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    1. Rail

    Is a 16-Mile HSR Tunnel Connecting Palmdale to Burbank Possible?

    March 16, 2016
    The impending construction of California’s High Speed Rail (HSR) project has the Rail Authority carefully weighing alternatives for various segments of the high speed rail system.
    Related To: Mineta Transportation Institute (MTI)

    The impending construction of California’s High Speed Rail (HSR) project has the Rail Authority carefully weighing alternatives for various segments of the high speed rail system. One problem that has stood out has been that of connecting Palmdale with Burbank through the San Gabriel Mountains. Various routes have been proposed, and the length of the proposed tunnel may be as great as 16 miles. Jae-Ho Pyeon, PhD, conducted a desktop study for the Mineta Transportation Institute that compiled information from long tunnels worldwide, including a number that were engineered specifically for HSR trains. The study, Trend Analysis of Long Tunnels Worldwide, created a database that breaks down attributes of successful tunnels around the world, discussing what the trends are for feasibility of long tunnels, the optimal configurations for HSR tunnels that cover significant distances, and what safety features best protect passengers and first responders in case of emergencies. 

    Dr. Pyeon explains that “With advances in tunneling technology, the many long tunnels in use around the world today hold valuable lessons for CHSR, particularly with respect to minimization of ground disturbance and improved passenger and operator safety.”

    The key findings include:

    • Five HSR tunnels of the same length as – or longer than – the proposed Palmdale-Burbank connection have been built, worldwide. Another six are in the planning or construction stages.
    • HSR tunnels have been built that exceed 30 miles; a tunnel longer than 16 miles is considered feasible by world engineering standards.
    • The double-tube, single-track configuration is becoming standard in most areas because it is considered the safest. These are normally connected by cross-passages that assist with maintenance, improve ventilation, and can be used for escape in the event of emergencies. Refuge areas are often included in long tunnels as an added safety precaution.
    • Both tunnel boring machines (TBMs) and conventional tunneling methods (drilling and blasting) are popular for rail tunnel projects. Many projects combine the two techniques. TBM is used because of its higher advance rates, and conventional means are employed in terrains that feature difficult rocks, highly variable rocks conditions, and enhanced risks of water inflow under high pressure.
    • Tunnel excavation spoil management is usually critical in reducing the environmental impact of tunnel construction. 

    The full study can be viewed at http://transweb.sjsu.edu/project/1429.html