scholarly journals Localised strain in fissured clays: the combined effect of fissure orientation and confining pressure

2021 ◽  
Author(s):  
Erika Tudisco ◽  
Claudia Vitone ◽  
Cristina Mondello ◽  
Gioacchino Viggiani ◽  
Stefanos Athanasopoulos ◽  
...  
Keyword(s):  
Stress Level ◽  
Confining Pressure ◽  
Important Variable ◽  
Combined Effect ◽  
Image Correlation ◽  
Complex Deformation ◽  
Santa Croce ◽  
Consistent Picture ◽  
Scaly Clay ◽  
Deformation Patterns

AbstractThis paper reports the main results of an experimental study on the mechanics of intensely fissured natural clays, extending our previous studies on scaly clay from Santa Croce di Magliano. While previous work focused on the influence of the orientation of fissures with respect to the loading direction, the present investigation specifically explores an additional, important variable: the stress level. The combined effect of fissure orientation and confining pressure was studied by setting up a large campaign of plane strain compression experiments, in which different combinations of these two variables were tested. Conventional global stress–strain measurements were complemented by measuring displacement and strain fields through two-dimensional digital image correlation. Such rich information provided a clear and consistent picture of the interplay between fissure orientation and stress level and revealed complex deformation patterns, which cannot be ignored for a proper interpretation of the material response.

scholarly journals Influence of fissure inclination and confining pressure on the local behaviour of natural clays

2019 ◽  
Vol 92 ◽  
pp. 03004
Author(s):  
Erika Tudisco ◽  
Claudia Vitone ◽  
Cristina Mondello ◽  
Gioacchino Viggiani ◽  
Stephen A. Hall ◽  
...  
Keyword(s):  
Volumetric Strain ◽  
Confining Pressure ◽  
Image Correlation ◽  
Compression Tests ◽  
Confinement Pressure ◽  
Santa Croce ◽  
Deformation Processes ◽  
Natural Clays ◽  
Scaly Clay

In this experimental study the influence of fissuring orientation and confinement pressure on the mechanical behaviour of natural clays is investigated. The tested material, the scaly clay from Santa Croce di Magliano (south of Italy), is characterised by an intense network of pre-existing fissures of single orientation. Several plane strain compression tests have been conducted, under different confinement pressures (i.e., from 50 to 600 kPa), on specimens having fissures with vertical, medium and horizontal inclination. Digital Image Correlation has been used to follow the deformation processes of the specimens throughout the tests by measuring incremental shear and volumetric strain maps. The results showed a strong coupling between the total confinement and the fissure inclination, that is controlling both the onset and the development of the patterns of the localisation processes. The new results have been compared with previous ones carried out on the same material without confinement. The comparison shed light on the role of total confinement that becomes particularly relevant from certain levels of pressures and fissuring inclination.

scholarly journals Prediction Models of Shear Parameters and Dynamic Creep Instability for Asphalt Mixture under Different High Temperatures

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2542
Author(s):  
Junxiu Lv ◽  
Xiaoyuan Zhang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Stress Level ◽  
Prediction Models ◽  
Asphalt Mixture ◽  
Confining Pressure ◽  
Shear Strength Parameters ◽  
Dynamic Creep ◽  
Shear Stress Level ◽  
Creep Instability

