ABSTRACT
The Shopping Mall comprises a group of buildings with different types of founda- tions, including shallow footings and deep bell caissons. The new twin bore 7.16 m diameter tunnels for the LA Metro’s Purple Line Extension Section 3 Project, were mined as close as 6m to the closest Mall foundations. Comprehensive 3D numerical models were developed based on different tunnelling volume losses to predict ground deformations in two scenarios: ground treatment (compensation/permeation grouting) vs Tunnel Boring Machines (TBM’s) pressurized closed-face tunnelling only. Mechanized tunnelling using EPB TBM’s proved to be effective, minimizing ground movements both at surface level and the buildings’ foundations, as reported by the extensive geotechnical monitoring data. This paper presents a summary of the EPB TBM parameters that lead to the successful mining under the Shopping Mall and the detailed damage assessment developed prior to mining.
