A small-clearance tunnel based on dynamic reinforcement and synergistic support

Abstract

This utility model relates to the field of tunnel engineering technology, specifically to a small-clearance tunnel based on dynamic reinforcement and collaborative support. It includes a pilot tunnel, a follow-up tunnel, and a central rock column positioned between the pilot and follow-up tunnels. The model also includes a support structure fitted to the inner wall of the pilot tunnel, hydraulic temporary support mechanisms deployed within the pilot and follow-up tunnels, a segmented prestressed anchor structure embedded within the central rock column, a real-time monitoring system deployed in the central rock column area, and multiple segmented grouting guide pipes radially penetrating the central rock column with one end extending into the pilot tunnel. The central rock column is divided radially from the inside to the outside of the tunnel into a core high-strength grouting zone, a transitional grouting zone, and a peripheral permeable grouting zone. All components of this utility model work closely together to dynamically reinforce and collaboratively support the small-clearance tunnel from multiple dimensions, comprehensively reducing construction risks, extending the tunnel's service life, and providing a solid guarantee for the safe and reliable operation of the project.

Description

Technical Field

[0001] This utility model relates to the field of tunnel engineering technology, specifically to a small-clearance tunnel based on dynamic reinforcement and collaborative support. Background Technology

[0002] In the construction of tunnels with small clearances, the central rock column, as a key component connecting the preceding and following tunnels, experiences significant stress concentration under the combined excavation and load conditions of both tunnels. This makes it highly susceptible to shear failure or eccentric instability, seriously threatening the safety of the tunnel structure. Traditional symmetrical support techniques are ineffective in handling asymmetrical load distribution conditions, leading to frequent cracking and excessive deformation of the initial support, failing to meet engineering safety requirements. Furthermore, the cumulative effect of construction disturbances during the construction of the preceding and following tunnels is significant, with the construction of the two tunnels influencing each other, further exacerbating the risk of surrounding rock deformation and failure.

[0003] Currently, in the construction of tunnels with small clearance, existing solutions for grouting reinforcement of the central rock column mostly adopt a single-range and fixed-parameter design, ignoring the dynamic evolution of stress redistribution in the surrounding rock throughout the entire tunnel construction cycle. This results in the grout diffusion range and reinforcement strength failing to meet actual needs, thus failing to fully realize the effectiveness of grouting reinforcement. Temporary support systems are constrained by fixed-rigidity structural designs, making it difficult to dynamically respond to differences in the deformation rate and amplitude of the surrounding rock at different construction stages. This often leads to insufficient or excessive support, weakening the ability to control tunnel deformation. In terms of construction processes, traditional construction relies heavily on experience-based pre-set procedures, lacking a dynamic decision-making mechanism driven by real-time monitoring data. When faced with complex geological conditions and sudden risks, it is difficult to quickly adjust construction parameters and processes, resulting in a lag in construction risk prevention and control. Utility Model Content

[0004] The purpose of this invention is to provide a small-clearance tunnel based on dynamic reinforcement and collaborative support, which addresses the current problems in small-clearance tunnel construction, such as: neglecting the dynamic changes of surrounding rock stress in grouting reinforcement of the central rock column; grout diffusion not matching the actual reinforcement strength; temporary support systems being unable to adapt to differences in surrounding rock deformation; improper support leading to weak deformation control; and traditional construction lacking a real-time data decision-making mechanism, making it difficult to adjust in time when encountering complex situations, resulting in lagging risk prevention and control.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a small-clearance tunnel based on dynamic reinforcement and collaborative support, comprising a pilot tunnel, a follow-up tunnel, and a central rock column set between the pilot tunnel and the follow-up tunnel, further comprising a support structure fitted to the inner wall of the pilot tunnel, hydraulic temporary support mechanisms respectively deployed inside the pilot tunnel and the follow-up tunnel, a segmented prestressed anchor structure embedded inside the central rock column, a real-time monitoring system deployed in the central rock column area, and multiple segmented grouting pipes radially penetrating the central rock column and extending one end into the pilot tunnel; the central rock column is divided into a core high-strength grouting zone, a transition grouting zone, and a peripheral permeable grouting zone from the inside to the outside along the tunnel radial direction; the grouting pressure of the core high-strength grouting zone is controlled at 1.5-2 MPa, and the grouting pressure of the peripheral permeable grouting zone is controlled at 0.5-1.0 MPa.

