| 1. |
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| 2. |
- Alm, Ove, et al.
(författare)
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Experimental deformation of Augen-gneisses
- 1979
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Ingår i: Mechanisms of deformation and fracture. - Oxford : Pergamon Press. - 0080242588 ; , s. 173-186
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Konferensbidrag (refereegranskat)
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| 3. |
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| 4. |
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| 5. |
- Alm, Ove, et al.
(författare)
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Microstructures and mechanical characteristics of the Tännäs augen gneiss, Swedish Caledonides
- 1980
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Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 102:4, s. 319-334
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical behaviour, microstructure and substructure of the classic Tannas augen gneiss of the Swedish Caledonides are presented. Progressive deformation of granodiorite to augen gneiss and mylonite is shown to take place in an isochemical environment with redistribution of megacrysts to surrounding matrix. Experimental deformation of natural rocks from the Tannas Augen Gneiss Nappe has been carried out in the temperature range of 20-600oC and under confining pressure of 100-700MPa. The highest strength found is for the fine-grained mylonite. The augen of the gneiss show brittle behaviour under all test conditions, and temperature has a limited effect on the ultimate strength of the matrix of the augen gneiss. Microstructures have been analysed by means of optical microscopy and transmission electron microscopy. The progressive deformation is brought about by dislocation glide and dislocation creep. Subgrain formation, recrystallization and straining of new grains are observed at all stages of the progressive deformation of the matrix while the augen behavior is brittle
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| 6. |
- Hakami, H., et al.
(författare)
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Gauged sleeve for controlled testing of rock
- 1987
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 24:6, s. 375-378
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Tidskriftsartikel (refereegranskat)abstract
- Electrical resistance strain gages, each 5 cm in length, were embedded at a depth of 1 mm, inside a Cil Monothane sleeve of thickness 2 mm. Cil Monothane A80 is a single component and non-toxic, heat-cure-pour polyurethane elastomer. It has sound elasto-plastic properties when cured. It was supplied by Compounding Ingredients Ltd, England. The strain gages cover about 95% of the circumference of the sleeve. The position of the strain gages corresponds to the mid-height of the rock sample
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| 7. |
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| 8. |
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| 9. |
- Ask, Maria, et al.
(författare)
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In-situ stress determination from breakouts in the Tornquist Fan, Denmark
- 1996
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 8:6, s. 575-584
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Tidskriftsartikel (refereegranskat)abstract
- The Tornquist Fan, a fan-shaped region in Denmark and Western Baltic, is situated in the transition zone between the Western and Northern European Stress Provinces. Breakout data from 20 wells (0.3-3.6 km) were analysed. The fan can be divided into three stress provinces: (i) The area south of the Romo Fracture Zone is part of the Western European Stress Province and has NNW-SSE orientation of the maximum horizontal stress, (ii) The sediment cover in the Norwegian-Danish Basin is dominated by ENE-WSW orientated maximum horizontal stress, (iii) The maximum horizontal stress is sub-parallel to the strike of the Sorgenfrei-Tornquist Zone. Deviations from the regional stress field were observed in wells close to faults and salt diapirs. In wells south of the Sorgenfrei-Tornquist Zone, breakout occurrence decreases with increasing age of the stratigraphic units. The downhole breakout distribution seems to correlate with lithology and thickness of the sediment layer.
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| 10. |
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| 11. |
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| 12. |
- Backers, Tobias, et al.
(författare)
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New data on Mode II fracture toughness of rock from the punch through shear test
- 2004
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 41:1, s. 2-7
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Tidskriftsartikel (refereegranskat)abstract
- The Punch-Through Shear (PTS) test was introduced as a method to determine the ModeII fracture toughness of rock material (Backers et al., 2002). Its unique feature is the ability to apply a confining pressure independent of the Mode II (shear) loading. This contribution reports new data on Mode II fracture toughness', KIIC, dependency on confining pressure, loading rate, sample size, and cyclic loading for six different rocktypes. Samples are subjected to different confining pressures up to 70 MPa. KIICincreases with increasing confining pressure and tends to reach a constant value at confining pressures higher than 20-35 MPa. Evidence for 'pure' Mode II fracturetoughness at high confining pressures is reported. Variation of loading rate over five orders of magnitude (10-8 - 10-3 m/s) does not change KIIC. The influence of sample size on coarser grained rocks is verified. Cyclic loading illustrates change of stiffness of the system as fracture propagation takes place. It is concluded that the PTS- test is a suitable future method for KIICtermination.
