JP2016204938A - Ground lowering method for existing tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To renovate an existing tunnel by expanding a tunnel cross-section, without widening a tunnel width or interrupting traffic during the renovation work.SOLUTION: A pile 10 is installed at a prescribed interval under a road surface of an existing tunnel, in a longitudinal direction. A temporary road surface is constructed using the pile 10 and with a covering plate 12, to cover two lanes in opposite directions. A space underneath the covering plate 12 is excavated for lowering a ground to a prescribed excavation bottom surface, and excavation is performed to below a side wall leg part of the existing tunnel. Then, an exposed wall surface on a ground side is supported by a lock bolt and sprayed concrete. Furthermore, side wall concrete 24 is installed for supporting a tunnel arch section and backfill 35 and pavement are provided, thus securing an expanded tunnel cross-section.SELECTED DRAWING: Figure 6

Description

  The present invention relates to securing the building limit of an existing tunnel, and in particular, in construction for constructing a repair tunnel by enlarging the cross section of the existing tunnel, it is being used without acquiring a new site for the tunnel and the installation road, and during construction. This is related to the method of lowering the existing tunnel so that the construction can be performed without blocking the traffic.

  In recent years, in order to cope with an increase in traffic volume and an increase in size of a passing vehicle, various tunnel widening methods for widening the cross section of an existing tunnel under a live line have been proposed (Patent Documents 1 and 2).

  In the tunnel widening method shown in Patent Document 1, when excavating a large-section tunnel on the outer periphery while supporting the arch and side wall of the existing tunnel, the lining of the existing tunnel is reinforced and the vehicle passing through the existing tunnel is It is characterized by excavating the surrounding ground of the existing tunnel as a protective work and widening the tunnel.

  In the tunnel widening method shown in Patent Document 2, the leading top tunnel of the enlarged tunnel is excavated on the ground above the existing tunnel in the state in which the inner lining of the existing tunnel is reinforced in advance, and the surrounding of the reinforced existing tunnel The lining of the existing tunnel is dismantled after excavation of the widened section is completed.

JP 2000-257368 A JP 2003-278475 A

  Any of the above-mentioned widening methods for existing tunnels are based on the premise that the lining of the existing tunnel will be dismantled and removed over the entire section after the construction of the enlarged tunnel. For this reason, in order to widen the cross section of the existing tunnel, in addition to the widening work of the tunnel body, dismantling and removal work of the existing tunnel and further light work such as widening the width of the road before and after the existing tunnel are required. For this reason, construction work will be prolonged, and in urban areas, it will take many years to secure land for the widening range that will be the approach of the tunnel, so it will not be possible to solve the problem at an early stage. There is a problem of not.

  In conventional existing tunnels, there are many cases in which the shoulder of the arch portion is limited to the construction limit due to the increase in size of the vehicle and hinders the passage of the vehicle. For this reason, if a marginal space with respect to the building limit can be secured in this portion, the problem related to vehicle traffic is often solved. Also, if widening work can be performed with the arch part of the existing tunnel as it is, the excavation cross section is small compared to the tunnel widening method as shown in each patent document, and traffic blocking is hardly caused. The construction period can be shortened.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and in the construction to widen the existing tunnel, it is necessary to block the traffic without acquiring a new site for the tunnel and the attachment road. The purpose of the present invention is to provide a method for lowering an existing tunnel so that construction can be performed without blocking traffic during the construction process.

  In order to achieve the above object, the lowering method of the existing tunnel according to the present invention constructs a pile at a predetermined pitch in the longitudinal direction under the road surface of the existing tunnel, and uses this pile to construct a receiving girder. A temporary road surface is constructed by laying a lining plate on the receiving girder, and the lower space of the lining plate is excavated down to a predetermined excavation bottom surface, and excavation is performed under the side wall leg portion of the existing tunnel. Side wall concrete surfaces are supported, side wall concrete is provided to support the arch portion of the existing tunnel, and an enlarged cross section is secured with the excavation bottom surface as the road surface after enlargement.

