JP6751260B2 - Construction method of large section tunnel - Google Patents

Description

The present invention relates to a method of constructing a large-section tunnel that is applied when constructing a large-section tunnel using a plurality of small-diameter shield tunnels, particularly when providing a widened portion in the shield tunnel.

In the shield tunnel, it is necessary to widen the tunnel cross section at the branching/merging portion, typically, the branching/merging portion at the junction between the main tunnel and the ramp tunnel.

In the case of road tunnels, the junctions and junctions of tunnels often have a large cross section with a width exceeding 20 m, and shield machines (shielding machines, hereinafter simply referred to as shields) with diameters exceeding 15 m are now being manufactured. However, it is not realistic to excavate the entire section of the limited area, which is the junction, with a shield machine.

Under such circumstances, as a technology that can widen the cross section of the shield tunnel, a small-diameter shield tunnel consisting of multiple pieces along the periphery of the planned construction area where the branch and merge part will be constructed is installed along the tunnel axis direction of the shield tunnel. A method of arranging a plurality of them and then constructing a RC skeleton into a cylindrical shape by using them to form an outer shell, and then excavating an inner region thereof to construct a branching and joining portion has been developed (Patent Documents 1 to 1). 4).

In these construction methods, the small-diameter shield tunnel is used as a receiving structure to support the surrounding earth pressure, and the RC structure is continuously constructed by cutting the small-diameter shield tunnel. Until construction, it is important to prevent water leakage from surrounding rocks and prevent collapse of the rocks to ensure safety.

JP, 2014-43738, A Japanese Patent No. 4228311 Japanese Patent No. 4958035 Japanese Patent No. 5605522 JP, 2005-151675, A

Here, since a plurality of small-diameter shield tunnels need to be arranged according to the size of the tunnel cross section at the branching/merging portion, the interval between adjacent small-diameter shield tunnels becomes large at the cross-section position where the cross section is large. In each of the construction methods described in Patent Documents 1 to 4, the surrounding ground must be improved on a larger scale in order to secure the above-mentioned water stoppage and safety.

On the other hand, a construction method has also been proposed in which the number of small-diameter shield tunnels is changed for each cross-section position according to the size of the tunnel cross-section at the branching/merging portion (Patent Document 5). Since the intervals between the shield tunnels can be made substantially constant, it is not necessary to carry out ground improvement for securing waterproofness and safety on an excessive scale.

In addition, according to the above-mentioned construction method, it is possible to keep the distance between the small-diameter shield tunnels small, so that of the two small-diameter shield tunnels that are adjacent to each other, two small-diameter shield tunnels are arranged in different angular directions from each other. A gap between the small-diameter shield tunnels is provided by extending the ridges and connecting the two ridges with two ridges that are similarly extended from the other small-diameter shield tunnel at their tips. Can be securely closed, and it becomes easier to secure the waterproofness at the above-mentioned locations only by backfilling, and even if ground improvement work is separately required, the extent and extent of improvement can be minimized. ..

However, in order to provide the above-mentioned ridge, a side cutter capable of laterally excavating the circular cross-sectional space excavated by the cutter head of the small-diameter shield is provided in a form protruding from the peripheral surface of the small-diameter shield. Must be provided on the small diameter shield.

Therefore, when the small-diameter shield is started and reached, the side cutter pushes and spreads the annular water-stop member provided at the rim of the wellhead to separate the annular water-stop member from the peripheral surface of the small-diameter shield. I was concerned.

In addition, it is necessary to provide two sets of the above-mentioned ridges, and two ridges facing each other must be connected to each other. Therefore, accuracy is required to form the ridges. Was also occurring.

By the way, this problem also occurs when the above configuration is applied to a construction method that does not change the number of small-diameter shield tunnels, for example, each construction method described in Patent Documents 1 to 4.

The present invention has been made in consideration of the above-mentioned circumstances, and when the small-diameter shield is started and reached without incurring a great cost for securing water-stopping and safety between two adjacent small-diameter shield tunnels. It is an object of the present invention to provide a method for constructing a large-section tunnel capable of preventing a decrease in water shutoff at a wellhead.

In order to achieve the above object, the method for constructing a large cross section tunnel according to the present invention is, as described in claim 1, a small-diameter shield tunnel comprising a plurality of small diameter tunnels along the periphery of a construction planned region where the large cross section tunnel is constructed. Construction of a large-section tunnel that extends in the tunnel axis direction of the large-section tunnel, constructs an outer shell using the plurality of small-diameter shield tunnels as a receiving structure, and then excavates an inner region surrounded by the outer shell. In the method
When excavating the ground with a small-diameter shield in constructing the small-diameter shield tunnel, when adjacent small-diameter shield tunnels are pre-constructed, the preceding construction side is behind the shield segment of the pre-constructed small-diameter shield tunnel. By cutting a part of the backfilling area that spreads out to the side and excavating the side ground near the backfilling area, a side space along the tunnel axis direction is formed, and adjacent small-diameter shield tunnels are still formed. When not constructed, by excavating the lateral ground on the unconstructed side, a lateral space along the tunnel axis direction is formed,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side ,
The small-diameter shield is a small-diameter shield provided with a side cutter that can freely move in and out along the radial direction. When retracting and forming each of the lateral spaces, the side cutter is projected outward from the peripheral surface of the shield body .

Further, in the method for constructing a large-section tunnel according to the present invention, the expanded backfilling area is provided so that the construction range at the time of constructing the outer shell does not extend to the adjacent ground extending outside the expanded backfilling area. To form.