This study mainly investigates the prediction models of shear parameters and dynamic creep instability for asphalt mixture under different high temperatures to reveal the instability mechanism of the rutting for asphalt pavement. Cohesive force c and internal friction angle φ in the shear strength parameters for asphalt mixture were obtained by the triaxial compressive strength test. Then, through analyzing the influence of different temperatures on parameters c and φ, the prediction models of shear strength parameters related to temperature were developed. Meanwhile, the corresponding forecast model related to confining pressure and shear strength parameters was obtained by simplifying the calculation method of shear stress level on the failure surface under cyclic loading. Thus, the relationship of shear stress level with temperature was established. Furthermore, the cyclic time FN of dynamic creep instability at 60 °C was obtained by the triaxial dynamic creep test, and the effects of confining pressure and shear stress level were considered. Results showed that FN decreases exponentially with the increase in stress levels under the same confining pressure and increases with the increase in confining pressure. The ratio between shear stress level and corresponding shear strength under the same confining pressure was introduced; thus, the relationship curve of FN with shear stress level can eliminate the effect of different confining pressures. The instability prediction model of FN for asphalt mixture was established using exponential model fitting analysis, and the rationality of the model was verified. Finally, the change rule of the parameters in the instability prediction model was investigated by further changing the temperature, and the instability forecast model in the range of high temperature for the same gradation mixture was established by the interpolation calculation.

scholarly journals Researches on the Constitutive Models of Artificial Frozen Silt in Underground Engineering

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Yugui Yang ◽  
Feng Gao ◽  
Hongmei Cheng ◽  
Yuanming Lai ◽  
Xiangxiang Zhang
Keyword(s):  
Mechanical Characteristic ◽  
Stress Level ◽  
Strain Softening ◽  
Triaxial Compression ◽  
High Stress ◽  
Constitutive Models ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Conventional Triaxial Compression ◽  
Shear Process

The researches on the mechanical characteristic and constitutive models of frozen soil have important meanings in structural design of deep frozen soil wall. In the present study, the triaxial compression and creep tests have been carried out, and the mechanical characteristic of frozen silt is obtained. The experiment results show that the deformation characteristic of frozen silt is related to confining pressure under conventional triaxial compression condition. The frozen silt presents strain softening in shear process; with increase of confining pressure, the strain softening characteristic gradually decreases. The creep curves of frozen silt present the decaying and the stable creep stages under low stress level; however, under high stress level, once the strain increases to a critical value, the creep strain velocity gradually increases and the specimen quickly happens to destroy. To reproduce the deformation behavior, the disturbed state elastoplastic and new creep constitutive models of frozen silt are developed. The comparisons between experimental results and calculated results from constitutive models show that the proposed constitutive models could describe the conventional triaxial compression and creep deformation behaviors of frozen silt.

Tearing Resistance of Advanced Double Hulls

1997 ◽  
Vol 41 (01) ◽  
pp. 69-80
Author(s):  
Mark D. Bracco ◽  
Tomasz Wierzbicki
Keyword(s):  
Steady State ◽  
Cutting Force ◽  
Average Error ◽  
Small Scale ◽  
Complex Deformation ◽  
Scale Models ◽  
State Force ◽  
Deformation Patterns ◽  
Double Hull ◽  
Tearing Resistance

This paper studies the cutting by a wedge of advanced double hull (ADH) small-scale models. A total of six cutting experiments were performed with six different wedge geometries. Complex deformation patterns observed in the damaged specimens were simplified to obtain a closed-form upper bound for the steady-state cutting force. The ADH steady-state cutting force solution varied from 6% above to 12% below the experimental mean steady-state force. The absolute average error is 5%.

scholarly journals Strain Distribution of Intact Rat Rotator Cuff Tendon-to-Bone Attachments and Attachments With Defects

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Ryan C. Locke ◽  
John M. Peloquin ◽  
Elisabeth A. Lemmon ◽  
Adrianna Szostek ◽  
Dawn M. Elliott ◽  
...  
Keyword(s):  
Area Under The Curve ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Defect Group ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Transverse Strain ◽  
Intact Group ◽  
Deformation Patterns ◽  
Insight Into

