A construction method for ultra-shallow buried tunnels in backfill areas

Abstract

The present invention specifically discloses a construction method for ultra-shallow buried tunnels in backfill areas, which adopts a detachable temporary support structure to effectively connect with an existing formed initial support arch frame; the method comprises the following steps: S1, processing the initial support arch frame and the detachable temporary support structure as semi-finished products outside the tunnel; S2, excavating the tunnel upper step heading face according to the design excavation footage requirements, and completing the expansion of the upper step arch foot; S3, constructing the initial support arch frame, and completing the installation of the I-beam unit of the expanded arch foot; S4, installing the top I-beam unit; S5, installing the waist I-beam unit; S6, connecting two adjacent steel arch frames; S7, dismantling the detachable temporary support structure, laying a waterproof layer, and constructing an inverted arch. The present invention can reduce material waste, save construction resources, reduce construction costs and improve construction efficiency; and can also ensure construction safety.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a construction method for an ultra-shallow buried tunnel in a backfill area. Background Art

[0002] There are more and more tunnel constructions. In the existing technology, the New Austrian Tunneling Method is generally used in tunnel construction, that is, the bearing capacity of the surrounding rock is utilized. After excavation in the weak surrounding rock, a steel frame (also called a steel arch frame or arch frame) is constructed for support. Anchors, nets, and shotcrete flexible initial supports are used to limit the deformation of the surrounding rock, that is, the initial support structure of the tunnel. These initial support structures are subjected to force and deform together with the surrounding rock. After the deformation of the surrounding rock converges, the secondary lining is constructed to cooperate with the initial support to bear force together. In ultra-shallow tunnels with poor strata, unstable rock mass and strict ground settlement requirements such as backfill areas, the center partition wall method (CD method) or the cross center partition wall method (CRD method) is usually used. The center partition wall method (CD method) is a construction method in which one side of the tunnel is excavated first, and a temporary center partition wall is built in the middle of the design, and then the other side is excavated. The cross center partition wall method (CRD method) is a construction method in which a temporary invert is added on the basis of the center partition wall method (CD method); among them, after the arch crown settlement and convergence of the initial support structure are basically stable, the temporary center partition wall and temporary invert in the initial support structure are removed from top to bottom. Traditional temporary support usually adopts the method of I-beam / grid steel frame + steel mesh + shotcrete. The advantage of this method is that the construction is relatively simple, it can be effectively connected with the primary support of the tunnel to form a closed ring, the technology is relatively mature, and it is widely used; however, this method also has great disadvantages. The first is the waste of materials and high cost, because the steel arch frame and the steel mesh are made into a whole by shotcrete. After the entire section of the tunnel is excavated, the temporary support needs to be removed. In this way, it is difficult to recycle the steel arch frame and steel mesh wrapped in concrete, which results in a large amount of steel and concrete waste and an increase in the project cost; secondly, for small-section tunnels, especially when the tunnel is a shallow buried tunnel in the backfill area and mechanical excavation is used, due to the small cross-section size, after the temporary middle partition wall and temporary invert are set, large-scale machinery and equipment cannot enter the site for construction, which restricts the construction efficiency, and ultimately increases the cost investment and affects the construction period.

[0003] To this end, by improving the construction process, a detachable trapezoidal support frame is used as a temporary support to replace the temporary middle partition and temporary inverted arch. When the inverted arch is constructed, the trapezoidal support frame is dismantled and recycled, and the arch foot of the upper step is enlarged. Based on this, the purpose of reducing material waste, saving construction resources, reducing construction costs and improving construction efficiency can be achieved while ensuring construction safety. Summary of the invention

[0004] The object of the present invention is to provide a construction method for an ultra-shallow buried tunnel in a backfill area, so as to solve the problems of waste of tunnel construction materials and high construction cost.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A construction method for an ultra-shallow buried tunnel in a backfill area, the construction method utilizing an existing formed initial support arch frame of the tunnel, and using a detachable temporary support structure to effectively connect the existing initial support arch frame; the detachable temporary support structure comprises a plurality of steel arch frames, two adjacent steel arch frames are connected by longitudinal connecting ribs, the steel arch frame comprises a top I-beam unit, a waist I-beam unit, an expanded arch foot I-beam unit and a connecting plate, the connecting plate being respectively welded to both ends of the top I-beam unit, the waist I-beam unit, the expanded arch foot I-beam unit and the initial support arch frame;

[0007] The construction method comprises the following steps:

[0008] S1, semi-finished product processing of the I-beam units of the initial support arch frame and the top I-beam units, waist I-beam units, and expanded arch foot I-beam units in the detachable temporary support structure outside the tunnel, and trial assembly of the first steel arch frame, the semi-finished product processing includes steel plate cutting of I-beams and connecting plates, punching of connecting plates, welding of I-beams and connecting plates, and welding of stiffening ribs and I-beams;

[0009] S2: According to the designed excavation advance requirements, the tunnel upper step heading is excavated and the upper step arch foot is enlarged;

[0010] S3, according to the design requirements, the initial support arch frame construction including mesh spraying, arch frame, anchor rod and shotcrete is carried out, and at the same time, the installation of the expanded arch foot I-beam unit in the detachable temporary support structure is completed. The expanded arch foot I-beam unit is arranged on the lower outer side of the initial support arch frame and the expanded arch foot I-beam unit is detachably connected to the initial support arch frame through a connecting plate and bolts;

[0011] S4, installing a top I-beam unit in the detachable temporary support structure, wherein the top I-beam unit is horizontally arranged on the top of the initial support arch frame and both ends of the top I-beam unit are detachably connected to the initial support arch frame through a connecting plate and bolts;

[0012] S5, installing the waist I-beam unit in the detachable temporary support structure, wherein the waist I-beam unit is symmetrically arranged on both sides of the top I-beam unit, one end of the waist I-beam unit is detachably connected to the initial support arch frame through a connecting plate and bolts, and the other end is detachably connected to the initial support arch frame and the top I-beam unit through a connecting plate and bolts;

[0013] S6, longitudinal connecting bars are used to weld two adjacent steel arches;

[0014] S7: After the arch crown settlement and convergence of the initial supporting arch frame are basically stable, the detachable temporary supporting structure is removed, the waterproof layer is laid, and the invert arch is constructed.

[0015] Furthermore, in S1, when the steel arch frame is processed into frames on the ground and assembled on trial, the circumferential length error is no more than 20 mm, and the plane warping error is no more than 20 mm. After adjustment and verification, they are numbered and can be mass-produced and used in the cave.

[0016] Furthermore, in S1, the top I-beam unit, the waist I-beam unit, and the expanded arch foot I-beam unit are all made of I-18 I-beam, and the size of the stiffening rib is 80mm×35mm×10mm.

[0017] Furthermore, in S3, the length of the arch foot I-beam unit is enlarged to 1 m, and it is installed at an angle of 30° with the horizontal setting.

[0018] Furthermore, in S3, the mesh spraying adopts φ8@200×200mm steel mesh, the anchor rod adopts φ22mm mortar anchor rod L=3.5m@1m×1m plum blossom arrangement, the arch frame adopts I-beam I18@0.5m, and 270 thick C25 sprayed concrete is sprayed.

[0019] Furthermore, in S3, S4 and S5, the spacing between the removable temporary support structures is consistent with the spacing between the initial support arch frames, which is 0.5m.

[0020] Furthermore, the bolts are M20, the connecting plate has a size of 200mm×200mm×15mm, and is provided with 6 bolt holes for installing the connecting bolts.

[0021] Furthermore, in S3, S4 and S5, when the steel arch frames are installed in the holes, the steel arch frames of each cycle step in the same section should be erected in the same plane, and the longitudinal spacing deviation should be within 50 mm.

[0022] Furthermore, in S6, the longitudinal connecting ribs are made of φ22mm threaded steel bars, with a circumferential spacing of 1m and a welding length of 10d.

[0023] Furthermore, in S7, the dismantled detachable temporary support structure can be recycled at the front tunnel face.

[0024] The beneficial effects of the present invention are:

[0025] The present invention can reduce material waste, save construction resources, lower construction costs and improve construction efficiency; at the same time, it can ensure construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention.

[0027] Figure 2 A schematic diagram of the connection of the connection plates of the present invention.

[0028] Figure 3 for Figure 2 Middle aa section view. DETAILED DESCRIPTION

[0029] The following is further described in detail through specific implementation methods:

[0030] The figure numbers in the drawings of the specification include: 1. initial support arch frame; 2. top I-beam unit; 3. waist I-beam unit; 4. expanded arch foot I-beam unit; 5. connecting plate; 6. bolt; 7. stiffening rib.

