scholarly journals Effects of relative density and accumulated shear strain on post-liquefaction residual deformation

2013 ◽  
Vol 13 (10) ◽  
pp. 2567-2577
Author(s):  
J. Kim ◽  
M. Kazama ◽  
Y. Kwon
Keyword(s):  
Cyclic Loading ◽  
Relative Density ◽  
Shear Strain ◽  
Axial Strain ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Monotonic Loading ◽  
Test Method ◽  
Lateral Strain ◽  
Undrained Conditions

Abstract. The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors more accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of lateral constrained-control hollow cylindrical torsion tests under undrained conditions. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0-drain after cyclic loading – in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the lateral constrained condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in situ ground. This lateral constrain control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the recovery of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structural restoration characteristics. In addition, in the ranges of 40–60% relative density and 50–100% accumulated shear strain, relative density was found to have greater effects than the number of cycles (accumulated shear strain).

scholarly journals Effects of relative density and accumulated shear strain on post-liquefaction residual deformation

2013 ◽  
Vol 1 (2) ◽  
pp. 1579-1617
Author(s):  
J. Kim ◽  
M. Kazama ◽  
Y. Kwon
Keyword(s):  
Cyclic Loading ◽  
Relative Density ◽  
Shear Strain ◽  
Axial Strain ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Lateral Spreading ◽  
Monotonic Loading ◽  
Test Method ◽  
Lateral Strain

Abstract. The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of undrained K0 control cylindrical torsional tests. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0 drain after cyclic loading-in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the K0 condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in-situ ground. This K0 control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the restoration behaviors of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structure restoration characteristics. In addition, in the ranges of 40~60% relative density and 50~100% accumulated shear strain, relative density was found to have greater effects than the number of cycles (accumulated shear strain).

Residual Deformation Behavior of Reinforced Rock-Fill Materials

2010 ◽  
Vol 150-151 ◽  
pp. 1495-1499
Author(s):  
Yong Liang Lin ◽  
Meng Xi Zhang ◽  
Xin Xing Li
Keyword(s):  
Cyclic Loading ◽  
Deformation Behavior ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Test Results ◽  
Rock Fill ◽  
Triaxial Apparatus ◽  
Deformation Behaviors ◽  
Confining Pressures ◽  
Fill Materials

Reinforcement technology is widely used in rock-fill dams in high seismic hazard zones. The evaluation of reinforcement on deformation and safety is concerned and it is one of the major study objectives in rock-fill engineering. The residual deformation behaviors of reinforced rock-fill materials were experimentally studies by use of a triaxial apparatus. The effects were analyzed of intervals of reinforcement layers, confining pressures and the conditions of cyclic loading on residual deformation. Results show that reinforcement improves the residual deformation behaviors of rock-fill materials. Both the residual shear strain and the residual volumetric strain are deduced. Based on the test results, the mechanism of the influence of reinforcement on residual deformation is proposed tentatively.

Noise Performance and Signal-to-Noise Ratio of Shear Strain Elastograms

2005 ◽  
Vol 27 (3) ◽  
pp. 145-165 ◽  
Author(s):  
Arun Thitai Kumar ◽  
Jonathan Ophir ◽  
Thomas A. Krouskop
Keyword(s):  
Shear Strain ◽  
Signal To Noise Ratio ◽  
Axial Strain ◽  
Center Frequency ◽  
Theoretical Expression ◽  
Lateral Strain ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Theoretical Results ◽  
Phantom Experiments

In this paper, we develop a theoretical expression for the signal-to-noise ratio (SNR) of shear strain elastograms. The previously-developed ideas for the axial strain filter (ASF) and lateral strain filter (LSF) are extended to define the concept of the shear strain filter (SSF). Some of our theoretical results are verified using simulations and phantom experiments. The results indicate that the signal-to-noise ratio of shear-strain elastograms ( SNRsse) improves with increasing shear strain and with improvements in system parameters such as the sonographic signal-to-noise ratio ( SNRs) beamwidth, center frequency and fractional bandwidth. The results also indicate that the amount of axial strain present along with the shear strain is an important parameter that determines the upper bound on SNRsse. The SNRsse will be higher in the absence of additional deformation due to axial strain.

