JP2013028898A - Construction method of invert, invert and precast member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of an invert, for suppressing floating and falling of an invert configuration part due to a pressure from natural ground and achieving excellent workability, the invert, and a precast member.SOLUTION: In the construction method of an invert 15 of a tunnel 1 by an NATM tunnel construction method, the invert 15 comprises precast plates P1-P3 connected in a width direction of the tunnel 1 on a tunnel bottom surface 19. The invert 15 includes the precast plate P1 having both ends with an L-shaped cross section, and the precast plates P2, P3 having an end connected to the end of the precast plate P1 by a half-lap joint with an inverted L-shaped cross section. The construction method includes: a first installation step of installing the precast plate P1 at a prescribed position of the tunnel bottom surface 19; a second installation step of installing the precast plate P2 adjacently on one side of the precast plate P1, and connecting the ends with each other by the half-lap joint; and a third installation step of installing the precast plate P3 adjacently on the other side of the precast plate P1 and connecting the ends with each other by the half-lap joint.

Description

  The present invention relates to a tunnel inversion method, an invert, and a precast member by a NATM tunneling method.

  Conventionally, in the construction of tunnels, the NATM tunneling method (New Austrian Tunneling Method) in which a steel arch, a shotcrete, and a rock volt are used to form a ground arch for the excavation mine is used frequently. The external pressure (external force) applied to this type of tunnel from the ground is mainly the force from above, so in the ground where the geology is relatively good, a steel support is built on the excavation bottom. The upper support is completed by spraying and driving a lock bolt. However, in the ground where the geology is poor, problems such as increased lateral pressure acting on the tunnel, lateral pressure, insufficient support force at the legs of the upper support, etc. occur, causing deformation and displacement in the tunnel's empty cross section. There is. As a countermeasure, it is necessary to invert the bottom of the tunnel, join the upper support at the lower part, close the cross section, and structurally stabilize the tunnel.

  As a technique related to inversion, a tunnel construction method described in Patent Document 1 below is known. This construction method is to install an invert that communicates between the side walls of the tunnel under construction. An arch-shaped primary support work was placed on the periphery of the tunnel exposed by excavating natural ground, and multiple blocks were placed in contact with each other on the bottom surface of the tunnel with adjusted irregularities, and both ends of the primary support work were connected. Build inverts. In this type of invert, a force that pushes up the invert from below may be applied due to external pressure from the natural ground. In order to prevent the block from being lifted or dropped by such force, it is proposed in Patent Document 1 that the blocks are engaged with each other.

JP 2005-179914 A

  However, when the blocks are engaged with each other as described above, the installation work of the blocks becomes difficult and the workability is lowered. For example, when installing the last block, it is difficult to insert the last block between the blocks, and workability is poor. During the construction of the invert, there is a case where it is necessary to restrict the passage of the tunnel excavation vehicle. Therefore, when the workability is lowered and the work time is prolonged, there is a problem that the efficiency of the tunnel excavation work is lowered. Therefore, when making invert into a block, good workability is desired while having a structure that resists pressure from the natural ground.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an invert construction method, an invert, and a precast member that suppress the lifting and dropping off of the invert components caused by the pressure from the natural ground, and realize good workability.

  The invert construction method of the present invention is a method of connecting the legs of the arch-shaped primary support having steel support, sprayed concrete, and rock bolts in the NATM tunnel method to form a convex arch shape below. An invert construction method for constructing the bottom of a tunnel, wherein the invert is composed of a plurality of precast plates connected in the width direction of the tunnel at the bottom of the tunnel, and the invert is provided with a notch so as to have an L-shaped cross section. A first precast plate having both ends, and a second precast plate having an end portion provided with a notch so as to have an inverted L-shaped cross section and connected to one end portion of the first precast plate by a phase notch And a notch provided so as to have an inverted L-shaped cross section, and an end connected to the other end of the first precast plate by a phase notch. A first precast plate installed at a predetermined position on the bottom surface of the tunnel, and adjacent to one side of the first precast plate installed at the predetermined position. The second pre-cast plate is installed, and the end portions of the first and second pre-cast plates are connected to each other by a phase joint, and the second pre-cast plate is adjacent to the other side of the first pre-cast plate installed at a predetermined position. And a third installation step in which three precast plates are installed and the ends of the first and third precast plates are connected to each other by phase cuts.

