Block Geometry Research Articles

Genesis and deformation of mud injections containing chaotic basalt-limestone-chert associations: Examples from the southwest Japan forearc

Muddy chaotic deposits, now melanges, are common throughout the Shimanto Belt, southwest Japan, a Cretaceous-Neogene forearc extending for more than 1800 km along strike, and also in the older, more northerly, arc-related belts. Many zones within these melanges show features that are consistent with an early, localized genesis as mud injections, seepages, or mud diapirs synchronous with early slope and accretion-related deformation. These have subsequently undergone considerable postlithification deformation. Melanges containing basalt, limestone, and chert associations may have resulted partly from the explosive fragmentation and fluidization of parts of accreted ocean seamounts or ridges as pore fluids escaping from overpressured shales moved along faults and fractures within the basalt-limestone-chert units to form large mud injections. Using field examples from the Shimanto and related belts, we review criteria for recognition of a variety of mud injections in the light of previous work. These criteria include the nature of contacts, the geometry and internal deformation of clasts or blocks, the matrix fabric and orientation of clasts or blocks in the matrix, and anomalous age relations. The incorporation of basalt-limestone-chert associations in some mud injections in southwest Japan is thought to result from the penetration of overpressured, fluidized muds through accreted seamount or ridge lithologies. This generates a variety of textural relations which may be further complicated by subsequent tectonic shearing.

New model of the midcontinent rift in eastern Minnesota and western Wisconsin

The Midcontinent rift contains a central zone of mostly volcanic and associated intrusive rocks. Flanking, and in places overlying, these mafic igneous rocks are clastic sedimentary basins which range in thickness from less than 1.5 km southwest of the west end of Lake Superior to more than 3.0 km near the Minnesota‐Iowa border. New gravity and magnetic modeling of the rift has shown that most of the volcanic and intrusive rocks are contained within a central block, which in Minnesota and Wisconsin extends to a depth of at least 10 to 20 km. The geometry of this central block, which ranges from fairly symmetric to very asymmetric, appears to reflect a change from predominantly a graben to only a half‐graben development. The modeling has also suggested the presence of a major prerift intrusive body along the Minnesota‐Iowa border which could have locally controlled the rift’s development.

Geometrical identification of three-dimensional rock block systems using topological techniques

This paper describes a new approach to the problem of defining geometrically polyhedral rock blocks created by the intersection of planar discontinuous in a rock mass. The approach represents an extension of the combinatorial topology concepts to solid geometry, which, when implemented computationally, results in a procedure for the systematic identification of the spatial arrangement of rock blocks. The principle of simplicial homology is reviewed and a specific application of block geometry analysis is presented. Various formulae are shown to be necessary in the derivation of the block identification algorithm. The simplicity of the procedure makes it very attractive.

Waipoapoa Landslide: A deep-seated complex block slide in Tertiary weak-rock flysch, Southern Hawke's Bay, New Zealand

Abstract The Waipoapoa Landslide (February 1976) in Southern Hawke's Bay is a complex failure in Upper Miocene weak alternating sandstone and mudstone (flysch). The landslide extends over approximately 18 ha and forms a reactivated portion of a larger ancient landslide complex. The Waipoapoa Landslide has a calculated volume of 8.35 × 106 m3. Morphologically the landslide is comprised of a head zone, front face, and debris-flow complex. Rock-mass defects have controlled slide block geometry. The crown escarpment of the head zone has propagated on nearly vertical intersecting fractures (joints and faults). The intersecting subhorizontal basal shear surface is coincident with bedding contact(s) in an alternating succession of friable porous sandstone and weakly consolidated slake-prone mudstone. Bedding attitude is inclined into the slope, with dips ranging up to 13°. Block movement has occurred against dip direction and has imparted a back-tilted geometry to the head zone depression. A multiple basal shear surface, and basal shear-gouge zone are inferred. The front face is postulated to have bulged outward during the main movement phase and successively collapsed, generating large, rapidly moving debris flows with an estimated volume of 1.75 × 106 m3. These flows stretch is excess of 900 m downvalley from the landslide toe. Failure mechanisms included both sliding and flowage. The failure involves several large blocks and is of multiple block geometry. Principal factors contributing to failure could have included: the presence of fractures (joints and faults) and other defects (e.g., bedding) along which block movement was facilitated; rapid ground-water infiltration along open fractures within the rock mass; high pore-water pressures in one or more porous sandstone beds; and the local steep relief.

