Ice Pressure Research Articles

Study on the Factors Influencing the Amplitude of Local Ice Pressure on Vertical Structures Based on Model Tests

Study on the Factors Influencing the Amplitude of Local Ice Pressure on Vertical Structures Based on Model Tests

Thermal-mechanical modelling on cumulative freeze-thaw deformation of porous rock in elastoplastic state based on Drucker-Prager criterion considering dilatancy

The comprehensive understanding of freeze-thaw (F-T) deterioration and deformation properties of rock is a critical basis for frost damage prevention on cold regional rock engineering. In freezing process, plastic strain generates in rock when the stress induced by pore ice pressure (PIP) becomes higher than yield strength, and unrecoverable deformation accumulates in rock under multiple F-T cycles. Therefore, this study presents a thermal-mechanical modelling on cumulative F-T deformation of rock under cyclic F-T action. In the modelling of mechanical action, the microporomechanics theory is applied with a spherical element model in the derivation of equilibrium equations of rock, and the Drucker-Prager criterion is utilized with dilatancy effect of rock considered to describe unrecoverable plastic deformation cumulated in rock under multiple F-T cycles. The thermal process is modelled with unfrozen water content and latent heat accounted. The proposed thermal-mechanical modelling method is validated based on experiments and numerical simulations of F-T deformation of sandstone, and it is able to simulate the temperature and F-T deformation of rock in acceptable precision. The numerical distributions of temperature, PIP, maximum principal strain and displacement are exhibited and show that the plastic region begins to develop in rock matrix with PIP exceeding the elastoplastic critical pressure when temperature drops to about −2 °C and grows rapidly when temperature drops from −2 to −6 °C. Several F-T cycles later, large unrecoverable plastic strain remains in sandstone though PIP dissipates after thawing. The cumulative F-T deformation, porosity increment and maximum of plastic volume ratio are much greater under condition with freezing temperature of −20 °C, compared with condition −10 °C. Besides, as cycle number increases, the plastic volume ratio becomes smaller and its decrease rate attenuates.

Experimental Investigation of Ice Loads on Structures during Quasi-Static Compression Tests

In polar ship hull structural designs, methods based on regulations are considered the most authoritative; however, they tend to be conservative and often exhibit a notable degree of redundancy. This study aims to evaluate the applicability of the empirical formula for ice load assessments by conducting a series of quasi-static indentation tests on scaled hull plates under laboratory-made ice blocks of different scales. The obtained data include ice loads, structural responses, and characteristics of ice pressure distribution. A detailed comparison of various formulas is provided, along with an examination of their differences and errors in comparison to experimental results. The objective of this paper is to offer technical support for ice load forecasting and assessment.

Efficacy of different strategies for reducing labor pain: A Bayesian analysis.

The effectiveness of different medical interventions in managing labor pain has yielded mixed results. Therefore, this systematic review and network meta-analysis aimed to provide a comprehensive summary of the available evidence on the impact of different strategies for reducing labor pain. We systematically searched 3 English databases (Pubmed, Embase and the Cochrane Library) from inception to January 2023. Randomized controlled trials (RCTs) or controlled clinical trials that investigating the effects of different strategies for reducing labor pain were included in this network meta-analysis. Risk of bias (ROB) was assessed using the Cochrane ROB tools. Network meta-analysis was performed using the R software (version 4.2.1) with gemtc package. A total of 9 studies involving 823 patients, including 9 treatments (acupressure, birth ball exercise, Bonapace method, distraction techniques, ice pressure, LI4 acupressure, lidocaine spray, smartphone-based music intervention and placebo). The surface under the cumulative ranking (SUCRA) shows that Bonapace method ranked first (SUCRA, 79.5%), LI4 acupressure ranked second (SUCRA, 65.6%), distraction technique ranked third (SUCRA, 57.6%), birth ball exercise ranked fourth (SUCRA, 51.8%). According to the results of the network meta-analysis, among the different strategies examined, the Bonapace Method stands out as the most effective nonpharmacological intervention for reducing labor pain. The results of this meta-analysis can aid both patients and healthcare professionals in choosing the most effective techniques to reduce labor pain.

