scholarly journals The mechanical behaviour and failure modes of volcanic rocks: a review

2021 ◽  
Vol 83 (5) ◽  
Author(s):  
Michael J. Heap ◽  
Marie E.S. Violay
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Mechanical Behaviour ◽  
Failure Modes ◽  
Volcanic Rocks ◽  
Pore Collapse ◽  
First Order ◽  
Compaction Bands ◽  
Brittle Ductile Transition ◽  
Porosity And Permeability

AbstractThe microstructure and mineralogy of volcanic rocks is varied and complex, and their mechanical behaviour is similarly varied and complex. This review summarises recent developments in our understanding of the mechanical behaviour and failure modes of volcanic rocks. Compiled data show that, although porosity exerts a first-order influence on the uniaxial compressive strength of volcanic rocks, parameters such as the partitioning of the void space (pores and microcracks), pore and crystal size and shape, and alteration also play a role. The presence of water, strain rate, and temperature can also influence uniaxial compressive strength. We also discuss the merits of micromechanical models in understanding the mechanical behaviour of volcanic rocks (which includes a review of the available fracture toughness data). Compiled data show that the effective pressure required for the onset of hydrostatic inelastic compaction in volcanic rocks decreases as a function of increasing porosity, and represents the pressure required for cataclastic pore collapse. Differences between brittle and ductile mechanical behaviour (stress-strain curves and the evolution of porosity and acoustic emission activity) from triaxial deformation experiments are outlined. Brittle behaviour is typically characterised by shear fracture formation, and an increase in porosity and permeability. Ductile deformation can either be distributed (cataclastic pore collapse) or localised (compaction bands) and is characterised by a decrease in porosity and permeability. The available data show that tuffs deform by delocalised cataclasis and extrusive volcanic rocks develop compaction bands (planes of collapsed pores connected by microcracks). Brittle failure envelopes and compactive yield caps for volcanic rocks are compared, highlighting that porosity exerts a first-order control on the stresses required for the brittle-ductile transition and shear-enhanced compaction. However, these data cannot be explained by porosity alone and other microstructural parameters, such as pore size, must also play a role. Compactive yield caps for tuffs are elliptical, similar to data for sedimentary rocks, but are linear for extrusive volcanic rocks. Linear yield caps are considered to be a result of a high pre-existing microcrack density and/or a heterogeneous distribution of porosity. However, it is still unclear, with the available data, why compaction bands develop in some volcanic rocks but not others, which microstructural attributes influence the stresses required for the brittle-ductile transition and shear-enhanced compaction, and why the compactive yield caps of extrusive volcanic rocks are linear. We also review the Young’s modulus, tensile strength, and frictional properties of volcanic rocks. Finally, we review how laboratory data have and can be used to improve our understanding of volcanic systems and highlight directions for future research. A deep understanding of the mechanical behaviour and failure modes of volcanic rock can help refine and develop tools to routinely monitor the hazards posed by active volcanoes.

scholarly journals The relative strengths of debris-laden basal ice and clean glacier ice: some evidence from Taylor Glacier, Antarctica

1996 ◽  
Vol 23 ◽  
pp. 270-276 ◽  
Author(s):  
Wendy Lawson
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Mechanical Behaviour ◽  
Deformation Mechanism ◽  
Basal Ice ◽  
Basal Zone ◽  
Dominant Deformation Mechanism ◽  
Glacier Ice ◽  
Pressure Melting ◽  
Taylor Glacier

An understanding of the mechanical behaviour of the basal zone of an ice mass is fundamental to understanding the overall dynamics of that ice mass. Despite the fact that debris-laden ice is found in the basal zones of many glaciers and ice sheets, its mechanical behaviour is only poorly understood. This paper attempts to expand our knowledge of the mechanical behaviour of debris-laden ice by examining the uniaxial compressive strength of debris-laden basal ice sampled from the snout of the Taylor Glacier, Antarctica. The mechanical behaviour of debris-laden ice (debris content 5–20% by volume) under uniaxial compression, and the relationship between the behaviours of debris-laden basal ice and ‘clean’ glacier ice, is complex and variable. At the relatively warm temperatures at which uniaxial compressive strength tests were conducted in the field, debris-laden ice was generally weaker than clean glacier ice. At these temperatures, between 0° and −5°C, pressure melting was the dominant deformation mechanism in the debris-laden ice and cracking the dominant deformation mechanism in clean ice. At −25°C, however, debris-laden ice reached higher strengths than lite clean glacier ice and cracking was the dominant deformation mechanism in both ice types. The change in relationship between the strengths of debris-laden and clean ice with temperature is inferred to be attributable to the temperature dependence of the rate of pressure melting. These results suggest that the dynamic effects and significance of the presence of a debris-laden ice layer in the basal zone of an ice mass are likely to be highly variable in space and time.

Large-Scale Ice Strength Tests at Slow Strain Rates

1988 ◽  
Vol 110 (3) ◽  
pp. 302-306 ◽  
Author(s):  
A. C. T. Chen ◽  
J. Lee
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Large Scale ◽  
Failure Modes ◽  
Sheet Thickness ◽  
Crystallographic Structure ◽  
Strain Rates ◽  
Strength Tests ◽  
Loading System ◽  
Ice Strength

