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| | The principles of this system were introduced in ''Tunnelling Activities in Japan 1998'', at a location 2 to 3 m away from the face, the initiator in a charged tube was sent, a command was then made by light signal or wireless for the addition of dynamite, and then tamping by the required amount using the same tube.The charging energy used is the air that is safe. From these experiences of usage, the safety of this work, the initial aim of this system, has been greatly improved, and the workers were released from the previous wearisome work, as well as the blasting efficiency increased due to the closest charging. The method has been introduced to 3 other tunnels, and will find more extensive use. | | (Presented by Kumagaigumi Co.,Ltd.)
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| When adopting mountain tunneling methods in parts of thin overburden coverage and in urban areas, the main task is to minimize ground surface settlements and to strictly reduce the influence on surrounding structures. In particular, settlement of the support leg can be a main cause of ground surface settlement, and the foot pile method is a representative countermeasure that has often been adopted for reinforcing the tunnel base. However, the traditional foot pile method,
Thus, for this method, special machinery with an arcshaped casing and auger is positioned at the tunnel cutting face, and 500mm large diameter mortar piles formed ahead of the cutting face for the support legs, with the aim of reducing settlement. The special feature of this method is that
as the auger is arc-shaped, leg reinforcing piles can be built prior to excavation of the cutting face.
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| | (Presented by Japan Foundation Engineering Co., Ltd.)
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| | The Ventilation Facilities Structural Works of the Imaigawa Underground Reservoir Construction Project are the excavation works for an inclined ventilation shaft connecting the main underground reservoir with a depth of 87m from the shaft The shaft, with an inner diameter of 2,000mm, was built using a slurry shield, with an inclination angle of 75.6 degrees, and under high artesian pressure conditions of up to 0.66MPa at the connection point.
In order to adopt the pipe-jacking method for a near-vertical inclined shaft, which is normally used for the excavation of horizontal tunnels, many devices were required which are described below:
| (1) | The slurry shield machine used for excavation: | _ | Maintain high water impermeablity by a sealing performance up to 1.0 MPa | _ | All-directional spherical surface by an articulation device to control the excavation direction | _ | Upon reaching arrival, the driving device of the shield machine to be parked and divided into two parts, to allow for later dismantling and removal through inside the pipe-shaft and thus shorten the schedule and improve safety | | (2) | Temporary equipment on the ground: | _ | sliding type pipe jacks | _ | fixing equipment by power casing jacks to prevent pipe uplift due to buoyancy | _ | Ground anchor in order to ensure adequate reactions to the two above-mentioned devices | _ | Work elevators for use inside the pipe-shaft |
The inclined shaft excavation method used for this project, as both the costs and construction schedule are favourable compared to constructing a vertical shaft and then excavating a horizontal tunnel from the base of the shaft, could also be used for constructing connecting vertical shafts for ventilation purposes, and also for small scale elevator shafts and the like. | |
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