Inclined shaft tunnel opening type tunnel portal excavation arrangement structure and construction method

Abstract

The invention relates to an inclined shaft tunnel opening type tunnel portal excavation arrangement structure and a construction method.The arrangement structure comprises an upward slope and a rigid built-in soil retaining structure, the upward slope is arranged at an inclined shaft tunnel opening in the axis direction of the tunnel, and tunnel portal wall excavation embedded steps are formed in the range of covering layer side slopes on the two sides of the inclined shaft tunnel opening in a step-by-step excavation mode; a tunnel door wall bottom cushion layer is arranged at the bottom of the wall excavation embedded step, a step type tunnel door wall is poured on the tunnel door wall bottom cushion layer, the step type tunnel door wall is embedded into the upward slope, and a rigid embedded soil retaining structure is formed; a concrete cover arch is arranged at the top of an inclined shaft opening, the concrete cover arch extends inwards and is in transition connection with an inclined shaft open cut tunnel lining, a steel arch frame is arranged between the concrete cover arch and the inclined shaft open cut tunnel lining, and the whole structure is closed through longitudinal connecting ribs of the steel arch frame. Compared with a common bamboo cutting type tunnel portal and a wing wall type tunnel portal, the tunnel portal walls of the notch type tunnel portal are embedded into the covering layer slopes on the two sides, and the soil retaining capacity of the covering layer tunnel portal walls and the stability of the slope entering the tunnel portal are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a structure and construction method for excavating a portal-type tunnel opening in a deep overburden layer. Background Technology

[0002] In the construction of inclined shaft tunnels under deep overburden conditions, the safety and rationality of the portal structure directly affect key construction procedures such as portal slope stability, drainage, and internal structural connections. In site conditions where the overburden consists of loose deposits, clay layers, or gravel interlayers, there are often problems such as concentrated pore water pressure, increased permeability during the rainy season, and softening and deformation at the toe of the slope, making the portal area structure more susceptible to landslides, erosion, or instability.

[0003] In tunnel engineering, inclined shaft portals often employ either a scissor-cut or end-wall structure. Scissor-cut portals are suitable for areas with open terrain, thin overburden, or high slope stability. However, with thicker overburden, the slope angle is limited, the slope length increases, and a cantilever structure forms between the slope and the portal wall, making stability difficult to guarantee. End-wall portals typically use short-section rigid retaining walls to directly seal the portal edge, offering a simple and clear construction organization. However, due to the high wall rigidity and limited embedment depth, it is difficult to effectively coordinate with the deformation differences of the overburden slope, easily leading to concentrated stress or pore pressure accumulation behind the wall, creating structural weak points. Under deep overburden conditions, the use of traditional scissor-cut or end-wall portal structures generally suffers from unreasonable structural stress, poor drainage, large slope disturbance, and tight front-field layout, making it difficult to meet the diverse needs of large inclined shaft projects, such as equipment hoisting, personnel evacuation, pipeline laying, and drainage connection. Summary of the Invention

[0004] To address the above problems, this invention provides a portal excavation layout structure and construction method for inclined shaft tunnels in deep overburden layers. This structure enhances the portal wall's embedment capacity, improves the drainage system, optimizes the portal layout conditions, reduces construction difficulty, and effectively overcomes existing problems such as unstable support, poor drainage, and limited layout space in inclined shaft tunnel portal layouts in deep overburden layers, ensuring tunnel entry safety and construction efficiency.

[0005] The technical solution adopted in this invention is: a portal excavation layout structure for an inclined shaft tunnel, characterized by: including a slope and a rigid retaining structure; the slope is set along the tunnel axis at the inclined shaft entrance, and the slopes of the overburden layer on both sides of the slope are directionally excavated to form a structural portal opening; within the range of the overburden slopes on both sides of the inclined shaft entrance, a portal wall is excavated and embedded in steps as the foundation for the embedded portal wall; a portal wall bottom cushion is set at the bottom of the wall excavation and embedded in the steps, and the stepped portal wall is poured from bottom to top on the portal wall bottom cushion, so that the stepped portal wall is embedded into the slope of the overburden layer step by step to form a rigid retaining structure; a concrete arch is set at the top of the inclined shaft entrance, the concrete arch extends inward to connect and transition with the lining of the inclined shaft open passage, and a steel arch frame is provided between the concrete arch frame and the lining of the inclined shaft open passage, and the overall structure is closed by longitudinal connecting bars of the steel arch frame.

