Approaches to reduce or impede the degradation of concrete in a marine environment by ice include the choice of concrete, the selection of the structural shape and the application of coatings to inhibit abrasion. To inform these approaches, it is necessary to understand the underlying mechanisms that lead to wear, so that appropriate design considerations may be made. This paper examines one such mechanism, the adhesive effects of large-scale (bulk) ice on concrete. Recent laboratory results are placed in context with previous laboratory programs to examine both what we know about parameters that influence the ice-concrete adhesion bond and if these parameters may lead to wear. Key parameters that affect the bulk bond are contact area, bond time, displacement rate, whether an applied load was present during bonding and the mechanism of bonding. Greater adhesive bonds were also found when bonding ice to pure cement paste compared to component aggregate or concrete. It is shown that generally-unreported parameters related to the concrete surface are likely to also play a role. Ice adhesion to concrete leads to material loss, although at a reduced volume compared to that observed in frictional studies of ice. Direct correlations between individual test parameters and wear were not feasible under most test configurations. Field conditions that could lead to ice adhesion to concrete in a marine environment and the initiation of wear include scenarios with a slow-moving loading condition, a longer bond time, under some pressure, and wet (but not submerged) bond formation.

This paper presents the results of a laboratory test program designed to investigate the adhesive effects of large-scale (bulk) ice on concrete. Medium-strength concrete cylinders were sawn into discs, and attached to a sample table. Freshwater ice samples, frozen using smaller, standard-sized concrete cylinders, were adhered to the concrete with both varying bond times and added weight during bonding. Shear strength tests were conducted at a set displacement rate, under a number of temperatures. The effect of these variables on the adhesive strength of ice to concrete was examined, as well as whether there was any noticeable removal of concrete cement paste or aggregate during testing. The tests indicate that the adhesive strength is negligible when the method of adhesion is “dry” (no liquid layer at the onset of adhesion). Tests with “wet” adhesion indicated a significantly higher strength. The nominal versus the apparent contact area had significant implications for the determination of the adhesive strength of the bond between the ice and the concrete. Removal of cement paste was evident in a number of tests, however the amount was not significant. The results have relevance for design of structures in a marine environment, such as revetement dams or rubblemound breakwaters, as well as for the standardization of adhesion tests with ice and concrete.

Damage of concrete in a marine environment by ice can result in significant degradation of a structure, leading to increased maintenance costs, decreased structural resistance, and decreased operational lifetime. There are a number of approaches to reduce or impede these impacts, such as the choice of concrete used, selection of the structural shape, and coatings to inhibit abrasion. In order to inform these approaches, it is necessary to understand the underlying mechanisms that lead to abrasion, so that appropriate design considerations may be made. Degradation of concrete through the frictional effects of ice is a key component of mechanical abrasion. Adhesion in turn is one of the key components of static friction. This paper examines the state of knowledge of the adhesive effects of large-scale (bulk) ice on concrete and presents the challenges in comparing results across test programs due to the lack of standard test procedures. Research directions are proposed, both to reduce challenges in cross-comparison of research results and to further advance our understanding of the contact mechanics at play in adhesion of ice to concrete and its effect on damage.

Maintenance and repair of ice-worn concrete structures in marine environments are ongoing challenges. Practical solutions for reducing ice-wear for large-scale applications have had marginal success rates to date. We still do not really know the relative degrees of abrasion caused by mechanical wear, freeze-thaw cycling, pore water pressure, or seawater chemical effects. What is happening at the interface between ice and concrete and is there a link between wear and adhesion processes? Many studies have examined ice and concrete adhesion: twist, push and pull tests on concrete piles frozen into ice; direct shear tests of ice on concrete; and investigations into the frictional wear of concrete by ice. How do contact mechanics influence the shear and tensile adhesion bonds between these two substances? This paper outlines a programme that seeks to inform not only our knowledge of adhesion loading, but also how adhesion may influence the initial high rate of wear that is common to ice abrasion of concrete. The presented test programme is using a suite of methodologies to examine ice-concrete adhesion. Three approaches are outlined, with an eye towards answering the questions above, for a comprehensive evaluation of ice-concrete adhesion bonding.