  In this construction method, invert is formed by a plurality of precast plates connected in the width direction of the tunnel. Since the end of the first precast plate has an L-shaped cross section and is connected to the second and third precast plates by a phased joint, the end of the first precast plate is connected to the second and third precast plates. The first to third precast plates are firmly connected to the end portions. With this structure, even when the first to third precast plates receive a force from below due to the pressure from the natural ground, the precast plates are prevented from rising and falling. In this construction method, the first precast plate is first installed, which is a precast plate other than the precast plate adjacent to the primary support leg (the precast plate constituting the end of the invert), and then the first precast plate. The second and third precast plates are installed while overlapping the end on the end. Therefore, even when the end portions of the precast plates are fitted and connected by phase cuts, the second and third precast plates can be easily installed, and good workability can be ensured.

  In the invert construction method of the present invention, the number of precast plates connected in the width direction to form inverts is an odd number, and the first precast plate is arranged at the center among the plurality of precast plates. Also good. It is considered that the central part of Invert acts most greatly on the force from below due to the pressure from the natural ground. Therefore, by using the central precast plate as the first precast plate having the above-described configuration, it is possible to effectively prevent the precast plate from being lifted or dropped due to the pressure from the natural ground.

  The invert of the present invention is an invert that connects the legs of an arch-shaped primary support having steel support, sprayed concrete, and rock bolts in the NATM tunnel method, and forms a convex arch shape below, A plurality of precast plates connected in the width direction of the tunnel at the bottom surface of the tunnel, and a first precast plate having both ends provided with notches so as to have an L-shaped cross section, and an inverted L-shaped cross section. A second precast plate having a notch and an end connected to one end of the first precast plate by a phase notch, and a first precast plate having a notch so as to have an inverted L-shaped cross section And a third precast plate having an end portion connected to the other end portion by a phase notch.

  This invert is formed by a precast plate connected in a plurality in the width direction of the tunnel. Since the end of the first precast plate has an L-shaped cross section and is connected to the second and third precast plates by a phased joint, the end of the first precast plate is connected to the second and third precast plates. The first to third precast plates are firmly connected to the end portions. With this structure, even when the first to third precast plates receive a force from below due to the pressure from the natural ground, the precast plates are prevented from rising and falling. In addition, when constructing this invert, the first precast plate that is a precast plate other than the precast plate adjacent to the primary support leg (the precast plate constituting the end of the invert) is first installed, and then What is necessary is just to install a 2nd and 3rd precast board, overlapping an edge part on the edge part of a 1st precast board. Accordingly, even when the end portions of the precast plates are connected to each other by phase-separation, the second and third precast plates can be easily installed, and good workability can be ensured.

  The precast member of the present invention is at least one of the inverts having a convex arch shape by connecting the legs of the primary support arch shape having a steel support work, a sprayed concrete part and a lock bolt in the NATM tunnel method. The invert is formed of a plurality of precast plates connected in the width direction of the tunnel at the bottom surface of the tunnel, and has two end portions provided with notches so as to form an L-shaped cross section. 1 precast plate, a second precast plate having a notch so as to have an inverted L-shaped cross section, and an end connected to one end of the first precast plate by a phase notch, and an inverted L-shaped cross section A third precast plate having a notch and an end connected to the other end of the first precast plate by a phase notch, Characterized by comprising.

  According to the present invention, it is possible to provide an invert construction method, an invert, and a precast member that suppress the lifting and dropping off of the invert components caused by the pressure from the natural ground and realize good workability.

