Investigating technique for understanding of pre-grouting area in sedimentary soft rocks

Sawada, Sumiyuki; Tokiwa, Tetsuya; Kumagai, Seiya; Minamide, Masashi*

Underground facilities have been excavated in soft sedimentary rocks in the Horonobe area, Hokkaido, Japan. Spring water induced by excavation is a major issue, and therefore it is need to implement the spring water control by pre-grouting before the excavation for the efficient and safety excavation. The flow point needed to inject the grouting had been calculated by using borehole investigation data (e.g., core observations and Fluid Electric Conductivity Logging), and boring for pre-grouting was carried out. As a result, calculated flow points are identical with actual flow points. Therefore, it is quite likely to assess and predict the flow points by focusing on borehole investigation data.