A rock column reinforcement method suitable for shallow-buried, bias-loaded, and ultra-small-spacing tunnels

Abstract

The present invention discloses a method for reinforcing a rock pillar in a shallow-buried, biased, and ultra-small-clearance tunnel, belonging to the technical field of tunnel construction. The method comprises the following steps: S1: excavating a pilot pit near the rock pillar in a shallow-buried, biased, and ultra-small-clearance tunnel, and providing initial support to the pilot pit; S2: installing a limited prestressed anchor in the upper reinforcement area of the rock pillar, and installing prestressed curved steel plates on both sides of the pilot pits near the rock pillar. The limited prestressed anchor penetrates the rock pillar and the two prestressed curved steel plates, and the ends of the limited prestressed anchor are respectively anchored to the corresponding prestressed curved steel plates; and S3: installing a small grouting conduit in the lower reinforcement area of the rock pillar. The method can reduce the asymmetric horizontal deformation problem of the rock pillar in shallow-buried, biased, and ultra-small-clearance tunnels, thereby achieving better support and reinforcement effects.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a method for reinforcing a rock column in a shallow-buried, biased, and ultra-small-clearance tunnel. Background Art

[0002] In shallow, biased, and short-distance tunnel construction, low-prestressed anchor bolts and small grouting tubes are often used to reinforce the intermediate rock pillars. Current low-prestressed anchor support requires drilling holes into the intermediate rock pillars, applying prestress, and finally grouting to seal them. Furthermore, anchor bolts must be used in conjunction with small grouting tubes when reinforcing the intermediate rock pillars, making construction more complex.

[0003] Furthermore, the commonly used hollow grouting anchor rods evolved from self-propelled anchor rods. Compared to ordinary mortar anchor rods, they offer significant improvements, such as being equipped with a backing plate, grouting plug, and anchor head, and employing a construction process of anchoring first and then grouting. However, the currently used hollow grouting anchor rods are overly simplified for ease of use, resulting in the following significant drawbacks:

[0004] a. When hollow grouting anchor rods are constructed at an elevation angle, the existing grouting process cannot completely exhaust the air in the anchor hole, giving the illusion of full grouting and forming a cavity in the anchor hole. The incomplete grouting is particularly serious when an intermittent grouting pump is used.

[0005] b. Due to the problem of air not being completely exhausted from the anchor hole in hollow grouting anchor rods, in actual use, in order to improve the grouting effect, material suppliers sometimes drill several small holes with a diameter of about 6mm in the anchor rod body. Although this can improve the loose surrounding rock structure during high-pressure grouting, it still does not solve the exhaust problem under normal conditions, and the actual effect is still limited. Drilling holes in the anchor rod body also has the consequence of reducing the rod body strength. The actual strength of this type of anchor rod currently in use is only equivalent to that of HRB335 rebar with a diameter of 16, which is far below the recognized range of system anchor rods. If the stress concentration at the drilled hole is taken into account, the actual strength is far below the high stress and high strength range of system anchor rods.

[0006] C. Due to inherent design flaws in the hollow grouting anchor and inappropriate grouting techniques, grouting at elevated angles was difficult. This created a disconnect between design and construction, leading to the construction company using cement rolls as an anchoring agent instead of grouting.

[0007] d. According to the flexible support theory, the surrounding rock is allowed to develop moderately in the plastic zone after excavation to utilize the self-stabilizing ability of the surrounding rock itself. The hollow anchor rod body is mostly made of carbon steel, using seamless steel pipes and then cold extruded. This process will make the yield strength of the rod body worse, the elongation lower, and the material harder, making it unable to adapt to the surrounding rock, especially the larger plastic deformation of grade II and III surrounding rock, reducing the anchoring strength. Summary of the Invention

[0008] In response to the above-mentioned problems, the present invention aims to provide a method for reinforcing the middle rock pillars in shallow-buried biased and ultra-small clearance tunnels, which can reduce the asymmetric horizontal deformation problem of the middle rock pillars in shallow-buried biased and ultra-small clearance tunnels and has better support and reinforcement effects.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for reinforcing a rock column in a shallow-buried, biased, ultra-small-clearance tunnel is characterized by comprising the following steps:

[0011] S1: Excavate a pilot pit for a shallow-buried, bias-loaded, ultra-small-spacing tunnel close to the rock pillar and provide initial support for the pilot pit.

