Rock pillar reinforcing structure in small-spacing tunnel

Abstract

The utility model relates to tunnel reinforcing engineering technical field, concretely to a kind of rock column reinforcing structure in small clear distance tunnel, including first hole, rear hole, middle rock column between first hole and rear hole, upper flange and lower flange respectively arranged in the upper and lower sides of middle rock column, multiple prestressed counter-pulling anchor rods transversely through middle rock column and matrix arrangement, further including honeycomb steel arch frame respectively arranged in the inner wall of first hole and rear hole, and the heating shape memory tensioning assembly respectively arranged at the two ends of prestressed counter-pulling anchor rod;The honeycomb steel arch frame and heating shape memory tensioning assembly are embeddedly connected;The honeycomb steel arch frame of the utility model forms lightweight stress grid with regular distribution hole, uniformly transfers rock wall load on the two sides of middle rock column, optimizes stress, reduces stress concentration;Prestressed counter-pulling anchor rod uses shape memory alloy pad, without traditional hydraulic equipment, heating triggers phase change to actively exert prestress, and construction is convenient and economical.

Description

Technical Field

[0001] This utility model relates to the field of tunnel reinforcement engineering technology, specifically a rock pillar reinforcement structure in tunnels with small clearance. Background Technology

[0002] Small clearance tunnels refer to tunnels where the clearance between two parallel tunnels (i.e., the minimum horizontal distance between the outer contours of adjacent tunnel structures) is small, typically ranging from 0.5B to 2.5B (where B is the excavation width of a single tunnel). A key issue with small clearance tunnels is the stability of the central rock pillar. Insufficient rock pillar strength or excessive construction disturbance can lead to tunnel deformation, cracking, or even collapse.

[0003] Traditional reinforcement methods for tunnels with small clearances commonly include steel arch support, grouting reinforcement, anchor bolt reinforcement, and prestressed tie rod reinforcement. However, in actual reinforcement operations, the following problems exist: Firstly, the equipment investment cost is high, requiring specialized equipment such as hydraulic jacks and oil pumps during construction; secondly, the contact area between the reinforcement equipment and the rock mass is limited, making it difficult to fully adhere to the rock surface, resulting in weaker constraint on the central rock column. Furthermore, there is a lack of effective coordination among the various reinforcement measures, leading to poor overall synergy and uneven load distribution on the rock walls on both sides of the central rock column, as well as localized stress concentration, posing a potential threat to the safety and stability of the tunnel structure. Utility Model Content

[0004] The purpose of this utility model is to provide a rock pillar reinforcement structure for tunnels with small clearance, which solves the problems of large equipment investment, small contact area between reinforcement equipment and rock mass, weak clamping of the central rock pillar, and poor coordination of various reinforcement measures, resulting in uneven load distribution and local stress concentration on the rock walls on both sides of the central rock pillar.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a rock pillar reinforcement structure in a tunnel with small clearance, comprising a pilot tunnel, a follower tunnel, a central rock pillar located between the pilot tunnel and the follower tunnel, upper and lower flanges respectively located on the upper and lower sides of the central rock pillar, multiple prestressed tie rods arranged in a matrix and transversely penetrating the central rock pillar, and honeycomb steel arch frames respectively located on the inner walls of the pilot tunnel and the follower tunnel, as well as heatable shape memory tensioning components respectively located at both ends of the prestressed tie rods; the honeycomb steel arch frames and the heatable shape memory tensioning components are fitted together.

[0006] Furthermore, the prestressed tie rod includes a rod body, externally threaded rod segments connected to both ends of the rod body, and regular octagonal axial ribs provided on the outer wall of the rod body; the height of the regular octagonal axial ribs is 2-5mm, and the circumferential spacing is 10-20mm.

[0007] Furthermore, the heatable shape memory tensioning assembly includes a grout stop plug, a steel pad, a shape memory alloy pad, a plurality of expansion bolts, and a nut that is threadedly connected to the external threaded rod segment, all sequentially sleeved on the rod body; the end face of the nut is in close contact with the surface of the shape memory alloy pad; the steel pad is fixed to the side wall of the central rock column by a plurality of expansion bolts.

[0008] Furthermore, the shape memory alloy pad is made of a shape memory alloy with a single-pass memory effect, and the phase transition temperature of the shape memory alloy pad is 60-120℃.

