A construction method for excavating into a tunnel in the dark on the secondary lining structure of an existing urban tunnel

Abstract

The present invention discloses a construction method for excavating into a tunnel in a concealed manner on the secondary lining structure of an existing tunnel in a city. The steps include: constructing temporary steel column supports for the existing tunnel structure at the designed tunnel intersection; excavating the pilot tunnel of the newly built tunnel and constructing temporary support; reverse excavation of the newly built tunnel, excavation of the standard section of the newly built tunnel and construction of the initial support; constructing the portal frame structure conversion system at the tunnel intersection; removing the temporary support of the existing tunnel structure; during the construction process, continuously monitoring the deformation of the secondary lining structure of the existing tunnel. The beneficial effects of the present invention are as follows: This construction method provides safety guarantee for the excavation construction process through temporary steel supports and advanced large-diameter pipe roofs, reduces the damage degree to the existing tunnel structure through the pilot tunnel and the portal frame structure, reduces the disturbance to it, strengthens the bearing capacity and stress conversion between structures, ensures the safety of the secondary lining structure of the existing tunnel, and improves the anti-leakage ability between the new and old structures through the waterproof and drainage strengthening system.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel construction, and particularly relates to a construction method for excavating a tunnel into an existing tunnel's secondary lining structure in a city. Background Technique

[0002] During the construction of a new tunnel project for a general highway or railway, when directly opening a hole into the mountain or rock surface, the stress condition of the surrounding rock is simple, and the stability is relatively easy to control. Different from new tunnels, in many urban underground projects, there are situations where new and old structures are demolished, combined, and form an intersection tunnel group with mutually intersecting interfaces. When opening a new hole on an existing tunnel structure, if conventional excavation and tunneling measures or methods are used, the damage range to the existing tunnel structure is relatively large, and the resulting safety disturbance is also large, and the safety of the existing tunnel structure cannot be guaranteed. In addition, the ineffective closure of the tunnel entrance for a long time during the construction process, the difficulty in combining new and old structures, and the large waterproofing influence range are all adverse factors faced when using ordinary tunneling methods. Patent document CN112431606A discloses a construction method for a large-section T-shaped intersection tunnel group, which controls the construction safety of a large-section tunnel entering a small-section tunnel through a construction method and also involves the force transfer problem of a transition support structure. However, this is a synchronous construction method for a tunnel group and does not involve the safety problem of the secondary lining structure of an existing tunnel. Therefore, there is an urgent need for a construction method for excavating a tunnel into an existing tunnel's secondary lining structure to solve the technical challenges faced by using ordinary tunneling methods. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a construction method for excavating a tunnel into an existing tunnel's secondary lining structure in a city to ensure the safety of the existing tunnel's secondary lining structure and construction safety, ensure the force transfer, bearing capacity, and effective combination between the new and old sections, and the anti-seepage ability between the new and old structures.

[0004] The technical solution is as follows:

[0005] A construction method for excavating a tunnel into an existing tunnel's secondary lining structure in a city, which is characterized by being carried out according to the following steps:

[0006] Step S1, construct temporary steel column support for the existing tunnel structure at the designed tunnel intersection;

[0007] Step S2, carry out excavation and temporary support construction for the pilot tunnel of the new tunnel;

[0008] Step S3, carry out reverse excavation of the new tunnel, excavation of the standard section of the new tunnel, and primary support construction;

[0009] Step S4, carry out construction of the portal frame structure conversion system at the tunnel intersection;

[0010] Step S5, the temporary support of the existing tunnel structure is removed;

[0011] During the processes of steps S2 - S5, continuously monitor the deformation of the secondary lining structure of the existing tunnel.

[0012] In an implementation manner, in the above step S1, the temporary steel column support includes steel columns and steel connecting beams. The steel columns are erected inside the existing tunnel. The steel columns are respectively arranged on both sides of the entrance of the designed new tunnel. The steel connecting beams are connected between the steel columns, and the steel connecting beams support the secondary lining structure of the existing tunnel.

[0013] In an implementation manner, the above step S2 includes:

[0014] Step S21, construction of the advanced large - diameter pipe shed in the pilot adit;

[0015] Step S22, excavate the pilot adit and erect temporary support according to the advancing direction of the new tunnel.

