ABSTRACT:
Face stability of microtunnelling TBMs is an important aspect for a safe and
controlled project execution. Lack of proper face support can lead to
sudden collapse with resulting large settlements. Guidelines for minimal and
maximal support pressures in most codes do not take the infiltration of
bentonite suspension in coarser soils into account. Infiltration lowers the
effectiveness of the face support. In loose sands infiltration can lead to
excess pore pressures and induce liquefaction, with possible catastrophic
consequences. This paper investigates the influence of infiltration and
gives some guidelines for a proper selection of bentonite suspensions based
on soil gradation.
