Discussion on 'Shape fabrics and superimposed simple shear strain in a Precambrian shear belt, W Greenland' by John Grocott

1979 ◽  
Vol 136 (4) ◽  
pp. 497.1-500
Author(s):  
John Grocott ◽  
P. Allen ◽  
M. K. Wells
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Rock Masses ◽  
Structural History ◽  
Field Area ◽  
Different Parts ◽  
Shear Belt

THE PRESIDENT (Professor P. Allen) asked Dr Grocott if the structural history in his field area reflected events in the broader context (e.g. jostling of the Greenland blocks).DR M. K. WELLS asked the author to comment on possible variations of fabric which might be related to lithological contrasts of major rock masses in different parts of the region. Was there any evidence to suggest that the development of some form of layered anisotropy in the rocks was a necessary preliminary to the development of the second kind of fabric he described?

§ 3. Hellenic Pottery from the Temple Site at Palaikastro

1940 ◽  
Vol 40 ◽  
pp. 40-41
Author(s):  
R. W. Hutchinson
Keyword(s):  
Hellenistic Period ◽  
Early Date ◽  
Group Of Seven ◽  
The Road ◽  
The Temple ◽  
Field Area ◽  
Different Parts

The pottery from the Post-Minoan strata on the ‘Temple Field’ (area χ) falls into three principal groups, (i) Geometric, (ii) Archaic, and (iii) Hellenistic. For the plan of the site, see BSA VIII, pl. xv.Three geometric cups are reported from Ξ 14, and Professor Bosanquet records fragments of no fewer than forty lamps and twelve torch-holders scattered over different parts of the ‘Temple Field.’ One geometric cup (BSA X, 320, fig. 20), discovered in the road E, was associated with a group of seven jugs in a fine fabric, but with a poor dark grey slip (Plate 16, No. 2: CM 4615). The early date assigned to these cups, because of their position, I believe to be erroneous, and I do not think they are earlier than the Hellenistic period.

Cyclic Simple Shear Apparatus for Low-Strain Soil Tests

1996 ◽  
Vol 1548 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Heather J. Miller ◽  
Pedro de Alba ◽  
Kenneth C. Baldwin
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Simple Shear ◽  
Recovery Period ◽  
Triaxial Tests ◽  
Cyclic Shear ◽  
Aging Period ◽  
Direct Simple Shear ◽  
Fabric Evolution ◽  
Excess Pore Pressures

A testing system has been developed to study the behavior of saturated sand under low-level cyclic shearing strains. The system has been used to determine threshold shear strain levels for fabric destruction in sand aged for different time periods. The system includes a special soil chamber and a direct simple shear (DSS) machine. To impose very small shearing strains, the DSS machine was designed to apply and measure horizontal deformations as small as 0.0005 mm (2 × 10−5 inches). Data obtained to date support the results of previous investigators who performed triaxial tests on freshly deposited samples, indicating a threshold cyclic shear strain level of approximately 0.01 percent. At strains in excess of those levels, destruction of the sand fabric occurred, as evidenced by a reduction in shear modulus at low strain levels. Subsequent modest increases in shear modulus were observed after the specimens were allowed to recover for 24 hours and then tested again. During the recovery period, drainage valves were left open to allow for dissipation of excess pore pressures and for potential consolidation during the short aging period. The DSS system was found to work well for low strain measurements. Furthermore, since shear strains are measured directly under DSS conditions (as opposed to triaxial conditions), the DSS system shows much promise as a device for studying parameters that may influence threshold shear strain levels and fabric evolution and destruction in sands.

scholarly journals Ice deformed in compression and simple shear: control of temperature and initial fabric

2012 ◽  
Vol 58 (207) ◽  
pp. 11-22 ◽  
Author(s):  
Christopher J.L. Wilson ◽  
Mark Peternell
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Critical Role ◽  
Shear Zones ◽  
Preferred Orientation ◽  
Shear Strain Rate ◽  
Compression Strain ◽  
Mechanical Evolution ◽  
Polycrystalline Ice ◽  
Strain Magnitude

AbstractLayered and polycrystalline ice was experimentally deformed in general shear involving axial compression (strain magnitude 0.5-17%) and simple shear (strain magnitude γ = 0.1-1.4). As the temperature is increased from -20°C to -2°C, there is at least a twofold enhancement in octahedral shear strain rate, which coincides with the onset of extensive dynamic recrystallization and a change in grain-size distribution at -15°C. Between -150C and -10°C the c-axis preferred orientation rapidly evolves with the initiation of two-maxima fabrics in shear zones. From -10°C to -2°C there is progressive evolution of a final c-axis pattern that is asymmetric with respect to the direction of shortening, with a strong maximum at ~5° to the pole of the shear zone, a sense of asymmetry in the direction of the shear, and a secondary maximum inclined at ~45° to the plane of shearing. An initial c-axis preferred orientation plays a critical role in the initial mechanical evolution. In contrast to established ideas, a strong alignment of basal planes parallel to the plane of easy glide inhibited deformation and there was an increased component of strain hardening until recrystallization processes become dominant.