In the winter of 1979/80, five petroleum companies participated in an Exxon Production Research Company program in which thirteen large-scale ice strength tests were conducted offshore in the vicinity of Prudhoe Bay. The purpose of the program was to determine the uniaxial compressive strength of annual sea ice as a function of strain rate and direction of loading with respect to preferred crystal alignment. Full ice sheet thickness test blocks with dimensions of 10 ft × 20 ft (3.05 m × 6.10 m) were cut free from the surrounding sheet ice. A hydraulic loading system with two million pounds of force capacity was used to compress the ice blocks at constant strain rates ranging from 10−7 s−1 to 10−5 s−1. Deformation in three orthogonal dimensions along with the axial had were measured and recorded throughout the test. This paper describes the field operations and test results, including uniaxial compressive strength, stiffness, Poisson’s ratio, and failure modes. Measured ice temperature, salinity and crystallographic structure are also presented.

scholarly journals The relative strengths of debris-laden basal ice and clean glacier ice: some evidence from Taylor Glacier, Antarctica

1996 ◽  
Vol 23 ◽  
pp. 270-276 ◽  
Author(s):  
Wendy Lawson
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Mechanical Behaviour ◽  
Deformation Mechanism ◽  
Basal Ice ◽  
Basal Zone ◽  
Dominant Deformation Mechanism ◽  
Glacier Ice ◽  
Pressure Melting ◽  
Taylor Glacier

An understanding of the mechanical behaviour of the basal zone of an ice mass is fundamental to understanding the overall dynamics of that ice mass. Despite the fact that debris-laden ice is found in the basal zones of many glaciers and ice sheets, its mechanical behaviour is only poorly understood. This paper attempts to expand our knowledge of the mechanical behaviour of debris-laden ice by examining the uniaxial compressive strength of debris-laden basal ice sampled from the snout of the Taylor Glacier, Antarctica.The mechanical behaviour of debris-laden ice (debris content 5–20% by volume) under uniaxial compression, and the relationship between the behaviours of debris-laden basal ice and ‘clean’ glacier ice, is complex and variable. At the relatively warm temperatures at which uniaxial compressive strength tests were conducted in the field, debris-laden ice was generally weaker than clean glacier ice. At these temperatures, between 0° and −5°C, pressure melting was the dominant deformation mechanism in the debris-laden ice and cracking the dominant deformation mechanism in clean ice. At −25°C, however, debris-laden ice reached higher strengths than lite clean glacier ice and cracking was the dominant deformation mechanism in both ice types. The change in relationship between the strengths of debris-laden and clean ice with temperature is inferred to be attributable to the temperature dependence of the rate of pressure melting.These results suggest that the dynamic effects and significance of the presence of a debris-laden ice layer in the basal zone of an ice mass are likely to be highly variable in space and time.

Effects of hygrothermal and thermal-oxidative ageing on the open-hole properties of T800/high-temperature epoxy resin composites with different hole shapes

2019 ◽  
Vol 32 (3) ◽  
pp. 306-315 ◽  
Author(s):  
Liang Xu ◽  
Yi He ◽  
Shaohua Ma ◽  
Li Hui
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Epoxy Resin ◽  
Failure Modes ◽  
Resin Composites ◽  
Physical Ageing ◽  
Hygrothermal Ageing ◽  
Open Hole ◽  
Epoxy Resin Composites ◽  
Oxidative Ageing

T800/high-temperature epoxy resin composites with different hole shapes were subjected to hygrothermal ageing and thermal-oxidative ageing, and the effects of these different ageing methods on the open-hole properties of the composites were investigated, including analyses of the mass changes, surface topography changes (before and after ageing), fracture morphologies, open-hole compressive performance, dynamic mechanical properties and infrared spectrum. The results showed that only physical ageing occurred under hygrothermal ageing (70°C and 85% relative humidity), and the equilibrium moisture absorption rate was only approximately 0.72%. In contrast, under thermal-oxidative ageing at 190°C, both physical ageing and chemical ageing occurred. After ageing, the open-hole compressive strength of the composite laminates with different hole shapes decreased significantly, but the open-hole compressive strength after thermal-oxidative ageing was greater than that after hygrothermal ageing. Among the aged and unaged laminates, the laminates with round holes exhibited the largest open-hole compressive strength, followed by those with the elliptical holes, square holes and diamond holes. The failure modes of the laminates were all through-hole failures. The unaged samples had a glass transition temperature ( T g) of 226°C, whereas the T g of the samples after hygrothermal ageing was 208°C, which is 18°C less than that of the unaged samples, and the T g of the samples after thermal-oxidative ageing was 253°C, which is 27°C greater than that of the unaged samples.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

scholarly journals Experimental Research on Reinforced Concrete Columns Strengthened with Steel Jacket and Concrete Infill

2021 ◽  
Vol 11 (9) ◽  
pp. 4043
Author(s):  
Aleksandar Landović ◽  
Miroslav Bešević
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Cross Section ◽  
Experimental Research ◽  
Failure Modes ◽  
Steel Tube ◽  
Rc Columns ◽  
Rc Column ◽  
Steel Jacket ◽  
Ductile Behavior

Experimental research on axially compressed columns made from reinforced concrete (RC) and RC columns strengthened with a steel jacket and additional fill concrete is presented in this paper. A premade squared cross-section RC column was placed inside a steel tube, and then the space between the column and the tube was filled with additional concrete. A total of fourteen stub axially compressed columns, including nine strengthened specimens and five plain reinforced concrete specimens, were experimentally tested. The main parameter that was varied in the experiment was the compressive strength of the filler concrete. Three different concrete compression strength classes were used. Test results showed that all three cross-section parts (the core column, the fill, and the steel jacket) worked together in the force-carrying process through all load levels, even if only the basic RC column was loaded. The strengthened columns exhibited pronounced ductile behavior compared to the plain RC columns. The influence of the test parameters on the axial compressive strength was investigated. In addition, the specimen failure modes, strain development, and load vs. deformation relations were registered. The applicability of three different design codes to predict the axial bearing capacity of the strengthened columns was also investigated.

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