No Rupture Surface Sliding Geo-Technique in Deep Excavation for Static and Especially for Seismic Thrust

Abstract

In the recent literature concerning the multi-propped bottom-up technique Shanghai Metro Stations Excavations, there is evidence of the importance of the disturbance in terms of greater wall horizontal deflections and consequently vertical settlements in the neighbouring, caused by the late long time of open -cut excavation without propping. Here is proposed, theoretical and pragmatic at the same time, a new approach to face the problem of the wall deflections and the related vertical settlements behind the wall. The solution proposed is indeed to impede any formation of the incipient sliding in the active wedge soil rupture surface, by oblique piling crossing over the rupture surface through a longer pile penetration length in relation to the active wedge before any excavation process starts. This piled-construction will then cut to shape the excavation profiles recurring to loss of piles material. This solution is particularly fit for high seismicity prone areas, because of the minor relative loss of per unit length of pile, caused by the greater depth of the rupture surfaces to get and cross over.