Supporting construction method and supporting structure for tunnel weak surrounding rock transverse tunnel intersection

Abstract

The invention relates to the technical field of tunnel construction, and provides a tunnel weak surrounding rock transverse tunnel intersection supporting construction method and a supporting structure, an intersection is primarily supported in a subarea circulation footage excavation and segmented arch bar supporting mode, and a portal frame is installed at the intersection to be connected with an arch bar of a first circulation; and the second anchor pipe which is obliquely arranged towards the front end of the width digging direction of the main tunnel and the third anchor pipe which is obliquely arranged towards the rear end of the width digging direction of the main tunnel are used for anchoring the arch bars, so that early support after excavation is ensured, the advance support construction time is saved, and the construction is safer. The construction progress of the intersection is accelerated, the construction cost is reduced, the safety of operating personnel is ensured, a safe space is provided for lap joint construction of the next cycle of primary support, and rapid hole entering is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a tunnel soft surrounding rock cross tunnel intersection support construction method and support structure. Background Art

[0002] In the construction of mountain tunnel projects, it is increasingly common for tunnel entrances to be located on steep cliffs. When it is not possible to enter the tunnel through the main tunnel, construction is usually carried out through auxiliary channels such as working branch tunnels or inclined shafts. During the construction of the working branch tunnel, the construction of the intersection with the main tunnel is a difficult point. In the conventional branch tunnel to main tunnel construction process, the lateral excavation at the intersection will affect the self-stability of the surrounding rock, and the newly added support structure is difficult to fix and uses more materials, resulting in high resource consumption. In addition, low work efficiency and long operation time also increase the safety risks of on-site workers. Summary of the invention

[0003] The purpose of the present invention is to provide a tunnel soft surrounding rock cross tunnel intersection support construction method and support structure, which solves the problems of difficult fixing of the support structure, large amount of materials, low efficiency and long operation time in the construction of conventional branch tunnels to main tunnels.

[0004] The present invention is implemented by the following technical scheme: A tunnel soft surrounding rock cross tunnel intersection support construction method, characterized in that it includes the following steps:

[0005] Step 1: dig a pilot tunnel in the branch tunnel to enter the main tunnel, and expand the space for installing the portal frame, and the portal frame is anchored to the side wall of the intersection of the branch tunnel and the main tunnel through grouting of the first anchor pipe;

[0006] Step 2: Excavate in sections along the width of the tunnel and spray concrete to fill the over-excavated holes;

[0007] Step 3: Position and install the arch rods one by one along the length direction of the main tunnel, and set connecting steel frames and steel meshes between the arch rods. The rear end of the arch rod is connected to the portal frame or the arch rod bolts of the previous cycle. The front end of the arch rod is anchored to the inner wall of the main tunnel through grouting of the second anchor pipe. The front end of the second anchor pipe is tilted toward the excavation direction of the width of the main tunnel.

[0008] Step 4: Install the third anchor pipe at the rear end of the arch rod and grout it for anchoring. The third anchor pipe is tilted toward the rear end in the digging direction of the positive tunnel width.

[0009] Step 5: Re-spray concrete and repeat steps 2 to 4 until the initial support of the steps on the intersection is completed.

[0010] Furthermore, the angles between the axes of the second anchor pipe and the third anchor pipe and the tangent line of the positive hole contour are both 10° to 30°.

[0011] Furthermore, in step 2, the main tunnel is divided vertically into multiple areas along the width direction, among which the area directly below the arch is divided into the left section and the right section, and the heading face is excavated step by step, and the excavation progress is 0.5m for the excavation span of grade VI surrounding rock, 1m for the excavation span of grade V surrounding rock, 2m for the excavation span of grade IV surrounding rock, and 3m for the excavation span of grade III and below surrounding rock.

[0012] Furthermore, in step 2, before the initial spraying of concrete, the joints between the spliced ​​arch rods and between the arch rods and the portal frames are wrapped with joint protective covers.

[0013] Furthermore, the first anchor pipe is overlapped and double-sidedly welded to the portal frame by means of L-shaped threaded steel bars, and the second anchor pipe and the third anchor pipe are overlapped and double-sidedly welded to the arch rod by means of L-shaped threaded steel bars.