Abstract The Drake pipeline is located offshore Melville Island, in the Canadian High Arctic. It was built on-site in 1977-78 and connected to a natural gas production well, which operated for only a few months. The well was plugged in 1995 and the pipeline was abandoned. The pipeline extends from the shoreline to the wellhead located about one kilometer offshore to a water depth of 55 meters. It is buried at the shoreline crossing, to a target depth of 1.5 meters below sea bottom. A system to generate a frozen soil shield was also devised for further protection against drifting ice. Also, a berm made from ice and gravel was built at the water line. Field investigations could prove highly instructive to assess the state of the structure, and provide guidelines for design of future pipelines in high risks areas. However, significant technical and logistical challenges would face that venture, namely a ‘no physical contact’ (with the pipeline) restriction from the property owner, which leads to difficulty in understanding what has occurred to the pipeline beneath the soil, and a propensity for the region to be covered with a very thick ice cover.

Large grounded ice features can be found in all regions of the world where there is moving ice. This paper compiles over 230 reported ice pile-ups from several international locations including the Baltic Sea, Gulf of Bothnia, Caspian Sea, Lake Simcoe, Stonehaven Harbour (New Brunswick), west Newfoundland, Alaskan and Canadian Beaufort Sea, Norton Sound, Bering Sea, Somerset Island and offshore Sakhalin. The NRC Particle-in-Cell numerical model is used to augment the data. A plot of the rubble sail height as a function of the ice block thickness shows considerable scatter but a general increase in sail height with increasing ice thickness. The scatter in the data is real and is attributed to the fact that the conditions for producing the maximum sail height are not met in most situations. An upper bound of the data can be represented by Hs,max = 19 hB0.33 where Hs,max is the maximum pile-up height (in m), and hB is the block ice thickness (in m). This equation covers the data range up to 2 m in ice thickness. The data also clearly show that high pile-ups (on the order of 10 to 12 m high) can be generated from thin ice less than 0.5 m thick. Further, sail heights up to 30 m are possible for thicker sea ice.

This paper provides the details of ice loading events that can be used to further the understanding of pack ice driving forces in the Beaufort Sea. Several methods have been reviewed and employed including in situ stress measurements, loads on the Molikpaq offshore caisson, shoreline pile-up events, pile-ups and rubble fields on offshore shoals and relic berms, analysis of shear walls on offshore rubble fields, and analysis of deep ridge keels. Over 50 different events are identified with 33 suitable for a pack ice analysis. The data are considered in terms of both the ISO 19906 (2010) Arctic Structures Standard and pack ice pressures that can be exerted across various widths. A new approach is proposed, in which the calculated and measured values from past pack ice pressure events are used to predict limit force.

Abstract In northern regions, ice forces, or actions, must be considered in the design of structures such as light piers, bridge piers, and offshore platforms. Estimates of ice forces in Canadian waters are usually obtained by consulting design standards such as those developed by the International Organization for Standardization (ISO) and the Canadian Standards Association (CSA). These design standards draw on available analytical formulae. Field measurements are available from several sources that suggest reasonable agreement with analytical results for simple cases involving wide structures. One of the remaining uncertainties in estimating design loads, however, is the contribution of force imposed below the waterline due to unconsolidated keels of ice ridges. Only cursory guidance is provided by the standards associations and their analytical design equations. Close inspection of those formulae show that force estimates can become excessive in situations where the expected keel depth is great compared to the designed structure width. Such scenarios would be expected in offshore oil and gas operations where drilling risers, jack-up legs, and even jacket structures may be exposed to ice ridges. The present work examines available approaches for evaluating ridge keel forces, including passive pressure calculations. The processes of ice rubble failure and the corresponding stress distributions are considered in the context of classical soil mechanics applied in geotechnical engineering. Design standards are also used to calculate ice forces for a range of ridge keel properties, keel geometries, and structure design widths. Field measurements from the Norströmsgrund lighthouse and the offshore Molikpag caisson are then examined and compared to the forces obtained using these approaches. The authors conclude that the shape factor adopted in ISO 19906 plays an important role in calculations considering narrow structures and deep keels. It is also shown that the sensitivity of ridge keel load calculation to geometric factors varies considerably with structure width. Furthermore, an absence of real world data from ridge keel interactions with very narrow structures precludes validation of present models in these situations and should be the focus of data collection and model refinement.