The existing tunnel consists of two lanes, builds a temporary road surface with the lining plate over both lanes, and then sequentially performs board digging in both lanes, side wall concrete construction,
It is preferable to sequentially perform roadbed construction in both lanes after widening.

  The existing tunnel is composed of two lanes, and in one lane and the other lane, the traffic lanes are replaced, and the temporary road surface is constructed in both lanes sequentially by the lining plates, and then the lanes are replaced again. It is preferable to perform the lowering excavation in both lanes and the construction of the side wall concrete in order, and further refill the traffic lane to sequentially perform the roadbed construction in both expanded lanes.

  It is preferable that the excavation to the lower side of the side wall leg, the support of the natural mountain side wall surface, and the construction of the side wall concrete are performed at predetermined intervals along the longitudinal direction of the existing tunnel.

  It is preferable that the excavation to the lower side of the side wall leg, the support of the natural mountain side wall surface, and the construction of the side wall concrete are performed at predetermined intervals alternately in the longitudinal direction of the existing tunnel and on both side walls of the tunnel cross section.

  The natural mountain side wall surface is preferably supported by shotcrete and rock bolts.

  The side wall concrete is preferably constructed so as to be integrated with a part of the side wall of the existing tunnel.

  It is preferable to cover the surface of the arch portion of the existing tunnel with a waterproof sheet and a precast concrete lining arch member and fill the gap with air mortar.

  It is preferable that the tunnel lining after the widening has a shape in which the invert is closed.

  It is preferable to lay a precast concrete paving slab as the road surface of the tunnel after the widening.

The schematic front view which showed the cross-sectional shape of the existing tunnel which applies the board lowering method of the existing tunnel of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic front view which showed the cross-sectional shape of the expansion tunnel which expanded by the board lowering excavation applying the board lowering construction method of the existing tunnel of this invention. Explanatory drawing which showed the construction order of the expansion construction of the existing tunnel by one Embodiment of this invention (steps 1 and 2). Explanatory drawing (steps 3 and 4) which showed the construction sequence of the panel lowering construction of the existing tunnel by one Embodiment of this invention. Explanatory drawing (steps 5 and 6) which showed the construction order of the panel lowering construction of the existing tunnel by one Embodiment of this invention. Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by one Embodiment of this invention (step 7, 8). Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by one Embodiment of this invention (step 9, 10). Explanatory drawing which showed the construction order in the excavation method of the panel lowering construction of the existing tunnel by one Embodiment of this invention. Explanatory drawing which showed the construction order in the excavation method of the panel lowering construction of the existing tunnel by one Embodiment of this invention. Explanatory drawing which showed the construction order in the excavation method of the panel lowering construction of the existing tunnel by one Embodiment of this invention. The schematic front view which showed the cross-sectional shape of the existing tunnel which applies the panel lowering method of the existing tunnel by other embodiment of this invention. The schematic front view which showed the cross-sectional shape of the widening tunnel which expanded the width by the downhill excavation by applying the downhill construction method of the existing tunnel by other embodiment of this invention. Explanatory drawing (step 1) which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention. Explanatory drawing (step 2) which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention. Explanatory drawing (step 3) which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention. Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention (step 4). Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention (step 5). Explanatory drawing (step 6) which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention. Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention (step 7). Explanatory drawing which showed the construction order of the panel lowering construction of the existing tunnel by other embodiment of this invention (step 8).

  Hereinafter, the following construction examples will be described with reference to the accompanying drawings as a mode for carrying out the panel lowering method of the existing tunnel of the present invention.

[First Embodiment]
FIG. 1 shows an example of a cross-sectional shape of an existing tunnel 50 to be widened. As shown in the figure, the building limit 52 has invaded a part of the arch portion 53 supported by the side wall concrete 54, and the passage of a large vehicle 60 such as an international standard container trailer is hindered. Yes.