It is sectional drawing which shows an example of the mountain tunnel to which the construction method, invert, and precast member of the invert of this invention are applied. (A), (b), (c) is sectional drawing which shows the precast board P1, P2, P3, respectively. (A), (b) is sectional drawing which shows the edge part vicinity of the precast board P1, P2 before a connection, respectively after a connection, respectively. It is sectional drawing which shows the other example of the connection structure of the precast board P1, P2. (A), (b), (c) is sectional drawing which respectively shows the 1st, 2nd, 3rd installation process of the construction method of the invert concerning 1st Embodiment. It is sectional drawing which shows the connection structure of the leg part of a primary support work, and the edge part of the precast board P3. (A), (b), (c) is sectional drawing which respectively shows the construction method of the invert concerning 2nd Embodiment. (A), (b), (c) is sectional drawing which respectively shows the construction method of the invert which concerns on 2nd Embodiment after FIG. It is sectional drawing which shows the other example of the mountain tunnel to which the construction method of an invert of this invention, an invert, and a precast member are applied.

  Hereinafter, embodiments of an invert construction method, an invert, and a precast member according to the present invention will be described in detail with reference to the drawings. First, an invert construction method, an invert, and a mountain tunnel 1 to which a precast member is applied will be described with reference to FIG. Tunnel 1 is constructed using the NATM tunneling method (New Austrian Tunneling Method).

  As shown in FIG. 1, the tunnel 1 includes a primary support 3 provided in an arch shape along the inner peripheral surface of the tunnel excavation anti-grid, and a lining concrete portion 5 provided inside the primary support 3. I have. The primary support 3 includes a steel support 7 provided on the inner peripheral surface of the tunnel excavation resistance. The steel support 7 is divided into two in the circumferential direction, for example, and is formed by connecting a pair of H steels forming an arc along the inner peripheral surface of the tunnel 1.

  Further, the primary support 3 includes a sprayed concrete portion 9. The sprayed concrete portion 9 is formed on the inner peripheral surface of the tunnel 1 by a spraying method so as to fill the space between the steel supporters 7. Further, the primary support 3 includes a number of lock bolts 11 driven into the ground from the sprayed concrete portion 9 toward the radially outer side of the tunnel 1. The lining concrete part 5 is placed further inside the steel supporting work 7 and the sprayed concrete part 9 so as to cover the primary supporting work 3.

  Further, the tunnel 1 includes an invert 15. The invert 15 is provided on the bottom surface 19 of the tunnel 1 so as to connect both the legs 4 a and 4 b of the primary support 3. The invert 15 is provided in an inverted arch shape (downwardly convex arch shape), and the tunnel 1 is structurally stabilized by closing the cross section of the tunnel 1. Note that the portion 17 below the legs 4a and 4b is excavated before the invert 15 is constructed, and backfilled after the invert 15 is completed. Since the above configuration relating to the tunnel 1 is known as a configuration of a NATM tunnel having an invert, further detailed description is omitted.

  As shown in the figure, in the tunnel 1 of the present embodiment, the invert 15 is composed of precast plates P1, P2, and P3 divided into three in the width direction of the tunnel 1. The precast plates P1 to P3 are reinforced concrete plates that are manufactured in advance at a factory and cured underwater. In the factory, the precast plates P1 to P3 are cured underwater for a specified number of days or more (for example, 7 days or more). Of these, the precast plates P2 and P3 are precast plates installed adjacent to the leg portions 4a and 4b, respectively.

  That is, outside the tunnel 1 tunnel, a mold, a curing water tank, and a product temporary storage yard are prepared, and the precast plates P1 to P3 are molded. Then, it is cured underwater for a prescribed number of days or more, and the precast plates P1 to P3 are completed under predetermined quality control. In general, invert is desired to develop strength as early as possible after construction. In response to this request, the tunnel 1 employs the precast plates P1 to P3 that are sufficiently cured in water in advance, so that the strength is expressed earlier than the in-situ invert. Therefore, the effect of closing the tunnel cross section can be exhibited at an early stage, and the displacement of the tunnel 1 and the loosening of the natural ground due to the natural ground pressure can be suppressed.

  The structure of the three precast plates P1 to P3 will be described with reference to FIG. 2A, 2B, and 2C are cross-sectional views of the precast plates P1, P2, and P3 in the cross section of the tunnel 1, respectively. The cross-sectional shape of each part in the following description means the shape of the cross section of the tunnel 1 as shown in FIG.

