Supporting structure for tunnel underneath pass structure construction

Abstract

The utility model discloses a supporting structure for construction of a tunnel underneath passing structure, which comprises an outer layer support, an inner layer support, an outer layer support, an inner layer support, an inner layer support and an outer layer support, and is characterized in that the outer layer support comprises an outer layer arch frame arranged in an excavated tunnel area at intervals; the outer-layer inverted arch and the outer-layer arch frame form closed annular outer supporting structures along the tunnel section contour line, and the annular outer supporting structures are connected into a whole through concrete and form a primary supporting layer; the inner-layer support comprises inner-layer arch frames which are arranged in the support section at intervals; the inner-layer inverted arch and the corresponding inner-layer arch frame are arranged on the inner side of the primary supporting layer and form closed annular inner supporting structures along the contour line of the inner-layer inverted arch, and the annular inner supporting structures are connected into a whole through concrete and form a temporary supporting layer. The inner-layer support is used as a temporary lining to reinforce the outer-layer support, a double-layer support structure is formed in the support section adjacent to the excavation section, deformation, displacement and convergence conditions of the primary support can be effectively controlled before lining construction, and reliability, stability and safety of the primary support are guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of tunnel construction, and more specifically, to a supporting structure for the construction of a tunnel underpass. Background Art

[0002] At present, the New Austrian Tunneling Method (NATM) is widely used in tunnel construction. It mainly uses a combination of anchor rods, steel arch frames and shotcrete as the main support means to reinforce the surrounding rock. It fully utilizes the self-bearing capacity of the surrounding rock and the spatial constraint of the excavation face, and can timely restrain the relaxation and deformation of the surrounding rock. Combined with conventional surrounding rock and support monitoring and measurement technology, the safe step distance between the excavation face and the lining is determined according to relevant industry standards and technical requirements, and lining is carried out in a timely manner.

[0003] However, when constructing tunnels passing under important structures (such as expressways and national highways), the vertical load borne by the tunnel arch increases significantly. Considering the soil side pressure after tunnel excavation and the long time that the initial support is subjected to stress alone, the conventional single-layer support structure cannot guarantee the safety during tunnel construction. There are problems such as slow construction progress, lining failure to keep up with the initial support, and abnormal monitoring data within the excavation face and lining safety step distance. Especially for loess tunnels with shallow burial depth and poor surrounding rock stability, the traditional anchor spraying support method cannot effectively prevent the deformation of the initial support structure, peripheral displacement, arch settlement, surface settlement and other problems.

[0004] In order to solve the above problems, it is necessary to design a support structure for the construction of tunnel underpass structures to improve the reliability, stability and safety of the tunnel initial support. Summary of the Invention

[0005] The purpose of the utility model is to provide a support structure for the construction of tunnel underpass structures, which adopts the inner layer support as temporary lining to reinforce the outer layer support, and forms a double-layer initial support structure in the support section adjacent to the excavation section. It can effectively control the deformation, displacement and convergence of the initial support before lining construction, and ensure the reliability, stability and safety of the initial support.

[0006] In order to achieve these purposes and other advantages according to the utility model, a support structure for the construction of a tunnel under a structure is provided, wherein the excavated tunnel area is divided into an excavation section, a support section, and a lining section in sequence along the length direction with the excavation face as the starting point, and the support structure comprises:

[0007] The outer support comprises a plurality of outer arch frames spaced apart along the length of the tunnel in the excavated tunnel area; a plurality of outer inverted arches corresponding to the plurality of outer arch frames, wherein each outer inverted arch and the corresponding outer arch frame form a closed annular outer support structure along the tunnel section contour line, and adjacent annular outer support structures are connected by concrete to form an initial support layer;

[0008] The inner layer support includes a plurality of inner layer arch frames, which are arranged at intervals in the support section along the length direction of the tunnel; a plurality of inner layer inverted arches, which are arranged in a one-to-one correspondence with the plurality of inner layer arch frames, and any inner layer inverted arch and the corresponding inner layer arch frame are arranged on the inner side of the initial support layer and form a closed annular inner support structure along its contour line, and adjacent annular inner support structures are connected as a whole by concrete to form a temporary support layer.

[0009] Preferably, in the support structure for the construction of the tunnel underpass structure, the front end of the support section is spaced a set distance from the tunnel excavation surface, and when a three-step construction structure is formed in the excavation section, the tunnel excavation surface is the lower step excavation surface.

