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1.
In this paper, we develop a multiscale model reduction technique that describes shale gas transport in fractured media. Due to the pore-scale heterogeneities and processes, we use upscaled models to describe the matrix. We follow our previous work (Akkutlu et al. Transp. Porous Media 107(1), 235–260, 2015), where we derived an upscaled model in the form of generalized nonlinear diffusion model to describe the effects of kerogen. To model the interaction between the matrix and the fractures, we use Generalized Multiscale Finite Element Method (Efendiev et al. J. Comput. Phys. 251, 116–135, 2013, 2015). In this approach, the matrix and the fracture interaction is modeled via local multiscale basis functions. In Efendiev et al. (2015), we developed the GMsFEM and applied for linear flows with horizontal or vertical fracture orientations aligned with a Cartesian fine grid. The approach in Efendiev et al. (2015) does not allow handling arbitrary fracture distributions. In this paper, we (1) consider arbitrary fracture distributions on an unstructured grid; (2) develop GMsFEM for nonlinear flows; and (3) develop online basis function strategies to adaptively improve the convergence. The number of multiscale basis functions in each coarse region represents the degrees of freedom needed to achieve a certain error threshold. Our approach is adaptive in a sense that the multiscale basis functions can be added in the regions of interest. Numerical results for two-dimensional problem are presented to demonstrate the efficiency of proposed approach.  相似文献   

2.
Soldini  L.  Antuono  M.  Brocchini  M. 《Natural Hazards》2016,84(2):621-635
This study, part of the Special Issue dedicated to the 70th anniversary of Professor Efim Pelinovsky, focuses on a topic that has been central in Professor Pelinovsky’s research, i.e. the analytical and numerical modelling of shallow water waves. We specifically focus on the evolution of trains of shock waves on a planar beach. Antuono (J Fluid Mech 658:166–187, 2011) has, for the first time, proposed a quasi-analytical solution for a train of shock waves forced by a constant Riemann invariant. The present contribution clarifies the validity of such solution and its value for benchmarking nonlinear shallow water equation solvers. Hence, the same tests of Antuono (J Fluid Mech 658:166–187, 2011) have been run by means of the solver of Brocchini et al. (Coast Eng 43(2):105–129, 2001) revealing surprisingly and reassuring good agreements. This provides significant support to the mentioned analytical solution and allows to critically analyse the eventual discrepancies, due to the practicalities of running numerical shallow water solutions (e.g. influence of the boundary conditions, of the numerical resolution, etc.).  相似文献   

3.
This paper presents a novel macroelement for single vertical piles in sand developed within the hypo-plasticity theory, where the incremental nonlinear constitutive equations are defined in terms of generalized forces, displacements and rotations. Inspired from the macroelement for shallow foundations of Salciarini and Tamagnini (Acta Geotech, 4(3):163–176, 2009), the new element adopts the “intergranular displacement” mutuated from Niemunis and Herle (Mech Cohes Frict Mater, 2:279–299, 1997) to reproduce the behavior under cyclic loading. Analytical and numerical strategies are provided to calibrate the macroelement’s parameters. Comparisons with experimental results show the performance of the macroelement that while being simple and computational fast is suitable for finite element calculations and engineering design.  相似文献   

4.
In a fluid system in which two immiscible layers are separated by a sharp free interface, there can be strong coupling between large amplitude nonlinear waves on the interface and waves in the overlying free surface. We study the regime where long waves propagate in the interfacial mode, which are coupled to a modulational regime for the free-surface mode. This is a system of Boussinesq equations for the internal mode, coupled to the linear Schrödinger equations for wave propagation on the free surface, and respectively a version of the Korteweg-de Vries equation for the internal mode in case of unidirectional motions. The perturbation methods are based on the Hamiltonian formulation for the original system of irrotational Euler’s equations, as described in (Benjamin and Bridges, J Fluid Mech 333:301–325, 1997, Craig et al., Comm Pure Appl Math 58:1587–1641, 2005a, Zakharov, J Appl Mech Tech Phys 9:190–194, 1968), using the perturbation theory for the modulational regime that is given in (Craig et al. to appear). We focus in particular on the situation in which the internal wave gives rise to localized bound states for the Schrödinger equation, which are interpreted as surface wave patterns that give a characteristic signature of the presence of an internal wave soliton. We also comment on the discrepancies between the free interface-free surface cases and the approximation of the upper boundary condition by a rigid lid.  相似文献   