Further, in the method for constructing a large-section tunnel according to the present invention, the construction-scheduled area is set as a width-expansion area of the shield tunnel, and a cross-sectional position at which the cross-section of the width-expansion area is maximized is set as a reference cross-section position. A section having substantially the same position and cross-section size is a large-section section, and a section having a cross-section size smaller than the reference cross-section position and whose size does not substantially change is a small-section section or a cross-section. In the large section section, the plurality of small-diameter shield tunnels are arranged in the widening planned area in the large section section with a section in which the size gradually changes from the size in the large section section to the size in the small section section. In the small cross-section section, only the number necessary to be almost equal to the arrangement interval at the reference cross-section position is provided in the small cross-section section so that they are all arranged along the contour line of the cross-section. In the transition section, only the number required to be substantially equal to the arrangement interval at the reference cross-section position is provided in the transition section so as to be arranged along the cross-section contour line. The plurality of small-diameter shield tunnels are respectively extended so that they are arranged along the contour line of the cross-section and the rest are arranged behind them, and the cross-section contour of the plurality of small-diameter shield tunnels is arranged. When constructing two small-diameter shield tunnels that are adjacent to each other along a line, and a small-diameter shield tunnel that is arranged along the cross-sectional contour line and a small-diameter shield tunnel that is arranged behind the small-diameter shield tunnel so as to be adjacent to the small-diameter shield tunnel. The step of forming the lateral space and the step of filling are performed when building.

Further, in the method for constructing a large-section tunnel according to the present invention, a construction range for constructing the outer shell is such that, between the two small-diameter shield tunnels which are adjacent to each other along the contour line of the transverse section in the expanded backfilling region. The expanded backfilling area is formed so as not to reach the adjacent ground extending outside the expanded backfilling area formed in the above.

Further, as described in claim 5, the method for constructing a large cross-section tunnel according to the present invention is characterized in that a small-diameter shield tunnel consisting of a plurality of small-diameter tunnels is formed along the periphery of the construction planned region where the large cross-section tunnel is constructed. In a method of constructing a large cross-section tunnel, which extends in the direction of the tunnel axis, constructs an outer shell using the plurality of small-diameter shield tunnels as a receiving structure, and excavates an inner region surrounded by the outer shell,
When constructing the small-diameter shield tunnel, when excavating the ground with a small-diameter shield, if adjacent small-diameter shield tunnels are pre-constructed, on the preceding construction side, behind the shield segment of the pre-constructed small-diameter shield tunnel. By cutting a part of the backfilling area that spreads out to the side and excavating the side ground close to the backfilling area, a side space along the tunnel axis direction is formed, and adjacent small-diameter shield tunnels are still formed. When not constructed, by excavating the lateral ground on the unconstructed side, a lateral space along the tunnel axis direction is formed,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side ,
In the step of forming the lateral space, when excavating on the pre-constructed side, the depth on both sides of the pre-constructed small-diameter shield tunnel is set to be greater than the depth on the nearest angular position. When forming a lateral space and excavating on the unconstructed side, the lateral space should be made uniform so that the depth is almost uniform within a certain angle range centered on the angle position closest to the small-diameter shield tunnel to be constructed. To form .
Further, as described in claim 6, the method for constructing a large-section tunnel according to the present invention is characterized in that a small-diameter shield tunnel consisting of a plurality of small-diameter tunnels is provided along the periphery of a construction planned region where the large-section tunnel is constructed. In a method of constructing a large cross-section tunnel, which extends in the direction of the tunnel axis, constructs an outer shell using the plurality of small-diameter shield tunnels as a receiving structure, and excavates an inner region surrounded by the outer shell,
When constructing the small-diameter shield tunnel, when excavating the ground with a small-diameter shield, if adjacent small-diameter shield tunnels are pre-constructed, on the preceding construction side, behind the shield segment of the pre-constructed small-diameter shield tunnel. By excavating the side ground close to the backfilling area while cutting a part of the backfilling area that spreads out to the side, the lateral space along the tunnel axis direction is dug in the radial direction of the small diameter shield. If a small-diameter shield tunnel adjacent to the small-diameter shield is not constructed yet, the lateral space along the tunnel axis direction is formed by excavating the side ground on the unconstructed side . It is formed in a shape that is dug in the radial direction ,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side,
The area to be constructed is the area to be widened of the shield tunnel, and the cross-sectional position at which the cross-section of the area to be widened is the maximum is the reference cross-sectional position, and the reference cross-sectional position and the cross-sectional size are substantially the same. Is a large cross-section section, a section in which the size of the cross-section is smaller than the reference cross-section position and the size of which does not change substantially is a small cross-section section, and the size of the cross-section is smaller than the size in the large-section section. As a transition section a section that gradually changes to the size in the section section, in the large section section, so that the plurality of small-diameter shield tunnels are all arranged along the cross-section contour line of the widening planned region, In the small cross-section section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, In the transition section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, and the rest is the same. The plurality of small-diameter shield tunnels are respectively extended so as to be arranged behind, and two of the plurality of small-diameter shield tunnels that are adjacent to each other along the cross-section contour line are constructed. At the time of and at the time of constructing a small-diameter shield tunnel arranged along the cross-sectional contour line and a small-diameter shield tunnel arranged behind the small-diameter shield tunnel so as to be adjacent to the small-diameter shield tunnel, the step of forming the lateral space and the filling The process is performed.

In the method of constructing a large cross-section tunnel according to the present invention, when excavating the ground with a small-diameter shield in constructing a small-diameter shield tunnel, when adjacent small-diameter shield tunnels are constructed in advance, on the preceding construction side By cutting a part of the backfill area that extends behind the shield segment of the small-diameter shield tunnel that was previously constructed, and excavating the side ground near the backfill area, a side space along the tunnel axis direction. To form.

On the other hand, when adjacent small-diameter shield tunnels have not been constructed yet, a lateral space along the tunnel axis direction is formed by excavating the lateral ground on the unconstructed side.