Finite element modeling of thermal‐hydro‐mechanical coupled processes in unsaturated freezing soils considering air‐water capillary pressure and cryosuction

AbstractThis paper presents a comprehensive computational model for analyzing thermo‐hydro‐mechanical coupled processes in unsaturated porous media under frost actions. The model employs the finite element method to simulate multiphase fluid flows, heat transfer, phase change, and deformation behaviors. A new soil freezing characteristic curve model is proposed to consider the suctions from air‐water capillary pressure and water‐ice cryosuction. A total pore pressure with components from liquid water pressure, air pressure, and ice pressure is used in the effective stress law. Vapor and dry air are considered miscible gases, utilizing the ideal gas law and Dalton's law. The governing equations encompass the linear momentum balance equation, the energy balance equation, and mass conservation equations for water species (ice, liquid, and vapor) and dry air. Weak forms are formulated based on primary variables of displacement, water pressure, air pressure, and temperature. The spatial discretization is achieved through the finite element method, while temporal discretization employs the fully implicit finite difference method, resulting in a system of fully coupled nonlinear equations. To verify the proposed computational model, a numerical implementation is developed and validated against a set of experimental data from the literature. The successful verification demonstrates the robustness of the model. A detailed discussion of the contributions from phase change strain and different sources of pore pressure is also addressed.

Numerical investigation of the path-dependent frost heave process in frozen rock under different freezing conditions

Frost heave in water-bearing rock masses poses significant threats to geotechnical engineering. This paper developed a novel three-dimensional (3D) frost model, based on the combined finite-discrete element method (FDEM), to investigate the frost heave process in rock masses where thermal transfer, water migration, water-ice phase transition (ice growth) and ice-rock interaction are explicitly simulated. The proposed model is first validated against existing experimental and analytical solutions, and further applied to investigate path-dependent frost heave behavior under various freezing conditions. Results show that freezing direction plays a vital role in the dynamic ice growth and ice-rock interaction, thus affecting the frost heave behavior. In the top-down freezing regime, ice plugs form first at the crack's top surface, sealing the crack and preventing water migration, which can amplify ice pressure. Parametric studies, including rock Young's modulus, ice-rock friction, and rock hydraulic conductivity, further reveal that the temporal aspects of ice development and rock mechanical response strongly affect ice-rock interaction and hence the frost heave mechanism. Furthermore, some typical phenomena (e.g. water/ice extrusion and frost cracking) can also be well captured in this model. This novel numerical framework sheds new light on frost heave behavior and enriches our understanding of frost heave mechanisms and ice-rock interaction processes within cold environment engineering projects.

A Framework for Structural Analysis of Icebreakers during Ramming of First-Year Ice Ridges

This paper presents a framework for structural analysis of icebreakers during ramming of first-year ice ridges. The framework links the ice-ridge load and the structural analysis based on the physical characteristics of ship–ice-ridge interactions. A ship–ice-ridge interaction study was conducted to demonstrate the feasibility of the proposed framework. A PC-2 icebreaker was chosen for the ship–ice interaction study, and the geometrical and physical properties of the ice ridge were determined based on empirical data. The ice ridge was modeled by solid elements equipped with the continuous surface cap model (CSCM). To validate the approach, the simulated ice resistance was computed using the Lindqvist solution and in situ tests of R/V Xuelong 2. First, the local ice-induced pressure on the hull shell was determined based on numerical simulations. Subsequently, the local ice pressure was applied to local deformable sub-structural models of the PC-2 icebreaker hull by means of triangular impulse loads. Finally, the structural response of sub-structural models with refined meshes was computed. This case study demonstrates that the proposed framework is suitable for structural analysis of ice-induced stresses in local hull components. The results show that the ice load and the structural response obtained based on the four first-year ice-ridge models show obvious differences. Furthermore, the ice load and corresponding structural response increases with the width of the ridge and with increasing ship speed.