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The embodiment is basically as shown in the attached Figure 1-3 As shown: a construction method applied to an ultra-shallow buried tunnel in a backfill area, the construction method utilizes the existing formed initial support arch frame 1 of the tunnel, and adopts a detachable temporary support structure to effectively connect with the existing initial support arch frame 1; the detachable temporary support structure includes a plurality of steel arch frames, and the adjacent two steel arch frames are connected by longitudinal connecting ribs, and the steel arch frame includes a top I-beam unit 2, a waist I-beam unit 3, an expanded arch foot I-beam unit 4 and a connecting plate 5, and the connecting plate 5 is respectively welded to the two ends of the top I-beam unit 2, the waist I-beam unit 3, the expanded arch foot I-beam unit 4 and the initial support arch frame 1.

[0033] The construction method includes the following steps:

[0034] S1, process the I-beam units of the initial support arch frame 1 and the top I-beam unit 2, waist I-beam unit 3, and expanded arch foot I-beam unit 4 in the detachable temporary support structure outside the tunnel, and conduct trial assembly of the first steel arch frame. The semi-finished product processing includes steel plate cutting of I-beams and connecting plates, punching of connecting plates, welding of I-beams and connecting plates, and welding of stiffening ribs 7 and I-beams. When the steel arch frame is processed into a frame on the ground and trial assembled, the circumferential length error is no more than 20mm, and the plane warping error is no more than 20mm. After adjustment and qualification, it can be numbered and mass-produced and used in the tunnel. The top I-beam unit, waist I-beam unit, and expanded arch foot I-beam unit are all made of I-18 I-beams, and the size of the stiffening rib 7 is 80mmX35mmX10mm.

[0035] S2: According to the designed excavation advance requirements, the tunnel upper step heading is excavated and the upper step arch foot is enlarged;

[0036] S3, according to the design requirements, the initial support arch frame 1 including mesh spraying, arch frame, anchor rod and shotcrete is constructed, and the installation of the expanded arch foot I-beam unit 4 in the detachable temporary support structure is completed at the same time. The expanded arch foot I-beam unit 4 is arranged on the lower outer side of the initial support arch frame 1 and the expanded arch foot I-beam unit 4 is detachably connected to the initial support arch frame 1 through the connecting plate 5 and the bolt 6. The length of the expanded arch foot I-beam unit is 1m, and it is installed at an angle of 30° to the horizontal setting. The mesh spraying adopts φ8@200×200mm steel mesh, the anchor rod adopts φ22mm mortar anchor rod L=3.5m@1m×1m plum blossom arrangement, the arch frame adopts I-beam 18@0.5m, and 270 thick C25 shotcrete is sprayed.

[0037] S4, installing the top I-beam unit 2 in the detachable temporary support structure, the top I-beam unit 2 is horizontally arranged on the top of the initial support arch 1 and both ends of the top I-beam unit 2 are detachably connected to the initial support arch 1 through the connecting plate 5 and the bolts 6.

[0038] S5, install the waist I-beam unit 3 in the detachable temporary support structure, the waist I-beam unit 3 is symmetrically arranged on both sides of the top I-beam unit 2, one end of the waist I-beam unit 3 is detachably connected to the initial support arch 1 through the connecting plate 5 and the bolt 6, and the other end is detachably connected to the initial support arch 1 and the top I-beam unit 2 through the connecting plate 5 and the bolt 6.

[0039] S6, the two adjacent steel arches are connected by welding with longitudinal connecting bars. The longitudinal connecting bars are made of φ22mm threaded steel bars, with a circumferential spacing of 1m and a welding length of 10d.

[0040] S7, after the arch crown settlement and convergence of the initial support arch frame 1 are basically stable, the detachable temporary support structure is removed, a waterproof layer is laid, and an invert is constructed. The removed detachable temporary support structure can be recycled in the front face.

[0041] The bolts of the present invention are M20, and the performance grade is A; the size of the connecting plate is 200mmX200mmX15mm, and 6 bolt holes are arranged on the connecting plate for installing the connecting bolts.

[0042] When the steel arch frame of the present invention is installed in the hole, the steel arch frames of each cycle step in the same section should be erected in the same plane, and the longitudinal spacing deviation is within 50mm. The spacing of the detachable temporary support structure is consistent with the spacing of the initial support arch frame, both of which are 0.5m

[0043] The present invention utilizes the existing formed steel arch frame initial support of the tunnel, cancels the temporary middle wall and temporary invert in the middle wall method (CD method) or the cross middle wall method (CRD method), adopts a detachable temporary support structure arch frame to be effectively connected with the existing initial support arch frame, so as to replace the temporary middle wall and temporary invert in the original middle wall method (CD method) or the cross middle wall method (CRD method). The present invention can reduce material waste, save construction resources, reduce construction costs and improve construction efficiency; and at the same time can ensure construction safety.

