| 1. |
- Stephansson, Ove, et al.
(författare)
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Nuclear power production in an underground chain
- 1984
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Ingår i: Rock mechanics. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9061912350 ; , s. 1193-1197
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Konferensbidrag (refereegranskat)
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Leijon, Bengt A., et al.
(författare)
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A comparative study between two rock stress measurement techniques at Luossavaara Mine
- 1986
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Ingår i: Rock Mechanics and Rock Engineering. - 0723-2632 .- 1434-453X. ; 19:3, s. 143-163
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Tidskriftsartikel (refereegranskat)abstract
- As part of a comprehensive geomechanical pre-investigation scheme, rock stress measurements were conducted at four locations, representing three different rock types, in the Luossavaara Mine, located within the Kiruna iron ore fields in northern Sweden. Two similar triaxial overcoring techniques, the CSIRO Hollow Inclusion Technique and the LUH Triaxial Technique, were used in a parallel fashion in order to obtain redundant results, but also with the intention of comparing the field applicability of the two methods. The results show that the state of stress is characterized by a sub-horizontally directed maximum stress with a magnitude of about 10 MPa. The agreement in terms of stress results between the two methods was generally good. The study demonstrated that the technical differences between the two devices used were of little significance as compared to the observed, often non-ideal mechanical characteristics of the rock. The latter added considerable uncertainty to the data, regardless of the measuring technique used, and it is therefore concluded that the rock quality is a major factor in the application of any overcoring method. Finally, it was shown that the biaxial test method, which is frequently used for the determination of rock properties in connection with stress measurements, is not always relevant for this purpose.
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| 6. |
- Li, Chunlin, et al.
(författare)
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Analytical models for rock bolts
- 1999
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 36:8, s. 1013-1029
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Tidskriftsartikel (refereegranskat)abstract
- Three analytical models have been developed for rock bolts: one for bolts subjected to a concentrated pull load in pullout tests, one for bolts installed in uniformly deformed rock masses, and one for bolts subjected to the opening of individual rock joints. The development of the models has been based on the description of the mechanical coupling at the interface between the bolt and the grout medium for grouted bolts, or between the bolt and the rock for frictionally coupled bolts. For rock bolts in pullout tests, the shear stress of the interface attenuates exponentially with increasing distance from the point of loading when the deformation is compatible across the interface. Decoupling may start first at the loading point when the applied load is large enough and then propagate towards the far end of the bolt with a further increase in the applied load. The magnitude of the shear stress on the decoupled bolt section depends on the coupling mechanism at the interface. For fully grouted bolts, the shear stress on the decoupled section is lower than the peak shear strength of the interface, while for fully frictionally coupled bolts it is approximately the same as the peak shear strength. For rock bolts installed in uniformly deformed rock, the loading process of the bolts due to rock deformation has been taken into account in developing the model. Model simulations confirm the previous findings that a bolt in situ has a pick-up length, an anchor length and a neutral point. It is also revealed that the face plate plays a significant role in enhancing the reinforcement effect. In jointed rock masses, several axial stress peaks may occur along the bolt because of the opening of rock joints intersecting the bolt.
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| 7. |
- Li, Chunlin, et al.
(författare)
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Design of underground drainage boreholes in foliated formations
- 1996
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Ingår i: Rock Mechanics and Rock Engineering. - 0723-2632 .- 1434-453X. ; 29:2, s. 99-105
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Tidskriftsartikel (refereegranskat)abstract
- The principle for the design of a directional drainage borehole in a foliated formation is such that the borehole is drilled so that it crosses all the interested foliation planes. If the inclination angle of the borehole is not appropriately selected, the borehole might never reach the concerned foliation planes. In other words, there exists a critical inclination angle for the borehole. The borehole is able to cross the concerned foliation planes only at an inclination angle larger than the critical angle. The critical inclination angle depends on the geological structure of the foliation planes as well as the trend of the drift. The method to determine the critical inclination angle is described both graphically and analytically in this paper. A case for design of drainage boreholes in a copper mine, using the developed method, is also presented
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Rao, K. Hanumantha, et al.
