Keeping the face support in soft ground TBM tunnelling

摘要

Even with decades of experience in soft groundTBM tunneling, the estimation of the necessaryrnface support pressure still is a difficult task. Still too often projects give the impression that the designer wasrnhappy to find a calculation model in a publication and to copy it, but without understanding the theory behindrnit and sometimes not even the very basics of geomechanics. If then there is a problem with either a collapsernor excessive settlements, the necessary experience for this emergency situation is naturally even less than thernexperience for the regular advance. Often critical time is lost during days or even weeks of discussion and whenrnaction is finally taken only the time-consuming and cost intensive options remain.rnMany different ways for the stabilization of the disturbed soil in front of the TBM have been tried over thernyears and most have been found to be problematic if not totally ineffective. While fast action is often helpful tornprevent the situation from becoming worse, the activities must be carried out in the right order and at the rightrntime. Experience has shown that the consulting of external help is often the much more effective way, both costrnand time wise, than trying to solve the problems by trial and error.