Drilling and Grouting Works for Pressurised Groundwater Conditions of the Semmering Base Tunnel

Abstract The Semmering Base Tunnel (SBT), with a total length of 27.3 km, is one the leading construction projects Baltic-Adriatic Railway Network. tunnel connects two federal provinces Lower Austria and Styria cuts through eastern part Alps. lot SBT 1.1-Tunnel Gloggnitz characterized by complex geological- hydro-geological architecture containing alternating competent geological structures, major fault zones, corresponding transition zones. There are three main water-bearing formations at 1.1: (a) Karst-prone blocky limestone an initial water pressure 10 bar. discontinuities form highly permeable interconnected joint network significant storage coefficient groundwater table. (b) Massive to dolomite 25 systematic disturbed zones subsidiary structures karst permeable, network. (c) zone base structure marks most challenging area for consolidation- sealing grouting. Weak rocks characterize intense fracturing. However, as subjected high bar, these associated potential flowing ground conditions. Based on overall project requirements, specific drilling- grouting methods materials pre-excavation have been established successfully implemented in process. innovations include Standpipe-Packer substituting conventional steel standpipe, specifically cased drilling system inserts prevent erosion within borehole allow defined In addition, this Grouting-Pipe replaces standard tube-à-manchettes controls flushing while preventers. Finally, combined cement-polyurethane grout mix (Hybrid Grout) was stabilize grout. implementation measures will be discussed detail, their benefits process highlighted.