METHOD FOR CONSTRUCTING A TUNNEL

Abstract: The known method for constructing a tunnel of the type that a shield tunnelling machine is shoved by means of a concrete lining jack and a shield jack equipped to the shield tunnelling machine with reaction forces received by concrete for lining placed in a space delimited by an inner form assembled within a tunnel bore successive­ ly digged by the shield tunnelling machine, a shield tail and an already placed concrete lining, as well as by the inner form, is improved in order to construct a tunnel main body as a reinforced concrete structure. The improve­ ments exist in that a reinforcing steel cage (13) is mounted to a combined spreader and end form (8a) of the concrete lining jack (8) via, the placed concrete for lining is com­ pressed while the reinforcing steel cage is moved, and thereby the reinforcing steel cage is disposed at a pre­ determined position within the concrete for lining.

Description: BACKGROUND OF THE INVENTION: The present invention relates to improvements in a method for constructing a tunnel. The inventor of this invention proposed, in Japanese Patent Publication No. 54-33656, a method for constructing a tunnel consisting of the steps of assembl­ ing an inner form within a tunnel bore that has been successively digged by means of a shield tunnelling machine, placing concrete in a space delimited by the form, a shield tail and a front surface of an already placed concrete lining, and thereafter shoving the shield tunnelling ma­ chine by means of a concrete lining jack and a shield jack equipped to the shield tunnelling machine with shoving reaction forces received by the placed concrete and the inner form. In a soft ground to which a shield tunnelling method is applied for constructing a tunnel, it is required to employ a reinforced concrete structure to assure safety of the tunnel body structure. Accordingly, upon plactic­ ing the above-mentioned cosntructing method in the prior art, it is necessary to assemble a reinforcing steel cage within the shield tail of the shield tunnelling machine and dispose it at a predetermined position. However, in the shield tail section, a working space is very narrow, the work for assembling the rein­ forcing steel cage becomes complexed, and moreover it is difficult to dispose the assembled reinforcing steel cage at a predetermined position. Furthermore, upon compress­ ing the placed concrete, there is a fear that the rein­ forcing steel cage may be moved or deformed at it becomes impossible to reveal the function of a desired reinforced concrete structure. SUMMARY OF THE INVENTION: It is therefore one object of the present invention to provide an improved method for constructing a tunnel in which a tunnel main body can be constructed easily and correctly as a reinforced concrete structure through a shield tunnelling method of field placed con­ crete lining type. According to one feature of the present inven­ tion, there is provided a method for constructing a tunnel, in which a reinforcing steel cage is mounted to a combined spreader and end form of a concrete lining jack via mount metals, placed concrete for lining is compressed while the reinforcing steel cage is moved, and thereby the re­ inforcing steel cage is disposed at a predetermined posi­ tion within the concrete for lining. Upon practicing the present invention as featured above, a spreader of a concrete lining jack equipped to a shield tunnelling machine is commonly used as an end form, a preliminarily assembled reinforcing steel cage is mounted to the combined spreader and end form via mount metals, by extending the concrete lining jack the reinforcing steel cage is moved to the side of concrete for lining which has been placed in the space delimited by an inner form assembled within a tunnel bore that has been succes­ sively digged by means of a shield tunnelling machine, a shield tail and an already placed concrete lining, the same concrete is compressed by the combined spreader and end form, and the reinforcing steel cage is disposed at a predetermined position within the concrete for lining by adjusting the stroke of the concrete lining jack, whereby a tunnel main body can be constructed as a rein­ forced concrete structure through a shield tunnelling method of field placed concrete lining type. The above-mentioned and other objects, features and advantages of the present invention will become more apparent by reference to the following description of preferred embodiments of the invention taken in conjunc­ tion with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Figs. 1 through 5 are longitudinal cross-section side views showing successive steps in a method for con­ structing a tunnel according to one preferred embodiment of the present invention; Figs. 6 through 12 are detailed partial views showing the same respective steps; Figs. 13 to 16 are partial perspective views showing the steps of mounting and moving a reinforcing steel cage; Figs. 17 and 18 are perspective views respec­ tively showing a mount portion of a reinforcing steel cage to a concrete lining jack; Fig. 19 is a transverse cross-section front view showing a state of arrangement of isolated reinforcing steels; and Figs. 20 through 25 are longitudinal