[0010] Preferably, the support structure used for the construction of tunnel underpass structures, when a three-step construction structure is formed in the excavation section, each outer arch within the upper step and the middle step is a temporary bottom beam, which is supported on the corresponding step and fixedly connected to the bottom end of the corresponding outer arch frame.

[0011] Preferably, in the support structure used for the construction of tunnel underpass structures, when a three-step construction structure is formed in the excavation section, the outer arch frame within each step is fixed to the arch foot of the current step by a locking anchor rod, and the outer arch frames in the remaining construction sections are provided with system anchor rods arranged in a plum blossom shape on the outside of the corresponding construction section.

[0012] Preferably, in the support structure for the construction of tunnel underpass structures, the inner arch frames and the outer arch frames are arranged alternately and spaced apart in the length direction of the tunnel, and any inner arch frame is located between two adjacent outer arch frames.

[0013] Preferably, in the support structure for the construction of the tunnel underpass structure, adjacent outer arch frames and adjacent inner arch frames are fixedly connected by connecting steel bars.

[0014] Preferably, in the support structure for the construction of tunnel underpass structures, the two ends of the outer inverted arch are fixedly connected to the bottom ends of the corresponding outer arch frames by steel plates and bolts, and the two ends of the inner inverted arch are fixedly connected to the bottom ends of the corresponding inner arch frames by steel plates and bolts.

[0015] The utility model has at least the following beneficial effects:

[0016] 1. The utility model is different from the traditional single-layer anchor-sprayed support structure. It adopts the inner arch frame and the inner inverted arch to form a closed annular inner support structure inside the original initial support layer. Structural concrete and shotcrete are applied between multiple annular inner support structures to reinforce the initial support layer as a temporary lining. The outer support layer and the inner support layer constitute a force-bearing whole. A double-layer initial support structure is formed in the support section adjacent to the excavation section, ensuring that the support structure has a certain strength, rigidity and anti-convergence ability, effectively resisting rock stress, and can effectively control the deformation, displacement and convergence of the initial support before the lining is constructed, thereby ensuring the reliability, stability and safety of the initial support.

[0017] 2. The utility model adopts a temporary bottom beam as a temporary inverted arch structure for the construction of the upper and middle steps to ensure the closure and support stability of the annular outer support structure. In the absence of a complete support surface, it can better resist the clearance convergence deformation and further ensure the support stability of the excavation section.

[0018] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the front elevation structure of a support structure for the construction of a tunnel underpass according to one embodiment of the present utility model;

[0020] Figure 2 It is a side elevation diagram of the support structure used for the construction of the tunnel underpass structure described in the above embodiment.

[0021] Description of reference numerals:

[0022] 1. Outer support; 11. Outer arch frame; 12. Outer invert; 13. Temporary bottom beam; 2. Inner support; 21. Inner arch frame; 22. Inner invert; 3. System anchor; 4. Excavation section; 5. Support section; 6. Lining section; 71. Upper step excavation surface; 72. Middle step excavation surface; 73. Lower step excavation surface; 8. Invert; 9. Invert trestle; 10. Tunnel bottom concrete. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0024] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "horizontal", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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 to the present invention.

[0025] like Figure 1-2 As shown, the utility model provides a support structure for the construction of a tunnel under a structure. The excavated tunnel area is divided into an excavation section 4, a support section 5 and a lining section 6 in the longitudinal direction with the excavation surface as the starting point. The support structure includes:

[0026] The outer support 1 includes a plurality of outer arches 11 spaced apart along the length of the tunnel within the excavated tunnel area; a plurality of outer inverted arches 12 corresponding to the plurality of outer arches 11, wherein each outer inverted arch 12 and the corresponding outer arch 11 form a closed annular outer support structure along the tunnel cross-section contour line, and adjacent annular outer support structures are connected by concrete to form an initial support layer;

[0027] The inner layer support 2 includes a plurality of inner layer arches 21, which are arranged at intervals in the support section 5 along the length direction of the tunnel; a plurality of inner layer inverted arches 22, which are arranged in a one-to-one correspondence with the plurality of inner layer arches 21. Any inner layer inverted arch 22 and the corresponding inner layer arch 21 are arranged on the inner side of the initial support layer and form a closed annular inner support structure along its contour line. Adjacent annular inner support structures are connected as a whole by concrete to form a temporary support layer.

