Mountain tunnel entering construction method and structure

Abstract

The invention relates to the technical field of tunnel construction, and discloses a mountain tunnel hole-entering construction method and structure, the mountain tunnel hole-entering construction structure comprises three cover arches which are connected in sequence and attached to the slope surface of a mountain, and the cover arches are provided with guide pipes pointing to the direction of the mountain; during cover arch construction, cover arch arrangement can be completed without large-area excavation and leveling of a mountain, the guide pipes are used for building a long pipe shed section to support the mountain, and the safety of tunnel entering construction is ensured; the pre-constructed hidden hole section is arranged to enable the cover arch and the mountain body to form a closed environment, the cover arch section and the long pipe shed section provide stable support after arrangement is completed, construction personnel can conduct tunneling construction conveniently, arrangement can be completed without large-area excavation to eliminate an upward slope during construction of the structure, the construction efficiency is effectively improved, and the local environment is prevented from being damaged; and stable supporting is provided according to the field geological environment, and the overall safety of the tunnel portal is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and particularly to a construction method and structure for a mountain tunnel to enter the hole. Background Art

[0002] At present, the development speed of road infrastructure such as highways and railways in China is relatively fast. China's terrain is mainly mountainous and hilly, and excavating tunnels is a relatively common construction method for crossing mountains and hills; therefore, excavating tunnels is frequently used in current road construction.

[0003] In the existing tunnel construction methods, when entering the hole for construction in a concave valley terrain, it is necessary to carry out large-area excavation and slope brushing of the mountain body to obtain a working surface for entering the hole construction. According to the actual situation on site, blasting operations may also be required, which will cause problems such as damage to the mountain body structure and the surrounding environment; in addition, for mountain bodies with too high side slopes, the excavation volume and protection engineering volume will be greatly increased, resulting in problems such as extended construction period. For mountain bodies with different degrees of hardness and softness of the soil on the working surface, using the same protection will lead to insufficient safety of the support. Summary of the Invention

[0004] The purpose of the present invention is to provide a construction method and structure for a mountain tunnel to enter the hole, which can achieve safe support and hole entry construction through a small amount of excavation, without large-area excavation of the mountain body, protect the environment and effectively improve the construction efficiency.

[0005] To achieve the above purpose, the present invention provides a construction method and structure for a mountain tunnel to enter the hole. The construction structure includes an arch segment, a long pipe shed segment, and a prefabricated blind tunnel segment. The arch segment is arranged on the outside of the mountain body and is connected to the mountain body through a guide pipe. The long pipe shed segment is arranged on the inside of the mountain body and is set along the tunnel construction direction. The prefabricated blind tunnel segment is arranged between the arch segment and the mountain body; the arch segment includes a first arch, a second arch, and a third arch that are sequentially connected and arranged from the outside to the inside of the mountain body along the mountain slope.

[0006] Preferably, the top heights and arch curvatures of the first arch, the second arch, and the third arch are the same;

[0007] The projection of the arch segment on the horizontal plane is an axisymmetric structure. The projections of the first arch, the second arch, and the third arch are all rectangles, and the length of the rectangle perpendicular to the tunnel construction direction is the maximum width of the corresponding arch. The maximum widths of the first arch, the second arch, and the third arch decrease in sequence.

[0008] Preferably, the construction structure further includes a steel arch frame for supporting the guide pipe. Connecting bars are arranged between multiple steel arch frames. The two ends of the connecting bar are respectively connected to the steel arch frames at its two ends. The spacing between adjacent connecting bars is 0.8 - 1.5 meters.

[0009] Preferably, the long pipe shed section includes long pipe shed steel pipes, and the external insertion angle of the long pipe shed steel pipes is 1° to 3°.

[0010] The construction method for a mountain tunnel to enter the hole includes the following steps:

[0011] The first step: Conduct the construction of the arch segment. Set three arch construction areas, namely the first arch area, the second arch area, and the third arch area, from the outside of the mountain body to the inside along the mountain slope. Set the first arch in the first arch area, the second arch in the second arch area, and the third arch in the third arch area. Confirm the positions and construction dimensions of the three construction areas according to the on-site terrain conditions;

[0012] The second step: Fabricate the arch steel arch frame and the reinforced arch formwork according to the preset arch dimensions;

[0013] The third step: Excavate the corresponding foundations for the three arch construction areas in sequence, set steel arch frames in the corresponding areas, then install guide pipes on the steel arch frames along the hole-entering construction direction, and install arch formwork according to the arch shape. Pour the three arches into shape in sequence, so that both ends of the three arches are located on the surface of the mountain body;

[0014] The fourth step: Excavate a groove at the edge of the prefabricated blind tunnel section, and conduct concrete pouring and primary lining construction for the prefabricated blind tunnel section;

[0015] The fifth step: Drive the long pipe shed steel pipes into the mountain body in sequence along the hole-entering construction direction, determine the driving length of the long pipe shed steel pipes according to the geological hardness of each part of the mountain body, and conduct construction reinforcement for the long pipe shed section at the tunnel entrance;

[0016] The sixth step: Excavate the mountain body, and conduct grouting treatment on the long pipe shed steel pipes through grouting small pipes;

[0017] The seventh step: Conduct secondary lining construction for the prefabricated blind tunnel section;

[0018] The eighth step: Enter the space in the middle of the arch to conduct tunnel excavation construction;

[0019] The ninth step: Construct the portal end wall, and conduct soil backfilling construction for the arch section after the end wall is completed.