Некоторые оценки тяжелых ледовых условий (сжатий) в Печорском море по данным наблюдений и моделирования (моделирование и анализ)

The work continues the study focused on the analysis of the severe ice conditions’ formation in the Pechora Sea during navigation in 2003 and 2018 (published in vol.12, no.4, 2022). Using a numerical model, the authors reproduce the dynamics and some elements of the morphometry of the ice cover during the indicated ice seasons. Thus, they reveal that the significant ice pressure (100—150 kPa and more) is caused by the strong on-shore wind, while the ice pressure related to the tidal phenomena have the predominant value at the weak winds. The tidal ice pressure occurs permanently and regularly, and varies mainly within the range of 10—50 kPa. The contribution of ice hummocks to the total ice volume becomes significant when strong ice pressure happens at the background of high ice thickness (close to the seasonal maximum, i.e. more than 60—70 cm). With small ice thicknesses, even strong ice pressure, as a rule, does not lead to a significant increase in the equivalent thickness of hummocks.

A poromechanics-based macro-mesoscopic constitutive model for warm frozen soil

This paper presents the establishment of a macro-mesoscopic constitutive model based on poromechanics for investigating the mechanics of warm frozen soil. The elastic parameters of warm frozen soil are influenced by the ice content variations during the loading process, considering the pressure melting characteristic of warm frozen soil. Through the integration of poromechanics and mesomechanics, a macro-mesoscopic constitutive model incorporating the pressure melting effect is developed to characterize the mechanical properties of warm frozen soil. The proposed model establishes a relationship between the elastic modulus at the mesoscopic and macroscopic scales of warm frozen soil.To validate the model, a comparison is made between the model predictions and experimental data obtained from warm frozen silt. The results demonstrate that the model effectively captures significant mechanical performance of warm frozen soil, including strain soft and dilatancy phenomena under various confining pressure conditions. Furthermore, the proposed model enables the prediction of freezing temperature, unfrozen water saturation, unfrozen water pressure, ice pressure, and porosity changes in warm frozen silt samples during the loading process.

An agent-based modelling framework for performance assessment of search and rescue operations in the Barents Sea

In recent years, the increase in Arctic offshore activities has raised concerns about the search and rescue (SAR) operations as mitigative measures to ensure the safety of shipping and cruise activities. Performing SAR operations in the remote Arctic offshore environment is exceptionally challenging due to the severe environmental conditions, including low temperatures, high waves, strong winds, heavy snow showers, sea ice, spray icing, dense fog, limited visibility, and polar low pressures. Moreover, the scarcity of port infrastructure along the Arctic coastline exacerbates the difficulties faced during SAR operations. Tackling the aforementioned challenges necessitates a comprehensive modelling framework for analysis of SAR operations in the Arctic that is able to consider the dynamics and uncertain nature of Arctic harsh environmental conditions, and the constraints imposed by the limited capacity of Arctic SAR infrastructure. To this aim, this paper proposes an agent-based modelling (ABM) framework to assess the performance of SAR operations while tackling such challenges in the Arctic. A Monte Carlo simulation approach is used to model the dynamics and uncertainty of weather and sea conditions using historical data, using which some severity levels are determined. Expert judgement process is then used quantify the impacts of such severity levels on the performance of rescue agents, and thus, on the total rescue time. To validate the proposed framework, an illustrative case in the Norwegian Barents Sea is considered, where the performance of SAR infrastructure is examined under different rescue scenarios. According to the results of this paper, the total rescue time is the longest during December to February, and the shortest rescue time is associated with months May to August. Some recommendations are further proposed to improve the performance of SAR infrastructure in the Barents Sea.