[0006] Furthermore, the support structure includes a double-layer steel mesh installed on the inner wall of the pilot tunnel near the central rock pillar, a steel arch frame connected to the double-layer steel mesh and attached to the inner wall of the pilot tunnel, and a flexible shotcrete layer sprayed onto the inner wall of the double-layer steel mesh; the flexible shotcrete layer is made of concrete and forms the initial support load-bearing structure.

[0007] Furthermore, the segmented prestressed anchor structure includes multiple prestressed short anchors and multiple prestressed tensioned long anchors; one end of each of the multiple prestressed short anchors is anchored to the steel arch frame of the pilot tunnel, and the other end is radially embedded into the interior of the central rock column; the multiple prestressed tensioned long anchors transversely penetrate the central rock column and are arranged in a matrix, with their two ends welded and fixed to the steel arch frames in the pilot tunnel and the subsequent tunnel, respectively, forming a joint force-bearing system across the central rock column.

[0008] Furthermore, the hydraulic temporary support mechanism includes a horizontal support hydraulic cylinder, a vertical support hydraulic cylinder, and multiple steel pads. The horizontal support hydraulic cylinder is arranged transversely along the tunnel, and its two ends abut against the inner walls of the preceding tunnel and the following tunnel. The vertical support hydraulic cylinder is arranged longitudinally along the tunnel, and its two ends abut against the inner walls of the preceding tunnel and the following tunnel. The steel pads are respectively disposed between the inner walls of the preceding tunnel and the following tunnel and the contact surfaces of the horizontal support hydraulic cylinder and the vertical support hydraulic cylinder.

[0009] Furthermore, the real-time monitoring system includes multiple strain gauges and multiple fiber optic sensors; the multiple strain gauges are spaced apart on the sidewall of the rock column near the pilot tunnel to monitor the surface strain of the rock column; the multiple fiber optic sensors are arrayed and embedded inside the rock column to monitor the internal stress and deformation data of the rock column.

[0010] Furthermore, the outer wall of the segmented grouting conduit extends into the core high-strength grouting zone and has multiple first grouting holes at one end, while the outer wall of the segmented grouting conduit extends into the peripheral permeable grouting zone and has multiple second grouting holes at one end. The density of the multiple first grouting holes is greater than that of the multiple second grouting holes.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0012] This utility model employs a support structure that fits tightly against the inner wall of the tunnel, effectively supporting and reinforcing the tunnel wall after excavation and controlling the deformation of the surrounding rock. Its equipped hydraulic temporary support mechanism can dynamically adjust the support force according to actual construction needs, providing reliable structural stability during the dual-tunnel excavation process and preventing damage to the central rock pillar due to uneven stress.

[0013] The application of segmented prestressed anchor structures enhances the overall bearing capacity of the central rock column and constructs a stable system for cross-tunnel coordinated stress.

[0014] The real-time monitoring system can dynamically and in real-time monitor key data such as stress and deformation of the rock column. Based on this real-time feedback monitoring data, construction personnel can adjust the excavation step distance and blasting parameters of the subsequent tunnel to ensure that the disturbance wave peaks generated by the construction of the two tunnels are staggered and reduce the negative impact of construction on the tunnel structure.

[0015] The segmented grouting guide pipes, combined with different grouting gradient zones, utilize differentiated grouting pressures based on the core high-strength grouting zone, transitional grouting zone, and peripheral permeable grouting zone defined by advanced geological prediction. This grouting method ensures both high-strength reinforcement of the core area and effective permeability of the peripheral areas, comprehensively improving the overall density and strength of the central rock column.

[0016] The various components of this utility model work closely together to dynamically reinforce and coordinate the support of tunnels with small clearances from multiple dimensions, comprehensively reducing construction risks, extending the service life of the tunnels, and providing a solid guarantee for the safe and reliable operation of the project. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of the small-clearance tunnel based on dynamic reinforcement and synergistic support according to this utility model.

[0018] Figure 2 This is a schematic cross-sectional view of the small-clearance tunnel based on dynamic reinforcement and synergistic support according to this utility model.

[0019] Figure 3 This is a schematic cross-sectional view of the small-clearance tunnel based on dynamic reinforcement and synergistic support according to this utility model.

[0020] Figure 4 This is a schematic cross-sectional view of the small-clearance tunnel based on dynamic reinforcement and synergistic support according to this utility model.