[0028] In the above technical solution, three construction sections (excavation section 4, support section 5, and lining section 6) are arranged continuously along the length of the tunnel. The boundary between adjacent construction sections is determined by the construction progress. Excavation section 4 is the construction area still in the tunneling stage; lining section 6 is the construction area where support construction has been completed. This area is separated from excavation section 4 by a certain distance. The support and surrounding rock structures are relatively stable, and subsequent lining construction work can begin. Support section 5 is the transitional construction area between excavation section 4 and lining section 6. This solution mainly improves and strengthens the support structure in this transitional construction area. Specifically, each outer arch frame 11 and inner arch frame 21 are steel arch frames. The outer layer support 1 adopts a conventional primary support structure, the outer layer arch frame 11 is adapted to the contour shape of the surrounding rock at the corresponding construction section, and the outer layer inverted arch 12 is an inverted arch support, which is adapted to the contour shape of the ground at the construction section, so that it can be connected with the corresponding outer layer arch frame 11 to form a closed annular external support structure, and structural concrete is filled between adjacent outer layer inverted arches 12 (and the ground), and sprayed concrete is filled between adjacent outer layer arch frames 11 (and the surrounding rock). Multiple outer layer inverted arches 12 can be connected with the multiple outer layer arch frames 11 to form an integrated annular support layer, that is, the initial support layer. The structure of the inner layer support 2 is similar to that of the outer layer support 1. The inner layer inverted arch 22 also adopts an inverted arch bracket, which is connected with the inner layer arch frame 21 to form a closed annular inner support structure, which is fitted on the inner side wall of the initial support layer. Structural concrete is filled between adjacent inner layer inverted arches 22 (and the initial support layer), and sprayed concrete is filled between adjacent inner layer arch frames 21 (and the initial support layer). Multiple inner layer inverted arches 22 can be connected with the multiple inner layer arch frames 21 to form an integrated annular support layer, that is, the temporary support layer. The above-mentioned inner support is set in the support section serving as the transition construction area, and can be used as a temporary lining to reinforce the initial support layer. The outer support and the inner support constitute a force-bearing whole, forming a double-layer initial support structure in the support section used for transition. This ensures that the support structure in the construction area where the surrounding rock structure is relatively unstable and the support pressure is relatively high has sufficient strength, rigidity, and anti-convergence ability, thereby effectively resisting rock stress and being able to effectively control the deformation, displacement, and convergence of the initial support before the lining is constructed, ensuring the reliability, stability, and safety of the initial support. In addition, the inner support is constructed immediately after the outer support is formed into a ring, ensuring the distance between the inner and outer supports, reducing the time the outer support is subjected to stress alone, and further improving the support stability of the overall tunnel support structure.

[0029] As construction progresses, the excavation face moves forward, and the positions of excavation section 4 and support section 5 change (move forward). Lining section 6 is extended in the construction direction based on the previous lining section, that is, the original support section position is transformed into the construction range of the lining section. At this time, the temporary support layer needs to be removed and the formal lining structure needs to be constructed (including constructing an invert arch 8 on the initial support layer and filling the tunnel bottom concrete 10, constructing the arch wall lining, etc.); after the invert arch construction of the lining structure is completed, the invert arch trestle 9 is moved forward to the new support section position to facilitate the next round of invert arch construction. It is worth noting that for the spraying and mixing work carried out after the above-mentioned arch frames and the corresponding invert arches are installed and connected and accepted, the sprayed concrete surface should be flat, without cracks, looseness, shedding, leakage, exposed reinforcement, or hollows. The gap between the sprayed concrete and the rock surface should be dense and there should be no cavities.

[0030] In this utility model, the interaction between the tunnel surrounding rock and the support structure continues until a balance is reached between the resistance provided by the support and the surrounding rock stress, thereby forming a mechanically stable tunnel structure. This support structure is simple, easy to install, and essentially aligns with conventional support processes. The construction process is unaffected by the working surface. After formation, it significantly limits the displacement and convergence of the tunnel surrounding rock and tunnel structure, effectively ensuring construction safety and the quality of the results, and has promising application prospects.

[0031] In another technical solution, the support structure for the construction of the tunnel underpass structure is such that the front end of the support section 5 is spaced a set distance from the tunnel excavation surface. When a three-step construction structure is formed in the excavation section, the tunnel excavation surface is the lower step excavation surface 73. In this embodiment, the excavation section 4 is constructed using the step method to form a three-step construction structure. Figure 2 The three-step structure shown here consists of an upper step, a middle step, and a lower step. The construction section at the front end of the upper step is the upper step excavation surface 71, the construction section at the front end of the middle step is the middle step excavation surface 72, and the construction section at the front end of the lower step is the lower step excavation surface 73. A certain distance (typically 2-3 meters) is left between the front end of support segment 5 and lower step excavation surface 73 to prevent interference or impact between excavation construction and inner support construction. Excavation section 4 is the construction area between upper step excavation surface 71 and the front end of support segment 5. The length of the support section can be determined based on a comprehensive consideration of tunnel design parameters and actual stress conditions, and can be selected to be 17-18 meters. The excavation distance (length) between the middle step and upper step can be controlled within 1-2 meters.