These lateral spaces are formed in such a manner that the excavation space having a circular cross section formed by the cutter head provided at the tip of the small-diameter shield is expanded in the radial direction, that is, is dug in the radial direction.

In forming the lateral space on the pre-constructed side, when cutting a part of the backfill area, the angular position closest to the pre-constructed small-diameter shield tunnel should be avoided so as not to interfere with the pre-constructed small-diameter shield tunnel. The typical example is to make the depth on both sides larger than the depth on the side.When forming the lateral space on the unconstructed side, center the angular position closest to the small-diameter shield tunnel to be constructed. It is a typical example to form so that the depths are substantially uniform within a certain angle range.

Once the above-mentioned lateral space has been formed, in parallel with or after that, by filling the lateral space with a flowable solidifying material, on the preceding construction side, the expansion which is continuously integrated with the above-mentioned backfilling region is performed. A backfill area is formed, and a new backfill area is formed on the unconstructed side.

In this way, the expanded backfilling area formed between two adjacent small-diameter shield tunnels ensures water shutoff and safety against landslides, eliminating the need for major ground improvement when constructing the outer shell. In addition, unlike the conventional method, it is not necessary to construct a complicated structure in which two sets of two ridges are provided and the opposing ridges are connected to each other at their tips.

When excavating the ground with a small-diameter shield, as described above, there are cases where adjacent small-diameter shield tunnels are pre-constructed and cases where they are not yet constructed. Thus, while either side may be the unconstructed side, either side may be the pre-constructed side, such as at the end of the construction.In the former case, new backfilling is performed on both sides. Regions are formed respectively, and in the latter case, extended backfill regions are formed on both sides.

The expanded backfill area is sufficient if a certain level of water stopping and safety against ground collapse are secured when constructing an outer shell between two adjacent small-diameter shield tunnels. It is not necessary to cover the entire construction range, and it is possible to configure to supplement the function of the expanded backfilling area while partially implementing water-stopping measures such as chemical injection, but the construction range when constructing the outer shell is the same as the above. If the expanded backfilling area is formed so as not to reach the adjacent ground extending outside the expanded backfilling area, the outer shell construction work is performed in the expanded backfilling area, It is possible to omit or reduce additional water shutoff measures.

In the method for constructing a large-section tunnel according to the present invention, the small-diameter shield tunnel is an expression representing a relative concept to the large-section tunnel, and its diameter is not restricted to the recognition of those skilled in the shield construction method. As the small-diameter shield tunnel of the present invention, a case where a shield tunnel having a size called a medium diameter in the field of the shield construction method, for example, about 4 m is used is also included in the present invention.

In addition, the method for constructing a large-section tunnel according to the present invention is such that a plurality of small-diameter shield tunnels are extended along the periphery of an area where a large-section tunnel is to be constructed, and then the outer shell is formed by utilizing the small-diameter shield tunnel. After construction, it is a method of excavating the inside of the outer shell to form a large cross-section tunnel space, and when constructing the outer shell, water resistance and safety decrease due to separation between two adjacent small-diameter shield tunnels. It is applicable to all cases where it is necessary to prevent, and how to construct multiple small-diameter shield tunnels is arbitrary, and the use of large-section tunnels is also arbitrary. It is also arbitrary whether the number of small-diameter shield tunnels changes or is constant.

For example, the area where the large-section tunnel is to be constructed is the area where the shield tunnel is to be widened, and in the large-section section, multiple small-diameter shield tunnels are all arranged along the cross-section contour line of the area to be widened. Of the multiple small-diameter shield tunnels in the section, the number of multiple tunnels in the transition section should be set so that only the number necessary to be approximately the same as the arrangement interval at the reference section position is arranged along the contour line of the cross section. Among the small-diameter shield tunnels in the above, only a plurality of tunnel tunnels should be arranged along the contour line of the cross section and the rest should be arranged behind them, in order to be almost the same as the spacing at the reference cross section position. It is also applicable when extending the small diameter shield tunnels.

In such a case, among the plurality of small-diameter shield tunnels, when forming two small-diameter shield tunnels that are adjacent to each other along the cross-section contour line, the above-described forming process and filling process of each lateral space are performed. The small-diameter shield tunnel arranged along the cross-section contour line is separated from the cross-section contour line and separated from another small-diameter shield tunnel, or the small-diameter shield tunnel separated from the cross-section contour line is the cross-section contour line. At the location where the small-diameter shield tunnels arranged along the line are inserted so as to interrupt, the distance between two small-diameter shield tunnels that are adjacent to each other along the cross-sectional contour line becomes large, and The filling process may be difficult to perform.

However, even in that case, since the small-diameter shield tunnels that are going to leave or enter are closely arranged behind the small-diameter shield tunnels along the cross-sectional contour line, each side mentioned above when constructing these If the forming process and the filling process of the rectangular space are performed, the small-diameter shield tunnel along the cross-section contour line and the small-diameter shield tunnel arranged behind it are securely closed, and as a result, the cross-section contour line is formed. Even if the distance between two small-diameter shield tunnels adjacent to each other along the path becomes large, it is possible to secure the water stoppage and the safety against landslides without major ground improvement.

The widened part is typically formed as a branching and joining part of the shield tunnel, especially as a branching and joining part at the junction of the main tunnel and the ramp tunnel, but it is constructed for an emergency evacuation zone, an emergency parking zone or any other purpose. The widened part is included.

