Prefabricated tunnel prestressed anchor rod and its manufacturing method and use method

Abstract

The present invention provides a prefabricated tunnel prestressed anchor rod and its manufacturing method and use method, wherein the anchor rod comprises an anchor rod body, wherein the anchor rod body comprises an unconstrained section and a prestressed section arranged in sequence; a steel casing is provided on the outer surface of the anchor rod body of the prestressed section, wherein holes are provided on the steel casing, and a filling material is provided between the steel casing and the anchor rod body, wherein the filling material is filled into the holes after prestress is applied to the anchor rod body on a tensioning pedestal, and the filling material is a material whose material structure is destroyed after power is applied; sleeves are provided at both ends of the steel casing, and a grouting plug for sealing is provided in the opening of the sleeve. The prestressed anchor rod of the present invention can be directly installed and used on site, and prestress can be applied after the filling material structure is destroyed. No special equipment is required, the operation is simple, and the prestressed state is well maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnels and underground engineering, and in particular to a prefabricated tunnel prestressed anchor rod and a manufacturing method and a use method thereof. Background Art

[0002] my country is currently progressing from a "transportation powerhouse" to a "transportation powerhouse." The transportation industry is booming, and the achievements in tunnel engineering are attracting worldwide attention. However, as we advance to higher levels, the challenges faced in tunnel construction are becoming increasingly prominent. Faults, soft rock, expansive rock, goafs, karst formations, and other factors pose significant challenges to tunnel structural safety. As part of the tunnel support structure, anchor rods offer significant technical and economic advantages and are adaptable to diverse working conditions. When faced with engineering challenges such as large soft rock deformation and rockbursts, researchers and designers often recommend the use of prestressed anchor rods, whose superior support properties have been widely recognized by the academic community.

[0003] Currently, the main construction method for implementing prestressed anchor bolting involves drilling and installing the anchor bolt, grouting the anchoring section, and once the grout is fully filled. An anchor puller is then placed over the anchor head, and a steel plate and nut are added to the end of the anchor head. After securing the grout, prestressing begins. After prestressing to the design requirement using the anchor puller, the tension is maintained for a period of time. The anchor bolt is then locked in place by tightening the steel plate and nut at the base of the anchor head with a torque wrench. The steel plate and puller are then removed, the excess anchor head is cut off, and the hole is sealed, completing the anchor bolting. This construction method presupposes a flat surface, but tunnels are arched, requiring pre-fabrication of the surface. Furthermore, prestressing requires a platform. While this approach is feasible for anchor bolts with horizontal or upward axes, it is extremely difficult to implement for anchor bolts within the arch crown, making quality and efficiency difficult to guarantee, and posing significant safety risks. Summary of the Invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide a prefabricated tunnel prestressed anchor rod and its manufacturing method and use method, so as to solve the problems of complex operation, difficult operation and difficult to ensure construction quality during the construction of existing tunnel prestressed anchor rods.

[0005] According to a first aspect of the present invention, there is provided a prefabricated tunnel prestressed anchor rod, comprising an anchor rod body, wherein the anchor rod body comprises an unconstrained section and a prestressed section arranged in sequence;

[0006] The anchor rod body of the prestressed section is covered with a steel casing, the steel casing is provided with holes, and a filling material is provided between the steel casing and the anchor rod body. The filling material is filled into the holes after prestress is applied to the anchor rod body on the tensioning pedestal, and the filling material is a material whose structure is destroyed when electricity is applied;

[0007] Sleeves are provided at both ends of the steel casing, and slurry stoppers for blocking are provided in the openings of the sleeves.

[0008] Furthermore, the outer diameter of the steel casing is smaller than the borehole diameter, and the inner diameter is 20-25 mm larger than the outer diameter of the anchor rod body; the length of the steel casing is consistent with the set length of the prestressed section after tensioning.