[0032] In another technical solution, the support structure for the construction of tunnel underpass structures, when a three-step construction structure is formed in the excavation section, each outer arch within the upper step and the middle step is a temporary bottom beam 13, which is supported on the corresponding step and fixedly connected to the bottom end of the corresponding outer arch frame.

[0033] In the above technical solution, after the upper and middle steps are excavated and supported with outer supports, a temporary bottom beam 13 is installed at the arch foot as a temporary inverted arch. Together with the outer arch frame 11, this forms a closed structure to resist headroom convergence deformation. I-beams can be used for the temporary bottom beam 13. The temporary inverted arch can be removed only when the lower step construction reaches the temporary inverted arch position. After the lower step excavation and support are completed, the permanent inverted arch (outer inverted arch) is constructed. After the ring is closed, concrete is poured to complete the outer support construction. Each outer arch frame 11 within the upper and middle steps must also be installed to accommodate the current tunnel cross-section (construction cross-section) structure. This means that it is not a complete outer arch frame structure. In this case, any outer arch frame and the corresponding temporary bottom beam can still form a closed ring-shaped external support structure along the tunnel cross-section contour. Adjacent outer arch frames are connected by sprayed concrete. However, the outer inverted arches (temporary bottom beams) within this area (upper and middle steps) are not filled with structural concrete to allow for rapid removal when the steps continue to excavate to the temporary bottom beam position.

[0034] In actual construction, after the construction of the outer arch frame of each step in the excavation section is completed, a temporary bottom beam is constructed as a temporary inverted arch to cooperate with the outer arch frame to form a closed support structure. When the construction of the lower step reaches the temporary inverted arch position, the temporary bottom beam is removed and the outer inverted arch is constructed as a permanent inverted arch to make the outer support complete into a ring. Then the inner support is constructed immediately, which ensures the distance between the inner support and the excavation section (excavation surface) and reduces the time that the outer support is supported and stressed alone.

[0035] In another technical solution, the support structure for tunnel underpass construction employs a three-step construction structure within the excavation section 4. The outer arch frame 11 within each step is secured to the foot of the current step using locking anchors. The outer arch frames 11 within the remaining construction sections (support section 5 and lining section 6) are equipped with system anchors 3 arranged in a plum blossom pattern on the outside of the corresponding construction sections. Specifically, different anchoring structures are employed for different outer arch frame configurations. For a structurally complete annular outer support structure, system anchors 3 are used as permanent anchors. For annular outer support structures that are not yet fully formed due to the constraints of the step structure, locking anchors are used as temporary anchors. These anchoring measures are all designed to ensure the structural strength and stability of the outer arch frame supporting the tunnel surrounding rock.

[0036] In another technical solution, the support structure for the construction of tunnel underpass structures, the inner arch frame 21 and the outer arch frame 11 are staggered and spaced apart in the length direction of the tunnel, and any inner arch frame 21 is located between two adjacent outer arch frames 11, thereby optimizing the support force structure and further strengthening the supporting stability of the double-layer support structure on the surrounding rock of the support section.

[0037] In another technical solution, the support structure for tunnel underpass construction employs interconnecting steel bars to securely connect adjacent outer arches 11 and adjacent inner arches 21, allowing the multiple arches to form a single, force-bearing entity, improving their stability. Furthermore, the outer supports within different construction sections are not completed within the same construction cycle. For construction sections requiring new outer supports, the outer arches can be spliced ​​with interconnecting steel bars from the previous cycle (previous construction section). This allows the outer supports of each section to be connected to form a force-bearing entity, improving the integrity of the initial support.

[0038] In another technical solution, the support structure for tunnel underpass construction comprises the outer inverted arches 12 having their ends fixedly connected to the bottom ends of their corresponding outer arch supports 11 using steel plates and bolts, while the inner inverted arches 22 having their ends fixedly connected to the bottom ends of their corresponding inner arch supports 21 using steel plates and bolts. In this embodiment, each arch support is connected to its corresponding inverted arch using 15mm steel plates and AM20 high-strength bolts to ensure connection quality.

