Glide Surfaces Research Articles

Geomechanics substantiation of pillars development parameters in case of combined mining the contiguous steep ore bodies

Purpose. Determining the actual dimensions of the protecting and crown pillars of ore bodies by seismic survey and assessing the possibility of rock mass collapse and fracturing at the lower levels of the Zhairemskoye field. Methods. An integrated approach is used, which involves the analysis of complete ore bodies development during the combined mining. To determine the geological strength index (GSI) and rock mass rating (RMR), the mass structure is studied, as well as the survey is executed of rock fracturing on the contours of mine workings at levels of +288, +240, +192, +144 m. In addition, the physical and mechanical properties of rocks are refined using the RocLab software. Using the numerical modelling of the self-caving process, when mining the protecting and crown pillars, the processed results of numerical modelling are analysed and the possible zones of the mass deformation are assessed based on the Phase2 software. Findings. It has been determined that during the mining of ore bodies 4 and 6, protecting pillars between the quarry and the underground mine, crown pillars between the levels up to the level of +144 m, the rock displacements are possible along glide surfaces. It has been revealed that the haulage workings of levels +240 and +192 m fall into the zone of possible displacements influence, and the rock pillar between ore bodies 4 and 6 will be exposed to inelastic deformations during the mining of crown pillars to the level of +144 m. It has been found that after the crown pillar development between the levels of +240 and +192 m for ore body 6, the rock pillar destructions are possible between ore bodies 4 and 6, since during the modelling, displacements of more than 2 mm are observed. In this case, the destruction processes are possible in the rock pillar upper part. Originality.A geomechanical assessment of the rocks tendency to caving is given and problem areas of stability during the mining of ore bodies 4 and 6 in the Zhairemskoye field are identified. Practical implications. The stable parameters of protecting and crown pillars have been substantiated, which is an important aspect in the design/efficient technology of mining the contiguous ore bodies. Keywords: engineering seismic, ore body, pillar, level, iron, manganese

Characteristics and occurrence of submarine canyon-associated landslides in the middle of the northern continental slope, South China Sea

High-resolution and high-density 2-D multichannel seismic data, combined with high-precision multibeam bathymetric map, are utilized to investigate the characteristics and distribution of submarine landslides in the middle of the northern continental slope, South China Sea. In the region, a series of 19 downslope-extending submarine canyons are developed. The canyons are kilometers apart, and separated by inter-canyon sedimentary ridges. Numerous submarine landslides, bounded by headscarps and basal glide surfaces, are identified on the seismic profiles by their distorted to chaotic reflections. Listric faults and rotational blocks in head areas and compressional folds and inverse faults at the toes of the landslides are possibly developed. Three types of submarine landslides, i.e., creeps, slumps, and landslide complexes, are recognized. These landslides are mostly distributed in the head areas and on the flanks of the canyons. As the most widespread landslides in the region, creeps are usually composed of multiple laterally-coalesced creep bodies, in which the boundaries of singular component creep bodies are difficult to delineate. In addition, a total of 77 landslides are defined, including 61 singular slumps and 16 landslide complexes that consist of two or more component landslides. Statistics show that most landslides are of a small dimension (0.53–18.09 km² in area) and a short runout distance (less than 3.5 km). Regional and local slope gradients and rheological behavior of the displaced materials might play important roles in the generation and distribution of the submarine landslides. A conceptual model for the co-evolution of the canyons and the associated landslides in the study area is presented. In the model it is assumed that the canyons are initiated from gullies created by landslides on steeper sites of the continental slope. The nascent canyons would then experience successive retrogressive landsliding events to extend upslope; at the same time canyon downcutting or incision would steepen the canyon walls to induce more landslides.