[0006] Preferably, the top area of ​​the concrete arch and inclined shaft lining is backfilled with stone chips or soil and stone materials in layers to form a compacted backfill body.

[0007] Preferably, a drainage ditch and a concealed pipe system are pre-installed inside the compacted backfill.

[0008] Preferably, a drainage ditch is provided on the back of the stepped portal wall, and the drainage ditch on the top of the portal is connected to the drainage ditch on the side slope of the cover layer to form a drainage system.

[0009] Preferably, a long pipe shed and a pipe shed guide pipe are installed at the front edge of the inclined shaft entrance as a steel arch support system; the starting point of the long pipe shed is located at the front edge of the stepped portal wall, and the ending point extends into the interior of the inclined shaft open section.

[0010] As a preferred option, as the tunneling enters the stable surrounding rock area, the long pipe roof support is gradually phased out and replaced with small pipe support or anchor bolt weakened support, thus realizing the construction transition from advanced active support to structural stability passive support.

[0011] Preferably, the lower part of the steel arch frame is equipped with locking anchor rods to fix it to the bottom of the inclined shaft lining.

[0012] As a preferred option, it is suitable for inclined shaft tunnels under conditions of deep overburden.

[0013] As a preferred option, the space created by the opening provides a forward area for large construction equipment, transport vehicles, and hoisting platforms.

[0014] A construction method for the above-mentioned inclined shaft tunnel portal excavation layout structure is characterized by the following steps: S1. Measure and set out the tunnel axis and the slope range of the inclined shaft. Cut the slope of the overburden layer in layers according to the design elevation, excavate to form the opening area of ​​the tunnel entrance, and excavate in stages to form the tunnel portal wall and embed the steps. S2. Construct the bottom cushion layer of the portal wall on the steps embedded in the excavation of the portal wall, and pour the stepped portal wall in sequence, embedding it into the slope structure from bottom to top to complete the construction of the portal walls on both sides. S3. A concrete arch is installed at the top of the inclined shaft entrance. The concrete arch is connected to the stepped portal wall and extends to the lining section of the inclined shaft. A steel arch frame is installed inside and longitudinal connecting bars are configured to form a continuous closed structure. S4. Backfill the top area of ​​the concrete arch and inclined shaft lining with stone chips in layers. During the backfilling process, pre-embed drainage pipes and set up a tunnel top drainage ditch to ensure unobstructed drainage in the tunnel top area. S5. A drainage ditch is set on the back of the stepped portal wall. The drainage ditch on the top of the portal connects to the drainage ditch on the left and right sides of the cover layer, forming a connected drainage network of portal back water, slope seepage and slope drainage system. S6. A long pipe shed and guide steel pipe are set at the front edge of the inclined shaft entrance as a means of support for entering the tunnel. The length of the long pipe shed is controlled within the lining section of the inclined shaft open tunnel. After the support is completed, it is connected to the lining of the inclined shaft open tunnel. S7. According to the changes in surrounding rock conditions, the support structure is gradually weakened in stable strata, and the pipe roof is replaced with small pipes and anchor bolts to complete the transition support structure closure between the inclined shaft entrance and the inclined shaft open tunnel lining. S8. After the lining section of the inclined shaft and the overall opening of the inclined shaft are completed, the lining structure will be constructed according to the design standards to form a stable portal sealing system.

[0015] The beneficial effects achieved by this invention are as follows: Compared with the prior art, this invention has the following advantages: 1. Compared with the common bamboo-cutting type portal and wing wall type portal, the portal wall of the gap type portal is embedded in the slope of the overburden layer on both sides, which effectively improves the soil retention capacity of the portal wall of the overburden layer and the stability of the entrance slope; at the same time, the space formed by the portal wall, the gap and the arch helps the backfilling and compaction of soil and rock materials on the top of the tunnel. 2. Inclined shaft entrances often require the installation of hoisting equipment, tracks, slag collection platforms, control rooms, and necessary ventilation, power supply, and water supply equipment. Therefore, sufficient space must be reserved along the axis of the entrance. Taking a certain project as an example, to accommodate the layout requirements of the inclined shaft hoisting equipment, the pre-planned length of the site before the inclined shaft entrance is approximately 80m to 100m. Compared to the common bamboo-cutting type and wing-wall type entrances, the notch-type entrance layout is more adaptable to the site planning requirements of the inclined shaft entrance and is more conducive to slag removal from the inclined shaft. 3. The gap-type portal connects the portal wall drainage ditch and the horse path drainage ditch together, so that the water accumulated behind the portal wall can be quickly discharged to the outside of the natural slope through the horse paths on both sides, forming a complete drainage system. 4. When using a wing-wall type portal for tunnel entry in thick overburden layers, long pipe roofs combined with arched entry are often used. For example, in one project, the pipe roof for tunnel entry in the overburden layer was as long as 20m. When using a gap-type portal, the tunnel entrance can be excavated deeper to increase the slope of the temporary uphill slope on the entrance side. When the temporary uphill slope on the entrance side enters the weakly weathered layer, the advance support measures can be weakened (for example, the pipe roof can be adjusted to advance small pipes or lock anchors) to reduce the difficulty of tunnel entry. The stability of the uphill slope at the tunnel entrance is improved after the portal wall is completed and the tunnel roof is backfilled. Attached Figure Description