Of the expanded backfill area, the expanded backfill area formed between the two small-diameter shield tunnels that are adjacent to each other along the contour line of the cross section does not necessarily cover the entire construction range when constructing the outer shell, as described above. Although it is not necessary, it is possible to construct a structure that complements the function of the expanded backfill area while partially performing water-stopping measures such as chemical injection, but the construction range when constructing the outer shell is outside the expanded backfill area. If the expanded backfill area is formed so that it does not extend to the adjacent ground that spreads over, the outer shell construction work will be performed in the expanded backfill area, and additional water stop measures will be taken. It is possible to omit or reduce it.

On the other hand, in the expanded backfill area, the expanded backfill formed between the small-diameter shield tunnel arranged along the contour line of the transverse section and the small-diameter shield tunnel arranged behind the small-diameter shield tunnel so as to be adjacent to the small-diameter shield tunnel. As for the area, since the latter small-diameter shield tunnel is separated from the contour line of the cross section, it is inherently difficult to cover the entire construction range when constructing the outer shell in the expanded backfill area. There is a risk that groundwater will infiltrate the construction area when constructing the outer shell from the opposite side where the filling area is formed.In such a case, the area not covered by the expanded backfilling area may be injected or frozen by a method such as chemical injection. You can stop the water separately.

How to form each of the above-mentioned lateral spaces is arbitrary, but, for example, the small-diameter shield is a small-diameter shield provided with a side cutter that can move in and out along the radial direction, and the small-diameter shield is started and reached. In doing so, the side cutter is retracted inward from the shield body peripheral surface of the small-diameter shield, and when forming the lateral spaces, the side cutter is placed outside the shield body peripheral surface. It is possible to adopt a configuration in which it projects.

According to this structure, since the small-diameter shield can be started and reached without any protrusion on the peripheral surface of the small-diameter shield, the annular water blocking member provided at the wellhead of the starting area is It is possible to prevent a decrease in water stoppage at the wellhead, since there is no possibility that the material will come into close contact with and there will be a gap.

An overall plan view showing how the outer shell is constructed by surrounding the widened portion of the main tunnel 1 with a plurality of small-diameter shield tunnels 4-1 to 4-24 by using the method for constructing a large-section tunnel according to the present embodiment. .. It is a cross-sectional view of FIG. 1, (a) is each AA line, (b) is each cross-sectional view along the BB line. Similarly, it is a cross-sectional view of FIG. 1, (a) is a C-C line, (b) is a cross-sectional view along the D-D line. It is the figure which showed a mode that the small diameter shield tunnel 4-1 was built in a large section section, (a) is a cross-sectional view which showed the side space 41,41 was formed by the overcut, (b) is The front view which showed the small diameter shield 42 used for it, (c) is the cross-sectional view which showed a mode that the side space 41, 41 was filled with a backfill material. FIG. 4 is a transverse cross-sectional view showing how a small-diameter shield tunnel 4-2 is continuously constructed. FIG. 6 is a transverse cross-sectional view showing how to construct the small diameter shield tunnels 4-1 to 4-5 in the transition section. Similarly, a cross-sectional view showing a state in which the construction is completed. FIG. 6 is a transverse cross-sectional view showing a manner of constructing small-diameter shield tunnels 4-2 to 4-7 (excluding small-diameter shield tunnel 4-5) in the small cross-section section.

Hereinafter, an embodiment of a method for constructing a large cross section tunnel according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example in which the present invention is applied to a case where a widened portion as a large-section tunnel is formed in the main line tunnel in order to provide a branching and joining portion for joining the main line tunnel 1 as the shield tunnel with the ramp tunnel 2. Then, the overall plan view showing the front receiving structure composed of a plurality of small-diameter shield tunnels 4-1 to 4-24, and FIGS. 2(a) and 2(b) are lines AA and B in FIG. 1, respectively. 3A and 3B are cross-sectional views taken along line C-C and line D-D of FIG. 1, respectively.

As shown in these drawings, in the method of constructing a large-section tunnel according to the present embodiment, first, along the periphery of the widening planned region 3 of the main tunnel 1 which is a planned region where the large-section tunnel is constructed. A total of 24 small-diameter shield tunnels 4-1 to 4-24 are provided along the tunnel axis of the main tunnel.

These 24 small-diameter shield tunnels 4-1 to 4-24 serve as a front receiving structure when constructing the outer shell 71 required before excavation of the widening planned region 3.

The small-diameter shield tunnels 4-1 to 4-24 may be constructed by starting the small-diameter shield from the starting area 6 provided near the outside of the main tunnel 1.

In the starting area 6, a shield segment (not shown) of the main line tunnel 1 is partially cut open from the inside to insert and install a circumferential tunnel excavator, and the peripheral ground that extends outside the main line tunnel 1 by the circumferential tunnel excavator is installed. After excavating to form an annular space having a rectangular cross section, it is possible to cut open the remaining shield segment to expose it as an annular trench, and to launch a small-diameter shield from the annular trench. it can.

Here, as shown in FIG. 1, the small-diameter shield tunnels 4-1 to 4-24 have a cross-section position where the cross-section of the widened region 3 is the maximum, in the present embodiment, the vicinity of the starting area 6 is the reference cross-section position, The section having substantially the same cross-sectional size as the reference cross-section position is the large cross-section section, and the section having the cross-sectional size smaller than the reference cross-section position and having the size substantially unchanged is the small cross-section section. As shown in Fig. 2(a), the cross section of the widening planned area 3 is crossed in the large cross section as the transition section where the size of the cross section gradually changes from the size in the large cross section to the size in the small cross section. Place all along the surface contour.

On the other hand, in the small cross section section, as shown in FIG. 3(b), the number and the number of the small diameter shield tunnels 4-1 to 4-24 required to be almost equal to the arrangement interval at the reference cross section position. In the embodiment, only 18 are arranged along the contour line of the cross section.

