SUCCESSFUL APPLICATION OF EPB TUNNELING FOR THE DENNY CSO PROJECT, SEATTLE, WASHINGTON

摘要

A 1.89 km-long, 4.5 m-l.D. tunnel was successfully constructed through saturated hard clay, and highly abrasive dense sand and gravel, with groundwater heads ranging from 10 to 20 m. In order to address these conditions, a Lovat earth pressure balance IBM was used, with soil conditioning by foam, water and various polymers. Support was provided by a single-pass segmented concrete lining. Groundwater inflows of 400 to 1,600 lpm at times created challenges for changing cutting tools. Surface settlements were generally less than measurement thresholds, except under very low cover at startup. This project provides a pivotal case study of the successful application of EPBM technology in saturated, abrasive glacial soils and the successful application of soil conditioners.