A method for excavating and supporting the arch of a tunnel in an inclined rock stratum

Abstract

The application discloses a kind of inclined strata cavern arch excavation support construction methods, it is related to underground engineering excavation support technical field, the method includes: S1, obtains the strata dip angle of inclined strata, and the intersection line of strata level and horizontal plane is determined based on the strata dip angle obtained, construction passage axis is determined based on the intersection line, S2, for construction passage arrangement passage support system;S3, with construction passage as starting point, to middle part of cavern arch middle part extension excavation middle part pilot area;S4, with middle part pilot area as boundary, cavern arch two sides are divided into independent excavation area symmetrically, each side is using preset excavation strategy, and excavation whole course follows symmetric construction, principle of first inside then outside, immediately support after each excavation, and next step is carried out after the deformation stability of previous area step support.This application realizes the safe and efficient construction of inclined broken strata arch by the integrated process of block excavation and collaborative support.

Description

Technical Field

[0001] This application relates to the field of underground engineering excavation and support technology, specifically to a construction method for excavation and support of underground cavern arch structures applicable to steeply inclined rock strata. Background Technology

[0002] As a key structure bearing the pressure of rock strata and groundwater, the arch of an underground cavern has stringent requirements for construction safety and stability. This is especially true when the arch is situated in inclined and fractured rock strata, where construction faces a dual core challenge: On the one hand, the inclined rock strata are controlled by bedding planes. After excavation, the rock blocks are prone to sliding along the bedding planes due to the lack of overall interlocking, resulting in instantaneous slag shedding. This not only affects construction efficiency but may also cause the face of the tunnel to collapse. On the other hand, the inclined rock strata have obvious bias pressure. In traditional full-face excavation or conventional step-by-step excavation methods, the support structures such as shotcrete and steel supports are prone to excessive radial or circumferential deformation due to uneven stress, which leads to the failure of the support system. Repeated reinforcement is required, which greatly increases the construction cost and construction period.

[0003] In existing technologies, methods such as the ring excavation with reserved core soil and the CD method commonly used in tunnel engineering can control excavation disturbance to a certain extent. However, these methods have not been specifically optimized in combination with the arc-shaped stress characteristics of the tunnel arch and the bias pressure effect of the inclined rock strata, resulting in significant technical adaptability defects. At the excavation control level, excessive single advance leads to the concentration of rock strata unloading areas and prolonged exposure time, keeping the risk of instability and fall of broken rock blocks along the bedding plane at a high level. At the support design level, the lack of reinforcement of the constraint structure to address the problems of bedding sliding force and arch foot stress concentration in the inclined rock strata results in insufficient shear bearing capacity and arch foot anchorage strength of the support system, making it difficult to match the complex non-uniformly distributed load of the inclined broken rock strata, which can easily lead to radial deformation or even overall failure of the support structure.

[0004] Therefore, there is an urgent need for a new construction method for excavation and support of the arch of inclined rock caverns to solve the technical bottleneck of excavation of the arch of inclined rock caverns. Summary of the Invention

[0005] In view of this, this application provides a construction method for excavation and support of the arch of an inclined rock stratum cavern, which aims to achieve safe and efficient construction of the inclined fractured rock stratum arch through an integrated process of segmented excavation and coordinated support.