[0020] Preferably, before the construction of the arch section, it is necessary to first survey the terrain and geology of the construction location and conduct construction layout, collect relevant data and confirm the construction plan;

[0021] Subsequently, clean up the dangerous rocks at the construction site; confirm the drain ditch dimensions according to the rainfall runoff volume at the construction location and construct the drain ditch.

[0022] Preferably, during the construction of the first arch, after the foundation excavation is completed, set up a steel reinforcement cage and reinforcement steel pipes of the same model as the long pipe shed steel pipes at the foundation to reinforce the foundation.

[0023] Preferably, during the construction of the second set of arches, after the foundation excavation is completed, concrete is poured to reinforce the foundation, and steel bars and steel bar meshes are welded to be longitudinally attached to the mountain wall; then the guiding pipes of the second set of arches are installed, and one end of the guiding pipes of the second set of arches is connected to the mountain body.

[0024] Preferably, during the construction of the prefabricated blind tunnel section, a settlement joint is provided between the side walls of the prefabricated blind tunnel section and the side walls of the arch sets. The width of the settlement joint is selected to be 20 - 30 cm. Asphalt hemp ropes are placed into the settlement joint from both sides of the settlement joint to fill the settlement joint, and the depth of the asphalt hemp ropes is greater than or equal to 15 cm.

[0025] Preferably, when setting up the steel arch frames, the steel arch frames are placed obliquely along the slope of the mountain body, and then the steel arch frames are successively adjusted from the inclined state to the state perpendicular to the foundation of the corresponding arch set section. After being adjusted to the vertical state, the steel arch frames are fixed on the foundation, and adjacent steel arch frames are connected to each other.

[0026] Compared with the prior art, the construction method and structure of the mountain tunnel entrance in the embodiment of the present invention have the beneficial effects as follows: Through three successively connected arch sets, the arch set section can be arranged along the slope of the mountain body. The guiding pipes are arranged on the arch set section and point towards the mountain body. When constructing the arch sets, large - area excavation and slope brushing are not required, and the setting of the arch sets can be completed. During this process, the mountain structure and environment of the construction operation surface can be ensured not to be damaged, and the construction time can be effectively saved; According to the guiding pipes of the arch set section, the construction directions of the steel pipes forming the long pipe shed can be determined, which is convenient for subsequent construction; The arch set section and the long pipe shed section provide support for the mountain body, improving the safety of tunnel construction; According to the on - site topography and geology, the setting positions of the three arch sets are determined, and the three arch sets are successively set up to form the arch set section. Through the arch sets and the long pipe shed, support is provided for the tunnel construction at the entrance, which is convenient for subsequent tunnel excavation construction for entering the hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is the top - view of the construction structure of a construction method and structure for a mountain tunnel entrance in an embodiment of the present invention.

[0028] Figure 2 FIG. is the schematic diagram of the support structure of the steel arch frame of the construction structure of a construction method and structure for a mountain tunnel entrance in an embodiment of the present invention.

[0029] Figure 3 FIG. is the schematic diagram of the support of the construction structure of a construction method and structure for a mountain tunnel entrance in an embodiment of the present invention.

[0030] In the figure, 1. arch set section; 11. the first arch set; 12. the second arch set; 13. the third arch set; 14. reinforcement steel pipes; 2. long pipe shed section; 21. long pipe shed steel pipes; 3. prefabricated blind tunnel section. DETAILED DESCRIPTION OF THE INVENTION

[0031] The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0032] In the description of the present invention, it should be understood that in the description of the present invention, the orientation or positional relationship indicated by terms such as "upper" and "lower" in the present invention is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, terms such as "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] As Figures 1 - 3 shown, a construction method and structure for a mountain tunnel to enter the hole in a preferred embodiment of the present invention. The mountain tunnel entrance construction structure includes an arch segment 1, a long pipe shed segment 2, and a pre-constructed blind tunnel segment 3. The arch segment 1 is arranged on the outside of the mountain and is connected to the mountain through a guide pipe. The long pipe shed segment 2 is arranged on the inside of the mountain and is arranged along the tunnel construction direction. The pre-constructed blind tunnel segment 3 is arranged between the arch segment 1 and the mountain. The arch segment 1 includes a first arch 11, a second arch 12, and a third arch 13 that are sequentially connected and arranged from the outside of the mountain inward along the mountain slope.

