The left line of Dailing Tunnel is lately completed using the earth pressure/TBM double-mode boring machine, which was manufactured jointly by China Railway 17th Bureau and CRCHI. The intended tunnel is a section of the Fuzhou Binhai Expressway, and is the first tunnel completed for the Fuzhou Binhai Expressway project, so it is a significant point for commencing the construction of the project.
While the Dailing Tunnel has1488m length, the ground type of this tunnel includes both soft soil and extreme hard rock ground and its maximum compressive strength is 200MPa. In order to suit the complicated changes in geology, the equipment comprises of both earth pressure mode and TBM mode and can not only meet the needs of rapid long-distance tunnelling of hard rock, but also meet the tunnelling requirements of complex strata including soft soil, soft rock and upper soft and lower hard rock. Due to the flexible and safe switching of the two modes quickly, following simple component adjustment, the equipment input cost is almost decreased.
Usage of the dual mode TBM EPB is particular for underneath pass structures such as foreign language school and available railway line. The section of hard rock was commenced after digging more than 100 m, so the transformation of EPB mode to TBM mode was completed safely and quickly. While the maximum efficiency of the machine footage has been 27m per a day, the maximum monthly footage is 389m.
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