A coupled thermomechanical peridynamic correspondence model for damage prediction in a freezing rock

This study presents a coupled thermomechanical (TM) bond-associated non-ordinary state-based peridynamic (BA-NOSB PD) (correspondence) model for simulating the thermal behavior and crack propagation in a saturated rock due to freeze. Considering the change in thermal property and the latent water–ice phase transition at low-temperature conditions, the PD form of the nonlinear thermal conduction equation is derived by using the PD differential operator (PDDO). The deformation response is obtained in the framework of BA-NOSB PD model considering the pore ice pressure and thermal expansion. The accuracy of the TM BA-NOSB PD model is verified by simulating the thermal behavior of tuff and sandstone and crack propagation in specimens with pre-existing cracks at low-temperature conditions. The PD predictions of temperature and frost heaving strain are in close agreement with the experimental and previous numerical results. The present model also accurately predicts crack propagation and coalescence in saturated rocks due to the freezing frost.

Frost-heaving characteristics and formation mechanism of saturated sandstone under unidirectional freezing conditions

In this study, a series of frost-heaving experiments were conducted on saturated sandstone at varying cooling rates under unidirectional freezing conditions. The frost-heaving strain in the freezing process was examined using a novel laboratory testing methodology. The results showed that the frost-heaving behavior of the saturated sandstone was significantly affected by the freezing direction and rate. Specifically, the rapid freezing of sandstone parallel to the freezing direction resulted in a more pronounced frost-heaving strain than that perpendicular to the freezing direction. The rock freezing rate had a positive correlation with the peak frost-heaving strain parallel to the freezing direction, and a negative correlation with that perpendicular to the freezing direction. A microstructure-based conceptual model is proposed to determine the frost-heaving pressure. The conceptual model showed that the ice pressure, determined by the pore-water pressure and capillary force, resulted from the crystallization of the pore water within the pore structure. A nonlinear relationship was observed between the ice pressure and crystallization rate. Capillary forces were more significant for slow crystallization processes, resulting in a larger difference between ice and water pressures. At high crystallization rates, the hydraulic pressure acted on the pore structure before the capillary forces become significant, leading to a smaller difference between the water and ice pressures. Rapid crystallization processes resulted in the uneven distribution of ice pressure within the pore structure, with subsequent re-equilibration occurring with the migration of unfrozen water. The proposed conceptual model presents a new perspective for obtaining an improved understanding of the microscopic frost-heaving mechanism involved in the freeze-thaw damage of porous rocks. It provides an evaluation method for the behavior of rocks during weathering by frost heave in cold regions.

Understanding unsaturated sulfate saline soil in cold regions: A comprehensive hydraulic–thermal–air–salt–mechanical model with experimental research

The destruction of infrastructure built on saline soil in cold regions is closely related to water and salt migration, and soil deformation in foundations. Consequently, it is imperative to understand the mechanisms of heat and mass transfer, along with deformation in saline soil. Based on the unsaturated soil mechanics and porous media theory, a hydraulic–thermal–air–salt–mechanical (HTASM) coupled mathematical model for frozen unsaturated sulfate saline soil is proposed. The model incorporates the impact of ice-water phase change, sodium sulfate crystallization, and vapor flow on heat and mass transfer during the freezing process. Two parameters—salt crystallization pressure, and ice pressure—are introduced into the mechanical control equation to capture the effects of phase change on deformation. In addition, the relationship between the density of soil particles, water, ice and gas, and temperature and pressure is considered to reflect the dynamic change of density during freezing. Finally, the numerical simulation using the HTASM model is conducted and its efficacy is validated by comparing the numerical results with those obtained from indoor unidirectional freezing tests. The coupling effect of the HTASM model is revealed by analyzing the dynamic changes of temperature, water content, salt content, vapor flux and crystallization pressure in the soil column during freezing. The results show that the proposed HTASM model can well simulate the heat and mass transfer behavior in freezing unsaturated sulfate saline soil.