Nanocomposite glide surfaces for FRP hydraulic cylinders – Evaluation and test

The use of continuous fibre-reinforced plastics (FRP) can significantly reduce the mass of hydraulic cylinders, such that light-weight actuators are becoming increasingly common especially in mobile applications. Currently, metallic inner liners are used as piston glide surfaces, which are commonly subject to failure-critical stresses due to the different mechanical behaviour of FRP laminate and metal structure. Adapted polymeric nanocomposites offer great potential to counteract these deficits, based on their good wear characteristics and chemical resistance as well as their high fracture strain and layer adhesion strength appropriate for the laminate deformation. Given this background, theoretical and experimental studies are being carried out on a nanoparticle-reinforced epoxy gelcoat, which has been adapted for load and for efficient manufacturing, as a piston glide surface layer under combined tribological, mechanical and media load. To evaluate the theoretical projection of the mechanical and hygrothermal load on the nanocomposite layer, the stresses and deformations are calculated using multi-layer composite theory for thick-walled anisotropic cylinder shells, and are then compared with experimental data.

Submarine mass-transport deposits in the Semantan Formation (Middle-Upper Triassic), central Peninsular Malaysia

Relatively fresh exposures of the Semantan Formation along the East-Coast Highway (Lebuhraya Pantai Timur - Fasa 1) between Karak and Kuantan, central Peninsular Malaysia, have given new insights into the sedimentary processes in the Triassic flysch basin that once separated west and east Malaya. An eastward change from distal to proximal facies between Karak and Maran indicates a west-facing, active continental shelf to slope sedimentation. Outcrops between Karak and Temerloh, east of the Late Triassic-Early Jurassic Bentong-Raub collisional suture, are generally characterized by classical flysch-like, thinly-bedded sandstone-mudstone facies. Further east of Temerloh towards Maran, and nearer to the paleo-shelf and slope, more sandy and thick-bedded turbidite facies occur. A proximal deep- marine facies association in the Semantan Formation is exposed at the Chenor Junction (Exit 821), kilometre 139 along the highway. South- and north-facing cuts on either sides of the highway reveal large gravity-slide blocks (megaclasts), slumps, debris flow deposits, and associated syn-sedimentary thrust faults and glide surfaces. These features are strongly indicative of large-scale submarine mass-transport processes on the palaeo-slope of the Triassic active margin. The Chenor mass-transport complex is made up of zones of incoherent slump deposits intercalated with well-bedded turbidite/debrite facies. In the lower part of the succession, there are megaclasts of sandstone-mudstone facies, measuring several metres in size, encased in a plastically deformed silty matrix. The megaclasts are highly deformed internally by numerous meso- scale normal faults, probably due to gravitationally-induced extension. Along with other smaller sandstone blocks, these megaclasts are interpreted as slide blocks due to slope failure up-dip. There are other gravity-induced structural features such as rotational slumps, glide surfaces, thrust faults and associated soft-sediment folds. The slump folds and thrusts show vergence to the west, as opposed to the generally eastward tectonic vergence. A few of the well-stratified units show strongly inclined stratal surfaces which may be attributed to lateral accretion of turbidite fan lobes. Several sets of these inclined surfaces are bounded by erosional surfaces which could have resulted from different episodes of turbidity flow. The association of incoherent mass-flow units with the more well-stratified deposits reflects the close spatial and temporal relationship between submarine mass-transport events and turbidity flows on the Triassic active slope and basin plain.

On the geometric origin of Orowan-type kinematic relations and the Schmid yield criterion

It is shown that the Orowan-type kinematic relations as well as the Schmid yield criterion can be derived basing oneself on a formula defining the mean curvature of glide surfaces for a principal congruence of edge dislocation lines accompanied with a particular distribution of secondary point defects. Moreover, it appears that this mean curvature has the physical meaning of a mesoscopic material parameter defining a relation between the evolution of the dislocation state and plastic deformation. It is pointed out that the existence of Orowan-type relations puts kinematic constraints, dependent on the isometry group of glide surfaces, on the dislocation density tensor.