[0014] Furthermore, the water-cement ratio of the grouting slurry of the first anchor pipe, the second anchor pipe and the third anchor pipe is 0.4-0.8, and the grouting pressure is 0.5MPa-1.0Mpa.

[0015] A supporting structure includes an arch frame, which is assembled from a number of arch rods. A first connecting plate and a second connecting plate are welded at both ends of the arch rod. The arch rod is bolted to a door frame or the first connecting plate of a previous cycle arch rod through the second connecting plate. A connecting hole is provided on the first connecting plate for positioning and passing a second anchor pipe.

[0016] Furthermore, the portal frame includes vertical poles, arc rods and longitudinal support beams. The vertical poles are respectively tightly attached to both sides of the branch hole, the arc rods are fitted with the contour of the main hole, one end of the longitudinal support beam is connected to the vertical pole, and the other end of the longitudinal support beam is connected to the arc rod. A supporting beam for supporting the branch hole is arranged between the tops of adjacent longitudinal support beams, and a horizontal support beam for connecting the arch rod is arranged between the ends of adjacent arc rods.

[0017] Preferably, the first anchor tubes are respectively arranged on the upper and lower sides of both ends of the arc rod, the second anchor tubes are respectively arranged on the left and right sides of the front end of the arch rod, and the third anchor tubes are respectively arranged on the left and right sides of the rear end of the arch rod.

[0018] Preferably, the vertical poles, curved poles, longitudinal joists, supporting beams, transverse joists and arch poles are all made of I-beams.

[0019] The present invention has at least the following advantages and beneficial effects:

[0020] (1) The intersection is initially supported by excavating in a zoned cycle and supporting the arch rod in sections. A gantry is installed at the intersection to connect the arch rod of the first cycle, and the arch rod is anchored by a second anchor pipe arranged at an angle toward the front end of the excavation direction of the positive tunnel width and a third anchor pipe arranged at an angle toward the rear end of the excavation direction of the positive tunnel width. This ensures early support after excavation, saves time for advanced support, and makes construction safer. The construction progress of the intersection is accelerated, the construction cost is reduced, the safety of the workers is ensured, and a safe space is provided for the overlapping construction of the next cycle of initial support, so that rapid entry into the tunnel is achieved.

[0021] (2) By assembling the arch frame in sections, one end of the arch rod is connected to the completed portal frame or arch rod, and the other end is locked in the surrounding rock by the first connecting plate and the second anchor pipe. This not only ensures that the arch frame can be smoothly looped in the initial support, but also plays a role in positioning and fixing the subsequent arch rods during the installation process. Both ends of the arch frame can be supported and prevented from falling. This saves the construction time of the intersection and the construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a process flow chart of a tunnel soft surrounding rock cross tunnel intersection support construction method.

[0023] Figure 2 A construction schematic diagram of a support structure provided by the present invention.

[0024] Figure 3 The present invention provides a front view of a portal frame in a supporting structure.

[0025] Figure 4 A side view of a portal frame in a supporting structure provided by the present invention.

[0026] Figure 5 A schematic diagram of the connection of arch rods in a supporting structure provided by the present invention.

[0027] Figure 6 A schematic structural diagram of an arch rod in a supporting structure provided by the present invention.

[0028] Figure markings: 1-branch hole, 2-main hole, 3-door frame, 31-vertical pole, 32-arc rod, 33-longitudinal support beam, 34-support beam, 35-transverse support beam, 36-first anchor pipe, 4-arch frame, 40-arch rod, 41-first connecting plate, 410-connecting hole, 42-second connecting plate, 43-second anchor pipe, 44-third anchor pipe, 5-locking foot anchor pipe. DETAILED DESCRIPTION

[0029] The following is a specific implementation method in conjunction with the accompanying drawings.