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| 13. |
- Birkholzer, Jens T., et al.
(författare)
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25 years of DECOVALEX - Scientific advances and lessons learned from an international research collaboration in coupled subsurface processes
- 2019
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1365-1609 .- 1873-4545. ; 122
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Forskningsöversikt (refereegranskat)abstract
- This paper provides an overview of an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. The creation of the international DECOVALEX Project, now running for over 25 years, was initially motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. Later it was realized that these processes also play a critical role in other subsurface engineering activities, such as storage of CO2, exploration of enhanced geothermal systems, and unconventional oil and gas production through hydraulic fracturing. Research teams from radioactive waste management organizations, national research institutes, regulatory agencies, universities, as well as industry and consulting groups have participated in the DECOVALEX Project, providing a wide range of perspectives and solutions to these complex problems. Analysis and comparative modeling of state-of-the-art field and laboratory experiments has been at the core of the collaborative work, with an increasing focus on characterizing uncertainty and blind prediction of experimental results. Over these 25 years, many of the major advances in this field of research have been made through DECOVALEX, as evidenced by three books, seven journal special issues, and a good number of seminal papers that have emerged from the DECOVALEX modeling work. Examples of specific research advances will be presented in this paper to illustrate the significant impact of DECOVALEX on the current state-of-the-art of understanding and modeling coupled THMC processes. These examples range from the modeling of large-scale in situ heater tests representing mock-ups of nuclear waste disposal tunnels, to studies of fluid flow and chemical-mechanical coupling in heterogeneous fractures, and to the numerical analysis of controlled-injection meso-scale fault slip experiments.
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| 14. |
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| 15. |
- Bjarnason, B., et al.
(författare)
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New developments in hydrofracturing stress measurements at Luleå University of Technology
- 1989
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 26:6, s. 579-586
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Tidskriftsartikel (refereegranskat)abstract
- Instrument and theoretical developments in hydrofracturing stress measurements at Lulea University of Technology since the first workshop in Monterey in 1981 are described and the general experience with the method in Sweden is summarized. A new field unit is described which includes a 1000-m long multihose and a 100 MPa water pump. Stress measurements by means of injection tests on preexisting fractures have been introduced and applied at two sites in Sweden. A theory has been developed which permits estimation of the maximum and minimum horizontal stresses in cases where transverse hydrofractures are created in the borehole wall instead of axial.
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| 16. |
- Bjarnason, Bjarni, et al.
(författare)
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The Bolmen project
- 1986
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 17. |
- Björnfot, Folke, et al.
(författare)
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Interaction of grouted rock bolts and hard rock masses at variable loading in a test drift of the Kiirunavaara mine, Sweden
- 1984
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Ingår i: Rock bolting. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9061915147 ; , s. 377-395
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Konferensbidrag (refereegranskat)abstract
- description is presented on the interaction between a reinforced drift and the surrounding rock. It attempts to explain the support mechanisms and characteristics of cement grouted rock bolts, as used in hard rock mining and underground construction. A 20 m long section of a test drift at the 514 m level in the Kiirunavaara Mine, was instrumented with 20 rock bolts mounted with strain gauges and linked to a data logger, and 50 bolts combined with single-anchor extensometer. Rock movements were measured with 23 borehole extensometers, 45 convergence measurement stations, and precise levelling. 14 stress monitors recorded changes in the tangential stresses in the surrounding rock mass.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Borg, Torgny, et al.
(författare)
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Stability prediction for the Zinkgruvan mine, central Sweden
- 1984
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Ingår i: Design and performance of underground excavations. - London : British Geotechnical Society. - 0727702114 ; , s. 113-121
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Konferensbidrag (refereegranskat)abstract
- The geomechanics of the Zinkgruvan Mine are presented. A new approach for performing rock stress measurements in open stopes and drifts was tested. An elastic FEM model and strain failure criteria were applied to predict the future condition of the mine. Limits of the strain failure criteria were based on strain values obtained from the model, observations of rock falls, and major failures in the mine. These limits were used to assess suitable panel height, sill pillar dimensions, and sequence delays for mining parallel ore bodies.