Ponui Landslide: A deep-seated wedge failure in Tertiary weak-rock flysch, Southern Hawke's Bay, New Zealand

Abstract The Ponui Landslide (September 1976), in Southern Hawke's Bay, is a wedge failure in an Upper Miocene weak-rock alternating sandstone-mudstone and amalgamated sandstone succession. The planimetric area involved with failure covers 25 ha and represents the reactivation and enlargement of a previous landslide. The Ponui Landslide has a calculated volume of approximately 2.5 × 106 m3. Morphologically, the Ponui Landslide consists of a lateral escarpment, exhumed slide surface, translational slide block, and slide debris. Rock-mass defects have controlled the landslide block geometry. The lateral escarpment has been propagated on nearly vertical intersecting fractures (joints and faults). The slide surface is coincident with bedding in an alternating succession of friable, porous sandstone and weak, slake-prone mudstone. Slide-plane dip is variable, ranging from 10° to 36° and this intersects the escarpment fractures, so isolating the rock wedge. The slide debris is comprised predominantly of silty sand. The rupture surface propagated on a thin montmorillonitic clay gouge zone parallel to bedding. The gouge represents atectonically formed shear zone. Block movement occurred subparallel to strike. The partially disintegrated slide block dammed Ponui Stream, creating a lake with maximum depth of 35 m, and a total calculated storage capacity of over 2.89 × 106 m3. The principal failure mechanism was sliding, involving essentially one large wedge-shaped block. Rapid movement and disintegration quickly reduced much of this block to debris. Other factors contributing to failure include: (1) high rainfall over a prolonged period prior to failure; (2) presumed high ground-water levels with excessive pore-water pressures generated within the porous, fractured sandstones resting on impervious mudstones; and (3) reactivation and enlargement of an existing failure which occurred during the 1931 Napier Earthquake.

Finite size effects in critical dynamics and the renormalization group

Systems representable as a time-dependent Ginzburg-Landau model with nonconserved order parameter are considered in a block (V=L d) geometry with periodic boundary conditions, both for space dimensionalitiesd≧4 andd=4−e. A systematic approach for studying finite size effects on dynamic critical behavior is developed. The method consists in constructing an effective reduced dynamics for the lowest-energy (q=0) mode by integrating out the remaining degrees of freedom, and generalizes recent analytic approaches for studying static finite size effects to dynamics. Above four dimensions, the coupling to the other (q≠0) modes is irrelevant and the probability densityP(Φ,t) for the normalized order parameterΦ=∫dd xϕ(x,t)/V satisfies a Fokker-Planck equation. The dynamics is equivalently described by the Langevin equation for a particle moving in a |Φ|4 potential or by a supersymmetric quantum mechanical Hamiltonian. Dynamic finite size scaling is found to be broken, e.g. the order parameter relaxation rate varies at the bulk critical temperatureT c,∞ as ωυ(T c,∞ L)∼L −d/2 asL→∞. By contrast, ford<4, the coupling to the other (q≠0) modes cannot be ignored and dynamic finite size scaling is valid. The asymptotic behavior of correlation and response functions can be studied within the framework of an expansion in powers of ɛ1/2. The scaling function associated with ωυ is computed to one-loop order. Finally, the many component (n→∞) limit is briefly considered.

