Ice Pressure Research Articles

STUDY ON THERMAL ICE STRESSES OF A POND IN COLD REGION

Static ice pressure due to thermal expansion is a key parameter for the design of hydraulic structures in cold regions. Thermal ice stress is affected by various factors, including thermal conditions of ice sheet (ice temperature, temperature rise rate, etc.), ice sheet constraint conditions, ice sheet thickness, etc., which leads to uncertainties in the estimation of thermal ice stress. To investigate the spatial and temporal distribution of thermal ice stress, a prototype observation was conducted to No.6 pond of Qinghuahu lake in Daqing City, Heilongjiang Province, and the ice temperature and thermal stress were fully analyzed. The analysis results indicate that ice temperature mainly depends on the fluctuation of air temperature, and that the ice temperature of each layer fluctuates more gently with time than air temperature. With the increase of ice depth, the fluctuation range of ice temperature decreases, and ice temperature increases. The surface ice temperature is well linearly related with air temperature by the change rate between 0.38 and 0.56, and the influence of air temperature on ice temperature is quite obvious within 30 cm, and ice temperature below 30 cm presents a linear distribution along depth. Based on Bergdahl's rheological constitutive relation of static ice, a mathematical model of thermal ice stress is proposed. The undetermined parameter in the model is determined by regression combining with measured data, and its values obviously depend on measuring positions. The calculated values of ice stress agree well with the measured ones. From station 1 to station 4, the overall thermal ice stresses increase. The stress is non-monotonically distributed along ice depth, i.e., thermal stress in surface ice is slightly smaller, reaches a maximum at the depth of 10~30 cm, and then gradually declines with depth. Moreover, thermal ice stresses only appear on the upper part of the ice within 0.7 m.

Ice pressure and icing volume expansion rate of acetate-based deicers under freezing conditions

Acetate-based deicers are frequently used as airport pavement de-icing fluids in cold regions. In this study, the ice pressure (Ip), icing volume expansion rate (ΔVP), freezing point (T0), and undercooling degree of acetate-based deicers were investigated. The above mentioned indices were also compared with that of water and NaCl deicers. The results showed that the cooling process and ice crystal growing process of acetate-based deicers could be divided into five stages. Additionally, the stabilised values of Ip and ΔVP decreased with the deicer concentration increases. Furthermore, the impulse concept of ice pressure (IPI) was proposed to evaluate the frost damage of concrete caused by deicers. The Ip, ΔVP , and T0 values of calcium magnesium acetate (CMA) deicer with different Ca/Mg mole ratios (i.e. 1/1, 0.91, 7/3, and 3/7) were tested in the ice pressure test. The value of CMA deicer with 3/7 Ca/Mg mole ratio was the lowest. However, the Ip values of CMA deicers with 0.91 Ca/Mg and 1/1 Ca/Mg mole ratios were the highest. Among all the tested acetate-based deicers, CMA deicers had the lowest values of Ip, ΔVP, and IPI. Moreover, the CMA deicer with 3Ca/7Mg mole ratio was recommended for deicing airport pavements to reduce the concrete frost deterioration caused by acetate-based deicers. In this study, we investigated the physical properties of acetate-based deicers, quantitatively analysed the destructive power of deicers in a freeze–thaw test, and studied the cause of freeze–thaw deterioration of concrete. Overall, this study provides a theoretical method for exploring new deicers.

The Comparison of The Effectiveness of Local Ice and Manual Pressure Application in Decreasing Pain Related to Intramuscular Injection

Objective: Because of the pain they cause, injection applications can constitute a negative experience for both the patients and the nurses performing the application. This study was planned to compare the effectiveness of local ice and manual pressure applications in decreasing the injection pain experienced by patients. Methods:This study performed a university hospital in Turkey. Onehundred and five patients,45 in the lokal ıce group, 45 in the manuel pressure group and 45 in the control group, met the inclusion criteria and completed the study. The local ice group received cold ice application to the injection area before injection. The manual pressure group was received 10 seconds of pressure applied by the researcher to the injection area before injection. The control group received routine injection. Study data was collected using The Wong‐Baker FACES Pain Rating Scale and The Visual Analog Pain Scale. Results: A statistically significant difference among the groups with regard to mean WBS and VAS scores was found as a result of the study. The control group received a higher score compared to the groups which underwent manuel pressure and local ice applications. Conclusions: It was concluded that local ice and manuel pressure applications before IM injections were effective in decreasing the injection pains of patients.