This paper discusses the results from an integrated research project, carried out over many years, which examined a variety of evacuation strategies for offshore structures in the Beaufort Sea. The objective of the project was to address the safety of offshore personnel working in Canada’s Arctic environment, by examining the issues surrounding emergency evacuation from an offshore structure under the diverse range of conditions in the Beaufort Sea. This was accomplished through: the development of decision flow-charts for the establishment of on-ice evacuation shelters and their associated costs and logistics; field measurements of personnel movement rates across different ice morphologies; an investigation into ice rubble stability and roughness and its influence on evacuation systems; an examination of ice management options when ice rubble is present around an offshore structure; and the presentation of generic means of evacuation and their adequacy for four “seasons” of evacuation: open water, moving pack ice, quasi-stable rubble and stable rubble/landfast ice. The project results provide 1) information related to the viability of systems for a range of realistic ice conditions, especially those involving ice rubble, 2) provide input into the development of the evacuation and rescue options and strategies for Beaufort Sea structures and 3) be used by Operators and Regulators to examine the feasibility of proposed evacuation systems for the Beaufort Sea.

Experience with past offshore platforms in the Beaufort Sea has shown that in some regions, a stable rubble field of ice may surround the platform during the winter months. These rubble fields can influence marine operations, emergency evacuation systems and can reduce ice loads on the platform. This paper analyzes the historical rubble information that has been collected pertaining to the nearshore Beaufort Sea and it examines potential empirical relationships between rubble field characteristics and a variety of ice and environmental parameters. Historically, offshore structures in this region were in open water for approximately 100days. During the remaining time, quasi-stable, grounded rubble could be present around a structure for extended periods — for example, on average 65% of the time that there was moving pack ice in the autumn. Rubble fields formed between 76%–87% of the time when a drilling structure was in water depths from 5 to 32m. This review shows that grounded rubble fields in the Beaufort Sea can be extensive with areas up to 1km2 with maximum sail heights up to 14m. The extent and shape of each field is interdependent upon a number of factors, such as water depth, number of days the site is in moving ice, and the size and shape of an island, caisson or a submarine berm. But no one factor could guarantee the formation of grounded rubble. Upper bounds to the size of a rubble field are proposed based upon three separate data sets. The potential presence of rubble to such a great degree indicates that operators should clearly identify the strategies to be used to either manage grounded ice rubble or account for its presence with respect to marine operations and emergency evacuation methods. However, the data also show that rubble fields often don't form, even if conditions seem to be favorable for their formation.

Abstract A simple analysis is presented to examine the forces necessary to create a large shear wall of ice which was observed in the Beaufort Sea. This shear wall was approximately 130 m long and 23 m high (from the seabed). Two types of analysis are presented. First, a distinct feature of a 0.8 m thick ice floe which had been pushed up the 8 m high (above the ice level) rubble pile was analyzed by considering a number of analytical models for ice ride-up. The analysis showed that the line loads were estimated to be on the order of 65 to 150 kN/m, and 90 to 208 kN/m for friction values of 0.3 and 0.5 respectively. A second analysis of the creation of the shear wall by a large-scale shearing event suggested the global force would have been on the order of 42 to 90 MN. These values are in agreement with measurements of global ice loads on offshore caisson structures. The analysis was extended to estimate the pack ice driving force for this event. Although a number of gross assumptions were made, the calculated values are in good agreement with other previous estimates of the pack ice driving force in the Beaufort Sea. Overall this study has indicated that observations of these large ice features and subsequent analysis can be a very useful method for gaining additional insight on pack ice driving forces.

Abstract As an ice sheet impinges on the surface of a cone, flexural failure takes place. That ice failure mode causes substantially lower forces than the case of compressive failure, which would take place if ice is to encounter a vertical structure. Previous work by the authors employed a numerical model of ice dynamics in order to predict ice failure patterns and forces on a conical structure. In an initial paper, simulations examined the role of the slope of the cone and the case of ice failure against inverted cones. That study indicated that the slope plays a role on ice loading. Later results, published at ATC 2014, then examined in more detail the roles of structure slope, friction on ice pile-ups and loading on a conical structure and compared the results with the analytical methodology presented in the ISO 19906 Arctic Offshore Structures standard. The present analysis continues to expand the work to examine the role of structure diameter on ice loading and pile-up height. Results are further compared to ISO 19906, with the objective of presenting concrete guidance for the current revision of that standard. Ice forces on upward-breaking cones as a function of structure slope, waterline diameter, ice thickness and ice-structure friction are presented. The results of the study are relevant for structures in ice, such as offshore drilling platforms, bridge piers and offshore wind turbine foundations.