[0016] Figure 1 This is a three-dimensional schematic diagram of the inclined shaft opening excavation of the present invention; Figure 2 This is a three-dimensional layout diagram of the inclined shaft entrance of the present invention; Figure 3 This is a schematic diagram of the layout of the inclined shaft entrance wall of the present invention; Figure 4 This is a schematic diagram of the backfilling at the top of the inclined shaft opening according to the present invention; Figure 5 This is a schematic diagram of the longitudinal section of the opening of the present invention; Figure 6 This is a schematic diagram of the tunnel entry method of the present invention; The components include: 1. Upward slope; 2. Inclined shaft entrance; 3. Excavation and embedding of steps in the portal wall; 4. Walkway drainage ditch; 5. Top drainage ditch; 6. Stepped portal wall; 7. Concrete arch; 8. Inclined shaft lining; 9. Long pipe shed; 10. Compacted backfill; 11. Bottom bedding layer of portal wall; 12. Steel arch frame; 13. Longitudinal connecting bars of steel arch frame; 14. Pipe shed guide pipe. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1-6 As shown, the present invention discloses an excavation layout structure for a sloping shaft tunnel portal, suitable for sloping shaft tunnel projects under deep overburden conditions, employing a portal layout structure. This layout structure includes a slope 1, a rigid retaining structure, a compacted backfill 10, a steel arch support system, and a drainage system.

[0019] Based on the design axis and elevation control line, the slope 1 area at the entrance of the inclined shaft is determined. This area is then excavated to create a stable slope 1 with a suitable gradient. Slope 1 is positioned along the tunnel axis at the entrance 2 of the inclined shaft. The overburden slopes on both sides of slope 1 are directionally excavated to form structural openings. These openings provide ample space for large construction equipment, transport vehicles, and hoisting platforms, facilitating coordinated and efficient construction both inside and outside the tunnel.

[0020] Within the slope range of the overburden layer on both sides of the inclined shaft entrance 2, the portal wall is excavated in stages to form the embedded steps 3, which serve as the foundation for the embedded portal wall 6 and have good anti-sliding stability. A bottom cushion layer 11 is set at the bottom of the embedded steps 3 (to distribute the vertical load and improve the bottom anti-settlement capacity), and the stepped portal wall 6 is poured from bottom to top on the bottom cushion layer 11, so that the stepped portal wall 6 is embedded into the slope 1 of the overburden layer in stages, forming a rigid embedded retaining structure and improving the anti-sliding stability of the portal.

[0021] A concrete arch 7 is installed at the top of the inclined shaft opening 2. The concrete arch 7 extends inward to connect and transition with the inclined shaft lining 8. A steel arch frame 12 is installed between the concrete arch 7 and the inclined shaft lining 8. The overall structure is enclosed by longitudinal connecting bars 13 of the steel arch frame. The lower part of the steel arch frame 12 is equipped with locking anchor rods to fix it to the bottom position of the inclined shaft lining 8, which improves the overall stress coordination and support capacity of the structure.

[0022] In the top area of ​​the concrete arch 7 and the inclined shaft open tunnel lining 8, stone chips or soil and rock materials are backfilled in layers to form a compacted backfill body 10. The top compacted backfill body 10 and the top arch structure together form a stable overlying system for the tunnel entrance, which has sealing and anti-disturbance performance. At the same time, a tunnel top drainage ditch 5 and a culvert system are pre-set inside the compacted backfill body 10 to effectively guide the water flow around the top arch and prevent the structural instability risk caused by water accumulation above the top arch.