Effects of steel fibers on failure mechanism of S-UHPC composite beams applied in the Arctic offshore structure

A novel steel–concrete–steel composite structure constructed using ultra high-performance concrete (forming an S-UHPC composite structure) was applied in Arctic offshore structures. This type of structure can withstand ice pressure derived from impinging sheet ice in the Arctic region. In this study, the failure mechanism of S-UHPC composite beams was explored experimentally and analytically, considering the effects of steel fibers in UHPC. Five groups of push-out tests were conducted to reveal the interfacial performance between steel plates and UHPC. Static tests on S-UHPC composite beams were performed to study their structural behaviors. The results indicate that steel fibers have a significant effect on the failure modes, slippage behavior, and mechanical behavior of the S-UHPC composite beams. Furthermore, on the basis of test results, finite element (FE) models of the push-out tests and static tests of the S-UHPC composite beams were developed and validated. Further, a parametric study was carried out to summarize the failure modes of the push-out tests and to explore the influence mechanism of steel fibers on the structural behavior of the S-UHPC composite beams. Finally, an analytical model for predicting the ultimate strength of S-UHPC composite beams was proposed and compared with existing design codes.

The Three‐Dimensional Light Field Within Sea Ice Ridges

AbstractSea ice pressure ridges have been recognized as important locations for both physical and biological processes. Thus, understanding the associated light‐field is crucial, but their complex structure and internal geometry render them hard to study by field methods. To calculate the in‐ and under‐ridge light field, we combined output from an ice mechanical model with a Monte‐Carlo ray tracing simulation. This results in realistic light fields showing that light levels within the ridge itself are significantly higher than under the surrounding level ice. Light guided through ridge cavities and scattering in between ridge blocks also results in a more isotropic ridge‐internal light field. While the true variability of light transmittance through a ridge can only be represented in ray tracing models, we show that simple parameterizations based on ice thickness and macro‐porosity allow accurate estimation of mean light levels available for photosynthesis underneath ridges in field studies and large‐scale models.

A novel model of heat-water-air-stress coupling in unsaturated frozen soil

The accurate prediction of frost heave in unsaturated frozen soil is crucial for the construction and protection of projects in cold regions. The occurrence of frost heave in unsaturated frozen soil is accompanied by an extremely complicated process of heat and mass transfer, which is closely related to the temperature gradient, water migration, air transfer, latent heat, deformation, overburden pressure, and so on. Based on thermodynamics and continuum mechanics, a comprehensive coupling model is proposed to describe the temperature variation and liquid water/vapor redistribution in unsaturated frozen soil. The Clapeyron equation was used to establish the relationship between the ice pressure and the water pressure during phase equilibrium. The initial water content of the frost heave, frozen fringe, and consolidation compression deformation are also introduced into the model to calculate the frost heave in unsaturated frozen soil. The proposed model was validated through a comprehensive experiment wherein a unidirectional freezing test was performed on a soil column in a closed system in our lab. The well-known experiment conducted by Mizoguchi and the simulation of this test by other study were also considered to validate the feasibility and adaptability of the model. The results reveal that the temperature variation, total water content distribution, and frost heave obtained by the proposed model are consistent with the measurement results.

