 0.0 0.5 1.0 1.5 e CORE-1 T CORE-2 e CORE-1 oriented frazil columnar

liiirnffli~~

oriented frazil 2.0 2.5

J .O

3.5

4.0 0 1 2 3 4 SALINITY, 0 / oo

5

850

900

950

DENSITY, Kg·m-3

f-10omm

ｾ＠

CORE-1

Fig.3 Vertical salinity, density and grain stmcture profile of Ice Island multi-year sea ice in 1990. granular columnar ... 0

ｾ＠

n

ｾ＠

n

;3

8

_N

(20)

lME-CRE-LM-002

NRC Test No: 4.1

Date and time: 1989 April 23, 12:30

Ice Face No: 7

SSW Test No: NRC 03 Data file record length: 30 s

Digitizing rate per channel: 500 Hz Actuator stroke: . 48 mm

Actuator rate : 20 mm/s

11

Displacement transducers: 1 transducer was used to measure motion of the actuator rod with respect to the actuator body.

Accelerometers: · Two accelerometers were placed on the indenter diametrically opposite each other.

Servo control: The signal from the displacement transducer was used for control. Notes: The whole system performed satisfactorily.

(21)

12 IME-CRE-CTR-002 TEST #4.1

z

₃

ｾ＠ w

u

0:: 0 u..

₂

ｾ＠ 0 r-ｾ＠ : )

r-u

₁

ｾ＠

0 +----i---+---+---+---l

6

8 10 :

12

14 TIME,

s

(22)

lME-CRE-LM-002 ₁₃ TEST #4.1 0

₄₀

Cl. ｾ＠ w 0::: :::) (/)

30

(/) w 0::: Cl.

20

w C) <( 0::: w

ｾ＠

10 Q - + - - - + - - - + - - - 1

0.000

0.100

0.200

0.300 AREA,

m

2

(23)

14

NRC Test No: 4.2

Ice Face No: 7

SSW Test No: NRC 04

Data file record length: 30 s

Digitizing rate per channel: 500 Hz Actuator stroke:

51

mm

Actuator rate: 20 mm.ls

IME-CRE-CTR-002

Displacement transducers: 1 transducer was used to measure motion of the actuator

rod with respect to the actuator body.

Aooelerometers: Two accelerometers were placed on the Indenter diametrically opposite each other.

Servo control: The signal from the displacement transducer was used for control.

(24)

IME-CRE-LM-002

z

3

ｾ＠

-w

u

0:: 0 u..

2

Ci:: 0 ｾ＠ <( : ) ｾ＠

u

_<( 1 15 TEST 4 .2

o~---+---1

9.000

9.500

TIME, s

10.000

(25)

16 IME-CRE-CTR-002 TEST #4 .2

40

0

a..

2

₃₀

w

0::: : ) (./) (./)

₂₀

w Ct: CL

10 o~ - - - --+-- - -- - ---+--- -- -- --1

0.000 0 .100

0 .200

0.300 AREA, m 2

(26)

Fig.8. View of the contact face after Test 4 (top) and the location of the sampled ice blocks (bottom).

ｾ＠

r--ｾ＠

8

_Iv ... -..J

(27)

/' j

~-

\

r'

I

I I I 11 •

f

I

J

/ 1

2 / I

_.

// 1

! i ; . / . / I ' f I_J, I .

.. /3

BLOCK

1. I

I I

-1 -

_{I ,}

t

I I

.f

,1;---I),

; ·-····

. 1

t

I ·

: I I it I

.... j,

., BLOC/( /

4-2

! '

_l/1

_/

Fig.9. Sketch of Block 4-1 (Test 4) showing locations of thick sections, with respect to lhe original ice cover, taken for thin sectionong: Horizontal Section (1), Mid-Vertical Section (2)

and Longiludinal Vertical Section (3) .

Fig. IO. Top view of Block 4- 1 (Test 4) before cutting .

00

ｾ＠

n

ｾ＠

n

ｾ＠

I 0

s

(28)

ｾ＠ ._

--Fig. I 1. Photograph of horizontal thin section of sea ice (Block 4-1; Section 1; Test 4) under cross-po1arized light.

Fig.12. Photograph of horizontal thin section of sea ice (Block 4- 1; Section 2; Test 4)

under combination cross-po1arized light and scattered light.

