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With multiscale permeability estimation one does not select parameterization prior to the estimation. Instead, one performs a hierarchical search for the right parameterization while solving a sequence of estimation problems with an increasing parameterization dimension. In some previous works on the subject, the same refinement is applied all over the porous medium. This may lead to over-parameterization, and subsequently, to unrealistic permeability estimates and excessive computational work. With adaptive multiscale permeability estimation, the new parameterization at an arbitrary stage in the estimation sequence is such that new degrees of freedom are not necessarily introduced all over the porous medium. The aim is to introduce new degrees of freedom only where it is warranted by the data. In this paper, we introduce a novel adaptive multiscale estimation. The approach is used to estimate absolute permeability from two-phase pressure data in several numerical examples. 相似文献
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Lyu Chuangxin Nishimura Satoshi Amiri Seyed Ali Ghoreishian Zhu Feng Eiksund Gudmund Reidar Grimstad Gustav 《Acta Geotechnica》2021,16(12):3831-3847
Acta Geotechnica - A systematical testing program on frozen Onsøy clay under isotropic loading and undrained shearing at different temperatures... 相似文献
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Asbj?rn Torvanger Alv-Arne Grimstad Erik Lindeberg Nathan Rive Kristin Rypdal Ragnhild Bieltvedt Skeie Jan Fuglestvedt Petter Tollefsen 《Climatic change》2012,114(2):245-260
We explore allowable leakage for carbon capture and geological storage to be consistent with maximum global warming targets of 2.5 and 3 °C by 2100. Given plausible fossil fuel use and carbon capture and storage scenarios, and based on modeling of time-dependent leakage of CO2, we employ a climate model to calculate the long-term temperature response of CO2 emissions. We assume that half of the stored CO2 is permanently trapped by fast mechanisms. If 40?% of global CO2 emissions are stored in the second half of this century, the temperature effect of escaped CO2 is too small to compromise a 2.5 °C target. If 80?% of CO2 is captured, escaped CO2 must peak 300?years or later for consistency with this climate target. Due to much more CO2 stored for the 3 than the 2.5 °C target, quality of storage becomes more important. Thus for the 3 °C target escaped CO2 must peak 400?years or later in the 40?% scenario, and 3000?years or later in the 80?% scenario. Consequently CO2 escaped from geological storage can compromise the less stringent 3 °C target in the long-run if most of global CO2 emissions have been stored. If less CO2 is stored only a very high escape scenario can compromise the more stringent 2.5 °C target. For the two remaining combinations of storage scenarios and climate targets, leakage must be high to compromise these climate targets. 相似文献
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Vikas Thakur Steinar Nordal Gustav Grimstad 《Geotechnical and Geological Engineering》2006,24(6):1729-1747
A negative second order work, strain softening, is often noticed in contractant material like sensitive clays. Failure in
such clays will lead to the formation of localized deformation zone of intense inelastic strain, known as shear band. Conditions,
emergence and inclination of shear band has been very well demonstrated in past decades in different manners, however a definite
thickness of shear band is still an open question due to several reasons. Mesh dependency, loss of ellipticity is another
challenge associated with finite element analyses for strain softening clays. This paper covers a comprehensive review of
classical theories of strain localization and associated limitation. Mesh dependency, ill-possed boundary value problem is
addressed using finite element simulation examples and experimental results. 相似文献
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Rajinder Bhasin Nick Barton Eystein Grimstad Panayotis Chryssanthakis 《Engineering Geology》1995,40(3-4):169-193
A detailed engineering geological assessment of low strength (6–35 MPa) anisotropic rocks at an ongoing Hydroelectric Project in the Himalayan Region has been carried out. The project (the Nathpa Jhakri Hydroelectric Project) will have one of the world's largest and longest water conducting systems, consisting of a 10.15 m diameter and 27.3 km long head race tunnel, a 942 000 m3 underground desilting complex and a 20 × 49 × 216 m powerhouse cavern in the area. Because these constructions are made in low strength metamorphosed anisotropic rocks like quartz mica schists, biotite schists and muscovite schists, it seemed necessary and worthwhile to undertake a comprehensive study of such rocks. The studies include petrographic and petrofabric analyses of the rocks, geo-mechanical properties, rock stress measurements, rock mass classification using the Q-System and data concerning joint geometry, joint roughness and joint strength. The use of mapped geological and geotechnical data along with the experimental and modelling studies have helped to better understand the behaviour of these rocks in underground openings. 相似文献