Fracture stiffness evaluation with waterless cryogenic treatment and its implication in fluid flowability of treated coals

Cryogenic fracturing using liquid nitrogen is a waterless and environmentally friendly formation stimulation method for creating complex fracture networks effectively. This study developed a non-destructive geophysical technique using seismic measurements to probe fluid flow through coal and ascertain the effectiveness of cryogenic fracturing. A theoretical model is established to determine the fracture stiffness of coal inverted from wave velocities, which serves as the nexus for correlating the hydraulic and seismic properties of fractures. In response to thermal shock and frost forces, visible cracks are observed on coal surfaces that deteriorate the mechanical properties of the coal bulk. Consequently, the wave velocity of frozen coal specimens exhibits a general decreasing trend with freezing time under both dry and saturated conditions. For a gas-filled specimen, both the normal and shear fracture stiffness decrease monotonically with freezing time as more cracks are created in the coal bulk. For a water-filled specimen, ice formation due to cryogenic treatment leads to grouting of the coal bulk. Accordingly, the fracture stiffness of wet coal increases initially and then decreases with freezing time. A coalbed with higher water saturation is preferable when applying cryogenic fracturing because fluid-filled cracks can endure larger cryogenic forces before complete failure, and the contained water aggravates coal breaking as ice pressure builds up from the volumetric expansion of the water–ice phase transition and applies additional splitting forces on pre-existing or induced fractures and cleats. Also confirmed is that the stiffness ratio is sensitive to fluid content. The measured stiffness ratio is 0.7–0.9 for dry coal but less than 0.3 for saturated coal. The present findings provide a basis for realistic estimation of coal stiffness ratio for future discrete fracture network modeling.

Discrete Element Analysis of High-Pressure Zones of Sea Ice on Vertical Structures

In cold regions, ice pressure poses a serious threat to the safe operation of ship hulls and fixed offshore platforms. In this study, a discrete element method (DEM) with bonded particles was adapted to simulate the generation and distribution of local ice pressures during the interaction between level ice and vertical structures. The strength and failure mode of simulated sea ice under uniaxial compression were consistent with the experimental results, which verifies the accuracy of the discrete element parameters. The crushing process of sea ice acting on the vertical structure simulated by the DEM was compared with the field test. The distribution of ice pressure on the contact surface was calculated, and it was found that the local ice pressure was much greater than the global ice pressure. The high-pressure zones in sea ice are mainly caused by its simultaneous destruction, and these zones are primarily distributed near the midline of the contact area of sea ice and the structure. The contact area and loading rate are the two main factors affecting the high-pressure zones. The maximum local and global ice pressures decrease with an increase in the contact area. The influence of the loading rate on the local ice pressure is caused by the change in the sea ice failure mode. When the loading rate is low, ductile failure of sea ice occurs, and the ice pressure increases with the increase in the loading rate. When the loading rate is high, brittle failure of sea ice occurs, and the ice pressure decreases with an increase in the loading rate. This DEM study of sea ice can reasonably predict the distribution of high-pressure zones on marine structures and provide a reference for the anti-ice performance design of marine structures.

Validation of a thermo-hydro-mechanical model of freezing of water-saturated soil based on laboratory tests results

Frost heave of freezing water-saturated soils is an important worldwide problem from an engineering point of view. In cold regions, this phenomenon significantly affects foundations of buildings and road pavements. Application of artificial ground freezing to underground construction due to frost heave can cause an undesirable uplift of the ground surface and an increase in pressure acting on a lining and frozen wall. In the present paper, a mathematical model of soil freezing enabling one to predict soil deformation due to phase transformation of pore water into ice is proposed. The model is based on a set of nonlinear equations of water transfer, heat transfer, and equilibrium which are solved relative to porosity, temperature, and displacement variables. Constitutive relations of the poromechanics theory along with Bishop-type effective stress are used to simulate the mechanical behavior of soil during the process of pore water freezing and to evaluate pore pressure depending on a changein porosity and volumetric strain. Moreover, equations of the associated flow rule of plasticity are incorporated into the model to describe an inelastic volumetric expansion of the freezing soil induced by pore ice pressure. The ability of the model to capture essential features of the freezing process of water-saturated soils is demonstrated by numerical simulation of two laboratory tests. For the first test, a comparison between results of the numerical simulation and experimental measurements of variations of temperature and uplift of the top surface of silty clay specimens with time has been conducted. It has been shown that the numerical results are highly consistent with the measurements when the soil specimen is frozen with the growth of a massive cryogenic structure. In the numerical simulation of the second test, the calculated radial deformation of freezing soil is in good agreement with the experimental measurements, obtained by a fiber-optical sensor during the radial freezing of the quartz sand sample in a closed system.