  The precast plates P <b> 1 to P <b> 3 are plate-like members that are substantially rectangular in plan view, and have a curved shape corresponding to the arch shape of the invert 15. The dimension of the precast plates P1 to P3 in the width direction of the tunnel 1 depends on the width of the tunnel 1, but is about 3 to 4 m, for example. Moreover, the dimension of the length direction of the tunnel 1 is about 1.5 m, for example. Such precast plates P1 to P3 are two-dimensionally spread to form the invert 15.

  The precast plate P1 (first precast plate) shown in FIG. 2A is located at the center of the three precast plates P1 to P3, and is not adjacent to the leg portions 4a and 4b when installed. The precast plate P1 has both end portions P1a and P1b. Since the upper half of the end surfaces of both end portions P1a and P1b is provided with a notch q1 having a rectangular cross section, both end portions P1a and P1b have L-shaped cross sections. Presents.

  The precast plate P2 (second precast plate) disposed adjacent to one side of the precast plate P1 has an end provided with a rectangular cross-section notch q2 in the lower half of the end surface, as shown in FIG. 2 (b). It has a part P2a. The end P2a has an upside down L-shaped cross section. The end portion P1b of the precast plate P1 and the end portion P2a of the precast plate P2 have a shape that is fitted to each other, and are connected to each other by phase notches (see FIG. 1).

  Similarly, the precast plate P3 (third precast plate) disposed adjacent to the other side of the precast plate P1 is provided with a notch q3 having a rectangular cross section in the lower half of the end surface as shown in FIG. 2 (c). End P3b. The end P3b has an upside down L-shaped cross section. The end portion P1a of the precast plate P1 and the end portion P3b of the precast plate P3 have a shape to be fitted to each other, and are connected to each other by phase notches (see FIG. 1). The other end P2b of the precast plate P2 and the other end P3a of the precast plate P3 are not formed with a notch, but have a flat end surface.

  With reference to FIG. 3, the connection structure of edge part P1b, P2a and edge part P1a, P3b is demonstrated. As shown in FIG. 3A, the male side coupling fitting 21 is embedded in the end portion P2a, and the female side coupling fitting 23 is buried in the opposite end portion P1b. When the end portions P1b and P2a are brought into contact with each other, the distal end portion of the male side connection fitting 21 is inserted into the opening 23a of the female side connection fitting 23. Then, as shown in FIG. 3B, when the tip pin 21a of the male side connection fitting 21 abuts against the bottom surface of the opening 23a, the sleeve 21b of the male side connection fitting 21 is pushed out and the sleeve 21b is opened. It bites into the side wall surface of 23a. As a result, the male side connection fitting 21 and the female side connection fitting 23 are firmly connected, and as a result, the end portions P1b and P2a are firmly connected. In addition, since the connection structure of the edge part P1a and the edge part P3b is the same as that of the above, the overlapping description is abbreviate | omitted.

  Note that the structure shown in FIG. 4 may be adopted instead of the connection structure shown in FIG. In the structure of FIG. 4, the male side connection fitting 21 is provided so as to protrude downward from the horizontal surface of the notch portion of the end portion P2a, and is opposed to the upper surface in the horizontal surface of the notch portion of the end portion P1b. A female-side connecting metal fitting 23 is provided so as to open to the center. 3 and 4, the male side connecting bracket 21 and the female side connecting bracket 23 may be reversed. The three precast plates P1 to P3 are connected in the structure as described above, and the member P (see FIG. 1) composed of the three precast plates P1 to P3 corresponds to the precast member in the claims.

  Next, an example of the above-described invert 15 construction method will be described as a first embodiment of the invert construction method according to the present invention with reference to FIG.

  As shown in FIG. 5 (a), after the portion 17 below the legs 4a, 4b of the primary support 3 is excavated and the tunnel bottom surface 19 appears, a mortar equal to or higher than the base material equivalent of the precast plates P1 to P3 The precast board P1 is installed in the center part on the bottom face 19 using a spacer (first installation step). Thus, a precast plate (here, precast plate P1) other than the precast plates P2 and P3 adjacent to the legs 4a and 4b of the primary support 3 is selected as the precast plate to be installed first. At this time, the precast plate P1 is set in advance at a position where the precast plate P1 is to be disposed in the invert 15 after completion, and is not moved in the subsequent steps.

