ABSTRACT
As part of a highway construction in mid-Norway, a tunnel with rock overburden of approximately 4-6 m was established close to a sensitive quick clay slope. Due to the adjacent railway, a relatively strict leakage requirement of 10 l/min/100 m demanded systematic pre-excavation grouting. The stability of the clay slope was below the national requirements. To avoid further decrease of the level of safety of the slope, the risk of increasing the pore pressure in the soil due to grouting was assessed. Limit values for maximum pore pressure in the slope were defined. Live monitoring of the pore pressure response enabled immediate adjustments of the grouting procedure. This paper presents the proposed limits for pore pressure, and the grouting strategy to keep the pore pressures below such limits. Then, the relations between the measured pore pressure response in the soil and the grouting parameters affecting such pore pressures are discussed.