Statistical results of the numerical model of sea ice drift extremes in the south-western part of the Kara Sea

The aim of the study was to identify the basic characteristics of ice drift in the south-western Kara Sea and to estimate the extreme drift speed of given probability, including its spatial variability and statistical correlation with the main drift-forming factors. In order to obtain the ice drift data, the numerical dynamic-thermodynamic model of ice cover evolution developed in AARI was used. Its basic specific feature is imitation of ice cover with the help of so-called markers (conventional ice floes). Using three variants of the model grid net (25, 12.5 and 5 km), the ice conditions in the Baidara Bay and the adjoining area in January-March 2018 were simulated. The analysis of the simulation results showed that the average ice drift (average ice transport) is directed from the Baidara Bay to the open sea, i.e. northward with slight deviations mostly to the west. A less detailed grid net results in a smoothed ice drift field, while an increase in the spatial resolution of the model increases the spatial contrasts of the ice drift. The maximum values of the extreme ice drift velocity expressed as “once per N years” occur in the northern part of the model area at the directions of the north-western quarter (up to 1.5-1.8 m/s “once per 10 years” - “once per 100 years”, respectively). The frequency of ice drift velocity exceeding 0.3 m/s is about 4-7 %, and that of ice drift velocity exceeding 0.6 m/s is not more than 1 %. At low drift velocity, the role of inertia is very high, but as the drift rate grows, the inertia contribution decreases noticeably. At increasing drift velocity, the statistical correlation between the ice drift (on the one hand) and the wind, current and sea level tilt (on the other hand) becomes evident. This effect is especially evident for the correlation “drift / wind”. The correlation “drift / ice pressure” depends on the drift speed more or less noticeably at low and high drift speeds, when unidirectional changes of the ice drift and ice pressure happen more often than the opposite ones. At the drift velocities within 0.15-0.60 m\s, the correlation between the ice drift and ice pressure is insignificant, i.e. the unidirectional and opposite changes of the ice drift and ice pressure are almost equally likely.

A thermal–hydromechanical coupled model for poro-viscoplastic saturated freezing soil

Most existing thermal–hydromechanical (THM) models used to describe the process of frost heave assumed the freezing soil to be elastic. However, an inelastic constitutive model capable of reflecting the viscous constitutive behaviour of freezing soils should be considered. Based on the existing mathematical model, this study presented an improved mathematical model of coupled water, heat, and stress for saturated freezing soil, in which the soil was assumed to be elastic-viscoplastic and its viscoplasticity was modelled by means of a simple (linear) Norton–Hoff’s law. In addition, solid–fluid interface energy was considered to formulate the effective water and ice pressures and liquid–crystal equilibrium condition which can be used to explain the micro-cryosuction mechanism was adopted to replace Clapyron equation which were used in most existing models. To solve the nonlinear governing equations, numerical simulations were performed using COMSOL software. Finally, the improved model was validated by comparing its simulation results with reference model and the distribution curves of frost heave, temperature, water content and flux rate were discussed.

Static Ice Pressure Measuring System Based on Fiber Loop Ring-Down Spectroscopy and FPGA.

Hydraulic engineering built in the cold region, such as reservoirs and hydropower stations, is often threatened by static ice pressure from nature. Therefore, it is of vital significance to research the pressure variation in the growth and melting processes of the ice layer for the design and protection of hydraulic structures in cold regions. This paper introduces an optical fiber sensor system based on the fiber loop ring-down spectroscopy technology and field-programmable gate array (FPGA) pulse modulation technology. An electro-optic modulation scheme that relied on FPGA to generate optical pulses with adjustable pulse width and period is proposed, which is more suitable for the in-situ observation. In addition, the temperature stability and repeatability of the system are also discussed. This system was applied to the real-time detection of static ice pressure on the sidewall and bottom of the polyvinyl chloride (PVC) pipe during the ice growth and melting processes. The results indicate that the system has favorable stability and sensitivity, and the relationship obtained between the static ice pressure and temperature could provide some references for the field application in the future.