Abstract This study aimed to experimentally track the tissue-scale strains of the tendon–bone attachment with and without a localized defect. We hypothesized that attachments with a localized defect would develop strain concentrations and would be weaker than intact attachments. Uniaxial tensile tests and digital image correlation were performed on rat infraspinatus tendon-to-bone attachments with defects (defect group) and without defects (intact group). Biomechanical properties were calculated, and tissue-scale strain distributions were quantified for superior and inferior fibrous and calcified regions. At the macroscale, the defect group exhibited reduced stiffness (31.3±3.7 N/mm), reduced ultimate load (24.7±3.8 N), and reduced area under the curve at ultimate stress (3.7±1.5 J/m2) compared to intact attachments (42.4±4.3 N/mm, 39.3±3.7 N, and 5.6±1.4 J/m2, respectively). Transverse strain increased with increasing axial load in the fibrous region of the defect group but did not change for the intact group. Shear strain of the superior fibrous region was significantly higher in the defect group compared to intact group near yield load. This work experimentally identified that attachments may resist failure by distributing strain across the interface and that strain concentrations develop near attachment defects. By establishing the tissue-scale deformation patterns of the attachment, we gained insight into the micromechanical behavior of this interfacial tissue and bolstered our understanding of the deformation mechanisms associated with its ability to resist failure.

scholarly journals Oblique collision and deformation partitioning in the SW Iberian Variscides

Solid Earth ◽  
2016 ◽  
Vol 7 (3) ◽  
pp. 857-872 ◽  
Author(s):  
Irene Pérez-Cáceres ◽  
José Fernando Simancas ◽  
David Martínez Poyatos ◽  
Antonio Azor ◽  
Francisco González Lodeiro
Keyword(s):  
Finite Strain ◽  
Lateral Displacement ◽  
Point Of View ◽  
Variscan Orogeny ◽  
Strain Partitioning ◽  
Complex Deformation ◽  
Oblique Collision ◽  
Deformation Partitioning ◽  
Oblique Convergence ◽  
Deformation Patterns

Abstract. Different transpressional scenarios have been proposed to relate kinematics and complex deformation patterns. We apply the most suitable of them to the Variscan orogeny in SW Iberia, which is characterized by a number of successive left-lateral transpressional structures developed in the Devonian to Carboniferous period. These structures resulted from the oblique convergence between three continental terranes (Central Iberian Zone, Ossa-Morena Zone and South Portuguese Zone), whose amalgamation gave way to both intense shearing at the suture-like contacts and transpressional deformation of the continental pieces in-between, thus showing strain partitioning in space and time. We have quantified the kinematics of the collisional convergence by using the available data on folding, shearing and faulting patterns, as well as tectonic fabrics and finite strain measurements. Given the uncertainties regarding the data and the boundary conditions modeled, our results must be considered as a semi-quantitative approximation to the issue, though very significant from a regional point of view. The total collisional convergence surpasses 1000 km, most of them corresponding to left-lateral displacement parallel to terrane boundaries. The average vector of convergence is oriented E–W (present-day coordinates), thus reasserting the left-lateral oblique collision in SW Iberia, in contrast with the dextral component that prevailed elsewhere in the Variscan orogen. This particular kinematics of SW Iberia is understood in the context of an Avalonian plate salient currently represented by the South Portuguese Zone.

scholarly journals Progressive Deformation Patterns from an Accretionary Prism (Helminthoid Flysch, Ligurian Alps, Italy)

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 26 ◽  
Author(s):  
Pierre Mueller ◽  
Matteo Maino ◽  
Silvio Seno
Keyword(s):  
Regional Scale ◽  
Kinematic Model ◽  
Outer Part ◽  
Accretionary Prism ◽  
Shear Zones ◽  
Low Grade ◽  
Progressive Deformation ◽  
Complex Deformation ◽  
Ligurian Alps ◽  
Deformation Patterns

This paper reports the results of a field-based structural investigation of a well-exposed paleo-accretionary prism, which experienced complex deformation in a low-grade metamorphic setting. Field analyses focused on the description of structural fabrics, with the main emphasis upon parameters like the orientation, style and kinematics of foliations, folds and shear zones. We address the research to the south-westernmost part of the Alpine chain, the Ligurian Alps, where, despite their origin as turbidite sequences deposited into the closing Alpine Tethys Ocean, the Helminthoid Flysch Nappes are presently distributed in the outer part of the chain, above the foreland. The new dataset highlights different deformation patterns related to the different spatial distribution of the flysch units. This regional-scale partitioning of strain is hence associated with progressive deformation within a two-stage geodynamic evolution. Correlations among the different orogenic domains allow the proposal of a kinematic model that describes the motion of the Helminthoid Flysch from the inner to the outer part of the orogen, encompassing the shift from subduction- to collision-related Alpine geodynamic phases.