[0034] Specifically, the first arch 11, the second arch 12, and the third arch 13 are sequentially connected and arranged along the mountain slope. The tunnel construction direction is the same as the opening direction of the arch segment 1. There are multiple guide pipes and they are arranged sequentially along the contours of the first arch 11, the second arch 12, and the third arch 13. The guide pipes extend to the mountain surface. The long pipe shed segment 2 is composed of long pipe shed steel pipes 21. During the construction of the long pipe shed segment 2, it is positioned through the guide pipes of the arch segment 1, and the long pipe shed steel pipes 21 are driven into the mountain along the guide pipes. Thus, the long pipe shed segment 2 is connected to the arch segment 1 and extends into the mountain along the tunnel construction direction. The arch segment 1 and the long pipe shed segment 2 provide support for the subsequent tunneling construction. The pre-constructed blind tunnel segment 3 is arranged between the arch and the mountain, making the arch and the mountain form a closed structure, improving the waterproof performance and safety.

[0035] It can make the arch fit the mountain slope, which is convenient for subsequent construction. When constructing this structure, there is no need to carry out large-area excavation of the mountain, effectively saving construction time and reducing damage to the mountain.

[0036] Preferably, the top heights and the arch curvatures of the first arch 11, the second arch 12, and the third arch 13 are the same;

[0037] The projection of the arch segment 1 on the horizontal plane is an axisymmetric structure. The projections of the first arch 11, the second arch 12, and the third arch 13 are all rectangles, and the length of the rectangle perpendicular to the construction direction of the tunnel is the maximum width of the corresponding arch. The maximum widths of the first arch 11, the second arch 12, and the third arch 13 decrease in sequence.

[0038] Specifically, both ends of the three arches are arranged on the mountain surface, and the mountain surface provides support for the arch segment. The first arch 11, the second arch 12, and the third arch 13 are arranged along the same axis, so that the tops of the three arches are at the same height; as Figure 1 shown, the projections of the first arch 11, the second arch 12, and the third arch 13 on the horizontal direction are all rectangles. The length of the projected rectangle of the first arch 11 is greater than that of the projected rectangle of the second arch 12, and the length of the projected rectangle of the second arch 12 is greater than that of the projected rectangle of the third arch 13, so that the heights where the two ends of the third arch 13 are located are higher than the heights where the two ends of the second arch 12 are located, and the heights where the two ends of the second arch 12 are located. The three arches can fit the mountain slope, and the setting of the arches can be completed without large-area excavation and leveling of the working surface, which is convenient for the subsequent construction of the long pipe shed section 2 and the tunnel excavation construction.

[0039] Preferably, the construction structure further includes steel arch frames for supporting the guide pipes. Connecting bars are arranged between multiple steel arch frames. The two ends of the connecting bar are respectively connected to the steel arch frames at its two ends, and the distance between adjacent connecting bars is 0.8 - 1.5 meters.

[0040] Specifically, the steel arch frames are connected by φ22mm steel bars. The connecting bars are arranged horizontally in the transverse direction. The adjacent connecting bars are arranged at a circumferential spacing of 1.0m. The two ends of the connecting bar are firmly welded to the steel arch frames at its two ends, controlling multiple steel arch frames of the same arch on the same horizontal plane, which can increase the integrity and stability of multiple steel arch frames.

[0041] Preferably, the long pipe shed section 2 includes long pipe shed steel pipes 21, and the external insertion angle of the long pipe shed steel pipes 21 is 1° to 3°.

[0042] Specifically, the long pipe shed steel pipes 21 are driven into the mountain body at an external insertion angle of 1° - 3° along the periphery of the tunnel, which is used to control the drilling direction and elevation, so as to effectively control the reinforcement range of the grouting operation and prevent over-excavation and under-excavation of the tunnel body;

[0043] During the construction of the long pipe shed, draw the contour line of the long pipe shed along the mountain slope. Use a down-the-hole drill to drill the mountain body along the guide pipe of the arch. After the drilling is completed, insert the long pipe shed steel pipes 21 into the drilled holes in the mountain body along the guide pipe of the arch. The external insertion angle of the guide pipe of the arch is also 1° - 3° to ensure the external insertion angle of the long pipe shed steel pipes 21. After the long pipe shed steel pipes 21 are set, grout the long pipe shed steel pipes 21 to reinforce the long pipe shed.