[0006] A method for excavation and support of the arch of an inclined rock cavern includes: S1. Obtain the dip angle of the rock strata, and determine the intersection line between the rock strata bedding plane and the horizontal plane based on the obtained rock strata dip angle. Determine the axis of the construction passage based on the intersection line, wherein the axis of the construction passage is the construction direction of the construction passage and is perpendicular to the intersection line. S2. Arrange a support system for the construction access road; The construction passage support system includes: spraying early-strength concrete to seal the rock surface of the construction passage; laying steel mesh and installing steel arches to form a stable construction passage. S3. Starting from the construction access road, extend the excavation of the central pilot area towards the middle of the tunnel arch. Among them, the central pilot area is excavated in two layers, with the tunnel arch axis as the center. After the top surface of the tunnel arch 1 is excavated in the upper layer, the upper tunnel arch support system is arranged to form a stable working space. The tunnel arch support system includes: after the top surface of the tunnel arch is excavated, early-strength concrete is immediately sprayed to seal the rock surface, steel mesh is laid, steel arch frame is installed, and early-strength concrete is sprayed again to form a stable working space. S4. Taking the central pilot area as the boundary, the two sides of the tunnel arch are symmetrically divided into independent excavation areas. Each side adopts a pre-set excavation strategy, and the entire excavation process follows the principle of symmetrical construction and inside-outside. Support is immediately provided after each excavation step, and the next step is carried out only after the support deformation of the previous step has stabilized. In one possible approach, the preset mining strategy includes: S401: Innermost Excavation and Support: First, excavate the innermost area on one side, then spray concrete initially, lay steel mesh, install steel arch frame, install anchor bolts at the arch foot, and spray concrete again; symmetrically excavate the innermost area on the other side to ensure balanced force on both sides. S402: Central Excavation and Support: After the innermost support on one side is stable, excavate the central area on the same side, spray initial concrete after excavation, lay steel mesh, install steel arch frame, and spray concrete again; excavate the central area on the other side symmetrically at the same time to avoid unilateral pressure. S403: Outermost Excavation and Support: After the middle support on one side is stable, the outermost area on the same side is excavated; after excavation, initial shotcrete is applied, steel mesh is laid, steel arch frame is installed, a locking anchor is installed at the arch foot, and shotcrete is applied again to enhance the stability of the arch edge of the tunnel.

[0007] In one possible configuration, the reinforcing mesh is welded between two steel arch frames. In one possible solution, the anchor bolt is driven into the inclined rock strata from the foot of the steel frame arch at an angle of 30° to 60° with the ground.

[0008] In one possible configuration, the anchor rod has evenly distributed small holes.

[0009] In one possible approach, the "three zones and three steps" refers to dividing the single-sided excavation section radially into three zones: the innermost zone, the middle zone, and the outermost zone. Each zone is then excavated three times according to a preset advance.

[0010] As can be seen from the above technical solution, this application has the following beneficial effects: By accurately understanding the characteristics of rock strata through advanced geological surveys and combining this with the method of constructing construction channels perpendicular to the dip angle of the rock strata, the sliding of inclined rock strata along the strata is suppressed from the source of stress, effectively avoiding the hidden dangers of eccentric pressure deformation in the tunnel. By adopting a step-by-step excavation process of double-layer pilot excavation in the middle and "symmetrical construction, inside-out" on both sides, the disturbance of the surrounding rock during construction is strictly controlled, and a stable working space is formed in advance. At the same time, the construction mode of excavating and protecting simultaneously and immediate sealing and support avoids long-term exposure of rock strata, solving the problems of large disturbance and easy collapse caused by traditional excavation.

[0011] Through a collaborative construction system that seamlessly integrates excavation and support, standardized support operations are simultaneously implemented in each excavation area, including early-strength concrete spraying, steel mesh laying, steel arch frame installation, and anchor bolt fixation. The combined support structure—combining steel arch frames to absorb and offset in-stratum sliding forces, steel mesh reinforcement to enhance the integrity of the sprayed concrete, and anchor bolt fixation to strengthen the arch foot—along with a symmetrical closed-loop support advancement method, systematically transmits rock stress and balances rock stratum bias pressure, achieving high-strength and high-stability load-bearing capacity of the support system. This improves upon the problems of traditional support systems being slow and having weak resistance to bias pressure.