[0039] In addition, any inner arch frame adopts a segmented assembly structure, which is divided into an upper arch frame, a middle arch frame and a lower arch frame (corresponding to the steps) from top to bottom according to the installation height. The inner arch is fixedly connected to the bottom end of the lower arch frame of the corresponding inner arch frame and is pre-embedded in the structural concrete at the bottom of the temporary support layer. During the inner support construction, the inner inverted arch (arch frame) is first positioned and installed, and then the corresponding lower arch frame of the inner arch frame is installed at the arch foot, and the bottom end of the lower arch frame is connected to the two ends of the inner inverted arch using steel plates and high-strength bolts. Then, the bottom structural concrete of the inner support is poured. At this time, some sections of the above-mentioned inner inverted arch and lower arch frame are embedded in the structural concrete as the basis for the construction of the inner arch frame; the unembedded sections of the lower arch frame are sprayed with C25 concrete to seal them. When the structural concrete strength reaches 75%, the concrete pouring formwork of the inner inverted arch is removed, and the middle arch frame and upper arch frame are constructed in sequence based on the lower arch frame. After each inner arch frame is sprayed and sealed, the inner support construction is completed.

[0040] Taking the construction of Xizhuang No. 1 Tunnel on the Yangquan Coal Group's Pingshu Railway dedicated line as an example, the support structure of this utility model has been applied to the construction of Xizhuang No. 1 Tunnel under the Taijiu Expressway and National Highway 307. After the support was completed, monitoring and measurement were carried out. The measured tunnel monitoring data was stable, with a low deformation rate and cumulative deformation. This shows that the support structure of this utility model can effectively control the support deformation problems that occur when loess tunnels pass under important structures, ensuring construction safety and quality.

[0041] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with this field, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A support structure for the construction of a tunnel underpass, characterized in that: The excavated tunnel area is divided into an excavation section, a support section, and a lining section along the length direction, starting from the excavation face. The support structure includes: The outer support comprises a plurality of outer arch frames spaced apart along the length of the tunnel in the excavated tunnel area; a plurality of outer inverted arches corresponding to the plurality of outer arch frames, wherein each outer inverted arch and the corresponding outer arch frame form a closed annular outer support structure along the tunnel section contour line, and adjacent annular outer support structures are connected by concrete to form an initial support layer; The inner layer support includes a plurality of inner layer arch frames, which are arranged at intervals in the support section along the length direction of the tunnel; a plurality of inner layer inverted arches, which are arranged in a one-to-one correspondence with the plurality of inner layer arch frames, and any inner layer inverted arch and the corresponding inner layer arch frame are arranged on the inner side of the initial support layer and form a closed annular inner support structure along its contour line, and adjacent annular inner support structures are connected as a whole by concrete to form a temporary support layer.

2. The support structure for tunnel underpass construction according to claim 1, characterized in that: The front end of the support section is spaced a set distance from the tunnel excavation surface. When a three-step construction structure is formed in the excavation section, the tunnel excavation surface is the lower step excavation surface.

3. The support structure for tunnel underpass construction according to claim 1, characterized in that: When a three-step construction structure is formed in the excavation section, each outer arch within the upper step and the middle step serves as a temporary bottom beam, which is supported on the corresponding step and fixedly connected to the bottom end of the corresponding outer arch frame.

4. The support structure for tunnel underpass construction according to claim 1, characterized in that: When a three-step construction structure is formed in the excavation section, the outer arch frame within each step is fixed to the arch foot of the current step by a locking anchor rod, and the outer arch frames in the remaining construction sections are provided with a plum blossom-shaped system anchor rod on the outside of the corresponding construction section.

5. The support structure for tunnel underpass construction according to claim 1, characterized in that: The inner arch frames and the outer arch frames are arranged alternately and at intervals in the length direction of the tunnel, and any inner arch frame is located between two adjacent outer arch frames.

6. The support structure for tunnel underpass construction according to claim 1, characterized in that: Adjacent outer arch frames and adjacent inner arch frames are fixedly connected by connecting steel bars.

7. The support structure for tunnel underpass construction according to claim 1, characterized in that: The two ends of the outer inverted arch are fixedly connected to the bottom end of the corresponding outer arch frame through steel plates and bolts, and the two ends of the inner inverted arch are fixedly connected to the bottom end of the corresponding inner arch frame through steel plates and bolts.

Images