  Subsequently, as shown in FIG. 5B, the precast plate P <b> 2 is inserted and installed between the precast plate P <b> 1 and the leg portion 4 a of the primary support 3. Here, the one end P1b of the precast plate P1 and the end P2a of the precast plate P2 are connected (second installation step). At this time, as described above, the end portions P1b and P2a are connected to each other by the phase notches so that the end portion P2a overlaps the end portion P1b. A gap is formed between the other end portion P2b of the precast plate P2 and the leg portion 4a, but the other end portion P2b and the leg portion 4a are connected by a connecting structure described later.

  Then, as shown in FIG.5 (c), the precast board P3 is inserted and installed between the precast board P1 and the leg part 4b of the primary support work 3. As shown in FIG. Here, the other end P1a of the precast plate P1 and the end P3b of the precast plate P3 are connected (third installation step). At this time, the end portions P3a are overlapped on the end portion P1a, and the end portions P1a and P3b are connected to each other by the phase notches as described above. A gap is formed between the other end portion P3a and the leg portion 4b of the precast plate P3, but the other end portion P3a and the leg portion 4b are connected by a connecting structure described later.

  Subsequently, the other end P2b of the precast plate P2 and the leg 4a are connected, and the other end P3a of the precast plate P3 and the leg 4b are connected. This connection structure will be described with reference to FIG. As shown in FIG. 6, a metal connecting member 31 having a trapezoidal cross section is fitted between the end surface of the end portion P3a of the precast plate P3 and the lower end surface of the steel support 7 in the leg portion 4b. Furthermore, the gap is finely adjusted by inserting an appropriate number of sheet irons 33 and the camber 35 between the metal connecting member 31 and the end face of the end portion P3a. Thereby, the precast board P3 and the leg part 4b of the primary support 3 are connected. The gap between the lining concrete portion 5 and the precast plate P3 may be filled with lining concrete. Moreover, the precast board P2 and the leg part 4a of the primary support 3 are connected with the same structure. As described above, the cross-sectional closed structure of the tunnel 1 in which the primary support 3 and the invert 15 are connected is completed.

  Immediately thereafter, in order to integrate the invert 15 and the bedrock below it, the early strong mortar is filled from a grout hole (not shown) embedded in the precast plates P1 to P3. Then, the strength of the filled early mortar is confirmed using a test piece. Thus, the invert 15 having a length of, for example, 1.5 m is completed in the longitudinal direction of the tunnel 1, and the above process is performed while moving in the longitudinal direction of the tunnel 1 in the same manner, so that the invert 15 is Extend in the longitudinal direction. Thereafter, reference is made back to the portion 17 (FIG. 1) above the invert 15.

  Then, the effect by the invert 15 mentioned above and its construction method is demonstrated.

  In the construction method of the invert 15 of this embodiment, the invert 15 is formed by a plurality of precast plates P1 to P3 connected in the width direction of the tunnel 1 (here, three). And, since the end portions P1a and P1b of the precast plate P1 have an L-shaped cross section and are fitted to the end portions of the precast plates P2 and P3 and connected by phase-separation, the precast plates P1 to P3 are firmly connected to each other. Is done. With this structure, even when the precast plates P1 to P3 receive a force from below due to the pressure from the natural ground, the lifting and dropping are suppressed.

  Further, the force acting from below due to the pressure from the natural ground is considered to be greatest in the central portion of the invert 15. Therefore, the both ends P1a and P1b of the center precast plate P1 are pressed down by the end portions P3b and P2a of the precast plates P3 and P2, respectively, so that the precast plate P1 caused by the pressure from the ground Lifting and dropping off can be effectively suppressed.