[0012] By adapting to the needs of on-site equipment and personnel through a straight-wall construction access, and optimizing the process flow through central pilot excavation, construction efficiency is significantly improved. The "three-zone, three-step" excavation and support mode, which can dynamically adapt to the rock strata dip angle and rock fragmentation degree, eliminates the need for special construction equipment. Combined with standardized and modular on-demand support layout, it reduces construction complexity and material waste, achieving highly efficient and high-quality construction of the arched structure of the tunnel. It possesses strong on-site adaptability and engineering promotion value. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a longitudinal sectional view of the pre-excavation of the cavern arch provided in an embodiment of this application; Figure 2 Plan view of the arch support of the central pilot area provided in this application embodiment; Figure 3 A longitudinal sectional view of the arch support of the central pilot area provided in this application embodiment; Figure 4 This application provides a zoning diagram of the excavation on both sides for an embodiment of the invention. Figure 5 Plan view of the excavation and support of the inner cavern arch provided in the embodiments of this application; Figure 6 This is a longitudinal sectional view of the excavation and support of the inner cavern arch provided in an embodiment of this application; Figure 7 Plan view of the excavation and support of the central cavern arch provided in this application embodiment; Figure 8 A longitudinal sectional view of the excavation and support of the central cavern arch provided in an embodiment of this application; Figure 9 Plan view of the excavation and support of the outer cavern arch provided in the embodiments of this application; Figure 10 This is a longitudinal sectional view of the excavation and support of the outer cavern arch provided in an embodiment of this application; Figure 11 A flowchart illustrating a construction method for excavation and support of the arch of an inclined rock cavern, as provided in this application embodiment; Figure label: 1—Cave arch; 2—Inclined rock strata; 3—Construction access; 4—Steel arch frame; 5—Steel arch frame connecting plate; 6—Reinforcing mesh; 7—Anchor bolt. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 11 As shown, a method for excavation and support construction of the arch of an inclined rock cavern includes: S1. Pre-excavation preparation of the cavern arch and acquisition of the dip angle of the inclined rock stratum 2, wherein the longitudinal section view of the pre-excavation of the cavern arch is as follows. Figure 1 As shown; and based on the obtained rock stratum dip angle, the intersection line of the bedding plane of the inclined rock stratum 2 and the horizontal plane is determined, and the construction channel axis is determined based on the intersection line, wherein the construction channel axis is the construction direction of the construction channel and is perpendicular to the intersection line; The selected direction is perpendicular to the dip angle of the inclined rock stratum 2. This direction ensures that during subsequent excavation on both sides, the force direction of the inclined rock stratum 2 is perpendicular to the bedding plane, effectively inhibiting the sliding of the inclined rock stratum 2 along the bedding plane and preventing the collapse of the excavation face from the root.

[0018] S2. Arrange a support system for construction passage 3 to obtain a stable construction passage 3; The construction passage support system includes: spraying early-strength concrete to seal the rock surface of the construction passage; laying steel mesh 6; installing steel arch frame 4; and installing a locking anchor rod 7 at the arch foot to form a stable construction passage 3. The construction passage 3 section is usually a straight wall type. After the initial support is formed, it can directly meet the needs of equipment and vehicle passage and staff operation without additional repairs, which greatly speeds up the construction progress.

[0019] The early-strength concrete with added accelerator can be quickly formed and reach its strength earlier. For the broken rock face after excavation, it can integrate the broken rock layers through the bonding effect of concrete, avoid continuous slag shedding at the face or sidewall, and eliminate safety hazards.

[0020] One possible design is that the anchor rod 7 has evenly distributed small holes on its shaft. After being driven into the inclined rock layer 2, the small holes in the shaft allow the injected cement mortar to overflow evenly, fully filling the gap between the anchor rod 7 and the rock layer, and greatly enhancing the connection strength between the anchor rod 7 and the inclined rock layer 2.

[0021] S3. Starting from construction access road 3, extend the excavation of the pilot area in the middle of the tunnel arch 1 as follows: Figure 2-3 , The central pilot area is excavated in two layers, centered on the axis of the cavern arch 1, as shown below. Figure 4 After the top surface of the upper cavern arch 1 is excavated, the upper cavern arch support system is arranged to form a stable working space. The central pilot area is excavated in two layers using a small tracked excavator. Compared with the traditional full-face excavation, this reduces the disturbance to the inclined rock strata 2. In addition, the early excavation of the upper layer can provide support for the cavern arch 1 in advance, thus providing a safety guarantee for the excavation of the lower layer.

[0022] The cavern arch support system includes: after the top surface of the cavern arch 1 is excavated, early-strength concrete is immediately sprayed to seal the rock surface, steel mesh 6 is laid, steel arch frame 4 is installed, and early-strength concrete is sprayed again to form a stable working space; the steel arch frame 4 is the main load-bearing structure, which can directly bear the in-situ sliding force of the inclined rock layer 2 and balance the lateral pressure of the rock layer through rigid support.

[0023] One possible design is that the steel mesh 6 is welded between the two steel arch frames 4, which can enhance the overall rigidity of the shotcrete, reduce the deformation of the concrete caused by rock pressure, and avoid support failure caused by concrete cracking.