[0009] Furthermore, the outer surface of the shape memory alloy pad is provided with multiple annularly spaced high-temperature resistant strain gauges.

[0010] Furthermore, the nut is welded to the externally threaded rod segment.

[0011] Furthermore, the honeycomb steel arch frame includes a steel plate and a plurality of regular hexagonal holes arranged in a honeycomb pattern on the steel plate; both the shape memory alloy pad and the steel pad are regular hexagonal prism structures, and their cross-sectional dimensions are adapted to the regular hexagonal holes, and the shape memory alloy pad and the steel pad have a circular through hole in the center for the rod to pass through; the regular hexagonal holes and the edges of the shape memory alloy pad interlock to form an interlocking structure.

[0012] Furthermore, both the pilot tunnel and the rear tunnel are equipped with multiple hollow grouting anchor rods arranged radially; the multiple hollow grouting anchor rods penetrate the upper flange and the lower flange, and extend into the interior of the pilot tunnel and the rear tunnel through the regular hexagonal holes of the honeycomb steel arch frame.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0014] 1. The honeycomb steel arch frame forms a lightweight stress-bearing grid through regularly arranged holes, which evenly transfers the load of the rock walls on both sides of the central rock column, optimizes the stress distribution, and reduces local stress concentration; the prestressed tie rod introduces shape memory alloy pads, abandoning traditional hydraulic equipment, and realizes active application of prestress by heating to trigger the phase change of the shape memory pads, making construction more convenient and economical.

[0015] 2. The surface of the prestressed tie anchor rod adopts an octagonal axial rib structure to increase the contact area with the rock mass of the central rock column, improve the static friction between the two, and enhance the anchoring performance of the prestressed tie anchor rod.

[0016] 3. Shape memory alloy pads and steel pads are embedded in the honeycomb steel arch frame. Through structural interlocking, a mechanical interlock is formed, which inhibits the rotation of the pads, improves the prestress transfer efficiency, and enhances the integrity and stress coordination of the middle rock column reinforcement structure.

[0017] 4. Hollow grouting anchors are used to reinforce the center of the honeycomb steel arch grid on the upper and lower flanges. The grouting liquid penetrates into the rock fissures of the flanges to form a combined support system and improve the stability of the flange rock mass. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of the rock pillar reinforcement structure in a small-clearance tunnel according to this utility model;

[0019] Figure 2 This is a schematic diagram of the steel arch frame of this utility model;

[0020] Figure 3 This is a schematic diagram of the prestressed tie rod and the prestressed tie rod of this utility model;

[0021] Figure 4 This is a side view of the prestressed tie rod of this utility model;

[0022] Figure 5 This is a schematic diagram of the steel arch frame and hollow grouting anchor rod of this utility model;

[0023] Figure 6 This is a schematic diagram of the honeycomb steel plate of this utility model.

[0024] In the diagram: 1. Pre-existing tunnel; 2. Subsequent tunnel; 3. Upper flange; 4. Lower flange; 5. Middle rock column; 6. Prestressed tie rod; 7. Hollow grouting anchor; 8. Honeycomb steel arch; 9. Regular hexagonal hole; 10. Rod body; 11. Regular octagonal axial rib; 12. Grout stop plug; 13. Steel pad; 14. Shape memory alloy pad; 15. High-temperature resistant strain gauge; 16. Expansion bolt; 17. Externally threaded rod segment; 18. Nut; 19. Steel plate. Detailed Implementation

[0025] Please see Figure 1-6 A rock pillar reinforcement structure for tunnels with small clearance includes a pilot tunnel 1, a follow-up tunnel 2, a central rock pillar 5 located between the pilot tunnel 1 and the follow-up tunnel 2, upper flanges 3 and lower flanges 4 located on the upper and lower sides of the central rock pillar 5 respectively, multiple prestressed tie rods 6 arranged in a matrix and passing through the central rock pillar 5 laterally, and honeycomb steel arch frames 8 embedded in the inner walls of the pilot tunnel 1 and the follow-up tunnel 2 respectively, and heatable shape memory tensioning components located at both ends of the prestressed tie rods 6; the honeycomb steel arch frames 8 are fitted and connected to the heatable shape memory tensioning components; the honeycomb steel arch frames 8 can uniformize the load on the rock walls on both sides of the central rock pillar 5 and optimize the stress on the rock walls on both sides of the central rock pillar 5.

