Automatic feedback system for resonant column testing

Automatic feedback system for resonant column testing

274A 905154 Some factors affecting the liquefaction and flow of saturated sands in laboratory tests Hird, C C; Hassona, F A K Engng Geol V28, N1/2, F...

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274A

905154 Some factors affecting the liquefaction and flow of saturated sands in laboratory tests Hird, C C; Hassona, F A K Engng Geol V28, N1/2, Feb 1990, P149-170

905158 Simplified finite element analysis of wave-induced effective stresses and pore pressures in permeable sea beds Gatmiri, B Geotechnique 1/40. N1, March 1990. P15-30

Liquefaction of sands under monotonic loading has been examined in a series of load controlled undrained triaxial tests. Influences of strain rate, particle shape, compressibility, specimen preparation and stress history are studied. All samples could liquefy under suitable conditions. At given conditions of confining pressure and void ratio, the more angular sands are less likely to liquefy than those with rounded particles. Presence of soft particles, which enhances compressibility, also lowers liquefaction susceptibility. Results are discussed within established conceptual frameworks.

A numerical solution of the general Biot theory is used to estimate the stability of the seabed and the distribution with depth of wave induced pore pressures and effective stress. Validation of simplifying assumptions of the finite element code COHET is made by comparing output with published solutions. Effects of bed thickness, and soil stiffness and permeability on distribution of pore pressure and effective stress are studied. Response of heterogeneous and homogeneous sea beds to harmonic loading, and the case of a sloping sea bed are examined.

905155 Hole geometry and anlsotropic effects on tube-wave propagation: a quasi-static study Nicoletis, L M A; Bamberger, A: Quiblier, J A; Joly, P; Kern, M Geophysics V55, N2, Feb 1990, P167-175 Tube wave propagation in a borehole is affected by borehole anomalies associated with the effects of the in situ stress field (non-hydrostatic). The case of wave propagation in a fluid filled borehole of arbitrary shape is first examined. The effects of ellipticity of hole are considered analytically, those of azimuthal anisotropy numerically, using finite element analysis. Local damage can significantly reduce tube wave velocity. It is not possible to obtain valuable information on stress direction from tube waves.

905156 Hyperbolic travcltime analysis of first arrivals in an azimuthally anlsotropic medium: a physical model study Ebrom, D A; Tatham, R H; Sekharan, K K; McDonald, J A; Gardner, G H F Geophysics I,'55, N2, Feb 1990, P185-191 Physical models representing anisotropic geologic materials were made using layers of Plexiglas with thin films of water, held under moderate uniaxial compression. For materials with parallel, vertical fractures, moveout curves were hyperbolic for a surface line parallel to the fractures, but non-hyperbolic for a line perpendicular. Q anisotropy is observed, with strongest attenuation in propagation paths perpendicular to the fractures.

905157 Automatic feedback system for resonant column testing Morris, D V Goetech Test J V13, N1, March 1990, P16-23 Circuitry and a test method to simplify measurements during resonant column tests are described. It uses a feedback system to automatically detect resonance. Consistent and controllable strain level are ensured. Variations in resonant frequency due to changes in applied cell pressure or strain level can be automatically followed and displayed. Direct digital output of strain level is also possible. An alternative, rapid method of measuring damping is suggested.

905159 Overview of projectile penetration into geological materials, with emphasis on rocks Heuze. F E Int J Rock Mech Min Sci V27. N1, Feb 1990. PI-14 Experimental and analytical data on projectile penetration into geological materials are reviewed. Work has concentrated on soils, with few instrumented penetration tests on rocks. Empirical approaches (Sandia National Laboratories, Waterways Experimental Station), analytical cavity expansion and differential area force law approaches, and numerical methods are examined. The many penetration models are summarised, and some evaluations and comparisons are made. Rock mechanical and structural aspects are discussed. 145 refs.

905160 Experimental study and analysis of the behaviour of rock under cyclic loading. Technical note Tao Zhenyu; Mo Haihong lnt J Rock Mech Min Sci V27, NI. Feb 1990, P51-56 Behaviour is described of marble and sandstone under cyclic loading, with different loading waveforms and control modes, and lateral deformation measurement. Total deformation has initial static, creep, and damage components, the last being the major contribution to failure. Critical strength is lower than static strength and related to loading rate, amplitude and waveform. Cyclic amplitude and loading waveform have significant influences on deformation. Lateral deformation develops at a faster rate than axial deformation. The endochronic constitutive equation describes observed behaviour satisfactorily.

905161 Influence of buildings on potential liquefaction damage Rollins, K M; Seed, H B J Geotech Engng Div ASCE VII6, N2, Feb 1990, P165-185 Field case histories, shaking table tests and centrifuge models indicate that excess pore pressure distributions near a building can differ significantly from those in the free field, and free field assumptions in liquefaction analysis may be erroneous. Modifications are suggested to take account of soil structure interaction, vertical stresses, horizontal shear stresses and overconsolidation. Liquefaction damage may be greater or lesser than that in the free field, depending on soil density and building type, sand liquefaction potential being increased below short period, low rise buildings and decreased below long period, high rise buildings.

i ~ 1990 Pergamon Press plc. Reproduction not permitted