Strain softening induced ductile flow in the Särv thrust sheet, Scandinavian Caledonides

The external zone of the Scandinavian Caledonides is characterized by thrust sheets composed of sedimentary rocks derived from the continent Baltica. The Särv thrust sheet is unique amongst them because the 4.5–6 km thick, flat-lying Tossåsfjället Group clastics were intruded by a sub-vertical tholeiitic dike swarm prior to thrusting. The Särv thrust sheet is a large horse (100 km long and 80 km wide) with a classical ramp-flat geometry. The original intrusive relationships of the dikes are preserved throughout most of the thrust sheet and deformation is concentrated at the base in a mylonite zone several tens of meters thick. In this zone, meter-thick dikes rotate into parallelism with the basal thrust and concordant mylonites of both lithologies are intercalated on a centimeter to millimeter scale. The overall rigid block geometry of the Särv thrust sheet, and the intense strain gradient recorded by the rotation of the dike swarm and the concurrent development of mylonites in the thrust zone, suggest that thrust emplacement took place by ductile yield and on-going pseudoplastic flow. Continual strain softening localized ductile flow in this zone by means of grain-size reduction, reaction-enhanced ductility and grain-boundary sliding — processes inferred from the microstructures.

Block-geometry functions characterizing transport in densely fissured media

Abstract The equations describing transport in fissured media, where transport in the matrix blocks is diffusive, are reduced to the standard form of a differential equation for the fissure phase. A dimensionless function is used to characterize the block geometry. Several such block-geometry functions are presented for simple shapes and an empirical generalization is suggested after considering their common properties. Two examples are provided to illustrate possible applications of the results.

A Practical Method for Modeling Fluid and Heat Flow in Fractured Porous Media

AbstractA multiple interacting continua (MINC) method is presented, which is applicable for numerical simulation of heat and multiphase fluid flow in multidimensional, fractured porous media. This method is a generalization of the double-porosity concept. The partitioning of the flow domain into computational volume elements is based on. the criterion of approximate thermodynamic equilibrium at all times within each element. The thermodynamic conditions in the rock matrix are assumed to be controlled primarily by the distance from the fractures, which leads to the use of nested gridblocks. The MINC concept is implemented through the integral finite difference (IFD) method. No analytical approximations are made for the coupling between the fracture and matrix continua. Instead, the transient flow of fluid and heat between matrix and fractures is treated by a numerical method. The geometric parameters needed in a simulation are preprocessed from a specification of fracture spacings and apertures and the geometry of the matrix blocks.The numerical implementation of the MINC method is verified by comparison with the analytical solution of Warren and Root. Illustrative applications are given for several geothermal reservoir engineering problems.

Wind as an influential factor in the orientation of the orthogonal street grid

According to contemporary accounts health and hygiene were important considerations in the planning of ancient orthogonally streeted cities and inevitably the wind and the sun played a not inconsiderable role in influencing the overall and orientation of such cities. Opposing views, held by theorists of the time, as to the benefits of wind at an angle or parallel to the orthogonal streets provide the starting point for this research. The paper deals, in the main, with model investigations into the effects of directionally variable winds on a range of orthogonally gridded block and street arrangements for which air velocity ratios have been established by comparing averaged velocities along streets in the direction of both grid axes. Block geometry is seen to hava an important effect on air speeds producing large differences with the larger block ratios.

Resistance to heat-flow of built-up sections by means of the heat-flow-meter test method

The high sophistication and cost of erecting a Guarded-Hot-Box test system (for investigating thermal performance of built-up sections) prevents its introduction into many research laboratories. The possibility of applying the simpler Heat-Flow-Meter test method without lowering accuracy to an unaccepted level was thus pursued: A system was erected and 18 hollow concrete-block test walls were tested, within a period of one year. The paper describes the system and analyses the test results. It is shown that the present measurements are accurate within ±13,1%, ±3,1% of which stem from the system itself and ±10% from the reference plate's data, (thus causing a maximum possible consistant shift of all the results by +10% or −10%). Ranges of the resistances are also calculated according to the properties of materials and geometry of blocks. The calculation results indicate that, assuming a possible shift of +10% of the test results, the ranges of calculated and tested values virtually coincide. This leads to the conclusion that the use of a Heat-Flow-Meter system, for the measurement of resistance to heat flow of built-up sections, is valid for engineering applications.

