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Tunnel Projects
Devil's Slide Tunnels Project
Pacifica, California
Pacifica, California
The present Devil’s Slide Tunnel consists of twin bores in rock,
constructed along Route 1 in Northern California with a 4,000 ft length.
It was the first road tunnel constructed by California Department of Transportation in 40 years.
The tunnel was designed and constructed using a drill-and-blast method.
EMI was the lead geotechnical engineer providing geologic and geotechnical interpretation and design recommendations
for the tunnels, portals, soil nail walls, and spoils disposal site. This project won EMI the 2013 Engineering Project Achievement Award from the Orange County Engineering Council.
Investigation EMI pioneered the effort to conduct a major site investigation program in mountainous terrain and constrained space on Route 1. EMI assisted in preparation of a SWPPP plan to address working in an environmentally sensitive habitat. The investigation required new road grading and helicopter support to gain access to drill timber platforms on steep slopes. Work featured multiple portable limited-access rigs working continuous shifts, deep inclined and subhorizontal rock and soil rotary wash borings, and trenching for geologic fault mapping.
In-hole testing included pressuremeter, packer testing, seismic wave logging, video logging, caliper/deviator logging, and piezometer installations for long-term groundwater monitoring. Work was coordinated from on-site logistics offices and used sample core storage trailers. EMI attended private and public informational hearings. The investigation was fast-paced and under Caltrans inspection and technical Peer Review.
Geotechnical Engineering Design EMI produced a Geotechnical Data Report (GDR), Geotechnical Interpretive Report (GIR), and Geotechnical Baseline Report (GBR). Seismic loading criteria were developed by conducting seismic hazard analyses and developing earthquake-time histories for design of the tunnels and portals.
To assist static and seismic designs of the tunnels, various loading mechanisms on the tunnel support systems were examined including geo-static loading, seismic-induced distortion of the support system, and key block loading. The seismic design procedure is now considered state-of-the-art and has been Peer reviewed and adopted by Caltrans as a standard for road tunnel design.
Investigation EMI pioneered the effort to conduct a major site investigation program in mountainous terrain and constrained space on Route 1. EMI assisted in preparation of a SWPPP plan to address working in an environmentally sensitive habitat. The investigation required new road grading and helicopter support to gain access to drill timber platforms on steep slopes. Work featured multiple portable limited-access rigs working continuous shifts, deep inclined and subhorizontal rock and soil rotary wash borings, and trenching for geologic fault mapping.
In-hole testing included pressuremeter, packer testing, seismic wave logging, video logging, caliper/deviator logging, and piezometer installations for long-term groundwater monitoring. Work was coordinated from on-site logistics offices and used sample core storage trailers. EMI attended private and public informational hearings. The investigation was fast-paced and under Caltrans inspection and technical Peer Review.
Geotechnical Engineering Design EMI produced a Geotechnical Data Report (GDR), Geotechnical Interpretive Report (GIR), and Geotechnical Baseline Report (GBR). Seismic loading criteria were developed by conducting seismic hazard analyses and developing earthquake-time histories for design of the tunnels and portals.
To assist static and seismic designs of the tunnels, various loading mechanisms on the tunnel support systems were examined including geo-static loading, seismic-induced distortion of the support system, and key block loading. The seismic design procedure is now considered state-of-the-art and has been Peer reviewed and adopted by Caltrans as a standard for road tunnel design.