Expansion Of Rock Research Articles

Late Jurassic to Early Cretaceous volcanism of Hong Kong: Insights from the Ping Chau Formation

The vast expanse of Mesozoic igneous rocks in Hong Kong contain important geological records of late Mesozoic magmatic events and tectonic processes from the coastal region of Southeast China. Of these, the Ping Chau Formation in the northwestern New Territories is the youngest known stratum. We perform a detailed study of the volcanic rocks of the Ping Chau Formation utilizing zircon U–Pb dating, with major and trace elements geochemistry. LA-ICP-MS zircon U–Pb data reveal Early Cretaceous age from two volcanic rock samples, with zircon crystallization from magmas at 140.3 ± 0.8 Ma and 139.3 ± 0.9 Ma, respectively. These rocks have high contents of total alkalis (Na2O + K2O = 5.58–9.45 wt.%), high-field-strength elements and light rare earth elements, conspicuous negative Eu anomalies, and depletions in Nb, Ta, Ti, Sr, Ba and P. Using this data, in combination with previous studies on the late Mesozoic volcanic belt in Southeast China, we propose that the volcanic rocks of the Ping Chau Formation probably originated from deep melting of the crust in a back-arc extensional setting induced by the subduction of the paleo-Pacific Plate. This formation represents the final stages of Early Cretaceous volcanic activity in Hong Kong, as associated with large-scale lithospheric extension, thinning and magmatism. Our results provide new information that can be used in evaluating the significance of Early Cretaceous volcanism and tectonics in Southeast China.

Modeling the swelling of shale matrix in unconventional reservoirs

The imbibition of the injection water into shale matrix may result in shale swelling affecting oil recovery from the rock matrix and the transport properties of the fractures. The expansion of rock due to the swelling of shale matrix compresses the pore space in the rock matrix and the surrounding fractures. This reduces fracture and matrix porosity and permeability. The reduction of matrix pore space can reduce the rate of oil recovered from the rock matrix. On the other hand, it also forces the oil out of the matrix pore space increasing oil recovery. However, this effect has not been evaluated and integrated in reservoir modeling.This study presents a coupled fluid flow and geomechanics model for modeling shale swelling to quantitatively investigate the effect of swelling on transport properties of rock matrix and fractures. The main objective is to quantitatively determine the effect of shale swelling on the oil recovery from the rock matrix. A numerical solution is presented to solve the coupled equations simultaneously for the phase pressure, fluid saturation, stress, and strain. We show that the mechanical properties of the rock matrix vary significantly as the result of water imbibition. The reduction of the fracture and matrix permeability and porosity due to swelling is considerable. This results in the reduction of more than 50% of the oil recovered from shale matrix. Hence, shale swelling should be prevented in any water injection operations.

Creep degradation mechanism by water-rock interaction in the red-layer soft rock

Bank slope stability has become a great concern, while the impoundment of Three Gorges reservoir. The bank slope composed of red-layer soft rock has exhibited distinct deformation and failure. Therefore, a typical red-layer soft rock around Three Gorges reservoir area was selected to demonstrate the process of cyclic changes at the reservoir level and immersion-air-dry cyclic action of water-rock inside hydro-fluctuation belt. To meet the objective of this study, a series of creep tests were conducted on the rock specimens at different water-rock interaction stages. The following points were noticed based on the laboratory results: (1) the creep fracture strength and long-term strength of red-layer soft rock degraded significantly during the process of water-rock interaction. For the first three water-rock interaction circulations, the strength of red-layer soft rock degraded quickly and then gradually became stable. (2) During the creep test, the lateral expansion of red-layer soft rock increased significantly regarding to the number of cycles. (3) The creep curve includes three typical stages at failure stress level—primary (damped) stage, secondary (steady-state) stage, and tertiary (nonlinear accelerated) stage. As the number of cycles increased, the percentage of secondary stage diminished gradually. However, the tertiary stage showed a gradual increment, since the plasticity of the specimens was strengthened by water-rock interaction. (4) The shear failure characteristics of the specimens became highly considerable during the process of water-rock interaction, and there have been a gradual increment of shear rupture zone. (5) The SEM results showed that the specimen microstructure changed its state from dense to loose and porous. The findings of this research provide a good basis for long-term stability analysis of bank slope.