[0044] A method for constructing a mountain tunnel entrance using the above-mentioned mountain tunnel entrance construction structure, comprising the following steps:

[0045] The first step: Carry out the construction of the arch rings. Set three arch ring construction areas, namely the first arch ring area, the second arch ring area, and the third arch ring area, in sequence from the outside to the inside of the mountain along the mountain slope. Install the first arch ring 11 in the first arch ring area, install the second arch ring 12 in the second arch ring area, and install the third arch ring 13 in the third arch ring area. Confirm the positions and construction dimensions of the three construction areas according to the on-site terrain conditions;

[0046] The second step: Fabricate the arch ring steel arch frames and the reinforced arch ring formworks according to the preset arch ring dimensions;

[0047] The third step: Excavate the corresponding foundations for the three arch ring construction areas in sequence, install the steel arch frames in the corresponding areas, then install the guide pipes on the steel arch frames along the tunnel entrance construction direction, and install the arch ring formworks according to the arch ring shapes. Pour the three arch rings into shape in sequence, so that both ends of the three arch rings are set on the surface of the mountain;

[0048] The fourth step: Excavate a groove at the edge of the prefabricated blind tunnel section 3, and carry out concrete pouring and primary lining construction on the prefabricated blind tunnel section 3;

[0049] The fifth step: Drive the long pipe shed steel pipes 21 into the mountain body in sequence along the tunnel entrance construction direction, determine the driving lengths of the long pipe shed steel pipes 21 according to the geological hardness of each part of the mountain body, and reinforce the long pipe shed section 2 at the tunnel entrance;

[0050] The sixth step: Excavate the mountain body, and carry out grouting treatment on the long pipe shed steel pipes 21 through the grouting small pipes;

[0051] The seventh step: Carry out secondary lining construction on the prefabricated blind tunnel section 3;

[0052] The eighth step: Enter the space in the middle of the arch ring to carry out tunnel excavation construction;

[0053] The ninth step: Construct the portal end wall, and carry out soil backfilling construction on the arch ring section 1 after the end wall is completed.

[0054] Specifically, when carrying out tunnel entrance construction on the side of the mountain body, first select the tunnel entrance construction area according to the construction requirements. After confirming the tunnel construction area, operate according to the following steps:

[0055] The first step: Measure and set out according to the on-site measured elevation and geological conditions. Use the drill rig platform to excavate and level the ground in front of the tunnel entrance working surface to determine the positions of the first arch ring area, the second arch ring area, and the third arch ring area, so as to facilitate the subsequent construction of the arch ring section 1.

[0056] Step 2: Fabricate the steel arch and the reinforcing steel arch formwork according to the preset arch dimensions for subsequent construction, which can effectively accelerate the construction progress.

[0057] Step 3: Excavate and level the foundation of the first arch area, then reinforce the foundation, erect the I-beam arch for support, and install the guide pipes of the first arch 11 and the arch formwork of the first arch 11 through the I-beam arch. Among them, multiple guide pipes are sequentially arranged on the outer periphery of the steel arch (i.e., the middle position after the formation of the first arch 11) along the contour of the first arch 11, and then pour concrete to form the first arch 11. The two ends of the first arch 11 are set on the foundation of the first arch area. After the first arch 11 is formed, excavate the foundation of the second arch area, reinforce the foundation, install or replace the I-beam arch for support, then install the guide pipes of the second arch 12 and the arch formwork, and pour concrete to form the second arch 12. The two ends of the second arch 12 are set on the foundation of the second arch area. After the second arch 12 is formed, excavate and reinforce the foundation of the III area, set the I-beam arch, install the guide pipes of the third arch 13 and the arch formwork, and pour concrete to form the third arch 13. The two ends of the third arch 13 are set on the foundation of the third arch area. Cure the first arch 11, the second arch 12, and the third arch 13. By the above method, there is no need to conduct large-area excavation of the mountain body, enabling the arch to be set along the mountain slope, effectively protecting the environment and saving construction time.

[0058] Step 4: The prefabricated blind tunnel section 3 is arranged in the gap between the arch and the mountain body. After trenching, use the I-beam arch as support, set the steel mesh and cover plate, and pour concrete to form it. After the prefabricated blind tunnel section 3 is formed, conduct the primary lining construction, cure the prefabricated blind tunnel section 3, and after the curing is completed, conduct clay backfilling to improve the strength and stability. Setting the prefabricated blind tunnel section 3 can connect the arch with the mountain body and provide stable support for subsequent construction.

[0059] Step 5: Drive the long pipe shed steel pipes 21 into the mountain body along each guide pipe of the arch. The driving length of the long pipe shed steel pipes 21 into the mountain body is determined by the hardness of the corresponding mountain soil. As Figure 1 shown, assuming that the soil on the left side of the mountain is softer, so the length of the long pipe shed steel pipes 21 driven into the left mountain body is longer. The long pipe shed steel pipes 21 provide support for the mountain body at the tunnel entrance working surface, improve safety, and facilitate subsequent tunnel excavation construction.