(författare)
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Size effect of the mode II fracture toughness of rock
- 1999
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Ingår i: Rock mechanics for industry. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9058091007 ; , s. 1117-1123
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Konferensbidrag (refereegranskat)abstract
- A new method, compression-shear test, has been developed for determining the mode II fracture toughness K (sub IIC) of rock. The effect of the specimen thickness B, the dimensionless notch length a/W as well as the notch inclination angle alpha on the determination of K (sub IIC) has been experimentally studied. The results show that the apparent mode II fracture toughness K (sub c) decreases as B and a/W increase and becomes constant when B> or =70 mm (i.e. cubic specimen) and a/W>0.5. The K (sub c) is almost independent of alpha in the range of 65 degrees -75 degrees . The constant K (sub c) is about 2-3 times that of mode I fracture toughness K (sub IC) and can be considered as the true mode II fracture toughness K (sub IIC) of rock.
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| 12. |
- Rao, Q.H., et al.
(författare)
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Mode II fracture toughness testing of rock
- 1999
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Ingår i: Comptes-rendus / 9 Congrès international de mécanique de roches, Paris, France 1999. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 905809071X ; , s. 731-734
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Konferensbidrag (refereegranskat)
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| 13. |
- Rao, Qiuhua, et al.
(författare)
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Shear fracture (Mode II) of brittle rock
- 2003
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 40:3, s. 355-375
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Tidskriftsartikel (refereegranskat)abstract
- Mode II fracture initiation and propagation plays an important role under certain loading conditions in rock fracture mechanics. Under pure tensile, pure shear, tension- and compression-shear loading, the maximum Mode I stress intensity factor, K (sub I max) , is always larger than the maximum Mode II stress intensity factor, K (sub II max) . For brittle materials, Mode I fracture toughness, K (sub IC) , is usually smaller than Mode II fracture toughness, K (sub IIC) . Therefore, K (sub I max) reaches K (sub IC) before K (sub II max) reaches K (sub IIC) , which inevitably leads to Mode I fracture. Due to inexistence of Mode II fracture under pure shear, tension- and compression-shear loading, classical mixed mode fracture criteria can only predict Mode I fracture but not Mode II fracture. A new mixed mode fracture criterion has been established for predicting Mode I or Mode II fracture of brittle materials. It is based on the examination of Mode I and Mode II stress intensity factors on the arbitrary plane theta ,K (sub I) (theta ) and K (sub II) (theta ), varying with theta (-180 degrees < or =theta < or =+180 degrees ), no matter what kind of loading condition is applied. Mode I fracture occurs when (K (sub II max) /K (sub I max) )(K (sub IIC) /K (sub IC) ) and K (sub II max) = K (sub IIC) at theta (sub IIC) . The validity of the new criterion is demonstrated by experimental results of shear-box testing. Shear-box test of cubic specimen is a potential method for determining Mode II fracture toughness K (sub IIC) of rock since it can create a favorable condition for Mode II fracture, i.e. K (sub II max) is always 2-3 times larger than K (sub I max) and reaches K (sub IIC) before K (sub I max) reaches K (sub IC) . The size effect on K (sub IIC) for single- and double-notched specimens has been studied for different specimen thickness B, dimensionless notch length a/W (or 2a/W) and notch inclination angle alpha . The test results show that K (sub IIC) decreases as B increases and becomes a constant when B is equal to or larger than W for both the single- and double-notched specimens. When a/W (or 2a/W) increases, K (sub IIC) decreases and approaches a limit. The alpha has a minor effect on K (sub IIC) when alpha is within 65-75 degrees . Specimen dimensions for obtaining a reliable and reproducible value of K (sub IIC) under shear-box testing are presented. Numerical results demonstrate that under the shear-box loading condition, tensile stress around the notch tip can be effectively restrained by the compressive loading. At peak load, the maximum normal stress is smaller than the tensile strength of rock, while the maximum shear stress is larger than the shear strength in the presence of compressive stress, which results in shear failure.
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| 14. |
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| 15. |
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| 16. |
- Stephansson, Ove, et al.