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| 22. |
- Burns, K.L, et al.
(författare)
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The Flinders Ranges breccias of South Australia diapirs or décollement?
- 1977
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 134:3, s. 363-384
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Tidskriftsartikel (refereegranskat)abstract
- Breccia-cored domes in the Northern Flinders Ranges, South Australia, have been regarded as diapirs analogous to diapiric salt structures in northwestern Germany and the Gulf Coast. It is shown that the core of the Blinman Dome is not intrusive and is not composed of less dense rocks; hence a diapiric process cannot apply. It is suggested that much of the breccia of the core is formed by deformation of a stratigraphic unit composed of interbedded competent and incompetent beds at a Flinders Ranges dgcollernent and results from folding. If this model is correct, the Flinders Ranges structures should occur at ddcollements in other parts of the world.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Dresen, G, et al.
(författare)
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Rock damage and fluid transport : part 1
- 2006
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Ingår i: Pure and Applied Geophysics. - : Springer Science and Business Media LLC. - 0033-4553 .- 1420-9136. ; 163:5-6, s. 915-916
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Tidskriftsartikel (refereegranskat)
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| 29. |
- Einstein, H. H., et al.
(författare)
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Fracture systems, fracture propagation and coalescence
- 2018
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Ingår i: ISRM International Symposium 2000, IS 2000. - : International Society for Rock Mechanics.
-
Konferensbidrag (refereegranskat)abstract
- In the context of "strength of rocks for rock slope design" this paper concentrates on the fact that rock masses are discontinua and, in many cases, have to be modelled as such. The paper, therefore, first describes various ways in which fracture systems can be described. Specifically, geometric, mechanical and geometric - mechanical models are discussed with emphasis on the latter. When considering slope stability, as well as rock mass behavior in general, it is very important to capture the mechanisms by which the discontinuities interact with each other. This interaction involves fracture coalescence which is the second major part of the paper. While all the preceding problems involve mainly non-persistent fractures, a few final comments are made on some special issues relating to persistent fractures. Throughout the paper we attempt to present the state-of-the-art of theory and compare it to the state of practice.
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| 30. |
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| 31. |
- Granfors, Michaela, et al.
(författare)
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Placental location and risk of retained placenta in women with a previous cesarean section : A population-based cohort study.
- 2020
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 0001-6349 .- 1600-0412. ; 99:12, s. 1666-1673
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Some studies have shown that women with a previous cesarean section, compared with women with a previous vaginal delivery, have an increased risk of retained placenta during a subsequent vaginal delivery. It is unknown whether this is mediated by anterior placental location, when the placenta might cover the uterine scar. The aim of this study was to evaluate whether the increased risk of retained placenta in women with a previous cesarean section is mediated by anterior placental location.MATERIAL AND METHODS: This is a population-based cohort study, with data from the regional population-based Stockholm-Gotland Obstetric Cohort, Sweden, from 2008 to 2014. The overall study population included 49 598 women with a vaginal second delivery, where adequate information about placental location from the second-trimester ultrasound scan was available. For the main analysis, including the 3921 women with a previous cesarean section, we calculated the relative risk of retained placenta in women with an anterior placental location, using women with non-anterior placental locations as reference. Relative risks were calculated as odds ratios (OR) with 95% CI. In a second model, adjustments were made for maternal age, height, country of birth, smoking in early pregnancy, infant sex, and in vitro fertilization.RESULTS: In the overall study population, the rate of retained placenta at the second delivery was 2.0%. The proportion of women with a retained placenta was higher among women with a previous cesarean compared with those with a previous vaginal delivery (3.4% vs 1.9%; P < .0001). In the main analysis, including women with a previous cesarean section, the risk for retained placenta was not increased with anterior compared with non-anterior placental location (OR 0.84, 95% CI 0.60-1.20). Adjustments did not affect the estimates in a significant way.CONCLUSIONS: The increased risk of retained placenta in women with a previous cesarean section is not mediated by anterior placental location.
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| 32. |
- Hakami, H., et al.
