Base plate assembly, tunnel anchor rod supporting structure and anchor rod prestress applying method

Abstract

The invention provides a base plate assembly, a tunnel anchor rod supporting structure and an anchor rod prestress applying method, and relates to the technical field of tunnel engineering construction.The base plate assembly comprises a rear base plate layer, a middle base plate layer and a front base plate layer; the rear base plate layer comprises a solid metal body; each of the middle backing plate layer and the front backing plate layer comprises a metal shell and a self-expanding cement medicine bag arranged in the metal shell; the medicine bag comprises an inner packaging bag and an outer packaging bag, the inner packaging bag is filled with quick-setting cement, and the space between the outer packaging bag and the inner packaging bag is filled with a self-expanding agent. Wherein the inner-layer packaging bag and the outer-layer packaging bag of the front base plate layer are both made of a permeable material; the inner-layer packaging bag of the middle base plate layer is made of a water-permeable material, and the outer-layer packaging bag is made of a water-impermeable material; the middle base plate layer further comprises a water inlet pipe and a water outlet pipe which make contact with the self-expanding agent. The technical problems that according to an existing anchor rod prestress applying method, the applying process is tedious, prestress loss is serious, and prestress cannot be supplemented in the service period are solved.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering construction technology, and in particular to a pad assembly, a tunnel anchor support structure, and a method for applying anchor prestress. Background Technology

[0002] Rock bolt support technology, as an important reinforcement method in geotechnical engineering, is widely used in underground engineering projects such as tunnels and slopes. Prestressed rock bolts improve the stress state of the surrounding rock by actively applying prestress, and the core technology lies in the effective application and long-term maintenance of prestress.

[0003] Existing methods for applying prestress to anchor bolts employ the principle of mechanical tensioning. Tensioning equipment such as jacks is used to apply tension to the anchor bolt body. Once the design load is reached, anchorages are used for mechanical locking. The core steps include: drilling and installation: Anchor bolt holes are drilled in the rock mass, and prestressed anchor bolts with free and anchored sections are inserted; tensioning: The free section of the anchor bolt is tensioned using hydraulic jacks or other tensioning equipment to reach the design prestress value; locking and anchoring: After tensioning, the anchor bolt is immediately locked to a pad or tray using anchorages (such as wedge-type anchorages, nuts, etc.), thus "locking" the prestress into the anchor bolt system; unloading equipment: The tensioning equipment is unloaded, completing the prestressing application process.

[0004] Existing methods for applying prestress to anchor bolts have at least the following drawbacks: ①The application process is cumbersome: The application of prestress in existing anchor bolts requires tensioning using equipment followed by locking, a rather cumbersome process. Specifically, in the standard construction procedure, workers must first install the anchor bolts and complete grouting consolidation. After the grout reaches sufficient strength, the tensioning equipment is installed, and the design prestress value is applied in stages using a hydraulic pump. The nuts are then immediately tightened to complete the anchoring and locking. This process involves multiple steps, including relocating the tensioning equipment, connecting hydraulic lines, and maintaining the load. On-site operation is time-consuming and subject to equipment scheduling constraints. ②Severe loss of prestress: The tension force on the existing anchor bolt after tensioning is the prestress applied to the anchor bolt. During the locking and anchoring process after tensioning, instantaneous displacement can easily occur between anchor components (such as wedge anchors, washers, and threaded pairs), causing the anchor bolt to spring back. This results in a significant loss of the anchor bolt prestress, with the actual effective prestress applied to the surrounding rock being far lower than the design value, weakening the support effect. The loss can reach 30%-50% of the design value. This stress loss directly reduces the anchor bolt's restraint effect on the surrounding rock and needs to be compensated by over-tensioning. However, over-tensioning may bring safety risks or material fatigue problems. ③ Prestress cannot be replenished during service life: Tunnel engineering is typically constructed in stages: initial support (including anchor bolts) - waterproofing layer - secondary lining (reinforced concrete structure). After the secondary lining is completed, the ends of the anchor bolts are completely encased in concrete, making them invisible and inaccessible from the outside. For anchor bolt structures that have been in service for a long time, factors such as surrounding rock rheology, temperature changes, and corrosion can cause continuous attenuation of the anchor bolt prestress. Once existing anchor bolts are sealed by the secondary lining, they lose an effective stress compensation channel and cannot be tensioned to supplement prestress. This irreversible prestress attenuation will gradually weaken the bearing capacity of the support system, potentially leading to engineering hazards such as lining cracking in weak surrounding rock sections. If maintenance is required, the lining often needs to be removed, which is costly and affects operational safety. Summary of the Invention

[0005] The purpose of this invention is to provide a pad assembly, a tunnel anchor support structure, and a method for applying anchor prestress, so as to alleviate the technical problems of existing anchor prestress application methods, such as cumbersome application process, serious prestress loss, and inability to replenish prestress during service.

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: In a first aspect, embodiments of the present invention provide a pad assembly for use in tunnel anchor bolt support structures, wherein the side facing the surrounding rock in its installed state is the front side, and the side away from the surrounding rock is the rear side. The pad assembly comprises layers stacked from back to front: The rear pad layer includes a solid metal body and a shaft hole that penetrates the central region of the solid metal body in the front-rear direction; The middle pad layer and the front pad layer each include a metal outer shell and a self-expanding cement medicine bag; the metal outer shell is cylindrical with an axially penetrating inner cavity inside, the self-expanding cement medicine bag is rolled up in the inner cavity, and the middle region of the self-expanding cement medicine bag forms a second axial hole extending along the axial direction of the metal outer shell, the second axial hole being coaxial with the first axial hole; the self-expanding cement medicine bag includes an inner packaging bag and an outer packaging bag, the inner packaging bag is filled with quick-setting cement, and the space between the outer packaging bag and the inner packaging bag is filled with a self-expanding agent that can self-expand after immersion in water; Wherein: the inner and outer packaging bags of the front pad layer are both made of water-permeable material; the inner packaging bag of the middle pad layer is made of water-permeable material and the outer packaging bag is made of impermeable material; the middle pad layer also includes an inlet pipe and an outlet pipe, which pass through the metal shell and the outer packaging bag of the middle pad layer respectively and come into contact with the self-expanding agent.