[0030] Example

[0031] like Figure 1-6 As shown, in this embodiment, a tunnel soft surrounding rock cross tunnel intersection support construction method is mainly disclosed, which is suitable for the initial support arch frame 4 construction of soft surrounding rock intersections such as tunnel branch tunnel 1 turning into main tunnel 2, inclined shaft turning into main tunnel 2, and cross passage turning into main tunnel 2, including the following steps:

[0032] Step 1: dig a pilot tunnel in the branch tunnel 1 to enter the main tunnel 2, and expand the space for installing the portal frame 3. The portal frame 3 is anchored to the side wall of the intersection of the branch tunnel 1 and the main tunnel 2 through the first anchor pipe 36. Specifically, after the initial support is completed, a small pilot tunnel is excavated in the branch tunnel 1 to enter the main tunnel 2. The branch tunnel 1 serves as an auxiliary working channel, and the excavation direction intersects with the side of the main tunnel 2 to form an intersection. Before installing the portal frame 3, mark the positions of the various components of the portal frame 3, and use mechanical support and arch frame trolley to complete the positioning and assembly of the portal frame 3; use a handheld rock drilling pneumatic drill to install the first anchor pipe 36, and weld the first anchor pipe 36 and the portal frame 3 to form a whole through L-shaped threaded steel, and fix the portal frame 3 through grouting anchoring.

[0033] Step 2: Excavate along the width direction of the main tunnel 2 in a circular manner, and initially spray concrete to fill the over-excavated holes; preferably, the main tunnel 2 is vertically divided into multiple areas along the width direction, among which the area directly below the arch is divided into the left and right sections, and the face is excavated in steps, and the excavation progress is 0.5m for the excavation span of grade VI surrounding rock, 1m for the excavation span of grade V surrounding rock, 2m for the excavation span of grade IV surrounding rock, and 3m for the excavation span of grade III and below surrounding rock. Specifically, Figure 2 As shown, in this embodiment, the main tunnel 2 can be divided into 8 areas from a to h for cyclic excavation, among which areas a and b are the first cycle of excavation from branch tunnel 1 to main tunnel 2, which provide sufficient space for the installation of portal frame 3 after excavation, i.e., the space expanded in the above step 1. The remaining areas provide space for the initial support construction of main tunnel 2 while ensuring excavation safety. It should be noted that when excavating the d area, the footage span is shortened. For example, if the surrounding rock is of grade VI, the rock is soft or in a plastic state, and the compressive strength is extremely low, the excavation span is controlled to 0.5m; if the surrounding rock is of grade V, there are multiple cracks in the rock mass, the joints and cracks are extremely developed, the strength is extremely low, the stability is poor, and the compressive strength is usually less than 15MPa, and the excavation span is controlled to 1m; if the surrounding rock is of grade IV, the rock mass is broken, the rock is relatively soft, the joints and cracks are developed, the strength is low, the stability is poor, and the compressive strength is generally between 15-20MPa, and the excavation span is controlled to 2m. If the surrounding rock is of grade III or below, the excavation span is 3m. In addition, the excavation of the d area adopts the form of left and right excavation in steps, which effectively avoids the instability of the surrounding rock, reduces the risk of tunnel collapse and deformation, and improves the safety of construction. At the same time, during the excavation process, the cross-section dangerous rocks are removed and the contours are repaired. Then, the initial concrete spraying is carried out on the arch top of the main tunnel 2 to fill the over-excavated holes, and the amount of spraying is controlled so that the spraying layer thickness is 3cm.

[0034] Step 3: Position and install the arch rods 40 one by one along the length direction of the main tunnel 2, and set connecting steel frames and steel meshes between the arch rods 40. The rear end of the arch rod 40 is bolted to the portal frame 3 or the arch rod 40 of the previous cycle, and the front end of the arch rod 40 is grout-anchored to the inner wall of the main tunnel 2 through the second anchor pipe 43. The second anchor pipe 43 is tilted toward the front end of the excavation direction of the width of the main tunnel 2. Specifically, the arch rod 40 of the first cycle is supported by the portal frame 3, and the position is measured and marked on the portal frame 3, and the steel plate is welded to install the arch rod 40. The arch rods 40 of the subsequent cycles are installed one by one according to the position of the arch rod 40 of the previous cycle. The second anchor pipe 43 adopts a Φ42×4mm steel pipe with a length of 4.5m. It is tilted and installed in front of the excavation, and the second anchor pipe 43 and the arch rod 40 are welded to form a whole through L-shaped threaded steel, and the arch rod 40 is fixed by grouting anchoring. The grout is injected into the front surrounding rock through the second anchor pipe 43 to improve the surrounding rock, which plays an advanced role and saves the time of advanced support construction, making the construction safer.