Toward a method for downscaling sea ice pressure for navigation purposes

Abstract. Sea ice pressure poses great risk for navigation; it can lead to ship besetting and damages. Contemporary large-scale sea ice forecasting systems can predict the evolution of sea ice pressure. There is, however, a mismatch between the spatial resolution of these systems (a few kilometres) and the typical dimensions of ships (a few tens of metres) navigating in ice-covered regions. In this paper, the downscaling of sea ice pressure from the kilometre-scale to scales relevant for ships is investigated by conducting high-resolution idealized numerical experiments with a viscous-plastic sea ice model. Results show that sub-grid-scale pressure values can be significantly larger than the large-scale pressure (up to ∼ 4 times larger in our numerical experiments). High pressure at the sub-grid scale is associated with the presence of defects (e.g. a lead). Numerical experiments show significant stress concentration on both sides of a ship beset in sea ice, especially at the back. The magnitude of the stress concentration increases with the length of the lead (or channel) behind the ship and decreases as sea ice consolidates by either thermodynamical growth or mechanical closing. These results also highlight the difficulty of forecasting, for navigation applications, the small-scale distribution of pressure, and especially the largest values as the important parameters (i.e. the length of the lead behind the ship and the thickness of the refrozen ice) are not well constrained.

Moulin Volumes Regulate Subglacial Water Pressure on the Greenland Ice Sheet

AbstractMeltwater inputs to moulins regulate Greenland Ice Sheet sliding speeds by controlling water pressure in the most connected regions of the subglacial drainage system. While moulin storage capacities are a critical control on subglacial water pressure, few observations exist to constrain storage. Using direct observations inside moulins, we show that moulin cross‐sectional areas can be at least 500 m2, far greater than is observed at the surface or assumed in models. Moulin water level measurements and numerical modeling reveal that diurnal variability in moulin water pressure is highly attenuated in moulins with large storage volumes (∼3% ice pressure), relative to moulins with smaller storage volumes (∼25% ice pressure). Because large variability in moulin water pressure is linked to processes that ultimately reduce ice sliding speeds, ice sliding speeds in areas drained by large moulins may be more sensitive to long‐term increases in meltwater than areas drained by small moulins.

Controls on Subglacial Rock Friction: Experiments With Debris in Temperate Ice

AbstractGlacier sliding has major environmental consequences, but friction caused by debris in the basal ice of glaciers is seldom considered in sliding models. To include such friction, divergent hypotheses for clast‐bed contact forces require testing. In experiments we rotate an ice ring (outside diameter = 0.9 m), with and without isolated till clasts, over a smooth rock bed. Ice is kept at its pressure‐melting temperature, and meltwater drains along a film at the bed to atmospheric pressure at its edges. The ice pressure or bed‐normal component of ice velocity is controlled, while bed shear stress is measured. Results with debris‐free ice indicate friction coefficients < 0.01. Shear stresses caused by clasts in ice are independent of ice pressure. This independence indicates that with increases in ice pressure the water pressure in cavities observed beneath clasts increases commensurately to allow drainage of cavities into the melt film, leaving clast‐bed contact forces unaffected. Shear stresses, instead, are proportional to bed‐normal ice velocity. Cavities and the absence of regelation ice indicate that, unlike model formulations, regelation past clasts does not control contact forces. Alternatively, heat from the bed melts ice above clasts, creating pressure gradients in adjacent meltwater films that cause contact forces to depend on bed‐normal ice velocity. This model can account for observations if rock friction predicated on Hertzian clast‐bed contacts is assumed. Including debris‐bed friction in glacier sliding models will require coupling the ice velocity field near the bed to contact forces rather than imposing a pressure‐based friction rule.