[0016] In an implementation manner, the step S21 is specifically:

[0017] Outside the excavation contour line of the pilot adit, construct an advanced large - diameter pipe shed. The length of the shed pipe of the advanced large - diameter pipe shed is 10m, the circumferential spacing is 0.4m, and the inclination angle is 1 - 2°.

[0018] In an implementation manner, each shed pipe is composed of two pipe segments with a length difference of more than 1m connected together, and the joints of adjacent shed pipes are staggered from each other.

[0019] In an implementation manner, during the construction process of the above step S3, back - excavate to the back of the side - wall structure of the existing tunnel. During the back - excavation process, gradually remove the temporary support of the pilot adit, and at the same time, construct the primary support of the main tunnel of the new tunnel.

[0020] In an implementation manner, the above step S4 includes:

[0021] S41, excavate the foundation trench of the portal frame structure, effectively connect the steel skeleton and waterproof layer peeled off from the portal frame structure and the secondary lining structure of the existing tunnel, and conduct construction joint treatment;

[0022] S42, embed grouting pipes, and reserve embedded pipes at the cross - beam position of the portal frame structure. First, pour the columns of the portal frame structure, and then pour the cross - beam.

[0023] In one embodiment, the specific process of step S41 is as follows: manually excavate the foundation trench of the portal frame structure, lay the steel skeleton of the portal frame structure in the foundation trench and weld it to the steel bars peeled off from the secondary lining structure of the existing tunnel. The waterproof layer of the portal frame structure is effectively welded to the waterproof layer peeled off from the secondary lining structure of the existing tunnel, and a drainage blind pipe is installed for drainage. After the joint concrete surface is cleaned and roughened, a water swelling water stop strip is installed, and the cross section is coated with a cementitious capillary crystalline coating.

[0024] In one embodiment, after the portal frame structure and the first formwork secondary lining concrete of the new tunnel reach the design strength, step S5 is carried out, and the temporary support is manually removed.

[0025] In one embodiment, the above-mentioned steel connecting beam includes at least two cross beams arranged in parallel along the direction of the existing tunnel. A triangular frame is supported above the cross beams. A group of jacks are erected on the inclined sides of the triangular frame. The jacks on the same triangular frame are distributed along the inclined side of the triangular frame. The jacks extend towards the arch crown of the existing tunnel. The extending ends of all the jacks support the same bendable fitting plate. The jacks are telescopically connected to the triangular frame and press the bendable fitting plate to make it fit the arch crown of the existing tunnel.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This construction method provides safety guarantee for the excavation construction process through temporary steel supports and advanced large pipe roofs, reduces the degree of damage to the existing tunnel structure through the pilot tunnel and the portal frame structure, reduces the disturbance to it, strengthens the bearing capacity and stress conversion between structures, ensures the safety of the secondary lining structure of the existing tunnel, and improves the anti-seepage ability between the new and old structures through the construction method of the anti-seepage and drainage strengthening system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the plan view of the adit excavation on the secondary lining structure of the existing tunnel;

[0028] Figure 2 It is the front view of the adit excavation tunnel on the secondary lining structure of the existing tunnel;

[0029] Figure 3 It is the side view of the adit excavation tunnel on the secondary lining structure of the existing tunnel;

[0030] Figure 4 It is the structural schematic diagram of the temporary support of the steel column;

[0031] Figure 5 For Figure 4 The enlarged view of part m in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described below in conjunction with the embodiments and the drawings.

[0033] As Figures 1 to 3 shown, a construction method for excavating into a tunnel in a concealed manner on the secondary lining structure of an existing tunnel in a city is carried out according to the following steps:

[0034] Step S1, carry out the construction of temporary support 1 of the steel column on the existing tunnel structure at the designed tunnel intersection;

[0035] Step S2, carry out the excavation of the pilot tunnel of the new tunnel and the construction of temporary support;

[0036] Step S3, carry out the reverse excavation of the new tunnel, the excavation of the standard section of the new tunnel and the construction of initial support;

[0037] Step S4, carry out the construction of the gantry frame structure conversion system at the tunnel intersection;

[0038] Step S5, remove the said temporary support of the existing tunnel structure;

[0039] During the process of steps S2 to S5, continuously monitor the deformation of the secondary lining structure of the existing tunnel.