Modeling Battery Performance Due to Intercalation Driven Volume Change in Porous Electrodes

A mathematical battery model is presented that incorporates the dimensional and porosity changes in porous electrodes caused by volume changes in the active material during intercalation. Porosity and dimensional changes in an electrode can significantly affect the resistance of the battery during cycling. In addition, volume changes generate stresses in the electrode, which can lead to premature failure of the battery. Here, material conservation equations are coupled with the mechanical properties of porous electrodes to link dimensional and porosity changes to stresses and the resulting resistances that occur during the intercalation processes. The stress-strain relationships used in this model are from previous works, which are used to predict porosity and dimensional changes, and were established by comparing thermal rock expansion and electrode expansion due to intercalation. Several different battery casings are examined and operating curves are predicted based off of standard equilibrium potentials combined with simple kinetics.

Modeling Battery Performance Due to Intercalation Driven Volume Change in Porous Electrodes

In order to accurately predict the behavior of electrochemical devices, it is necessary to develop sophisticated models that take into consideration transport processes, electrochemical phenomena, mechanical stresses, and structural deformations (i.e. strain) on the operation of an electrochemical system. There are many different models in use that can predict the electrochemical performance of these devices under a variety of operating and design conditions. However, many of these models assume a constant porosity and do not take into consideration the effects of a variable porosity on the porous electrode during cycling and what effects that may have on performance. In recent years, electrodes have been developed that show significant volume changes during intercalation and deintercalation, which are unable to be accurately predicted using these constant porosity models. Here, a mathematical battery model is presented that incorporates the dimensional and porosity changes in porous electrodes caused by volume changes in the active material during intercalation (e.g., lithium into carbon or silicon). Porosity and dimensional changes in an electrode can significantly affect the resistance of the battery during cycling. In addition, volume changes generate stresses in the electrode, which can lead to premature failure of the battery. Here, material conservation equations were coupled with the mechanical properties of porous electrodes to link dimensional and porosity changes to stresses and the resulting resistances that occur during the intercalation process. The stress-strain relationships used in this model are from previous works, which are used to predict porosity and dimensional changes, and were established by comparing thermal rock expansion and electrode expansion due to intercalation. Several different cases modeled after new battery electrode technologies are examined and operating curves are predicted based off of standard equilibrium potentials.

Fracture initiation in cavity expansion of rock

Initiation of fracture from a cylindrical opening in blocks of Berea sandstone under plane strain was monitored with a cavity expansion apparatus. Using the particle tracking technique called digital image correlation, a discontinuity in the displacement field near the cavity boundary was identified at 80% of the peak internal pressure, which meant that a process zone developed prior to peak. To investigate the effect of scaling on fracture, a two dimensional bonded particle model was validated, and several specimens sizes with different borehole and tension softening characteristics were tested numerically. It is demonstrated that with increase in specimen size or with increase in borehole size, the peak pressure decreases, and these size effects are governed by both material and structural length scales.

Building ceramics with improved thermal insulation parameters

One of the most important performance characteristics of masonry units is their high thermal insulation. There are many different ways to improve this parameter, however the most popular methods in case of ceramic masonry units are: addition of pore-creating raw materials and application of proper hole pattern. This study was an attempt to improve thermal insulation of ceramics by applying thermal insulation additives. Perlite dust created as a subgrain from expansion of perlite rock was used. Perlite subgrain is not very popular among consumers, that’s why it’s subjected to granulation to obtain coarse grain. The authors presented concept of direct application of perlite dust for the production of building ceramics with improved thermal insulation. Fineness of this additive is asset for molding of ceramic materials from plastic masses. Based on the results it was found that about 70% perlite by volume can be added to obtain material with a coefficient of heat conductivity of 0,37 W/mK. Higher content of this additive in ceramic mass causes deterioration of its rheological properties. Mass loses its plasticity, it tears up and formed green bodies are susceptible to deformation. During sintering perlite takes an active part in compaction process. Higher sintering dynamics is caused by: high content of alkali oxides in perlite and glass nature of perlite. Alkali oxides generate creation of liquid phase which intensifies mass compaction processes. Active role of perlite in sintering process causes good connection of its grains with clay groundwork which is important factor for mechanical parameters of ceramic materials. It was also noted that addition of perlite above 40% by volume of mass effectively neutralized negative effect of efflorescence in ceramic materials.