Influences Driving and Limiting the Efficacy of Ice Segregation in Alpine Rocks

AbstractRockwall erosion by rockfall is largely controlled by frost weathering in high alpine environments. As alpine rock types are characterized by crack‐dominated porosity and high rock strength, frost cracking observations from low strength and grain supported pore‐space rocks cannot be transferred. Here, we conducted laboratory experiments on Wetterstein limestone samples with different initial crack density and saturation to test their influence on frost cracking efficacy. We exposed rocks to real‐rockwall freezing conditions and monitored acoustic emissions as a proxy for cracking. To differentiate triggers of observed cracking, we modeled ice pressure and thermal stresses. Our results show initial full saturation is not a singular prerequisite for frost cracking. We also observe higher cracking rates in less‐fractured rock. Finally, we find that the temperature threshold for frost cracking in alpine rocks falls below −7°C. Thus, colder, north‐exposed rock faces in the Alps likely experience more frost cracking than southern‐facing counterparts.

A model of segregation frost heave for saturated soil freezing under overburden pressure

To study the inhibition mechanism of overburden pressure on water migration in freezing soil, the pressure-suction coexistence state of film water is analyzed, and it is found that the main function of ice pressure is to offset and balance the theoretical suction. Under the combined action of ice pressure and theoretical suction, the surface adsorption force that drives water migration is produced. Based on this, the mechanical model of the pressure-suction coexistence state is introduced into the frozen fringe theory, and it is found that as the overburden pressure increases, the surface adsorption force gradually increases, while the total permeability coefficient of the frozen fringe decreases according to a high-order power function. Given this, a theoretical model of segregation frost heave under pressure is established and an explicit equation for the water migration velocity is given. Finally, a frost heave loading test is performed on saturated silt under open-system conditions, and the main parameters of the test process are substituted into the explicit equation for water migration velocity, the results showed that the calculated value of the model is completely consistent with the experimental value, thus verifying the correctness of the model. In summary, the proposed model has important theoretical value and practical significance for improving the existing frost heave theory.

Influence of propeller on brash ice loads and pressure fluctuation for a reversing polar ship

When a polar ship is stuck in ice-covered waters, reversing operation is an effective way for it to escape from ice. During this operation, rotational propeller will affect flow field and motion of brash ice, thus affecting ice loads and pressure fluctuation. In this paper, a new coupling model using Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) is proposed to investigate characteristics of brash ice loads and pressure fluctuation for a polar ship reversing in a brash ice channel. The present method is well validated by model tests of a towing polar ship in brash ice channel. The simulation results show that in reversing process, brash ice blocks collide with the stern and two sides of ship, where ice blocks accumulate. When the reversing speed is low, the pumping action and acceleration effect of the propeller on the brash ice are obvious. The pumping action reduces the average value of the longitudinal and vertical ice loads, and the acceleration effect makes ice loads occur multiple peaks. The increase in reversing speed worsens the performance of propeller, weakening the pumping action and acceleration effect. The pressure fluctuation period is consistent with propeller rotation period, which decreases for poor propeller propulsion caused by higher reversing speed. It is necessary to strengthen the stern structure in reversing process, especially at low speed, for pumping action and acceleration effect of propeller.

Diffuse debris entrainment in glacier, lab and model environments

AbstractSmall quantities of liquid water lining triple junctions in polycrystalline glacier ice form connected vein networks that enable material exchange with underlying basal environments. Diffuse debris concentrations commonly observed in ice marginal regions might be attributed to this mechanism. Following recent cryogenic ring-shear experiments, we observed emplacement along grain boundaries of loess particles several tens of microns in size. Here, we describe an idealized model of vein liquid flow to elucidate conditions favoring such particle transport. Gradients in liquid potential drive flow toward colder temperatures and lower solute concentrations, while deviations of the ice stress state from hydrostatic balance produce additional suction toward anomalously low ice pressures. Our model predicts particle entrainment following both modest warming along the basal interface resulting from anticipated natural changes in effective stress, and the interior relaxation of temperature and solute concentration imposed by our experimental protocols. Comparisons with experimental observations are encouraging, but suggest that liquid flow rates are somewhat higher and/or more effective at dragging larger particles than predicted by our idealized model with nominal parameter choices. Diffuse debris entrainment extending several meters above the glacier bed likely requires a more sophisticated treatment that incorporates effects of ice deformation or other processes.

