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Showing papers on "Discontinuity (geotechnical engineering) published in 1985"


Journal ArticleDOI
TL;DR: In this article, a back-analysis technique is used to determine the behavior modes of a rock mass from an array of deformational measurements. But the model is limited to a single set of deformations.
Abstract: This paper explains a novel ‘back-analysis’ shceme to determine rock mass behaviour modes from an array of deformational measurements. The input will be the locations of data points and the set of measured displacements, as well as description of the locations and orientations of planes of discontinuity, and the blocks they determine. The output, drawn by the computer, will be the set of block displacements, rotations, and strains that determine the behavioural mode of the mass.

285 citations



Journal ArticleDOI
TL;DR: In this article, the authors focus on the deformation processes and rheologies of rocks at high temperatures and high effective pressures, conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones.

244 citations


Journal ArticleDOI
TL;DR: In this paper, a simplified theoretical analysis and the experimentally proven assumption that tensile rather than shear failure is the dominant chip forming mechanism are derived for the prediction of disc cutter performance in bedded and schistose rocks.

209 citations


Journal ArticleDOI
Fazil Erdogan1
TL;DR: In this paper, the singularity of the crack tip stress field in a nonhomogeneous medium having a shear modulus with a discontinuous derivative was investigated and the problem was solved for a finite crack and extensive results were given for the stress intensity factors.
Abstract: The singular nature of the crack tip stress field in a nonhomogeneous medium having a shear modulus with a discontinuous derivative was investigated. The problem is considered for the simplest possible loading and geometry, namely the antiplane shear loading of two bonded half spaces in which the crack is perpendicular to the interface. It is shown that the square-root singularity of the crack tip stress field is unaffected by the discontinuity in the derivative of the shear modulus. The problem is solved for a finite crack and extensive results are given for the stress intensity factors.

199 citations


Book
01 Jan 1985
TL;DR: In this article, the authors discuss stresses in pressure vessels and flat plates under external pressure, and fracture control of pressure vessels under static and dynamic external pressure in flat plate flat plates.
Abstract: Pressure vessels. Stresses in pressure vessels. Stresses in flat plates. Discontinuity stresses in pressure vessels. Fracture control. Design-construction features. Fabrication, innovation, and economics. Buckling of vessels under external pressure. Index.

110 citations


Journal ArticleDOI
TL;DR: In this paper, a line-spring model is used to model the locking and stressing of the San Andreas fault in a way equivalent to imposition of a remotely uniform tectonic shear stress.
Abstract: An analysis is presented of the stressing of locked patches along a fault zone which is creeping elsewhere. The model consists of strike-slip faulted elastic lithospheric plates loaded in a manner equivalent to imposition of a remotely uniform tectonic shear stress. The fault zone has an inhomogeneous strength distribution both depth-wise and along strike. It is modeled as being composed of locked patches and freely slipping parts treated as cracks. The solution is given with the use of the “line-spring” model which analyzes the problem by thickness-averaged plane stress theory for lithospheric plates which slip along a discontinuity cut at the plate boundary. As a boundary condition, thickness-averaged stress and slip at each local section along the cut was related to one another by the result of an antiplane strain analysis of slip for the crack or crack pair which describes the slipping and locked depth ranges at that section. The analysis indicates that the slip distribution along creeping parts of the fault, as well as the stress distribution along locked patches, depends strongly on the geometry of these zones. The model is used to examine stress concentrations associated with a slip-deficient seismic gap along strike and to study the effect of local irregularities in the margin of a locked region. It is also used to simulate slip and stressing processes associated with the creeping portion of the San Andreas fault in central California, between the presently locked zones of the great 1906 and 1857 ruptures, and to constrain the nature of an apparently locked zone at the southeastern end which ruptures in characteristic Parkfield earthquakes. Near-fault creep and broadscale displacement data along the fault since the 1966 Parkfield earthquake and inferences from seismicity distributions are used. Limitations of the modeling procedure at short spatial wavelengths prohibit an accurate description of the Parkfield locked patch, but results suggest that it may be localized and occupy a small fraction of area of the normal seismogenic zone. An effective remote stressing rate of order 0.3 × 10−6 × shear modulus/yr is inferred, together with a less well constrained 30 to 40 km lithospheric thickness, for consistency with the displacement data. Results enable estimates of stress accumulation along the locked 1857 rupture zone and the build-up of fracture energy release capability (of order 107 J/m2 in 150 yr) at its lower margin.

64 citations


Journal ArticleDOI
TL;DR: In this article, the authors used elastic-plate flexure models of mascon loading on the moon to predict the occurrence of strike-slip faulting at the radial distance where grabens are found.
Abstract: The prediction of fault type on planetary surfaces from model stresses calculated at depth is discussed. These fault-type predictions yield different faults than those predicted using the surface criteria commonly employed in geophysical models. For elastic-plate flexure models of mascon loading on the moon, stresses calculated at the surface predict the occurrence of strike-slip faulting at the radial distance where grabens are found. Normal faults bounding lunar grabens and thrust faults responsible for wrinkle ridges are analyzed. It is found that the former initiate at the mechanical discontinuity that separates the breccia of the megaregolith from in situ fractured rock and that the latter initiate at the mechanical discontinuity between basalt layers and the underlying basin floor. The difference between elastic constants for the outer few kilometers of brecciated megaregolith and the underlying lunar lithosphere are evaluated. Superposing nonisotropic stresses resulting from the weight of overburden to the depth of the relevant mechanical discontinuity yield stresses that predict wrinkle ridges in the basin centers and grabens outside the basin margin, and eliminate the predicted zone of strike-slip faults.