[0026] The prestressed tie rod 6 includes a rod body 10, threaded rod segments 17 connected to both ends of the rod body 10, and regular octagonal axial ribs 11 provided on the outer wall of the rod body 10. The regular octagonal axial ribs 11 are formed by hot rolling or cold extrusion, and the height of the regular octagonal axial ribs 11 is 2-5mm, and the circumferential spacing is 10-20mm. The regular octagonal axial ribs 11 increase the contact area between the rod body 10 and the central rock column 5, increase the static friction between the rod body 10 and the central rock column 5, and enhance the anchoring effect of the rod body 10 on the central rock column 5 in tunnels with small clearance.

[0027] The heatable shape memory tensioning assembly includes a grout stopper 12, a steel pad 13, a shape memory alloy pad 14, multiple expansion bolts 16, and a nut 18 threadedly connected to the externally threaded rod segment 17, all sequentially fitted onto the rod body 10. The end face of the nut 18 is in close contact with the surface of the shape memory alloy pad 14. The steel pad 13 is fixed to the side wall of the central rock column 5 by multiple expansion bolts 16. The steel pad 13 is placed between the grout stopper 12 and the shape memory alloy pad 14, and fixed to the rock wall surfaces on both sides of the central rock column 5 by expansion bolts 16.

[0028] The prestressing method for the prestressed anchor rod 6 is as follows: the shape memory alloy pad 14 is heated to cause "high temperature phase" deformation and elongation. The shape memory alloy pad 14 will undergo longitudinal elongation deformation along the rod body 10. Its elongation deformation will generate compressive force on the steel pad 13. Since the steel pad 13 has been fixed to the rock walls on both sides of the central rock column 5 by expansion bolts 16, it will not be displaced after being compressed. Instead, it will generate a reaction force in the opposite direction to the compressive force. The reaction force is transmitted along the shape memory alloy pad 14 to the surface of the nut 18. The nut 18 will be subjected to thrust. Since the nut 18 is welded to the external thread rod segment 17, there is no relative displacement. Therefore, the thrust of the nut 18 will be transmitted to the rod body 10, tensioning the rod body 10. The tension value of the rod body 10 can be monitored in real time by attaching the high temperature resistant strain gauge 15 to the side surface of the shape memory alloy pad 14.

[0029] The shape memory alloy pad 14 is made of a shape memory alloy with a single-pass memory effect. The phase transition temperature of the shape memory alloy pad 14 is 60-120℃. The shape memory alloy pad 14 can be deformed at low temperature and then heated to restore the shape of the "high temperature phase". However, it cannot restore the shape of the "low temperature phase" when cooled again.

[0030] Multiple high-temperature resistant strain gauges 15 arranged in annular intervals are attached to the outer surface of the shape memory alloy pad 14. The magnitude of the prestress applied to the rod 10 is monitored in real time by connecting the high-temperature resistant strain gauges 15 attached to the side of the shape memory alloy pad 14 to the instrument.

[0031] The nut 18 and the external threaded rod segment 17 are assembled and welded together to form a whole, and the nut 18 and the external threaded rod segment 17 will not have relative displacement.

[0032] The honeycomb steel arch frame 8 includes a steel plate 19 and a plurality of regular hexagonal holes 9 arranged in a honeycomb pattern on the steel plate 19; both the shape memory alloy pad 14 and the steel pad 13 are regular hexagonal prism structures, and their cross-sectional dimensions are adapted to the regular hexagonal holes 9. The shape memory alloy pad 14 and the steel pad 13 have circular through holes in their centers for the rod body 10 to pass through; the regular hexagonal holes 9 and the edges of the shape memory alloy pad 14 engage to form an interlocking structure, which inhibits the rotation of the shape memory alloy pad 14 and the steel pad 13 and enhances the prestress transfer efficiency.

[0033] Both the pilot tunnel 1 and the follower tunnel 2 are equipped with multiple radially arranged hollow grouting anchors 7. These hollow grouting anchors 7 penetrate the upper flange 3 and the lower flange 4, and extend into the interior of both tunnels through hexagonal holes 9 in the honeycomb steel arch frame 8. The hollow grouting anchors 7 enhance the stability of the surrounding rock at the upper and lower flanges of the central rock column.

