Tunneling through an operational oilfield and active faults on the ECIS Project, Los Angeles, CA, USA

摘要

A 2.5km (1.8 mile) long tunnel has been driven by a 4.7m (15.5ft) diameter EPB-TBM through sands and gravels of the Lakewood formation and very stiff massive clays and silts with minor occurrences of sand of the San Pedro formation. The Unit 1, western section, of the East Central Interceptor Sewer (ECIS) project tunnels beneath major utility lines with shallow cover, crosses the seismically active Newport-Inglewood Fault Zone beneath Baldwin Hills, and navigates through the Inglewood Oil Fields. The paper describes the hazard assessment and construction considerations of tunneling through faults and outlines risk avoidance planning to avoid abandoned oil wells. The paper then describes the performance of the TBM in the different ground conditions encountered, the forward probing method used to monitor for gas and the search for existing oil wells using a magnetometer both in a probe hole from the tunnel and also from the surface. Procedures are included describing the re-abandonment of an existing oil well discovered elsewhere on the project, and how successful implementation enabled the project to proceed safely.