In the transition section, as shown in FIG. 2B, the number of small-diameter shield tunnels 4-1 to 4-24, which are necessary to be almost equal to the arrangement interval at the reference cross-section position, are used. In the form, only 18 are arranged along the contour line of the cross section, and the remaining 6 small-diameter shield tunnels 4-1, 4,5, 4-9, 4-13, 4-17, 4-21 are , Behind a small-diameter shield tunnel, which is placed along the contour line of the cross section.

In constructing these 24 small-diameter shield tunnels 4-1 to 4-24, as described above, the small-diameter shield may be appropriately started from the starting area 6, but when performing ground excavation with the small-diameter shield. As described in detail below, while digging the side ground, the side space formed by the digging is filled with a fluidized solidifying material to provide a backfill area behind the shield segment. To form.

In the present embodiment, for convenience of description, in the large cross-section section and the transition section, natural ground excavation by the small-diameter shield for constructing the small-diameter shield tunnels 4-1 to 4-24 is performed in the ascending order of the figure numbers, and FIG. Speaking of a) and (b), it is performed sequentially clockwise, and in the small cross section section, six small-diameter shield tunnels 4-1, 4,5, 4-9, 4-13, 4-17, 4-21 are used. Except for the remaining 18 lines, the processes are performed in the ascending order of the figure numbers, that is, in the clockwise direction in FIG.

First, in the large cross section section, as shown in FIG. 2(a), 24 small-diameter shield tunnels 4-1 to 4-24 are constructed so that their intervals are equal along the contour line of the cross section. When excavating the ground, the side where adjacent small-diameter shield tunnels are pre-constructed is the pre-construction side, the side not yet constructed is the unconstructed side, and the pre-construction side is the pre-constructed small-diameter shield tunnel. While cutting a part of the backfill area that extends behind the shield segment of, the side ground along the tunnel axis direction is formed by excavating the side ground near the backfill area. Then, by excavating the lateral ground, lateral spaces are formed along the tunnel axis.

FIG. 4 shows a state in which the small-diameter shield tunnel 4-1 is constructed, and at the time of excavating the ground for constructing the small-diameter shield tunnel, the adjacent small-diameter shield tunnels have not yet been constructed. , As shown in Fig. 6(a), by digging so that the depth is almost uniform in a certain angle range centered on the angle position closest to the small-diameter shield tunnel 4-2 to be constructed, A space 41 is formed on the right side of the figure. Also on the left side of the figure, the lateral space 41 is formed by digging so that the depth becomes substantially uniform within a certain angle range centered on the angle position closest to the small-diameter shield tunnel 4-24 to be constructed. It forms similarly.

FIG. 4B is a view of the small-diameter shield 42 capable of forming the lateral spaces 41, 41 from the tip side, and a cutter head 43 (shield body and shield body) provided at the tip of the shield body (not shown). (The same diameter) is rotated about an axis perpendicular to the plane of the drawing (hereinafter referred to as the machine axis) to excavate the front ground, and the side cutter 47 installed on the cutter head causes the cutter head 43 to form a circular cross-section. The excavation space can be expanded laterally.

The side cutter 47 is a swing cutter arm 46 installed on the outer peripheral ring 48 of the cutter head 43 so as to be swingable around the machine axis, and a rod cutter at a position slightly separated from the swing center of the swing cutter arm. It is composed of a hydraulic cylinder 45 whose tip is connected.

The oscillating cutter arm 46 extends in the opposite direction from the oscillating center so that the two cutting arms 44a and 44b are entirely bent toward the shield body, in other words, the whole is a boomerang. In addition to the above, the cutting bits 50 are arranged side by side in a row on the side of the long edge of each cutting arm that is opposite to the shield body, that is, the edge that is the ground side in the excavation posture. ..

The hydraulic cylinder 45 is connected to the spokes 49 of the cutter head 43 on the cylinder side and holds the stroke of the rod in the neutral position to retract the entire swing cutter arm 46 to the inside of the peripheral surface of the shield body. Can be done (solid line in the figure (b)).

On the other hand, in the hydraulic cylinder 45, by extending the rod from the neutral position, the swing cutter arm 46 swings counterclockwise to cause the cutting arm 44b to project outward from the peripheral surface of the shield body, and By contracting from the neutral position, the swinging cutter arm 46 is swung clockwise so that the cutting arm 44a projects outward from the peripheral surface of the shield body, and the entire side cutter 47 rotates the cutter head 43. Since it rotates around the axis as a whole in conjunction with, if the rod expanding and contracting operation is added to the clockwise and counterclockwise rotating operation of the cutter head 43, the excavating space having a circular cross section by the cutter head 43 can be formed into a desired cross section. It can be expanded radially in shape.

When the small-diameter shield 42 is started from the starting area 6, the rod of the hydraulic cylinder 45 is held in the neutral position and the swing cutter arm 46 of the side cutter 47 is retracted to the inside of the peripheral surface of the shield body. After passing through the wellhead of No. 6, the swing cutter arm 46 is appropriately swung as described above.

If the side spaces 41, 41 along the tunnel axis direction are formed by excavating the side ground by using the side cutter 47 as shown in FIG. While assembling the shield segment 51 at the tail portion of the same, by filling the backspaces 41, 41 extending behind the shield segments with a backfill material as a fluidized solidifying material, new backfill areas 52, 52 are formed. To do.

Next, in constructing the small-diameter shield tunnel 4-2 on the right side of the pre-constructed small-diameter shield tunnel 4-1, as in the case of constructing the small-diameter shield tunnel 4-1. Starting the small-diameter shield 42 from the starting area 6, and then cutting a part of the backfilling area 52 extending behind the shield segment 51 of the previously constructed small-diameter shield tunnel 4-1 as shown in FIG. The lateral space 61 on the side of the preceding construction along the tunnel axis direction is formed by excavating the lateral ground close to the backfill area.