[0021] Figure 5 This is a schematic diagram of the segmented grouting guide tube structure of this utility model;

[0022] Figure 6 This is a schematic diagram of the construction process and monitoring feedback logic of a small-clearance tunnel based on dynamic reinforcement and collaborative support according to this utility model.

[0023] In the diagram: 1. Pre-existing tunnel; 2. Subsequent tunnel; 3. Middle rock column; 4. Core high-strength grouting zone; 5. Transition grouting zone; 6. Peripheral permeable grouting zone; 7. Prestressed short anchor bolt; 8. Prestressed tension anchor bolt; 9. Steel arch frame; 10. Double-layer steel mesh; 11. Flexible shotcrete layer; 12. Strain gauge; 13. Fiber optic sensor; 14. Steel pad; 15. Horizontal support hydraulic cylinder; 16. Vertical support hydraulic cylinder; 17. Segmented grouting small guide pipe; 18. First grouting hole; 19. Second grouting hole. Detailed Implementation

[0024] Please see Figure 1-6 A small-clearance tunnel based on dynamic reinforcement and synergistic support includes a pilot tunnel 1, a follow-up tunnel 2, and a central rock pillar 3 located between the pilot tunnel 1 and the follow-up tunnel 2. It also includes a support structure fitted to the inner wall of the pilot tunnel 1, hydraulic temporary support mechanisms respectively deployed inside the pilot tunnel 1 and the follow-up tunnel 2, a segmented prestressed anchor structure embedded inside the central rock pillar 3, a real-time monitoring system deployed in the area of ​​the central rock pillar 3, and multiple segmented grouting guides radially penetrating the central rock pillar 3 and extending one end into the pilot tunnel 1. Pipe 17; Based on the advanced geological forecast, the degree of fracture development of the central rock column 3 is determined to divide the grouting gradient area. The central rock column 3 is divided into a core high-strength grouting zone 4, a transition grouting zone 5, and a peripheral permeable grouting zone 6 along the radial direction of the tunnel from the inside to the outside; The segmented grouting pipe 17 is used to control the grouting pressure of the core high-strength grouting zone 4 at 1.5-2MPa, the grouting pressure of the transition grouting zone 5 at 1.0-1.5MPa, and the grouting pressure of the peripheral permeable grouting zone 6 at 0.5-1.0MPa for grouting.

[0025] The support structure includes a double-layer steel mesh 10 located on the inner wall of the pilot tunnel 1 near the central rock column 3, a steel arch frame 9 connected to the double-layer steel mesh 10 and attached to the inner wall of the pilot tunnel 1, and a flexible shotcrete layer 11 sprayed onto the inner wall of the double-layer steel mesh 10; the flexible shotcrete layer 11 is made of concrete and forms the initial support bearing structure.

[0026] The segmented prestressed anchor structure includes multiple prestressed short anchors 7 and multiple prestressed tension anchors 8. One end of each prestressed short anchor 7 is anchored to the steel arch frame 9 of the pilot tunnel 1, and the other end is radially embedded into the middle rock column 3. The multiple prestressed tension anchors 8 transversely penetrate the middle rock column 3 and are arranged in a matrix. Their two ends are welded and fixed to the steel arch frames 9 in the pilot tunnel 1 and the subsequent tunnel 2, respectively, forming a collaborative force-bearing system across the middle rock column 3. The multiple prestressed short anchors 7 are firmly anchored at one end to the steel arch frame 9 of the pilot tunnel 1, and the other end is radially embedded into the middle rock column 3, which can enhance the connection strength between the tunnel wall of the pilot tunnel 1 and the middle rock column 3, and locally reinforce the side of the middle rock column 3 near the pilot tunnel 1, limiting the deformation of the surrounding rock. The prestressed elongated anchor rods 8 penetrate the central rock column 3 laterally and are arranged in a matrix. Both ends are welded and fixed to the steel arch frame 9 in the first tunnel 1 and the second tunnel 2, respectively, to construct a collaborative force-bearing system that spans the central rock column 3. The two tunnels are treated as a whole to carry the load collaboratively, which improves the overall shear and tensile strength of the central rock column 3 and disperses the load during construction and operation.