[0012] S2: A limited prestressed anchor rod is applied in the upper reinforcement area of the middle rock column, and a prestressed curved steel plate is applied on one side of the two pilot pits close to the middle rock column. The limited prestressed anchor rod passes through the middle rock column and the two prestressed curved steel plates, and both ends of the limited prestressed anchor rod are anchored to corresponding prestressed curved steel plates respectively;

[0013] S3: A small grouting tube is constructed in the lower reinforcement area of the middle rock column.

[0014] Furthermore, there are two position-limiting prestressed anchor rods described in step S2, and the two position-limiting prestressed anchor rods are respectively located at the arch waist and the tunnel side wall.

[0015] Furthermore, the limiting prestressed anchor rod includes an outer sleeve, two steel strands are symmetrically arranged in the outer sleeve, and two sleeve baffles are symmetrically arranged on the inner wall of the outer sleeve, each of the sleeve baffles is sleeved outside the corresponding steel strand, and a limiting assembly is provided between the steel strand and the corresponding sleeve baffles.

[0016] Furthermore, the limiting assembly includes a pushing rod sleeved outside the steel strand, and the pushing rod is located on the outside of the sleeve baffle; three arc-shaped connecting rods are symmetrically fixed to one end of the pushing rod close to the sleeve baffle, and the three arc-shaped connecting rods are movable through the sleeve baffle, and a pushing rod limiting plate is fixed to one end of the three connecting rods away from the pushing rod, and the pushing rod limiting plate is fixedly connected to the steel strand and the ends of the three connecting rods, and a first return spring is also fixed between the pushing rod limiting plate and the sleeve baffle.

[0017] Furthermore, a locking assembly is provided between the pushing rod and the outer sleeve, and the locking assembly includes multiple groups of conical blocks fixed on the outer side wall of the pushing rod, each group of the conical blocks has three, and the three conical blocks are symmetrically fixed on the outer side wall of the pushing rod, and three locking rods are symmetrically provided between two adjacent groups of conical blocks, and multiple sleeve reserved holes matching the locking rods are opened on the outer sleeve, and a locking rod limiting spring is provided between the inner side wall of the sleeve reserved hole and the end of the locking rod.

[0018] Furthermore, the angle between the locking rod and the steel strand is 45 degrees.

[0019] Furthermore, a stabilizing assembly is provided between the two pushing rod limit plates, and the stabilizing assembly includes three arc-shaped baffles sleeved on the outside of the two pushing rod limit plates, and the three arc-shaped baffles are symmetrically arranged, and a second return spring is fixedly provided on the inner side wall of each arc-shaped baffle, and a second return spring support rod is sleeved on the outside of each second return spring, and one end of the three second return spring support rods passes through the corresponding arc-shaped baffles and is fixedly connected to the inner side wall of the outer sleeve, and the other end of the three second return spring support rods is fixedly connected at the center position of the three arc-shaped baffles.

[0020] Furthermore, the small grouting conduit described in step S3 is applied horizontally and forwardly at an angle of 45 degrees to the tunnel axis.

[0021] The beneficial effects of the present invention are:

[0022] 1. The method for reinforcing the middle rock column in the present invention adopts a method for reinforcing the upper part of the middle rock column by using a limited prestressed anchor rod and a prestressed bent steel plate, and adopts a method for reinforcing the lower part of the middle rock column by using a small grouting pipe. This method adopts different reinforcement methods for different partitions of the middle rock column in a targeted manner according to the stress characteristics and deformation characteristics of the middle rock column in the ultra-small clearance tunnel. The method is convenient to construct, and can better ensure the stability of the middle rock column, change the stress characteristics of the middle rock column, reduce the deformation of the middle rock column, and ensure the stability of the tunnel construction process. It is particularly suitable for the protection and reinforcement of the middle rock column in the middle tunnel section of a shallow-buried biased ultra-small clearance tunnel, and has good economic benefits.

