Hydraulic and earth engineering – Underground passageway – e.g. – tunnel – Boring
Patent
1991-10-04
1993-01-19
Taylor, Dennis L.
Hydraulic and earth engineering
Underground passageway, e.g., tunnel
Boring
299 33, 405138, 405141, E21D 908
Patent
active
051802520
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a shield-type, underground tunneling process in which the excavated soil is improved and is utilized for effecting shielding of the excavation against the underground pressure of the earth being excavated, particularly to the shield excavation of earth which exerts a high hydraulic pressure on the working face of the excavation, that is, the face of the excavation that is contacted by the cutter.
DESCRIPTION OF THE PRIOR ART
In a conventional shield-type underground tunneling process, in which the working face is stabilized by maintaining pressurized, fluidized, excavated soil in contact with the working face of the excavation. Such a process is hereafter referred to as a soil pressure-type shield process. The following problems because an excavation additive is added at the time of excavation for imparting fluidity and viscosity to the excavated soil. pressure, the excavated soil and the pressurized ground water are apt to jet from the discharge port of the screw conveyor which is used for discharging the excavated soil, thereby disturbing the earth adjacent to the shield machine. This is liable to cause subsidence or collapse of the earth around the excavation site. truck or the like outside the shield construction site due to its high fluidity, it was necessary to improve the excavated soil to eliminate the fluidity therefrom at the shield construction site.
When the excavated soil is jetted from the discharge conveyor, the pressure variation at the working face is restricted to a minimum by providing a rotary valve and the like at the soil discharge port. However, when the hydraulic ground water pressure ranges 2 to 3 kg/cm.sup.2, the shield excavation cannot be carried out in the soil pressure-type shield process, but rather, it can be carried out by a muddy water pressure-type shield process. Accordingly, a system other than the soil pressure-type shield process, such as the muddy water pressure-type shield process can be employed.
In order to improve the excavated soil having high fluidity, a soft mud improving agent is added to and mixed with the excavated soil at the shield excavation site so as to eliminate the fluidity.
It is an object of the present invention to provide the soil pressure-type shield process capable of solving such drawbacks described above. The invention makes it possible to excavate soil having high hydraulic pressure without resorting to the large scale and troublesome muddy water pressure-type shield process.
SUMMARY OF THE INVENTION
To achieve the above objects, the soil pressure type shield process for underground tunneling comprises the steps of adding an excavation additive comprising a mixture of (1) an agent for improving the fluidity and viscosity of an excavated soil and (2) a mud-improving main agent, to the excavated soil at the time of shield excavation at the working face, and further mixing the excavated soil and the excavation additive inside the mixing chamber of the shield machine and inside the soil conveying screw conveyor to sufficiently mix the excavated soil with the mud-improving main agent, then adding (3) a mud improving assistant inside the soil discharge screw conveyor so that the excavated soil is improved to become a high quality soil inside the soil conveying screw conveyor. As a result, the excavated soil can be mixed with the excavation additive and improved sufficiently even if a shield machine having a small diameter is employed. The improved, high-quality soil is continuously conveyed toward the rear end of a conveying screw conveyor by a screw provided in the conveying screw conveyor and a mixing screw conveyor and is filled under high pressure into the rear end of the conveying screw conveyor. A cut-off plug zone is formed by a cylinder portion having no soil and gravel conveyor means, which cylinder portion is disposed at the rear end of the conveying screw conveyor. As a result, the soil pressure-type shield process, according to the present invention, makes it possible to use the s
REFERENCES:
patent: 3334945 (1967-08-01), Bartlett
patent: 3830545 (1974-08-01), Sugden
patent: 4165129 (1979-08-01), Sugimoto et al.
patent: 4848963 (1989-07-01), Babenderetde et al.
patent: 4915541 (1990-04-01), Thompson et al.
Kobayashi Ryoji
Tanaka Hiroshi
Kabushiki Kaisha Komatsu Seisakusho
Kabushiki Kaisha Konoike Gumi
Taylor Dennis L.
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