[0009] Furthermore, the steel casing is constructed to be conductive so as to conduct current to the filling material, thereby destroying the structure of the filling material.

[0010] Furthermore, the diameter of the holes is 5-15 mm, and the distance between two adjacent holes is 20-30 cm.

[0011] Furthermore, the sleeve has a wall thickness of 6-10 mm, and comprises:

[0012] A threaded portion, used for connecting the steel casing, wherein the inner diameter of the threaded portion matches the outer diameter of the steel casing;

[0013] The filling stop plug portion is used to provide a receiving space for the stop plug.

[0014] Furthermore, the wall thickness of the steel casing is 4-6 mm, and both ends of the steel casing are respectively provided with threads, which are connected to the threaded part through the threads.

[0015] Furthermore, the stop plug is made of elastic material; the middle protrusion of the stop plug forms a spindle-shaped structure, the outer diameters of the front and rear ends of the stop plug are consistent with the inner diameter of the sleeve, and the outer diameter of the middle protrusion is 3-4 mm larger than the inner diameter of the sleeve.

[0016] Furthermore, the filling material is an inorganic material whose fluidity, compressive strength after consolidation, and gripping performance with the anchor rod body all meet preset conditions.

[0017] According to a second aspect of the present invention, a method for manufacturing the above-mentioned prefabricated tunnel prestressed anchor rod is provided, the manufacturing method comprising:

[0018] Install the steel casing on the tensioning pedestal according to the set position. The axis of the steel casing is consistent with the tensioning axis and kept horizontal. The length of the steel casing is consistent with the length of the prestressed section after tensioning. The holes on the steel casing are kept vertically upward. Sleeves are installed at both ends of the steel casing, and slurry stoppers are installed at both ends of the sleeve.

[0019] Pass the anchor rod body through the steel casing, place the prestressed section in the steel casing, start tensioning, and after tensioning to a set prestress, pour filling material into the space between the steel casing and the anchor rod body through the hole;

[0020] After the filling material solidifies and reaches the required design strength, the two ends of the anchor rod body are stretched. Before the prestressed anchor rod is put into storage for further curing, the grouting plugs and sleeves at both ends are removed to obtain a prefabricated tunnel prestressed anchor rod.

[0021] According to a third aspect of the present invention, a method for using the above-mentioned prefabricated tunnel prestressed anchor is provided, the method comprising:

[0022] Install prefabricated tunnel prestressed anchor rods in the drilled hole, bury and lead wires on the steel casing, pass the wires and grouting pipes through the grouting plugs, connect the grouting pipes to the reserved grouting holes, and grout the gaps between the anchor section, steel casing, and the drilled hole respectively;

[0023] After the slurry is filled and reaches the design strength, it is connected to the power supply through the wire, and the electric current is used to destroy the structure of the filling material, eliminating the gripping effect of the filling material on the prestressed anchor rod, and the prestress is transferred to the surrounding rock, thus completing the prestressed anchor rod support requirements.

[0024] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0025] The prefabricated tunnel prestressed anchor provided by the present invention is mass-produced in a factory using a special tensioning pedestal according to the anchor production process. Due to the assembly line prefabrication construction, the construction quality is easy to ensure and the stress retention effect is good. When used, the anchor is transported to the working surface and directly installed on site. After a period of time after the grouting of the anchoring section is completed, the filling material structure can be destroyed by electricity, and the prestress is transferred to the surrounding rock. The construction efficiency is high, and no special equipment and complicated operations are required. The operation is simple. The prestressed anchor above the arch line and axially toward the center of the tunnel can also be quickly constructed, and weak, broken, rock burst and other undesirable surrounding rocks can be reinforced in time. The prestressed state is maintained well, ensuring construction safety and structural safety, and solving the problems of conventional means with low operability, low efficiency, and high construction safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0027] Figure 1 This is a schematic structural diagram of a prefabricated tunnel prestressed anchor rod according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic structural diagram of a sleeve according to an embodiment of the present invention;