  FIG. 2 shows the cross-sectional shape of the enlarged tunnel 1 after the tunnel cross-section is enlarged by the existing tunnel lowering method of the present invention. As shown in the figure, the construction limit 2 can be significantly increased by constructing the road surface 30 with the arch portion 53 of the existing tunnel 50 left as it is, and with the board lowered. Although the enlarged tunnel 1 of this embodiment has an inverted closed structure, a pile head of a support pile 10 diverted by cutting a part of a temporary pile described later is embedded and fixed to the inverted concrete 25. Thereby, the enlarged tunnel 1 functions as a structure in which the invert is supported by the support layer. Note that the pile head of the pile 10 may be positioned in the ground below the invert concrete without being embedded in the invert concrete 25 and insulated from the invert concrete 25. In that case, the support pile 10 does not directly support the enlarged tunnel 1, but can function as a deterrent pile that suppresses lateral movement due to partial pressure in soft ground. A precast concrete lining arch 40 is constructed on the inner peripheral surface of the arch portion 53 of the expansion tunnel 1. The precast concrete lining arch 40 of the present embodiment has a substantially semicircular arch structure in which arches of 2 to 3 blocks are assembled, and each arch is constructed by using a gate-type mobile stand or a dedicated installation machine (not shown) and an aerial work vehicle. It is assembled along the inner peripheral surface of the portion 53. At that time, the existing arch part 53 is formed, and the arch part 53 and the precast concrete lining arch are used as countermeasures against water leakage from cracks and joints of the lining concrete or gaps between bricks and concrete blocks, which are weak points of conventional method lining. A gap filling portion 41 is constructed in which a waterproof sheet (not shown) is stretched between the gap 40 and the gap between the arch portion 53 is filled with air mortar or the like.

  Generally, cement concrete pavement is used for the road surface 30 in the tunnel, but since a concrete curing period is required, a precast concrete concrete pavement plate is laid.

  Hereinafter, a series of construction situations (steps 1 to 10) of the existing tunnel lowering method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 3 (a-1) shows that piles 10 are laid at a predetermined pitch in the longitudinal direction over the entire length of the tunnel in each of the upper and lower lanes 5 of the existing two-lane tunnel 50, and a receiving girder 11 is installed on the pile 10. The tunnel cross section in the construction situation (step 1) which constructed the temporary road which laid the lining board 12 on the receiving girder 11 is shown. FIG. 3A-2 is a longitudinal sectional view of the tunnel in this state. In this embodiment, the piles 10 are driven at intervals of 2 m in the longitudinal direction. This road surface lining work is performed by day and night one-lane regulation or night one-lane regulation (traffic is opened during the day) according to traffic conditions. The pile 10 uses the H-shaped steel pile as a temporary pile in this construction example. Moreover, it is preferable to previously provide a pile connection part in a part of the pile 10 so that the pile head is located in the invert concrete 25 when the enlarged tunnel is completed as described above.

  FIGS. 3B-1 and 3B-2 show tunnel cross sections in the excavation state (step 2) of the space under the temporary road. Since the piles 10 are dense and narrow in the space 7 under the road, a small self-propelled excavator (not shown) is carried in from an opening provided by removing a part of the lining plate 12 behind the face. Carry out (large back) excavation work. At this time, in order to secure a working space, the lining plate 12 at the excavation position is temporarily removed to perform excavation work. Further, it is preferable to extend a carry-out path (not shown) for continuously carrying out the excavated sediment to the outside of the tunnel well opening so as not to block the passage of the vehicle on the temporary road by the excavated sediment transport operation. . As for the excavation procedure of the space 7, it is preferable to perform bench excavation of the entire cross section or an appropriate number of steps according to the stability of the natural ground, and to stabilize the face and the slope with shotcrete or the like. Moreover, it is also preferable to improve the stability of the temporary road by reinforcing the exposed piles 10 with a connecting material (not shown) as necessary.

  4 (c-1), (c-2) to FIG. 5 (e-1), (e-2) are side walls of the existing tunnel 50 in one lane (referred to as the left side of the paper, hereinafter referred to as lane 1). The process (steps 3 to 5) from the removal of a part of the section to the construction of the side wall concrete and the invert part of the enlarged tunnel is shown. 8-10 are shown in order to explain the construction direction in the longitudinal direction and the left and right lanes when the digging method is adopted. Hereinafter, the construction content of each work will be described with reference to each drawing.

