The Regional Connector consists of twin underground tunnels approximately 1.9 miles long and more than 50 feet below grade that connect several of Metro’s existing light rail lines to provide better connectivity and more efficient rail service in the downtown area. The twin tunnels were constructed with the use of earth pressure balance (EPB) type tunnel boring machines (TBM). Concrete segment liners were used as primary support of the tunnel excavations which were assembled within the tail shield of the TBM as the shield advanced forward.

Project Highlights:

• 2 Underground Light Rail Tunnels
• 3 Underground Stations
• Cross-over Underground Cavern
• Earth Pressure Balance (EPB) Tunnel Boring Machines (TBM)
• Sequential Excavation Method (SEM)
• Geotechnical Instrumentation Installation and Monitoring Program
• 80 multi-point borehole extensometers
• 50 ground, utility, and building settlement reference points
• 20 inclinometers
• 5 groundwater monitoring wells
• Multiple strain gauges, load-cells, tilt-meters, liquid levels, and crack gauges

Ninyo & Moore provided geotechnical instrumentation monitoring services for this project to help manage risk and liability to the owner due to the tunneling and excavation construction. Ninyo & Moore was responsible for the management, supervision, and oversight of the geotechnical instrumentation installation and monitoring program. This program evaluated ground deformation and associated structural behavior during tunneling, cavern excavation, and station cut-and-cover operations, and provided early warning of adverse ground surface performance. Our services included 1) overseeing the installation, data acquisition, and maintenance of geotechnical instrumentation installed by the Contractor and ensuring conformance with the project’s geotechnical instrumentation specifications; 2) compilation, interpretation and reporting of data obtained through a GIS Web-based data and information management system called iSiteCentralTM for real-time, remote monitoring applications; and 3) review of project-related geotechnical submittals. Geotechnical instrumentation included multipoint borehole extensometers, ground, utility and building settlement reference points, inclinometers, groundwater monitoring wells, strain gauges, load-cells, tilt-meters, liquid levels and crack gauges.

Project Details

Los Angeles Metropolitan Transportation Authority c/o Arcadis

Los Angeles, California