cross-­ section side views showing successive steps in a method for constructing a tunnel according to another preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS: Now description will be made on the illustrated embodiments of the present invention. In Fig. 1, reference numeral (1) designates a shield shell in a shield tunnelling machine, numeral (2) designates a cutter, numeral (3) designates a motor for driving the cutter (2), numeral (4) designates a bulkhead, numeral (5) designates a cutter chamber formed between the bulkhead (4) and the cutter (2), numeral (6) designates a ring girder, numerals (7) and (8) respectively designate a shield jack and a concrete lining jack mounted to the ring girder (6), numeral (9) designates a shield tail section, and numeral (10) designates a concrete lining that was placed between a form assembled within a tunnel bore successively digged by the shield tunnelling machine (1) and a ground. Fig. 1 shows the state where shoving of the shield tunnelling machine has been completed by means of the shield jack (7) and the concrete lining jack (8) with the shoving reaction forces received by an inner form (11) and the concrete lining (10). Figs. 2 to 6 show the states where the respec­ tive jacks (7) and (8) are retracted, and in this state, hook bolts (12) disposed as penetrating through a combined spreader and end form (8a) of the concrete lining jack (8) are left on the side of the concrete lining (10). Subsequently, as shown Fig. 3, a reinforcing steel cage (13) is mounted to the combined spreader and end form (8a) via the hook bolts (12), then the reinforcing steel cage (13) is moved up to a predetermined position by extending the concrete lining jack (8), and the inner form (11) is assembled inside of the reinforcing steel cage (13). Figs. 7 to 10 show the steps of mounting and moving the above-mentioned reinforcing steel cage (13), in which hook bolts (12) are inserted into through-holes (14) in the combined spreader and end form (8a) (See Fig. 7), then nuts (15) are threadedly engaged with the hook bolts (12) and fastened to fixedly secure the hook bolts (12) to the combined spreader and end form (8a), and the reinforcing steel cage (13) is engaged with hook portions at the tip ends of the hook bolts (12) (See Fig. 8). Subsequently the reinforcing steel cage (13) is moved by extending the above-described concrete lining jack (8), then the tip end of the moved reinforcing steel cage (13) is engaged with hook bolts (12) projecting from a rein­ forcing steel cage (13) disposed in the already placed concrete lining (See Fig. 9), and thereafter an inner form (11) is assembled (See Fig. 10). Next, as shown in Figs. 4 and 11, a concrete lining (10) is placed around the outer circumference of the newly assembled inner form (11). Subsequently, as shown in Figs. 5 and 12, the shield jack (7) and the concrete lining jack (8) are extended with the reaction forces received respectively by the inner form (11) and the placed concrete lining (10), and thereby the shield tunnelling machine is shoved until the state shown in Fig. 1 is again established. At this time, a cavity portion (16) formed by the advance of the shield shell (1) is filled with concrete for lining (10), and the reinforcing steel cage moves rightwards as shown at (13′) in Fig. 12 simultaneously with extension of the concrete lining jack (8). During this movement, the reinforcing steel cage (13′) would not be displaced in the lateral position because it moves as guided by the hook bolts (12). In addition, as the rein­ forcing steel cage (13′) is fixedly secured to the combined spreader and end form (8a) via the hook bolts (12), it would not be subjected to a thrust of the concrete lining jack (8), and hence stress or deformation would not be generated in the reinforcing steel cage (13′). After the shoving of the shield tunnelling machine has been completed in the above-described manner, when the nuts (15) are removed and the combined spreader and end form (8a) is retracted, the hook bolts (12) would remain on the side of the concrete lining (10) and the state shown in Fig. 6 is realized. Thereafter, similar steps to the above-described ones are repeated and the reinforcing steel cage is buried in the concrete lining. Figs. 13 to 16 show details of the steps of mounting a reinforcing steel cage (13) to the above-­ described combined spreader and end form (8a) and shoving the same. In the combined spreader and end form (8a) formed in an arcuated shape and having a large number of through-holes (14) as shown in Fig. 13, hook bolts (12) are inserted into the respective through-holes (14) (See Fig. 14), then a reinforcing steel cage (13) is engaged with the hook bolts (12) as shown in Fig. 15, and as shown in Fig. 16 the reinforcing steel cage (13) is supported by hook bolts (12) projecting from a concrete lining (10) by extending the concrete lining jack (8). Fig. 17 shows details of the mount portion of the reinforcing steel cage (3) to the hook bolts (12), a combined spacer and packing (17) is fitted around each hook bolt (12), and thereby leakage of cement paste can be prevented. Fig. 18 shows another example of the mount por­ tion in which a packing (18) is fitted around the hook bolt (12) and a spacer (19) is interposed between the combined spreader and end form (8a) and the reinforcing steel cage (13). Fig. 19 shows the state of arrangement of re­ inforcing steel cages (13) each consisting of a single reinforcing bar as arranged so as to conform to the mode of generation of stresses in a transverse cross-section. More particularly, in the top and bottom portions of a tunnel main body tensile stresses would be generated in an inside portion of a transverse cross-section of the concrete lining (10), whereas in the left and right por­ tions of the tunnel main body tensile stresses would be generated in an outside portion of the transverse cross-­ section, and therefore, the reinforcing bars are arranged so as to effectively reinforce the concrete lining against the respective stresses. Figs. 20 to 25 illustrate another preferred embodiment of the present invention, in which a shield main body consists of a front shield drum (1A) and a rear shield drum (1B), and component parts equivalent to those of the above-described first preferred embodiment are given like reference numerals. Fig. 20 shows the state where shoving of the shield tunnelling machine has been completed, and starting from this state a shield jack (7) is extended with a reac­ tion force received by an inner form (11) to make the front shield drum (1A) advance resulting in the state shown in Fig. 21. During this period, a concrete lining jack (8) extends in synchronism with the shield jack (8) and there­ by holds a predetermined compressing force to a concrete lining (10). Subsequently, the respective jacks (7) and (8) are retracted, and the hook bolts (12) take the state of projecting from the reinforcing steel cage (13) within the concrete lining (10) into the space in front of the concrete surface of the concrete lining (10) (See Fig. 22). Then, a reinforcing steel cage (13) is mounted to a combined spreader and end form (8a) of the concrete lining jack (8) via hook bolts (12) and an additional inner form (11) is essembled (See Fig. 23), and further, as shown in Fig. 24 concrete for lining (10) is placed. Thereafter, as shown in Fig. 25, while the con­ crete for lining (10) is being compressed by the concrete lining jack (8), the rear shield drum (1B) is shoved by the reaction force of the concrete lining jack (8), and thus shoving of the tunnelling machine is completed, resulting in the state shown in Fig. 20. Subsequently, by repeating the same steps as those described above, the reinforcing steel cage is buried in the concrete lining. According to the present invention, in a shield tunnelling method of field placed concrete lining type, a tunnel main body can be constructed as a reinforced concrete structure that is structurally reliable as de­ scribed above, and in this method since it is only neces­ sary to mount a preliminarily assembled reinforcing steel cage to a combined spreader and end form of a concrete lining jack via mount metals, the work of disposing a reinforcing steel cage can be achieved easily even in a narrow space within a shield tail, and if the working space is yet insufficient, it is only required to retract the concrete lining jack by a desired length. Furthermore, upon disposing the reinforcing steel cage within the concrete for lining, the reinforcing steel cage can be disposed at a predetermined position in the axial direction of the tunnel by adjusting the stroke of the concrete lining jack. Still further, since the reinforcing steel cage can be assembled independently of the inner form as guided by the combined spreader and end form of the concrete lining jack within the shield tail, the reinforcing steel cage would not be restricted by the method of assembling the inner form. While a principle of the present invention has been described above in connection to preferred embodiments of the invention, it is a matter of course that many ap­ parently widely different embodiments thereof can be made without departing from the spirit of the present invention.

Claims: 1. A method for constructing a tunnel of the type that a shield tunnelling machine is shoved by means of a concrete lining jack and a shield jack equipped to said shield tunnelling machine with reaction forces re­ ceived by concrete for lining placed in a space delimited by an inner form assembled within a tunnel bore succes­ sively digged by the shield tunnelling machine, a shield tail and an already placed concrete lining, as well as by said inner form; characterized in that a reinforcing steel cage is mounted to a combined spreader and end form of said concrete lining jack via mount metals, said placed concrete for lining is compressed while said reinforcing steel cage is moved, and thereby said reinforcing steel cage is disposed at a predetermined position within said concrete for lining. 2. A method for constructing a tunnel as claimed in Claim 1, wherein said mount metals consists of hook bolts, and said reinforcing steel cage is disposed within said concrete for lining in such manner that said hook bolts partly project from the plane of the placed concrete.

Inventors: KIRITANI, YOSHIHARU, YAMAMOTO, MINORU
Applicants: SATO KOGYO KABUSHIKI KAISHA, YAMAMOTO, MINORU
Application year: 1987
Main classification: E21D9
IPC codes: E21D9, E21D11