[0027] The hydraulic temporary support mechanism includes horizontal hydraulic cylinders 15, vertical hydraulic cylinders 16, and multiple steel pads 14. The horizontal hydraulic cylinders 15 are arranged transversely along the tunnel, with both ends abutting against the inner walls of the first tunnel 1 and the second tunnel 2. The vertical hydraulic cylinders 16 are arranged longitudinally along the tunnel, with both ends abutting against the inner walls of the first tunnel 1 and the second tunnel 2. The steel pads 14 are respectively placed between the inner walls of the first tunnel 1 and the second tunnel 2 and the contact surfaces of the horizontal hydraulic cylinders 15 and the vertical hydraulic cylinders 16. The horizontal hydraulic cylinders 15, arranged transversely along the tunnel, tightly abut against the inner walls of the first tunnel 1 and the second tunnel 2 at both ends, which can resist the transverse deformation pressure during the construction of the two tunnels and prevent the central rock column 3 from cracking due to transverse stress concentration. The vertical hydraulic cylinders 16, arranged longitudinally, ensure the longitudinal stability of the tunnel and avoid excessive settlement caused by excavation disturbance. The multiple steel pads 14 placed between the contact surfaces can evenly distribute the supporting force of the horizontal support hydraulic cylinder 15 and the vertical support hydraulic cylinder 16 to the tunnel wall, preventing excessive local stress from damaging the surrounding rock, while also enhancing the fit and friction between the horizontal support hydraulic cylinder 15, the vertical support hydraulic cylinder 16 and the tunnel wall.

[0028] The real-time monitoring system includes multiple strain gauges 12 and multiple fiber optic sensors 13. The multiple strain gauges 12 are spaced apart on the side wall of the central rock column 3 near the pilot tunnel 1 to monitor the surface strain of the central rock column 3. The angle and spacing distribution of the prestressed anchor rods 8 and the prestressed short anchor rods 7 are determined by the monitoring data. The multiple fiber optic sensors 13 are arrayed and embedded inside the central rock column 3 to monitor the internal stress and deformation data of the central rock column 3. The support pressure of the temporary horizontal support hydraulic cylinder 15 and the vertical support hydraulic cylinder 16 is dynamically adjusted according to the real-time monitoring data to adjust the excavation advance and control the convergence difference between the two tunnels.

[0029] The outer wall of the segmented grouting conduit 17 extends into the core high-strength grouting zone 4 and has multiple first grouting holes 18. The outer wall of the segmented grouting conduit 17 extends into the peripheral permeable grouting zone 6 and has multiple second grouting holes 19. The density of the multiple first grouting holes 18 is greater than that of the multiple second grouting holes 19.

[0030] By densely arranging multiple first grouting holes 18 at one end of the segmented grouting conduit 17 extending into the core high-strength grouting zone 4, and arranging a relatively sparse number of second grouting holes 19 at the other end extending into the peripheral permeable grouting zone 6, on the one hand, the high density of the first grouting holes 18, combined with the high grouting pressure of 1.5-2 MPa in the core high-strength grouting zone 4, ensures sufficient grout injection into the core area, achieving high-strength reinforcement and improving the bearing capacity and stability of the core part of the central rock column 3; on the other hand, the low density of the second grouting holes 19 is compatible with the lower grouting pressure of 0.5-1.0 MPa in the peripheral permeable grouting zone 6, allowing the grout to permeate and diffuse evenly at a suitable flow rate and range, avoiding excessive pressure that could cause the surrounding rock to split, ensuring the reinforcement effect of the peripheral area while reducing grouting costs and construction risks.

[0031] A construction method for small-clearance tunnels based on dynamic reinforcement and synergistic support, comprising the following steps:

[0032] Step 1: In the early stage of construction, advanced geological prediction technology was used to comprehensively investigate the fracture development of the central rock column 3. Based on the investigation results, the central rock column 3 was divided into a core high-strength grouting zone 4, a transition grouting zone 5, and a peripheral permeable grouting zone 6 from the inside out along the tunnel radial direction. Subsequently, grouting operations were carried out using radially arranged segmented grouting pipes 17. The grouting pressure in the core high-strength grouting zone 4 was controlled at 1.5-2 MPa to achieve high-strength reinforcement. The grouting pressure in the peripheral permeable grouting zone 6 was set at 0.5-1.0 MPa to ensure sufficient penetration and diffusion of the grout. Different pressure settings effectively improved the grouting reinforcement effect.

[0033] Step 2: After the excavation of the pilot tunnel 1 is completed, the construction of prestressed short anchor rods 7 (3-5m in length) will be carried out immediately. One end of the anchor rods will be firmly anchored to the tunnel wall, and the other end will be radially embedded into the central rock column 3 to initially enhance the stability of the connection between the tunnel wall and the central rock column 3. Next, double-layer steel mesh 10 will be laid in sequence, steel arch frame 9 will be installed, and shotcrete will be sprayed to form a flexible shotcrete layer 11 to construct the initial support bearing structure and timely support the excavated tunnel wall to prevent deformation of the surrounding rock.