[0023] 2. In the reinforcement method for the middle rock column of the present invention, the upper reinforcement area of the middle rock column is reinforced by limited prestressed anchor rods and prestressed bent steel plates. Compared with low prestressed anchor rods, limited prestressed anchor rods can usually apply greater prestress. Therefore, the use of limited prestressed anchor rods and prestressed bent steel plates can actively protect and reinforce the middle rock column, rather than passively reinforce it like low prestressed anchor rods. When the curvature of the prestressed bent steel plate is slightly larger than the curvature of the rock column in the tunnel, the middle position of the steel plate can first contact the middle rock column during installation. In the subsequent process of applying prestress, the remaining parts of the prestressed bent steel plate also gradually contact the middle rock column, so that the stress on the middle rock column is more uniform, and finally a drum-shaped reinforcement area is formed at the reinforcement location. The reinforcement area is clamped by the bent steel plate, and its horizontal deformation is smaller, and its vertical bearing capacity is improved on the side. At the same time, the height of the reinforcement area is about twice the width, similar to a pillar, which can better transmit the upper load. The reinforced area is subjected to the clamping force of the prestressed curved steel plate. If the curvature of the prestressed curved steel plate is the same as that of the rock pillar in the tunnel, uneven force may be applied to the rock pillar.

[0024] 3. The limited prestressed anchor rod in the present invention has a steel strand as the main reinforcement component and does not adopt grouting reinforcement, which can avoid problems such as incomplete grouting during the grouting process, and can also avoid problems such as defects in the design of hollow grouting anchor rods and unreasonable grouting technology. After the two ends of the steel strand are subjected to tension, the steel strand drives the jacking rod to slide, and the tapered block on the sliding rod slides and squeezes the locking rod, which pushes the outer sleeve outward and inserts into the surrounding rock. After the steel strand and the jacking rod slide for a certain distance, they are restricted by the jacking rod limit plate and cannot continue to slide. At the same time, the locking rod drills into the surrounding rock to reach the maximum depth and finally engages with the surrounding rock. The rock is fixed together, which can improve the stability of the limited prestressed anchor rod; when the jacking rod limit plate moves close to the sleeve baffle, the position between the two jacking rod limit plates is vacant, and the arc baffle shrinks toward the center under the action of the second return spring. The three arc baffles contact each other to form a hollow cylindrical structure, and are located between the two jacking rod limit plates to prevent the jacking rod limit plates from rebounding and affecting the reinforcement effect, thereby ensuring that the limiting component in the middle of the limited prestressed anchor rod can be in the middle position in the middle rock column, and the support structure will not be pulled to one side due to uneven deformation on both sides of the biased tunnel, thereby affecting the reinforcement effect.

[0025] 4. The limiting component of the limiting prestressed anchor rod in the present invention can ensure that the deformation difference of the surrounding rock on both sides of the steel strand is small. For example, in a biased tunnel, the deformation on both sides of the middle rock column is uneven, which will cause the steel strand to be pulled to one side and offset, resulting in poor final reinforcement effect. The limiting component of the limiting prestressed anchor rod in the present invention can limit the large displacement of the steel strand, thereby ensuring the reinforcement effect of the middle rock column under biased conditions; it can also provide greater prestress in engineering, avoiding the problem of reduced anchor rod strength when the surrounding rock undergoes large deformation of low prestressed anchor rods, and is suitable for a variety of deformation conditions.

[0026] 5. In the reinforcement method of the middle rock column of the present invention, the lower reinforcement area of the middle rock column is reinforced by a small grouting tube. The small grouting tube is horizontally driven at an angle of 45° forward, which can improve the mechanical parameters of the surrounding rock. At the same time, the oblique driving can also reinforce the lower position of the front middle rock column in advance. When the upper position of the middle rock column in the subsequent cycle is reinforced, the slurry in the grouting reinforcement area of the lower part of the middle rock column has solidified and reached the design strength, which can better bear the upper load. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the method for reinforcing a rock column in Example 1 of the present invention.

[0028] Figure 2 This is the front view of the rock column reinforcement structure in Example 1 of the present invention.

[0029] Figure 3 This is a side view of the rock column reinforcement structure in Example 1 of the present invention.

[0030] Figure 4 Schematic diagram of the internal structure of the position-limiting prestressed anchor rod in the second embodiment of the present invention.

[0031] Figure 5 For the present invention Figure 4 A partial enlarged view of the structure of part A.

