The chapter describes results of measurements during several ship trials, in which instrumented vessels were used to interact with ice. The main focus is the measurement of local ice pressures by strain-gauging of the ship hull. The results include ramming of ice features. A variety of results are analysed, including those from the Kigoriak, Polar Sea, Louis S. St.-Laurent, Oden, and Terry Fox. Analyses of high-pressure zones are presented and a novel method (the alpha-method) is presented for local design of vessels and structures.

The chapter commences with a description of various observations of time-dependent fractures in ice. In the medium scale tests, slow loading resulted in very large flaws, whereas fast loading resulted in many small fractures and spalls in the vicinity of the load application. Then, a summary of fracture toughness measurements on ice are summarized. The question of stress singularity at crack tips is raised, and to deal with this, Barenblatt’s analysis is introduced, based on linear elasticity. Schapery’s linear viscoelastic solution for this method is described, using the elastic-viscoelastic correspondence principle. The J integral forms the basis of the application to fracture, using the correspondence principle noted. A set of experiments on ice samples, beams with 4-point loading, was conducted. Tests with a range of loading rates, as well as constant-load tests, were conducted. Comparison of the results with theory was made. The results of Liu and Miller using the compact tension set-up were also considered. Good agreement with theory was found in all cases. Nonlinear viscoelastic theory of Schapery is also outlined.

The analysis of ice response to stress using finite elements is described, using multiaxial constitutive relationships, including damage, in a viscoelastic framework. The U-shaped relationship of compliance with pressure is part of this formulation. The results show that the layer of damaged ice adjacent to the indentor arises naturally through the formulation, giving rise to a peak load and subsequent decline. This shows that there can be “layer failure” in addition to failure due to fractures and spalling. Tests on extrusion of crushed ice are described together with a formulation of constitutive relationships based on special triaxial tests of crushed ice. The ice temperature measured during field indentation tests showed a drop in temperature during the upswings in load. This was attributed to localized pressure melting. Small scale indentor tests are described, which show clearly the difference between layer failure and spalling, as found using high-speed video and pressure-sensitive film. The question of scaling, as used in ice tanks, is addressed. Flexural failure can be scaled to some extent; scaling of high-pressure zones lies in the mechanics as developed in the book.

Viscoelastic theory is introduced, using ice as the material under consideration. Linear theory is first introduced, based on elasticity of the springs and on linear viscosity of the dashpots. The nonlinearity of the dashpots in modelling ice deformation is then introduced. The “crushed layer” and analysis by Kheisin and co-workers is outlined, based on linearly viscous modelling. Kelvin and Burgers models are introduced. Microstructural change is modelled using damage mechanics and state variables for material points. Stress and strain re-distribution arises from this aspect, as well as from nonlinearity with stress. Schaperys modified superposition principle is introduced.

Recent observations are summarized, in which it has been found that in compressive ice failure, zones of high-pressure form with pressures locally as high as 70 MPa. Various aspects of ice behaviour are summarized: creep, fracture, recrystallization, and the development of microstructurally modified layers of ice. Pressure melting is described, whereby the melting temperature decreases with accompanying hydrostatic pressure. The importance of fracture and spalling in the development of high-pressure zones is emphasized. The use of mechanics in analysis of ice failure is discussed.

The importance of field experimental results is emphasized, as well as the necessity to include consideration of time in ice mechanics

Measurements of pressure on fixed structures are reviewed including the Helsinki and JOIA test programmes. The Molikpaq experience and the Hans Island programmes are described in some detail. Loads tend to be concentrated in small areas, as was the case for ship structures (the high-pressure zones). Size effect of ice pressure with regard to ice thickness is discussed; average pressures decrease with ice thickness. The medium scale field indentation programmes are described, covering the Pond Inlet, Rae Point, and Hobsons Choice Ice Island test series. Ice-induced vibrations are introduced; these were observed in the Molikpaq structure and in many indentation tests. The vibrations tended to occur at certain speed ranges, associated with ice crushing. Results of field tests on iceberg failure are also reviewed, in which supporting evidence for layer failure was obtained.

The Appendix contains an outline of the development of Biot-Schapery theory based on the thermodynamics of irreversible processes. A brief biography of R. A. Schapery is followed by an exposition of the theory, the use of the modified superposition theory, and the use of J integral to deal with damage processes.

The states of stress in high-pressure zones involve a combinations of volumetric and deviatoric stresses. Modelling of ice behaviour under these states of stress is essential for developing proper mechanics of failure of high-pressure zones. Past triaxial tests are reviewed. There is a lack of information for higher confining pressures. The microstructural changes of microcracking and recrystallization needed to be studied in terms of past stress history. These were addressed in a special series of tests, which showed that microcracking at low confinements causes increase in compliance, which decreases with increasing confinement, but that at higher confinements, pressure softening, associated with melting, results in much increased compliance. Tests in which the activation energy at various confinements was measured using tests at a range of temperatures showed that the addition of pressure to ice resulted in behaviour similar to less confined ice at a higher temperature (pressure–temperature equivalence). Ice is prone to localize and small irregularities are sufficient to trigger this behaviour, as observed in some triaxial tests.

Methods used for sample preparation in the research are described, for triaxial testing and for small-scale indentation in the laboratory.