ｾ＠

n

ｾ＠

r'

. .,,,, ｾ＠

8

_t-> ,__

'°

(29)

Fig.13. Photograph of mid-vertical thin section of sea ice (Block 4- 1; Section 2; Test 4) under combination cross-polarized light and scattered light.

Fig.14. Photograph of mid-vertical thin section of sea ice (Block 4-1; Section 2; Test 4) under cross-polarized light. t0 0

-ｾ＠

I n

ｾ＠

n

ｾ＠

8

h )

(30)

BL OC /(.

I

/

I

/

/ ! BLoCI(

4 - Z

;- -- -

··-.. .. 1, . .f j

2 "\,

.I 1 • - •- - - r I

I

1 1 / . / ii

3

Fig.15. Sketch of Block 4-2 (Test 4) showing thick sections, with respect to the original ice cover~ taken for thin sectionong: Horizontal Section (1), Mid-Vertical Section (2) and Longitudinal Vertical Section (3).

nm11mm111Dmmr1JtWMtm111n,JtB11r!ri11;:1~~r,:~r;¥.5~~:~;:f~:r.'.~~~:'; :'.'; '.!l!!!'···

'II t~1 \ f~~1l~hl 1" it, ,,,

1r·: .

) ~ ,.111: i" n:ir, ·, ~· ~'. . :1~\. • ' JI

it,~,.

11 11Jt~ J•, j d ｾ＠ 1,t I 1l!i'IM~ 'J ｾ＠I !j 1 \ I

Fig. I 6. Top view of Block 4-2 (Test 4) before cutting.

-

<'

ｾ＠

n

;

r

ｾ＠ 6 0 1-..> t...>

(31)

Fig.17 Photograph of horizontal thin section (1) of Block 4-2 (Test 4) of sea ke under

cross-polarized light. Curved surface at the bottom shows the contact surface. Note the recrystallized zone with relatively fine grains on the left and even finer grains near the cont1ct surface.

Fig.18. Photograph of horizontal thin section (1) of Block 4-2 (Test 4) of sea ice under combination cross-polarized light and scattered light. The cmshed zone near the contact surface is clearly

revealed. ｾ＠

....

!?

En

()

ｾ＠

0

;j

8

N

(32)

Fig.19. Photograph of mid-vertical thin section (2) of Block 4-2 (Test 4) under combination cross-polarized

light and scattered light. Bottom end of the micrograph shows the cantact face.

Fig.20. Photograph of mid-vertical thin section (2)

of Block 4-2 (Test 4) under cross-polarized tight.

...

ｾ＠

n

ｾ＠

ｾ＠ｾ＠_I Q

s

1:0 '.,.)

(33)

24

NRC Test No: 6

Date and time : 1989 April 24, 17:50

Ice Face No : 9

SSW Test No: NRC 06

Data file record length: 30

s

Digitizing rate per channel: 500 Hz

Actuator stroke: 50 mm

Actuator rate: 20 mm/s

[\1E-CRE-CTR-002

Displacement transducers: 1 transducer was used to measure motion of the actuator

rod with respect to the actuator body.

Acx:elerometers: Two accelerometers were placed on the indentor diametrically opposite each other.

Servo control: The signal from the displacement transducer A01 was used for control.

(34)

1~1E-CRE-LM-002

NRC Test No: 7

Ice Face No: 9

SSW Test No: NRC 07

Actuator stroke: 58

mm

25

Displacement transducers: , transducer was used to measure motion of the actuator rod with respect to the actuator body.

Accelerometers: Two accelerometers were placed on the indenter diametrically opposite each other.

Servo control: The signal from the displacement transducer A01 was used for control.