(författare)
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Shear fracture energy of Stripa granite : Results of controlled triaxial testing
- 1990
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Ingår i: Engineering Fracture Mechanics. - 0013-7944 .- 1873-7315. ; 35:4-5, s. 855-865
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Tidskriftsartikel (refereegranskat)abstract
- We have performed controlled triaxial experiments on Stripa granite in a 'nearly stiff' environment. This means that, before the commencement of loading, an initial confining pressure was 'locked' in the pressurizing chamber of the triaxial vessel. During the axial loading of the sample, the confining pressure was unavoidably increased, opposing largely the 'free' expansion of the sample due to overall microcracking. Further increase in confining pressure beyond the peak load resulted from the dilation of the formed shear fracture, during shear displacement. Under triaxial testing condition a reasonable assumption is that the shear fracture in the specimen is a consequence of pure shear (mode II) state of stress prevailing in the sample, in the vicinity of a 'bandlike' zone, from which the shear fracture propagated. Under this assumption and by the relevant fracture mechanics approach incorporating the 'slip weakening' model, shear fracture energy of Stripa granite was estimated. The results were compared with those estimated through controlled triaxial experiments at constant confining pressure, recently reported by other workers. Also, the influence of the testing method described here on the process of laboratory failure of rock in shear is discussed.
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| 33. |
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| 34. |
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| 35. |
- Hudson, John A., et al.
(författare)
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Guidance on numerical modelling of thermo-hydro-mechanical coupled processes for performance assessment of radioactive waste repositories
- 2005
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 42:5-6, s. 850-870
-
Tidskriftsartikel (refereegranskat)abstract
- This paper provides advice on how to incorporate thermo-hydro-mechanical (THM) coupled processes into performance and safety assessments and design studies for radioactive waste disposal in geological formations. The advice is based on work conducted for the EU research project BENCHPAR: "Benchmark Tests and Guidance on Coupled Processes for Performance Assessment of Nuclear Waste Repositories". In Section 1, there is an explanation of why numerical analyses incorporating THM mechanisms are required for radioactive waste studies and background material on the subject is provided. Then, the THM processes and their interactions are explained in Section 2. Three case examples of THM numerical analysis are presented in Section 3 to illustrate the type of work that can be conducted to study the near-field, upscaling, and the far-field. The importance and priority of the THM couplings are summarized in Section 4. Recommended soft and hard auditing procedures are presented in Section 5. We place special emphasis on the fact that the most important step in numerical modelling is not executing the calculations per se, but the earlier conceptualization of the problem regarding the dominant processes, the material properties and parameters, the engineering perturbations, and their mathematical presentations. The associated modelling component of addressing the uncertainties and estimating their influence on the results is also important. Thus, the specific models and codes should be studied first to evaluate the harmony between the nature of the problem and the nature of the codes. The tactical use of particular numerical techniques will then be based on a sound strategic foundation. An associated listing of bullet point recommendations and issues for future directions for this THM subject area is given in Section 6.
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| 36. |
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| 37. |
- Jing, Lanru, et al.
(författare)
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An experimental study on the anisotropy and stress-dependency of the strength and deformability of rock joints
- 1992
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 29:6, s. 535-542
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Tidskriftsartikel (refereegranskat)abstract
- The anisotropy and stress-dependency of the strength and deformability of rock joints were investigated experimentally through shear tests of concrete replicas of natural rock joints. 50 concrete replicas of two natural granite joints were sheared on a servo-controlled hydraulic test frame under different magnitudes of normal stress and in different shear directions. Significant anisotropy in both the friction angle and shear stiffness of concrete replicas of joints were observed and both of them change with the variation of normal stress. The rates of dilatancy and contraction of joint samples appear to be different during cyclic shear tests, depending very much on the initial conditions of sample surfaces. Empirical relations were then postulated to describe these newly found properties of joint samples and used in developing new constitutive models for rock joints
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| 38. |
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| 39. |
- Jing, Lanru, et al.
(författare)
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Distinct element modelling of sublevel stoping
- 1991
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Ingår i: Berichte. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9054100125 ; , s. 741-746
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Konferensbidrag (refereegranskat)
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| 40. |
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| 41. |
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| 42. |
- Jing, Lanru, et al.