[0060] Step 6: Excavate the mountain body to make the tunnel entrance working surface in a state ready for tunnel excavation, which is convenient for subsequent construction; grout the long pipe shed steel pipes 21 through the grouting small pipes. After the grout solidifies, the strength of the long pipe shed section 2 is improved, and the support capacity is enhanced.

[0061] Step 7: Conduct the secondary lining construction of the prefabricated blind tunnel section 3 to improve the stability of the prefabricated blind tunnel section 3.

[0062] Eighth step: Excavate the mountain along the extension directions of the arch segment 1 and the long pipe shed segment 2 to construct the tunnel. Adopt the construction method of leaving the core soil in the upper and lower benches or the CD (CRD) method, excavate and support each segment one by one, and quickly form a ring to improve safety and complete the tunnel construction.

[0063] Ninth step: Backfill the mountain, bury the top and both sides of the arch segment 1 into the backfill soil, making the arch segment 1 become the hidden part of the tunnel. The first arch 11 is the tunnel entrance. Subsequently, improve the drainage system and greening construction at the entrance to complete the tunnel construction.

[0064] Through the above construction method for the mountain tunnel entrance, there is no need to conduct large-scale excavation of the mountain during the entrance construction. Multiple arch segments can be directly set along the mountain, avoiding damage to the mountain structure and the environment. Moreover, steel pipes of different lengths can be set according to the hardness of the soil at the working face to provide stable support, improving the safety of the tunnel entrance construction; while ensuring safety, it can effectively shorten the construction period and reduce construction energy consumption.

[0065] Preferably, before the arch segment construction, it is necessary to first survey the topography and geology of the construction location and conduct construction layout, collect relevant data and confirm the construction plan;

[0066] Subsequently, clear the dangerous rocks at the construction site; confirm the size of the drainage ditch according to the rainfall catchment volume at the construction location and construct the drainage ditch.

[0067] Specifically, first conduct on-site survey and construction layout for the entrance construction section, detect whether there are adverse geological conditions or shallow-buried and bias pressure situations in the nearby topography and geomorphology, and design and draw the cross-section of the entrance excavation according to the survey results; to determine the relevant conditions of the construction working face, facilitating the formulation of subsequent construction plans and the relevant parameters of the construction structure.

[0068] Subsequently, deal with the dangerous rocks and other sundries at the entrance construction section, and dig a drainage ditch according to the concave valley topography of the mountain. The drainage ditch extends from the top of the entrance working face to both sides of the entrance working face and finally converges at the gully below the entrance working face, so that the water flow does not flow through the entrance working face, reducing the influence of the water flow on the entrance working face; the size of the drainage ditch is determined by the rainwater flowmeter installed at the gully; to improve the stability of the entrance working face and facilitate construction.

[0069] Preferably, when constructing the first arch 11, after the foundation excavation is completed, set up a steel reinforcement cage at the foundation and use a reinforcement steel pipe 14 of the same model as the long pipe shed steel pipe 21 to reinforce the foundation.

[0070] Specifically, the reinforcement steel pipe 14 at the arch segment foundation needs to be connected to the reinforcement steel pipe 14 at the bottom foundation during the tunnel excavation construction. The reinforcement steel pipe 14 has the same size as the long pipe shed steel pipe 21, which is convenient for material preparation and subsequent connection operations such as welding.

[0071] Preferably, when constructing the second set of arches 12, after the foundation excavation is completed, concrete is poured to reinforce the foundation, and steel bars and steel bar meshes are welded until they are attached to the mountain longitudinally; subsequently, the guide pipes of the second set of arches 12 are installed, and one end of the guide pipes of the second set of arches 12 is connected to the mountain body.

[0072] Specifically, when constructing the second set of arches 12, it is necessary to excavate the foundation and reinforce the foundation by pouring concrete, erect I-beams and weld steel bars and steel bar meshes. The steel bars and steel bar meshes extend to be attached to the mountain body. The guide pipes of the second set of arches 12 are collinear with the guide pipes of the first set of arches 11. One end of the guide pipes of the second set of arches 12 is tightly connected to the surface of the mountain body. When constructing the long pipe shed section 2, the mountain body can be directly drilled through the guide pipes of the second set of arches 12, which is convenient for the construction of installing the long pipe shed steel pipes 21 and the subsequent grouting construction of the long pipe shed steel pipes 21 through the small pipes.

[0073] Preferably, when constructing the prefabricated hidden tunnel section 3, settlement joints are arranged between the side walls of the prefabricated hidden tunnel section 3 and the side walls of the set of arches. The width of the settlement joints is selected to be 20 - 30 cm. Asphalt hemp ropes are placed into the settlement joints from both sides of the settlement joints to fill the settlement joints, and the depth of the asphalt hemp ropes is greater than or equal to 15 cm.