The side space 61 may be formed by using the side cutter 47 of the small diameter shield 42, as in the case of forming the side space 41 of the small diameter shield tunnel 4-1.

In forming the side space 61, when cutting a part of the backfill area 52, an angle closest to the small-diameter shield tunnel 4-1 so as not to interfere with the pre-constructed small-diameter shield tunnel 4-1. The depth at both sides should be larger than the depth at the position.

On the other hand, on the unconstructed side where the adjacent small-diameter shield tunnels 4-3 have not yet been constructed, by excavating the side ground, in the same manner as the side space 41 of the small-diameter shield tunnel 4-1, the tunnel axial direction is obtained. To form a lateral space 41 along.

When the side spaces 41 and 61 are formed, as shown in FIG. 5(b), while the shield segment 51 is assembled with the tail portion of the small-diameter shield 42, the side of the unconstructed side that expands behind the shield segment By filling the space 41 with the backfill material, a new backfill region 52 is formed.

On the other hand, on the preceding construction side, by filling the lateral space 61 extending behind the shield segment 51 with the backfill material, the extended backfill area 62 that is continuously integrated with the backfill area 52 of the small diameter shield tunnel 4-1 is formed. Form.

The expanded backfill area 62 is formed by continuously integrating backfill materials injected from two adjacent small-diameter shield tunnels so as to sandwich them in an X-shaped cross section. In other words, the outer shell construction range between two adjacent small-diameter shield tunnels is included in the expanded backfilling area so that the construction range when constructing the outer shell 71 does not extend to the adjacent ground extending outward. To be formed.

By repeating the above procedure, the small-diameter shield tunnels 4-1 to 4-23 are sequentially constructed in the clockwise direction while forming the expanded backfill area 62 between them in the large cross-section section, and the small-diameter shield tunnel 4 is formed. By constructing -24 so that the extended backfill regions 62, 62 are formed on both sides with the preceding construction side being formed, the small-diameter shield tunnels 4-1 to 4-24 are cross-sectional contours of the region 3 to be widened. Arrange annularly at equal intervals along the line.

Next, the transition section shown in the cross-sectional view (FIG. 2(b)) taken along the line BB of FIG. 1 is generally performed in the same manner as the large section section, but in the transition section, as described above, the small-diameter shield tunnel is used. Of 4-1 to 4-24, the number required to be almost equal to the arrangement interval at the reference cross-section position, in the present embodiment, only 18 are arranged along the cross-section contour line, and the remaining 6 The small-diameter shield tunnels 4-1, 4,5, 4-9, 4-13, 4-17, 4-21 are arranged behind the small-diameter shield tunnels arranged along the contour line of the cross section.

Therefore, in constructing the small-diameter shield tunnel 4-1, the lateral spaces to be formed on both sides of the small-diameter shield tunnel 4-1 have the angular positions closest to the small-diameter shield tunnels 4-2 and 4-24 to be constructed in FIG. 6(a). As can be seen, when the small-diameter shield tunnel 4-1 is viewed right above, it is diagonally downward right and diagonally downward left, so that the lateral space has a depth within a certain angular range centered on these two diagonal angles. The back-filling regions 52 and 52 are formed by filling the respective side spaces with a back-filling material, and the small-diameter shield tunnel 4-2 is continuously formed on the right side thereof. As constructed, an extended backfill area 62 is formed as described above.

Regarding the small-diameter shield tunnels 4-5, 4-9, 4-13, 4-17, 4-21, one is the pre-construction side and the other is the non-construction side at the time of constructing them, but the small-diameter shield tunnel 4 -5 will be described as an example, as shown in FIG. 6(b), on the non-constructed side, the side ground is excavated so that the depth becomes substantially uniform within a certain angle range centered on the above-mentioned oblique angle. To form the lateral space 41, and on the preceding building side, a part of the backfilling region 52 on the preceding building side is cut so that the depths on both sides of the preceding building side are larger than the depth at the above-mentioned oblique angle. Meanwhile, a lateral space 61 is formed by excavating a lateral ground close to the backfill region, and then a new backfill region is formed by filling the lateral space 41 on the unconstructed side with a backfill material. As shown in FIG. 7, the expanded backfilling area 62 that is continuously integrated with the backfilling area 52 of the small-diameter shield tunnel 4-4 is formed as shown in FIG. To form.

Of the expanded backfill area 62, the expanded backfill area formed between the two small-diameter shield tunnels adjacent to each other along the contour line of the cross section has an adjacent land extending outside the expanded backfill area, as described above. It is formed so that the construction range when constructing the outer shell 71 on the mountain does not extend.

As for the small section section shown in the sectional view (FIGS. 3(a) and 3(b)) taken along the line C-C or the line D-D in FIG. 1, as shown in FIG. The remaining 18 lines, except for 6 lines 4-5, 4-9, 4-13, 4-17 and 4-21, may be constructed in the same manner as the large section section.

Note that the six small-diameter shield tunnels 4-1, 4,5, 4-9, 4-13, 4-17, 4-21 are sufficiently separated from the cross-section contour line and separated from other small-diameter shield tunnels. Then, the two small-diameter shield tunnels that were adjacent to each other via the small-diameter shield tunnels are now directly adjacent to each other along the contour line of the transverse section at an arrangement interval equal to the arrangement interval at the reference cross-section position. At the time point, that is, when the state shown in FIG. 8 is reached, the role of the front receiving structure is completed, and therefore the extension of them is completed in a manner that the inflow of groundwater from the end is prevented.

If the small-diameter shield tunnels 4-1 to 4-24 are constructed in all sections, these small-diameter shield tunnels are used as a receiving structure to support surrounding earth pressure and water pressure, and these are cut open to form an RC frame into a cylindrical shape. To form the outer shell 71, and thereafter, the inner region thereof may be excavated to construct the branching and joining section.