[0023] A drainage ditch 5 is set on the back of the tunnel portal wall 6 and connected to the walkway drainage ditch 4 set on the slope of the cover layer on both sides. This allows the water accumulated on the back of the tunnel portal wall to be quickly discharged to the outside of the natural slope through the walkways on both sides, forming an integrated drainage system for the back of the tunnel portal water, slope seepage water and slope drainage, ensuring that the back of the tunnel portal water, the top of the tunnel water and the seepage water of the cover layer are discharged smoothly.

[0024] To ensure the safety of the front structure during the initial excavation stage, a long pipe roof 9 and a pipe roof guide pipe 14 are installed at the front edge of the inclined shaft entrance 2 as a steel arch support system. The starting point of the long pipe roof 9 is located at the front edge of the stepped portal wall 6, and the ending point extends into the interior of the open section of the inclined shaft. The pipe roof guide pipe 14 is installed in front of the long pipe roof 9 to accurately control the advancement direction and installation accuracy of the long pipe roof 9 during construction. As the excavation enters the stable surrounding rock area, the support of the long pipe roof 9 is gradually removed and replaced by small pipe support or weakened support forms such as anchor bolts, realizing the construction transition from advanced active support to passive support for structural stability.

[0025] The inclined shaft tunnel portal excavation layout structure of the present invention has good slope stability, structural continuity, construction adaptability and drainage, and is suitable for the safe entry requirements of inclined shaft tunnels under deep overburden conditions.

[0026] The present invention discloses a construction method for an inclined shaft tunnel portal excavation layout structure, characterized by comprising the following steps: S1. Measure and set out the tunnel axis and the inclined shaft slope 1 range, cut the slope of the overburden layer in layers according to the design elevation, excavate to form the opening area of ​​the tunnel entrance, and excavate in stages to form the tunnel portal wall and embed the steps 3. S2. Construct the bottom cushion layer 11 of the portal wall on the step 3 embedded in the portal wall, and pour the stepped portal wall 6 in sequence, embedding it into the slope structure from bottom to top to complete the construction of the portal walls on both sides. S3. A concrete arch 7 is installed at the top of the inclined shaft opening 2. The concrete arch 7 is connected to the stepped doorway wall 6 and extends to the lining section 8 of the inclined shaft. A steel arch frame 12 is installed inside and a longitudinal connecting bar 13 of the steel arch frame is configured to form a continuous closed structure. S4. Backfill the top area of ​​the concrete arch 7 and the inclined shaft open tunnel lining 8 with stone chips in layers. During the backfilling process, pre-embed drainage pipes and set up drainage ditches 5 at the top to ensure unobstructed drainage in the tunnel top area. S5. Drainage ditch 5 is set on the back of the stepped portal wall 6. Drainage ditch 5 connects to the horse path drainage ditch 4 on the left and right sides of the cover layer, forming a connected drainage network of portal back water, slope seepage and slope drainage system. S6. A long pipe shed 9 and a guide steel pipe 14 are set at the front edge of the inclined shaft entrance 2 as a means of entering the tunnel. The length of the long pipe shed 9 is controlled inside the lining section 8 of the inclined shaft open tunnel. After the support is completed, it is connected to the lining section 8 of the inclined shaft open tunnel. S7. According to the changes in surrounding rock conditions, the support structure is gradually weakened in the stable stratum, and the pipe roof 8 is replaced with small pipes and anchor bolts to complete the transition support structure closure between the inclined shaft entrance 2 and the inclined shaft open tunnel lining 8. S8. After the completion of the lining of the inclined shaft open tunnel in sections 8 and the overall completion of the inclined shaft entrance 2, the lining structure construction shall be carried out in accordance with the design standards to form a stable tunnel entrance sealing system.

[0027] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims.

