North American Trends and Developments of Complex Support of Excavation Systems

Abstract

Foundation and tunneling projects often require complex support of excavation (SOE) systems. Application of conventional shoring with sheet pile, soldier pile or soil nail walls can be limited by excavation depth, challenging ground conditions and high groundwater levels. Recently completed support of excavation systems, including Seattle’s Alaskan Way Viaduct Replacement and the Port of Miami Tunnel required shoring in extremely difficult conditions. Innovative ground improvement techniques were combined with traditional shoring methods on a massive scale to provide integrated lateral support and groundwater control for these projects. Powerful state-of-practice specialty foundation equipment was used to construct blocks of low permeability soil for safe-havens, emergency cross passages and the tunnel boring machine break in/out plugs. In situ mixing tools were advanced through variable, highly porous limestone formations. Large diameter secant pile walls, installed through extremely difficult ground conditions with running sands, wooden debris and cobbles and boulders, provided the support for the Tunnel Boring Machine launch and retrieval portals. Creative support of excavation solutions made practical by the most modern equipment and tooling made these cutting edge projects feasible and cost effective.