(35)

26 II\-IB-CRE-CTR-002

VERTICAL ELEVATION

ｾ＠

~2Dmm 720mm INDENTOR

~ /

g

....,20 3 / TRENCH WALL

l/llli:;,;:7'1~~)/1111

.SECTION A-A TEST NRC 6

AREA CRUSHED 270 .,.RENCH WALL

IN TESTNRC 6 ~ / '

/ I / I I / ·I I

/l'J7

I I / / I

/II

ICE

SECTION A-A TEST NRC 7

(36)

w

u

0::: 0 L

c:::

0

ｾ＠

::>

t-u

<l: lME-CRE-LM-002 27 TEST #6

2-r--- - - -- - - -- ----,

1

O+---t---+---+--- ----1

3.0 4 .0

5.0

6.0

TIME, s

(37)

28 rtvfE-CR E-CTR -002

TEST #6

0 CL ｾ＠

₆

w

0:: : ) (.I) (.I)

4 w

0:: 0....

w

(_!) <( ｾ＠

₂

w

>

<(

·o4----~----~---+---l

0.000 0 . 100

0.200

0.300

0.400

0.500 AREA, m 2

(38)

-w

u

0:: 0 I.J....

a::

0

ｾ＠

::>

t-u

<( HvfE -C RE-LM -002 29

TEST #7

4

3

2

1

O;---+---t---1---+----~

3.300

3.500

3.700

3.900

4.100

4.300 TIME,

s

(39)

30 _{IME-CRE-CTR-002}

TEST #7

0 Q_ 2

w

₁₀

0::: ::)

c.n

U1 w 0::: 0...

w

(.'.)

₅

<{ 0::: w

ｾ＠

0+---+---+--- - -- 1--- -- ~ . ---1

0.000 0 . 100

0.200

0.300 0 .400

0 .50 0

AREA, m 2

(40)

'

_{d '}

..

,.

1 :'

I , ... ¥ifWi#gp;.l fal.Llf. ~ - -- - - · -· _ ,01:;'f! 2r,q !OIJ ｾ＠ jO,,!iqmu < ,.

.

ｾ＠

.,~

1.:: . ... .

'

ﾷｾ

ｾｾ＠

---~-,

'J'--,.jf~ ~:;r' __ ,

r-..

Fig.26. View of contact face after Tests 6 and 7 (left) and the location of the sampled ice block

(right).

I~

.:... 7-[T r '7 ...,.,

(41)

3 / L / L

i

I 1 - - - - ·-I I . _I _I

-· -· - 1-1

_! _I }

U-1

I l ;-,. j

I , ,

. I I / ; :; :

/

/ ·/

Fig.27. Sketch of Block I of Test 6 and 7 showing locations of thick sections, with re~pect to the original ice cover, taken for thin sectionong: Horizontal Section (l) , M id-Vertical Section (2) and Longitudinal Vertical Section (3).

oit o .. !IOI: ·oe,

°''

OH 091 O', I ,,., OCI oi, 011 00 1 010 019 01, 01·- ~s ·01~ ·01t 01t Oji wJ( ·1,u,,,~ 'lllli,1

°''

Oll 091 no;, Dt l ,.,, Cl.ii IH I uo, 016 01v Oil 019

ll'lh11lwl'.ILWl1WllJll1•~- hwl11 "l!111l1 11J1ul1.J1J., 1, ... 11 ,h,uls, I, • It •I• •I • l"' "11" 11' I l'l 'il l ., ,,.. 11h11• 11111111 lldll•lil"I!' ' u11h111 JJIIJiuJ.udlb1L111flll~piwiw:lulllLilllliku~111nl U~Q~ l;lrl I I'"'•· I 1, ' 1••'. ,o ,I I I I, 11-irl . " 1111 ,,,1 11'1 I ·

::-.. 1 ,i~~ '

·~· ·1

it,i,

·Ii ''I~

. ,,! ', ｾ＠ .1fl11 .• !' ｾ＠

' ·' (i1

! ., ,,.' .,

' ~ ,,,I: fjl_~· ( • lo :Ii fl • f • '"

I', ｾ＠ 'fl~, . ,

F ig.28. Top View of Block I (Test 6 and 7) befo re C ulling.

• • ..> t-..> ... -~

n

ｾ＠

()

•;j

·, 0 0 N

(42)

Fig.29. Photograph of horizontal thin section (l) of Blot:k 1 (Test 6 and 7) under c ross-pola rized }jght. The bottom end of the micrograph shows the contact smface and recrystall ized crushed zone.

Fig.30. Photograph of horizontal thin section (1) Block I (Test 6 and 7) under combination cross-polarized and scattered ~ght. Note the microcracks and macrocracks on the right.

'? hi ' \J ;;,::< rn

r

ｾ＠ C · 0 t .J I.,.) I.,.)

