EPB excavation in transitional mixed face: Line 5—Lilac (São Paulo Metro, Brazil)

Abstract

The use of Earth Pressure Balance (EPB) shields is still very modest for tunneling in urban areas in Brazil. This study analyzed and integrated geological data and excavation parameters of a segment of Route 2 (Lot 3) of the Line 5—Lilac (São Paulo Metro), between Campo Belo Station and Jesuíno Maciel Shaft. This segment is 557 m long and represents one of the first experiences on tunneling in transitional mixed face with pressurized shield machines in Brazil. The excavation performed an average advance rate of 7.7 m/day and intercepted different proportions of gneisses, saprolites, and residual soils. The results show how the excavation parameters respond to different geological materials. The sections excavated in mixed transitional ground conditions had several negative effects on the excavation process, similarly to that described in other projects worldwide. Finally, results also suggested the nominal torque was insufficient for excavation of the segment.