设为首页 | 加入收藏
文献检索:
  • The influence of microwave irradiation on rocks for microwaveassistedunderground excavation 免费阅读 下载全文
  • Demand is growing for explosive-free rock breakage systems for civil and mining engineering, and spaceindustry applications. This paper highlights the work being undertaken in the Geomechanics Laboratoryof McGill University to make a real application of microwave-assisted mechanical rock breakage to fullfacetunneling machines and drilling. Comprehensive laboratory tests investigated the effect of microwaveradiation on temperature profiles and strength reduction in hard rocks (norite, granite, and basalt)for a range of exposure times and microwave power levels. The heating rate on the surface of the rockspecimens linearly decreased with distance between the sample and the microwave antenna, regardlessof microwave power level and exposure time. Tensile and uniaxial compressive strengths were reducedwith increasing exposure time and power level. Scanning electron micrographs (SEMs) highlightedfracture development in treated basalt. It was concluded that the microwave power level has a strongpositive influence on the amount of heat damage induced to the rock surface. Numerical simulations ofelectric field intensity and wave propagation conducted with COMSOL Multiphysics software generatedtemperature profiles that were in close agreement with experimental results.
  • The stresse-straine-permeability behaviour of clay rock during damageand recompaction 免费阅读 下载全文
  • Characterisation and understanding of the stresse-straine-permeability behaviour of a clay host rockduring damage and recompaction are essential for prediction of excavation damaged zone and forassessment of its impact on the repository safety. This important issue has been experimentally studiedin triaxial compression tests on the Callovo-Oxfordian clay rock in this study. The samples weresequentially loaded by (1) hydrostatic precompaction to close up sampling-induced microcracks, (2)applying deviatoric stresses to determine damage and permeability changes, and (3) recompressionalong different loading paths to examine reversibility of the damage. The critical stress conditions at theonset of dilatancy, permeability percolation, failure strength, and residual strength are determined. Anempirical model is established for fracturing-induced permeability by considering the effects of connectivityand conductivity of microcracks. The cubic law is validated for the variation of permeability ofconnected fractures with closure. The experiments and results are also presented and discussed.
  • A laboratory acoustic emission experiment and numerical simulationof rock fracture driven by a high-pressure fluid source 免费阅读 下载全文
  • In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluidsources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPawith fluid injection in the laboratory. Furthermore, we tested a number of numerical models using theFLAC3D modeling software to find the best model to represent the experimental results. The high-speedmultichannel acoustic emission (AE) waveform recording system used in this study made it possible toexamine the total fracture process through detailed monitoring of AE hypocenters and seismic velocity.The experimental results show that injecting high-pressure oil into the rock sample can induce AE activityat very low stress levels and can dramatically reduce the strength of the rock. The results of thenumerical simulations show that major experimental results, including the strength, the temporal andspatial patterns of the AE events, and the role of the fluid can be represented fairly well by a modelinvolving (1) randomly distributed defect elements to model pre-existing cracks, (2) random modificationof rock properties to represent inhomogeneity introduced by different mineral grains, and (3)macroscopic inhomogeneity. Our study, which incorporates laboratory experiments and numericalsimulations, indicates that such an approach is helpful in finding a better model not only for simulatingexperimental results but also for upscaling purposes.
  • Effects of porosity on seismic velocities, elastic moduli and Poisson'sratios of solid materials and rocks 免费阅读 下载全文
  • The generalized mixture rule (GMR) is used to provide a unified framework for describing Young's (E),shear (G) and bulk (K) moduli, Lame parameter (l), and P- and S-wave velocities (Vp and Vs) as a functionof porosity in various isotropic materials such as metals, ceramics and rocks. The characteristic J values ofthe GMR for E, G, K and l of each material are systematically different and display consistent correlationswith the Poisson's ratio of the nonporous material (n0). For the materials dominated by corner-shapedpores, the fixed point at which the effective Poisson's ratio (n) remains constant is at n0 ?0.2, andJ(G) 〉 J(E) 〉 J(K) 〉 J(l) and J(G) 〈 J(E) 〈 J(K) 〈 J(l) for materials with n0 〉 0.2 and n0 〈 0.2, respectively.J(Vs) 〉 J(Vp) and J(Vs) 〈 J(Vp) for the materials with n0 〉 0.2 and n0 〈 0.2, respectively. The effective nincreases, decreases and remains unchanged with increasing porosity for the materials with n0 〈 0.2,n0 〉 0.2 and n0 ?0.2, respectively. For natural rocks containing thin-disk-shaped pores parallel to mineralcleavages, grain boundaries and foliation, however, the n fixed point decreases nonlinearly withdecreasing pore aspect ratio (a: width/length). With increasing depth or pressure, cracks with smaller avalues are progressively closed, making the n fixed point rise and finally reach to the point at n0 ?0.2.