[0029] Figure 3 This is a schematic structural diagram of a slurry stopper according to an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of on-site installation of a prefabricated tunnel prestressed anchor rod according to an embodiment of the present invention;

[0031] In the figure: 1-unconstrained section, 2-prestressed section, 3-steel casing, 31-eyelet, 4-filling material, 5-sleeve, 51-threaded portion, 52-filled slurry plug portion, 6-slurry plug, 7-initial support surface, 8-conductor, 9-drilling channel, 10-slurry, 11-anchorage section, 12-base plate, 13-bolt. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0033] An embodiment of the present invention provides a prefabricated tunnel prestressed anchor rod, referring to Figure 1 The anchor rod includes an anchor rod body, which includes an unconstrained section 1 and a prestressed section 2 arranged in sequence; a steel casing 3 is provided on the outer shell of the anchor rod body of the prestressed section 2, and a hole 31 is opened on the steel casing 3. A filling material 4 is provided between the steel casing 3 and the anchor rod body. The filling material 4 is filled into the hole 31 after prestress is applied to the anchor rod body on the tensioning base. The filling material 4 is a material whose structure is destroyed after power is applied; sleeves 5 are provided at both ends of the steel casing 3, and a slurry stopper 6 for sealing is provided in the end opening of the sleeve 5.

[0034] In the above embodiment, the anchor rod body can be a conventional tunnel anchor rod. The rod body length, the length of the unconstrained section 1, and the length of the prestressed section 2 are set according to design requirements. The anchor rod body is prestressed on a tensioning pedestal in the factory. Material 4 is then filled between the steel sleeve 5 and the prestressed section 2 of the anchor rod body. After the filling material 4 reaches the set strength, tension is released to form a prefabricated prestressed anchor rod. This prefabricated prestressed anchor rod is transported to the tunnel working face and installed at the designed position. After grouting of the anchoring section, electricity is applied to destroy the filling material 4 structure, transferring the prestress to the surrounding rock.

[0035] In some embodiments, the outer diameter of the steel casing 3 is constrained by the diameter of the drill hole and must be ensured to be placed in the drill hole. Therefore, the outer diameter of the steel casing 3 is smaller than the diameter of the drill hole, and the inner diameter of the steel casing 3 is determined by comprehensive factors such as the anchor rod body diameter, the steel casing wall thickness, and the amount of filling material. Preferably, the inner diameter of the steel casing 3 is 20-25 mm larger than the outer diameter of the anchor rod body; the length of the steel casing 3 is consistent with the set length of the prestressed section 2 after tensioning.

[0036] In some embodiments, the steel casing 3 is constructed to be conductive. Specifically, since the steel casing 3 is made of steel and the main body is a non-insulating material, it can be conductive after being connected to a power source through the wire 8, thereby conducting current to the filling material 4, causing the structure of the filling material 4 to be destroyed.

[0037] Since the filling material 4 has good fluidity and the diameter of the steel casing 3 is generally between 55-60 mm, the diameter of the hole 31 should not be too large. In some embodiments, the diameter of the hole 31 is 5-15 mm. To improve the filling efficiency, the spacing between the holes 31 should be as small as possible. Considering the mutual influence between adjacent holes 31 when injecting the filling material 4, preferably, the spacing between two adjacent holes 31 is 20-30 cm.

[0038] In some embodiments, the two ends of the steel casing 3 are sealed with sleeves 5 and slurry stoppers 6. The wall thickness of the sleeve 5 is 6-10 mm. It can be understood by those skilled in the art that in order to effectively seal the filling material 4 in the steel casing 3, the larger the diameter of the sleeve 5, the correspondingly larger the wall thickness. Figure 2 The sleeve 5 includes a threaded portion 51 and a filling stop plug portion 52 in sequence, wherein: the threaded portion 51 is used to connect the steel casing 3, and the inner diameter of the threaded portion 51 matches the outer diameter of the steel casing 3; the filling stop plug portion 52 is used to provide an accommodating space for the stop plug 6.

