Boring or penetrating the earth – Common drive or advancing means for concurrently boring...
Patent
1997-03-05
1998-08-25
Schoeppel, Roger J.
Boring or penetrating the earth
Common drive or advancing means for concurrently boring...
175162, 175113, 175220, E21B 700
Patent
active
057974659
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-shaft drilling unit used to develop a continuous wall under the ground.
2. Description of the Related
In an in-situ soil mixing method, subsoil is drilled in a wall-shape and a mixed liquid of cement, and the like, is discharged from an end point of an auger shaft to mix with the in-situ soil to develop a continuous wall and is applied to form cut-off walls in works on retaining walls and shoring in underground works of civil engineering construction and has been widely effectively used.
A multi-shaft auger machine for the development of such continuous wall is explained with reference to FIGS. 18 and 19.
In FIG. 18, a drive unit 103 is equipped to move vertically on a guide post 102 mounted on a crawler truck 101; a multi-shaft unit 104 is connected to the lower part of such drive unit 103; and a plurality of auger shafts (three shafts as shown in the illustrated example) 110A, 110B and 110C, hereinafter referred to collectively as "105" are installed on the multi-shaft unit 104.
A drilling cutter 106 is equipped at the lower end of each auger shaft 105; a screw type movable wing 107 of which the diameter is the same as the drilling cutter 106 and a bar-shaped auger wing 108 are alternately equipped at the upper part of the drilling cutter 106; and each end of the auger wing, next to the other one, is reciprocally working to form a continuous wall unit by mixing in-situ soil with mixed liquid to improve retention and cut-off power by molding H-type steel and sheet pile to the continuous wall, where required.
In the aforementioned conventional multi-shaft auger machine of the prior art, because outer auger shafts 110A, 11OC and a center auger shaft 11OB alternately rotate in the opposing directions respectively to complete the mixture, the rotary reaction force of the drilling cutters 106 is apt to be unbalanced as much as 2:1, and the linearity of such continuous wall unit deteriorates.
In addition, the pitch between auger shafts 105 is limited such as to be required to continue drilled holes by overlapping each rotary range of the drilling cutters 106.
Furthermore, H-type steel is required to be fabricated for each shaft line of the auger shafts.
Still further, in such multi-shaft auger machine shown in FIGS. 18 and 19, a triangular irregularity overlapped by outer rotation loci of the drilling cutters is formed at both longitudinal sides of the continuous wall unit obtained by operating auger shafts. This is an undesirable feature of attainable strength.
There has been disclosed a multi-shaft auger machine, in which the linearity is remarkably good and such that a continuous wall can be developed without any limitation on a position where H-type steel is molded and the pitch between auger shafts is long in Japanese Patent Application Disclosure No. 2-115406. Because chain drive drilling cutters are provided angularly close to the lower ends of the auger shafts of this multi-shaft auger machine which is equipped with a plurality of auger shafts used to develop a continuous wall under the ground, any irregularity can be removed by such chain drive drilling cutters even if any triangular irregularity is formed by overlapping outer rotation loci of such drilling cutters.
According to the prior art disclosed in Japanese Patent Application Disclosure No. 2-115406, however, there is a problem with the linearity of a continuous wall because such machine is not constructed to completely withstand a reaction force, even the rotary reaction force in one direction. Besides, there is the problem of reliability because chains are apt to loosen and breakage or damage may occur.
The object of the present invention is to provide a highly reliable multi-shaft drilling unit to develop a continuous wall of which the linearity is remarkable in consideration of the aforementioned problems involving the prior art.
SUMMARY OF THE INVENTION
The multi-shaft auger machine in the present invention is equipped with a guide shaft on on
REFERENCES:
patent: 3760915 (1973-09-01), Young et al.
patent: 4537536 (1985-08-01), Tsubonuma et al.
Hatakeda Hachiro
Kubo Hiroaki
Mori Akira
Nakamura Tetsuo
Shibasaki Mitsuhiro
Chemical Grouting Company, Ltd.
Schoeppel Roger J.
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