(43)

Fig.31 Photograph of longitudinal vertical thin section (3) of Block I (Test 6 and 7) under cross-polarized light shows that the ice was columnar-grained and vertically oriented at that location.

Fig.32. Photograph of mid-vertical thin section (2) of Block I (Test 6 and 7) under cross-polarized light.

Fig.33. Photograph of mid-vertical thin section (2) of Block 1 (Te~1 6 and 7) under combination cross-polarized light and scattered light.

l_µ ｾ＠

ｾ＠

()

ｾ＠

n

;j

.

0 0 r,,.J

(44)

11 .. .

.

... ｾ＠ • I ~r . 11 1,• ' _{·o • •}., : ·~ .: ｾ＠ •, o ~I IJ ,

...

Fig.34. Details of l1orizontal thin section (1) of Block l

(Test 6 and 7) under parallel-polarized light. Note the concentration of minute air bubbles (or inclusions) trapped in the

cmshed

zone at the bottom and along the

macro-cracks.

..

.r' .

l'

!ri.

m

t _ ,'~·

-.,m,~

[(~~

~' •,,~111,,:rari;tt 1 • • '

.... iMt, ,; · · "' ·

,'i(

~:r

,

.i,od~ J:it•~!1"'., ..• , .• l 'I" • , I • • 1' )1.;)t,,• , 11'°' • '" /f , , , , • ( ' l ,.. .1 .. .

•

\ . Jf.- ,,. " ,t_ r ~, ' ,· fl .,.ti\,;.• . , . . ) /.. · ~ ｾ＠ ' ' ·i~ . ｾﾷｾ＠

-·~ ..,,; ·.. . ... I U

IUHfltlllfll

l~:\];-,-~

l~ Uj,i

11 1

j,i

111 j

I

"r:

I~·~ '. .

Ii

l1

11m

li~fjl~Alti!Jll!f'!jj!

1

¥(

•, _{Ii ,} 11 HT - . ·; Tl" l .

nr

,,

I

J

I

-Fig.35. Details of mid-vertical thin section (2) of

Block 1 (Test 6 and 7) under cross-polarized light.

'/ ｾ＠ ' , ) ::0 l"T1 ' r' 3: ' N I.;.) V\

(45)

IME-CRE-CTR-002

VERTICAL ELEVATION

1 \

_i

INDENTOR

I

_l _- _{- - - -}

I

_-

_...

_-

-l E I I E

Bu

I l E I

:lJ

E I 0 ' 0 0 _' 0 0

I

'

: , B

I,()

...

I I \ i

-

--

---

..

- --

--I

I

'

I

1-

750 m r:, -- i I

ｾ＠

INDENTOR

TRENCH WA~

Ci2ot:;J

/ / / ( 1 7 7 /

ICE

SECTION B-B TEST NRC 8

(46)

l\1E -CRE-LM-002

NRC Test No: 8

Date and time : 1989 April 26, 10:45 Ice Face No: 1 O

SSW Test No: NRC 08

Actuator stroke: 70 mm Actuator rate: 100 mm.ls

37

Displacement transducers: transducer AD1 was used to measure motion of the

indenter with respect to the Ice of the trench floor. Transducer A02 was used to measure motion of tne actuator rod with respect to tne actuator body.

Accelerometers: Two accelerometers were placed on the indenter diametrically opposite each other.

Servo control: The signal from tne displacement transducer A01 (indentor with respect to ice) was used for control.

Notes: The whole system per1ormed satisfactorily. Because the indenter was shorter, about a 0.5 m thickness of plywood was used to shim up the reaction pad.

(47)

38

z

ｾ＠

-I.I..' u c:: 0 L c:: 0 I

-<

: ) I -u

<

IME-CRE-CTR-002

TEST # 8

5 I

4

3

2

1

0-+---,..--~----+---1---lf---1

3. 100

3.300

3.500

3.700 3 .900

TIME,

s

Fig.37. Load time record of Test 8. Average indentation rate

=

80mm/s.

(48)

E

I-z

w

ｾ＠

w

u

<

_{_J} CL (J) 0 I1\1E-CRE-LM-002

90

80

70

60 T

t c:. ,,,

....-v

T

40

30

20 -,cl

, ; 'v 4, ｾ＠ ' ' ' ' ;

A

I

I I

.

I ' I I

TEST #8

.. ... .. . ... •---.... ... ..

