MULTI-SHAFT EXCAVATING DEVICE

Abstract: The present invention provides multi-shaft excavating device for forming a cast in situ diaphragm wall that is capable of forming such a wall of good linearity and is highly reliable. According to the invention, a guide shaft is provided on one or both sides of a plurality of excavating shafts which are linearly arranged and in which a jet nozzle is provided on said guide shaft. A multi-shaft excavating device with three mixing shafts for forming a cast in situ diaphragm wall comprising a first gear adapted to be rotated by the central mixing shaft, a pair of second gears in mesh engagement with said first gear, a first bevel gear that is integral with said first gear, a second bevel gear in mesh engagement with said first bevel gear and fixedly provided on a rotating shaft perpendicular to a straight line connecting the centers of said mixing shafts and cutters provided at the ends of said rotating shaft, all of which are provided in a housing maintaining an interval between said mixing shafts. With the multi-shaft excavating device of the present invention, it is possible to form such a wall of good linearity. Moreover, with the device of the present invention, since the ground is excavated in such a manner as to form a rectangular cross section by a jet stream, it is possible to improve reliability over a conventional excavating blade driven by a chain. Furthermore, with the device of the present invention, it is possible to form such a wall unit of rectangular shape, and since the reaction of the cutters is offset, good balance is obtained, and it is possible to obtain a device of high reliability due to gear driving.

Description: The present invention relates to a multi-shaft drilling unit for use in forming a continuous wall under the ground. An in-situ soil mixing process, in which subsoil is drilled in a wall shape while liquid cement or the like is discharged from an end of an auger shaft to mix with the in-situ soil to form a continuous wall, has been widely used to form cut-off walls or retaining walls and shoring in underground works of civil engineering construction. A known multi-shaft auger machine for use in forming such a continuous wall will first be described with reference to Figures 18 and 19. Referring to Figure 18, a drive unit 3 is mounted to move vertically on a guide post 2 mounted on a crawler truck 1, a multi-shaft drilling unit 4 is connected to the lower part of such drive unit 3, and a plurality of auger shafts (three in this embodiment) 5A, 5B and 5C are provided in said multi-shaft unit 4. A drilling cutter 6 is mounted at the lower end of each auger shaft 5. Screw type blades 7, whose diameter is the same as the drilling cutter 6, and bar-shaped auger blades 8, are alternately located above each drilling cutter 6. The auger blades cooperate reciprocally to form a continuous wall unit by mixing in-situ soil with liquid. H-section steels or sheet piles may be incorporated if necessary. In this known multi-shaft auger machine, the outer auger shafts 5A, 5C and the central auger shaft 5B rotate in opposite directions, to enhance mixing. As a result, the rotary reaction force of the drilling cutters 6 tends to be unbalanced, and this adversely affects the linearity of the continuous wall being formed. In addition, the pitch between the auger shafts is limited, as compared with what is required to drill continuous holes, by limitations on the overlapping of the rotary fields of the drilling cutters 6. Furthermore, as previously mentioned, H-section steels are required to be incorporated in line with the said auger shafts. Also, triangular irregularities are formed between the outer rotation loci of the drilling cutters at both longitudinal sides of a continuous wall unit formed by the auger shafts, which has an undesirable effect on the strength of the wall. The present applicant has previously proposed a multi-shaft auger machine, which can form walls of good linearity and by means of which a continuous wall can be formed without any limitation on the positions where H-section steels are incorporated, and in which the pitch between the auger shafts is long. This machine, which is described in Japanese Patent Application Publication No. 2-115406, incorporates chain drive drilling cutters close to the lower ends of the auger shafts, which avoid the aforementioned triangular irregularities. However, there is still a problem with the linearity of a continuous wall, because this machine does not completely withstand a rotary reaction force working in one direction. Also, there can be a problem with reliability because the chains are apt to loosen. Thus, the object of the present invention is to provide a multi-shaft drilling machine capable of reliably forming a continuous wall of good linearity. JP-B2-59-53999 discloses a multi-shaft drilling apparatus comprising a plurality of parallel drilling shafts arranged in a row with their axes in a common plane, and a guide shaft at at least one end of the said row, parallel to and in the same plane as the said drilling shafts. The present invention is characterised in that jet nozzles are provided on opposite sides of the said guide shaft or shafts, laterally offset on opposite sides of the said plane, the nozzles being directed respectively along the opposite sides of the drilling envelopes of the said drilling shafts, to dislodge material from undrilled areas between said envelopes, in use. US-A-3645101 discloses apparatus in which a jet nozzle is used to dislodge material during the formation of an underground wall. In one form of the invention there is a said guide shaft at only one end of the said row of drilling shafts, said guide shaft having a said jet nozzle on each side thereof. In another form of the invention there is a said guide shaft at each end of said row of drilling shafts, each said guide shaft having a said jet nozzle on each side thereof. In the accompanying drawings: Figure 1 is a front view of a first embodiment of the present invention. Figure 2 is a view of the lower part of Figure 1. Figure 3 is a section view on the line A-A in Figure 2. Figure 4 is a front view of a guide bit. Figure 5 is a section view on the line B-B in Figure 4. Figure 6 is a section view on the line C-C in Figure 4. Figure 7 is a plan view to illustrate a drilling operation. Figure 8 is a front view to illustrate the operation of the apparatus. Figures 9 and 10 are front views to illustrate the operation of the guide bit. Figure 11 is a plan view to illustrate another drilling operation. Figure 12 is a side view of a second embodiment. Figure 13 is a front view of the machine of Figure 12. Figure 14 is a side view showing an auger machine of the prior art. Figure 15 is a front view of the machine of Figure 14. In the following description the same numerals are given to some parts already referred to above with reference to Figures 14 and 15, and a detailed explanation is not given, so as to avoid repetition. Referring first to Figures 1 to 3, a plurality of rotatable drilling shafts (three in this embodiment) 10A, 10B and 10C and a fixed guide shaft 11 are arranged so that all of the shaft centres are located on a straight line L. The drilling shafts 10A to 10C are connected together by interference prevention brackets 12 also serving as bearings. Clamp brackets 13A locked to the guide shaft 11 are connected to the several brackets 12A of the brackets 12. Referring now to Figures 4 to 6, a guide bit 14 is mounted at the lower end of the guide shaft 11. The body 15 of the guide bit is tubular. The part of the body 15 which overlaps with a drilling cutter 6 of a drilling shaft 10A and with the outer rotation locus D of a screw blade 7 (both of which, and the outer diameter R of an auger blade 8, are equal) is formed with a circular concave part 16. A pair of jet nozzles 17, which inject a jet stream J in a tangential direction, are provided on the outer circumference of the body 15 parallel to the centre line L. In a drilling operation, as shown in Figure 7, guide holes H1, H2, etc. are drilled in advance. As shown in Figure 8, guide bit 14 is then inserted in guide hole H1 and holes h1, h2 and h3 are drilled by drilling shafts 10A, 10B and 10C, to drill the subsoil in a wall shape with the aid of the jet streams J. Repeating the same operation in the guide hole H2, further holes h1, h2 and h3 are drilled so as again to drill the subsoil continuously in a wall shape with the aid of the jet streams J. Since the guide holes H1, H2, etc. receive the drilling reaction force of the drilling shaft 10 through the guide bit 14, the linearity of the wall shaped section is good. During this operation, and as shown in Figure 8, the holes are drilled such that the guide bit 14 is lowered further than the drilling cutters 6, by the length L, which may be 500mm-700mm. By this means, the guiding effect of the guide bit 14 is enhanced. In some operations a clamp on the guide shaft 11 can be released at a clamp block 13B so that the guide bit 14 becomes free before the length L showing a scheduled drilling depth is reached. On the other hand, when drilling is done with the guide bit 14 and drilling cutter 6 at the same level in the subsoil as shown in Figure 9, or when drilling is done in such a way that the guide bit 14 is pulled up by a distance D1 (e.g. 300mm to 550mm) above the drilling cutter 6 as shown in Figure 10, release of the clamp on the guide bit 14 as mentioned above will not be required. However, since the guiding ability then slightly decreases, such release is desirable when operating in weak ground. Figure 11 shows another drilling procedure. Here, when a first drilling using guide hole H1 is completed, a second drilling is executed using hole h3 as a guide hole. In this case, linearity is further enhanced and the need for a jet stream J is decreased as compared with the previous embodiment. Figures 12 and 13 show another embodiment of the invention in which shafts 11, 11A are provided on both sides of the drilling shafts 10A to 10C. In use of this embodiment, referring again to Figure 7, guide holes H1, H2 are used simultaneously and jet streams J are oppositely projected from such holes, so that linearity is further improved.