[0074] Specifically, when the prefabricated hidden tunnel section 3 is formed by pouring, a 23-cm settlement joint is reserved between the side wall of the prefabricated hidden tunnel section 3 and the corresponding set of arches to prevent uneven settlement between the set of arches and the prefabricated hidden tunnel section 3 from damaging the overall structure. Asphalt hemp ropes are placed into the settlement joints from the openings on both sides of the settlement joints to ensure the waterproofness of the support structure formed by the set of arches and the prefabricated hidden tunnel section 3.

[0075] Preferably, when setting up the steel arch frames, the steel arch frames are placed obliquely along the slope of the mountain body, and then the steel arch frames are successively adjusted from the inclined state to the state perpendicular to the foundation of the corresponding set of arch sections 1. After being adjusted to the vertical state, the steel arch frames are fixed on the foundation, and adjacent steel arch frames are connected to each other; this can effectively reduce the pressure on the foundation where the steel arch frames are located and is convenient for observing whether the soil is too soft during the setting up of the steel arch frames, resulting in insufficient supporting force, and can be adjusted in time to avoid large damage to the construction section.

[0076] Preferably, the size of the guide pipes of the set of arches is φ140mm×4.5mm, the length is 1m - 3m, and the circumferential spacing is 30 - 50 cm; φ16 fixing steel bars are used to weld the guide pipes and the I-beams firmly, and the weld length is greater than 15 cm; to ensure that sufficient supporting strength can be provided and for the down-the-hole drill to drill the mountain body for construction.

[0077] Preferably, the outer diameter of the long tube rack steel pipe 21 is 89mm or 108mm, the wall thickness is 6mm or 8mm, and one end of the steel pipe is a pointed cone to facilitate the steel pipe to be driven into the mountain; grouting holes with a diameter of 5-10mm are provided around the steel pipe, and the spacing between the grouting holes is 15cm to facilitate grouting operations, so that a higher strength support is formed around the steel pipe.

[0078] In addition, during the construction of the arch section, the first arch area, the second arch area and the third arch area all used blasting machines to excavate the foundation, with a foundation depth of 5 meters; foundation reinforcement: 8φ108 steel pipes, 6m in length, grouting pressure 2-3MPa, with 4φ16 steel cages (steel bars, channel steels and arch steel bars welded to form a whole);

[0079] The allowable deviation of steel arch assembly is ±3cm, the plane warping should be less than 2cm, and the spacing is 0.75m; the steel arch should be installed strictly according to the designed center line and horizontal position, and the lower end of the steel arch is set on the arch foundation and fixed firmly with ground anchors. The three steel arches are connected with φ22 steel bars, and the connecting bars are arranged at a circumferential spacing of 1.0m and are welded firmly to the steel arch.

[0080] The working process of the present invention is as follows: when tunnel construction is carried out on the side of a mountain, a tunnel entrance construction area is first selected according to construction needs. After the tunnel construction area is confirmed, a field survey and construction layout are carried out on the tunnel entrance construction section to detect the nearby terrain and soil quality and whether there is unfavorable geology or shallow buried bias. The cross-section of the tunnel entrance excavation is designed and drawn according to the survey results to determine the relevant conditions of the construction working surface, so as to facilitate the specification of relevant parameters of subsequent construction plans and construction structures.

[0081] After formulating the plan, the dangerous rocks and other debris on the working surface are dealt with, and the size of the drainage ditch is determined according to the rainfall measured by the local rainwater flow meter to ensure that the drainage ditch can drain all the rainwater. Subsequently, the drainage ditch is dug along the concave valley terrain of the mountain. The drainage ditch extends from the top of the cave entrance working surface to both sides of the cave entrance working surface and finally converges in the valley below the cave entrance working surface, so that the water does not flow through the cave entrance working surface, reducing the impact of the water flow on the cave entrance working surface.

[0082] According to the measured elevation and geological conditions on site, the survey and layout are carried out, and the ground in front of the tunnel entrance is excavated and leveled using a drilling rig platform. The positions of the first, second and third arch areas are determined according to the slope of the mountain. The tunnel centerline and the elevation of the outer arch crown are marked on the slope, and the outer arch line is drawn as a basis to make steel arch frames and steel arch templates in preparation for subsequent construction.

