Settlement Monitoring for the University Link Light Rail in Seattle, Washington

摘要

An extensive instrumentation program for the University Link Light Rail, Link Contract U220rnin Seattle, Washington, was successfully implemented to monitor both surface and subsurface movement duernto mining of twin bore tunnels using Earth Pressure Balance Tunnel Boring Machines. This paper describes thernchallenges of instrument installation along the alignment and also highlights the most meaningful monitoringrnresults, including measured ground movements from extensometers installed to depths immediately aboverntunnels and a comparison of measured surface and subsurface movements in two distinct geologic conditions.rnIn both cases, tunneling was in glacially consolidated course-grained non-glacial deposits; however, onernlocation was capped by non-glacially consolidated deposits to the surface, while the other location was cappedrnby glacially consolidated soils to the surface. Settlement measurements and rates of settlement were differentrnin each area, regardless of the tunnel face encountering similar soil types.