Dynamic deformation characteristics of sands and rockfill materials

1993 ◽  
Vol 30 (5) ◽  
pp. 747-757 ◽  
Author(s):  
Nario Yasuda ◽  
Norihisa Matsumoto
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Simple Shear ◽  
Void Ratio ◽  
Dynamic Deformation ◽  
Damping Ratio ◽  
Intermediate Principal Stress ◽  
Deformation Characteristics ◽  
Confining Stress ◽  
Rockfill Materials

Cyclic torsional simple shear (CTSS) tests and cyclic triaxial (CTX) tests were carried out to investigate the dynamic deformation characteristics of sands and rockfill materials. It was found that the shear modulus and damping ratio can be expressed as a function of shear strain, void ratio, and confining stress. Also the shear modulus in CTSS tests is larger than in CTX tests because of the influence of the intermediate principal stress. When the shear strain is increased, the shear modulus (G) and damping ratio (h) of the rockfill materials were altered at smaller strains than in sands. Key words : sands, rockfill materials, torsional simple shear, shear modulus, damping ratio.

Failure state of a sand in simple shear

1988 ◽  
Vol 25 (2) ◽  
pp. 395-400 ◽  
Author(s):  
Muniram Budhu
Keyword(s):  
Stress State ◽  
Shear Strain ◽  
Simple Shear ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Shear Tests ◽  
Failure State ◽  
Failure Loads ◽  
Test Soil ◽  
Geotechnical Problems

The stress state in many practical geotechnical problems is analogous to simple shear strain. However, the devices available to test soil samples in simple shear strain impose nonuniform stress and strain fields. Consequently, the interpretation of results from simple shear tests is often questioned. In this article, results of tests on loose and dense Leighton Buzzard sand from two specially instrumented simple shear devices–Cambridge University's device and a Norwegian Geotechnical Institute type–are used to interpret the failure mode and the failure stress state. The data were obtained from the centre of the samples, a region removed from stress concentrations. Failure was observed to be initiated on vertical planes and occurred very soon after shear displacement was applied. However, neither these vertical planes nor the horizontal planes were the planes of maximum stress obliquity mobilized during the tests. Key words: deformation, failure, loads, sand, shear tests, simple shear, stresses.

Strain Accumulation Procedure During Staged Cyclic Loading of Carbonate Sediments

2014 ◽  
Author(s):  
Nathalie Boukpeti ◽  
Barry Lehane ◽  
J. Antonio H. Carraro
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Shear Strain ◽  
Simple Shear ◽  
Soil Strength ◽  
Carbonate Sediments ◽  
Strain Accumulation ◽  
Shear Tests ◽  
Cyclic Shear ◽  
North West

Design of offshore foundation systems requires assessment of the effects of cyclic loading on the soil strength. This paper investigates the applicability of the strain accumulation procedure, which is used to assess the effects of wave loading on the soil strength. Staged undrained cyclic simple shear tests were conducted on a carbonate sediment from the North West shelf of Australia, with varying shear stress amplitude in each stage. The shear strain mobilised at the end of the staged tests is compared with the value predicted by the strain accumulation procedure, using shear strain contours constructed from the results of single amplitude undrained cyclic simple shear tests. It was found that the strain accumulation procedure gives adequate prediction for normalised cyclic shear stress less or equal to 0.3, but largely underestimates the cyclic shear strain for normalised cyclic shear stress greater than 0.3 (the cyclic shear stress being normalised by the effective vertical stress at the end of consolidation).

scholarly journals Deformation rates in combined compression and shear for ice which is initially isotropic and after the development of strong anisotropy

1996 ◽  
Vol 23 ◽  
pp. 247-252 ◽  
Author(s):  
Li Jun ◽  
T.H Jacka ◽  
W.F. Budd
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Stress State ◽  
Strain Rate ◽  
Shear Strain ◽  
Uniaxial Compression ◽  
Simple Shear ◽  
Strain Rates ◽  
Shear Strain Rate ◽  
State Dependent

Laboratory-prepared fine-grained, initially isotropic polycrystalline ice samples were deformed under conditions of simple shear with simultaneous uniaxial compression at a constant temperature of −2.0°C. The aim was to investigate the effects of stress configuration on the flow rate of initially isotropic ice and on ice with subsequent stress and strain-induced anisotropy. Experiments were carried out for various combinations of shear and compression with shear stress ranging from 0 to 0.49 MPa and compressive stress ranging from 0 to 0.98 MPa, but such that for every experiment the octahedral shear stress was 0.4 MPa.The strain curves resulting from the experiments clearly exhibit minimum strain rates while the ice is still isotropic, and steady-state tertiary strain rates along with the development of steady-state anisotropic fabric patterns. With constant octahedral stress (root-mean-square of the principal stress deviators), the minimum octahedral shear-strain rate has no dependence on stress configuration. This result supports the hypothesis that the flow of isotropic ice is dependent only on the second invariant of the stress tensor. This fundamental assumption has been used to provide a general description of ice-flow behaviour independent of the stress configuration (e.g. Nye, 1953; Glen, 1958; Budd, 1969).For the tertiary flow of anisotropic ice, the octahedral strain rate is stress-state dependent as a consequence of the developed crystal-orientation fabric, which is also stress-state dependent, and which develops with strain and rotation. The present tests indicate that the enhancement factor for steady-state tertiary octahedral shear-strain rate depends on the shear or compression fraction and varies from about 10 for simple shear (with zero compression) to about 3 for uniaxial compression (with zero shear).

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