Determination of volumetric changes at an underground stone mine: a photogrammetry case study

Photogrammetry, as a tool for monitoring underground mine deformation, is an alternative to traditional point measurement devices, and may be capable of accurate measurements in situations where technologies such as laser scanning are unsuited, undesired, or cost-prohibitive. An underground limestone mine in Ohio is used as a test case for monitoring of structurally unstable pillars. Seven pillars were photographed over in a 63day period, punctuated by four visits. Using photogrammetry, point clouds of the mine geometry were obtained and triangulation surfaces were generated to determine volumes of change over time. Pillar spalling in the range of 0.29–4.03m3 of rock on individual rib faces was detected. Isolated incidents of rock expansion prior to failure, and the isolated failure of a weak shale band were also observed. Much of the pillars remained unchanged during the monitoring period, which is indicative of proper alignment in the triangulated surfaces. The photographs of some ribs were of either too poor quality or had insufficient overlap, and were not included. However, photogrammetry was successfully applied to multiple ribs in quantifying the pillar geometry change over time.

Pile groups under deep expansion: a case history

A viaduct in a high-speed railway line experienced severe heave of its central pillars as a result of deep expansion of an anhydrite rock. Bridge pillars were founded on pile groups that experienced vertical heave displacements as well as lateral displacements and rotations. A semi-analytical solution for the response of a pile group under loading and arbitrary located soil expansion was developed, integrating fundamental solutions for the elastic half-space. The procedure was first validated and then applied to explain the recorded behaviour of the pile groups. The deep expansion was identified from independent surface heave and continuous extensometer readings. Group rotations were well predicted. Observed tensile fissures at the cap–pile contact were explained by the calculated forces and moments on the piles.

The effect of caprock permeability on shear stress path at the aquifer–caprock interface during fluid injection

The permeability of the cap rock is one of the most important properties for determining whether an injected fluid can be sequestered as desired. A literature review on many previously conducted investigations shows that the mechanical properties of a clayey cap rock, such as Young’s moduli and Poisson’s ratios, are relatively constrained to a small range of potential values in comparison to the permeability, which can vary greatly by many orders of magnitude. We found that the shear stress on the interface between the aquifer and cap rock results in very different temporal behaviors in response to different cap rock permeability. The largest shear stress changes concentrate on the near well region and remain stationary over a long period of time if the cap rock has very low permeability. The shear stresses increase greatly in the near well region at early times but the largest increases tend to migrate to the far side for semi-pervious or pervious cap rock conditions. Shear stress near the well may experience a reversion at the interface due to the delayed expansion of the cap rock if the cap rock is semi-pervious and more expansive than the aquifer formation. Because of the difficulty in measuring the stresses at depth, these stress changes may only be inferred from in-direct signals, such as induced seismicity. This poses the possibility that we may be able to inversely evaluate whether a cap rock formation is tight (very impermeable), or semi-pervious or even permeable by detecting the temporal and spatial occurrences of seismic swarms on the rock interface associated with fluid injection.