  • Carbon sequestration potential of the Habanero reservoir whencarbon dioxide is used as the heat exchange fluid 免费阅读 下载全文
  • The use of sequestered carbon dioxide (CO2) as the heat exchange fluid in enhanced geothermal system(EGS) has significant potential to increase their productivity, contribute further to reducing carbonemissions and increase the economic viability of geothermal power generation. Coupled CO2 sequestrationand geothermal energy production from hot dry rock (HDR) EGS were first proposed 15 years agobut have yet to be practically implemented. This paper reviews some of the issues in assessing thesesystems with particular focus on the power generation and CO2 sequestration capacity. The Habanerogeothermal field in the Cooper Basin of South Australia is assessed for its potential CO2 storage capacity ifsupercritical CO2 is used as the working fluid for heat extraction. The analysis suggests that the major CO2sequestration mechanisms are the storage in the fracture-stimulation damaged zone followed bydiffusion into the pores within the rock matrix. The assessment indicates that 5% of working fluid losscommonly suggested as the storage capacity might be an over-estimate of the long-term CO2 sequestrationcapacity of EGS in which supercritical CO2 is used as the circulation fluid.
  • Predicting excavation damage zone depths in brittle rocks 免费阅读 下载全文
  • During the construction of an underground excavation, damage occurs in the surrounding rock massdue in large part to stress changes. While the predicted damage extent impacts profile selection andsupport design, the depth of damage is a critical aspect for the design of permeability sensitive excavations,such as a deep geological repository (DGR) for nuclear waste. Review of literature regardingthe depth of excavation damage zones (EDZs) indicates three zones are common and typically relatedto stress induced damage. Based on past developments related to brittle damage prediction usingcontinuum modelling, the depth of the EDZs has been examined numerically. One method to capturestress induced damage in conventional engineering software is the damage initiation and spallinglimit (DISL) approach. The variability of depths predicted using the DISL approach has been evaluatedand guidelines are suggested for determining the depth of the EDZs around circular excavations inbrittle rock masses. Of the inputs evaluated, it was found that the tensile strength produces thegreatest variation in the depth of the EDZs. The results were evaluated statistically to determine thebest fit relation between the model inputs and the depth of the EDZs. The best correlation and leastvariation were found for the outer EDZ and the highly damaged zone (HDZ) showed the greatestvariation. Predictive equations for different EDZs have been suggested and the maximum numericalEDZ depths, represented by the 68% prediction interval, agreed well with the empirical evidence. Thissuggests that the numerical limits can be used for preliminary depth prediction of the EDZs in brittlerock for circular excavations.
  • A simple approach for the estimation of CO2 penetration depth into acaprock layer 免费阅读 下载全文
  • Caprock is a water-saturated formation with a sufficient entry capillary pressure to prevent the upwardmigration of a buoyant fluid. When the entry capillary pressure of caprock is smaller than the pressureexerted by the buoyant CO2 plume, CO2 gradually penetrates into the caprock. The CO2 penetration depthinto a caprock layer can be used to measure the caprock sealing efficiency and becomes the key issue tothe assessment of caprock sealing efficiency. On the other hand, our numerical simulations on a caprocklayer have revealed that a square root law for time and pore pressure exists for the CO2 penetration intothe caprock layer. Based on this finding, this study proposes a simple approach to estimate the CO2penetration depth into a caprock layer. This simple approach is initially developed to consider the speedof CO2 invading front. It explicitly expresses the penetration depth with pressuring time, pressure differenceand pressure magnitude. This simple approach is then used to fit three sets of experimental dataand good fittings are observed regardless of pressures, strengths of porous media, and pore fluids (water,hydrochloric acid, and carbonic acid). Finally, theoretical analyses are conducted to explore those factorsaffecting CO2 penetration depth. The effects of capillary pressure, gas sorption induced swelling, and fluidproperty are then included in this simple approach. These results show that this simple approach canpredict the penetration depth into a caprock layer with sufficient accuracy, even if complicated interactionsin penetration process are not explicitly expressed in this simple formula.