[0035] Step 4: Install the third anchor pipe 44 at the rear end of the arch rod 40 and anchor it by grouting. The third anchor pipe 44 is arranged inclined toward the rear end in the excavation direction of the width of the main tunnel 2; specifically, the third anchor pipe 44 adopts a Φ42×4mm steel pipe with a length of 3.0m. After the third anchor pipe 44 is installed, the third anchor pipe 44 and the arch rod 40 are welded to form a whole through L-shaped threaded steel. The third anchor pipe 44 and the second anchor pipe 43 are inclined in opposite directions, which effectively improves the stability of the anchoring of the arch rod 40.

[0036] Step 5, re-spray concrete, repeat steps 2 to 4 until the initial support of the steps on the intersection is completed. It should be noted that before re-spraying concrete, it is necessary to refer to the original design drawings, add locking foot anchor pipes 5 at the corresponding positions, and perform welding and grouting anchoring to completely lock the formed initial support. Then, use a wet spraying trolley to re-spray concrete on the arch of tunnel 2 to complete the partition support construction, and then repeat steps 2 to 4, and continue to advance by partition until the initial support of the steps on the intersection is completed. In addition, the construction joints at each partition of the initial support need to be re-sprayed in time.

[0037] This method does not need to expand the original design section of the main tunnel 2, but only uses the original design of the initial support section for partial excavation. Compared with the traditional intersection top construction method, it reduces the input of materials and labor, and uses the self-stabilizing ability of the surrounding rock to ensure construction safety. It speeds up the construction progress of the intersection, reduces construction costs, ensures the safety of workers, provides a safe space for the overlap construction of the next cycle of initial support, and realizes rapid entry into the hole.

[0038] Furthermore, the included angles between the axes of the second anchor pipe 43 and the third anchor pipe 44 and the tangent line of the outline of the main tunnel 2 are both 10° to 30°, so that the second anchor pipe 43 and the third anchor pipe 44 are initially embedded in the surrounding rock without damaging the surrounding rock.

[0039] Furthermore, in step 2, before the initial spraying of concrete, the joints between the spliced ​​arch rods 40 and between the arch rods 40 and the door frame 3 are wrapped with joint protection sleeves.

[0040] Furthermore, the first anchor pipe 36 is overlapped and double-sided welded with the portal frame 3 through L-shaped threaded steel bars, and the second anchor pipe 43 and the third anchor pipe 44 are overlapped and double-sided welded with the arch rod 40 through L-shaped threaded steel bars. During the specific construction, it is difficult to keep the surfaces of the first anchor pipe 36 and the arch rod 32, the second anchor pipe 43 and the third anchor pipe 44 and the arch rod 40 completely perpendicular, which makes it difficult for the pre-processed L-shaped threaded steel bars to fit the connection surfaces at the same time. The bending angle of the L-shaped threaded steel bars is adjusted according to the angle of the connection surface on site to ensure that the connection surfaces are closely attached to avoid wide gap welding.

[0041] Furthermore, the water-cement ratio of the grouting slurry of the first anchor pipe 36, the second anchor pipe 43 and the third anchor pipe 44 is 0.4-0.8, and the grouting pressure is 0.5MPa-1.0Mpa. Specifically, the cement slurry adopts early-strength single-liquid cement slurry. It should be noted that the grouting is first thin and then thick, and the grouting pressure of each hole reaches 1.0MPa, and it is kept for more than 10 minutes before stopping the grouting. Considering that the grouting of weak surrounding rock is prone to excessive slurry consumption, it deteriorates the engineering properties of the surrounding rock. If the on-site thin slurry grouting volume is greater than the single designed grouting volume, the grouting water-cement ratio is changed to 0.4, and the grouting is continued according to the quality control requirements. The first grouting slurry of the adjacent hole is changed to thick slurry.