Hydromechanical behaviour of overconsolidated unsaturated soil in undrained conditions

2019 ◽  
Vol 56 (11) ◽  
pp. 1609-1621 ◽  
Author(s):  
Shengshen Wu ◽  
Annan Zhou ◽  
Jie Li ◽  
Jayantha Kodikara ◽  
Wen-Chieh Cheng
Keyword(s):  
Effective Stress ◽  
Unsaturated Soils ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Conventional Triaxial Compression ◽  
Hydromechanical Behaviour ◽  
Undrained Conditions

Hydromechanical behaviour of an unsaturated silt with various suctions and different overconsolidated ratios (OCRs) was investigated through a series of undrained triaxial tests (constant water contents, CW). All the samples were prepared from the slurry state. Different OCRs (= 1, 2, 4, and 8 in net stress) were achieved by unloading the samples to 400, 200, 100, and 50 kPa from an initial confining net pressure of 400 kPa. Then the samples were dried to various suctions (0, 100, 200, 300, and 400 kPa). Unsaturated samples with different OCRs were then sheared at CW conditions following the conventional triaxial compression (CTC) paths. Full hydromechanical responses including the changes in deviator stress, stress ratio, volumetric strain, suction, and degree of saturation with axial strain were monitored and are presented in this paper. Some key findings include (i) the critical state for unsaturated soils with different OCRs can be well defined by Bishop’s effective stress; (ii) the peak strength in Bishop’s effective stress increases with increase of OCR, but decreases with increase of suction in the undrained condition; and (iii) the volume change of unsaturated soils in undrained conditions is related to OCRs and the volume of pore air.

Characterization of permanent axial strain of granular materials subjected to cyclic loading based on shakedown theory

2019 ◽  
Vol 198 ◽  
pp. 751-761 ◽  
Author(s):  
Wen-Bo Chen ◽  
Wei-Qiang Feng ◽  
Jian-Hua Yin ◽  
Lalit Borana ◽  
Ren-Peng Chen
Keyword(s):  
Cyclic Loading ◽  
Granular Materials ◽  
Axial Strain ◽  
Shakedown Theory

scholarly journals Optical Coherence Elastography Techniques for Carotid Arterial Wall Imaging

2021 ◽  
Author(s):  
Felix Nolte
Keyword(s):  
Axial Strain ◽  
Image Correlation ◽  
Arterial Blood Flow ◽  
Lateral Strain ◽  
Optical Coherence ◽  
Phantom Experiment ◽  
Arterial Blood ◽  
Speckle Patterns ◽  
Imaging Mode

In this thesis, elastography is evaluated in combination with optical coherence tomography (OCT). Two approaches to OCT based elastography, Digital image correlation (DIC) and Doppler optical coherence elastography (DOCE), are evaluated for an intravascular setup using in vivo images from a porcine carotid model. DIC tracks the displacement of speckle patterns in consecutive frames, allowing the calculation of axial and lateral strain. Rapid speckle decorrelation was observed in preprocessed structural images, affecting the tracking and limiting the feasibility of this algorithm. DOCE measures axial strain based on relative tissue velocities. Rotational movement of the imaging optical fibre was the biggest source of artefacts in this imaging mode, but could be removed with a newly developed algorithm, based on the phase change induced in a surrounding catheter. The standard deviation of phase after artefact removal, measured in a stationary phantom experiment, was ~0.2 rad, corresponding to a minimum detectable velocity of 792 μm/s at a Doppler angle of 20°. The sensitivity allowed the detection of arterial blood flow velocity and pattern and the detection of adjacent veins, but did not allow direct elastography.

scholarly journals EVOLUTION OF THE CARBON NANOTUBE BUNDLE STRUCTURE UNDER BIAXIAL AND SHEAR STRAINS

2020 ◽  
pp. 525
Author(s):  
Leysan Kh. Rysaeva ◽  
Dmitry V. Bachurin ◽  
Ramil T. Murzaev ◽  
Dina U. Abdullina ◽  
Elena A. Korznikova ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Shear Strain ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Shear Bands ◽  
Volumetric Strain ◽  
Structural Evolution ◽  
Biaxial Compression ◽  
Chain Model ◽  
Nanotube Bundle

Close packed carbon nanotube bundles are materials with highly deformable elements, for which unusual deformation mechanisms are expected. Structural evolution of the zigzag carbon nanotube bundle subjected to biaxial lateral compression with the subsequent shear straining is studied under plane strain conditions using the chain model with a reduced number of degrees of freedom. Biaxial compression results in bending of carbon nanotubes walls and formation of the characteristic pattern, when nanotube cross-sections are inclined in the opposite directions alternatively in the parallel close-packed rows. Subsequent shearing up to a certain shear strain leads to an appearance of shear bands and vortex-like displacements. Stress components and potential energy as the functions of shear strain for different values of the biaxial volumetric strain are analyzed in detail. A new mechanism of carbon nanotube bundle shear deformation through cooperative, vortex-like displacements of nanotube cross sections is reported.

scholarly journals Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading

2018 ◽  
Vol 55 (12) ◽  
pp. 1756-1768
Author(s):  
Jahanzaib Israr ◽  
Buddhima Indraratna
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Excess Pore Water Pressure ◽  
Excess Pore

This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.

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