Kinematics of edge dislocations. I. Involutive distributions of local slip planes

The geometry of continuous distributions of dislocations and secondary point defects created by these distributions is considered. Particularly, the dependence of a distribution of dislocations on the existence of secondary point defects is modeled by treating dislocations as those located in a time-dependent Riemannian material space describing, in a continuous limit, the influence of these point defects on metric properties of a crystal structure. The notions of local glide systems and involutive distributions of local slip planes are introduced in order to describe, in terms of differential geometry, some aspects of the kinematics of the motion of edge dislocations. The analysis leads, among others, to the definition of a class of distributions of dislocations with a distinguished involutive distribution of local slip planes and such that a formula of mesoscale character describing the influence of edge dislocations on the mean curvature of glide surfaces is valid.

On the isotropy of continuized dislocated crystals. I. The isotropic lattice distortion

The geometrical theory of continuous distributions of dislocations traditionally neglects the dependence of a distribution of dislocations on the existence of point defects created by this distribution (e.g., due to intersections of dislocation lines). In this paper the influence of such point defects on metric properties of the continuized dislocated Bravais crystalline structure is assumed to be isotropic. The influence of the point defects on the distribution of dislocations is then modeled by treating dislocations as those located in a conformally flat space. This approach leads (among others) to new results concerning the geometry of glide surfaces.

The system of extensional structures developed in the late Yanshanian orogeny in the west of Shandong Province, China

The system of extensional structures in the west of Shandong Province is located on the east margin of the China continental block and on the west side of the Tangcheng-Lujiang fault. Complex crustal movements occurred in the region after the Late Triassic. The system of extensional structures is composed of a linked system of faults, formed under biaxial horizontal extensions after the Yanshanian orogenic contraction. The structure consists of three groups of faults: (1) listric normal faults with NW-SE, approximately E-W and approximately N-S trends; (2) transfer faults that are perpendicular to the normal faults; gently dipping detachments in several layers. The NW-SE-trending Late Jurassic and Early Cretaceous basins have an extension of about 11–16 km (about 6.7%). The Eogene basins have NW-SE and E-W trends, and an extension of about 13–19 km (about 8%). Adding the extensional value of the top of the Archaean metamorphic basement, the total N-S extension is about 25–30 km (about 14%). The total extension of N-S-trending grabens formed during the Late Eogene is about 9.8 km (about 6.6%). The amount of extension in this system was not large enough to produce a typical metamorphic core complex. The Taishan-Lushan-Yishan mountains are uplifted bodies of Precambrian basement which have approximately E-W trends and which were formed by N-S extension. Similarly, the Nishan mountain is an uplifted body by E-W extension. These structures represent a late-orogenic extensional system, characterised by multiple glide surfaces and by faults with different orientations causing extension in all horizontal directions.

Structural analysis of the central and southwestern Sudbury Structure, Southern Province, Canadian Shield

The Sudbury Structure (SS) is an unusual crater structure which acquired its present oval surface shape during northwest-directed ductile thrusting. Lower amphibolite-facies metamorphism accompanied the thrusting which generated a major reverse shear zone. At least 50 km long, the South Range shear zone (SRSZ) transects the South Range of the Sudbury Structure and exhumes a low level of the Sudbury Igneous Complex (SIC). Assuming heterogeneous simple shear in the northwest–southeast vertical plane on northeasterly striking glide surfaces, minimal estimates of net displacement across the SRSZ exceed 8 km. This displacement magnitude and the map pattern of the SIC require the southwest closure of the SS to be steeply plunging, in accord with a hypothetical funnel shape of the SIC. The rocks of the metasedimentary core of the SS are deformed into a family of second-order buckle folds, the tangent surface of which forms an upright open flexure within the first-order structure of the Sudbury synclinorium. The original orientation and bulk rotation of contacts in the SIC are unknown, so its participation in large-scale folding remains uncertain.

Prismatic dislocation arrays produced by single glide

Abstract Slip lines on opposite faces of a crystal deformed in single glide do not match in detail because the glide surfaces are never perfectly flat. The dislocation distribution produced by slip on an imperfect glide surface is modelled in terms of arrays of prismatic primary dislocations, associated with secondary slip. Such arrays can be produced by cross-slip. The model has certain features which match those observed in crystals which work harden in three stages.