Local pressures for ships in ice: Probabilistic analysis of full-scale line-load data

Ships operating in ice might be exposed to significant ice loading. Using a probabilistic semi-empirical method known as the event-maximum method, the long-term maximum level of ice loading on a ship can be estimated based on parent distributions of short-term full-scale ice load measurements. The event-maximum method is used to model the relationship between extreme local ice pressures and impact area by estimating parameters corresponding to the inverse slope (α) and intercept (x0) for the line of best fit for the tail of ranked peak pressure data versus the natural logarithm of the Weibull plotting position. These best-fit lines are assumed to follow an exponential distribution and associated α and x0 values are produced for different local design areas. This allows for the determination of α-area curves, which reflects the relationship between ice pressure and the local design area. Previous studies have determined α-area curves for different geographical areas such as the Beaufort Sea and South Bering Sea, representing different ice types including both first-year and multi-year ice. In this study, two separate sets of full-scale ice load measurements having been considered, namely measurements from the Kara Sea and the Barents Sea, as well as measurements from the Antarctic Ocean. Using these two datasets, two new α-area curves have been generated that represent among other operating areas (the Kara Sea and the Barents Sea), operating modes (icebreaker assisted operation) and impact areas (aft shoulder) not covered by other curves. Earlier formulations of the event-maximum method are based on local design areas in which the width and height of areas are defined by the size of instrumented rectangular panel areas (or combinations of those areas) on the bow of the vessel from which the data were collected. In that approach, ice thickness is not directly considered since the height of individual panels is based on the dimensions of instrumented areas and moreover, detailed ice thickness records were not available for those data sets. In the present study, an alternative approach has been developed to extend the event maximum method for use with ship line-load data. In this approach ice pressures are calculated by dividing the ice force measured on frames by the corresponding line-load area (ALL), which is the product of the width (W) that is based on frame spacing and an assumed line-load height (H) corresponding to 30% of the maximum prevailing ice thickness, as per best design practice, along the lines of the Finnish-Swedish ice class rules. Data already presented as line-loads (in units of force per unit width), are converted to pressures by dividing line-loads by height H. The event definition used in the present approach is defined as the maximum pressure corresponding to 10- or 20-min intervals, as opposed to the impact event definition used in earlier works. In applying this extended method to develop new α-area curves, valuable insights into the relationship between local peak ice pressure and prevailing ice thickness have been gained for the above-mentioned full-scale measurements. The determined curves indicate a negative correlation between prevailing ice thickness and maximum local nominal ice pressure. Finally, it has been demonstrated that it is feasible to apply such curves in combination with the principle of the event-maximum method to estimate the maximum nominal ice pressure expected for a ship given a specified transit distance in sea ice with different prevailing thicknesses.

Penetration and relaxation behavior of JSC-1A lunar regolith simulant under cryogenic conditions

Lunar in situ resource utilization discussions have recently been focused on the presence and distribution of ice in the upper layers of surface regolith, in particular within the confines of the permanently shadowed regions. Extraction ideas - ranging from simple scooping to percussive drilling and thermal (optical) mining utilizing cold-trap volatile capture – require detailed knowledge of the mechanical properties of icy regolith as we are likely to encounter. Penetrometers provide a robust and straightforward measurement technique for determining soil properties, but previous research fails to reliably show measurement sensitivity to increasing ice content due to difficulties in experimentation at cryogenic conditions. To display the capability of a simple conical penetrometer to discern saturation levels of icy regolith simulant within an expected range, we conducted laboratory penetration and subsequent relaxation measurements of JSC-1A lunar simulant using a specially-designed cryogenic apparatus which minimizes sample temperature fluctuation as well as the thermal mismatch between the penetrating probe and tested sample. We measured penetration resistance and force relaxation behavior for JSC-1A lunar simulant under constant displacement rate penetration at ~300 mTorr pressure, ~110 K sample temperature, 170 K to 190 K probe temperature, and ice contents of 0% to 12% and 100%. Penetration resistance and relaxation behavior both showed sensitivity to ice content, with parameters of best-fit curve models offering simple empirical predictors of saturation. A critical ice content of 1% to 3%, wherein a significant increase in penetration resistance occurs, is identified as being fundamentally influenced by the filling of substantial pore space with grouting ice. A decrease in viscoelastic behavior of high ice content samples at cryogenic temperatures is noted, and inhibition of relaxation mechanisms due to activation-energy-based temperature effects is also demonstrated in dry, ice-free simulant. Additional research across the spectrum of ice saturations, temperatures, and pressure environments likely to be found in extraterrestrial environments is suggested to improve upon these results, in particular using cryogenic systems even more specialized to reduce thermal issues and increase load capacities and apparatus stiffness. Such additional information will serve to advance the potential use of these results and this technology in future exploratory missions.

