The stability of rock masses is influenced by the occurrence of rock joints. Therefore, the shear strength of rock joints must be considered in dimensioning of underground constructions. One way to predict the shear strength is through usage of failure criteria, which are validated from results of direct shear tests under controlled laboratory conditions. Consequently, the quality of the results from the tests are crucial to the accuracy with which the criteria will be able to predict the shear strength. Since rock joints are unique by nature usage of replicas (man-made copies of rock joints) is of importance in parameter studies. The overall objective of this work is to facilitate the development of improved criteria for predictions of the shear strength of rock joints. To support this objective, two sources of uncertainty have been investigated, namely the geometry of replicas and the influence of the normal stiffness of test systems. Two quality assurance parameters for evaluation of geometrical differences between replicas and rock joints based on scanning data have been derived. The first parameter describes the morphological deviations. The second parameter describes the deviations in orientation with respect to the shear plane. The effective normal stiffness approach, which compensates for the influence of the normal stiffness of the test system in direct shear testing, has been developed, validated, and applied. With help of the quality assurance parameters it is demonstrated that it is possible to reproduce replicas within narrow tolerances. Application of the effective normal stiffness approach basically eliminates the normal load error. In all, the results support generation of improved quality of test data and consequently, the development of shear strength criteria with improved accuracy will also be facilitated. / <p>Academic Dissertation which, with due permission of the KTH Royal Institute of  Technology, is submitted for public defence for the Degree of Licentiate of Engineering on Wednesday the 9th June 2021, at 9:00 a.m. in M108, Brinellvägen 23, Stockholm.</p><p><strong>Paper A</strong>: Larsson J, Flansbjer M, Portal N W, Johnson E, Johansson F, and Mas Ivars D. (2020) Geometrical Quality Assurance of Rock Joint Replicas in Shear Tests – Introductory Analysis. Paper presented at the ISRM International Symposium - EUROCK 2020, physical event not held. https://onepetro.org/ISRMEUROCK/proceedings-abstract/EUROCK20/All-EUROCK20/ISRM-EUROCK-2020-101/451187  In Diva: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-51987 </p><p><strong>Paper B:</strong> Larsson J, Johansson F, Mas Ivars D, Johnson E, Flansbjer M and Portal N W. (2021) Rock joint replicas in direct shear testing – Part 1: Extraction of geometrical quality assurance parameters. To be submitted to Rock Mechanics and Rock Engineering  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-53111 </p><p><strong>Paper C:</strong> Larsson J and Flansbjer M. (2020) An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests. Rock Mechancis and Rock Engineering 53, 2185–2199 https://doi.org/10.1007/s00603-020-02051-0  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-44085  </p><p><strong>Paper D:</strong> Larsson J. (2021) Experimental investigation of the system normal stiffness of a 5 MN direct shear test setup and the compensation of it in CNS direct shear tests. Submitted to ISRM International Symposium - EUROCK 2021  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-53112 </p>

The stability of rock masses is influenced by the occurrence of rock joints. Therefore, the shear strength of rock joints must be considered in dimensioning of underground constructions. One way to predict the shear strength is through usage of failure criteria, which are validated from results of direct shear tests under controlled laboratory conditions. Consequently, the quality of the results from the tests are crucial to the accuracy with which the criteria will be able to predict the shear strength. Since rock joints are unique by nature usage of replicas (man-made copies of rock joints) is of importance in parameter studies. The overall objective of this work is to facilitate the development of improved criteria for predictions of the shear strength of rock joints. To support this objective, two sources of uncertainty have been investigated, namely the geometry of replicas and the influence of the normal stiffness of test systems. Two quality assurance parameters for evaluation of geometrical differences between replicas and rock joints based on scanning data have been derived. The first parameter describes the morphological deviations. The second parameter describes the deviations in orientation with respect to the shear plane. The effective normal stiffness approach, which compensates for the influence of the normal stiffness of the test system indirect shear testing, has been developed, validated, and applied. With help of the quality assurance parameters it is demonstrated that it is possible to reproduce replicas within narrow tolerances. Application of the effective normal stiffness approach basically eliminates the normal load error. In all, the results support generation of improved quality of test data and consequently, the development of shear strength criteria with improved accuracy will also be facilitated. / Bergmassors stabilitet påverkas av bergssprickor. Bergssprickors skjuvhållfasthet behöver därför beaktas vid fastställandet av vilka laster berganläggningar skall dimensioneras mot. Skjuvhållfastheten predikteras bland annat med hjälp av brottkriterier, vilka valideras med hjälp av resultaten från skjuvtester i kontrollerad laboratoriemiljö. Kvaliteten på resultaten från testerna är därför av avgörande betydelse för med vilken noggrannhet kriterierna kommer att kunna prediktera skjuvhållfastheten. Det övergripande målet med detta arbete är att underlätta utvecklingen av förbättrade kriterier för prediktioner av bergssprickors skjuvhållfasthet. Som ett bidrag till att uppnå detta mål har två osäkerhetsfaktorer undersökts, nämligen geometrin av replikor (kopior) av bergssprickor och inverkan av testsystems normalstyvhet. Två kvalitetssäkringsparametrar för utvärdering av de geometriska skillnaderna mellan replikor och bergprov baserade på skanningdata har tagits fram. Den första parametern beskriver de morfologiska avvikelserna. Den andra parametern beskriver avvikelserna i orientering med avseende på skjuvplanet. Ett tillvägagångssätt med en effektiv systemnormalstyvhet, vilken kompenserar för inverkan av testsystemets normalstyvhet, har utvecklats, validerats och tillämpats. Med hjälp av kvalitetssäkringsparametrarna påvisas att det ar möjligt att reproducera replikor inom snäva toleranser. Genom tillämpning av tillvägagångssättet med en effektiv normalstyvhet kan felet i normallast i princip elimineras. Sammantaget stödjer resultaten framtagning av testdata med förbättrad kvalitet och därigenom underlättas även utvecklingen av skjuvhållfasthetskriterier med förbättrad noggrannhet. / <p>QC 210518</p>