ICONE15-10445 GROUTING METHODOLOGY IN CRYSTALLINE ROCK

Abstract

For this paper, an initial literature review was conducted to investigate the potential applications of grouting technology for geological disposal of high level radioactive waste (hereafter called geological disposal), and the potential grouting material for each application. The results show the necessity of using suspension grout, such as cement-based grout, during excavation work, especially deep underground. Next, the method to achieve highly effective seals in crystalline rock with cement grout is studied. To enhance the sealing quality, cement grout should penetrate into very fine fractures, e.g. less than 100μm aperture. In the case of suspension grout, clogging with grout at the openings of rock fractures, especially fine fractures, tends to occur, which results in poor grout penetration. A laboratory experiment was conducted to investigate the clogging phenomenon; the results suggest that high injection pressures could be effective to prevent clogging. Finally, focusing on pre-excavation grouting for horizontal tunnels in crystalline rock, the effective grout hole patterns for achieving high quality sealing was studied. A series of theoretical calculations for water inflow and cost studies were conducted. The results indicate that a dense arrangement of grout holes in a relatively narrow area around a tunnel section, as practised in the Nordic countries, is favorable in hard crystalline rock.