[0034] A construction method for a rock pillar reinforcement structure in a tunnel with a small clearance includes the following steps:

[0035] Step 1: The first tunnel 1 is excavated using the CD method. During construction, a rock drill is used to pre-leave installation grooves for the honeycomb-shaped steel arch frame 8 on the rock surface.

[0036] Step 2: After the initial spraying of each pilot tunnel in the first tunnel is completed, the honeycomb steel arch frame 8 is immediately embedded in the reserved groove. The two bottom feet of the steel arch frame are fixed by locking anchor rods. Then, sprayed concrete is used to fill the gap between the honeycomb steel arch frame 8 and the rock surface to ensure compaction.

[0037] Step 3: Drill holes at the center of the honeycomb steel arch frame 8 corresponding to the rock mass positions of the upper flange 3, lower flange 4, and middle rock column 5. After completion, use high-pressure air to clean the holes. Install hollow grouting anchor rods 7 on the upper flange 3 and lower flange 4. Bury the rod body 10 of the prestressed tie rod 6 in the middle rock column area (take care to protect the end of the rod body 10 on the side of the subsequent tunnel 2 so that the excavation of the subsequent tunnel 2 will not damage the rod body 10 of the prestressed tie rod 6). Install the grout stop plug, pad, and nut of the hollow grouting anchor rod 7 in sequence, as well as the grout stop plug 12 of the prestressed tie rod 6 at the middle rock column 5. Embed the steel pad 13 into the regular hexagonal hole 9 of the honeycomb steel arch frame 8 and fix it to the rock wall on the side of the first tunnel 1 with expansion bolts 16. Then install the shape memory alloy pad 14 (embedded in the regular hexagonal hole 9). Finally, tighten the nut 18 of the external thread rod section 17.

[0038] Step 4: After completing the installation of the accessories for the hollow grouting anchor rods 7 on the upper flange 3 and lower flange 4 of the pilot tunnel 1 and the prestressed tie rods 6 on the central rock column, grout the hollow grouting anchor rods 7 on the upper flange 3 and lower flange 4.

[0039] Step 5: The subsequent tunnel 2 is excavated using the same CD method as the preceding tunnel 1, with the working faces staggered by more than twice the tunnel excavation width. The installation of the honeycomb steel arch frame 8, shotcrete, hollow grouting anchor rods 7, and prestressed tie rods 6 is completed simultaneously.

[0040] Step 6: After the accessories of the prestressed tie rod 6 on the side of the rear tunnel are installed, the nuts 18 on both sides are welded and fixed to the rod body 10 using a projection welding machine to ensure that there is no relative displacement.

[0041] Step 7: After welding, the shape memory alloy pad 14 is heated by a high-frequency induction heating device to trigger the elongation deformation of its "high temperature phase". The thrust is transmitted to the nut 18 through the steel pad 13, and the tension rod 10 generates prestress. At the same time, the strain of the shape memory alloy pad 14 is monitored by the strain acquisition system to control the prestress value.

[0042] Step 8: After the prestressing of the middle rock column 5 is completed, the prestressed tie rod 6 is grouted, and finally the secondary lining of the entire cross section of the pilot tunnel 1 and the follow-up tunnel 2 is constructed.