Wall-Rock Structural Controls on the Genesis of the Voisey's Bay Intrusion and its Ni-Cu-Co Magmatic Sulfide Mineralization (Labrador, Canada)

The Voisey’s Bay intrusion of the Mesoproterozoic Nain Plutonic Suite hosts a world-class magmatic Ni-Cu-Co sulfide deposit. Here we document the brittle and ductile structure of gneisses surrounding the intrusion using field data, borehole intersections, and subsurface structural data obtained from acoustic and optical televiewer surveys. We elucidate the role that wall-rock structure played on controlling the geometry of the intrusion and the formation of structural traps that host mineralization. The Voisey’s Bay intrusion consists at first order of two km-scale magma chambers, interpreted to represent an upper and lower chamber of the intrusion, that are connected by a system of dikes. Three types of gneiss, associated with the Paleoproterozoic Torngat orogen, form the wall rocks of the intrusion: Archean orthogneiss, Paleoproterozoic Tasiuyak paragneiss, and Paleoproterozoic enderbitic orthogneiss. Three phases of ductile deformation (D1–D3), predating intrusion emplacement, are recorded in the wall-rock gneisses. D1 produced the dominant S1 fabric, subparallel to original bedding (S) in the Tasiuyak gneiss. D2 shortening caused shallowly plunging, upright to moderately inclined, F2 folds in the enderbitic gneiss, the prototype of which was likely emplaced toward the end of D1. D3 ductile deformation resulted in steeply dipping shear zones, and flat lying to shallowly dipping C3 shear planes. At least two later phases of brittle deformation (D4 and D5) are present. D4 is a preemplacement event characterized by fractures with orientations similar to D3 shear zones and shear planes. D5 faults and joints formed during syn- to postemplacement brittle deformation likely associated with E-W brittle sinistral transtension associated with the Mesoproterozoic Gardar-Voisey’s Bay fault zone. The geometry of the Voisey’s Bay intrusion and its mineralization was controlled by pre- to synemplacement brittle structures and preemplacement ductile structures, which acted as passive wall-rock anisotropies. Mineralization hosted within Tasiuyak gneiss is controlled by the intersection of a dike with S1/S, D3 shear zones and D4 fractures. Where the intrusion occurs within enderbitic gneiss, mineralization locally coincides with shallow fabrics associated with F2 fold closures. The margins of the Voisey’s Bay dikes are controlled by steeply and shallowly dipping D4 fractures. Changes in dike thickness, which control the locations of mineralization, can be explained by thermomechanical erosion of the walls of the dike, which occurs by thermal expansion and contraction of wall rock due to repeated magma pulses, and the mechanical spalling of this wall rock along anisotropies. The strong brittle structural control on emplacement, along with previous geothermobarometry, is consistent with a mid-crustal (9–11 km) depth of emplacement. Lithosphere-scale E-W–trending D5 faults may have acted as conduits for the crustal-scale transport of primitive Voisey’s Bay magmas from their source, rather than an older orogenic suture zone.

Neotectonic uplift of Early Precambrian cratons caused by metamorphism with rock expansion in the earth crust

Neotectonic uplift of Early Precambrian cratons caused by metamorphism with rock expansion in the earth crust

Anomalous surface heave induced by enhanced oil recovery in northern Alberta: InSAR observations and numerical modeling

AbstractRecent interferometric synthetic aperture radar observations over northern Alberta, Canada, show persistent surface heave occurring at rates of 1–4 cm/yr, localized at sites where the steam‐assisted gravity drainage technique is currently used to extract bitumen from the Athabasca oil sands. We find that uplift rates above the horizontal injector wells are strongly correlated with rates of steam injection, even though there is a net fluid loss from the reservoir pore space as oil and water are withdrawn through the production wells. In combination with available steam injection and bitumen production data at four sites, we use reservoir flow models to explain how the thermal and geomechanical effects of steam injection on an oil sand reservoir can generate uplift at the surface. Results of our numerical experiments show that persistent surface heave consistent with observed rates can be driven by stress changes in the reservoir due to porous flow and thermal expansion. We also observe an unexpected localized uplift, of magnitude equal to or greater than the heave above the sites of steaming but located at clusters of wellheads which are outside the region of influence of the steam chambers. We show that this “wellhead” deformation can be explained by thermal expansion of rock near the injector wells.