[0083] Use a hydraulic breaker to excavate and level the foundation of the first arch area. The foundation depth is 5 meters. Subsequently, set 8 φ108 steel pipes and 4 φ16 steel reinforcement cages at the foundation of the first arch area, and reinforce the foundation by pouring concrete with a grouting pressure of 2 - 3 MPa; after the concrete hardens, erect a steel arch frame formed by I-beams to provide support. When installing the I-beams, the allowable deviation for peripheral assembly is ±3 cm, and the planar warping should be less than 2 cm. 3 sets of 25b I-beam arch frames can be set inside the lagging arch, with a spacing of 0.75 m. When installing the steel arch frame, it should be erected strictly according to the designed center line and horizontal position. The lower end of the steel arch frame is set on the lagging arch foundation and fixed firmly with ground anchors. The steel arch frames are connected by φ22 steel bars as connecting bars, and the connecting bars are arranged at a circumferential spacing of 1.0 m and welded firmly to the steel arch frames; after the installation of the I-beam arch frames is completed, install the guide pipes and lagging arch templates of the first arch 11. The guide pipes are made of φ140mm×4.5mm steel pipes, and the length is determined by the length of the first arch 11 along the tunnel construction direction. The circumferential spacing is 40 cm. Use φ16 fixing steel bars to weld the guide pipes of the first arch 11 firmly to the I-beam arch frames. Use double-sided welding, and the weld length is greater than 15 cm. The external insertion angle of the guide pipe installation is 3°. The end of the guide pipe is pressed tightly against the lagging arch template to prevent concrete from entering the guide pipe and blocking it during concrete pouring. Then pour concrete to form the first arch 11. The two ends of the first arch 11 are set on the foundation of area I;

[0084] After the first arch 11 is formed, excavate the foundation of the second arch area, reinforce the foundation, and the parameters of the foundation are the same as those of the first arch area. Subsequently, install or replace the I-beams for support, weld the steel bars and steel bar meshes to be longitudinally attached to the wall, and then install the guide pipes and lagging arch templates of the second arch 12. The material parameters are the same as those of the first arch 11. Pour concrete to form the second arch 12. The two ends of the second arch 12 are set on the foundation of the second arch 12; after the second arch 12 is formed, carry out the construction of the third arch 13 in the third arch area. The construction steps of the third arch 13 are the same as those of the second arch 12; after the lagging arches are formed, cure the first arch 11, the second arch 12, and the third arch 13; there is no need for large-area excavation, so that the lagging arches can be set along the mountain slope, effectively protecting the environment and saving construction time.

[0085] After the construction of the arch lining is completed, use the I-beam arch support to set up the steel mesh and cover plate. The mesh size of the steel mesh is 15 cm x 15 cm. Install the cover plate above the I-beam arch support and the steel mesh to form a closed boundary for shotcrete. Pour concrete to form the precast blind tunnel section 3, and leave a settlement joint of 23 cm between the side wall of the precast blind tunnel section 3 and the corresponding arch lining to prevent uneven settlement between the arch lining and the precast blind tunnel section 3 from damaging the overall structure. Put asphalt hemp ropes into the settlement joint from the openings on both sides of the settlement joint; after the precast blind tunnel section 3 is formed, carry out the primary lining construction, cure the precast blind tunnel section 3, and backfill with clay after curing to improve the strength and stability; enable the precast blind tunnel section 3 to connect the arch lining with the mountain body and provide stable support for subsequent construction.

[0086] Subsequently, use a down-the-hole drill to drill holes in the mountain body along each guide pipe of the arch lining. After drilling, drive the long pipe shed steel pipes 21 into the drilled holes in the mountain body along the guide pipes of the arch lining in sequence. The long pipe shed steel pipes 21 are driven into the mountain body at an external insertion angle of 1° - 3° along the periphery of the tunnel; the length of the steel pipes driven into the mountain body is determined by the hardness of the mountain soil. The softer the soil, the longer the length of the steel pipes driven in. The steel pipes provide support for the mountain body at the entrance working face.

[0087] Excavate the mountain body to make the entrance working face in a state ready for tunnel excavation, which is convenient for subsequent construction; grout the guide pipes of the arch lining through the grouting small pipes. After the grout solidifies, improve the strength of the guide pipes of the arch lining and the long pipe shed steel pipes 21 and enhance the support capacity.

[0088] Carry out the secondary lining construction for the precast blind tunnel section 3 to improve the stability of the precast blind tunnel section 3.

[0089] Carry out tunneling construction on the mountain body along the extension direction of the arch lining and the long pipe shed, excavate the tunnel, and use the method of leaving a core soil in the upper and lower benches or the CD (CRD) method for construction. Excavate and support each segment one by one to quickly form a ring to improve safety and complete the tunnel construction.

[0090] Backfill the mountain body, bury the top and both sides of the arch lining section 1 into the backfill soil to make the arch lining section 1 become the blind tunnel part of the tunnel. The first arch lining 11 is the tunnel entrance, and complete the drainage system and greening construction at the entrance to complete the tunnel construction.

[0091] In summary, the embodiment of the present invention provides a method and structure for a mountain tunnel to enter the hole. By setting three arch linings that fit the mountain body and forming a support for the tunnel to enter the hole with the long pipe shed, it is not necessary to carry out large-area excavation to eliminate the cut slope, improve the construction efficiency, and protect the local environment; and adjust the long pipe shed steel pipes 21 according to the hardness of the soil to improve the overall safety of the support.