56 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed cracks in ductile single crystals for geometries and orientations such that two-dimensional states of anti-plane shear constitute possible deformation fields.
Abstract: Cracks in ductile single crystals are analyzed here for geometries and orientations such that two-dimensional states of anti-plane shear constitute possible deformation fields. The crystals are modelled as ideally plastic and yield according to critical resolved shear stresses on their slip systems. Restrictions on the asymptotic forms of stress and deformation fields at crack tips are established for anti-plane loading of stationary and quasistatically growing cracks, and solutions are presented for several specific orientations in f.c.c. and b.c.c. crystals. The asymptotic solutions are complemented by complete elastic-plastic solutions for stationary and growing cracks under small scale yielding, based on previous work by Rice (1967, 1984) and Freund (1979). Remarkably, the plastic zone at a stationary crack tip collapses into discrete planes of displacement and stress discontinuity emanating from the tip; plastic flow consists of concentrated shear on the displacement discontinuities. For the growing crack these same planes, if not coincident with the crack plane, constitute collapsed plastic zones in which velocity and plastic strain discontinuities occur, but across which the stresses and anti-plane displacement are fully continuous. The planes of discontinuity are in several cases coincident with crystal slip planes but it is shown that this need not be the case, e.g., for orientations in which anti-plane yielding occurs by multi-slip, or for special orientations in which the crack tip and the discontinuity planes are perpendicular to the activated slip plane.

54 citations


Journal ArticleDOI
TL;DR: In this article, an upper mantle velocity model was constructed using synthetic seismograms to model amplitudes, and additional constraints can be placed on the derived velocity profile using geometric raytracing techniques.

52 citations



Journal ArticleDOI
TL;DR: In this article, a new formulation of the direct boundary element method is presented for modelling structural discontinuities, such as geological joints and faults, in heterogeneous rock, where the rock surrounding a discotinuity is assumed to be linear elastic and, for the purpose of modelling, is divided into regions of homogeneous material, with adjacent regions separated by interfaces.

01 Mar 1985
TL;DR: In this paper, the authors proposed a linear elastic model to explain the attenuation of compressional and polarized shear wave in a single set of assumptions, where a joint or fracture represents a displacement discontinuity across which average stresses in seismic waves are continuous but displacements are not.
Abstract: This paper discusses a new model in which attenuation as well as group velocity changes are explained by a single set of assumptions. The basis of this model is that a joint or fracture represents a displacement discontinuity across which average stresses in seismic waves are continuous but displacements are not. The model is linear elastic so that all material properties are real valued. It is applicable to cases in which the fractures are large in extent but small in thickness compared to the wavelength of the seismic waves. Laboratory experiments were performed in which a single fracture was represented by an interface between two steel cylinders. Measured attenuation of compressional (P) and polarized shear (S) waves was compared with model predictions.


Journal ArticleDOI
TL;DR: In this paper, a new instability in rotating shallow water in which the rotation velocity has a discontinuity, in a regime where the flow velocity exceeds the characteristics velocity of the waves, has been found experimentally.


Journal ArticleDOI
TL;DR: Stress wave propagation in a long bone with a progressively increasing defect in the bony cortex, simulating a healing fracture, was studied by recording the outputs of bonded semiconductor strain gages, proximal and distal to the defect.

Patent
29 Oct 1985
TL;DR: In this paper, a series of independent parallel pairs of light emitting and detecting diodes for a linear pixel array, which is laterally positioned over an edge-like discontinuity in a workpiece to be scanned, is disclosed.
Abstract: A series of independent parallel pairs of light emitting and detecting diodes for a linear pixel array, which is laterally positioned over an edge-like discontinuity in a workpiece to be scanned, is disclosed These independent pairs of light emitters and detectors sense along intersecting pairs of separate optical axes A discontinuity, such as an edge in the sensed workpiece, reflects a detectable difference in the amount of light from that discontinuity in comparison to the amount of light that is reflected on either side of the discontinuity A sequentially sychronized clamping and sampling circuit detects that difference as an electrical signal which is recovered by circuitry that exhibits an improved signal-to-noise capability for the system

Journal ArticleDOI
TL;DR: In this article, the angle of friction at the interface (or the skin friction) between cohesionless soil and another material is considered theoretically, and it is shown that the interface friction is upper-bounded by two different values.