[0044] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0045] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A construction method for an ultra-shallow buried tunnel in a backfill area, characterized in that: The construction method utilizes the existing initial support arch frame of the tunnel, and adopts a detachable temporary support structure to effectively connect with the existing initial support arch frame; the detachable temporary support structure includes a plurality of steel arch frames, and two adjacent steel arch frames are connected by longitudinal connecting ribs, and the steel arch frame includes a top I-beam unit, a waist I-beam unit, an expanded arch foot I-beam unit and a connecting plate, and the connecting plate is respectively welded to the two ends of the top I-beam unit, the waist I-beam unit, the expanded arch foot I-beam unit and the initial support arch frame; The construction method comprises the following steps: S1, semi-finished product processing of the I-beam units of the initial support arch frame and the top I-beam units, waist I-beam units, and expanded arch foot I-beam units in the detachable temporary support structure outside the tunnel, and trial assembly of the first steel arch frame, the semi-finished product processing includes steel plate cutting of I-beams and connecting plates, punching of connecting plates, welding of I-beams and connecting plates, and welding of stiffening ribs and I-beams; S2: According to the designed excavation advance requirements, the tunnel upper step heading is excavated and the upper step arch foot is enlarged; S3, according to the design requirements, the initial support arch frame construction including mesh spraying, arch frame, anchor rod and shotcrete is carried out, and at the same time, the installation of the expanded arch foot I-beam unit in the detachable temporary support structure is completed. The expanded arch foot I-beam unit is arranged on the lower outer side of the initial support arch frame and the expanded arch foot I-beam unit is detachably connected to the initial support arch frame through a connecting plate and bolts; S4, installing a top I-beam unit in the detachable temporary support structure, wherein the top I-beam unit is horizontally arranged on the top of the initial support arch frame and both ends of the top I-beam unit are detachably connected to the initial support arch frame through a connecting plate and bolts; S5, installing the waist I-beam unit in the detachable temporary support structure, wherein the waist I-beam unit is symmetrically arranged on both sides of the top I-beam unit, one end of the waist I-beam unit is detachably connected to the initial support arch frame through a connecting plate and bolts, and the other end is detachably connected to the initial support arch frame and the top I-beam unit through a connecting plate and bolts; S6, longitudinal connecting bars are used to weld two adjacent steel arches; S7: After the arch crown settlement and convergence of the initial supporting arch frame are basically stable, the detachable temporary supporting structure is removed, the waterproof layer is laid, and the invert arch is constructed.

2. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1, characterized in that: In S1, when the steel arch frame is processed into frames on the ground and assembled for trial, the circumferential length error is no more than 20mm, and the plane warping error is no more than 20mm. After adjustment and verification, they are numbered and can be mass-produced and used in the cave.

3. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1 is characterized in that: In S1, the top I-beam unit, the waist I-beam unit, and the expanded arch foot I-beam unit are all made of I-18 I-beam, and the size of the stiffening rib is 80mm×35mm×10mm.

4. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1 is characterized in that: In S3, the length of the expanded arch foot I-beam unit is 1 m, and it is installed at an angle of 30° to the horizontal.

5. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1 is characterized in that: In S3, mesh spraying uses φ8@200×200mm steel mesh, anchor rods use φ22mm mortar anchor rods L=3.5m@1m×1m arranged in plum blossom shape, arch frame uses I-beam I18@0.5m, and sprayed with 270 thick C25 shotcrete.

6. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1, characterized in that: In S3, S4 and S5, the spacing between the removable temporary support structures is consistent with the spacing between the initial support arch frames, which are all 0.5m.

7. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1 is characterized in that: The bolts are M20, the connecting plate has a size of 200mm×200mm×15mm, and is provided with 6 bolt holes for installing the connecting bolts.

8. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1 is characterized in that: In S3, S4 and S5, when the steel arch frame is installed in the hole, the steel arch frame of each cycle step in the same section should be erected in the same plane, and the longitudinal spacing deviation should be within 50mm.

9. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1, characterized in that: In the S6, the longitudinal connecting ribs are made of φ22mm threaded steel bars, with a circumferential spacing of 1m and a welding length of 10d.

10. The construction method for an ultra-shallow tunnel in a backfill area according to claim 1, characterized in that: In S7, the dismantled detachable temporary support structure can be recycled at the front tunnel face.

Images