Discrete element simulation of rock cutting Rojek, Jerzy; Oñate, Eugenio; Labra, Carlos ...
International journal of rock mechanics and mining sciences (Oxford, England : 1997),
09/2011, Volume:
48, Issue:
6
Journal Article
Peer reviewed
Open access
This paper presents numerical modelling of rock cutting processes. The model consists of a tool–rock system. The rock is modelled using the discrete element method, which is suitable to study ...problems of multiple material fracturing such as those involved in rock cutting. Both 2D and 3D models are considered in this work. The paper presents a brief overview of the theoretical formulation and calibration of the discrete element model by a methodology combining the dimensional analysis with simulation of the unconfined compressive strength (UCS) and indirect tension (Brazilian) tests. The rock cutting process with roadheader picks, which is typical for underground excavation, has been simulated. The results of the 2D and 3D analyses have been compared with one another, and numerical results have been compared with the available experimental data.
► Advanced modelling of a complex engineering problem using the discrete element model. ► Calibration of the discrete element model. ► Successful validation of the numerical model using experimental results of rock cutting.
Owing to the importance of serpentinites for planetary geochemical and geodynamic processes, there has been much work discerning the origins of their parent rocks, including distinguishing between ...serpentinites derived from a subducting plate versus overlying mantle in exhumed subduction complexes. The island of New Caledonia (SW Pacific Ocean) provides a rare window into Cenozoic Pacific subduction processes. The island is unique in exposing both an exceptionally preserved high‐pressure, low‐temperature subduction complex and one of the largest supra‐subduction zone ophiolites in the world. Previous studies disagree on the origin of serpentinites in the subduction complex. In this study, we analyze 23 serpentinites from this complex for whole‐rock major and trace element geochemistry and stable isotope (δD, δ18O) compositions. Our data reveal two distinct groups of serpentinites: Group I samples in the northern portion of the complex are pervasively serpentinized, and exhibit enriched heavy rare earth element (REE) compositions and δ18O values between +6.7‰ and +10.2‰. In contrast, Group II serpentinites in the south preserve relict orthopyroxene and olivine, and show depleted trace element compositions and comparatively lower δ18O values between +5.1‰ and +8.0‰. We interpret Group I serpentinites to derive from downgoing plate mantle, whereas Group II serpentinites derive from overlying mantle wedge, exhibiting remarkable similarity to the REE geochemistry of the structurally overlying New Caledonia ophiolite. Our results establish the subduction complex in New Caledonia as an unusual natural record of the entrainment and exhumation of mantle from both the overlying mantle wedge and the downgoing plate in an oceanic subduction zone.
Plain Language Summary
The hydration of Earth's mantle produces rocks called serpentinites that are important to chemical cycling within the Earth system. This process, a form of metamorphism, occurs in several types of tectonic settings on Earth. Serpentinites formed in these different settings are imparted with unique geochemical “fingerprints” due to different types of fluids and varied compositions of the original mantle material. In metamorphic complexes that preserve remnants of subduction zones, serpentinites can offer clues to the original tectonic setting and subsequent mechanics of subduction. We analyze stable isotope and whole‐rock compositions to determine the origin of the mantle that produced serpentinites found in the metamorphic complex preserved in New Caledonia (SW Pacific). We discover two distinct groups of serpentinites: one group in the northern portion of the complex likely formed on the ocean floor prior to subduction, and experienced high degrees of fluid alteration as it was metamorphosed. In contrast, a second group of serpentinites in the southern portion of the complex resembles material from the mantle overlying the subducting plate and is less altered. This locality represents an uncommon example, globally, where material from the overlying mantle was entrained and then preserved at the surface in an exhumed subduction complex.
Key Points
Two compositionally distinct types of serpentinites are identified in the New Caledonia subduction complex
Some serpentinites derive from the subducting plate, others from the overlying mantle wedge
New Caledonia preserves evidence for incorporation and exhumation of mantle hangingwall via the subduction channel
Constraining the source, genesis, and evolution of Archaean felsic crust is key to understanding the growth and stabilization of cratons. The Akia Terrane, part of the North Atlantic Craton, West ...Greenland, is comprised of Meso-to-Neoarchaean orthogneiss, with associated supracrustal rocks. We report zircon U–Pb and Lu–Hf isotope data, and whole-rock geochemistry, from samples of gneiss and supracrustals from the northern Akia Terrane, including from the Finnefjeld Orthogneiss Complex, which has recently been interpreted as an impact structure. Isotope data record two major episodes of continental crust production at ca. 3.2 and 3.0 Ga. Minor ca. 2.7 and 2.5 Ga magmatic events have more evolved εHf, interpreted as reworking of existing crust perhaps linked to terrane assembly. Felsic rocks from the Finnefjeld Orthogneiss Complex were derived from the same source at the same time as the surrounding tonalites, but from shallower melting, requiring any bolide-driven melting event to have occurred almost simultaneously alongside the production of the surrounding crust. A simpler alternative has the Finnefjeld Complex and surrounding tonalite representing the coeval genesis of evolved crust over a substantial lithospheric depth. Hafnium isotope data from the two major Mesoarchaean crust-forming episodes record a contribution from older mafic Eoarchaean crust. Invoking the involvement of an Eoarchaean root in the growth of younger Mesoarchaean crust puts important constraints on geodynamic models of the formation of the discrete terranes that ultimately assembled to form Earth’s cratons.