  • Numerical simulation of displacement characteristics of CO2 injectedin pore-scale porous media 免费阅读 下载全文
  • Pore structure of porous media, including pore size and topology, is rather complex. In immiscible twophasedisplacement process, the capillary force affected by pore size dominates the two-phase flow inthe porous media, affecting displacement results. Direct observation of the flow patterns in the porousmedia is difficult, and therefore knowledge about the two-phase displacement flow is insufficient. In thispaper, a two-dimensional (2D) pore structure was extracted from a sandstone sample, and the flowprocess that CO2 displaces resident brine in the extracted pore structure was simulated using the NaviereStokes equation combined with the conservative level set method. The simulation results reveal thatthe pore throat is a crucial factor for determining CO2 displacement process in the porous media. Thetwo-phase meniscuses in each pore throat were in a self-adjusting process. In the displacement process,CO2 preferentially broke through the maximum pore throat. Before breaking through the maximum porethroat, the pressure of CO2 continually increased, and the curvature and position of two-phase interfacesin the other pore throats adjusted accordingly. Once the maximum pore throat was broken through bythe CO2, the capillary force in the other pore throats released accordingly; subsequently, the interfaceswithdrew under the effect of capillary fore, preparing for breaking through the next pore throat.Therefore, the two-phase displacement in CO2 injection is accompanied by the breaking through andadjusting of the two-phase interfaces.
  • Multiphysics of carbon dioxide sequestration in coalbeds: A reviewwith a focus on geomechanical characteristics of coal 免费阅读 下载全文
  • To reduce the emissions of carbon dioxide (CO2) into the atmosphere, it is proposed to inject anthropogenicCO2 into deep geological formations. Deep un-mineable coalbeds are considered to be possibleCO2 repositories because coal is able to adsorb a large amount of CO2 inside its microporous structure.However, the response of coalbeds is complex because of coupled flow and mechanical processes. Injectionof CO2 causes coal to swell, which leads to reductions in permeability and hence makes injectionmore difficult, and at the same time leads to changes in the mechanical properties which can affect thestress state in the coal and overlying strata. The mechanical properties of coal under storage conditionsare of importance when assessing the integrity and safety of the storage scheme. On the other hand, thegeomechanical response of coalbed will also influence the reservoir performance of coalbed. This paperprovides an overview of processes associated with coalbed geosequestration of CO2 while the importanceof geomechanical characteristics of coalbeds is highlighted. The most recent findings about the interactionsbetween gas transport and geomechanical characteristics of coal will be discussed and theessence will be delivered. The author suggests areas for future research efforts to further improve theunderstanding of enhanced coalbed methane (ECBM) and coalbed geosequestration of CO2.
  • Laboratory core flooding experimental systems for CO2geosequestration: An updated review over the past decade 免费阅读 下载全文
  • Carbon dioxide (CO2) geosequestration in deep saline aquifers has been currently deemed as a preferableand practicable mitigation means for reducing anthropogenic greenhouse gases (GHGs) emissions to theatmosphere, as deep saline aquifers can offer the greatest potential from a capacity point of view. Hence,research on core-scale CO2/brine multiphase migration processes is of great significance for preciselyestimating storage efficiency, ensuring storage security, and predicting the long-term effects of thesequestered CO2 in subsurface saline aquifers. This review article initially presents a brief description ofthe essential aspects of CO2 subsurface transport and geological trapping mechanisms, and then outlinesthe state-of-the-art laboratory core flooding experimental apparatus that has been adopted for simulatingCO2 injection and migration processes in the literature over the past decade. Finally, a summary ofthe characteristics, components and applications of publicly reported core flooding equipment as well asmajor research gaps and areas in need of further study are given in relevance to laboratory-scale coreflooding experiments in CO2 geosequestration under reservoir conditions.
  • 《岩石力学与岩土工程学报:英文版》封面

    关于我们 | 网站声明 | 合作伙伴 | 联系方式 | IP查询
    金月芽期刊网 2017 触屏版 电脑版 京ICP备13008804号-2