(författare)
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Revben i berg
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 17. |
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| 19. |
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| 20. |
- Stillborg, Bengt
(författare)
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Experimental investigation of steel cables for rock reinforcement in hard rock
- 1984
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes a detailed experimental investigation of the mechanical behaviour of fully grouted steel cables used for rock reinforcement in hard rock. An attempt is also made to explain the possible modes of deformation and cable failure, based on observations from the experiments. The behaviour is investigated using pull-out and shear tests. Two mechanically quite different cables, a steel wire rope and a steel strand were tested in the experiments. The cable, types and design are specified in detail, and results from mechanical tests are presented. A cement based grout was used as grouting agent for the cables. Through extensive tests of compressive and tensile strengths, different properties of grout with and without additives are defined. The effect of both the curing conditions and the water segregation are studied. Laboratory scale pull-out tests on cables with short and long embedded lengths were conducted. The tests define what are believed to be important aspects of the mechanical behaviour of a grouted cable. The effect of the embedded length, cable surface properties, curing conditions and grouts with and without additives on the mechanical behaviour of the grouted cables are given. It is shown that the cable surface properties, the curing conditions as well as type of grout significantly effect the pull-out behaviour of the cable. No general correlation between cement grout compressive or tensile strength and bond strength in pull-out tests was established. However, the bond strength increases with increasing compressive strength of grout without additives. The laboratory scale pull-out tests are compared with insitu pull-out tests to establish the validity of the test procedure. It is concluded that pull-out tests should, (unless they are conducted for purposes of comparison) be conducted under in-situ conditions where the results will be applied later, whenever this is possible. Shear tests on the steel wire rope were unsuccessful because the rock blocks, inside which the rope was grouted, failed. The shear tests of the steel strand indicated however high shear loads and large shear displacements before failure of the cable occurred. Failure of cable reinforcement in hard rock is discussed. Here, it is reasonable to assume that cable failure will be a more important factor than failure of the rock, grout or intermediate bonds. Results from further in-situ pull-out tests confirm this assumption. An in-situ test procedure for cables in hard rock conditions is proposed. The stiffness/compliance of a fully grouted cable is defined. However, it is concluded from the pull-out tests that the complete pull-out curve always should be considered, in the interpretation of the pull-out test results. Results of in-situ pull-out tests show that blast induced dynamic loading before pull-out can have a significant effect on the pull-out behaviour of the cable. Borehole / cable diameter ratios were found to have an insignificant effect on the pull-out behaviour of the cable. Finally, the results of this investigation are discussed and recommendations for cable reinforcement in hard rock are made.
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| 21. |
- Stillborg, Bengt L.
(författare)
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Rock mass response to large blast hole open stoping
- 1993
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Ingår i: Excavation, support and monitoring. - Oxford : Elsevier. - 0080420672 ; , s. 485-511
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Presents a case study of the rock engineering investigation based on the activities of the Swedish Mining Research Foundation at the Luossavaara mine. The work, aimed at introducing new technology to the Swedish mining industry had three major components: a geomechanics preinvestigation focusing on methods applicable to mining; rock reinforcement studies for prereinforcement; and an instrumentation and monitoring scheme for observation during mining activities. The chapter details the work with emphasis on mine layout design, including pillar design, design and support of loading level, hanging wall support, and footwall support. The chapter concludes with a series of conclusions derived from the work. -R.Gower
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| 22. |
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| 23. |
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| 24. |
- Stillborg, Bengt
(författare)
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'Rib-in-roc' pre-reinforcement system for large underground openings
- 1980
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Ingår i: Tunnels and Tunnelling. - 0041-414X. ; 12:9, s. 23-37
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Tidskriftsartikel (refereegranskat)abstract
- Before any full-scale excavation takes place under the Rib-in-Rock method, an entry is made in the host rock and rib raises are driven around the proposed opening. These raises are spaced at intervals dependent upon rock quality; an opening in poor rock needs more ribs per length of opening. As the ribs are driven they are used as a site from which competent rock bolting can be carried out. As a rib is excavated, it is filled with reinforced concrete. Finally, after the proposed opening has been reinforced, the displacements are automatically controlled as the opening is being excavated. Using this method, openings with a span of 50-60m and a height of 60-80m can be achieved. This paper summarises the results of a two-and-a-half year research programme, the objective of which was to develop a fundamental understanding of the Rib-in-Roc method. Through the development of a new model technology, namely three-dimensional physical models which powerfully exploit the results of dimensional analysis it has been possible to establish the contribution to both permanent and immediate stabilization of a large underground opening prereinforced by the Rib-in-Roc method. The paper demonstrates that the Rib-in-Rock method is a practical working system of pre-reinforcement
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