[0032] Figure 6 For the present invention Figure 4 A partial enlarged view of the structure of part B.

[0033] Figure 7 For the present invention Figure 4 Cross-section in the aa direction.

[0034] Figure 8 For the present invention Figure 4 Cross-sectional view in the middle bb direction.

[0035] Figure 9 For the present invention Figure 4 Cross-sectional view in the middle CC direction.

[0036] Figure 10 For the present invention Figure 4 Cross-section in the dd direction.

[0037] Figure 11 For the present invention Figure 10 Cross-section in the ee direction.

[0038] Figure 12 For the present invention Figure 11 The middle arc baffle moves to the center of the outer sleeve and then forms a hollow rod-shaped structure with a closed outer side wall.

[0039] Figure 13 Schematic diagram of the rock column reinforcement structure of the asymmetric tunnel in Example 3 of the present invention.

[0040] Among them: 1-middle rock column, 11-upper reinforcement area, 12-lower reinforcement area, 2-limited prestressed anchor rod, 21-steel strand, 22-locking rod, 221-locking rod limiting spring, 23-jacking rod, 231-conical block, 232-jacking rod limiting plate, 233-connecting rod, 24-arc baffle, 25-first return spring, 26-outer sleeve, 261-sleeve reserved hole, 262-sleeve baffle, 27-second return spring, 271-second return spring support rod, 3-prestressed bent steel plate, 4-grouting small catheter, 41-first hole grouting small catheter drilling hole, 42-later hole grouting small catheter drilling hole. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0042] Example 1:

[0043] As attached Figure 1 As shown, a method for reinforcing rock pillars in shallow-buried, biased, and ultra-small-clearance tunnels includes the following steps:

[0044] S1: excavate a pilot pit of a shallow-buried biased ultra-small clearance tunnel close to the middle rock column 1, and apply initial support to the pilot pit; the initial support method of the pilot pit adopts the initial support method in the existing technology, which will not be described in detail in this invention.

[0045] S2: A limited prestressed anchor rod 2 is applied in the upper reinforcement area 11 of the middle rock column 1, and a prestressed curved steel plate 3 is applied on one side of the two pilot pits close to the middle rock column 1. The limited prestressed anchor rod 2 passes through the middle rock column 1 and the two prestressed curved steel plates 3, and the two ends of the limited prestressed anchor rod 2 are respectively anchored to the corresponding prestressed curved steel plates 3;

[0046] As attached Figure 2 and 3As shown, there are two limiting prestressed anchor rods 2, and the two limiting prestressed anchor rods 2 are respectively located at the arch waist and the tunnel side wall. First, a hole is drilled on the middle rock column 1. The diameter of the hole is slightly larger than the diameter of the limiting prestressed anchor rod 2. The two holes are arranged vertically, and pass through the middle rock column horizontally from the arch waist and the tunnel side wall respectively. After the limiting prestressed anchor rod 2 passes through the drill hole, it passes through the reserved hole on the prestressed bent steel plate 3 to apply prestress to the limiting prestressed anchor rod 2 for locking.

[0047] The curvature of the prestressed curved steel plate 3 is slightly larger than that of the rock column 1 in the tunnel. The purpose is to ensure that the prestressed curved steel plate 3 can evenly reinforce the rock column 1 after anchoring, avoiding uneven stress and affecting the reinforcement effect.

[0048] The specific operation of this step is: after completing the initial support of the pilot tunnel in step S1, measure the deformation of the tunnel surrounding rock after the initial support is completed, and design different tensioning lengths of the limited prestressed anchor rods 2 according to the different deformation degrees of the left and right tunnels of the biased tunnel; in actual application, when the deformation of one side is greater than that of the other side, the design value of the tensioning length of one side can be appropriately increased to balance the deformation of the surrounding rocks on both sides.

[0049] After the prestressed tensioning design is completed, a limited prestressed anchor rod 2 and a prestressed bent steel plate 3 are applied to the upper reinforcement area 11 of the middle rock column 1. The limited prestressed anchor rod 2 is a through-type design and the ends on both sides are anchored on the prestressed bent steel plate 3.