Permian and Triassic rocks near Quinn River Crossing, Humboldt County, Nevada

Permian and Triassic rocks near Quinn River Crossing, Humboldt County, Nevada, consist of four structural blocks: (1) a Lower Permian volcanic block; (2) a Permian(?) chert-arenite block; (3) a Lower Permian limestone block; and (4) a Permian and Triassic block. The contacts between the Permian volcanic block and the others are interpreted as thrust faults or glide surfaces. None of these rocks are metamorphosed, in contrast to those of the surrounding mountain ranges. Each of the blocks is lithically similar in some respects to rocks of the Osgood Mountains area 80 km to the southeast. The fusulinid and brachiopod faunas of two of the blocks display affinities to those of the McCloud Limestone of northern California and the Coyote Butte Limestone of central Oregon, and the fauna of another block has elements in common with autochthonous rocks of eastern Nevada and Utah. All four blocks probably are allochthonous with respect to the rocks exposed in the surrounding mountain ranges, but their points of origin remain obscure. The rocks at Quinn River Crossing provide a link among the Permian rocks of north-central Nevada, northern California, and central Oregon and a possible key to their original relations, but more comparative data are needed.

The movement of volterra disclinations and the associated mechanical forces

Abstract An analysis is made of conservative and non-conservative movement of Volterra disclinations and the associated mechanical forces. It is shown that both disclination lines and their axes can experience a force under the action of an applied stress. A general equation is derived for the force on a disclination loop and its axis. The condition for conservative movement is derived. Examples illustrating these principles are given. Glide surfaces for disclination loops are defined. The motion is conservative on a surface generated by rotating the disclination line around its axis, and on a plane normal to the axis. It is shown how a twist loop can be converted to a wedge loop and, vice versa, conservatively.

Subsidence related to underground nuclear explosions, Nevada Test Site

abstract The U. S. Geological Survey is investigating the mechanism of collapse of nuclear explosion cavities for its value in containment, with the hope of eventually determining those geologic environments most susceptible to early collapse or most adaptable to the incitation of collapse. This is a progress report on a part of these studies. The investigations to date have been confined largely to the subsidence of the ground surface in the desert alluvium of Yucca Flat by collapse of volcanic rocks and (or) alluvium into the large cavities formed by nuclear explosions. The sinks thus formed are as much as 60 m (meters) deep and 250 m in radius; they have forms that are commonly variations of inverted cones or sectors of spheres. The outer half of each sink is an inward slide of slightly disoriented but relatively undisturbed alluvium. The major physical disturbance within the slide mass is by subsidiary spoon-shaped cracks and slide surfaces along which individual blocks have adjusted within the glide mass. Each individual block moves a net distance that is small relative to the total movement of the main slide. The cracks or glide surfaces are assumed to flatten with depth within the slide and to join the major surface of failure at the base of the main slide mass. The spoon-shaped surfaces, where they intersect the top surface of the slide, dip steeply to vertically. In plan they make a pattern of curving, intersecting cracks. The depth of burial of the explosion cavity in alluvium relative to its size affects the profile of the sinks, the height of chimneys for collapses not extending to the surface, and, to an extent, the likelihood that later surface subsidence will occur. A working model of collapse includes: (a) maintenance of the explosion cavity until main collapse occurs; (b) a two-phase collapse taking place in several seconds or several tens of seconds, culminating in surface subsidence if the cavity is sufficiently close to the surface. The first phase of collapse in alluvium, at least, consumes 70-90 per cent of the collapse period; collapse propagates upward at rates of 50-80 ft/sec. The second phase shows faster rates of upward propagation, a lesser degree of particulation of the collapse material, and ends with the drop of a central mass of alluvial material that initiates formation of the sink. The shape, size, and distance of vertical drop of this alluvial plug control the size and form the resulting sink. Acceleration of this mass ranges from 0.35 to 0.8 g.