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Gustav Grimstad Mohammad Ali Haji Ashrafi Samson Abate Degago Arnfinn Emdal Steinar Nordal 《Geomechanics and Geoengineering》2016,11(1):86-93
Settlement analysis of field cases is normally studied based on parameters interpreted from laboratory samples influenced by varying degrees of sample disturbance. Such disturbance is more pronounced in natural soft clays and could significantly affect the engineering properties of the soil, e.g. the over consolidation ratio (OCR) and compressibility index (Cc). Hence, it is vital to understand the role of sample quality in relation to soil characterisation for long-term settlement analyses. In this work, this is numerically illustrated by use of a simple creep model along with realistic parameter selection. This work takes its starting point on critical discussion of the work presented by Fatahi et al. (2013) and uses the opportunity to further clarify some important aspects of settlement/creep analyses in light of sample quality and parameter interpretation valid for the corresponding constitutive model. 相似文献
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Hao Gao Seyed Ali Ghoreishian Amiri Signe Kjelstrup Gustav Grimstad Benoit Loranger Elena Scibilia 《国际地质力学数值与分析法杂志》2023,47(1):82-105
This paper presents a fully coupled thermo-hydro-mechanical (THM) model which simulates frost heave in fully saturated soils. The model is able to simulate the formation and growth of multiple distinct ice lenses. The basic equations of the system were derived using the continuum theory of mixtures, nonequilibrium thermodynamics, and fracture mechanics, considering skeleton deformation, water flow and heat transport. Central to this model is the coupled transport of mass due to the temperature gradient across the frozen fringe, which acts as the main driving force of the phenomenon. The model is formulated in terms of measurable physical properties and thus no ad hoc parametrization is required. In an ice-lens-free state, the system is solved as a continuum using the finite element method (FEM). It is then locally treated as a discontinuous system upon the formation of ice lens, by enriching the elements carrying the embedded ice lens(es) using the extended finite element method (X-FEM). The accuracy and efficiency of the proposed model has been verified using several laboratory tests on Devon silt samples at different overburden pressures and thermal boundary conditions. Shut-off pressures have been also estimated and compared with the experimental results. 相似文献
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Many geotechnical problems involve undrained behavior of clay and the capacity in undrained loading. Most constitutive models used today are effective stress based and only indirectly obtain values for the undrained shear strength. To match the design profiles of undrained shear strengths, in active (A), direct simple shear (D) and passive (P) modes of loading are complicated. This paper presents the elastoplastic constitutive model NGI‐ADP which is based on the undrained shear strength approach with direct input of shear strengths. Consequently, exact match with design undrained shear strengths profiles is obtained and the well‐known anisotropy of undrained shear strength and stiffness is accounted for in the constitutive model. A non‐linear stress path‐dependent hardening relationship is used, defined from direct input of failure strains in the three directions of shearing represented by triaxial compression, direct simple shear and triaxial extension. With its clear input parameters the model has significant advantages for design analysis of undrained problems. The constitutive model is implemented, into finite element codes, with an implicit integration scheme. Its performance is demonstrated by a finite element analysis of a bearing capacity problem. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Rajinder Bhasin Eystein Grimstad Jan Otto Larsen Ashok K. Dhawan Rajbal Singh S. K. Verma K. Venkatachalam 《Engineering Geology》2002,64(4):351-368
Landslides and other mass movements are serious geo-environmental hazards in the Himalayas. Massive landslides killing tens of thousands of people with catastrophic damages have occurred in the Eastern Himalayan State of Sikkim, which shares common borders with Tibet, Nepal, and Bhutan. This paper describes the investigations carried out on recent landslides in Gangtok, Sikkim, India, with emphasis on the triggering mechanisms that have contributed to the release and creep of natural slopes in the region. It is believed that the intense rainfall in the region not only contributes to rapid erosion and weathering of the rock mass, but also increases the groundwater level that leads to reduction in the stability of natural slopes. A landslide instrumentation programme that includes placement of settlement pillars and piezometers is underway to predict the behaviour of landslides in the area. 相似文献
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