Abstract:

To investigate the advantages and disadvantages of the new doubleshield open tunnel boring machines(TBMs) and compare them with the conventional mainbeam open TBMs, a case study is conducted on Beijiang water diversion project and Nabang hydropower station project bored by the two open TBMs. First, theoretical comparative analysis is conducted from the aspects of the main machine structure, rock support equipment layout, and construction advantages and disadvantages. Second, engineering application comparison is performed from the aspects of utilization rate of excavation time, construction speed, and geological adaptability. The results show the following: (1) Construction speed of both the TBMs is almost the same when tunneling in complete or relatively complete Grades Ⅱ and Ⅲ surrounding rocks. (2) For surrounding rocks of Grades Ⅳ and Ⅴ or fault fracture zones, the construction speed and adaptability of the doubleshield TBMs are comparatively poor. Therefore, the doubleshield open TBMs are recommended to be employed in smalldiameter tunnels with complete or relatively complete surrounding rocks or less fault fracture zones and tunnels with small curvature radius.

Key words: doubleshield open TBM, mainbeam open TBM, tunneling performance, adaptability