Showing papers on "Discontinuity (geotechnical engineering) published in 1982"

Magnetisation discontinuity of the two-dimensional Potts model

Abstract: The q-state two-dimensional ferromagnetic Potts model has a first-order transition for q>4, its spontaneous magnetisation having a jump discontinuity. The magnitude of this discontinuity is calculated exactly for the square, triangular and honeycomb lattices: it depends only on q and is the same for all three lattices.

Evidence for a seismic discontinuity near 200km depth under a continental margin

Abstract: Summary. We present evidence for a seismic discontinuity near 200 km depth (the Lehmann Discontinuity) under the passive continental margin of north- west Australia, where continental lithosphere merges into oceanic lithosphere. The velocity contrast across the discontinuity is 0.2-0.3 km s-', and is similar to the contrast across discontinuities at similar depths in seismic models for purely continental paths to the east under central Australia. The discontinuity has been shown to be present under continents, oceans and now at continental margins, and is probably a worldwide feature.

Evolution of weak discontinuity waves in self-similar flows and formation of secondary shocks. The "point explosion model"

Abstract: In this paper we consider a quasi-linear hyperbolic system in two independent variables (space and time), to evaluate the “critical time” for weak discontinuity waves travelling in self-similar flows like those generated by a “point explosion”

Endless conveyor system

Abstract: An endless conveyor system for moving load bearing units along a path defined by the conveyor system which has a discontinuity or gap along the path such as may be required to accommodate a conveyor system drive or tensioning device. The endless conveyor system includes a transfer station located at the discontinuity or gap to move the load bearing units across the discontinuity without interruption to the flow of load bearing units along the path.

Wave Tilt Fluctuations near a Vertical Discontinuity in a Flat Ground Plane

Abstract: Using microwaves (4.8 GHz) and laboratory models, the electric field tilt was measured across a horizontal plane having an abrupt transition from a highly inductive surface to a highly conductive surface. The wave tilt was found to exhibit an interference pattern in front of the boundary. This phenomenon can be explained in terms of the reflection and backscattering from the boundary region. It is predicted that this effect will be observable in wave tilt measurements made on the earth's surface, and may result in the misleading interpretation of field data in addition to obscuring the effect of real changes in local ground conductivity. Surface impedance measurements, however, should not suffer from this problem. The experimental results further support the idea that accurate interpretation of ground parameters from wave tilt and surface impedance measurements cannot be made within a distance of one wavelength (measured in the earth) from any substantial lateral discontinuity. The highly inductive surface consisted of a grounded pin bed (aniso. tropic) structure. Since the subsurface field in such a structure must propagate normal to the surface, it is ideal for synthesizing surface impedances for propagation over the earth which has a large index of refraction.

Discontinuity in conversational speech : an investigation of some theoretical problems and their analysis

Abstract: The occurrence of discontinuity in conversational speech raises a variety of theoretical problems for the study of verbal communication. According to the dominant explanatory models of language, discontinuities in the form of pauses, self-corrections, repeats, false starts, and the like are errors'of language performance. Consequently, when, inconversational speech, discontinuities do occur, it is natural that questions should arise regarding (a) why they occur and (b) given that they do occur, how speakers and hearers are able to deal with them. It is argued that no coherent answers may be offered to these questions under the prevalent conceptualization of discontinuity. As a feature of verbal performance, discontinuity has been studied primarily by researchers from the related disciplines of psychology, sociology, ethnomethodology, and discourse analysis. Although the explanatory approaches differ greatly, there is an underlying presuppositional unity to them. Whether discontinuity is studied as an indication of the speaker's cognitive processing, as a feature of social differentiation, or as an essential aspect of the speaker and hearer's ~ management of conversational interaction, it is always assumed that discontinuities occur as the result of speaker error. This assumption, in turn, is shown to be derived from an unrecognised written-language (or 'scriptist') bias in the study of verbal communication. This conceptual bias, it is argued, is a shared weakness in the otherwise differing theoretical approaches to the explanation of discontinuity in conversational speech. The theoretical discussion of the thesis is supplemented by an appendix containing a selection of transcribed examples of discontinuities compiled with the aid of a computer concordance program. These examples are used as comparative evidence throughout the central chapters of the thesis. Discontinuity in Conversational Speech: an investigation of some theoretical problems and their analysis. Talbot J. Taylor Trinity College Thesis submitted for the degree of D.Phil, in Michaelmas term, 1981.

Stratigraphy -- The Fall of Continuity

Abstract: The twentieth-century theme of discontinuity has begun to invade stratigraphy. It is implicit in the recently-developed sea-level curve and in the realization that fracture rather than simple flexure controls basin development. The recognition of discontinuity in the stratigraphic record is changing our views of two of Steno's principles, Superposition and Original Lateral Continuity. Small-scale vertical discontinuity is exemplified by bedform migration, storm deposition, turbidite sedimentation, fan or delta-lobe switching, channel or inlet migration. On a larger scale, transgressive overstep marked by a subtle disconformity is a common feature in the record. Its recognition has led to a new model for cyclothem deposition, in which the cycles are strongly asymmetric and regressive dominant. Similar cycles have been advocated for carbonate sequences. Transgressive disconformities are important to identify, because their presence invalidates the use of Walther's Law. Vertical discontinuity on a grand scal...

