Underpassing of Angel Underground by London Ring Main Extension Tunnel

Abstract

This paper presents the predictions of movements, monitoring methods and measured movements of the Angel Station Upper Escalator and the Northern Line London Underground tunnels during tunnelling for the Thames Water Ring Main Extension Stoke Newington to New River Head (TWRM) tunnel. The earth pressure balance tunnel boring machine was driven from a launch shaft in Stoke Newington in an approximately southerly direction to a reception shaft in Islington, at depths of between 40 and 60 m. Along its route, the TWRM passed near to the Upper Escalator of Angel London Underground station, the longest escalator in western Europe, and soon after passed underneath two operational and one disused Northern Line tunnels. No discernible tunnel-induced movements of the escalator were observed. The measured movements of the tunnels were within the conservative expected value predictions of volume loss, but the trough widths were consistently narrower than expected.