[0034] Step 3: After the initial support of the pilot tunnel 1 is completed, multiple strain gauges 12 are installed at preset intervals on the side of the central rock column 3 near the pilot tunnel 1 to monitor the surface strain of the central rock column 3 in real time. At the same time, multiple fiber optic sensors 13 are embedded in the rock mass of the central rock column 3 in an array layout to build a real-time rock mass stress monitoring network, so as to obtain the internal stress and deformation data of the central rock column 3 in all aspects and provide data support for subsequent construction decisions.

[0035] Step 4: Before the excavation of the second tunnel, in order to enhance the collaborative bearing capacity of the two tunnels, long prestressed tie rods 8 (8-12m in length) are installed to penetrate the central rock column 3 laterally. The two ends are welded and fixed to the steel arch frame 9 in the first tunnel 1 and the second tunnel 2 respectively, forming a collaborative force-bearing system across the central rock column 3. At the same time, the hydraulic temporary support mechanism deployed inside the first tunnel 1 and the second tunnel 2 is activated. The mechanism consists of horizontal support hydraulic cylinder 15, vertical support hydraulic cylinder 16 and steel pad 14. The horizontal support hydraulic cylinder 15 and the vertical support hydraulic cylinder 16 abut against the inner wall of the two tunnels to provide temporary support for the excavation of the second tunnel 2.

[0036] Step 5: During the subsequent construction process, continuously collect real-time monitoring data from strain gauge 12 and fiber optic sensor 13, dynamically adjust the support pressure of cross brace hydraulic cylinder 15 based on data changes, and reasonably control the excavation progress of the rear tunnel 2; strictly control the convergence difference between the two tunnels to within 15mm to ensure the safety of the construction of the two tunnels and avoid affecting the stability of the tunnel structure due to excessive deformation.

[0037] Working process and principle: Before construction, the degree of fracture development in the central rock column 3 is determined through advanced geological forecasting. Based on this, the core high-strength grouting zone 4, the transition grouting zone 5, and the peripheral permeable grouting zone 6 are divided. Multiple segmented grouting pipes 17, which are radially inserted through the central rock column 3 and extend one end into the pilot tunnel 1, are used to grout according to different areas. The core high-strength grouting zone 4 is 1.5-2 MPa to ensure high-strength reinforcement, while the peripheral permeable grouting zone 6 is 0.5-1.0 MPa to achieve effective permeability. During the construction of the pilot tunnel 1, grouting is carried out using pipes installed on its inner wall near the entrance. The initial support bearing structure consists of a double-layer steel mesh 10 on one side of the near-central rock pillar 3, a steel arch frame 9 connected to and attached to the inner wall, and a flexible shotcrete layer 11 sprayed onto the inner wall of the double-layer steel mesh 10; the hydraulic temporary support mechanism consists of horizontal hydraulic cylinders 15 arranged transversely along the tunnel and abutting the inner walls of the first tunnel 1 and the subsequent tunnel 2 at both ends, vertical hydraulic cylinders 16 arranged longitudinally along the tunnel and abutting the inner walls of the two tunnels at both ends, and multiple steel pads 14 placed between the contact surfaces, dynamically adjusting the support pressure based on feedback from the real-time monitoring system; segmented prestressing. In the anchor structure, multiple prestressed short anchors 7 are anchored at one end to the steel arch frame 9 of the pilot tunnel 1 and radially embedded inside the central rock column 3. Multiple prestressed elongated anchors 8 transversely penetrate the central rock column 3 and are arranged in a matrix. Their two ends are welded and fixed to the steel arch frames 9 in the pilot tunnel 1 and the subsequent tunnel 2, respectively, forming a cooperative force-bearing system. The real-time monitoring system monitors the surface strain through multiple strain gauges 12 spaced at intervals on the sidewall of the central rock column 3 near the pilot tunnel 1, providing data for the angle and spacing distribution of the prestressed short anchors 7 and the prestressed elongated anchors 8. They are embedded in an array in the central rock column 3. Multiple fiber optic sensors 13 inside the rock column 3 monitor internal stress and deformation, thereby controlling the support pressure of the horizontal support hydraulic cylinder 15 and the vertical support hydraulic cylinder 16, adjusting the excavation advance, and controlling the convergence difference between the two tunnels. The outer wall of the segmented grouting guide pipe 17 has multiple first grouting holes 18 at one end near the core high-strength grouting zone 4, and multiple second grouting holes 19 at one end near the outer permeable grouting zone 6. The density of the first grouting holes 18 is greater than that of the second grouting holes 19, ensuring that the grout is injected as needed. All systems work together to ensure the safe and stable construction and operation of the small-clearance tunnel.