Continuous distributions of dislocations. V. Twisting under conditions of single glide

The theory of continuous distributions of dislocations is applied to discuss the geometrical features of the twisting of a cylindrical crystal deforming by single glide. It is first assumed that the strains are small, and that the dislocations arrange themselves so as to produce no far-reaching stress, and explicit expressions for the shape changes, lattice rotations and dislocation distribution are derived. The theory is in reasonable agreement with the observations of Whapham & Wilman (1956) when the angle of twist per unit length is not too large. The expression for the shape of the glide surfaces is much simpler than that derived by Whapham & Wilman, who also applied a small strain approximation, but not consistently. It is shown that the consistent reduction of the complicated expression of these authors leads to the simple one of the present theory. Further, the correct shape of the glide surfaces for large strains is also derived using the boundary conditions employed by Whapham & Wilman. This predicts an asymmetry of the type observed in a severely twisted crystal before correction of the observations for macroscopic bending, although the predicted asymmetry is rather too large.

Continuous distributions of dislocations IV. Single glide and plane strain

The theory of the continuously dislocated crystal is applied to discuss the behaviour of a crystal which has deformed by single glide. When the single glide is also in one crystallographic direction only the deformation is two-dimensional, and this situation is treated in detail. The analysis assumes that the dislocations arrange themselves so that they cause no far-reaching stress. In single glide, the lattice lines originally normal to the slip plane are the orthogonal trajectories of a family of surfaces, the glide surfaces. It is shown that these surfaces are developable, and that this imposes additional restrictions on the dislocation density, which are not considered by Nye (1953) and which provide a basis for the classification of the possible states of dislocation. A convenient analytical solution is given of the general equations for single glide when the lattice rotations are everywhere small. The discussion of plane strain begins by treating the lattice deformation. The general equation governing the lattice rotation is given, and the necessary boundary conditions and methods of solution are discussed. The analysis is compared with that of Nye and illustrated by some examples of practical interest. More realistic problems are posed when the boundary conditions specify changes of shape of the specimens. To discuss these the relationship between the lattice, shape and dislocation deformations is considered, and it is shown how all these deformations can be found from the necessary boundary conditions on the shape deformation. The general solution, which is valid for large strains, is applied to a general class of bending problem, and equations relating the geometrical features of the lattice, and of lines scribed on the crystal are derived. The general analysis is illustrated by examples emphasizing certain confusing degeneracies arising in the very symmetrical situation of uniform plane bending (Nye 1953), and revealing the meaning of many valued solutions for the lattice rotation.

The shapes of glide planes in bent zinc crystals

Experiments are described which show that, within the experimental error, the glide surfaces in uniformly bent zinc single crystals intersect the plane of bending in involutes of circles. The observation that “river-patterns” on the cleavage surfaces of zinc crystals often begin along the line of mosaic boundaries formed during the growth of the crystals is also reported.

Some geometrical relations in dislocated crystals

When a single crystal deforms by glide which is unevenly distributed over the glide surfaces the lattice becomes curved. The constant feature of distortion by glide on a single set of planes is that the orthogonal trajectories of the deformed glide planes (the c-axes in hexagonal metals) are straight lines. This leads to the conclusion that in polygonisation experiments on single hexagonal metal crystals the polygon walls are planes, while the glide planes are deformed into cylinders whose sections are the involutes of a single curve. The analysis explains West's observation that the c-axes in bent crystals of corundum are straight lines. For double glide on two orthogonal sets of planes there is a complete analogy between the geometrical properties of the distorted glide planes and those of the “slip-lines” in the mathematical theory of plasticity. More general cases are discussed and formulae are derived connecting the density of dislocations with the lattice curvatures. For a three-dimensional network of dislocations the “state of dislocation” of a region is shown to be specified by a second-rank tensor, which has properties like those of a stress tensor except that it is not symmetrical.