01 Apr 1985
TL;DR: In this paper, geotechnical descriptors for rock and rock mass are suggested for use in the field that can be readily understood by geotehnical engineers and contractors, such as tunnel support.
Abstract: : Geotechnical descriptors for rock and rock mass are suggested for use in the field that can be readily understood by geotechnical engineers and contractors. Geotechnical applications include tunnel support. slope and foundation stability, and rock excavation. The descriptors are rock type, strength, discontinuity characterization, weathering, rock quality designation (RQD), ground-water conditions, and rock density. The rock name or type should be retained in field description but uncommon rock names should be accompanied by a brief definition to enable the user to relate to more common rock types. Rock strength should be described quantitatively by the point load index test. Descriptions of discontinuities should include measurement and classification of aperture and a determination of whether the discontinuity is open or tight; filling thickness and composition; wall asperity or roughness; and orientation of individual discontinuities; sets and systems. Use of stereographic projection and unambiguous azimuthal notation to describe discontinuity orientation is recommended. Bieniawski's classification of rock weathering is recommended. Field recognition and description of seepage and groundwater conditions along discontinuities based on simple observations of the amount of water present and estimates of discharge are recommended to precede and augment the design of more elaborate pore pressure and seepage analysis investigations.

Book ChapterDOI
01 Jan 1985
TL;DR: In this article, the authors suggest that much of the scatter may be associated with a change in failure mode which generates a discontinuity in the S-N curve and that the remaining scatter is a consequence of static strength variations.
Abstract: Traditionally the large scatter encountered during fatigue testing of E-Glass/Epoxy has been accepted as being an inevitable consequence of the fatigue process. Evidence is presented which suggests that much of the scatter may be associated with a change in failure mode which generates a discontinuity in the S—N curve and that the remaining scatter is a consequence of static strength variations.

Patent
François Joet1
03 Apr 1985
TL;DR: In this paper, the authors present a method for selective detection of microscopic defects in a workpiece by detecting the times when such check line meets a discontinuity, and searching for any possible defects in the workpiece intermittently for time intervals defined in reference to said times.
Abstract: For selective detection of microscopic defects in a workpiece to be checked presenting at least one macroscopic discontinuity of known nature, upon relative motion in respect to such workpiece according to a given check line, detecting the times when such check line meets a discontinuity, and searching for any possible defects in the workpiece intermittently for time intervals defined in reference to said times. This applies in particular to inspection of weld seams of welded tubes.

Patent
11 Apr 1985
TL;DR: In this article, a method for ultrasonic testing of bolts for incipient cracks emanating from a wall thickness discontinuity between thinner and thicker parts of the bolt, which includes placing an ultrasound transmitter and receiver in the form of a piezo-electric transducer on the periphery of the thicker part of a bolt with the discontinuity located in the near-field region, radiating longitudinal waves at an angle of 55° to 70° and transversal waves from the transducers in direction toward the bolt discontinuity, was presented.
Abstract: A method for the ultrasonic testing of bolts for incipient cracks emanating from a wall thickness discontinuity between thinner and thicker parts of the bolt, which includes placing an ultrasound transmitter and receiver in the form of a piezo-electric transducer on the periphery of the thicker part of the bolt with the discontinuity located in the near-field region, radiating longitudinal waves at an angle of 55° to 70° and transversal waves at an angle of 25° to 35° from the transducer in direction toward the discontinuity, and comparing the intensity of reflected transversal and longitudinal waves with an echo characteristic obtained from a test body corresponding to the bolt to be tested, having slots formed therein simulating incipient cracks of different depths, and an apparatus for carrying out the method.

Journal ArticleDOI
TL;DR: In this article, the transition metal impurity levels were used to predict the isovalent heterojunction (HJ) band-edge discontinuities for Ga1−xAlxAs/GaAs heterojunctions.
Abstract: Our recent proposal of using the transition metal impurity levels to predict the isovalent heterojunction (HJ) band-edge discontinuities is further discussed. It is shown that for Ga1−xAlxAs/GaAs heterojunctions most of the recent discontinuity data follow within experimental error the prediction of the ΔEcb:ΔEvb= 0.64:0.36 discontinuity ratio derived from the Fe2+ level position in Ga1−xAlxAs compound. Predictions of valence-band discontinuities for the other III–V and II–VI HJ systems are also given.

Patent
11 Dec 1985
TL;DR: In this paper, the authors describe an approach for locating a discontinuity such as a joint or a crack in a metal pipe or conduit from the interior of the pipe, which comprises means in the form of a magnet 2 for inducing a magnetic field in the pipe and a sensor 3 exhibiting the Hall effect.
Abstract: Apparatus for locating a discontinuity such as a joint or crack in a metal pipe or conduit from the interior of the pipe or conduit, comprises means in the form of a magnet 2 for inducing a magnetic field in the pipe or conduit and a sensor 3 exhibiting the Hall effect, whereby any change in electrical output from the sensor 3 owing to a discontinuity in the pipe or conduit can be monitored. The sensor 3 comprises two Hall effect devices the output of one of which is inverted to cancel one induced magnetic pole. The apparatus includes a pre op-amp 4 which is connected to external equipment including a logic circuit to monitor the signal. There may be four such apparatus mounted around a pipe-line pig. The pig may tow a sealing pig.



Journal ArticleDOI
TL;DR: In this paper, a semi-analytical elastoplastic method is proposed for calculating the ultimate roof support pressure, assuming the failed rock surrounding an underground opening to behave as a Coulomb material.