  4 (c-1) and (c-2) show a state in which a part of the existing tunnel 50 side wall concrete 54 on the lane 1 side is removed and the remaining side wall concrete part 54 a is reinforced with the lock bolt 21. ing. As shown in FIG. 4 (c-1), in the down excavation of the side wall portion of the enlarged tunnel, the area below the side wall leg portion of the existing tunnel 50 is excavated. In the expansion tunnel, the side wall concrete 54 of the existing tunnel 50 is removed in order to construct the new side wall concrete 24 (FIG. 5 (e-1)) instead of the side wall concrete 54 of the existing tunnel 50. However, since the side wall concrete 54 is a member that supports the arch portion 53, it is important that the arch portion is not deformed. Therefore, a part 54 a of the side wall concrete 54 of the existing tunnel is left, and this part is used as a support member for the arch portion 53 of the existing tunnel 50. A part 54 a of the side wall concrete on the natural ground 8 side was left and reinforced with the lock bolt 21 to form a support member for the arch portion 53. The number and length of the lock bolts 21 are determined by designing appropriately according to the situation of the target ground. Thereby, the arch part 53 of the existing tunnel can be reliably supported until the side wall concrete of the enlarged tunnel is completed. At this time, it is preferable to temporarily remove the lining plate at the work position in order to secure a work space in each work.

  By the way, in the excavation and support work in steps 4 and 5 described above, in order to support the arch portion of the existing tunnel with certainty, an “excavation method” is performed for each block at a predetermined interval along the tunnel longitudinal direction. Adopted (FIG. 4 (c-2)). Here, the extraction step will be described with reference to FIGS. FIG. 8 shows an example of construction in a state where the natural ground stability is relatively poor. If the natural ground is bad, there is a risk of uneven earth pressure if only one side lane is constructed, so the left and right lanes will be constructed alternately. Therefore, it is preferable to perform the construction rotation in accordance with the lining span of the existing tunnel arch part. For example, if the lining span is 12 m, one excavation length is 3 m. As the construction order, as shown in FIG. 8 (a), first, the order of lane 1 and lane 2 with respect to even-numbered blocks within one span (for example, 2BL and 4BL in FIG. 4 (c-1)), respectively. Perform construction at (For example, the order of circle numbers 1 → 2 → 3 → 4). This operation is performed over the entire length in the tunnel longitudinal direction. The construction in one span can be performed as a parallel work at a plurality of locations. In that case, it is preferable to work in a span that is separated by one span or more in order to prevent the efficiency of each work from being reduced due to the proximity construction. When the excavation construction in the entire length of the tunnel or in the predetermined range is completed, the excavation construction of the unconstructed block is performed (FIG. 8B). Also in this case, as shown in FIG. 8 (b), the construction of the non-constructed blocks is performed in the order of lane 1 and lane 2 in order of odd blocks remaining in one span (circled number 5 → 6 → 7 → 8). Needless to say, excavation is performed by appropriately changing the excavation procedure described above. For example, in an even block, excavation can be performed in a zigzag manner such as circle numbers 1 → 4 → 2 → 3, and in subsequent odd blocks, excavation can be performed in the order of circle numbers 5 → 8 → 6 → 7.

  Next, the excavation step when the natural ground is relatively stable will be described with reference to FIGS. If the ground is stable and there is no risk of uneven earth pressure, digging up to the side wall of the existing tunnel can be preceded by a one-sided lane with emphasis on workability. As shown in FIG. 9A, construction is first performed in order on even-numbered blocks (for example, 2BL, 4BL in FIG. 4C-1) within one span of lane 1 (circle numbers 1 → 2). . This work is performed along the tunnel longitudinal direction. When the excavation construction in the entire length of the tunnel or in the predetermined range is completed, the excavation construction of the unconstructed block of the lane 1 is continued (FIG. 9B). As shown in FIG. 9 (b), the unapplied block is applied to odd blocks remaining in one span of the lane 1 (circle numbers 3 → 4). Subsequently, as shown in FIGS. 10A and 10B, in the lane 2, the construction of even blocks (round numbers 5 → 6) and the odd blocks (round numbers 7 → 8) are performed. In this case as well, construction in one span can be performed as a parallel work at a plurality of locations, but it is preferable to work in a span that is separated by one span or more in order to prevent a reduction in the efficiency of each work due to the proximity construction. In addition, it cannot be overemphasized that various setting is possible for the construction order of these blocks, the length of a block, etc. in consideration of the state of natural ground, construction nature, etc.