Brian Eno Albiez, Sean; Pattie, David
2016, 2016-08-11
eBook
On the back of his published diary Brian Eno describes himself variously as: a mammal, a father, an artist, a celebrity, a pragmatist, a computer-user, an interviewee, and a 'drifting clarifier'. To ...this list we might add rock star (on the first two Roxy Music albums); the creator of lastingly influential music (Another Green World; Music for Airports); a trusted producer (for Talking Heads, U2, Coldplay and a host of other artists); the maker of large-scale video and installation artworks; a maker of apps and interactive software; and so on. He is one of the most feted and influential musical figures of the past forty years, even though he has described himself on more than one occasion as a non-musician. This volume examines Eno's work as a musician, as a theoretician, as a collaborator, and as a producer. Brian Eno is one of the most influential figures in popular music; an updated examination of his work on this scale is long overdue. - See more at: http://www.bloomsbury.com/uk/brian-eno-9781441129123/#sthash.CmHDQ6Xy.dpuf
During underground mining, rock deformation may be time-dependent and is reflected in rheological behavior. These changes may be also accelerated by dynamic disturbances, such as rock blasting, which ...can trigger mining-induced hazards such as rockburst and a falling roof. A combined double-rock sample was analyzed to clarify the rockburst mechanism resulting from interaction between roof and pillar. In this work, a double-rock sample was subjected to a combined creep and dynamic loading condition. Based on the results, an ideal mechanical model was developed to describe the interaction between double rock samples loaded in series to simulate interaction between the pillar and roof. To test the model, a double-rock sample composed of granite and sandstone was loaded in series under creep and dynamic loading and the effect of dynamic disturbance on the creep process was quantified. Under the same creep stress, a higher impact dynamic disturbance resulted in shorter failure time. Under the same dynamic disturbance, the specimen failed faster with increased strain energy of rebound of the granite sample under increasing creep stress. The energy dissipation rate and energy transfer efficiency are defined to quantify the energy dissipation of double-rock sample and energy transfer between strong and weak sample. Based on the quantification of energy transfer efficient, it confirms that the ratio of stiffness of the double-rock sample should be a indicator for the energy transfer between strong and weak samples. The granite sample had higher uniaxial compressive strength, so it did not fail during the loading process. For the plaster-granite sample, the granite released most energy to accelerate the unstable failure of plaster. The granite-granite sample failed simultaneously and released most strain energy violently. The results can provide a reference to evaluate the delayed rockburst of rock subjected to creep stress.
Drop the record needle on any vinyl album in your collection, then read the first pages of that novel you've been meaning to pick up—the reverberations between them will be impossible to miss. Since ...Dylan went electric, listening to rock 'n' roll has often been a surprisingly literary experience, and contemporary literature is curiously attuned to the history and beat of popular music. In The Ink in the Grooves, Florence Dore brings together a remarkable array of acclaimed novelists, musicians, and music writers to explore the provocatively creative relationship between musical and literary inspiration: the vitality that writers draw from a three-minute blast of guitars and the poetic insights that musicians find in literary works from Shakespeare to Southern Gothic. Together, the essays and interviews in The Ink in the Groove s provide a backstage pass to the creative processes behind some of the most exciting and influential albums and novels of our time. Contributors: Laura Cantrell, Michael Chabon, Roddy Doyle, Bob Dylan, Steve Earle, William Ferris, Dom Flemons, Rhiannon Giddens, Dave Grohl, Peter Guralnick, Amy Helm, Randall Kenan, Jonathan Lethem, Greil Marcus, Rick Moody, Lorrie Moore, the John Prine band (Dave Jacques, Fats Kaplin, Pat McLaughlin, Jason Wilber), Dana Spiotta, John Jeremiah Sullivan, Richard Thompson, Scott Timberg, Daniel Wallace, Colson Whitehead, Lucinda Williams, Warren Zanes.
In Remember Little Rock Erin Krutko Devlin explores public memories surrounding the iconic Arkansas school desegregation crisis of 1957 and shows how these memories were vigorously contested and ...sometimes deployed against the cause. Delving into a wide variety of sources, from memoirs to televised docudramas, commemoration ceremonies, and the creation of Little Rock High museums, Devlin reveals how many white moderates proclaimed Little Rock a victory for civil rights and educational equality even as segregation persisted. At the same time, African American activists, students, and their families asserted their own stories in the ongoing fight for racial justice.