5.
The garnet–orthopyroxene pairs are commonly found in the assemblages of basic granulites/charnockite and hence are suitable for estimating equilibrium temperature of these metamorphic rocks. At present, there are many calibrations of garnet–orthopyroxene thermometer that may confuse geologists in choosing a reliable thermometer. To test the accuracy of the garnet–orthopyroxene thermometers, we have applied 14 models formulated by a number of workers since 1980 to date. We have collated 51 samples from the literature all over the world, which has been processed through the “Gt-Opx.EXE” software. Based on the present study, we have identified a set of the best among all the 14 models which were considered under this comparative study. We have concluded that the five garnet–orthopyroxene (Gt-Opx) thermometers are the most valid and reliable of this kind of thermometer: Aranovich and Berman (Am Mineral 82:345–353, 1997), Raith et al. (Earth Sci 73:211–244, 1983), Harley (Contrib Mineral Petrol 86:359–373, 1984), Nimis and Grütter (Contrib Mineral Petrol 159:411–427, 2010), and Sen and Bhattacharya (Contrib Mineral Petrol 88:64–71, 1984).  相似文献   

6.
This study provides new insights into the relationship between radiation-dose-dependent structural damage due to natural U and Th impurities and the anisotropic mechanical properties (Poisson’s ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. in Am Mineral 76:1510–1532, 1991) and synthetic samples, covering a dose range of zero up to 6.8 × 1018 α-decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by Özkan (J Appl Phys 47:4772–4779, 1976), revealed a general radiation-induced decrease in stiffness (~54 %) and hardness (~48 %) and an increase in the Poisson’s ratio (~54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Ríos et al. in J Phys Condens Matter 12:2401–2412, 2000a; Farnan and Salje in J Appl Phys 89:2084–2090, 2001; Zhang and Salje in J Phys Condens Matter 13:3057–3071, 2001). The excellent agreement, revealed by the different methods, indicates a large influence of structural and even local phenomena on the macroscopic mechanical properties. Therefore, this study indicates the importance of acquiring better knowledge about the mechanical long-term stability of radiation-damaged materials.  相似文献   

7.
The 2010 eruption of the Eyjafjallajökull volcano had a devastating effect on the European air traffic network, preventing air travel throughout most of Europe for 6 days (Oroian in ProEnvironment 3:5–8, 2010). The severity of the disruption was surprising as previous research suggests that this type of network should be tolerant to random hazard (Albert et al. in Nature 406(6794):378–382, 2000; Strogatz in Nature 410(6825):268–276, 2001). The source of this hazard tolerance lies in the degree distribution of the network which, for many real-world networks, has been shown to follow a power law (Albert et al. in Nature 401(6749):130–131, 1999; Albert et al. in Nature 406(6794):378–382, 2000). In this paper, we demonstrate that the ash cloud was unexpectedly disruptive because it was spatially coherent rather than uniformly random. We analyse the spatial dependence in air traffic networks and demonstrate how the combination of their geographical distribution and their network architectures jeopardises their inherent hazard tolerance.  相似文献   

8.
A reply essay is presented on the rebuttal article by Parise (Environ Earth Sci 75(23):1476, 2016) suggesting that qanat is not a hazard. It is presented as a refutation on the paper by Abbasnejad et al. (Environ Earth Sci 75:1306, 2016) in which the authors have explained the etiology, the impacts and remedies of a qanat hazard in Iranian urban areas. Since the majority of qanats in Iranian urban areas are abandoned, useless and threatening, according to definition and in comparison with similar features introduced as a hazard, they are considered as a hazard too. However, this does not mean, and Abbasnejad et al. (in Environ Earth Sci 75:1306, 2016) have not claimed, that all qanats are hazardous. In addition, the authors who have studied qanats in Iranian urban areas, before Abbasnejad et al. (in Environ Earth Sci 75:1306, 2016), have also considered qanats as a hazard.  相似文献   