The unification of language understanding and problem solving

We are interested in the role that "common-sense knowledge" plays in our ability to understand natural language. Because problemsolving systems have similar knowledge requirements, we are studying the relation between language comprehension on one hand, and problem-solving systems, including much of what goes under the heading of "knowledge engineering", on the other. The current focus of our research therefore is a system that can function in several areas. Some of these will be typical of the language comprehension literature ("stories" about stereotypic situations) while others will involve problem-solving (the blocks world, geometry, and inventory control). This system is based upon a unified set of programs for deductive information retrieval, syntactic parsing, and "low-level" problem solving, as well as a single "frame" representation[1].

Vector stability analysis of an arbitrary polyhedral rock block with any number of free faces

A computational is derived to analyse the stability of a single three-dimensional rock block. It is assumed that the block is rigid and that it is located in an otherwise fixed body of rock and bounded by a combination of flat discontinuities and excavation surfaces. In common with most other solutions for three-dimensional blocks, possible block movements are assumed to be limited to translation only, and rotation is excluded. The block geometries that can be handled by the new procedure are more complex and realistic than those in existing solutions. To start with, the block can be an arbitrary polyhedron with various re-entrant surface features, such as notches and cavities. In addition, any number of its faces may be free and exposed at excavation surfaces. The computational procedure is based on a vector analysis of the block's stability. Part of the computation tests the geometrical configuration of the fixed faces initially in contact with the block to find whether they permit it to move. If so, the procedure can determine the nature and direction of the attempted movement and can usually calculate a factor of safety indicating the likelihood that such movement will be prevented by friction. A method is also outlined for calculating areas of block faces, together with the block's volume and centre of mass. These quantities are relevant to a few of the parameters in the stability analysis.

The use of inclined hemisphere projection methods for the determination of kinematic feasibility, slide direction and volume of rock blocks

The paper explains the use of inclined hemisphere projection methods which allow the assessment of kinematic feasibility, plane(s) of sliding, slide direction and maximum volume of polyhedral blocks defined by the mutual intersection of planar discontinuities and a rock excavation face of any orientation. The methods, which rely on the construction of an inclined hemisphere projection whose plane of projection coincides with the plane of the rock face, are introduced by means of examples that demonstrate the analysis of tetrahedral blocks at planar faces. Subsequent examples deal with pentahedral and polyhedral blocks at bi-planar and curved excavation faces. The methods described can be used prior to, or during, excavation to identify potentially unstable block geometries that merit detailed stability analysis.

Estimating the block size of an ore body

1. The quantitative characteristics of the block size, found by processing measurements of the network of surface cracks, must be converted to the actual parameters of the block size; as a rough approximation we can recommend a linear transformation of the dimensions of the form (1), (2). 2. Borehole measurements of jointing in fans of blastholes enables us to obtain detailed and very important information concerning the jointing of the ore body; there is promise in the possibilities of operational monitoring, and in the use of this information to correct the method of charging and the scheme of blastholes when necessary. 3. Gamma-gamma density logging is a very promising method (although insufficiently researched in this application) of investigating the block size of the ore body-zones of deconsolidation, as a rule, correspond to regions of marked damage. A further step is the development of a method of measurement and quantitative interpretation of the GGDL curves interms of the jointing structure of the rock. 4. The geometry of single blocks (dimensions, area, volume, density, and shape) and their statistical aggregates (packing configuration, structural levels of jointing, and distribution of block dimensions) are important characteristics of the rock, and largely govern the effectiveness of a technology in particular conditions.