.... ...

\

...

,--····

wrt

.A.CTUATOR ·. 4

wrt

1c::

5

6 TIME,

s

Fig.38. Displacement time record of Test 8.

Average indentation rate

=

80mm/s.

.

' '

.

7

' ' 39

8

(49)

0 0... 2 (J) (J)

w

er::

I-V.' 40

1 5

(

I

'

(

l]

11. IME-CRE-CTR-002 0+-- - ---1--- -- - - + -- - -- -+-- - - - 4 - - - l

0.C

0.1

J.2

0.3 0 .4

0 .5

(50)

-I!'vffi-CRE-LM-002

Fig.40. View of contact face after Test 8 (top) and Jocation of the sampled ice blocks (bottom).

(51)

/

-) -

---4 ' J, /3 w:-

- - / ~

Fig.41. Sketch

or

Block 2 of Test 8 showing localm11s of thick sections, with respect to the o riginal

ice cover, taken for thin seclionong: HoriLontal Section (1), Mid-Vertical Section (2) and Longitudinal Ye11ical Section (3).

ｾ＠

I

"' . .

_ ,~ ;~ . ~ '..i . ~ - ~lo 6D

Bu

' I

.~

I , I T ｾ＠ I , .... f 1 ｾ＠ .. ;j.~,1.:.11,n,1, ,: ,qrr.;lmlJll'•ltll•l"t1l11111,.rtii,,1flli1iiaJ.ll.111u1,11~, 'i''ill' ,1111u,1111 •

9 0 100 110 1~ 130 t<O 150 180 ! 1to . 16() 1111) 200 210 '20 230 2,1() 260 260 270 2IO 290 300

\(

_..

ｾ＠ Fi~~ •1) TPp V i l"\\ . . , P.l11l k ' ( fr ·.1 :~:""I •. 1111 ' " ' " ' 111 1 111'" I , ... '?' ｾ＠

n

;;,:, :;1 ~· ' --l

IN

I

-1.-_.

(52)

. r

r.

[

_l

( [ [

Fig.43. Photograph of horizontal thin section (1) of Block 2 (Test 8) under cross polarized light.

Fig.44. Photograph of horizontal thin section (1) of Block 2 (Test 8) under combination cross-polarized and scattered light.

ｾ＠

()

ｾ＠

§

+"' l,.)

(53)

Fig.45. Photograph of longitudinal vertical thin section (3) of Block 2 (Test 8) under polarized light.

Fig.46. Photograph of longitudinal vertical thin section (3) of Block 2 (test 8) under comhination cross-polarized light and scattered light.

t

-?'

m

n

';rj cT1

n

ｾ＠

' ｾ＠ N

(54)

Fig.47. Photograph of mid-vertical thin section (2) of Block 2 (Test 8) under cross polarized light.

Fig.48. Photograph of mid-vertical thin section (2) of Block 2 (Test 8) under combination cross-polarized light. and scatterecl

light.

-

_ｾ＠

.

()

ｾ＠

r"'

ｾ＠ 6

8

ｾ＠ ( 11

(55)

46

SSW Test No: NRC 10

Jee Face No: 12

SSW Test No: NRC 10

Actuator stroke: 77 mm

TME-CRE-CTR-002

Displacement transducers : transducer AD1 was used to measure motion of the indentor with respect to the actuator body. Transducer AD2 was used to measure motion of the actuator rod with respect to the ice of the trench floor.

Accelerometers: Two accelerometers were placed on the Indenter diametrically opposite each other. ·

Servo control: The signal from the displacement transducer A01 (indentor with respect to actuator body) was used for control.

Notes: The whole system performed satisfactorily but the ice resistance was sufficiently high that the reaction pad moved backwards, compressing the plywood.

(56)

IME-CRE-LM-002

T

E E

8

0

..-VERTICAL ELEVATION

INDENTOR I I

l-1o

I

ｾ＠

E E 0 0 I() INDENTOR

SECTION D-D TEST NRC 10

Fig.49. Schematic of truncated wedge ice face for Test 10.