Exploring the influence of biofilm on short‐term expansion and contraction of supratidal rock: an example from the Mediterranean

ABSTRACTPrevious geomorphological investigations using the traversing micro‐erosion meter (TMEM) have identified daily and hourly contractions and expansions of littoral rock on a range of lithologies. While organic influences on these patterns have been inferred, this has rarely been tested in a controlled way. Here, a TMEM was used to measure micro‐scale (<mm) topographic changes on supratidal limestone of the Massif des Calanques, southern France. Four TMEM monitoring sites (each 64 cm2) were set up in total, two in the Calanque de Morgiou and two in the Presqu'ile de Cassis. On both shores one TMEM bolt site was positioned on bare rock and the other on colonized rock. TMEM data were collected and the surface micro‐topography mapped for each site at two‐hourly intervals from early morning to late evening across one day in mid‐summer.Significant relative expansion and contraction was observed between measurement periods at all four sites, regardless of biofilm colonization (P < 0.001 in all instances), and sometimes between adjacent zones on the rock surface (at a scale of centimetres). Rock with and without biofilm behaved broadly similarly, but the magnitude of topographic change varied: average movement from one interval to the next was 0.03 mm on bare sites and 0.06 mm on biofilm‐colonized sites. As expected, patterns of surface change related largely to insolation, with greatest movement occurring in the morning and evening when thermal gradients were steepest. Interestingly, the presence of a biofilm intensified rock expansion, but delayed surface response to microclimatic variability. We largely attribute this effect to biofilm influences on surface albedo, and hypothesize that episodes of contraction and expansion are superimposed onto longer (annual to decadal) episodes of surface movement and downwearing. Short‐term TMEM studies therefore need to be coupled with longer‐term seasonal and annual measurements to improve understanding of rock surface dynamics. Copyright © 2014 John Wiley & Sons, Ltd.

Experimental study on settlement and punching behavior of full-scale RC and SFRC precast tunnel lining segments

The overall stability of a segmental tunnel lining ring is highly dependent on the structural integrity of its individual precast segments, which provide protection against the surrounding exposure conditions. In this study, the settlement and punching behavior of full-scale conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) precast tunnel lining segments fabricated for a subway tunnel in Canada were investigated. Precast concrete tunnel lining (PCTL) segment specimens were subjected to mid-span load on their intrados faces. Such loading can be induced as a result of vehicular accidents inside the tunnel and/or soil settlement underneath the PCTL segments. Moreover, a punching test was conducted to replicate the expansion of rocks or other geotechnical surrounding conditions above or underneath the tunnel segments. The experimental results showed that the peak load carrying capacity of the RC segments was higher than that of the SFRC segments for both the settlement and punching behavior. However, SFRC segments exhibited higher initial cracking load, more stable post-peak cracking pattern compared to that of the RC segments and significant reduction in crack width. This makes SFRC attractive for the fabrication of segmental tunnel linings where the initial cracking is a governing criterion. Furthermore, it was confirmed that both the tested RC and SFRC PCTL segments satisfied common settlement and punching loads design criteria.

Can livestock grazing maintain landscape diversity and stability in an ecosystem that evolved with wild herbivores?

The livestock industry is converting mountain ecosystems in central Argentina into rocky deserts. However, it helps to conserve plant biodiversity, presumably because the ecosystem has evolved under wild herbivores now locally extinct. We hypothesized that low or moderate livestock stocking rates, instead of the high stocking rates currently used for commercial production, might mimic pre-hispanic herbivore pressures. Thus, the mosaic of physiognomies necessary to maintain landscape diversity and soil integrity could be preserved. To test this hypothesis we tracked physiognomic changes in 200 plots (16 m2 each) under different stocking rates, including livestock exclusion, for five years. Contrary to our expectations, we found that both low and moderate stocking rates failed to maintain landscape diversity. As observed for livestock exclusion, low to moderate stocking rates promote retraction and, finally, elimination of short grazing lawns and their replacement by tall tussock grasslands, or possibly by woody vegetation. In turn, heavy grazing pressure maintains the desired short lawn patches in the landscape, but also promotes a concomitant loss and eventual elimination of woodlands, together with an expansion of bare rock as a consequence of soil erosion. These results indicate that the present mosaic of physiognomic types is difficult to maintain and raise questions about the past stability of the ecosystem. We suggest that during the last 400 years of livestock production in the ecosystem, short lawns have been maintained by means of heavy stocking rates and anthropogenic fires ignited to eliminate tussocks. However, this relative stability of lawns has been attained concomitantly with a progressive loss of soils and woodland area. We also discuss some possible explanations for the maintenance of short lawns before the introduction of livestock, based on main climatic and floristic shifts during the late Holocene.