[0050] S3: A small grouting pipe 4 is installed in the lower reinforcement area 12 of the middle rock column 1; the small grouting pipe 4 is installed horizontally and forward at a 45-degree angle to the tunnel axis;

[0051] There are grouting holes distributed on the wall of the grouting small tube 4. First, a hole is drilled on the middle rock column 1, and the grouting small tube 4 is driven into the drill hole and then grouting is injected to seal the hole. The length of the grouting small tube 4 is determined according to the depth of the drill hole; the limiting prestressed anchor rod 2, prestressed bent steel plate 3 and grouting small tube 4 form a middle rock column reinforcement structure.

[0052] During the construction of the grouting small conduit 4, the grouting small conduit 4 includes a leading hole grouting small conduit and a trailing hole grouting small conduit. The leading hole grouting small conduit and the trailing hole grouting small conduit are arranged in an up-down staggered manner. The leading hole grouting small conduit is driven forward at an angle of 45° from the leading hole grouting small conduit drilling hole 41, and the trailing hole grouting small conduit is driven forward at an angle of 45° from the trailing hole grouting small conduit drilling hole 42. The drilling positions of the leading hole grouting small conduit drilling hole and the trailing hole grouting small conduit drilling hole 42 are shown in the attached figure. Figure 3 shown.

[0053] In practice, based on the layout results, a hole is drilled into the intermediate rock pillar 1. The drilling depth should be determined based on the thickness of the intermediate rock pillar 1, and the drilling direction should be horizontal and forward at a 45° angle to the tunnel axis. After drilling is completed, a small grouting pipe 4 is installed and grouting is then carried out. Before grouting, a water pressure test must be conducted to check whether the mechanical equipment and pipeline connections are functioning properly. To maximize equipment efficiency and speed up construction, group grouting can be used, with 3 to 5 pipes at a time. 42.5-grade cement is used, with a slurry water-cement ratio of 1:1. The grouting pressure is controlled between 0.5 and 1 MPa. During the grouting process, the pressure should be increased gradually, with a certain injection volume. When the design final pressure of 1.0 MPa is reached, the grouting rate is generally 20 to 30 L / min, and injection is continued for at least 10 minutes. When the groundwater level is high, a cement + water glass slurry is injected under pressure, with a cement slurry to water glass volume ratio of 1:0.5 and a water glass concentration of 35 degrees Baume. The grouting pressure remains constant. During the grouting process, the changes in the grouting pump discharge volume should be observed at any time, and the grouting situation should be analyzed to prevent pipe blockage, slurry leakage, and slurry leakage.

[0054] The specific principle behind the intermediate rock column reinforcement structure used in the intermediate rock column reinforcement method of the present invention is as follows: Under normal circumstances, the stress on intermediate rock column 1 is transmitted from the upper load. Due to the Poisson effect, the middle portion of intermediate rock column 1 is subjected to vertical compression from the upper load, resulting in horizontal deformation. Simultaneously, the lower portion of intermediate rock column 1 is also subjected to vertical deformation due to the upper load. Therefore, targeted reinforcement of these two areas can improve the bearing capacity of intermediate rock column 1.

[0055] The upper reinforcement area 11 of the middle rock column 1 is reinforced by a limited prestressed anchor rod 2 and a prestressed curved steel plate 3. Compared with a low prestressed anchor rod, a limited prestressed anchor rod 2 can usually apply a larger prestress. Therefore, the use of a limited prestressed anchor rod 2 and a prestressed curved steel plate 3 can actively protect and reinforce the middle rock column 1, rather than passively reinforce it like a low prestressed anchor rod. When the curvature of the prestressed curved steel plate 3 is slightly larger than the curvature of the rock column 1 in the tunnel, the middle position of the prestressed curved steel plate 3 can first contact the middle rock column 1 during installation. In the subsequent process of applying prestress, the remaining parts of the prestressed curved steel plate 3 also gradually contact the middle rock column 1, so that the stress on the middle rock column 1 is more evenly distributed, and finally a drum-shaped reinforcement area is formed at the reinforcement location. This reinforced area is clamped by the prestressed curved steel plate 3, minimizing horizontal deformation and enhancing its vertical bearing capacity. Furthermore, the height of the upper reinforced area 11 is approximately twice its width, similar to a pillar, which better transmits the upper load. This upper reinforced area 11 is clamped by the prestressed curved steel plate 3. If the prestressed curved steel plate 3 and the tunnel rock column 1 have the same curvature, uneven stress on the rock column 1 may occur.

