STUDY ON MATERIAL PROPERTIES AND TESTING OF VARIOUS ROCK TYPES, DEVELOPMENT OF INVESTIGATION PROCEDURE AND TEST METHODOLOGY FOR FUTURE PROJECTS
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This master thesis aims to provide insight and qualitative information about swellingmechanisms in volcanic rocks, in particular the swelling of rocks related to hydropowerwater tunnels. Additionally, traditional laboratory methods for determining the mainrock material properties controlling swelling behavior are investigated. The rocksamples tested are obtained from the Alimit area in Philippines, where The Alimit HEPPis in its feasibility phase. The hope is to provide an enhanced understanding of theswelling potential of the volcanic rocks, and introduce a suggestion on a properinvestigation procedure to detect potential challenges at an early stage.The first step in this investigation, was to get an overview of the status quo in swellingrock sciences. The further work was based on the leading hypothesis on swelling clayminerals (i.e. smectites or similar groups of swelling clay minerals) to be the main causeof tunnel collapses in previous projects. Other explanations, as the swelling of chloritesand zeolites, and moisture swelling, were also kept in mind during the investigations.The next step was to survey the project case site, located in the Ifugao province of thePhilippines, to get an overview of the geological and topographical features of the area.Sampling of the assumed most dominating rock types, with focus on regions in whichmajor constructions are planned, was performed. The samples were obtained from theborehole core storage of SN Aboitiz (cooperating partner of SN Power/Statkraft) inLagawe, Philippines.The main part of the investigation procedure was to obtain information on rock materialkey properties of the collected samples, by different laboratory test methods. Thesamples underwent mineralogical analyses, UCS-tests, and different types of swellingtests. Oedometer swelling tests were performed at two different institutes (NTNU andKiT), for comparison of methodology and output.The study has uncovered an unexpected swelling potential of strong, andesitic rocktypes, despite the lack of swelling clay minerals in the samples tested. The swellingpressure magnitudes are confirmed by repeated tests, and apply on the results obtainedat both institutes. The swelling potential is assumed closely linked to the high contentof laumontite (zeolite). Content of swelling clay minerals, in particular montmorillonite,iiis detected in other rock types tested. The rock material of these samples are weak anddisintegrated, and thus not up to standards for UCS testing. However, the swellingpressure magnitudes are lower in the weak material, compared to the strong andesiticrock.The comparison of the oedometer methodology in operation at NTNU and KiT,uncovered important differences between the two institutes. The deviations apply onboth the apparatus used, and the procedures of swelling tests. The differences includethe version of the ISRM suggested methods, intern modifications on apparatus andprocedures, and intern traditions in how specific points in the ISRM standard istranslated in practice.Based on the work performed throughout the investigation, a suggestion on an improvedinvestigation procedure is presented at the end of this thesis.