Claims: A multi-shaft drilling apparatus comprising a plurality of parallel drilling shafts (5) arranged in a row with their axes in a common plane, and a guide shaft (11) at at least one end of the said row, parallel to and in the same plane as the said drilling shafts, characterised in that jet nozzles (17) are provided on opposite sides of the said guide shaft or shafts, laterally offset on opposite sides of the said plane, the nozzles being directed respectively along the opposite sides of the drilling envelopes of the said drilling shafts, to dislodge material from undrilled areas between said envelopes, in use. Apparatus as claimed in claim 1, wherein there is a said guide shaft (11) at only one end of the said row of drilling shafts (5), said guide shaft having a said jet nozzle (17) on each side thereof. Apparatus as claimed in claim 1, wherein there is a said guide shaft (11) at each end of said row of drilling shafts (5), each said guide shaft having a said jet nozzle (17) on each side thereof.

Inventors: HATAKEDA HACHIRO, KUBO HIROAKI, MORI AKIRA, NAKAMURA TETSUO, SHIBASAKI MITSUHIRO, TAKAHASHI TSUTAO, HATAKEDA, HACHIRO, KUBO, HIROAKI, MORI, AKIRA, NAKAMURA, TETSUO, SHIBASAKI, MITSUHIRO, TAKAHASHI, TSUTAO, HATAKEDA, HACHIRO,
Applicants: CHEMICAL GROUT CO, CHEMICAL GROUTING COMPANY LTD.
Application year: 1993
Main classification: E02D5
IPC codes: E02D17, E21B7, E02D5