Temperature Buildup in Bonded Rubber Blocks Due to Hysteresis

Abstract The comparison between theoretical and experimental results of the temperature distribution in bonded cyclindrical rubber blocks due to compressive cyclic loading was largely dependent on the value of Poisson's ratio. It was found that, for thin rubber blocks (D/h&amp;gt;6), the third significant figure in the value of v appreciably altered the temperature distribution, while for thick blocks (D/h&amp;lt;4), the same change in v had much smaller effect on the temperature distribution within the rubber block. The theoretical analysis used in the paper can easily be adapted for blocks of different geometries, and hence the temperature distribution within a desirable limit can be achieved by changing the geometry of the rubber block.

Grand Forks - Modelling a Three-Dimensional Reservoir With Two-Dimensional Reservoir Simulators

Abstract The purpose of this paper is to discuss techniques that can be used to simulatea three-dimensional reservoir using two-dimensional reservoir simulators. Thetechniques were applied in a two-dimensional areal simulation of waterfloodingin the Grand Forks Lower Mannville D Pool to account for gravity segregationand water coning phenomena. A coning correlation was developed for the range of rates expected in the arealmodel using a two-dimensional radial coning model. The coning correlation andpseudo relative permeability curves for modelling vertical segregation wereincorporated into the areal model to match reservoir history and predictwaterflood performance. The predicted water-oil ratios using the coning'correlation appear to be reasonable when compared with the water-oil ratioscalculated using the laboratory relative permeability curves – the usualassumption in areal modelling. It is concluded from this study that it ispossible to generate pseudo relative permeability curves to approximate waterconing in areal simulation of a three-dimensional reservoir. In developingthese curves velocity sensitivity should be evaluated. Introduction NUMERICAL SIMULATION MODELS are currently available to most reservoir engineersfor simulation of oil and gas reservoir performance. In studying a reservoir.where numerical simulation is justified, the engineer must first select theappropriate model. The model selected could vary from a one-dimensionalsingle-phase model to a three-dimensional, fully compositional model. Generally, study costs are directly proportional to the number of dimensionsand phases or components modelled; therefore, in the case of athree-dimensional problem it is desirable to use a two-dimensional simulatorproviding, of course, that three-dimensional performance can be adequatelyapproximated. In simulating three-dimensional performance with two-dimensional areal models, flaw and fluid distribution in the vertical direction and individual wellperformance must be approximated. Several authors(1–3) havesuggested using pseudo relative permeability and pseudo capillary pressurecurves in two-dimensional areal models to approximate flow and fluiddistribution in the vertical direction. However, except for van Poollen etal.(4) who discussed correspondence been model and measuredpressures, none of these investigations were concerned with approximatingindividual well performance in areal models. Modelling individual well performance is perhaps the most difficult problemencountered in two-dimensional areal simulation of a three-dimensional problem.Initial bottom water, slumping or under-running of injected water can result inwater caning, which is difficult to simulate on two-dimensional areal orthree-dimensional models because block geometry does not adequately definesaturation or pressure distribution near the wellbore. Coning behaviour is bestsimulated with two-dimensional radial coning models, which, unfortunately, cannot predict areal conformance. Mrosovsky and Ridings(7) suggested coupling a three-dimensionalmodel and a radial coning model to simulate coning in a field-wide study. Thisapproach would probably be prohibitively expensive for simulation studies withlarge numbers of wells. One could use analytical approximations such as theradial flow equation or correlations proposed by Sobosinsky(8) or Telkov(9) to approximate coning behaviour. However, to model coningthese approximations must be calibrated to actual field performance forreliable results.

Thermal breakdown in chalcogenide glasses

The time-dependent heat balance equation has been solved numerically for a material having the measured low-field conductivity of amorphous As30Te48Ge10Si12. For a 60 μm thick infinite slab, with boundaries held at ambient temperature and a constant electric field applied parallel to the slab faces, the temperature and current distributions remain relatively uniform until a critical field is exceeded. The current then becomes progressively channelled in the region of the central plane and, for a field of 5.9 × 107 V m−1, it increases by two orders of magnitude within 100 psec as the centre temperature rises from 750 to 1000 K. Time-dependent solutions have also been obtained for a cylindrical block geometry, where heat flow is considered simultaneously both parallel and transverse to the axis. For sufficiently large applied potentials a current channel forms with the hottest point initially at the centre of the block. Hot spots, with associated channel constriction, then grow and move out towards the electrodes.