Devlin also demonstrates that public memory directly bears on law and policy. She argues that the triumphal narrative of civil rights has been used to stall school desegregation, support tokenism, and to roll back federal court oversight of school desegregation, voter registration, and efforts to promote diversity in public institutions. Remember Little Rock examines the chasm between the rhetoric of the "post--civil rights" era and the reality of enduring racial inequality.
Tectonic interpretations of arc remnants in the Himalayan orogen remain uncertain, despite their important implications for the overall convergence history between India and Eurasia. Provenance ...results from deep‐water volcaniclastic rocks of the Indus Suture Zone in Ladakh provide new constraints on the Mesozoic tectonic evolution of the Dras and Kohistan‐Ladakh arcs. Detrital zircon (DZ) U‐Pb ages and whole‐rock geochemistry of the fault‐bounded Upper Cretaceous Nindam and Paleocene Jurutze formations present age patterns and compositions that are consistent with those of the Dras and Kohistan‐Ladakh arcs, respectively. The combination of DZs of the Nindam and Jurutze formations with the igneous zircons of the Dras and Kohistan‐Ladakh arcs shows similar age distributions that support a Late Jurassic to Paleocene tectonic connection between all these units. We argue that the secular trends in geochemical composition of DZs and volcaniclastic material are consistent with the magmatic evolution of one convergent margin, which shifted from a primitive to a mature stage during the Late Cretaceous. The recognition of a single Dras‐Kohistan‐Ladakh arc sets the stage for reevaluating competing scenarios of the Mesozoic evolution of the India–Eurasia convergent system. We find that the most likely scenario is that of a Jurassic arc formed above a south‐dipping intraoceanic subduction zone and accreted to Eurasia during the Early Cretaceous, after which it evolved above a north‐dipping subduction zone.
Plain Language Summary
The Himalayan orogen is the result of the collision between India and Eurasia and the closure of the intervening Neotethys Ocean. The suture zone between India and Eurasia hosts an incomplete and complex archive of the paleogeography that once existed between them prior to continent‐continent collision. Investigating suture zone rocks may therefore provide valuable information on the building blocks of the orogen and the overall history of the India‐Eurasia convergent system. Disparate remnants exposed in the Indus Suture Zone (Western Himalaya) suggest that volcanic arcs and sedimentary basins were formed above intraoceanic subduction zones, but there is no consensus on their original paleogeography. We discuss new and existing geological data from volcaniclastic rocks related to the Dras and Kohistan‐Ladakh arcs. Our data support the existence of a single Dras‐Kohistan‐Ladakh arc during the Mesozoic and provide additional insights into the complexity of the pre‐collisional convergence between India and Eurasia.
Key Points
Dissimilar ages and compositions of volcaniclastic units in the Indus Suture Zone reveal arc evolution from primitive to mature stages
Detrital zircon U‐Pb ages and geochemistry, and whole‐rock geochemistry support a common origin of the Dras and Kohistan‐Ladakh arcs
The recognition of a single Dras‐Kohistan‐Ladakh arc represents a key constraint in models of India‐Eurasia convergence
Earthquake and Volcano Deformationis the first textbook to present the mechanical models of earthquake and volcanic processes, emphasizing earth-surface deformations that can be compared with ...observations from Global Positioning System (GPS) receivers, Interferometric Radar (InSAR), and borehole strain- and tiltmeters. Paul Segall provides the physical and mathematical fundamentals for the models used to interpret deformation measurements near active faults and volcanic centers.
Segall highlights analytical methods of continuum mechanics applied to problems of active crustal deformation. Topics include elastic dislocation theory in homogeneous and layered half-spaces, crack models of faults and planar intrusions, elastic fields due to pressurized spherical and ellipsoidal magma chambers, time-dependent deformation resulting from faulting in an elastic layer overlying a viscoelastic half-space and related earthquake cycle models, poroelastic effects due to faulting and magma chamber inflation in a fluid-saturated crust, and the effects of gravity on deformation. He also explains changes in the gravitational field due to faulting and magmatic intrusion, effects of irregular surface topography and earth curvature, and modern concepts in rate- and state-dependent fault friction. This textbook presents sample calculations and compares model predictions against field data from seismic and volcanic settings from around the world.
Earthquake and Volcano Deformationrequires working knowledge of stress and strain, and advanced calculus. It is appropriate for advanced undergraduates and graduate students in geophysics, geology, and engineering.
Professors: A supplementary Instructor's Manual is available for this book. It is restricted to teachers using the text in courses. For information on how to obtain a copy, refer to: http://press.princeton.edu/class_use/solutions.html
Rock failure phenomena, such as rockburst, slabbing (or spalling) and zonal disintegration, related to deep underground excavation of hard rocks are frequently reported and pose a great threat to ...deep mining. Currently, the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward. In this study, new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced. Two types of coupled loading modes, i.e. “critical static stress t slight disturbance” and “elastic static stress t impact disturbance”, are proposed, and associated test devices are developed. Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory, and the rockburst mechanism and related criteria are demonstrated. The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold, and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion. Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density. In addition, we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass, which can efficiently and accurately locate the rock failure in hard rock mines. Also, a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.
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