[0038] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A small-spacing tunnel based on dynamic reinforcement and coordinated support, comprising a leading hole (1), a trailing hole (2), and a middle rock pillar (3) arranged between the leading hole (1) and the trailing hole (2), characterized in that, It also includes a support structure fitted to the inner wall of the pilot tunnel (1), a hydraulic temporary support mechanism respectively installed inside the pilot tunnel (1) and the rear tunnel (2), a segmented prestressed anchor structure buried inside the central rock column (3), a real-time monitoring system installed in the area of ​​the central rock column (3), and multiple segmented grouting pipes (17) that radiate through the central rock column (3) and extend to the pilot tunnel (1) at one end; the central rock column (3) is divided into a core high-strength grouting zone (4), a transition grouting zone (5) and an outer permeable grouting zone (6) along the radial direction of the tunnel from the inside to the outside; the grouting pressure of the core high-strength grouting zone (4) is controlled at 1.5-2MPa, and the grouting pressure of the outer permeable grouting zone (6) is controlled at 0.5-1.0MPa.

2. The small-spacing tunnel according to claim 1, wherein The support structure includes a double-layer steel mesh (10) located on the inner wall of the pilot tunnel (1) near the central rock column (3), a steel arch frame (9) connected to the double-layer steel mesh (10) and attached to the inner wall of the pilot tunnel (1), and a flexible shotcrete layer (11) sprayed and covering the inner wall of the double-layer steel mesh (10); the flexible shotcrete layer (11) is made of concrete and forms the initial support bearing structure.

3. The small-clearance tunnel according to claim 2, characterized in that, The segmented prestressed anchor structure includes multiple prestressed short anchors (7) and multiple prestressed tensioned anchors (8); one end of each of the multiple prestressed short anchors (7) is anchored to the steel arch frame (9) of the pilot tunnel (1), and the other end is radially embedded into the interior of the central rock column (3); the multiple prestressed tensioned anchors (8) are transversely penetrating the central rock column (3) and arranged in a matrix, and their two ends are welded and fixed to the steel arch frame (9) in the pilot tunnel (1) and the rear tunnel (2) respectively, forming a joint force-bearing system across the central rock column (3).

4. The close-spaced tunnel of claim 1 wherein, The hydraulic temporary support mechanism includes a horizontal support hydraulic cylinder (15), a vertical support hydraulic cylinder (16), and multiple steel pads (14). The horizontal support hydraulic cylinder (15) is arranged transversely along the tunnel, and both ends of the horizontal support hydraulic cylinder (15) abut against the inner walls of the pilot tunnel (1) and the rear tunnel (2). The vertical support hydraulic cylinder (16) is arranged longitudinally along the tunnel, and both ends abut against the inner walls of the pilot tunnel (1) and the rear tunnel (2). The steel pads (14) are respectively set between the inner walls of the pilot tunnel (1) and the rear tunnel (2) and the contact surfaces of the horizontal support hydraulic cylinder (15) and the vertical support hydraulic cylinder (16).

5. The small-clearance tunnel according to claim 1, characterized in that, The real-time monitoring system includes multiple strain gauges (12) and multiple fiber optic sensors (13); the multiple strain gauges (12) are spaced apart on the side wall of the rock column (3) near the pilot tunnel (1) to monitor the surface strain of the rock column (3); the multiple fiber optic sensors (13) are arrayed and embedded inside the rock column (3) to monitor the internal stress and deformation data of the rock column (3).

6. The close-spaced tunnel of claim 1 wherein, The outer wall of the segmented grouting conduit (17) extends into the core high-strength grouting zone (4) and is provided with a plurality of first grouting holes (18). The outer wall of the segmented grouting conduit (17) extends into the peripheral permeable grouting zone (6) and is provided with a plurality of second grouting holes (19). The arrangement density of the plurality of first grouting holes (18) is greater than that of the plurality of second grouting holes (19).

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