  In this construction method, the precast plate P1 that is not adjacent to the legs 4a and 4b of the primary support 3 is first installed, and then the precast plates P2 and P3 are installed so that the end portions overlap the precast plate P1. Then, connect them with phase cuts. Therefore, although the end portions of the precast plates P1 to P3 are fitted to each other with a phase gap and firmly connected, the precast plates P2 and P3 can be easily installed, and good workability can be ensured. The work time can be shortened due to good workability. As a result, restrictions on the passage of tunnel excavation vehicles and the like can be relaxed, and the efficiency of tunnel excavation work can be improved.

  Subsequently, as a second embodiment of the invert construction method according to the present invention, another example of the invert 15 construction method will be described with reference to FIGS. 7 and 8. In addition, in this construction method, since the connection process of the edge parts of the precast boards P1-P3, the filling process of early strong mortar, etc. are equivalent to the process shown by the above-mentioned construction method, the overlapping description is abbreviate | omitted.

  As shown in FIG. 7A, first, excavation is performed while leaving a portion 17b close to the leg portion 4b in the portion 17 below the leg portions 4a and 4b of the primary support 3. As a result, a portion of the tunnel bottom 19 that is close to the leg 4a is exposed. The exposed portion is a portion where the precast plates P1 to P3 including the central precast plate P1 and the precast plates (precast plates P1 and P2) located on the leg 4a side are to be installed. Next, as shown in FIG.7 (b), the precast board P1 is installed in the center part on the bottom face 19 (1st installation process). Then, as shown in FIG.7 (c), the precast board P2 is inserted and installed between the precast board P1 and the leg part 4a of the primary support 3, and the edge parts of the precast boards P1 and P2 are connected. (Second installation step).

  During the installation work of the precast plates P1 and P2, the upper surface of the portion 17b is used as the traveling zone 18b of the vehicle. Thereby, the tunnel excavation vehicle can be passed through the traveling zone 18b, and the tunnel excavation work can be efficiently performed in parallel.

  Subsequently, as shown in FIG. 8A, a portion 17b including the traveling zone 18b is excavated, and a portion of the tunnel bottom surface 19 near the leg portion 4b is exposed. The exposed portion is a portion where the remaining precast plate P3 is to be installed. Furthermore, the part 17a close | similar to the leg part 4a among the parts 17 lower than the leg parts 4a and 4b of the primary support 3 is refilled on the precast boards P1 and P2. Next, as shown in FIG. 8B, the precast plate P3 is inserted between the precast plate P1 and the leg portion 4b of the primary support 3, and the end portions of the precast plates P1 and P3 are connected to each other (first 3 installation process).

  During the installation work of the precast plate P3, the upper surface of the portion 17a is used as the traveling zone 18a of the vehicle. Thereby, the tunnel excavation vehicle can be passed through the traveling zone 18a, and the tunnel excavation work can be efficiently performed in parallel.

  Subsequently, the tunnel 1 in which the end portion of the precast plate P2 and the leg portion 4a are connected, and the end portion of the precast plate P3 and the leg portion 4b are connected, whereby the primary support 3 and the invert 15 are connected. The cross-sectional closed structure is completed. Thereafter, as shown in FIG. 8C, the upper portion 17 of the invert 15 is completely backfilled.

  According to the construction method of the present embodiment, the traveling zone 18a or 18b of the tunnel excavation vehicle can always be secured even during the construction of the invert 15, so the construction of the invert 15 and the tunnel excavation work are performed in parallel. Can do.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to the said embodiment, You may change in the range which does not change the summary described in each claim. For example, in the embodiment, the invert 15 is divided into three in the tunnel width direction, but as shown in FIG. 9, the invert is divided into five, and the five precast plates P11 to P15 are connected in the width direction to form the invert 215. May be. In this case, first, a precast plate (P11, P12, or P13) other than the precast plates P14, P15 adjacent to the legs 4a, 4b of the primary support 3 may be installed. Here, among the five sheets, the central precast plate P11 is installed first, and for example, the precast plates P11, P12, P13, P14, and P15 are installed in this order.

  In this case, the precast plate (first precast plate) P11 has both end portions P11a and P11b having an L-shaped cross section, and adjacent precast plates (second and third precast plates) P12 and P13 each have an inverted L-shaped cross section. It has one end P12, P13b.

