Face stability conditions with earth-pressure-balanced shields

摘要: Abstract Earth pressure balanced shields provide continuous support to the tunnel face using freshly-excavated wet soil, which under completely fills up work chamber. EPB-shield tunnelling has been successfully applied worldwide in recent years. Under extremely unfavourable geological and hydrogeological conditions, however, instabilities may occur. In this paper, mechanism of failure is analysed drained conditions. Accordingly, a distinction made between water-pressure effective The stability controlled through combined effects these two entities. can be visualized as “grain grain” contact muck ground at face. water chamber reduces hydraulic head gradient and, consequently, seepage forces acting front thus stabilized both by direct pressurized reduction ground. greater head-difference chamber, higher will have be. A high has, on other hand, operational disadvantages such excessive cutter wear, torque etc.. It great practical interest investigate quantitatively relationships required for given geotechnical situation. contribution, normalized diagrams are provided allow assessment stability.