(57)

48 IME-CRE-CTR-002 TEST # 10

4---.Z

_{3 .}

ｾ＠

.

w

u

a:::

0 LL-

₂

a:::

0 I-<{ ::)

I-u

₁

<{

0+---...i.---+---+---4---1

3 .800

3.900

4.000 4.100

4 .200

4.'3 80

TIME, s

(58)

IME-CRE-LM-002 ₄₉

TEST

#

10 E

300 wrt

E

I-z

w

2

w

280 u

:5

_wrt

_ICE

Q_ (./) 0

260

ＲＴＰＭＫＭｾｾｾｾｾｾｾｾＭＫＭｾｾｾｾＭＫＭＭｾｾｾＭＫＭｾｾｾｾ＠

3.800

3.900

4.000

4.100

4.200 4 .300

TIME,-s

(59)

50 IME-CRE-CTR-002

TEST

#

10

0 0... 2 ' w 0::: ::>

ｾ＠

(/) (/)

1 0

---w

er::

_ｾ＠ 0...

w

c.:> <( 0::: w

>

<( I

0 -+---,+---+,---+-:---+:----~

0.000 0. 100

0.200

0.300

0.400

0.500 AREA, m2

(60)

r

(

r

_l

l.

{ [ ( ( (

Fig.53. View of contact face after Test 10 (left) and location of the sampled ice block (right).

l

ｾ＠

()

ｾ＠

r ｾ＠I 0 0 N VI ...

(61)

,f

/3

...

,

. . ·-1· . ··-- ·· \ ... I • I '

.,

1 ' I

. v1

~ ,f ! I l I 2 '

1

ｾ＠ I .

'

' I ' • '

ｾ＠

,

•' fy

. ;

!

l . . ··- ·- .

/

,:

ｾ＠ｾ＠

·--

ｾ＠

.,--·

"

I --- -- ·--

ｾ＠

I

'

_{... ... p·-}

,.,,..--l -

-/ ,-

_I

_.I

.,

--!

r

ｾ＠

r , /'

:-

' /

I ;

·- ---'--;.

______ _

Fig.54. Sketch of Block 3 of Test 10, Face 12 showing locations of thick sections, with respect to the original ice cover, taken for thin sectionong: Horizontal Section (1), Mid-Vertical Section (2) and Longitudinal Vertical Section (3) .

'\,,

n111_{•rJ"'~' ~·'!l';~"l"ji·}_{11 1 ·· ,1}_{•r r}_I_j _{1 ,·} _{1 ,} ₁

l ~

I ,,

_{· 1 ;'.~1,1r , • r ,h j 11r1,1,1, ,," ,1n:C,,,~ ·,fF~ ~n·11,1mq11~} _{, , 1} _{•'l ·'i''l.,,,,:'1}~~~;';}

rm,Yt O 210 3 1o 4 0 Sfn fil,) 71o 80 Ulo ,oo 1 10 1111 13 .i IOO '~t • o :;:o l:ll) '40 ISO 160 1 0 180 t QO 200 210 Zl'J 230 240 2bO ｾ＠ '70 ,M ti!) :lJ6•

----·- ··· ·--··• - ... ····- - .. - - . · ··- -- • ... -"' ' ' ~- .. . - ··- ·-· --·· ~- - l .,...,:: ｾ＠ｾ＠ ... '1.[ 1-:

·~\

_{,. .}

"' 1'k

'!I

,1 >

:~

f

ｾ＠ .I,!.

'

"j

"

\

'

,, l',i;

, ;. !' • ' •

,,,.

,

·1 Iii'',

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(62)

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or

horizontal thin section (2) of Block 3 (Test 10) under combination cro.ss -polarized light and scallcRxl light.

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or

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56 I!vfE -CRE-CTR-002

Appendix 1

IN SITU MULTI-YEAR SEA ICE STRENGTI I USING NRCC BOREHOLE INDENTOR

Ni rmal K. Sinhi.:

Insti tute for Mechanical Engineeiing, t--1 -1 'i

National Research Council of Can::da Ottawa, Ont~rio, Canada K lA OR6

Abstract

A borehole indenter system, including a fibre-glass core auger, was developed at the National Research Counci l of Canada (N RCC) to conduct in situ tests over a wide range of penetration velocity. This system proved ideal for the data collection program and microstructural failure analyses o n the Ice Island multi-year consolidated sea ice in the High Arctic. The tests indi cated that local p ressures up to 40 Mpa could be generated in cold ice