The volume expansion of rocks by the weathering

The volume expansion of rocks by the weathering

Integrity of Pre-existing Wellbores in Geological Sequestration of CO2 – Assessment Using a Coupled Geomechanics-fluid Flow Model

Abstract Assessment of potential CO 2 and brine leakage from wellbores is central to any consideration of the viability of geological CO 2 sequestration. Depleted oil and gas reservoirs are some of the potential candidates for consideration as sequestration sites. The sequestration sites are expected to cover laterally extensive areas to be of practical interest. Hence there is a high likelihood that such sites will contain many pre-existing abandoned wells. Most existing work on wellbore integrity has focused on field and laboratory studies of chemical reactivity. Very little work has been done on the impacts of mechanical stresses on wellbore performance. This study focuses on the potential enhancement of fluid flow pathways in the near-wellbore environment due to modifications in the geomechanical stress field resulting from the CO 2 injection operations. The majority of the operational scenarios for CO 2 sequestration lead to significant rise in the formation pore pressure. This is expected to lead to an expansion of the reservoir rock and build-up of shear stresses near wellbores where the existence of cement and casing are expected to constrain the expansion. If the stress buildup is large enough, this can lead to failure with attendant permeability enhancement that can potentially provide leakage pathways to shallower aquifers and the surface. In this study, we use a numerical model to simulate key features of a wellbore (casing, annulus and cement) embedded in a system that includes the upper aquifer, caprock, and storage aquifer. We present the sensitivity of damage initiation and propagation to various operational and formation parameters. We consider Mohr-Coulomb shear-failure models; tensile failure is also likely to occur but will require higher stress changes and will be preceded by shear failure. The modeling is performed using the numerical simulator FEHM developed at LANL that models coupled THM processes during multi-phase fluid flow and deformation in fractured porous media. FEHM has been developed extensively under projects on conventional/unconventional energy extraction

Modeling Volume Change due to Intercalation into Porous Electrodes

A mathematical model is presented that predicts the dimensional and porosity changes in a porous electrode caused by volume changes in the active material during intercalation (e.g., lithium into carbon or silicon). Porosity and dimensional changes in an electrode significantly affect the resistance of the battery during cycling. In addition, volume changes generate stresses in the electrode, which can lead to premature failure of the battery. Here, material conservation equations are coupled with the mechanical properties of the porous electrode to derive governing relations that link dimensional and porosity changes to stresses that occur during the intercalation process. The stress-strain relationships used in this model, which are needed to predict porosity and dimensional changes, have been established by examining the similarities between thermal rock expansion (e.g., the exchange of thermal energy with the rock) and electrode expansion due to intercalation.

Writing from ‘the perilous ridge’: Romanticism and the Invention of Rock Climbing

This essay argues that rock climbing had its genesis in the Romantic period and that there was a powerful synergy between the emergent sport and the era’s literature. It was during the Romantic period that clambering on crags, cliffs and ridges started to become an activity undertaken for its own sake and began to provide a subject for literature, developments which I explore in the essay’s first section through an examination of the travel writing of William Bingley and others. In the second section, I argue that the specific embodied experience of rock climbing was integral to the development of a key Romantic trope, visionary power, an issue I consider through readings of two of the period’s greatest first-hand accounts of rock climbing, Wordsworth’s poetic evocation of his scrambling on Yewdale Crags in The Prelude and Coleridge’s epistolary description of his descent of Broad Stand. In the final section of the essay, I investigate how climbing became a feature of some of the era’s most significant as well as best-selling poems and novels, focusing particularly on Walter Scott’s work to show how his writing transformed the image of the climber, shaped the imagining of the nascent sport, and laid the foundation for the remarkable expansion of rock climbing in the second half of the nineteenth century.