Traditional and Specialty EPB TBM Soil Conditioners used on the N125 Project in Seattle, WA – Experiences with a novel Encapsulated Oil Additive

摘要

Soil conditioning is one of the main factors in successful application of EPB machines in tunneling, which involves changing the characteristics of the ground in order to make it suitable for the tunneling process. Conditioning surfactant suppliers often provide guidelines for the selection of surfactant and conditioning parameters that are mainly based on lab tests. The analysis of the data from the N125 contact (part of the Northgate Link Extension project) shows that observational methods should be used in addition to these provided guidelines. The soil conditioning program needs to be adjusted on site to address the specific ground conditions encountered. In certain cases, traditional soil conditioners, like foam and bentonite slurry, are not sufficient to achieve the desired performance and specialty soil conditioners like Encapso have to be used. The twin tunnels of the N125 experienced plugging issues while mining through dry sand. The novel algae-based encapsulated oil Encapso was successfully used to improve the TBM performance in this challenging ground.