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| | The TBM has an overall length of 17.83m, a weight of 350 t and a machine diameter of 6.82m. The cutter head face plate has 48 pieces of 17 inch roller cutters, and has a maximum turning speed of 6 revolutions per minute. The gripper reaction is 35,000 kN and the overall thrust force of the machine is 15,000 kN. Equipment for applying shotcrete and installing rock bolts mounted on the working platform which is attached to the rear of the TBM. Furthermore, when 8 rear wagons with the shotcrete plant and dust collector etc. are connected, the total length becomes 103.3m. | | |
On the ground conditions, from the start point there were mainly andesite type rocks, and near the end point plagioclase porphyry with a layer of andesite type rock in between. In the andesite type rocks section, it was confirmed that sills of porphyrite and andesite had intruded, and that these intrusions occurred almost in the same era of the penetration of the plagioclase porphyry.
Close to both portals, uncoagulated deposits of talus, mudflow deposits, terraces deposits, loam layers etc., cover the base rock. Although both tunnel portals pass through the uncoagulated layer, it was expected that apart from these parts the tunnel would pass through relatively sound rock, The tunnel coverage varied from a minimum of 6m to a maximum of 350m. As for recent the construction progress, from January 2003 the TBM departure shaft was excavated 180m by mechanical excavation, and from September 2003 TBM excavation started. Tunnel breakthrough is expected in the spring of 2005 | | (Presented by East Japan Railway Co.)
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| Case of Shimizu No. 4 Tunnel
Recently, with increasing tunnel length and increasing speed in construction, and furthermore with ongoing sharpening curves using underground U-turns, there is an increasing need for more efficiency in the facilities for mucking. The belt conveyor systems used until now (where mucking work by belt conveyor is carried which can be extended by the belt conveyor system), can work well in straight lines or along gentle curves, but is not suitable for work along sharp curves. For the Shimizu No. 4 Tunnel (radius 30m, 180 degree U-turn suited continuous belt conveyor system) a sharp curve method was developed for use, and an outline is given on the results it achieved.
The tunnel is situated mainly in the Shizuoka Fault group (mainly sandstones predominating with sandstone and mudstone alternating strata) in which tertiary sedimentary rocks which are widely distributed. The unconfined compressive strength is around 50-170 N/mm2 maximum, which is rather high for tertiary sedimentary rocks.
This tunnel was excavated using the TBM pilot tunnel and enlarged excavation method, with the TBM pilot tunnel as a top heading ahead of the main excavation by NATM. The Nagoya-bound carriageway starting at the Tokyo side was excavated using NATM pilot tunnel methods, then made a U-turn before the Nagoya side portal (inside the mountain) and then went back-excavating the Tokyo-bound carriageway returning to the Tokyo side portal.
For the tunnel excavation for the New Tomei by TBM for the sharp 30m radius U-turn, transportation of the excavated soil would normally require rails and mucking cars. For improving the environment inside the tunnel and also for making a quicker and more economic construction, the method of using a continuous belt conveyor instead of sliding wheels was employed for the transportation of excavated soil.
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| | (Presented by Japan Highway Public Corporation)
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