[0024] S4. Taking the central pilot area as the boundary, the two sides of the cave arch 1 are symmetrically divided into independent excavation areas. Each side adopts a pre-set excavation strategy, and the entire excavation process follows the principle of symmetrical construction and inside-outside. Support is immediately provided after each excavation step, and the next step is carried out only after the support deformation of the previous area / step has stabilized. The preset excavation strategy is a "three-zone, three-step" strategy, which involves dividing the excavation section on one side radially into three zones: the innermost, the middle, and the outermost. Each zone is then excavated in three small advances. Breaking the excavation section on both sides into smaller zones and excavating them in multiple stages avoids concentrated disturbance to the inclined rock strata 2 caused by a single large-section excavation, reduces the risk of bedding plane slippage and rock block detachment, and ensures the stability of the rock surface during excavation. The reason for excavating the innermost zone first is that the bedding angle of the inclined rock strata 2 is higher on the right and lower on the left. Excavating and supporting the innermost zone first can effectively resist the bedding-parallel sliding force of the inclined rock strata 2, and the inclined rock strata 2 in the middle zone is less likely to fall. If the outer zone is excavated first, the inclined rock strata 2 in the middle zone is prone to bedding-parallel sliding, resulting in debris falling and collapse, posing a greater safety hazard.

[0025] The specific steps of the "three zones and three steps" include: S401: Innermost excavation support: as shown Figure 5-6 As shown, the innermost area on one side is excavated first, followed by initial shotcrete, laying of steel mesh 6, installation of steel arch frame 4, and installation of 2 anchor bolts 7 at the arch foot, and then shotcrete again; the innermost area on the other side is excavated symmetrically to ensure the balance of forces on both sides. S402: Central Excavation Support: (e.g., ...) Figure 7-8 As shown, after the innermost support on one side is stable, the middle area on the same side is excavated, initial shotcrete is applied after excavation, steel mesh 6 is laid, steel arch frame 4 is installed, and shotcrete is applied again; the middle area on the other side is excavated symmetrically at the same time to avoid unilateral pressure. S403: Outermost excavation support: such as Figure 9-10 As shown, after the central support on one side is stabilized, the outermost area on the same side is excavated; after excavation, initial shotcrete is applied, steel mesh 6 is laid, steel arch frame 4 is installed, two anchor bolts 7 are installed at the arch foot, and shotcrete is applied again to enhance the edge stability of the tunnel arch 1.

[0026] This application addresses the construction challenges of slag shedding, eccentric deformation, and easy collapse in the arch of inclined rock caverns by employing a refined step-by-step excavation process to minimize disturbance to the surrounding rock.

[0027] In the early stages of construction, advanced geological surveys were conducted to accurately determine the geological characteristics of the rock strata, such as their dip angle and integrity, providing a basis for the construction plan. During the construction phase, construction channels were laid vertically to the dip angle of the rock strata to inhibit bedding slippage from the source of stress and avoid potential risks of bias pressure.

[0028] Based on the existing construction passage, a layered and zoned excavation method was adopted. First, two layers of pilot excavation were carried out in the middle to create a stable and safe working space in advance. Then, the two sides of the tunnel were divided into multiple construction areas, and excavation was carried out step by step strictly following the principle of "symmetrical construction and internal-to-external." Throughout the entire process, excavation and support were carried out immediately after each excavation step to prevent long-term exposure of the rock strata. This effectively solved the technical problems of traditional excavation techniques, such as large disturbances and susceptibility to surrounding rock collapse and deformation.

[0029] This application adopts a collaborative construction design that seamlessly integrates excavation and support, constructing a high-strength and high-stability joint support system. After the excavation of the construction access road, the central pilot area, and the two side sections is completed, standardized support operations such as early-strength concrete spraying and sealing, steel mesh laying, steel arch frame installation, and anchor bolt fixing are immediately carried out, with each process closely connected and efficiently closed-loop.

[0030] Among them, the steel arch frame effectively bears and offsets the sliding force of the rock strata along the bedding plane, improving the overall structural bearing capacity; the steel mesh enhances the integrity of the shotcrete and prevents cracking and detachment of the support surface layer; the anchor bolts are deeply embedded in the arch foot, consolidating the structural foundation. At the same time, the symmetrical and synchronous advancement and gradual closure of the supports on both sides guides the rock strata stress to be transmitted to the support system in an orderly manner, specifically balancing the bias pressure of the inclined rock strata, and thoroughly improving the problems of traditional support lag, insufficient resistance to bias pressure, and poor structural stability.

