Browsing by Author "Liou, JC"

Now showing 1 - 6 of 6

A fall-velocity equation - Discussion
(2001-07-01)
Chang, HK
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Liou, JC
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土木工程學系
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Department of Civil Engineering
Fabric evolution of granular assembly under K-0 loading/unloading
(2003-11-01)
Liou, JC
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Pan, YW
;
土木工程學系
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Department of Civil Engineering
This study attempted to investigate the fabric evolution in K-0 loading/unloading. The work made use of a field simulator to control K-0 loading/unloading in large specimens prepared by air-pluviation. In each loading stage, wave velocities along various propagation directions were measured. On the basis of the theories of micro-mechanics and wave propagation, the microscopic parameters of the granular assembly were back calculated to investigate the fabric evolution of granular soil during K-0 loading/unloading. In this study, the Geometric fabric was modelled by fabric tensors of ranks 2 and 4. The comparison of calibrated results using ranks 2 and 4 revealed the advantage of the usage of rank-4 fabric tensor in modelling fabric evolution in spite of its complexity. By comparing relative magnitudes of vertical and horizontal components of geometric fabric, it was demonstrated that relative constraint in lateral directions increased during K-0-unloading in order to maintain a K-0 condition. It revealed that fabric evolution was responsible for a higher K-0 in unloading than K-0 in loading. Copyright (C) 2003 John Wiley Sons, Ltd.
K-0 estimation in level granular soil from anisotropic wave velocities on the basis of micromechanics
(2004-12-10)
Pan, YW
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Liou, JC
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土木工程學系
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Department of Civil Engineering
This study aims to explore the possibility for estimating K-0 in a level ground of granular soil by seismic methods on the basis of micromechanics theory. The idea was to simulate in situ cross-hole seismic method for the measurement of wave velocities along various directions of wave-propagation. This work made use of a field simulator to control a K-0 condition (zero lateral strain condition) in specimens. A series of vertical loading containing subsequent loading and unloading were applied to the specimen prepared by pluviation. In general, the K-0 values determined experimentally in this work agreed with the exiting empirical relations. K-0 value was also calibrated from measured anisotropic wave velocities using an optimization procedure. From the comparison of the back-calculated and measured results of K-0, it revealed the feasibility for the determination of the in situ lateral stress in granular soil by seismic methods and on the basis of micromechanics theory as long as enough wave-velocity measurements along various directions of wavepropagation were available. The potential for the usage of the presented methodology for the determination of the in situ lateral stress in level-ground of granular soil by seismic methods seems encouraging. Copyright (C) 2004 John Wiley Sons, Ltd.
Long wave reflection and transmission over a sloping step
(2004)
Chang, HK
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Liou, JC
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土木工程學系
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Department of Civil Engineering
This investigation examines long wave reflection and transmission induced by a sloping step. Bellman and Kalaba's (1959) invariant imbedding is introduced to find wave reflection. An alternative method matching both the surface elevation and its surface slope of each region at the junction is applied to the determination of wave reflection and transmission. The proposed methods are compared with the accurate numerical results of Porter and Porter (2000) and those of Mei (1983) for a vertical step. The wave reflection obtained for a mildly sloping step differs significantly from the result of Mei. ne wave reflection is found to fluctuate owing to wave trapping for the mild sloping step. The height and the face slope of the step are important for determining wave reflection and transmission coefficients.
Solving wave dispersion equation for dissipative media using homotopy perturbation technique
(2006-01-01)
Chang, HK
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Liou, JC
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土木工程學系
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Department of Civil Engineering
This investigation develops a third-order explicit approximation to finding the roots of the dispersion relation for water waves that propagate over dissipative media, using homotopy perturbation. The proposed third-order approximation can give an explicit and accurate calculation on the inaccessible roots of the dispersion relation. The homotopy method yields global convergence to the roots. Interestingly, the contours of the domains of attraction of the roots resemble a fractal pattern.
Wave reflection over a sloping beach
(2001)
Chang, HK
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Hsu, TW
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Liou, JC
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交大名義發表
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National Chiao Tung University
A frequency domain method for separating Incident and reflected waves is proposed to account for normally incident waves propagating over a sloping beach in a wave flumes Linear wave shoaling is applied to determine changes of the wave amplitude and phase due to variations of the bathymetry. The wave reflection coefficient is estimated from wave heights measured by two fixed wave gauges with a separated distance. The method is applicable to both monochromatic and random waves. Brief comparisons between theories and the proposed model are made for waves propagating over a sloping seabed.