( -19 °C) during ice/structure interactions for a displacement rate

of 0.2 mm s·1. I ntroduction

. In addition to the multitude of structural features, natural ice shows a great deal of trapped impurities. The purity o f ice depends on the p urity of the wate r or the melt from which the ice grew. Freshwater ice contains a fair amount of impurities usually in the form of air bubbles. These bubb les are elongated in columnar grained ice with the long axis of the bubbles parallel to the Jong axis of the grains. These inclusions, however, pose no problems if blocks of ice are to be recovered for tests to be comlucted at late r dates. Sea ice, o n the other hand, contains significant amount of hrine, in addition to air bub bles. in the form of pocke ts trapped between th e grains and the subgrains. Even the old mu lt i-year sea ice, as will he described later in this P.aper, could contain a s ignificant amount of t rapped hrine. There is a marked tendency to desalinate if the ice is sampled whe n the ambient a ir temperatures arc high. 1l1is is a chronic problem in the sampling and testing of sea ice. Mor eover, shipping ice to distant laboratories is always very risky; the author, on many occasions, has seen bags of water at the end of the journey. There is a potential, the.refore, to alleviate some of the sampling

problems if in situ tests could he carried out on ice.

A new bureliole indenter test system and test methods were develo ped at th e National Research Council of Ca nada (NRCC). Tbe new test system proved idea l for studying the

strength decav of Dows Ll!ke ice cove r in Ottawa -:wir:1: 11,~

spring thaw i~ 1987 (Sinha, 1990). The ice cover i, J,cJ ;\<.: :,

winter for public skating and there is a need to evah:a :e i:s s:,:<:

use. The test system was also fol!nd to be id?al :or J,.: .,

collection program on the Canadian Coast Guard Ship ;Si, Jc:-r: Franklin' during the Lahr"dor Ice ~1argin Exp~r:me:it J9s;o (LIMEX-89) in March, 1989. Over one hi.:nJrcJ ;.,;, t, wcr-: conducted using this sysrem fnr de ,e rmir.ing in .w11 mc c;wn;c1l behaviour of warm sea ;ce in the Lllbra::o~ Se:!. Th e :~otde -f re~ operation and successful me of the ~RCC brn el1ole i11dc11tw during th is field operation !,'.:l\'e u~ t:ic confid.:r;<.::.: tu tak<.: 111 :~ system to the Ice lslancl in April, 1989 w;,:::n rr.cdiurn ,ct!-: indentation tests were also carried out (Frederking et :ii.. 199;:;.

The following is a sho~t report to give a g,irr.pse o :" tl·e resu l:s

NRCC Borehole Indenlor

The NRCC borehole indentor Uack) was deve hiped ;n

1985 after using and evaluating available existing sv, tcrns in : 1:.::

High Arctic (Sinha, 1986; 1987). It operates ir :i : SU n:11 d iameter (D) vertical borehole in ice (Fig. 1). The tes: h;iles a~e drilled through the ice cover using a fibre-glass core aug~·r a ., ,. ma<le at NRCC. Load is applied hydrau lical ly to pu ~h pl;1,c, o 1 opposite ends of th e indcntor against the sides of t:1e bor?hn'c. The plates are screwed to the actuat ors. If required, : 1:.: configuration allows the geometry and construction d~t.:ib l>I ti!: plates to be changed if required ·such as insertion of tc:n pc ra tL r:

probes and miniature load cells. The 90 mm diarne:er polished stainless steel plates (R₀), used <l uring the present test ser:es. U ·~

curved in one plane to match the curvature of the wall (F:g. 21. During a tes t the plate pressure is registered on a dial g;1u£! ~ attached to the supply line and the pressur e can be recor<l~,.l manually. There is provision a lso for recording the µres su: ~ arid the displacements of the t.vo plates and he nce t he torn · cii,1me: ·:1l displacement as functions of time, t:sing a strip chart recorJ? r ,,, well as a d igital data logger. A transducer in the hydraulic ,vs:r:n

is calibrated to give the average applied pressure on the p· u e~

(averaged ove r an area of 6.5 x 103 mm2), and two LVDT ,:, JJ~

Proceedings 10th International Conference Offshore Mechanics and Arctic Engineering. iOMAE/ASMF.), SLavanger, Norway, June 23-29, 1991, Vol.4, pp. 229 - 236.