Field Observations of Water and Ice Problems in Railway Tunnels from a Maintenance Perspective

Abstract During the winter season, ice causes major problems in many Swedish railway tunnels. Ice, rock and shotcrete in the roof and on the walls may come loose and fall down, installations and cables can break due to ice loads and the tracks can become covered with ice. To maintain safety and prevent traffic disturbances, many tunnels require frequent maintenance. The removal of ice, loose rock and shotcrete is expensive and potentially risky work for the maintenance workers. To reduce maintenance costs, it is important to improve our knowledge of frost penetration inside tunnels and investigate the effect of ice pressure and frost shattering on load-bearing constructions. The aim of this investigation was to gather information about the problems caused by water leakage and its effect on the degradation of a rock tunnel when subjected to freezing temperatures. There are many factors that determine whether frost or ice formations will appear in tunnels. To collect information on ice formation problems, field observations were undertaken in five of Sweden’s railway tunnels between autumn 2004 and summer 2005. For one of the tunnels, follow-up observations also took place in March during the years 2005, 2006 and 2007. Keywords: Railway tunnel, Field observations, Ice formation, Frost shattering, Maintenance, Degradation of rock and shotcrete, Cold climate.

Ice pressure distribution model: A geometry-based solution for high-pressure zone representation

Studies have shown that the interface between ice and an indenter is a complex system that gives rise to two ice types, relatively-intact ice and crushed ice. Each type accordingly imparts different pressure magnitudes on the indenting structure, where intact ice is associated with high pressures zones (HPZs) and crushed ice with low pressures (LPZs). HPZ average pressures are almost an order of magnitude larger than LPZ pressures. This means that their relative distribution over the contact area significantly affects the structural response. This work develops a methodology for modelling ice pressure zone distributions based on the topological skeleton and distance field information of the ice-indenter contact area. Results compare favourably with experimentally determined HPZ distributions from varying ice indentation experiments of small, medium and large scale.

Study on the Influence of Saturation on Freeze–Thaw Damage Characteristics of Sandstone

In order to explore the evolution mechanism of freeze-thaw disasters and the role of water in the freezing-thawing cycles of rocks, the macro mechanical indexes and microstructural characteristics of seven different saturation sandstones after certain freeze-thaw cycles were analyzed. Electron microscope scanning, nuclear magnetic resonance, and uniaxial compression tests were employed to study the migration law of water in the rock, the crack growth law, and the damage mechanism during freeze-thaw cycles. The results showed that when the saturation was 85%, the peak load curve of sandstone with different saturation appeared at the minimum point, and the porosity of sandstone reached the maximum. The damage variable increased sharply when the saturation was 75-85%. This proves that 85% saturation is the critical value of sandstone after five freeze-thaw cycles. The water migration freezing model is established, and the migration direction of capillary film water during freezing is micropore → mesopore → macropore. The migration of water is accompanied by the expansion and generation of cracks. Then we study the mechanism and law of crack expansion, and the crack propagation rate is positively related to the theoretical suction. The theoretical suction and theoretical ice pressure increased linearly with the decrease in temperature, which accelerated the crack propagation. The crack propagation rate in decreasing order is Vmacropore > Vmesopore > Vmicropore. The research results can provide a theoretical basis for evaluating the stability of rocks under the action of freeze-thaw cycles in cold regions.