[0056] The lower reinforcement area 12 of the middle rock column 1 is reinforced by a small grouting tube 4, and the small grouting tube 4 is applied horizontally forward at a 45-degree angle to the tunnel axis, which can improve the mechanical parameters of the surrounding rock. At the same time, the oblique installation can also reinforce the lower reinforcement area 12 of the front middle rock column 1 in advance. When the upper reinforcement area 11 of the middle rock column 1 in the subsequent cycle is reinforced, the grouting slurry in the lower reinforcement area 12 of the middle rock column 1 has solidified and reached the design strength, which can better bear the upper load.

[0057] The grouting conduit 4 reinforces the central rock column 1 similarly to conventional anchor bolts. When the surrounding rock deforms, its support resistance limits further deformation. After grout is injected into the central rock column 1 through the grouting conduit 4, the grout diffuses into the surrounding weak and fractured rock fissures, forming a reinforced area with strong integrity and high rigidity.

[0058] Example 2:

[0059] In the second embodiment, a specific structure of a limited prestressed anchor rod 2 is provided, as shown in the attached Figure 4-12 As shown, the limiting prestressed anchor rod 2 includes an outer sleeve 26, and two steel strands 21 are symmetrically arranged in the outer sleeve 26. The steel strands 21 can move in the outer sleeve 26. The lengths of the steel strands 21 and the outer sleeve 26 are determined according to the width of the middle rock column 1 and are slightly larger than the width of the middle rock column 1 to ensure that both ends can be anchored on the prestressed curved steel plate 3; two sleeve baffles 262 are symmetrically provided on the inner wall of the outer sleeve 26, and each of the sleeve baffles 262 is sleeved on the outside of the corresponding steel strands 2, and a limiting component is provided between the steel strands 2 and the corresponding sleeve baffles 262.

[0060] The limiting assembly includes a pushing rod 23 sleeved on the outside of the steel strand 2, and the pushing rod 23 is located on the outside of the sleeve baffle 262, that is, the pushing rod 23 is located on a side of the sleeve baffle 262 away from its center; three arc-shaped connecting rods 233 are symmetrically fixed to one end of the pushing rod 23 close to the sleeve baffle 262, and the three arc-shaped connecting rods 233 are movable through the sleeve baffle 262. The three connecting rods 233 form a circular structure with the same inner diameter as the inner diameter of the pushing rod 23, and a gap is left between two adjacent connecting rods 233. Three through holes matching the connecting rods 233 are opened on the sleeve baffle 262, so that the connecting rod 233 and the pushing rod 23 can move axially along the outer sleeve 26. The mutual cooperation between the sleeve baffle 26 and the connecting rod 233 can limit the moving direction of the pushing rod 23 to prevent the pushing rod 23 from rotating during the movement.

[0061] The three connecting rods 233 are fixed with a pushing rod limit plate 232 at one end away from the pushing rod 23, and the pushing rod limit plate 232 is fixedly connected to the ends of the steel strand 21 and the three connecting rods 233. The pushing rod limit plate 232 connects the three connecting rods 233 and the corresponding steel strands 21 to form an integral structure. When the steel strand 21 is pulled, the pushing rod limit plate 232, the pushing rod 23 and the connecting rod 233 can be driven to move synchronously at the same time; a first return spring 25 is also fixed between the pushing rod limit plate 232 and the sleeve baffle 262. There are three first return springs 25, which are respectively located on the outside of the three connecting rods 233. When there is no force, the steel strand 21 and the pushing rod 23 can be prevented from sliding outward under the action of the first return spring 25.