[0039] The steel casing 3 mainly provides constraints for the filling material 4 to ensure prestress, so the steel casing 3 requires sufficient strength and rigidity, so its wall should not be too thin; but if the wall of the steel casing 3 is too thick, the filling amount of the filling material 4 will be too small and it will be difficult to achieve the designed prestress. Preferably, the wall thickness of the steel casing 3 is 4-6mm, and threads are provided at both ends of the steel casing 3. Specifically, the threads are 3cm threads provided at both ends of the steel casing 3, with a tooth angle of 75° and a pitch of 3.0, and are connected to the threaded part 51 through threads.

[0040] In order to make the stop plug 6 have a good sealing effect, the stop plug 6 is made of elastic material; Figure 3 Since the slurry stop plug 6 is made of elastic material, it needs to be inserted into the sleeve 5 to stop slurry before grouting. The slurry stop plug 6 needs to withstand the pressure from the filling material 4. In order to ensure that the slurry stop plug 6 is not pushed out, the middle protrusion of the slurry stop plug 6 forms a spindle-shaped structure. The outer diameters of the front and rear ends of the slurry stop plug 6 are consistent with the inner diameter of the sleeve 5, and the outer diameter of the middle protrusion is 3-4 mm larger than the inner diameter of the sleeve 5, thereby ensuring that the slurry stop plug 6 tightly plugs the end opening of the sleeve 5 to achieve a good sealing and slurry stopping effect.

[0041] In some embodiments, the sleeve 5 and the grout stopper 6 are installed before the anchor rod body is tensioned and removed after the prestressed anchor rod is prefabricated. The sleeve 5 and the grout stopper 6 can be reused.

[0042] In one embodiment, the sleeve 5 is 8 cm long and 6-10 mm thick. It is divided into two sections: one end is a 3 cm long threaded portion 51 for connecting to the steel casing 3, with an inner diameter matching the outer diameter of the steel casing 3; the other end is a 5 cm long filler stopper portion 52. The stopper 6 within the sleeve 5 is made of elastic material, is 6 cm long, and has a spindle-shaped structure. Each section is 2 cm long. The outer diameters of the front and rear ends match the inner diameter of the sleeve 5, while the outer diameter of the central protrusion (bulge) is 3-4 mm larger than the inner diameter of the sleeve 5. It is installed within the sleeve 5 before tensioning.

[0043] In the above embodiment, the filling material 4 is an inorganic material whose fluidity, compressive strength after solidification, and gripping performance with the anchor rod body all meet the preset conditions. The preset conditions are determined according to specific construction requirements. Since the material has good fluidity, high compressive strength after solidification, and good gripping performance with the anchor rod body, after the steel casing 3 becomes conductive, the material structure is destroyed under the action of the current, thereby effectively transferring the prestress to the surrounding rock.

[0044] The prefabricated tunnel prestressed anchor rod in the above embodiment can be transported to the working face and directly installed and used on site. After a period of time after the grouting of the anchoring section is completed, the filling material 4 structure can be destroyed by electricity, and the prestressed stress can be transferred and applied to the surrounding rock. The construction efficiency is high, and no special equipment and complicated operations are required. The operation is simple. The prestressed anchor rod above the arch line and axially toward the center of the tunnel can also be quickly constructed, and weak, broken, rock burst and other undesirable surrounding rocks can be reinforced in time. The prestressed state is maintained well, ensuring construction safety and structural safety, and solving the problems of low operability, low efficiency and high construction safety risks of conventional means.