[0031] This construction technique combines practicality and flexibility, with a compact overall process and high construction efficiency. Once the straight-wall construction passage is completed, it can directly meet the basic needs of on-site equipment access and personnel operation; the pilot excavation in the middle opens up the working interface in advance, significantly reducing the time spent on subsequent process connections and improving construction efficiency.

[0032] The innovative "three-zone, three-step" excavation and support model allows for flexible adjustment of construction parameters and process rhythm based on the dip angle and rock fragmentation degree of the site. It requires no special construction equipment and is highly adaptable. The support components adopt a standardized layout and modular installation mode, enabling precise configuration as needed, effectively reducing construction complexity and minimizing redundant material consumption. This technology is particularly suitable for the construction of arched structures in tunnels, offering controllable construction quality, significant cost advantages, and strong value for engineering promotion and application.

[0033] For example, an underground arch project is buried at a depth of 200m, with an arch span of 12m and an arch height of 5m. It is located in a sandy carbonaceous rock stratum with an inclined attitude. The exploration determined that the bedding angle is 35° (higher on the right and lower on the left), with a moderate degree of fracturing and local development of fissures.

[0034] Ground-penetrating radar was used to conduct advance surveys at a depth of 8m in the arch excavation area, with one survey profile laid out every 5m along the tunnel axis. Simultaneously, three boreholes were drilled in the central pilot excavation area for core sampling. The results show that the arch strata are layered, with a bedding angle of 35°. The fractured zones are concentrated on both sides of the arch edge, and there are no large-scale faults or weak interlayers in the central pilot area, providing geological basis for optimizing the construction plan.

[0035] Centered on the arch axis perpendicular to the 35° rock dip angle, a straight-wall construction passage with a cross-section of 2.0m × 2.2m was excavated to meet equipment passage requirements. Short-advance excavation was adopted, with a single advance of ≤0.6m. Immediately after excavation, a 6cm thick layer of C25 early-strength concrete was sprayed, incorporating an accelerator, so that the strength reached 80% of the design value after 2 hours. Next, the rock surface was sealed, a Φ6mm × 20cm × 20cm steel mesh was laid, and I16 I-beam steel arch frames were installed with a spacing of 1.0m. At the arch foot, a Φ22mm hollow anchor rod was inserted at a 45° angle, with an 8mm grouting hole in the rod body. Grouting filled the gap between the anchor rod and the rock strata, forming a stable passage support system.

[0036] Starting from the construction access road, a pilot area with a circular cross-section and a diameter of 2.2m was excavated towards the center of the arch. A small tracked excavator was used to excavate in two layers, with each layer being 2.5m high and each advance ≤0.5m. After the upper layer excavation exposed the top surface of the arch, the support was carried out according to the process of "initial spraying - laying mesh - scaffolding - re-spraying": first, an 8cm thick layer of C25 early-strength concrete was sprayed, then a steel mesh was laid, followed by the installation of I18 I-beam steel arch frames with a spacing of 0.8m, and finally, a 16cm thick layer of concrete was sprayed again to create a stable working space.

[0037] First, excavate an area of ​​3.2m. 2 The innermost zone on the right side was excavated at a rate of 0.5m per step. After excavation, a 6cm thick layer of C25 concrete was initially sprayed, followed by the laying of a steel mesh. I18 I-beam steel arch frames were then installed and welded to the central steel arch frame at a spacing of 0.8m. Two Φ25mm anchor bolts were inserted at the arch foot at a 30° angle and grouting was performed for reinforcement. Finally, a 18cm thick layer of concrete was sprayed again. Subsequently, the innermost zone on the left side was excavated symmetrically and supported according to the same standard to ensure the balance of forces on both sides.

[0038] After the innermost support on the right side has stabilized, excavate an area of ​​3.8m² on the same side. 2 In the central area, the single advance is 0.6m, and the support is carried out according to the D1 process. The installed steel arch frame maintains a 35cm overlap length with the innermost steel arch frame; at the same time, the left central area is excavated symmetrically to avoid unilateral pressure.