As described above, according to the method of constructing a large cross section tunnel according to the present embodiment, the water blocking effect from the outside of the large cross section tunnel and the ground by the expanded backfilling region 62 formed between the two adjacent small diameter shield tunnels. Since safety against landslides is ensured, large-scale ground improvement is not required, and unlike the conventional construction method, two pairs of ridges, each consisting of two, are provided, and the opposing ridges are There is no need to build a complicated structure of connecting at the tip.

Further, according to the method of constructing the large cross-section tunnel according to the present embodiment, regarding the expanded back-filling region 62 formed between the two small-diameter shield tunnels that are adjacent to each other along the cross-section contour line, Since the expanded backfilling area is formed so that the construction range when constructing the outer shell 71 does not extend to the adjacent ground extending outward, the work of constructing the outer shell 71 is performed within the extended backfilling area 62. As a result, it will be possible to omit or reduce additional water shutoff measures.

Further, according to the method for constructing a large cross-section tunnel according to the present embodiment, the above-mentioned expanded backfill area 62 is provided between the small-diameter shield tunnel along the cross-section contour line and the small-diameter shield tunnel arranged behind it. Since it is formed, even if the distance between two adjacent small-diameter shield tunnels becomes large in the transition section where the number of small-diameter shield tunnels changes, outside of the widening planned area 3 without major ground improvement. It is possible to secure the safety against the earth pressure and the water pressure acting in the radial direction from the inside to the inside, and also the water stoppage against the groundwater inflow from the direction.

Further, according to the method of constructing the large cross section tunnel according to the present embodiment, the small diameter shield tunnels 4-1 to 4-24 are constructed using the small diameter shield 42 provided with the side cutter 47 that can freely move in and out along the radial direction. In addition, since the side cutter 47 is dug to form the side space 41 and the side space 61, the small-diameter shield can be started and reached without any protrusion on the peripheral surface of the small-diameter shield. Become.

Therefore, when the small-diameter shield 42 is started and reached, the annular water-stop member provided at the wellhead of the starting area 6 does not come into close contact with the peripheral surface of the small-diameter shield to cause a gap, thus reducing the waterstop at the wellhead. It becomes possible to prevent it.

In the present embodiment, the lateral space on the pre-construction side is formed such that the depths on both sides of the lateral space on the pre-construction side are larger than the depth on the angle position closest to the small diameter shield tunnel, and the lateral space on the non-construction side is formed. , The depth was formed to be almost uniform within a certain angle range centered on the angle position closest to the small-diameter shield tunnel to be constructed, but an extended backfill area was formed between two adjacent small-diameter shield tunnels. If so, the depth of forming the lateral space is arbitrary.

Further, in the present embodiment, an example in which the present invention is applied when the number of small-diameter shield tunnels surrounding the construction area of the large-section tunnel changes at the cross-section position, the number of small-diameter shield tunnels is constant depending on the cross-section position. In this case, the present invention can be applied.

Further, in the present embodiment, the side cutter 47 is dug to form the lateral spaces 41 and 61, but how to form these lateral spaces is arbitrary. Instead of the side cutter 47, a known cutting means can be adopted.

Further, although not particularly mentioned in the present embodiment, in the expanded backfill area 62, a small-diameter shield tunnel arranged along the contour line of the transverse section and a small-diameter shield arranged behind the small-diameter shield tunnel adjacent to the small-diameter shield tunnel. 7, a small-diameter shield tunnel 4-2 and a small-diameter shield tunnel 4-1, a small-diameter shield tunnel 4-4 and a small-diameter shield tunnel 4-5, or a small-diameter shield tunnel 4 in FIG. The expanded backfill area 62 formed between the −6 and the small diameter shield tunnel 4-5 is the same because the small diameter shield tunnel 4-1 and the small diameter shield tunnel 4-5 are separated from the contour line of the cross section. As can be seen in the figure, it is inherently difficult to cover the entire construction range when constructing the outer shell 71 in the expanded backfill area.

In this case, the area not covered by the expanded backfilling area should be covered with a chemical solution or frozen to prevent water from entering from the side opposite the expanded backfilling area. You can stop the water separately.

1-line tunnel (shield tunnel)
3 Planned widening area for shield tunnel (Planned area for large cross-section tunnel)
4-1 to 4-24
Small-diameter shield tunnel 41, 61 Side space 42 Small-diameter shield 47 Side cutter 51 Shield segment 52 Backfill area 62 Extended backfill area 71 Outer shell

Claims (6)

