STUDY ON MATERIAL PROPERTIES AND TESTING OF VARIOUS ROCK TYPES, DEVELOPMENT OF INVESTIGATION PROCEDURE AND TEST METHODOLOGY FOR FUTURE PROJECTS

This master thesis aims to provide insight and qualitative information about swelling mechanisms in volcanic rocks, in particular the swelling of rocks related to hydropower water tunnels. Additionally, traditional laboratory methods for determining the main rock material properties controlling swelling behavior are investigated. The rock samples tested are obtained from the Alimit area in Philippines, where The Alimit HEPP is in its feasibility phase. The hope is to provide an enhanced understanding of the swelling potential of the volcanic rocks, and introduce a suggestion on a proper investigation 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 swelling rock sciences. The further work was based on the leading hypothesis on swelling clay minerals (i.e. smectites or similar groups of swelling clay minerals) to be the main cause of tunnel collapses in previous projects. Other explanations, as the swelling of chlorites and 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 the Philippines, 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 which major constructions are planned, was performed. The samples were obtained from the borehole core storage of SN Aboitiz (cooperating partner of SN Power/Statkraft) in Lagawe, Philippines. The main part of the investigation procedure was to obtain information on rock material key properties of the collected samples, by different laboratory test methods. The samples underwent mineralogical analyses, UCS-tests, and different types of swelling tests. Oedometer swelling tests were performed at two different institutes (NTNU and KiT), for comparison of methodology and output. The study has uncovered an unexpected swelling potential of strong, andesitic rock types, despite the lack of swelling clay minerals in the samples tested. The swelling pressure magnitudes are confirmed by repeated tests, and apply on the results obtained at both institutes. The swelling potential is assumed closely linked to the high content of laumontite (zeolite). Content of swelling clay minerals, in particular montmorillonite, ii is detected in other rock types tested. The rock material of these samples are weak and disintegrated, and thus not up to standards for UCS testing. However, the swelling pressure magnitudes are lower in the weak material, compared to the strong andesitic rock. The comparison of the oedometer methodology in operation at NTNU and KiT, uncovered important differences between the two institutes. The deviations apply on both the apparatus used, and the procedures of swelling tests. The differences include the version of the ISRM suggested methods, intern modifications on apparatus and procedures, and intern traditions in how specific points in the ISRM standard is translated in practice. Based on the work performed throughout the investigation, a suggestion on an improved investigation procedure is presented at the end of this thesis