The Eşme-Salihli railway tunnel is a short section of high-speed railway, measuring 3.05km through mixed conditions. Contractor Kolin Construction conducted 15 core drillings at 200m intervals prior to the start of construction, with results predicting occasional groundwater and weak rock between 5-9MPa UCS, with the potential for a gassy environment. Rock and soil types included sections of gneiss, sandstone, claystone, mudstone, quartzite, and silt.

A dual-mode rock/EPB TBM design was created by Robbins for the project, in which no design elements were sacrificed in the engineering. The machine was fully capable of operating in 100% EPB mode or 100% hard rock single shield mode. The TBM was designed for sections of hard rock and mixed ground, in highly variable conditions.

While some of the crossover features on the 13.77m Crossover XRE machine proved beneficial, the TBM was able to utilise the screw conveyor for mucking for the complete tunnel drive, which was a further benefit for the project's overall schedule.

Large diameter, dual mode rock/EPB machines can and will excavate mixed ground conditions efficiently - even at world record rates. While similar projects in Turkish geology have met with challenges, the Esme-Salihli tunnel shows that with proper maintenance and a knowledgeable crew, equipment downtime can be kept to a minimum and advance rates can remain high.

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