[0043] Working process and principle: The first tunnel 1 is constructed using the CD method, with pre-reserved grooves for embedding honeycomb steel arch frames 8. After being fixed to the shotcrete through locking measures, hollow grouting anchor rods 7 and prestressed tie rods 6 rod bodies 10 are installed by drilling holes in the upper flange 3, lower flange 4, and middle rock column 5. The grout stop plug 12, steel pad 13, and shape memory alloy pad 14 are sequentially sleeved onto the rod body 10, so that the steel pad 13 is fixed to the side wall of the middle rock column 5 by expansion bolts 16. The shape memory alloy pad 14 and the regular hexagonal hole 9 of the honeycomb steel arch frame 8 form an interlocking structure. Then, the nut 18 is tightened and welded to the external threaded rod section 17. The second tunnel is constructed in the same way, with the working faces staggered by more than twice the tunnel excavation width. When prestress is applied, the shape memory alloy pad 14 is heated to 60-120℃ using a high-frequency induction heating device, causing it to undergo elongation deformation in the "high temperature phase," which generates compressive force on the fixed steel pad 13. The reaction force is transmitted to the nut 18 through the shape memory alloy pad 14, thereby tensioning the rod body 10 to generate prestress. At the same time, the strain is monitored in real time by the high-temperature strain gauge 15 and the strain acquisition system to control the prestress value. The octagonal axial ribs 11 on the outer wall of the rod 10 increase the contact area and static friction with the central rock column 5, enhancing the anchoring effect. The honeycomb steel arch frame 8, through the interlocking structure of the regular hexagonal holes 9 with the steel pad 13 and the shape memory alloy pad 14, inhibits the rotation of the steel pad 13 and the shape memory alloy pad 14, uniformly transmits the load, and optimizes the stress on the rock walls on both sides of the central rock column 5. The hollow grouting anchor rod 7 penetrates the upper flange 3 and the lower flange 4 for grouting, enhancing the stability of the surrounding rock of the upper flange 3 and the lower flange 4, and finally forming a collaborative support system of "prestressed tensioning - load homogenization of honeycomb steel arch frame 8 - grouting reinforcement", improving the shear strength and overall stability of the central rock column 5.

[0044] 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 rock pillar reinforcement structure in a tunnel with a small clearance, comprising a pilot tunnel (1), a follow-up tunnel (2), a central rock pillar (5) located between the pilot tunnel (1) and the follow-up tunnel (2), an upper flange (3) and a lower flange (4) respectively located on the upper and lower sides of the central rock pillar (5), and a plurality of prestressed tie rods (6) transversely penetrating the central rock pillar (5) and arranged in a matrix, characterized in that, It also includes honeycomb steel arch frames (8) installed on the inner walls of the first tunnel (1) and the second tunnel (2), and heatable shape memory tensioning components installed at both ends of the prestressed tie rods (6); the honeycomb steel arch frames (8) and the heatable shape memory tensioning components are fitted together.

2. The rock column strengthening structure according to claim 1, wherein The prestressed tie rod (6) includes a rod body (10), externally threaded rod segments (17) connected to both ends of the rod body (10), and a regular octagonal axial rib (11) provided on the outer wall of the rod body (10); the height of the regular octagonal axial rib (11) is 2-5mm, and the circumferential spacing is 10-20mm.

3. The rock column reinforcement structure of claim 2, wherein, The heatable shape memory tensioning assembly includes a grout stop plug (12), a steel pad (13), a shape memory alloy pad (14), a plurality of expansion bolts (16) sequentially sleeved on the rod body (10), and a nut (18) threadedly connected to the external threaded rod segment (17); the end face of the nut (18) is in close contact with the surface of the shape memory alloy pad (14); the steel pad (13) is fixed to the side wall of the central rock column (5) by a plurality of expansion bolts (16).

4. The rock column reinforcement structure of claim 3, wherein, The shape memory alloy pad (14) is made of a shape memory alloy with a single-pass memory effect, and the phase transition temperature of the shape memory alloy pad (14) is 60-120℃.

5. The center rock column strengthening structure according to claim 3, wherein The outer surface of the shape memory alloy pad (14) is provided with multiple annularly spaced high-temperature strain gauges (15).

6. The rock column strengthening structure of claim 3, wherein The nut (18) is welded to the external threaded rod segment (17).

7. The center rock column strengthening structure according to claim 3, wherein The honeycomb steel arch frame (8) includes a steel plate (19) and a plurality of regular hexagonal holes (9) arranged in a honeycomb pattern on the steel plate (19); the shape memory alloy pad (14) and the steel pad (13) are both regular hexagonal prism structures, and their cross-sectional dimensions are adapted to the regular hexagonal holes (9). The shape memory alloy pad (14) and the steel pad (13) have a circular through hole in the center for the rod body (10) to pass through; the regular hexagonal holes (9) and the shape memory alloy pad (14) interlock with each other to form an interlocking structure.

8. The method according to claim 7, wherein Both the pre-tunnel (1) and the rear tunnel (2) are equipped with a plurality of radially arranged hollow grouting anchor rods (7); the plurality of hollow grouting anchor rods (7) penetrate the upper flange (3) and the lower flange (4), and extend into the interior of the pre-tunnel (1) and the rear tunnel (2) through the regular hexagonal holes (9) of the honeycomb steel arch frame (8).

Images