  4 (d-1), (d-2), FIG. 5 (e-1), and (e-2) will be described below with respect to the supporting work (steps 4 and 5) of the site excavated by the above-described excavation method. The description will be given with reference. In step 4, the above-described excavation of the target block, construction of the exposed ground sprayed concrete 20 and placement of the lock bolt 21 are performed. In this embodiment, the spraying thickness of the shotcrete 20 is 10 cm, the length of the lock bolt 21 is 3 m, and the pitch is 1 m in the longitudinal direction. It is preferable to appropriately design and determine according to the mountain situation.

  FIGS. 5 (e-1) and 5 (e-2) show the construction situation (step 5) in which the side wall concrete 24 is constructed on the side wall after excavation by lowering. As shown in the figure, the side wall concrete 24 has a substantially L shape including a side wall 24a integrated with a part of the side wall concrete 54 of the existing tunnel and a part 24b of an invert (bottom slab), and from the arch portion to the side wall 24a. The transmitted load is reliably supported by the invert (bottom plate) 24b. As shown in FIG. 5 (e-1), the lining thickness of the side wall concrete 24 is set to a thickness along the inner empty cross section of the enlarged tunnel, and the expanded tunnel 1 together with the invert concrete 25 to be finally constructed. As the lining member, a reinforced concrete structure in which a predetermined amount of reinforcing bars is arranged. When placing the invert concrete 25, it is preferable to install a box form (not shown) in the portion including the pile 10. Moreover, it is preferable to provide the water stop part 26 using the rubber-type water stop board around the pile 10 near the bottom part.

  FIGS. 5 (f-1) and 5 (f-2) show a state (step 6) in which the construction up to a part of the side wall concrete and invert concrete 25 of both lanes is completed by the above-described excavation method. In this state, since the invert is not closed, temporary struts (cut beams) are arranged at a predetermined pitch in the tunnel longitudinal direction between the inverts placed opposite to each other in order to prevent deformation of the tunnel cross section. It is also preferable.

  6 (g-1) and 6 (g-2) show a state (step 7) in which invert concrete 25 is placed and invert closing is performed. As a result, the enlarged tunnel 1 is dynamically stabilized. The enlarged tunnel 1 of the present embodiment has a structure in which the invert is supported by the pile 10, but as described above, the tunnel cross section that closes the invert as a structure in which the pile head of the pile 10 is not embedded and fixed in the invert concrete 25. It is good.

  6 (h-1), (h-2) to FIGS. 7 (j-1) and (j-2), in order to secure a road surface 30 with a predetermined design height in the enlarged tunnel 1, the predetermined height is reached. The backfilling material 35 is laid, rolled and shaped to construct the backfill portion 35, and the construction state (steps 8 to 10) until the roadbed 31 and the surface pavement 33 having a predetermined design thickness are applied thereon is shown. Yes. The pile 10 upper part, the receiving girder 11, and the lining board 12 can be removed sequentially from the range where the backfilling part was constructed. At this time, as shown in FIG. 9 (i-2), in order to perform the roadbed work 31 on the backfill portion 35, it is preferable to provide the temporary slope 34 with a predetermined inclination from the end of the temporary road to the road surface 30. As shown, the temporary slope 34 may be composed of a temporary roadbed 36 and a temporary surface pavement 37, or a temporary lining plate and support legs (not shown) for easy movement. You may make it do.