[0028] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A portal excavation layout structure for inclined shaft tunnels, characterized in that: The structure includes an inverted slope and a rigid retaining structure. The inverted slope is set along the tunnel axis at the entrance of the inclined shaft. The slopes of the overburden layer on both sides of the inverted slope are directionally excavated to form a structural opening. Within the range of the overburden slopes on both sides of the inclined shaft entrance, a stepped portal wall is excavated and embedded, serving as the foundation for the stepped portal wall. A bottom cushion layer is set at the bottom of the embedded steps, and the stepped portal wall is poured from bottom to top on the bottom cushion layer, so that the stepped portal wall is gradually embedded into the inverted slope of the overburden layer, forming a rigid retaining structure. A concrete arch is set at the top of the inclined shaft entrance. The concrete arch extends inward and connects with the lining of the inclined shaft. A steel arch frame is provided between the concrete arch frame and the lining of the inclined shaft, and the overall structure is enclosed by longitudinal connecting bars of the steel arch frame.

2. The inclined shaft tunnel portal excavation layout structure according to claim 1, characterized in that: In the top area of ​​the concrete arch and inclined shaft lining, stone chips or soil and rock materials are backfilled in layers to form a compacted backfill body.

3. The inclined shaft tunnel portal excavation layout structure according to claim 2, characterized in that: A pre-installed drainage ditch and underground pipe system are installed inside the compacted backfill.

4. The inclined shaft tunnel portal excavation layout structure according to claim 3, characterized in that: A drainage ditch is installed on the back of the stepped portal wall, and the drainage ditch on the top of the portal is connected to the drainage ditch on the slope of the cover layer on both sides to form a drainage system.

5. The inclined shaft tunnel portal excavation layout structure according to claim 1, characterized in that: A long pipe shed and a pipe shed guide pipe are installed at the front edge of the inclined shaft entrance to serve as a steel arch support system; the starting point of the long pipe shed is located at the front edge of the stepped portal wall, and the ending point extends into the interior of the open section of the inclined shaft.

6. The inclined shaft tunnel portal excavation layout structure according to claim 5, characterized in that: As the tunneling enters the stable surrounding rock area, the long pipe roof support is gradually phased out and replaced by small pipe support or anchor bolt weakened support, realizing the construction transition from advanced active support to passive support for structural stability.

7. The inclined shaft tunnel portal excavation layout structure according to claim 1, characterized in that: The lower part of the steel arch frame is equipped with locking anchor rods to fix it to the bottom foot position of the inclined shaft open tunnel lining.

8. The inclined shaft tunnel portal excavation layout structure according to claim 1, characterized in that: Suitable for inclined shaft tunnels under conditions of deep overburden.

9. The inclined shaft tunnel portal excavation layout structure according to claim 1, characterized in that: The opening creates a space for large construction equipment, transport vehicles, and hoisting platforms.

10. A construction method for an inclined shaft tunnel portal excavation layout structure as described in any one of claims 1 to 9, characterized in that: Includes the following steps: S1. Measure and set out the tunnel axis and the inclined shaft slope 1 range, cut the slope of the overburden layer in layers according to the design elevation, excavate to form the opening area of ​​the tunnel entrance, and excavate in stages to form the tunnel portal wall excavation and embedding steps. S2. Construct the bottom cushion layer of the portal wall on the steps embedded in the excavation of the portal wall, and pour the stepped portal wall in sequence, embedding it into the slope structure from bottom to top to complete the construction of the portal walls on both sides. S3. A concrete arch is installed at the top of the inclined shaft entrance. The concrete arch is connected to the stepped portal wall and extends to the lining section of the inclined shaft. A steel arch frame is installed inside and longitudinal connecting bars are configured to form a continuous closed structure. S4. Backfill the top area of ​​the concrete arch and inclined shaft lining with stone chips in layers. During the backfilling process, pre-embed drainage pipes and set up a tunnel top drainage ditch to ensure unobstructed drainage in the tunnel top area. S5. A drainage ditch is set on the back of the stepped portal wall. The drainage ditch on the top of the portal connects to the drainage ditch on the left and right sides of the cover layer, forming a connected drainage network of portal back water, slope seepage and slope drainage system. S6. A long pipe shed and guide steel pipe are set at the front edge of the inclined shaft entrance as a means of support for entering the tunnel. The length of the long pipe shed is controlled within the lining section of the inclined shaft open tunnel. After the support is completed, it is connected to the lining of the inclined shaft open tunnel. S7. According to the changes in surrounding rock conditions, the support structure is gradually weakened in stable strata, and the pipe roof is replaced with small pipes and anchor bolts to complete the transition support structure closure between the inclined shaft entrance and the inclined shaft open tunnel lining. S8. After the lining section of the inclined shaft and the overall opening of the inclined shaft are completed, the lining structure will be constructed according to the design standards to form a stable portal sealing system.

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