9.
The echinoid fauna from the Miocene sedimentary succession cropping out south Wadi Tweirig, and Wadi Hommath, south Gebel Ataqa, NW Gulf of Suez, has been examined with the aim to known their stratigraphic and paleogeographic distribution. The Miocene succession includes two formations: Sadat Formation, unconformably overlying the middle/upper Eocene rocks at the base and Hommath Formation at the top. Twenty-eight echinoid species (8 regular and 20 irregular) belonging to 18 genera, 13 families, and 7 orders have been identified, systematically described, and illustrated in this work. Eleven species are recorded for the first time from Egypt: ten of these came from the Hommath Formation (Schizechinus cf. serresii Desor (1856), Schizechinus pentagonus Kier 1972, Clypeaster cf. martini des Moulins 1837, Scutella checchiae occidentalis Desio 1934, Scutella melitensis Airaghi 1902, Echinodiscus desori Duncan and Sladen 1883, Echinolampas cf. zeitensis Fourtau 1920, Schizaster lovisatoi Cotteau 1895, Agassizia (Agassizia) powersi Kier 1972, and Hemipatagus ocellatus Defrance (1827)), and one from the Sadat Formation (Clypeaster campanulatus Schlotheim (1820)). The identified fauna shows a strong affinity with the Mediterranean bio-province.  相似文献   

10.
The paper suggests an alternative quantification of the Geological Strength Index (GSI) Chart published by Hoek et al. in Paper prepared for presentation at the 47th US Rock mechanics/geomechanics symposium held in San Francisco (2013). The engineering parameters proposed for the horizontal and vertical axes of the Chart are the most commonly used in routine field investigations on rock masses by means of standard exposure surveys and borehole logging. They mainly include parameters traditionally used for block size characterization (i.e., volumetric joint count Jv, joint spacing S and RQD/Jn factor) as well as other parameters purposely defined in the present study and based on combinations of the traditional ratings of the Bieniawski’s RMR89 classification. Adopting these options, new empirical equations for calculating the GSI have been fine tuned and tested on a real rock mass dataset. The comparison between the GSI values calculated using the new equations and those directly mapped during underground excavations has demonstrated the potentiality of the proposed methodology. The new quantification of the GSI Chart can be regarded as a useful and practical tool suitable to integrate the Hoek et al. (2013) approach. The complementary use of different and independent methods represents an effective practice to properly check and validate the final estimation of the GSI.  相似文献   

11.
The authors (Lloret-Cabot et al. in Acta Geotech 1–23, 2017) applied the glasgow coupled model (GCM), originally proposed by Wheeler et al. (Géotechnique 53(1):41–54, 2003), to the simulation of several experimental tests that involve transition between saturated and unsaturated states. The authors show qualitatively, but not quantitatively, predictions of GCM for shrinkage during air drying of normally consolidated samples (Fig. 13) under low mechanical stress conditions, without presenting the material parameters. The discussers, who have worked with GCM to model multilayer deposition of tailings/soft soils (Qi in Numerical investigation for slope stability of expansive soils and large strain consolidation of soft soils. Doctoral dissertation, University of Ottawa, 2017; Qi et al. in J Geotech Geoenviron Eng 143(7):04017018, 2017, Qi et al. J Geotech Geoenviron Eng 143(7):04017019, 2017), have made quantitative predictions of similar cases. Satisfactory simulations of such cases using GCM are sensitive to the selection of the coupling parameters k1 and k2. By considering an alternative analytical form of GCM, an analytical procedure can be derived for calibrating the coupling parameters for problems involving virgin drying.  相似文献   