[0045] Another embodiment of the present invention provides a method for manufacturing the aforementioned prefabricated tunnel prestressed anchor rod. The method comprises: first installing a steel casing 3 on a tensioning pedestal, with holes 31 provided on the steel casing 3. During installation, the holes 31 face upward, and the two ends of the steel casing 3 are connected to a sleeve 5 and a grout stopper 6, respectively. After tensioning to a set prestress, a filling material 4 is injected into the holes 31 on the steel casing 3. After solidification reaches the designed strength, the tension is released to obtain a prefabricated tunnel prestressed anchor rod. Specifically, the method comprises the following steps:

[0046] S1, install the steel casing 3 on the steel casing positioning frame on the tensioning platform according to the set position. The axis of the steel casing 3 is consistent with the tensioning axis and kept horizontal. The length of the steel casing 3 is consistent with the length of the prestressed section 2 after tensioning. The holes 31 on the steel casing 3 are kept vertically upward. Install sleeves 5 at both ends of the steel casing 3 and install slurry stoppers 6 at both ends of the sleeve 5;

[0047] S2, pass the anchor rod body through the steel casing 3, place the prestressed section 2 inside the steel casing 3, start tensioning, after tensioning to the set prestress, maintain for a period of time, fine-tune the position of the steel casing 3 to be consistent with the prestressed section 2, and then pour the filling material 4 into the space between the steel casing 3 and the anchor rod body through the hole 31, while pouring in skip holes and exhausting through the unfilled holes;

[0048] S3, after the pouring is completed, continue to maintain it for a period of time. After the filling material 4 reaches the design strength, the two ends of the anchor rod body are stretched; before the prestressed anchor rod is put into the warehouse for further curing, the grouting plugs 6 and sleeves 5 at both ends are removed to obtain a prefabricated tunnel prestressed anchor rod.

[0049] Another embodiment of the present invention further provides a method for using the above-mentioned prefabricated tunnel prestressed anchor rod, referring to Figure 4 , the usage method includes:

[0050] S1: Install a prefabricated tunnel prestressed anchor in the borehole 9, bury a conductor 8 in the steel casing 3 and lead it out, install a grouting plug 6, a pad 12, and a bolt 13 on the initial support surface 7, and install the pad 12 and bolt 13 at the end of the anchor rod body and close to the rock surface. The bolt 13 and pad 12 prevent the anchor rod body from retracting. The conductor 8 and the grouting pipe pass through the grouting plug 6 together, and the grouting pipe is connected to the reserved grouting hole. Grouting is performed between the anchor section 11 (corresponding to the unconstrained section 1 of the prefabricated tunnel prestressed anchor) and the borehole 9, and between the steel casing 3 and the borehole 9.

[0051] S2, after the slurry 10 is filled and reaches the design strength, a low-voltage current power source is connected through the conductor 8, and the current is used to destroy the structure of the filling material 4, eliminating the gripping effect of the filling material 4 on the prestressed anchor rod, and the prestress is transferred to the surrounding rock, completing the prestressed anchor rod support requirements.

[0052] The prefabricated tunnel prestressed anchor rods provided by the above-mentioned embodiment of the present invention are used by transporting the anchor rods to the working face and directly installing and using them on site. After a period of time after the grouting of the anchoring section is completed, electricity can be turned on to destroy the filling material structure and transfer the prestress to the surrounding rock. This can not only ensure the construction quality, but also maintain a good support stress, with high construction efficiency. No special equipment and complicated operations are required at the construction site. Even above the arch line, the prestressed anchor rods with the axis facing the center of the tunnel can be quickly constructed, and weak, broken, rock burst and other undesirable surrounding rocks can be reinforced in time, while ensuring construction safety and structural safety, and solving the problems of low operability, low efficiency and high construction safety risks of conventional means.

[0053] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various modifications or variations within the scope of the claims without affecting the essence of the present invention. The above preferred features may be used in any combination as long as they do not conflict with each other.

