Face Stabilization Methods for Excavating Unconsolidated Soil Ground with High Groundwater Level

Abstract

This paper reports the face stabilization measures used for the tunnel running under the diluvium upland. The geology comprises sand, volcanic ash silt and cohesive soil. Since the groundwater level is high, deep wells are dug. On the other hand, as the measures for tunnel excavation in unconsolidated ground, the crowns are reinforced by forepiling or the AGF (forepiling with injection). These measures had been devised continuously, in response to the change of the face condition such as the water flow from face and the appearance of a sand layer with a small coefficient of uniformity in the crown.