[0039] After the support in the middle of the right side is stable, excavate an area of ​​4.2m² on the same side. 2In the outermost zone, over-excavation was strictly controlled during construction, and C25 concrete was used to backfill the over-excavated areas. After excavation, an 8cm thick layer of C25 concrete was initially sprayed, a steel mesh was laid, and I20 I-beam steel arches were installed and welded to the central steel arch frame at a spacing of 0.7m. Two Φ25mm anchor bolts were inserted at the arch foot and grouting was performed at a grouting pressure of 1.2MPa. Finally, concrete was sprayed again to a thickness of 20cm. After the right side was completed, the left side was constructed according to the same standard.

[0040] After the excavation and support on both sides are completed, the final support step is delayed by 2 steps. The initial shotcrete on the arch wall is leveled to ensure that all support components are covered. Then, EVA waterproof membrane is laid, and finally C30 cast-in-place concrete is poured for secondary lining to complete the arch structure.

[0041] The selected direction is perpendicular to the dip angle of the inclined rock stratum 2. This direction ensures that the force direction of the rock stratum is perpendicular to the bedding plane during subsequent excavation on both sides, effectively inhibiting the sliding of the inclined rock stratum 2 along the bedding plane and preventing the collapse of the excavation face from the root.

[0042] The construction passage 3 section is usually a straight wall type. After the initial support is formed, it can directly meet the needs of equipment and vehicle passage and staff operation without additional repairs, which greatly speeds up the construction progress.

[0043] The central pilot area is excavated in two layers using a small tracked excavator. Compared with the traditional full-section excavation, this reduces the disturbance to the inclined rock strata 2. In addition, the early excavation of the upper layer can provide support for the cavern arch 1 in advance, thus providing a safety guarantee for the excavation of the lower layer.

[0044] In this embodiment, the anchor bolt 7 is driven into the inclined rock layer 2 from the foot of the steel frame arch 4 at an angle of 30° to 60° to the ground. The anchor bolt 7 is perpendicular to the inclined rock layer, so as to maximize the supporting effect of the anchor bolt and inhibit the sliding of the rock layer along the bedding plane.

[0045] In this embodiment, the "three zones and three steps" refers to dividing the single-sided excavation section radially into three zones: the innermost, the middle, and the outermost. Each zone is then excavated in three small advances. By breaking down the two-sided excavation sections into small areas and excavating them in multiple stages, concentrated disturbance to the inclined rock strata 2 can be avoided by a single large-section excavation, reducing the risk of bedding plane slippage and rock block detachment, and ensuring the stability of the rock surface during the excavation process.

[0046] In this embodiment, the reason for excavating the innermost area on one side first is that the dip angle of the inclined rock stratum 2 is higher on the right and lower on the left. Excavating the innermost support first can effectively resist the in-bedding sliding force of the inclined rock stratum 2, and the inclined rock stratum 2 in the middle area is not easy to fall off. If the outer area is excavated first, the inclined rock stratum 2 in the middle area is prone to in-bedding sliding, resulting in safety accidents such as debris falling and collapse.

[0047] This application addresses the challenges of strata-parallel slippage and eccentric deformation in the arch section of inclined rock strata caverns by employing precise, phased excavation to control strata disturbance. First, advanced geological surveys clarify the characteristics of the rock strata. Then, a construction channel 3 is excavated along the dip angle perpendicular to the inclined rock strata 2, suppressing strata-parallel slippage at the source of stress. Subsequently, starting from construction channel 3, a two-layer pilot excavation is carried out in the middle section to establish a stable working space in advance. Finally, the two sides are divided into multiple areas, and excavation is carried out in phases according to the principle of "symmetrical construction, inside first, outside later." Each excavation step is promptly sealed and supported to prevent prolonged exposure of the rock strata, effectively solving the problems of significant disturbance to the inclined rock strata 2 and the tendency to cause collapse caused by traditional excavation methods.