[0040] Before step S2 starts, arrange monitoring deformation observation points above the excavation contour line of the designed pilot tunnel 2, and continuously monitor the deformation of the secondary lining structure of the existing tunnel during the subsequent construction process. Then carry out step S2:

[0041] Step S21, carry out the construction of the advanced large-diameter pipe shed 5 of the pilot tunnel 2. The construction method is: outside the excavation contour line of the pilot tunnel 2, construct the advanced large-diameter pipe shed 5. The pipe length of the advanced large-diameter pipe shed 5 is 10m, the circumferential distance is 0.4m, and the inclination angle is 1 - 2°;

[0042] Step S22, carry out the excavation of the pilot tunnel 2 and the erection of temporary support in the advancing direction of the new tunnel. The lock foot bolts need to be constructed at the arch feet and the nodes of the springing line of each segment of the temporary support arch of the pilot tunnel 2.

[0043] When demolishing the concrete structure of the existing tunnel, manual demolition is adopted to reduce the disturbance to the structure.

[0044] For the situation where the construction space is limited, for the convenience of construction, each said pipe shed is connected by two pipe segments with a length difference of more than 1m, and the joints of adjacent two said pipe sheds are staggered from each other. For example, the pipe shed is formed by arranging two pipe segments with lengths of 4m and 6m in sections, and the size is The pre-grouting of the pipe shed adopts M30 cement slurry to provide safety guarantee during the excavation construction process.

[0045] The excavation of the pilot tunnel 2 should minimize the disturbance to the structure, ensure short footage, excavate and support one by one, and the temporary support adopts the form of steel arch frame combined with shotcrete with wire mesh to ensure the structural safety.

[0046] During the construction process of step S3, the excavation is carried out in the reverse direction to the back of the side wall structure of the existing tunnel. During the excavation process, the temporary support of the advanced pilot tunnel is gradually removed, and at the same time, the initial support of the main tunnel of the new tunnel is constructed, also in the form of a steel arch frame combined with anchor mesh shotcrete to ensure structural safety. On this basis, the foundation trench of the portal frame structure is excavated.

[0047] Step S4 specifically includes:

[0048] S41, excavate the foundation trench of the portal frame structure, effectively connect the steel skeleton and waterproof layer peeled off from the secondary lining structure of the existing tunnel with the portal frame structure, and carry out construction joint treatment;

[0049] Specifically, the foundation trench of the portal frame structure is excavated manually, the steel skeleton of the portal frame structure is arranged in the foundation trench and welded to the steel bars peeled off from the secondary lining structure of the existing tunnel. The waterproof layer of the portal frame structure is effectively welded to the waterproof layer peeled off from the secondary lining structure of the existing tunnel, and drainage blind pipes are installed for drainage. After the joint concrete surface is cleaned and roughened, water-swelling waterstop strips are installed, and the cross-section is coated with cementitious capillary crystalline coating;

[0050] S42, pre-embed Φ32 grouting pipes 6, and reserve pre-embedded pipes 7 at the position of the cross beam 3 of the portal frame structure. First, pour the columns 4 of the portal frame structure, and then pour the cross beam 3.

[0051] Then, the secondary lining construction of the new tunnel is carried out. After the portal frame structure and the first formwork of the secondary lining concrete of the new tunnel reach the design strength, step S5 is carried out, and the temporary support is removed manually in an orderly manner. Finally, the new tunnel is constructed normally.

[0052] A steel column temporary support 1 includes steel columns 110 and steel connection beams 120. The steel columns 110 are erected in the existing tunnel. The steel columns 110 are respectively arranged on both sides of the entrance of the designed new tunnel. The steel connection beams 120 are connected between the steel columns 110, and the steel connection beams 120 support the secondary lining structure of the existing tunnel.

[0053] The steel column 110 can adopt t = 16mm hot-rolled seamless steel pipe. The steel connection beam 120 is a triangular wedge welded with double I16 steel sections and steel plates. Stiffeners are set at the joints. The top should be closely attached to the concrete surface of the arch structure of the existing tunnel. After applying prestress, the base of the steel column 110 is poured with C20 concrete for fixation. This ensures the structural safety of the existing tunnel.