Drag Forces on Baffle Blocks in Hydraulic Jumps

Large bluff-shaped objects (baffle blocks) placed in the jump improve the hydraulic jump performance characteristics. Knowledge of the drag force on the blocks would aid in determining the optimum block geometry. The highly turbulent and nonuniform flow in the jump prevent a theoretical solution to the problem. An experimental technique similar to that employed by aerodynamicists was used to directly measure the drag forces. Block location, height, width, spacing, second-row location, and shape were the geometrical variables investigated. The study was limited to nonsubmerged jumps in wide, rectangular, horizontal channels. A drag force ratio using the free jump, sequent depth pressure force proved more practical for data correlation than a classical drag coefficient. Resultant downstream water depths computed using the measured drag force compared favorably with experimentally measured values. The results enable the designer to calculate the drag force for a wide range of block geometries and jump inlet Froude numbers from 3 to 10.

Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension

Research Article| April 01, 1971 Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension JOHN H STEWART JOHN H STEWART U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN H STEWART U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America Received: 03 Apr 1970 Revision Received: 05 Oct 1970 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1971, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1971) 82 (4): 1019–1044. https://doi.org/10.1130/0016-7606(1971)82[1019:BARSAS]2.0.CO;2 Article history Received: 03 Apr 1970 Revision Received: 05 Oct 1970 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN H STEWART; Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension. GSA Bulletin 1971;; 82 (4): 1019–1044. doi: https://doi.org/10.1130/0016-7606(1971)82[1019:BARSAS]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Basin and Range structure can be interpreted as a system of horsts and grabens produced by the fragmentation of a crustal slab above a plastically extending substratum. According to this view, the extension of the substratum causes the basal part of the slab to be pulled apart along narrow, systematically spaced zones which in turn cause the downdropping of complex horizontal prisms (grabens) in the brittle upper crust. The grabens form valleys at the surface; the intervening areas are horsts, or tilted horsts.Not all geologists have agreed, however, that Basin and Range structure consists of a system of horsts and grabens. Instead, the structure is commonly considered to consist of tilted blocks in which the upslope part of an individual block forms a mountain and the downslope part a valley. Recent detailed studies, including geophysical work, suggest that the horst and graben model may be more generally applicable. Many of the valleys in the Great Basin are bounded on both sides by faults that drop the valley block down; these faults are exposed at the surface or can be inferred from steep gravity gradients indicative of steep faulted subsurface bedrock slopes. Some areas that were thought to represent a typical series of tilted blocks may be a series of highly asymmetrical grabens in which one side of a valley is marked by a master fault and the other side by valleyward tilt. With present knowledge, most, or perhaps all, of the major valleys in the Great Basin can plausibly be considered to be grabens, and most or all of the mountains can be considered to be horsts or tilted horsts.The grabens, and the underlying inferred deep zones of extension that cause them, are systematically distributed in the Great Basin. They are generally north-trending features spaced 15 to 20 mi apart. Locally, the pattern is more complex, and individual grabens divide and trend away from each other at acute or high angles. In a few places, the pattern may even be roughly polygonal. The distribution pattern of the grabens and the related deep zones of extension resemble crack patterns in small-scale tensional systems, and both patterns may be mechanically related. By analogy with the small-scale systems, the areas of generally north-trending and parallel grabens require east-west extension, whereas the areas with a possible polygonal pattern of grabens must extend radially.The geometry of block faulting related to Basin and Range structure requires sizable east-west extension, estimated at about 1.5 mi on the average for each major valley and at about 30 to 60 mi across the entire Great Basin. Most of this extension has taken place in the last 17 m.y., or perhaps even in the last 7 to 11 m.y., indicating a rate of extension in the range of 0.3 to 1.5 cm/yr. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.