[0048] This application employs a synchronized excavation and support design to enhance structural stability: After excavation of the construction passage 3, the central pilot area, and both sides, early-strength concrete is immediately sprayed for sealing, followed by the laying of steel mesh 6, installation of steel arch frames 4, and the installation of anchor bolts 7. The steel arch frames 4 bear the in-stratum sliding force, the steel mesh 6 enhances the overall integrity of the sprayed concrete, and the anchor bolts 7 deeply anchor the arch feet. Furthermore, the symmetrical advancement and gradual closure of the supports on both sides ensures the orderly transfer of rock stress to the support system, specifically balancing the bias pressure of the inclined rock strata 2, thus addressing the shortcomings of traditional supports, such as lag and weak resistance to bias pressure.

[0049] The construction steps in this application are both adaptable and practical. Once the straight-wall construction passage 3 is completed, it can directly meet the operational needs of equipment and personnel. The pilot excavation in the middle creates operational conditions for subsequent construction and reduces the time spent on process connections. The "three-zone, three-step" excavation and collaborative support steps can be flexibly adjusted according to the dip angle and degree of fracture of the inclined rock strata 2. It can be implemented without special equipment, and the support components are laid out as needed and installed in a standardized manner, reducing construction complexity and material consumption. It is particularly suitable for the construction of the arch structure of the cavern arch 1 and has strong applicability.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for excavation and support construction of the arch of an inclined rock cavern, characterized in that, include: S1. Obtain the dip angle of the inclined rock strata, and determine the intersection line between the rock strata bedding plane and the horizontal plane based on the obtained rock strata dip angle. Determine the construction channel axis based on the intersection line, wherein the construction channel axis is the construction direction of the construction channel and is perpendicular to the intersection line. S2. Arrange a support system for the construction access road; The construction passage support system includes: spraying early-strength concrete to seal the rock surface of the construction passage; laying steel mesh and installing steel arches to form a stable construction passage; S3. Starting from the construction access road, extend the excavation of the central pilot area towards the middle of the tunnel arch. The central pilot area is excavated in two layers, with the tunnel arch axis as the center. After the top surface of the tunnel arch is excavated in the upper layer, the upper tunnel arch support system is arranged to form a stable working space. The tunnel arch support system includes: after the top surface of the tunnel arch is excavated, early-strength concrete is immediately sprayed to seal the rock surface, steel mesh is laid, steel arch frame is installed, and early-strength concrete is sprayed again to form a stable working space. S4. Using the central pilot area as the boundary, the two sides of the tunnel arch are symmetrically divided into independent excavation areas. Each side adopts a pre-set excavation strategy, and the entire excavation process follows the principle of symmetrical construction and inside-outside. Support is provided immediately after each excavation step, and the next step is carried out only after the support deformation of the previous step has stabilized.

2. The method for excavation and support of the arch of an inclined rock cavern according to claim 1, characterized in that, The preset mining strategy includes: S401: Innermost Excavation and Support: First, excavate the innermost area on one side, then spray concrete, lay steel mesh, install steel arch frame, install two anchor bolts at the arch foot, and spray concrete again; symmetrically excavate the innermost area on the other side to ensure the balance of forces on both sides. S402: Central Excavation and Support: After the innermost support on one side is stable, excavate the central area on the same side, spray initial concrete after excavation, lay steel mesh, install steel arch frame, and spray concrete again; excavate the central area on the other side symmetrically at the same time to avoid unilateral pressure. S403: Outermost Excavation Support: After the middle support on one side is stable, excavate the outermost area on the same side; after excavation, spray concrete initially, lay steel mesh, install steel arch frame, install 2 anchor bolts at the arch foot, spray concrete again to enhance the stability of the arch 1 edge of the cavern.

3. The method for excavation and support of the arch of an inclined rock cavern according to claim 1, characterized in that, The steel mesh is welded between the two steel arch frames.

4. The method for excavation and support of the arch of an inclined rock cavern according to claim 1, characterized in that, The anchor bolts are driven into the inclined rock strata from the foot of the steel frame arch at an angle of 30° to 60° with the ground.

5. The construction method for excavation and support of the arch of an inclined rock cavern according to claim 3, characterized in that, The anchor rod has evenly distributed small holes.

6. The method for excavation and support of the arch of an inclined rock cavern according to claim 5, characterized in that, The "three zones and three steps" refers to dividing the single-sided excavation section radially into three zones: the innermost zone, the middle zone, and the outermost zone. Each zone is then excavated three times according to a preset advance.

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