Large-Scale Field Investigation of Grouting in Hard Jointed Rock

During the construction of the rock tunnels at the South Link, Stockholm, Sweden, grout investigations were carried out. The aim was to develop alternative methods/concepts for sealing of tunnels compared to the methods/concepts described in the contract. The investigation started with a laboratory study, which outlined the most appropriate grouts for field trials. The field trials consisted of seven grout fans. The front of each fan was divided for equal pumping test values, and grouted with different concepts. The sealing result and the spreading of the grout were studied in 10 holes in the tunnel front and in 10 holes perpendicular to the tunnel. The holes were test pumped and studied with a borehole camera. From the investigation it was concluded that regardless the maximum grain size of cement (9.5, 16 or 30 μm) fine joints (< 100 μm) were still unsealed after grouting. In open joints or rock masses (>1 Lugeon) there was some indications that micro cement was more effective than the more coarse cement type. Higher stop pressure did not give a better sealing result and some parameters achieved at laboratory especially for micro cements were not possible to reproduce with ordinary field mixers.