[0062] Furthermore, a locking assembly is provided between the jacking rod 23 and the outer sleeve 26, and the locking assembly includes a plurality of groups of tapered blocks 231 fixed on the outer side wall of the jacking rod 23, each group of the tapered blocks 231 has three, and the three tapered blocks 231 are symmetrically fixed on the outer side wall of the jacking rod 23, and three locking rods 22 are symmetrically provided between two adjacent groups of tapered blocks 231, and the three locking rods 22 are respectively located between two axially adjacent tapered blocks 231. The outer sleeve 26 is provided with a plurality of sleeve pre-holes 261 that match the locking rod 22. The angle between the sleeve pre-holes 261 and the axial direction of the steel strand 2 is 45 degrees, so that the angle between the locking rod 22 and the axial direction of the steel strand 2 is also 45 degrees. A locking rod limit spring 221 is provided between the inner side wall of the sleeve pre-hole 261 and the end of the locking rod 22 to prevent the locking rod 22 from sliding out of the sleeve pre-hole 261 when not in use. When the steel strand 23 is stretched outward, the jacking rod 23 is stretched accordingly, and the conical block 231 moves outward synchronously, thereby squeezing and pushing the locking rod 22 out of the sleeve pre-hole 261 and inserting it into the middle rock column 1. The end of the locking rod 22 close to the middle rock column 1 is a conical structure, which is convenient for insertion into the middle rock column 1.

[0063] Furthermore, a stabilizing assembly is provided between the two ejector rod limit plates 232, and the stabilizing assembly includes three arc-shaped baffles 24 which are sleeved on the outside of the two ejector rod limit plates 232. The three arc-shaped baffles 24 are symmetrically arranged to form a circular structure. A second return spring 27 is fixedly provided on the inner side wall of each arc-shaped baffle 24. When the ejector rod limit plate 232 is located inside the three arc-shaped baffles 24, the second return spring 27 is in a stretched state, and the two ejector rod limit plates 232 are respectively located on both sides of the second return spring 27. Each of the second return springs 27 is sleeved with a second return spring support rod 271, and one end of the three second return spring support rods 271 passes through the corresponding arc baffles 24, and the arc baffles 24 are provided with through holes for the second return spring support rods 271 to pass through, and the second return spring support rods 271 are fixedly connected to the inner side wall of the outer sleeve 26, and the other ends of the three second return spring support rods 271 are fixedly connected at the center position of the three arc baffles 24. The point where one end away from the arc baffle 24 is fixedly connected to the three arc baffles 24 is also fixedly connected. When the two push rod limit plates 232 are pulled outward to the outside of the arc baffle 24, the three arc baffles 24 move toward the center under the reset action of the second reset spring 27. The two adjacent arc baffles 24 fit together to form a hollow rod structure with a closed outer wall, and the two ends of the hollow rod structure are respectively against the two push rod limit plates 232, which can prevent the push rod limit plates 232 and the push rod 23 from rebounding, thereby improving the reinforcement effect.

[0064] The working principle of the limited prestressed anchor rod 2 in the present invention is as follows: after the initial support of the guide pits on both sides of the middle rock column 1 is completed, the ends of the two steel strands 21 are tensioned according to the designed tensioning length, and the two steel strands 21 should be tensioned at the same time. When tensioning the steel strands 21, the jacking rod 23 is stretched accordingly, and the conical block 231 moves outward synchronously, and the locking rod 22 pushes out the outer sleeve 26 and inserts into the surrounding rock. After the steel strand 21 and the jacking rod 23 slide for a certain distance, they are restricted by the jacking rod limit plate 232 and cannot continue to slide. At the same time, the locking rod 22 drills into the surrounding rock to reach the maximum depth and is finally fixed to the surrounding rock, which can improve the stability of the limited prestressed anchor rod 2; when the jacking rod limit plate 232 moves close to the sleeve baffle 262, the jacking rod limit plate 232 is released from the arc baffle 2 4 slides out, and the position between the two jacking rod limit plates 232 is vacant. The arc baffle 24 contracts toward the center under the action of the second return spring 27. The three arc baffles 24 contact each other to form a hollow cylindrical structure, and are located between the two jacking rod limit plates 232 to prevent the jacking rod limit plates 232 from rebounding and affecting the reinforcement effect, thereby ensuring that the limiting component in the middle of the limited prestressed anchor rod 2 can be located in the middle position of the middle rock column 1, and the support structure will not be pulled to one side due to uneven deformation on both sides of the biased tunnel, thereby affecting the reinforcement effect.

[0065] Example 3:

[0066] The method for reinforcing the rock column in the first embodiment of the present invention and the position-limited prestressed anchor rod 2 in the second embodiment can also be used in the construction of asymmetric tunnels, as shown in the attached drawings. Figure 13 As shown, the reinforcement method and the operation of the position-limiting prestressed anchor rod 2 are the same as those in the first and second embodiments.