Investigations on the ship-ice impact: Part 1. Experimental methodologies

In the structural design of the Polar Class ships, glancing impact with ice has been considered as the governing load scenario for dimensioning the bow structure. At present, non-linear transient dynamic analysis has been reckoned as a fundamental requirement in the assessment of the structural strength of ships with higher ice classes. Under such requirement, understanding of the dynamic characteristics of the ship-ice impact load appears significant importance. The present study aims to investigate the spatial and temporal variations of the impact loads by simulating the glancing impact events between a polar research vessel and giant ice floes in ice tank. The ship-ice impact loads were recorded by a grid-based tactile sensor attached on the bow area of the model ship. To achieve a reasonable simulation on the design scenario described by the IACS Unified Requirements for Polar Class Ships (UR I), a series of methodological calibration tests were preliminarily carried out to determine the key parameters that should be carefully monitored and controlled, accompanying with thorough discussions on the ship-ice impact process. This paper provides detailed information on the preliminary methodological calibrations and the tactile data processing techniques, including the identification of the ship-ice contact area, the depiction of the ice loading trail and the outline of the spatial distributions of local ice pressures. A companion paper provides detailed analyses and discussions regarding the spatial and temporal variation of the ice impact loads from the formal tests based on the proposed testing procedures obtained by the methodological calibrations.

Methodology for Calculating the Stability of the Polymer Operating String in Permafrost

The goal of this paper is to develop a methodology for calculating the stability of an annular cross-section string casing made of polymer material used for the development of mineral deposits by underground leaching in permafrost formations. The aim was to determine the geometric parameters of the casing and to ensure its operational reliability.The relevance of the research is associated with the peculiarities of external influences on the string, for example, a geotechnological well operating in permafrost formation under conditions of additional exposure to ice pressure during freezing of water in the borehole annulus. This effect is usually accompanied by deformation of the casing due to ice pressure, which can lead to string collapse, abnormal operation and the risk of contamination of the geological environment.The proposed calculation method for a polymer casing is based on simulation of objects using the finite element method. We used the spatial finite elements to model the interaction of key elements of the geotechnological natural-technogenic complex: a polymer casing, ice in the annulus space and homogeneous or heterogeneous rock masses adjacent to the well.The results of the study are presented in the form of tables and patterns of displacements, which reflect stresses and strains in the elements of the calculation scheme. The analysis of the obtained results confirms the possibility of using polymer casings of different technological purposes in various conditions of permafrost formation, including extreme ones. The results of the redistribution of pressure created by ice during the freezing of water in the borehole annulus to the rock mass and the string are evaluated. Interdependent deformations of the rock mass and operating string during freezing of water in the borehole annulus are determined. The necessity of considering the properties of the rock mass in determining the pressure on the string is established. The conditions for the collapse of the string with a different combination of its parameters are revealed.

The ice extrusion test: a novel test setup for the investigation of ice-structure interaction – results and validation

ABSTRACT Understanding ice-structure interaction is critical for an efficient and safe design of offshore structures and ships in ice-covered waters. During the last decades a variety of field experiments, full-scale measurements on ships and laboratory tests have been conducted. Within this paper, a novel experimental setup of the ice extrusion test for the investigation crushing loads is proposed. Due to the flexible design of the experiment brittle and ductile ice loads can be investigated in the laboratory at different load levels. A comprehensive test series with more than 350 tests has been carried out to investigate the system behaviour. The failure mode of the ice is mostly determined by the test speed. The ratio of gap height and sample diameter is the most important parameter for the load level. A validation against full-scale data showed that with this experimental setup it is possible to generate relevant nominal local ice pressures.