  On the other hand, in a tunnel with a long extension, the approach road 38 toward the tunnel wellhead is preferably rubbed as a slope from the existing road to the road surface 30 in the tunnel with a predetermined gradient (for example, 5%) (FIG. 7 (i -2), (j-2)). In the case of a tunnel with a short extension, it is also possible to lower the approach road in a predetermined range leading to the tunnel pit according to the road surface of the enlarged tunnel without providing a ramp.

  In the above description, the enlarged tunnel after enlargement has a cross-sectional shape that closes invert, but when the ground strength is good, the tunnel cross-sectional shape that supports the load of the arch part with side wall concrete without providing invert is also possible. Good.

[Second Embodiment]
Hereinafter, as another embodiment (second embodiment) of the tunnel lowering method of the existing tunnel of the present invention, one lane is preliminarily constructed with respect to the existing tunnel of two facing lanes, and then the other lane is constructed. An example of construction performed will be described.

  FIG. 11 shows an example of the cross-sectional shape of the existing tunnel 50 to be widened as in FIG. Also in this figure, the building limit 52 invades a part of the arch portion 53 supported by the side wall concrete 54, and there is an obstacle to the passage of the large vehicle 60 such as a container trailer.

  FIG. 12 shows the cross-sectional shape of the enlarged tunnel 1 after the tunnel cross-section is widened by the board lowering method of the other embodiment. The enlarged tunnel shown in the figure has a cross-sectional shape that does not perform invert closure. The arch portion 53 of the existing tunnel 50 is left as it is and the side wall concrete is newly installed to secure an enlarged tunnel cross section. A significant increase in A precast concrete lining arch 40 is constructed on the inner peripheral surface of the arch portion 53 of the expansion tunnel 1. The precast concrete lining arch 40 of the present embodiment has a substantially semicircular arch structure in which 2-3 arches are assembled, and an arch portion is formed by using a gate-type movable mount or a dedicated installation machine (not shown) and an aerial work vehicle. 53 is assembled along the inner peripheral surface. At that time, a gap filling portion 41 is constructed by a waterproof sheet (not shown) and air mortar as a countermeasure against water leakage of the existing arch portion 53. The road surface 30 in the tunnel is constructed by a precast concrete paving plate that does not require a concrete curing period.

  Hereinafter, a series of construction situations (steps 1 to 8) of the existing tunnel lowering method according to another embodiment will be described with reference to FIGS.

  FIG. 13 shows that the pile 10 and the receiving girder 11 are installed at a predetermined pitch in the longitudinal direction over the entire length of the tunnel of one lane 5 in the existing tunnel 50 of the opposite two lanes, and the lining plate 12 is laid on the receiving girder 11, The construction situation (step 1) which constructs a temporary road is shown. This work is done day and night with one-lane restrictions. In the figure, an assumed excavation bottom G after lowering is shown for widening. Although the pile 10 uses the H-shaped steel pile as a temporary pile in this construction example, the kind of pile is not ask | required.

  FIG. 14 shows a construction situation (step 2) in which a similar construction work of the lining board 12 is performed in the other lane 6 after the completion of the construction shown in FIG. As a result, the entire surface of the existing tunnel 50 is covered with the lining plate 12 and becomes a temporary road for later construction.

  FIG. 15 shows the construction status (step 3) of the board lowering excavation work under the lining of the temporary road of one lane 5. As shown in the figure, the work space 7 is a narrow space where the piles 10 are densely packed. Therefore, excavation is performed by a small self-propelled excavator (not shown) so as not to block the passage of vehicles on the temporary road. In addition, it is preferable to extend a carry-out route (not shown) for continuously carrying out the excavated earth and sand to the outside of the tunnel well opening according to the progress.

  In the down excavation shown in FIG. 15, since the excavation is performed under the side wall leg portion of the existing tunnel, it is necessary to newly provide support for the arch portion. Therefore, in this construction example, a part of the existing side wall concrete 54 is beaten, and the shotcrete 20 and the rock bolt 21 are constructed on the ground surface exposed by excavation. The spraying thickness of the shotcrete 20, the number of lock bolts 21, and the length are determined by designing as appropriate according to the condition of the target ground. As a result, it is possible to reliably support the arch portion and to stabilize the support of the widened portion.