(författare)
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Numerical modelling of intraplate earthquake by 2-dimensional distinct element method
- 1990
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Ingår i: Gerlands Beitraege zur Geophysik. - 0016-8696. ; 989:5, s. 463-472
-
Tidskriftsartikel (refereegranskat)abstract
- computational model for an intraplate earthquake source, comprising of three blocks and two intersection faults, is analysed by using a two-dimensional Distinct Element Method. The Mohr-Coulumb model (M-CM) and Continuously-Yielding model (C-YM) of rock discontinuities are used to simulate the behaviour of the faults. Stick-slip phenomena are obtained for both models. The results support the idea that the nucleation of an intraplate earthquake starts at the intersects of faults
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| 43. |
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| 44. |
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| 45. |
- Jing, Lanru, et al.
(författare)
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Study of rock joints under cyclic loading conditions
- 1993
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Ingår i: Rock Mechanics and Rock Engineering. - 0723-2632 .- 1434-453X. ; 26:3, s. 215-232
-
Tidskriftsartikel (refereegranskat)abstract
- A conceptual model for the behaviour of rock joints during cyclic shear and under constant normal stresses was proposed according to results from shear tests with 50 concrete replicas of rock joints. The shear strength and deformability of joint samples were found to be both anisotropic and stress dependent. Based on these experimental results, a two-dimensional constitutive model was developed for rock joints undergoing monotonic or cyclic loading sequences. The joint model was formulated in the framework of non-associated plasticity, coupled with empirical relations representing the surface roughness degradation, appearance of peak and residual shear stresses, different rates of dilatancy and contraction, variable normal stiffness with normal deformation, and dependence of shear strength and deformability on the normal stress. The second law of thermodynamics was represented by an inequality and used to restrict the values of some of the material parameters in the joint model. The new joint model was implemented into a two-dimensional Distinct Element Method Code, UDEC, and its predictions agreed well with some well-known test results.
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| 46. |
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| 47. |
- Koyama, Tomofumi, et al.
(författare)
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Numerical simulation of shear-induced flow anisotropy and scale-dependent aperture and transmissivity evolution of rock fracture replicas
- 2006
-
Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 43:1, s. 89-106
-
Tidskriftsartikel (refereegranskat)abstract
- Fluid flow anisotropy in a single rock fracture during a shear process is an important issue in rock mechanics and is investigated in this paper using FEM modelling, considering evolutions of aperture and transmissivity with shear displacement history. The distributions of fracture aperture during shearing with large shear displacements were obtained by numerically manipulating relative translational movements between two digitalized surfaces of a rock fracture replica, with changing sample sizes. The scale dependence of the fluid behaviour and properties were also investigated using a fractal approach. The results show that the fracture aperture increases anisotropically during shear with a more pronounced increase in the direction perpendicular to the shear displacement, causing significant fluid flow channelling effect, as also observed by other researchers. This finding may have important impacts on the interpretation of the results of coupled hydro-mechanical experiments for measurements of hydraulic properties of rock fractures because the hydraulic properties are usually calculated from flow test results along the shear directions while ignoring the more significant anisotropic flow perpendicular to the shear direction. This finding indicates that the coupled stress-flow tests of rough rock fractures should be conducted in true three-dimensions if possible. Significant change in fracture aperture/ transmissivity in the out-of-plane direction should be properly evaluated if two-dimensional tests are conducted. Results obtained from numerical simulations also show that fluid flow through a single rough fracture changes with increasing sample size and shear displacements, indicating that representative hydro-mechanical properties of the fractures in the field can only be more reliably determined using samples of large enough sizes beyond the stationarity threshold and tested with larger shear displacements.
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| 48. |
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| 49. |
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| 50. |
- Kulatilake, Pinnaduwa H.S.W., et al.
(författare)
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Analysis of structural homogeneity of rock masses
- 1990
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Ingår i: Engineering Geology. - 0013-7952 .- 1872-6917. ; 29:3, s. 195-211
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Tidskriftsartikel (refereegranskat)abstract
- The statistical tests suggested by Miller (1983) and Mahtab and Yegulalp (1984) to investigate structural homogeneity in rock masses are reviewed. The difficulty in making a decision about statistical homogeneity only through the results of either one of these two tests or through equal-area polar plots, is shown through a case study. New interpretations are suggested for these two tests to use them in assigning relative ranks for the strength of homogeneity of different regions in rock masses. An example is given to illustrate how one can use Miller's method with new interpretations along with equal-area plots in making decisions about statistical homogeneity in rock masses. The example also shows an attempt to incorporate results of Mahtab and Yegulalp's test with new interpretations to the decision-making process
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