12.
Earth Science community depends on the exploration, analysis and reprocessing of high volumes of data as well as the modeling and simulation of complex coupled systems on multiple scales. The main aim of this article is to introduce a new hydrological modeling service based on the Soil and Water Assessment Tool (SWAT) (Arnold et al. J American Water Resour Assoc 34(1), 73–89, 1998 ; Arnold and Fohrer Hydrol Process 19(3), 563–572, 2005) model using high efficiency, resource sharing and low cost cloud computing resources (Astsatryan et al. International Journal of Scientific & Engineering Research 1(1), 1130–1133, 2014). Such a Desktop as a Service (DaaS) approach allowing users to work from anywhere, and gives centralized desktop management and great performance. Within the Spatial Data Infrastructure (SDI) and cloud platform, the DaaS service gives secure access to the model and a centralized data storage to get a SWAT model input. The article illustrates the analyses of the implementation of the SWAT model for the Sotk watershed of Lake Sevan in Armenia (Sargsyan 2007).  相似文献   

13.
A computationally robust framework for simulating geomaterial failure patterns is presented in this paper. Finite element simulations which feature the use of embedded discontinuities to track material failure are known to suffer from convergence issues due to a lack of robustness. Oftentimes, complex time step-cutting schemes or arc-length methods are required in order to achieve convergence. This may invariably limit the complexity of constitutive models available for use in tracking nonlinear material behavior. To this end, we use an implicit–explicit integration scheme [Impl–Ex (Oliver et al. in Comput Methods Appl Mech Eng 195(52):7093–7114, 2006)] coupled with a novel constitutive model which allows for combined opening and shearing displacement in tension, as well as frictional sliding in compression. We show that this framework is suitable for capturing complex fracture patterns in geomaterial structures without the need for elaborate continuance schemes.  相似文献   

14.
An enhanced SMA based SCS-CN inspired model for watershed runoff prediction   总被引：1，自引：0，他引：1  
Incorporation of initial soil moisture (V 0) in the Soil Conservation Service Curve Number (SCS-CN) methodology helps to avoid the sudden jumps in Curve Number (CN) and, in turn, in computed runoff. It invoked the development of an enhanced (yet simple) Soil Moisture Accounting (SMA) procedure-based-SCS-CN inspired model, by incorporating initial moisture (V 0). Its performance is tested using a dataset of 152 small to large watersheds of USDA (total 38,169 storm events), and compared with original SCS-CN method, Mishra and Singh (Acta Geophys Polon 50(3):457–477, 2002), Michel et al. (Water Resour Res 41(2):W02011, 2005) and Singh et al. (Water Resour Manag 29(11): 4111–4127, 2015) model using four statistical indices (RMSE, R 2, PBIAS and NSE) and rank grading system (RGS). The proposed model scores highest (= 691 marks out of maximum 2280 marks) (Rank I) followed by Singh et al. (Water Resour Manag 29(11):4111–4127, 2015) model with 642 marks (Rank II), Michel et al. (Water Resour Res 41(2):W02011, 2005) model with 376 marks (Rank III) and Mishra and Singh model with 362 marks (= Rank IV). The original SCS-CN model, however, performs the poorest of all with 209 marks (Rank V).  相似文献   

