Stability assessment of underground parking cavern in Hammerfest
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This thesis addresses in detail the stability of the planned parking cavern inHammerfest. It includes a review on recognized literature of support design forunderground constructions, frost issues in tunnels, water inflow and mitigation,numerical modelling, and general stability of underground caverns. Studying the localand regional geology reviled that the rock mass is mainly composed of gneiss, withsome small amount of quartzite. The rock mass is expected to be strong (RMR>60,Q>10) but encountering a zone of weak rock mass(Q<0.01) is anticipated. Two cases ofunderground facilities in Norway are reviewed with emphasis on key experiences,support requirement, and monitoring. Support needed for the Hammerfest parking cavern is suggested by analytical,empirical approaches. Finalized rock support measures are quantified and tested withnumerical modelling. The cavern is expected to be sufficiently supported with rockbolts and shotcrete. However, if weak rock is encountered, reinforced shotcrete archesand spiling bolts will be needed. Kinematic assessment is carried out identifying possible failing wedges in the roof andwalls. Leakage of water is discussed and consequences of draining surface ponds areevaluated. Some leakage is expected in the cavern based on field observationshowever, levels are generally anticipated as dripping. Ahead-of-face investigations areconcluded necessary to identify possible high water conduction near the weak rockmass zone. There will be need for grouting should the water leakage exceed quantifiedlimits given in the thesis. Frost intrusion to the cavern is modelled and discussed. It has been recognized thatfrost will enter the cavern and sufficient mitigation is suggested.