[0054] To improve the support effect, such as Figure 4, a steel connection beam 120 includes at least two cross beams 121 arranged in parallel along the direction of the existing tunnel. A triangular frame 122 is supported above the cross beam 121. A group of ejector rods 123 are vertically arranged on the hypotenuse of the triangular frame 122. The ejector rods 123 on the same triangular frame 122 are distributed along the hypotenuse of the triangular frame 122. The ejector rods 123 extend towards the crown of the existing tunnel. The extending ends of all the ejector rods 123 support the same bendable fitting plate 130. The ejector rods 123 are telescopically connected to the triangular frame 122 and press the bendable fitting plate 130 to make it fit the crown of the existing tunnel. This can make the supporting force distribution of the steel column temporary support 1 on the crown of the existing tunnel more uniform and reduce the stress concentration.

[0055] Such as Figure 5 , the bendable fitting plate 130 includes a rubber plate 131, and a reinforcing iron plate 133 is wrapped inside the rubber plate 131. The rubber plate 131 abuts against the crown of the existing tunnel. A group of anti-slip grooves 132 are formed on the side of the rubber plate 131 facing away from the crown of the existing tunnel. The anti-slip grooves 132 extend along the direction parallel to the axial direction of the existing tunnel. All the anti-slip grooves 132 are evenly arranged transversely along the crown of the existing tunnel. A purlin 124 is fixedly arranged at the extending end of the ejector rod 123. The surface of the purlin 124 facing the bendable fitting plate 130 is an arc-shaped pressing surface adapted to the anti-slip grooves 132.

[0056] Specifically, a group of parallel convex strips are integrally formed on the side of the reinforcing iron plate 133 facing the anti-slip grooves 132. After the reinforcing iron plate 133 is wrapped inside the rubber plate 131, the surface of the rubber plate 131 between two adjacent convex strips forms the anti-slip grooves 132. The reinforcing iron plate 133 not only increases the rigidity and strength of the rubber plate 131, but also helps to disperse the pressing force of the purlin 124.

[0057] The triangular frame 122 can be made of section steel. Its hypotenuse can be made of I-beam or T-beam. Connecting holes are processed on the wall of the hypotenuse of the triangular frame 122 facing the end plate. The two acute angles of the triangular frame 122 respectively press the edge of the bendable fitting plate 130 close to the crown of the existing tunnel and the edge close to the side wall of the existing tunnel.

[0058] The ejector rod 123 is connected to the triangular frame 122 through an end plate. Two rows of connecting holes are distributed along the length direction of the hypotenuse of the triangular frame 122.

[0059] At least two oblong holes are formed in the end plate, and the length direction of the oblong holes is parallel to the hypotenuse of the triangular bracket 122. The end plate and the triangular bracket 122 are fixed through the oblong holes and the connecting holes. The row of connecting holes allows the position of the ejector rod 123 on the hypotenuse of the triangular bracket 122 to be set as required, while the oblong holes allow for fine adjustment of the position, so as to facilitate fixing the ejector rod 123 at an appropriate position, and enabling the purlin 124 at the extending end of the ejector rod 123 to be pressed against the anti-slip groove 132 at the corresponding position.

[0060] The ejector rod 123 can use a turnbuckle, which is composed of a threaded steel pipe and two threaded steel bars with opposite thread directions connected to both ends thereof, to achieve telescopic adjustment. The outer ends of the two threaded steel bars are respectively welded to the purlin 124 and the end plate.

[0061] In step S1, the steel column 110 is erected, the cross beam 121 is installed to connect the steel columns 110, then the triangular bracket 122 and the ejector rod 123 are installed, the rubber plate 131 is preliminarily fixed, and then the ejector rod 123 is adjusted to extend and press tightly against the bendable fitting plate 130.

[0062] Finally, it should be noted that the above description is only the preferred embodiment of the present invention. Under the inspiration of the present invention, those of ordinary skill in the art can make various similar representations without departing from the purpose and claims of the present invention, and such transformations all fall within the protection scope of the present invention.