15.
According to the International Society of Rock Mechanics, squeezing is a time dependent large deformation occurring during tunnel construction around the tunnel associated with creep caused by exceeding a limiting shear stress (Barla in ISRM News J 2:44–49, 1995). This research is conducted using a case study on the Nowsoud Tunnel, Iran. Being 14 km in length and 4.5 m in diameter, the tunnel is located in the western part of Iran near the Iraq border. Nowsoud tunnel, which was excavated using a double shield TBM, exhibited severe squeezing (with 8919 m) in its critical zone which resulted in excavation termination. In this research, the best approach for predicting squeezing among the recommended methods for reducing the damages caused by squeezing on TBM was determined. In this regard, approaches commonly used to predict squeezing are empirical, semi-empirical, and theoretical–analytical methods. Besides, these methods, numerical modeling is used to estimate convergence generated along the tunnel pathways, which is ultimately used to categorize squeezing. This paper compares squeezing prediction methods in 68 section of Nowsoud Tunnel. These 68 sections indicate that the empirical methods propose a general estimation/overview of squeezing. Among the semi-analytical approaches, the one proposed by Hoek and Marinos (Rock engineering in difficult rock conditions—soft rocks and karst, Taylor & Francis Group, London, pp 49–60, 2000) are compatible with the occurrence of squeezing in the critical zone. However, the degree of predicted squeezing is less than the real degree of squeezing in this zone. Based on the result of Aydan approach, 75 % of the tunnel sections are under squeezing condition. Theoretical–analytical approaches underestimate the possibility of squeezing in the critical zone. Barla?s approach (1995) demonstrated the possibility of squeezing in the critical zone with low intensity. The numerical computations in this paper were performed using Plaxis (version 8.5), a two-dimensional numerical program based on the finite element method. Plaxis results, classified by Hoek and Marinos (2000) method, show that 8800 m of the tunnel length is under the non-squeezing condition. According to all prediction methods, the squeezing zones depend on faulted zones, argillaceous limestone and shale formations such as J1Kh, J4Kh, J5Kh, and Kgr. These formations were identified with a high quantity of shale and argillaceous limestone. Bedding of these geological formations is thin and their geotechnical properties are weaker than those of limestone formations. On the other hand, non-squeezing zones depend on limestone formations such as J2Kh, J3Kh, J6Kh, Kabg, and Kbg. Moreover, all approaches predicted squeezing potential for the critical zone where TBM is jammed.  相似文献   

16.
Copper is a moderately incompatible chalcophile element. Its behavior is strongly controlled by sulfides. The speciation of sulfur is controlled by oxygen fugacity. Therefore, porphyry Cu deposits are usually oxidized (with oxygen fugacities > ΔFMQ +2) (Mungall 2002; Sun et al. 2015). The problem is that while most of the magmas at convergent margins are highly oxidized, porphyry Cu deposits are very rare, suggesting that high oxygen fugacity alone is not sufficient. Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly (Lee et al. 2012; Wilkinson 2013). Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity (>ΔFMQ +2) may form magmas with initial Cu contents up to >500 ppm, favorable for porphyry mineralization. Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization. In contrast, re-melting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits. Thick overriding continental crust reduces the “leakage” of hydrothermal fluids, thereby promoting porphyry mineralization. Nevertheless, it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2–4 km where porphyry deposits form.  相似文献   

17.
This paper presents a simulation of three components of near-field ground shaking recorded during the main shock at three stations of the September 16, 1978, Tabas (M w = 7.4), Iran, earthquake, close to the causative fault. A hybrid method composed of a discrete wavenumber method developed by Bouchon (Bouchon in Bull Seismol Soc Am 71:959–971, 1981; Cotton and Coutant in Geophys J Int 128:676–688, 1997) and a stochastic finite-fault modeling based on a dynamic corner frequency proposed by Motazedian and Atkinson (Bull Seismol Soc Am 95:995–1010, 2005), modified by Assatourians and Atkinson (Bull Seismol Soc Am 97:935–1949, 2007), is used for generating the seismograms at low (0.1–1.0 Hz) and high frequencies (1.0–20.0 Hz), respectively. The results are validated by comparing the simulated peak acceleration, peak velocity, peak displacement, Arias intensity, the integral of velocity squared, Fourier spectrum and acceleration response spectrum on a frequency-by-frequency basis, the shape of the normalized integrals of acceleration and velocity squared, and the cross-correlation with the observed time-series data. Each characteristic is compared on a scale from 0 to 10, with 10 being perfect agreement. Also, the results are validated by comparing the simulated ground motions with the modified Mercalli intensity observations reported by reconnaissance teams and showed reasonable agreement. The results of the present study imply that the damage distribution pattern of the 1978 Tabas earthquake can be explained by the source directivity effect.  相似文献   