[0042] like Figure 2-6As shown, in this embodiment, a support structure is also disclosed, including an arch frame 4, which is assembled from a plurality of arch rods 40, with a first connecting plate 41 and a second connecting plate 42 welded at both ends of the arch rod 40, the arch rod 40 is bolted to the door frame 3 or the first connecting plate 41 of the previous cycle arch rod 40 through the second connecting plate 42, and a connecting hole 410 for positioning and penetrating the second anchor pipe 43 is provided on the first connecting plate 41. Specifically, in this embodiment, the first connecting plate 41 is a steel plate of 460mm×200mm×16mm, and the second connecting plate 42 is a steel plate of 260mm×200mm×16mm. The first connecting plate 41 is arranged at one end of the arch rod 40 away from the branch hole 1, and the second connecting plate 42 is arranged at one end of the arch rod 40 close to the branch hole 1, and bolt holes for butt-jointing and penetrating bolts are provided at corresponding positions on the first connecting plate 41 and the second connecting plate 42. The connecting hole 410 can be a strip hole, and its opening position should avoid overlapping interference with the second connecting plate 42 when the arch rod 40 is spliced, so as to ensure the smooth installation of the second anchor rod, provide a suitable construction angle and limit method, make the construction more convenient, and achieve a better locking effect. It should be noted that there is a misalignment between the installation position of the second anchor pipe 43 at the front end of the arch rod 40 and the installation position of the third anchor pipe 44 at the rear end of the next cycle arch rod 40 along the width direction of the arch rod 40. By assembling the arch frame 4 in sections, early support after excavation is ensured, while reducing the loss of additional materials and saving construction time. Compared with the scaffolding method, there is no need to remove unnecessary columns, trim the initial surface, install the main tunnel 2 arch frame 4 and other construction steps, which greatly saves the construction time of the intersection and saves construction time.

[0043] Further, the door frame 3 includes a vertical rod 31, an arc rod 32 and a longitudinal support beam 33. The vertical rod 31 is respectively closely attached to both sides of the branch hole 1, the arc rod 32 is in contact with the contour of the main hole 2, one end of the longitudinal support beam 33 is connected to the vertical rod 31, and the other end of the longitudinal support beam 33 is connected to the arc rod 32. A support beam 34 for supporting the branch hole 1 is arranged between the tops of adjacent longitudinal support beams 33, and a transverse support beam 35 for connecting the arch rod 40 is arranged between the ends of adjacent arc rods 32. Preferably, the first anchor pipe 36 is respectively arranged on the upper and lower sides of both ends of the arc rod 32, the second anchor pipe 43 is respectively arranged on the left and right sides of the front end of the arch rod 40, and the third anchor pipe 44 is respectively arranged on the left and right sides of the rear end of the arch rod 40.

[0044] Preferably, the vertical pole 31, the arc rod 32, the longitudinal support beam 33, the support beam 34, the cross support beam 35 and the arch rod 40 are all made of I-beam. Specifically, the vertical pole 31, the longitudinal support beam 33, the support beam 34 and the cross support beam 35 are all cut and formed according to the designed length. The arc rod 32 has its length and rise determined according to the designed angle and radius, and is processed and formed by the arch frame bending machine. The angle, radius, length and rise of the arch rod 40 are determined by dividing the arch rod 40 according to the partition excavation design drawing in the above step 2.

Claims

1. A tunnel soft surrounding rock cross tunnel intersection support construction method, characterized in that: The following steps are involved: Step 1: installing the portal frame (3), excavating a pilot tunnel in the branch tunnel (1) to enter the main tunnel (2), and expanding the excavation to create a space for installing the portal frame (3), and the portal frame (3) is grout-anchored to the side wall of the intersection of the branch tunnel (1) and the main tunnel (2) through a first anchor pipe (36); Step 2: Excavate the cross section in sections, excavate in sections in a circular manner along the width direction of the main tunnel (2), and initially spray concrete to fill the over-excavated holes; Step 3, installing the partitioned arch rods (40), positioning and installing the arch rods (40) one by one along the length direction of the main tunnel (2), and arranging connecting steel frames and steel meshes between the arch rods (40), the rear end of the arch rod (40) being bolted to the door frame (3) or the arch rod (40) of the previous cycle, the front end of the arch rod (40) being grout-anchored to the inner wall of the main tunnel (2) through a second anchor pipe (43), and the front end of the second anchor pipe (43) being inclined toward the excavation direction of the width of the main tunnel (2); Step 4: anchoring the rear end of the arch rod (40), installing a third anchor pipe (44) at the rear end of the arch rod (40), and anchoring it by grouting, wherein the third anchor pipe (44) is arranged obliquely toward the rear end in the excavation direction of the width of the main tunnel (2); Step 5: Re-spray concrete and repeat steps 2 to 4 until the initial support of the upper steps of the intersection is completed.