Effect of particle size and strain conditions on the strength of crushed basalt

1983 ◽  
Vol 20 (4) ◽  
pp. 706-717 ◽  
Author(s):  
Mosaid Al-Hussaini
Keyword(s):  
Particle Size ◽  
Stress Level ◽  
Level Density ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Strain Diagram ◽  
Compression Tests ◽  
Cohesionless Soils ◽  
Lower Shear

This paper describes the results of an investigation carried out to study the influence of particle size, stress level, density, method of consolidation, and strain conditions on the strength and compressibility of crushed basalt. All specimens were prepared at medium or high density, consolidated isotropically or under K0 consolidation, and sheared under effective confining pressure ranging from 443 to 2297 kPa. The material used in the test program had a straight line grain size distribution with maximum particle size ranges from 0.63 to 76.2 mm and minimum particle size equivalent to No. 30 U.S. standard sieve size:The tests indicated that an increase in the particle size (i.e., gradation) increases the strength and decreases the axial and the volumetric strain at failure. The study indicated further that the crushed basalt under triaxial compression has a lower shear strength than when sheared under plane strain conditions. Particles crushed were significantly influenced by the stress level and gradation and to a lesser degree by density of material. Keywords: cohesionless soils, density (mass/volume), shear tests, stress–strain diagram, compression tests, rockfill dams.

Temperature Dependency of the Deformation Behavior of Hybrid CFRP/Elastomer/Metal Laminates under 3-Point Bending Loads

2019 ◽  
Vol 809 ◽  
pp. 259-265
Author(s):  
Vincent Sessner ◽  
Kay André Weidenmann
Keyword(s):  
Deformation Behavior ◽  
Galvanic Corrosion ◽  
Image Correlation ◽  
Constrained Layer Damping ◽  
Bending Vibrations ◽  
Complex Deformation ◽  
Damping Behavior ◽  
Different Temperatures ◽  
Bending Loads ◽  
Soft Elastomer

Fibre-metal-elastomer laminates offer the possibility of using material combinations which often have to deal with premature delamination, for example due to different coefficients of thermal expansion or galvanic corrosion due to different electronegativities. The present study deals with laminates made of layers of CFRP and aluminum, each of which is bonded together by an elastomer layer. The shear-soft elastomer also allows the much stiffer aluminum and CFRP layers to be sheared off against each other under bending stress. This leads to complex deformation behavior. The shear of the elastomer also plays a crucial role in the damping behavior of the laminate. Due to large shear deformations in the elastomer layer, the combination of rigid layers and soft elastomer layers shows very good damping behavior according to the principle of constrained layer damping. Since bending vibrations that occur during normal use usually have only small amplitudes, the deformation behavior is of particular interest in the elastic range. Since this deformation behavior is strongly dependent on the shear modulus of the elastomer used and this in turn is strongly influenced by temperature, the deformation behavior is characterized at different temperatures. Within the scope of this investigation, quasi-static 3-point bending tests are carried out on different laminate lay-ups in the temperature range from -40 °C to +80 °C. The laminates are consolidated by compression molding and contain two different EPDM elastomers in varying layer thicknesses, unidirectional CFRP prepreg in biaxial layer lay-up and aluminum 2024 sheets. The deformation behavior is analyzed by digital image correlation. This is used to measure both the bending line of the overall composite and strains over the layer thickness. In particular, the shear in the elastomer layers is evaluated and set in relation to the bending lines. Finally, the ability of the laminate lay-up to damp bending vibrations is evaluated.

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