[0092] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A mountain tunnel entry construction structure, characterized in that: It includes an arch section, a long pipe shed section and a prefabricated blind tunnel section. The arch section is arranged on the outside of the mountain and connected to the mountain through a guide pipe. The long pipe shed section is arranged on the inside of the mountain and along the tunnel construction direction. The prefabricated blind tunnel section is arranged between the arch section and the mountain. The arch section includes a first arch, a second arch and a third arch which are connected and arranged in sequence from the outside of the mountain to the inside along the slope of the mountain.

2. The mountain tunnel entry construction structure according to claim 1, characterized in that: The top heights and curvatures of the first set of arches, the second set of arches and the third set of arches are all the same; The projection of the arch segment on the horizontal plane presents an axisymmetric structure. The projections of the first arch, the second arch and the third arch are all rectangular, and the length of the rectangle perpendicular to the construction direction of the tunnel is the maximum width of the corresponding arch. The maximum widths of the first arch, the second arch and the third arch decrease successively.

3. The mountain tunnel entry construction structure according to claim 1, characterized in that: It also includes a steel arch frame for supporting the guide tube, and connecting ribs are provided between the plurality of the steel arch frames. The two ends of the connecting ribs are respectively connected to the steel arch frames at the two ends thereof, and the spacing between adjacent connecting ribs is 0.8-1.5 meters.

4. The mountain tunnel entry construction structure according to claim 1, characterized in that: The long tube shelf section comprises a long tube shelf steel pipe, and the external insertion angle of the long tube shelf steel pipe is 1° to 3°.

5. A mountain tunnel construction method, characterized in that: The following steps are involved: Step 1: Carry out the arch section construction. Set up the first arch area, the second arch area, and the third arch area in sequence along the mountain slope from the outside of the mountain to the inside. Set up the first arch in the first arch area, the second arch in the second arch area, and the third arch in the third arch area. Confirm the location and construction size of the three construction areas according to the on-site terrain conditions; Step 2: Make the arch steel frame and the steel arch template according to the preset arch size; Step 3: Excavate the corresponding foundations for the three arch construction areas in turn, set up steel arch frames in the corresponding areas, then install guide pipes on the steel arch frames along the construction direction of the tunnel, and install arch templates according to the arch shape, and cast the three arches in turn so that both ends of the three arches are located on the surface of the mountain; Step 4: Dig a groove at the edge of the prefabricated blind tunnel section, pour concrete and perform primary lining construction on the prefabricated blind tunnel section; Step 5: Drive the long-tube shed steel pipes into the mountain in sequence along the direction of the tunnel construction. Determine the driving length of the long-tube shed steel pipes according to the geological softness and hardness of various parts of the mountain, and reinforce the long-tube shed section at the tunnel entrance; Step 6: Excavate the mountain and inject grout into the long-tube shed steel pipe through a small grouting pipe; Step 7: Carry out secondary lining construction on the prefabricated blind tunnel section; Step 8: Enter the space in the middle of the sleeve arch to carry out tunnel excavation construction; Step 9: Construct the end wall of the opening. After the end wall is completed, backfill the arch section with soil.

6. The mountain tunnel construction method according to claim 5, characterized in that: Before the construction of the arch section, it is necessary to first survey the topography and geology of the construction location, make layout, collect relevant information and confirm the construction plan; Then, the dangerous rocks at the construction site are cleared; the size of the drainage ditch is confirmed and the drainage ditch is installed according to the rainfall at the construction location.

7. The mountain tunnel construction method according to claim 5, characterized in that: During the construction of the first set of arches, after the foundation excavation is completed, a steel cage and reinforcing steel pipes of the same type as the long tube shed steel pipes are set at the foundation to reinforce the foundation.

8. The mountain tunnel construction method according to claim 5, characterized in that: During the construction of the second set of arches, after the foundation excavation is completed, concrete is poured to reinforce the foundation, and steel bars and steel mesh are welded to the longitudinal wall of the mountain; then the guide pipe of the second set of arches is installed, and one end of the guide pipe of the second set of arches is connected to the mountain.

9. The mountain tunnel construction method according to claim 5, characterized in that: During the construction of the prefabricated blind tunnel section, a settlement joint is set between the side wall of the prefabricated blind tunnel section and the side wall of the sleeve arch. The width of the settlement joint is selected to be 20-30 cm. Asphalt hemp tendons are placed from both sides of the settlement joint to fill the settlement joint. The depth of the asphalt hemp tendons is greater than or equal to 15 cm.

10. The mountain tunnel construction method according to claim 5, characterized in that: When setting up the steel arch frame, the steel arch frame is placed obliquely along the slope of the mountain, and then the steel arch frame is adjusted from the inclined state to a state perpendicular to the foundation of the arch section in sequence. After adjusting to the vertical state, the steel arch frame is fixed to the foundation, and adjacent steel arch frames are connected to each other.

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