[0067] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for reinforcing rock pillars in shallow-buried, bias-loaded, and ultra-small-spacing tunnels, characterized in that: The following steps are included: S1: Excavate a pilot pit for a shallow-buried, biased, ultra-small-spacing tunnel close to the middle rock pillar (1), and provide initial support for the pilot pit; S2: A limited prestressed anchor rod (2) is applied in the upper reinforcement area (11) of the middle rock column (1), and prestressed curved steel plates (3) are applied on both sides of the two guide pits close to the middle rock column (1), the limited prestressed anchor rod (2) passes through the middle rock column (1) and the two prestressed curved steel plates (3), and both ends of the limited prestressed anchor rod (2) are anchored on the corresponding prestressed curved steel plates (3); S3: A small grouting pipe (4) is installed in the lower reinforcement area (12) of the middle rock column (1); The limiting prestressed anchor rod (2) includes an outer sleeve (26), two steel strands (21) are symmetrically arranged in the outer sleeve (26), and two sleeve baffles (262) are symmetrically arranged on the inner wall of the outer sleeve (26), each of the sleeve baffles (262) is sleeved outside the corresponding steel strand (21), and a limiting component is provided between the steel strand (21) and the corresponding sleeve baffles (262); The limiting assembly includes a push rod (23) sleeved outside the steel strand (21), and the push rod (23) is located outside the sleeve baffle (262); three arc-shaped connecting rods (233) are symmetrically fixed to one end of the push rod (23) close to the sleeve baffle (262), and the three arc-shaped connecting rods (233) are movable through the sleeve baffle (262), and a push rod limiting plate (232) is fixed to one end of the three connecting rods (233) away from the push rod (23), and the push rod limiting plate (232) is fixedly connected to the steel strand (21) and the ends of the three connecting rods (233), and a first return spring (25) is also fixed between the push rod limiting plate (232) and the sleeve baffle (262); A stabilizing assembly is provided between the two push rod limit plates (232), and the stabilizing assembly includes three arc-shaped baffles (24) sleeved outside the two push rod limit plates (232). The three arc-shaped baffles (24) are symmetrically arranged, and a second return spring (27) is fixedly provided on the inner wall of each arc-shaped baffle (24). A second return spring support rod (271) is sleeved outside each second return spring (27), and one end of the three second return spring support rods (271) passes through the corresponding arc-shaped baffles (24) and is fixedly connected to the inner wall of the outer sleeve (26). The other ends of the three second return spring support rods (271) are fixedly connected at the center position of the three arc-shaped baffles (24).

2. The method for reinforcing rock pillars in shallow-buried, bias-loaded, and ultra-small-spacing tunnels according to claim 1 is characterized by: There are two position-limiting prestressed anchor rods (2) described in step S2, and the two position-limiting prestressed anchor rods (2) are respectively located at the arch waist of the tunnel and the tunnel side wall.

3. The method for reinforcing rock pillars in shallow-buried, bias-loaded, and ultra-small-spacing tunnels according to claim 1 is characterized by: A locking assembly is further provided between the jacking rod (23) and the outer sleeve (26), and the locking assembly includes a plurality of groups of conical blocks (231) fixed on the outer side wall of the jacking rod (23), each group of the conical blocks (231) has three, and the three conical blocks (231) are symmetrically fixed on the outer side wall of the jacking rod (23), and three locking rods (22) are symmetrically provided between two adjacent groups of conical blocks (231), and a plurality of sleeve reserved holes (261) matching the locking rod (22) are opened on the outer sleeve (26), and a locking rod limit spring (221) is provided between the inner side wall of the sleeve reserved hole (261) and the end of the locking rod (22).

4. The method for reinforcing rock pillars in shallow-buried, bias-loaded, and ultra-small-spacing tunnels according to claim 3 is characterized by: The angle between the locking rod (22) and the steel strand (21) is 45 degrees.

5. The method for reinforcing rock pillars in shallow-buried, bias-loaded, and ultra-small-spacing tunnels according to claim 1 is characterized by: The grouting small conduit (4) described in step S3 is applied horizontally and forwardly at an angle of 45 degrees to the tunnel axis.

Images