  FIG. 16 shows a construction situation (step 4) in which the side wall concrete 24 is constructed on the side wall after excavating the board. As shown in the figure, the side wall concrete 24 has a substantially L-shape consisting of a side wall 24a integrated with a part of the side wall concrete 54 of the existing tunnel and a bottom plate 24b, and the load transmitted from the arch to the side wall 24a is the bottom plate 24b. It is definitely supported. The side wall concrete 24 is constructed by in-situ concrete, but a precast concrete member manufactured in a factory having a predetermined size and shape can be carried into the site and assembled. In this case, in order to integrate the precast concrete member with the shot side concrete 20 on the back side, the side wall concrete 54 of the existing tunnel, and the precast concrete member, an adhesive resin such as an epoxy resin is filled between them. Is preferred.

  FIGS. 17 and 18 show the state of excavation under the lining in the other lane 6 (FIG. 7: step 5) and the construction of the side wall concrete 24 (FIG. 8: step 6). Thus, the excavation work in one lane 5 and the side wall concrete construction work are independent of the excavation work in the other lane 6 and the side wall concrete construction work. The work can be performed in parallel with the work of the other lane delayed by a predetermined distance from the rear of the work of the other lane. Alternatively, the work in the other lane may be performed after the work in one lane is completed over the entire length of the tunnel. Furthermore, you may make it advance the operation | work of both lanes toward the opposite direction. In this way, excavation in each lane, formwork assembly, concrete placement work, depending on the situation (for example, the amount of traffic in the tunnel, the length of the construction period, the number of construction machines) It is preferable to determine the process appropriately.

  FIG. 19 shows a construction situation (step 7) in which the pile 10 and the lining board 12 of the lane 6 are removed as a lane restriction for only the lane 5, and the roadbed work 31 and the drainage work 32 are constructed on the widened excavation surface. ing. As shown in the figure, the building limit 2 based on the road surface 30 of the enlarged tunnel 1 after widening can be set in the enlarged tunnel 1 so as not to interfere with the arch portion 53.

  FIG. 20 shows the construction situation (step 8) in which the road is replaced with the widened lane 6 and the roadbed 31 and the drainage 32 of the lane 5 are subsequently constructed. As shown in the figure, in this construction example, by lowering the road surface 30 of the expansion tunnel 1 by about 1 m from the road surface of the existing tunnel, it is possible to reliably secure the building limit 2 assuming the passage of a large vehicle. .

  In parallel with the road paving work, the precast concrete lining arch 4 is assembled on the inner peripheral surface of the arch portion 53 of the expansion tunnel 1. The precast concrete lining arch 40 has a substantially semicircular arch structure in which arches of 2 to 3 blocks are assembled. The inner circumference of the arch portion 53 is formed by using a gate-type movable stand or a dedicated installation machine (not shown) and an aerial work vehicle. Assembled along the surface. At that time, a gap filling portion 41 is constructed by a waterproof sheet (not shown) and air mortar as a countermeasure against water leakage of the existing arch portion 53. The road surface 30 in the tunnel is constructed by a precast concrete paving plate that does not require a concrete curing period.

  Note that the present invention is not limited to the two embodiments described above, and various modifications can be made within the scope indicated in each claim. In other words, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Expansion tunnel 2,52 Construction limit 5,6 Lane 7 Work space 10 Pile 11 Receiving girder 12 Covering board 20 Shotcrete 21 Rock bolt 24,54 Side wall concrete 30 Road surface (precast concrete pavement)
31 Roadbed 32 Drainage 33 Surface pavement 35 Backfill 40 Precast concrete lining arch 50 Existing tunnel 53 Arch

In order to achieve the above object, the present invention constructs a pile at a predetermined pitch in the longitudinal direction below the road surface of an existing tunnel, constructs a girder using this pile, and installs a lining plate on the girder. Laying and constructing a temporary road surface, then excavating the lower space of the lining plate down to a predetermined excavation bottom and excavating under the side wall legs of the existing tunnel to expose part of the existing side wall concrete The work up to the placement of the new side wall concrete that supports the existing side wall surface and supports the existing arch part and a part of the existing side wall concrete is positioned at a predetermined interval along the longitudinal direction of the existing tunnel. The construction is performed sequentially for each construction block to be constructed, and a tunnel cross section is constructed in which the cross section is expanded to the bottom of the excavation.