  Then, the precast plates P11 to P13 are connected by phase-separation by the same structure as the above-mentioned precast plates P1 to P3, and a precast member P ′ composed of three precast plates P11 to P13 is formed. The precast member P 'corresponds to the precast member in the claims. Then, the precast plates P14 and P15 are connected to both sides of the precast member P 'to form the invert 215. In addition, you may use the connection structure of a phase-separation joint also between the precast board P12 and P14 and between the precast board P13 and P15.

  Further, the number of precast plates is not limited to three or five, but may be seven or nine. However, since the connecting portion between the precast plates is a relatively weak portion, it is preferable to reduce the number of connecting portions. . Therefore, it is preferable that the number of precast plates divided in the tunnel width direction is smaller, and three is preferable.

  The number of precast plates may be an even number, but an odd number is preferable. As described above, it is considered that the force acting from below by the pressure from the natural ground is the largest in the central part of Invert. When the number of precast plates is an even number, a connection portion between the precast plates, which is a relatively weak portion, may be disposed in the central portion of the invert. On the other hand, when the number of precast plates is an odd number, a structure in which a connecting portion between the precast plates is arranged at the central portion of the invert is avoided, and the strength of the invert can be ensured.

DESCRIPTION OF SYMBOLS 1 ... Tunnel, 3 ... Primary support, 4a, 4b ... Primary support leg, 7 ... Steel support, 9 ... Sprayed concrete part, 11 ... Rock bolt, 15,215 ... Invert, 19 ... Tunnel bottom, P, P '... precast member, P1, P11 ... first precast plate, P2, P12 ... second precast plate, P3, P13 ... third precast plate, q1, q2, q3 ... notches.

Claims (4)

Inverting method in which the inverted arch-shaped invert is formed on the bottom of the tunnel by connecting the legs of the arch-shaped primary support with steel support, sprayed concrete and rock bolts in the NATM tunnel method Because
The invert is
A plurality of precast plates connected in the width direction of the tunnel at the bottom of the tunnel,
The invert is
A first precast plate having both ends provided with notches so as to have an L-shaped cross section;
A second precast plate having a notch provided with an inverted L-shaped cross section and having an end connected to one end of the first precast plate by a phase notch;
A third precast plate having a notch so as to have an inverted L-shaped cross section and having an end connected to the other end of the first precast plate by a phase notch,
A first installation step of installing the first precast plate at a predetermined position on the bottom surface of the tunnel;
The second precast plate is installed adjacent to one side of the first precast plate installed at the predetermined position, and the end portions of the first and second precast plates are connected to each other by phase notches. Installation process;
A third precast plate is installed adjacent to the other side of the first precast plate installed at the predetermined position, and third ends of the first and third precast plates are connected to each other by phase-separation. Installation process;
An invert construction method characterized by comprising: The number of the precast plates connected in the width direction to form the invert is an odd number,
2. The invert construction method according to claim 1, wherein the first precast plate is disposed at a center of the plurality of precast plates. Inverting the arch-shaped primary support legs with steel support, sprayed concrete and rock bolts in the NATM tunnel construction method to form a convex arch shape,
It consists of a precast plate connected in the width direction of the tunnel at the bottom of the tunnel,
A first precast plate having both ends provided with notches so as to have an L-shaped cross section;
A second precast plate having a notch provided with an inverted L-shaped cross section and having an end connected to one end of the first precast plate by a phase notch;
And a third precast plate having a notch provided with an inverted L-shaped cross section and having an end portion connected to the other end portion of the first precast plate by a phase notch. . It is a precast member that forms at least a part of an invert that forms a convex arch shape by connecting the legs of an arch-shaped primary support with steel support, sprayed concrete, and rock bolts in the NATM tunnel method. And
The invert is composed of a precast plate connected in a plurality in the width direction of the tunnel at the bottom of the tunnel,
A first precast plate having both ends provided with notches so as to have an L-shaped cross section;
A second precast plate having a notch provided with an inverted L-shaped cross section and having an end connected to one end of the first precast plate by a phase notch;
A precast comprising: a third precast plate having a notch provided with an inverted L-shaped cross section and having an end connected to the other end of the first precast plate by a phase notch Element.

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