Abstract Conical structures are often used to ameliorate the action of floating ice. There is a long history of using cone-shaped bridge piers. Moreover, many recent designs adopt downward-breaking cones to further reduce ice forces. The present work aims to clarify aspects of ice interaction with cones that are poorly understood. This work builds on a previous study that employed a numerical model of ice dynamics in order to predict ice failure patterns and forces on a conical structure. Performance of the model was validated against available ice basin tests, and the study examined a test case representing a pier of the Confederation Bridge, Canada. The present tests examine the roles of ice-structure friction and shape of the cone (upward- or downward-breaking) in more detail. Additionally, the effects of ice thickness and embedded consolidated ridges are examined. The results reveal trends of the dependence of the modes of ice failure and the resulting forces on ice-structure friction, slope and the type of the cone (upward- or downward-breaking). For upward-breaking cones, ice-structure friction proved to be more significant for gentler slopes than for steeper ones. For those cones, ice failure appeared to correspond to three-dimensional buckling. Downward-breaking cones displayed a different behavior with downwards bending failure. The value of the ice-structure friction coefficient had a clear influence on the forces for all downward-breaking cases. The results also support the idea that downward-breaking cones correspond to lower horizontal forces than those acting on upward-breaking cones. Concerning ice sheet thickness, peak horizontal ice forces show a near linear dependence on the thickness. For large consolidated ridges, forces increased substantially. The numerical model results are compared with the elastic beam bending approach given in the ISO 19906 Arctic Offshore Structures Standard for ice loading on a sloped structure. In order to use the equations in ISO 19906, assumptions must be made on the maximum accumulated rubble height and other parameters, which affect the calculated load. The peak loads from the model and ISO approach are similar for level ice interactions, although the ISO approach is more sensitive to ice-structure friction. Also, the ISO approach may overestimate the load generated by some ridge geometries.

Abstract There are large oil and gas resources in the shear zone region of theBeaufort Sea. Development of these resources would entail many factorsfor consideration. One of the most important is the ice load on drillingand production platforms. However, there is very large uncertainty on theice loads in this region due to a clear lack of knowledge of the pack icedriving forces. This pack ice driving force is one of the primarymechanisms that dictate how much force the ice can exert on an offshoreplatform, even if large multi-year ice floes are present. Improvedknowledge of this force would significantly reduce uncertainty in the designice loads, provide essential baseline engineering knowledge and a more reliablestructure, leading to greater regulatory certainty and safer and moreeconomical offshore operations. The pack ice driving force, as a function of width, can be calculatedthrough an equation in the ISO Arctic Offshore Structures Standard. However, a relevant parameter is still poorly defined for this equationand spans a large range. As a result, calculations of driving forces arevery uncertain, yet it is the key limiting force mechanism for the BeaufortSea. This paper presents the results of a study that investigated meansof refining uncertainty when calculating pack ice driving forces. Anoverview of the standard method of determining these forces is given, as wellas a discussion of the historical development of, and implications ofuncertainty in, calculating the pack ice force. Methods for refining theuncertainty are presented and comparisons are discussed. Numericalmodelling studies offer the greatest potential for refining the uncertaintybased on cost, usefulness, confidence in the results and studyopportunities. The information provided in this paper has applicationsfor refinement of pack ice driving force calculations in current engineeringstandards. A clear understanding of the magnitude of pack ice drivingforces would help to reduce the risk of failure of engineering structures andimprove their safety, by enabling a significantly better definition of theanticipated ice loads and the upper limit of the loads for the BeaufortSea.

As an ice sheet impinges on the surface of a cone, flexural (or bending) failure is likely to take place. That ice failure mode causes substantially lower forces than the case of compressive failure, which would take place if ice is to encounter a vertical structure. Some designs further adopt inverted cones, as downward-breaking of ice may produce lower forces. The present study employs a numerical model of ice dynamics in order to predict ice failure patterns, ice clearing around the structure, and forces on the structure. Performance of the model is validated against tests done in the Esso Resources Canada Ltd. ice basin during 1989 and 1990. The paper then proceeds to examine a test case representing a pier of the Confederation Bridge. The results are compared to available observations. Simulations also examine the role of the slope of the cone and the case of ice failure against inverted cones. Comparison of downward- breaking and upward-breaking indicate that the slope plays a role. For a relatively steep slope of 52 o , the downward-breaking cone experiences a substantially lower force than the upward- breaking cone. For a gentler 40 o slope, the downward- and upward-breaking cones experienced similar values of peak ice forces. The results have applications for bridge pier and offshore wind turbine tower designs, offshore oil and gas exploration and production structures, and standards development, such as the ISO 19906 Arctic Offshore Structures standard, which also has applications for temperate regions.