18.
Impacts of climate change have been observed in natural systems and are expected to intensify in future decades (IPCC in Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change IPPC, Geneva, 2014). Governments are seeking to establish adaptive measures for minimizing the effects of climate change on vulnerable citizen groups, economic sectors and critical infrastructure (Adger et al. in Global Environ Change 15(2):77–86, 2005. doi: 10.1016/j.gloenvcha.2004.12.005; Smit and Wandel in Global Environ Change 16(3):282–292, 2006. doi: 10.1016/j.gloenvcha.2006.03.008). Coastal areas are particularly vulnerable to changing conditions due to rising sea levels and storm event intensification that produce new flood exposures (Richards and Daigle in Government of Prince Edward Island, Halifax, Nova Scotia, 2011 http://www.gov.pe.ca/photos/original/ccscenarios.pdf). However, communities oftentimes lack access to locally-relevant climate change information that can support adaptation planning. This research introduces the use of a Geoweb tool for supporting local climate change adaptation efforts in coastal Canadian communities. The Geoweb tool (called “AdaptNS”) is a web-based visualization tool that displays interactive flood exposure maps generated using local climate change projections of sea level rise and storm surge impacts between the years 2000 and 2100. AdaptNS includes participatory features that allow users to identify and share specific locations to protect against present and future coastal flood events. By soliciting feedback from community members, AdaptNS is shown to support local adaptation through the provision of flood exposure visuals, as a platform for identifying adaptation priorities, and as an avenue to communicate local risks to external entities that could facilitate local adaptation initiatives (e.g. upper levels of government). Future Geoweb research directions include improving the visualization of climate change projection uncertainties, the expansion of informational and participation capabilities, and understanding the potential for long-term adoption of Geoweb tools in adaptation decision-making.  相似文献   

19.
Micro-mechanical failure analysis of wet granular matter   总被引：1，自引：1，他引：0  
We employ a novel fluid–particle model to study the shearing behavior of granular soils under different saturation levels, ranging from the dry material via the capillary bridge regime to higher saturation levels with percolating clusters. The full complexity of possible liquid morphologies Scheel et al. (Nat Mater 7(3):189–193, 2008. doi: 10.1038/nmat2117) is taken into account, implying the formation of isolated arbitrary-sized liquid clusters with individual Laplace pressures that evolve by liquid exchange via films on the grain surface Melnikov et al. (Phys Rev E 92(022):206, 2015. doi: 10.1103/PhysRevE.92.022206). Liquid clusters can grow in size, shrink, merge and split, depending on local conditions, changes of accessible liquid and the pore space morphology determined by the granular phase. This phase is represented by a discrete particle model based on contact dynamics Brendel et al. (Contact dynamics for beginners. Wiley-VCH, Weinheim, 2005. doi: 10.1002/352760362X.ch14), where capillary forces exerted from a liquid phase add to the motion of spherical particles. We study the macroscopic response of the system due to an external compression force at various liquid contents with the help of triaxial shear tests. Additionally, the change in liquid cluster distributions during the compression due to the deformation of the pore space is evaluated close to the critical load.  相似文献   

20.
In mountainous areas, channelized rock avalanches swarm downslope leading to large impact forces on building structures in residential areas. Arrays of rock avalanche baffles are usually installed in front of rigid barriers to attenuate the flow energy of rock avalanches. However, previous studies have not sufficiently addressed the mechanisms of interaction between the rock avalanches and baffles. In addition, empirical design approaches such as debris flow (Tang et al., Quat Int 250:63–73, 2012), rockfall (Spang and Rautenstrauch, 1237–1243, 1988), snow avalanches (Favier et al., 14:3–15, 2012), and rock avalanches (Manzella and Labiouse, Landslides 10:23–36, 2013), which are applied in natural geo-disasters mitigation cannot met construction requirements. This study presents details of numerical modeling using the discrete element method (DEM) to investigate the effect of the configuration of baffles (number and spacing of baffle columns and rows) on the impact force that rock avalanches exert on baffles. The numerical modeling is firstly conducted to provide insights into the flow interaction between rock avalanches and an array of baffles. Then, a modeling analysis is made to investigate the change pattern of the impact force with respect to baffle configurations. The results demonstrate that three crucial influencing factors (baffle row numbers, baffle column spacing, and baffle row spacing) have close relationship with energy dissipation of baffles. Interestingly, it is found that capacity of energy dissipation of baffles increases with increasing baffle row numbers and baffle row spacing, while it decreases with increasing baffle column spacing. The results obtained from this study are useful for facilitating design of baffles against rock avalanches.  相似文献   

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