Claims

1. A prefabricated tunnel prestressed anchor, characterized in that: The anchor rod body comprises an unconstrained section and a prestressed section arranged in sequence; The anchor rod body of the prestressed section is covered with a steel casing, the steel casing is provided with holes, and a filling material is provided between the steel casing and the anchor rod body. The filling material is filled into the holes after prestress is applied to the anchor rod body on the tensioning pedestal, and the filling material is a material whose structure is destroyed when electricity is applied; Sleeves are provided at both ends of the steel casing, and slurry stoppers for blocking are provided in the openings of the sleeves; The steel casing provides constraints for the filling material to ensure prestress; the steel casing is constructed to be conductive so as to conduct current to the filling material to destroy the structure of the filling material.

2. The prefabricated tunnel prestressed anchor according to claim 1, characterized in that: The outer diameter of the steel casing is smaller than the borehole diameter, and the inner diameter is 20-25 mm larger than the outer diameter of the anchor rod body; the length of the steel casing is consistent with the set length of the prestressed section after tensioning.

3. The prefabricated tunnel prestressed anchor rod according to claim 1, characterized in that: The diameter of the holes is 5-15 mm, and the distance between two adjacent holes is 20-30 cm.

4. The prefabricated tunnel prestressed anchor rod according to claim 1, characterized in that: The wall thickness of the sleeve is 6-10 mm, and the sleeve comprises: A threaded portion, used for connecting the steel casing, wherein the inner diameter of the threaded portion matches the outer diameter of the steel casing; The filling stop plug portion is used to provide a receiving space for the stop plug.

5. The prefabricated tunnel prestressed anchor rod according to claim 4, characterized in that: The wall thickness of the steel casing is 4-6 mm, and both ends of the steel casing are respectively provided with threads, which are connected to the threaded part through the threads.

6. The prefabricated tunnel prestressed anchor rod according to claim 1, characterized in that: The stop plug is made of elastic material; the middle protrusion of the stop plug forms a spindle-shaped structure, the outer diameters of the front and rear ends of the stop plug are consistent with the inner diameter of the sleeve, and the outer diameter of the middle protrusion is 3-4 mm larger than the inner diameter of the sleeve.

7. The prefabricated tunnel prestressed anchor according to claim 1, characterized in that: The filling material is an inorganic material whose fluidity, compressive strength after consolidation, and gripping performance with the anchor rod body all meet preset conditions.

8. A method for manufacturing a prefabricated tunnel prestressed anchor rod according to any one of claims 1 to 7, characterized in that: include: Install the steel casing on the tensioning pedestal according to the set position. The axis of the steel casing is consistent with the tensioning axis and kept horizontal. The length of the steel casing is consistent with the length of the prestressed section after tensioning. The holes on the steel casing are kept vertically upward. Sleeves are installed at both ends of the steel casing, and slurry stoppers are installed at both ends of the sleeve. Pass the anchor rod body through the steel casing, place the prestressed section in the steel casing, start tensioning, and after tensioning to a set prestress, pour filling material into the space between the steel casing and the anchor rod body through the hole; After the filling material solidifies and reaches the required design strength, the two ends of the anchor rod body are stretched. Before the prestressed anchor rod is put into storage for further curing, the grouting plugs and sleeves at both ends are removed to obtain a prefabricated tunnel prestressed anchor rod.

9. A method for using the prefabricated tunnel prestressed anchor rod according to any one of claims 1 to 7, characterized in that: include: Install prefabricated tunnel prestressed anchor rods in the drilled hole, bury and lead wires on the steel casing, pass the wires and grouting pipes through the grouting plugs, connect the grouting pipes to the reserved grouting holes, and grout the gaps between the anchor section, steel casing, and the drilled hole respectively; After the slurry is filled and reaches the design strength, it is connected to the power supply through the wire, and the electric current is used to destroy the structure of the filling material, eliminating the gripping effect of the filling material on the prestressed anchor rod, and the prestress is transferred to the surrounding rock, thus completing the prestressed anchor rod support requirements.

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