A plurality of small-diameter shield tunnels are provided along the periphery of the construction area where the large-section tunnel is constructed, extending in the tunnel axial direction of the large-section tunnel, and the plurality of small-diameter shield tunnels are used as a front receiving structure. In the method of constructing a large-section tunnel in which an inner region surrounded by the outer shell is excavated after the shell is constructed,
When excavating the ground with a small-diameter shield in constructing the small-diameter shield tunnel, when adjacent small-diameter shield tunnels are pre-constructed, the preceding construction side is behind the shield segment of the pre-constructed small-diameter shield tunnel. By cutting a part of the backfilling area that spreads out to the side and excavating the side ground close to the backfilling area, a side space along the tunnel axis direction is formed, and adjacent small-diameter shield tunnels are still formed. When not constructed, by excavating the lateral ground on the unconstructed side, a lateral space along the tunnel axis direction is formed,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side ,
The small-diameter shield is a small-diameter shield provided with a side cutter that can freely move in and out along the radial direction, and when the small-diameter shield is started and reached, the side cutter is placed inside the shield body peripheral surface of the small-diameter shield. A method for constructing a large cross-section tunnel, characterized in that the side cutters are projected outward from a peripheral surface of the shield body when the side cutters are retracted to form the lateral spaces . The method for constructing a large cross-section tunnel according to claim 1, wherein the expanded backfill region is formed so that a construction range for constructing the outer shell does not reach an adjacent ground extending outside the expanded backfill region. The area to be constructed is the area to be widened of the shield tunnel, and the cross-sectional position at which the cross-section of the area to be widened is the maximum is the reference cross-sectional position, and the reference cross-sectional position and the cross-sectional size are substantially the same. Is a large cross-section section, a section in which the size of the cross-section is smaller than the reference cross-section position and the size of which does not substantially change, is a small cross-section section, and the size of the cross-section is smaller than the size in the large cross-section section. As a transition section a section that gradually changes to the size in the section section, in the large section section, so that the plurality of small-diameter shield tunnels are all arranged along the cross-section contour line of the widening planned region, In the small cross-section section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, In the transition section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, and the rest is the same. The plurality of small-diameter shield tunnels are respectively extended so as to be arranged behind, and two of the plurality of small-diameter shield tunnels that are adjacent to each other along the cross-section contour line are constructed. At the time of and at the time of constructing a small-diameter shield tunnel arranged along the contour line of the cross section and a small-diameter shield tunnel arranged behind the small-diameter shield tunnel so as to be adjacent to the small-diameter shield tunnel, the step of forming the lateral space and the filling The method for constructing a large cross-section tunnel according to claim 1, wherein The construction area for constructing the outer shell is an adjoining ground that extends outside the expanded backfilling area formed between two small-diameter shield tunnels that are adjacent to each other along the contour line of the cross section among the expanded backfilling areas. The method for constructing a large cross-section tunnel according to claim 3, wherein the extended backfill region is formed so as not to reach a mountain. A plurality of small-diameter shield tunnels are provided along the periphery of the construction area where the large-section tunnel is constructed, extending in the tunnel axial direction of the large-section tunnel, and the plurality of small-diameter shield tunnels are used as a front receiving structure. In the method of constructing a large-section tunnel in which an inner region surrounded by the outer shell is excavated after the shell is constructed,
When excavating the ground with a small-diameter shield in constructing the small-diameter shield tunnel, when adjacent small-diameter shield tunnels are pre-constructed, the preceding construction side is behind the shield segment of the pre-constructed small-diameter shield tunnel. By cutting a part of the backfilling area that spreads out to the side and excavating the side ground near the backfilling area, a side space along the tunnel axis direction is formed, and adjacent small-diameter shield tunnels are still formed. When not constructed, by excavating the lateral ground on the unconstructed side, a lateral space along the tunnel axis direction is formed,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side ,
In the step of forming the lateral space, when excavating on the pre-constructed side, the depth on both sides of the pre-constructed small-diameter shield tunnel is set to be greater than the depth on the nearest angular position. When forming a lateral space and excavating on the unconstructed side, the lateral space should be made uniform so that the depth is almost uniform within a certain angle range centered on the angle position closest to the small-diameter shield tunnel to be constructed. A method for constructing a large-section tunnel, which is characterized in that it is formed . A plurality of small-diameter shield tunnels are provided along the periphery of the construction area where the large-section tunnel is constructed, extending in the tunnel axial direction of the large-section tunnel, and the plurality of small-diameter shield tunnels are used as a front receiving structure. In the method of constructing a large-section tunnel in which the inner region surrounded by the outer shell is excavated after the shell is constructed,
When constructing the small-diameter shield tunnel, when excavating the ground with a small-diameter shield, if adjacent small-diameter shield tunnels are pre-constructed, on the preceding construction side, behind the shield segment of the pre-constructed small-diameter shield tunnel. By excavating the side ground close to the backfilling area while cutting a part of the backfilling area that spreads out to the side, the lateral space along the tunnel axis direction is dug in the radial direction of the small diameter shield. If a small-diameter shield tunnel adjacent to the small-diameter shield is not constructed yet, the lateral space along the tunnel axis direction is formed by excavating the side ground on the unconstructed side . It is formed in a shape that is dug in the radial direction ,
In parallel with or after the step of forming the lateral space, by filling the lateral space with a fluidized solidifying material, on the preceding construction side, an expanded backfilling area that is continuously integrated with the backfilling area. And a method for constructing a large-section tunnel for forming a new backfill region on the unconstructed side,
The area to be constructed is the area to be widened of the shield tunnel, and the cross-sectional position at which the cross-section of the area to be widened is the maximum is the reference cross-sectional position, and the reference cross-sectional position and the cross-sectional size are substantially the same. Is a large cross-section section, a section in which the size of the cross-section is smaller than the reference cross-section position and the size of which does not change substantially is a small cross-section section, and the size of the cross-section is smaller than the size in the large-section section. As a transition section a section that gradually changes to the size in the section section, in the large section section, so that the plurality of small-diameter shield tunnels are all arranged along the cross-section contour line of the widening planned region, In the small cross-section section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, In the transition section, among the plurality of small-diameter shield tunnels, only the number necessary to be substantially equal to the arrangement interval at the reference cross-section position is arranged along the cross-section contour line, and the rest is the same. The plurality of small-diameter shield tunnels are respectively extended so as to be arranged behind, and two of the plurality of small-diameter shield tunnels that are adjacent to each other along the contour line of the cross section are constructed. At the time of and at the time of constructing a small-diameter shield tunnel arranged along the cross-sectional contour line and a small-diameter shield tunnel arranged behind the small-diameter shield tunnel so as to be adjacent to the small-diameter shield tunnel, the step of forming the lateral space and the filling A method for constructing a large cross-section tunnel, which comprises:

Images