Seismic waves from a horizontal stress discontinuity in a layered solid

Abstract: The displacement components for a horizontal stress discontinuity along a buried finite fault in an elastic homogeneous layer on top of an elastic half-space are given analytically in terms of generalized rays. For a particular case of a concentrated horizontal force pointing in an arbitrary direction, detailed time-dependent expressions are given. For a simple model of a “crustal” layer over a “mantle” half-space, the numerical seismograms in the near- and intermediate-field show some interesting features. These include a prominent group of compressional waves whose radial component is substantial at distances four times the crustal thickness. All the dominant shear arrivals ( s , SS , and sSS ) are important and show large variations of amplitude as the source depth and receiver distance are varied. Some of the prominent individual generalized rays are shown, and it is found that they can be grouped naturally into families based on the number of interactions with the boundaries. The subdivision into individual generalized rays is useful for analysis and for checks on the numerical stability of the synthetic seismograms. Since the solution is analytic and the numerical evaluation is complete up to any desired time, the results are useful in comparing other approximate methods for the computation of seismograms.

Behaviour of a Discontinuity at the Wave-Head Propagating Through a Relaxing Gas

Abstract: The rate of amplification of a discontinuity in the velocity gradient is evaluated at the wave-head in a spatially uniform but time evolving flow of a relaxing gas. The paper investigates the effects of relaxation (present in the flow) and the initial wave front curvature on the growth and decay behaviour of waves in the thermodynamical state of weak or strong equilibrium.

In-situ stress determinations in northeastern ohio.

Abstract: During construction of the intake tunnels for a nuclear power facility in Ohio, evidence of a potential geological discontinuity was discovered. Assuming that the discontinuity might still prevail underneath the site, it was decided to measure the stress profile across the discontinuity. Seven intervals were hydraulically fractured to determine the magnitude and orientation of the stress tensor, in order to infer the shear stresses acting along the discontinuity. The formation consists of tightly interbedded shales. This, in combination with the shallow depths, would be expected to lead to horizontal hydraulic fractures. Careful testing procedures, and meticulous interpretation, allowed the determination of the horizontal stress components as well as the vertical component, via the initiation and/or propagation of multiple fractures. The measured stresses fall within the range of stress magnitudes and orientation determined in other areas of the northeastern and north-central United States and in southern parts of Canada. In addition, a small stress gradient anomaly was recorded at depth. On a different scale, the measured stress regime is also evaluated in light of the regional geological setting. For the covering abstract of the symposium see TRIS 452576. (Author/TRRL)

On the effect of the higher modes on the scattering of Love waves at the boundary of welded layered quarter-spaces

Abstract: In this paper, we investigate the effect of higher modes on the scattering of plane, harmonic Love waves, normally incident (from either side) upon the plane of discontinuity in the horizontally discontinuous structure consisting of welded layered quarter-spaces with a plane surface. We find that the effect of the higher modes on the scattering of an incident fundamental mode from hard into the soft medium is considerable for large impedance contrasts with or without body-wave conversion, and is negligible when the impedance contrast is low. Our results indicate that contributions from body-wave conversion are important in higher Love mode studies when there is large contrast in the elastic constants of the media on the two sides of the vertical plane of discontinuity.

Spontaneous emission of waves by a fast shock wave in a longitudinal magnetic field

Abstract: The stability of a fast longitudinal shock wave against weak perturbations of the discontinuity surface is investigated within the framework of ideal magnetohydrodynamics. It is shown that the region of spontaneous emission of waves by the discontinuity in a plasma with an arbitrary equation of state is determined by the magnetic field, and is broader than the corresponding region in ordinary hydrodynamics. In a sufficiently strong magnetic field, the spontaneous wave emission by the discontinuity can occur in an ideal gas with a constant specific heat.

Method and apparatus for optical fiber fault location

Abstract: METHOD AND APPARATUS FOR OPTICAL FIBER FAULT LOCATION A discontinuity within a fiber is located using a reflectometry technique. A swept frequency sinusoidal signal is launched into the fiber from one end and propagates along the fiber. If the discontinuity is reflecting the signal is reflected, while if non-reflecting, backscatter is markedly reduced. Both conditions can be monitored when a signal returned to the fiber input end interferes constructively or destructively with the input signal depending on the phase difference between them. Both the amplitude and phase of the resulting interference signal vary periodically with frequency. From the periodicity, the distance from the input end of the fiber to the discontinuity can be derived.

The Circular Crack as a Surface Defect

Abstract: The circular crack is considered as a defect in a linearly elastic medium. Presented is the mathematical formulation of the crack problem by application of the elastic potential of a double layer. This leads to a singular integral equation that solves for the displacement discontinuity.