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Large-scale shear test of brash ice
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik, Norway.ORCID iD: 0000-0001-7896-3710
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0002-4042-4110
SINTEF Narvik, Norway.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.ORCID iD: 0000-0003-1935-1743
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2022 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 249, article id 110935Article in journal (Refereed) Published
Abstract [en]

A large-scale shear apparatus has been originally developed and built to test the mechanical properties of coarse-grained material. It was used to evaluate the shear behaviour of brash ice. The brash ice blocks were collected at Luleå harbour in two separate measuring campaigns in March 2020 and March 2021. The shear cylinder was loaded with brash ice in Luleå port in two different locations for the two test campaigns, and the displacement-controlled shear tests were conducted. A vertical actuator was used to set a constant normal load and then a horizontal actuator was used to move the shear swing. In this setup, time, forces, and displacements were recorded at the forward and return stroke of the horizontal actuator. In total 6 shear cycles on two brash ice samples with axial stress of 4.8 kPa, 2 kPa and 1 kPa were performed. The test data was analysed to determine the relationship between shear stress and shear strain. The macro-porosity and confining axial force were found to be the most influential factors in determining the strength and deformation of the brash ice. Furthermore, an attempt has been made to estimate a few parameters of a material model known as the Continuous Surface Cap Model.

Place, publisher, year, edition, pages
Elsevier, 2022. Vol. 249, article id 110935
Keywords [en]
Large-scale shear, Brash ice, Volumetric strain, Continuous Surface Cap Model (CSCM)
National Category
Ocean and River Engineering
Research subject
Building Materials; Soil Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-87537DOI: 10.1016/j.oceaneng.2022.110935ISI: 000778736100004Scopus ID: 2-s2.0-85125482502OAI: oai:DiVA.org:ltu-87537DiVA, id: diva2:1603833
Funder
The Research Council of Norway, 195153
Note

Validerad;2022;Nivå 2;2022-03-31 (hanlid);

Funder: KOLARCTIC (1867.50, KO2100 ICEOP); Nordland county; SINTEF

Available from: 2021-10-18 Created: 2021-10-18 Last updated: 2023-05-08Bibliographically approved
In thesis
1. Nonlinear Numerical Simulations of Interactions Between Ice Rubble and Structure
Open this publication in new window or tab >>Nonlinear Numerical Simulations of Interactions Between Ice Rubble and Structure
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This research is focused on three distinct but interconnecting topics:1) investigation of physical and mechanical properties of ice rubble, 2) material modelling of ice rubble, 3) numerical simulation of the interaction between ice rubble structure interaction. large scatter in the values of physical and mechanical properties of ice rubble can be seen in the literature due to non-standardised methods. Therefore, important tests are identified, and their major findings are presented. The shear box and punch through tests are important methods for deriving ice rubble properties, yet the interpretation of the results of the test is not straightforward. Numerical simulation of these tests offers a unique way to gain insight into rubble behaviour and to calibrate a material model for ice rubble. The accurate modelling of the ice rubble is needed when designing marine structures in ice-covered waters.

The friction coefficient between ice-ice, ice-rubber and ice-steel was investigated by measuring contact forces in controlled laboratory experiments. The experiments revealed that surface topology, speed and temperature play important roles in determining the friction coefficient on ice surfaces. Given the similarities between cohesionless ice rubble and brash ice, like discrete nature, these two ice features can be explored together. A large-scale simple shear test and a pull-up test were conducted at Luleå harbour. The data collected over two test campaigns for large scale simple shear was analysed. An attempt was made to estimate, elastic properties (bulk and shear modulus), yield strength, kinematic and volumetric hardening parameters for continuous surface cap model (CSCM) based on large-scale test data.

The calibration of material model CECM was done by curve fitting of simulation data to tests. Three tests were simulated using the finite element method (shear-box test and punch through the test) and smoothed particle hydrodynamics (punch through and pull-up test). The automated optimization algorithms were used to find the admissible combination input parameters. The assumptions of isotropy and continuity of surfaces reduced the number of input parameters. Despite the mesh distortion issue, the simulation of punch through test post-peak behaviour was simulated correctly. In the simulation shear box, expansion due to shear stress in the rubble was observed. In the simulation, the results clearly demonstrated that the evolution of the deformation patterns was related to the load records in the experiments.

A seemingly promising numerical method i.e. smoothed particle hydrodynamics (SPH) was explored in this research. The limitation posed by mesh size in finite element formulation is removed in SPH formulation, yet this formulation takes advantage of the numerically robust underlying Lagrangian formulation. The plug formation in the simulation of punch through test and pull-up test was similar to that of test observations. Good agreement in the initial, peak and post-peak part of the load-displacement relationship was achieved by calibrating the material model parameter. It can be seen clearly while by comparing simulation results, that Mohr-Coulomb criteria are not fit to simulate the post-peak behaviour of ice rubble in the tests.

The Cohesive Element Method (CEM) was used to simulate two full-scale load events recorded at Lighthouse Norströmsgrund in the Gulf of Bothnia. Two load events were identified out of full-scale measurement campaigns, “Measurements of Structure in Ice” (STRICE), to simulate ice rubble stricture interaction process with CEM. a scaling formula, based on ice rubble porosity, is explored to estimate material properties such as elastic modulus, fracture toughness and fracture energy. The hydrodynamic effects of water were added to the numerical model by the spring dash-pot system which was developed during this work for the research on ice mechanics. The frictional forces were also part of the numerical model. A relative velocity based dynamic friction coefficient was introduced. The mass damping and stiffness damping were part of the numerical model for interaction between ice rubble structure interaction but were not fully investigated.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2022. p. 178
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
ice mechanics, ice rubble, sea ice ridges, punch through test, shear box test, friction coefficient, cohesive element method, smoothed particle hydrodynamics, continuous surface cap model, numerical modelling
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-87540 (URN)978-91-7790-979-8 (ISBN)978-91-7790-980-4 (ISBN)
Public defence
2022-03-04, C305, Luleå, 10:00 (English)
Opponent
Supervisors
Funder
The Research Council of Norway, 195153EU, European Research Council, 1867.50
Available from: 2021-11-16 Created: 2021-11-15 Last updated: 2022-12-31Bibliographically approved

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The full text will be freely available from 2031-10-01 11:18
Available from 2031-10-01 11:18

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Patil, AniketZhaka, VasiolaSand, BjörnarLaue, JanCwirzen, Andrzej

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