Claims

1. A construction method for secretly excavating and entering a tunnel in the secondary lining structure of an existing urban tunnel, characterized in that The following steps are carried out: Step S1, construct the temporary steel column support (1) for the existing tunnel structure at the designed tunnel intersection; Step S2, carry out the excavation and temporary support construction of the pilot heading (2) of the new tunnel; Step S3, carry out the reverse excavation of the new tunnel, the excavation of the standard section of the new tunnel and the initial support construction; Step S4, carry out the construction of the gantry frame structure conversion system at the tunnel intersection; Step S5, remove the temporary steel column support of the existing tunnel structure; During the process of steps S2 to S5, continuously monitor the deformation of the secondary lining structure of the existing tunnel; The said step S4 includes: S41, excavate the foundation trench of the gantry frame structure, effectively connect the steel skeleton and waterproof layer peeled off from the existing tunnel secondary lining structure, and carry out construction joint treatment; S42, pre-bury the grouting pipe (6), and reserve the pre-buried pipeline (7) at the position of the cross beam (3) of the gantry frame structure. First, pour the columns (4) of the gantry frame structure, and then pour the cross beam (3).

2. The construction method for secretly excavating and entering a tunnel on the secondary lining structure of an existing urban tunnel according to claim 1, characterized in that: In the said step S1, the temporary steel column support (1) includes steel columns (110) and steel connection beams (120). The steel columns (110) are erected in the existing tunnel. The steel columns (110) are respectively arranged on both sides of the entrance of the designed new tunnel. The steel connection beams (120) are connected between the steel columns (110), and the steel connection beams (120) support the secondary lining structure of the existing tunnel.

3. The construction method for secretly excavating and entering a tunnel on the secondary lining structure of an existing urban tunnel according to claim 1, characterized in that The said step S2 includes: Step S21, construct the advanced large-diameter pipe shed (5) of the pilot heading (2); Step S22, carry out the excavation and erection of temporary support of the pilot heading (2) in the advancing direction of the new tunnel.

4. A construction method for secretly excavating and entering a tunnel on the secondary lining structure of an existing urban tunnel according to claim 3, characterized in that The said step S21 is specifically: Outside the excavation contour line of the pilot heading (2), construct the advanced large-diameter pipe shed (5). The length of the shed pipe of the advanced large-diameter pipe shed (5) is 10m, the circumferential distance is 0.4m, and the inclination angle is 1-2°.

5. A construction method for secretly excavating and entering a tunnel on the secondary lining structure of an existing urban tunnel according to claim 4, characterized in that: Each shed pipe is composed of two pipe sections with a length difference of more than 1m, and the joints of adjacent shed pipes are staggered from each other.

6. The construction method for mining into a tunnel in an existing secondary lining structure of a city tunnel according to claim 1, characterized in that: During the construction process of the said step S3, reverse excavate to the back of the side wall structure of the existing tunnel. During the excavation process, gradually remove the temporary support of the pilot heading, and at the same time construct the initial support of the main tunnel of the new tunnel.

7. A construction method for excavating into a tunnel in the existing second lining structure of a city tunnel in a concealed manner according to claim 1, characterized in that The specific process of the said step S41 is: manually excavate the foundation trench of the gantry frame structure, lay the steel skeleton of the gantry frame structure in the foundation trench and weld it with the steel bars peeled off from the existing tunnel secondary lining structure. The waterproof layer of the gantry frame structure is effectively welded with the waterproof layer peeled off from the existing tunnel secondary lining structure, and drainage blind pipes are installed for drainage. After the joint concrete surface is washed and roughened, water-swelling waterstop strips are installed, and the cross section is coated with cementitious capillary crystalline coating.

8. A construction method for mining into a tunnel in the existing second lining structure of an urban tunnel, characterized in that: After the gantry frame structure and the first lining concrete of the new tunnel reach the designed strength, then carry out the said step S5, and manually remove the temporary steel column support.

9. A construction method for secretly excavating and entering a tunnel on the secondary lining structure of an existing urban tunnel according to claim 2, characterized in that: The steel connection beam (120) includes at least two cross beams (121) arranged in parallel along the direction of the existing tunnel. A triangular frame (122) is supported above the cross beam (121). A set of jacking rods (123) are vertically arranged on the hypotenuse of the triangular frame (122). The jacking rods (123) on the same triangular frame (122) are distributed along the hypotenuse of the triangular frame (122). The jacking rods (123) extend towards the vault of the existing tunnel. The extending ends of all the jacking rods (123) support the same bendable fitting plate (130). The jacking rods (123) are telescopically connected to the triangular frame (122) and jack up the bendable fitting plate (130) to make it fit the vault of the existing tunnel.

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