The existing tunnel consists of two lanes, to construct a temporary road surface by the lining plate over both lanes, subsequently, sequentially performs a construction to the newly sidewall concrete from the board lowered drilling both lane, both lanes after expansion It is preferable to perform the roadbed work in order.

The existing tunnel is composed of two lanes, and in one lane and the other lane, the traffic lanes are replaced, and the temporary road surface is constructed in both lanes sequentially by the lining plates, and then the lanes are replaced again. sequentially performed construction to the newly sidewall concrete from the board lowered drilling both lanes done, it is preferable to successively perform roadbed Engineering in both lanes of the enlarged further performs Sheng replacement of traffic lanes.

It is preferable that the work from the excavation under the side wall legs to the placement of the new side wall concrete is performed at predetermined intervals alternately between the longitudinal direction of the existing tunnel and both side walls of the tunnel cross section.

The new side wall concrete is preferably constructed so as to be integrated with a part of the existing side wall concrete .

Tunnel lining section of after the expansion is preferably to have closure by new inverted shape.

Tunnel road after the expansion is preferably laid precast concrete pavement on the roadbed on the excavation bottom.

Claims (10)

A pile is constructed at a predetermined pitch in the longitudinal direction under the road surface of the existing tunnel, a girder is constructed using this pile, and a temporary road surface is constructed by laying a lining plate on this girder,
Excavating the lower space of the lining plate down to a predetermined excavation bottom, excavating to the bottom of the side wall leg of the existing tunnel, supporting the exposed ground wall side surface,
Provide side wall concrete to support the arch part of the existing tunnel,
A method for lowering an existing tunnel, characterized in that an enlarged cross-section is secured with the bottom surface of the excavation as a road surface after enlargement. The existing tunnel consists of two lanes, constructs a temporary road surface with the lining plate over both lanes,
Subsequently, the lower digging in both lanes and the side wall concrete construction were carried out sequentially.
The method for lowering an existing tunnel according to claim 1, wherein roadbed works in both lanes after widening are sequentially performed. The existing tunnel is composed of two lanes, and in one lane and the other lane, the traffic lane is replaced and the temporary road surface is constructed by the lining plates in both lanes sequentially.
Subsequently, the lanes of the traffic lanes were replaced, and excavation of both sides of the lanes and construction of side wall concrete were sequentially performed.
The method of lowering the existing tunnel according to claim 1, further comprising replacing the traffic lane and sequentially performing roadbed construction in both lanes after widening.   The excavation to the lower side of the side wall leg, the support of the ground wall side surface, and the construction of the side wall concrete are performed at predetermined intervals along the longitudinal direction of the existing tunnel. The method for lowering the existing tunnel according to claim 3.   The excavation to the lower side of the side wall leg, the support of the side wall surface of the ground and the construction of the side wall concrete are performed by alternately separating the longitudinal direction of the existing tunnel and both side walls of the tunnel cross section at a predetermined interval. The method for lowering the existing tunnel according to claim 1 or 2.   The downhill construction method for an existing tunnel according to claim 1, wherein the natural mountain side wall surface is supported by shotcrete and a rock bolt.   The method for lowering an existing tunnel according to claim 1, wherein the side wall concrete is constructed so as to be integrated with a part of the side wall of the existing tunnel.   The method of lowering an existing tunnel according to claim 1, wherein the surface of the existing tunnel is covered with a waterproof sheet and a precast concrete lining member, and filled with air mortar.   2. The tunnel lowering method for an existing tunnel according to claim 1, wherein the lining of the tunnel after widening has a shape in which an invert is closed.   The method of lowering an existing tunnel according to claim 1, wherein the road surface of the tunnel after widening is formed by laying a precast concrete paving plate.

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