2. A tunnel soft surrounding rock cross tunnel intersection support construction method according to claim 1, characterized in that: The included angles between the axes of the second anchor pipe (43) and the third anchor pipe (44) and the tangent line of the outline of the main hole (2) are both 10° to 30°.

3. A tunnel soft surrounding rock cross tunnel intersection support construction method according to claim 1, characterized in that: In the step 2, the main tunnel (2) is vertically divided into a plurality of areas along the width direction, wherein the area directly below the arch is divided into a left section and a right section, and the heading face is excavated in steps, and the excavation progress is 0.5 m for the excavation span of grade VI surrounding rock, 1 m for the excavation span of grade V surrounding rock, 2 m for the excavation span of grade IV surrounding rock, and 3 m for the excavation span of grade III and below surrounding rock.

4. The construction method for supporting the intersection of a tunnel with soft surrounding rock according to claim 1 is characterized in that: In the step 2, before the initial spraying of concrete, the joints between the spliced ​​arch rods (40) and between the arch rods (40) and the door frame (3) are wrapped with joint protection sleeves.

5. According to the construction method for supporting intersections of soft surrounding rock cross tunnels in a tunnel as described in claim 1, the first anchor pipe (36) is overlapped and double-sidedly welded to the portal frame (3) through L-shaped threaded steel, and the second anchor pipe (43) and the third anchor pipe (44) are overlapped and double-sidedly welded to the arch rod (40) through L-shaped threaded steel.

6. The construction method for supporting the intersection of a tunnel with soft surrounding rock according to claim 1 is characterized in that: The water-cement ratio of the grouting slurry of the first anchor pipe (36), the second anchor pipe (43) and the third anchor pipe (44) is 0.4-0.8, and the grouting pressure is 0.5MPa-1.0MPa.

7. A support structure for a tunnel soft surrounding rock cross tunnel intersection support construction method according to any one of claims 1 to 6, characterized in that: The invention comprises an arch frame (4), wherein the arch frame (4) is assembled from a plurality of arch rods (40), wherein a first connecting plate (41) and a second connecting plate (42) are respectively welded at both ends of the arch rod (40), and the arch rod (40) is bolted to the door frame (3) or the first connecting plate (41) of the previous cycle of the arch rod (40) via the second connecting plate (42), and a connecting hole (410) for positioning and penetrating the second anchor pipe (43) is provided on the first connecting plate (41).

8. The supporting structure according to claim 7, characterized in that: The door frame (3) comprises a vertical rod (31), an arc rod (32) and a longitudinal support beam (33); the vertical rod (31) is respectively closely attached to both sides of the branch hole (1); the arc rod (32) is in conformity with the contour of the main hole (2); one end of the longitudinal support beam (33) is connected to the vertical rod (31); the other end of the longitudinal support beam (33) is connected to the arc rod (32); a support beam (34) for supporting the branch hole (1) is arranged between the tops of adjacent longitudinal support beams (33); and a transverse support beam (35) for connecting the arch rod (40) is arranged between the ends of adjacent arc rods (32).

9. The supporting structure according to claim 8, characterized in that: The first anchor tube (36) is respectively arranged on the upper and lower sides of both ends of the arc rod (32), the second anchor tube (43) is respectively arranged on the left and right sides of the front end of the arch rod (40), and the third anchor tube (44) is respectively arranged on the left and right sides of the rear end of the arch rod (40).

10. The supporting structure according to claim 8, characterized in that: The vertical rod (31), the arc rod (32), the longitudinal support beam (33), the supporting beam (34), the transverse support beam (35) and the arch rod (40) are all made of I-beams.

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