[0007] In an optional embodiment, the pad assembly further includes a pressure-sensitive element that is pressed into the gap between the front surface of the solid metal body of the rear pad layer and the rear surface of the middle pad layer. A data line is connected to the pressure-sensitive element, and the data output end of the data line extends to the outside of the gap.

[0008] In an optional embodiment, the metal shell of the middle pad layer is provided with a plurality of self-expanding cement bags, each of the self-expanding cement bags being connected to at least one inlet pipe and at least one outlet pipe.

[0009] In an optional embodiment, a filter screen is installed at the opening of the water inlet pipe and the water outlet pipe where they connect to the outer packaging bag.

[0010] In an optional embodiment, both the solid metal body and the metal outer shell are made of steel.

[0011] In an optional embodiment, the volume of the self-expanding agent before immersion in water is V1, and the maximum volume that can expand after immersion in water is V2. Then: 2V1≤V2≤3V1; the compressive strength of the quick-setting cement after immersion in water for 1 hour is greater than or equal to 20MPa.

[0012] Secondly, embodiments of the present invention provide a tunnel anchor bolt support structure, including an anchor bolt, a nut, and a pad assembly provided in any of the optional embodiments of the first aspect. In the installed state, the front end of the anchor bolt is anchored inside the surrounding rock of the tunnel, and the pad assembly and the nut are both sleeved on the outside of the tail end of the anchor bolt. The nut is threadedly connected to the anchor bolt to press the pad assembly between the outer wall of the surrounding rock and the nut. The water inlet pipe and the water outlet pipe both extend to the outside of the secondary lining structure of the tunnel through pre-embedded pipes.

[0013] Thirdly, embodiments of the present invention provide a method for applying prestress to an anchor bolt, wherein the method applies the pad assembly provided in any of the optional embodiments of the first aspect, and specifically includes the following steps: Anchor the front end of the anchor bolt to the inside of the tunnel surrounding rock; Immerse the pad assembly in water, ensuring that the external interfaces of its data cable, inlet pipe, and outlet pipe are not submerged. After the self-expanding cement bag of the front pad layer no longer produces air bubbles, fit the pad assembly along the axial holes of each pad layer onto the outside of the anchor rod's tail end. Thread the nut onto the tail end of the anchor rod to press the pad assembly between the outer wall of the surrounding rock and the nut.

[0014] In an optional embodiment, the pad assembly further includes a pressure-sensitive element that is pressed into the gap between the front surface of the solid metal body of the rear pad layer and the rear surface of the middle pad layer. A data line is connected to the pressure-sensitive element, and the data output end of the data line extends to the outside of the gap. The anchor bolt prestressing application method further includes: connecting the data output end of the data cable to a display device, monitoring the pressure data value through the display device, and adding water to the water inlet pipe to supplement the prestress of the anchor bolt when the pressure data value is detected to decline to a preset value.

[0015] In an optional implementation, the step of anchoring the front end of the anchor bolt into the surrounding rock of the tunnel includes: Drill anchor bolt holes inside the tunnel surrounding rock, insert the front end of the anchor bolt into the drilled anchor bolt hole, and press resin anchoring agent into the anchor bolt hole.

[0016] The embodiments of the present invention can achieve at least the following beneficial effects: ① The anchor rod is tensioned and the initial prestress is applied by the self-expansion effect of the front self-expanding cement bag after reacting with water. The application process does not involve the use of external equipment to tension the anchor rod, and there is no step of using locking anchors. This eliminates the two processes of mechanical tensioning and anchoring locking of the anchor rod in the traditional prestress application process, reduces construction steps, and improves construction efficiency. ② The application process does not involve the use of external equipment to tension the anchor rods, and there is no step of using locking anchors, which effectively avoids the problem of sudden drop in prestress that occurs when locking traditional anchors, and the prestress value applied to the anchor rods is relatively stable; ③ During the service period of the anchor bolt, water is added to the self-expanding cement bag in the middle through the reserved water inlet pipe. After adding water, expansion pressure is generated again, which can replenish the anchor bolt prestress lost during the service period.

[0017] In summary, the pad assembly, tunnel anchor support structure, and anchor prestressing application method provided in this embodiment of the invention are convenient to operate during construction, can effectively avoid prestress loss caused by tensioning the locking device, and can effectively supplement the prestress lost by the anchor during its service life. It solves the problems of cumbersome anchor prestressing application process, prestress loss during anchor prestressing tensioning and locking process, and the inability to supplement prestress loss during subsequent long-term service, and has good promotion and application value. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the pad assembly applied to the tunnel anchor support structure provided in an embodiment of the present invention; Figure 2 In the pad assembly provided in the embodiment of the present invention, the radial cross-sectional view of the rear pad layer is shown with the front-to-back direction as the axial direction. Figure 3 A radial cross-sectional view of the middle pad layer in the pad assembly provided in the embodiment of the present invention, with the front-to-back direction as the axial direction; Figure 4 In the pad assembly provided in the embodiment of the present invention, a radial cross-sectional view of the front pad layer is shown with the front-to-back direction as the axial direction. Figure 5 A schematic diagram of the installation method of the tunnel anchor support structure in the surrounding rock of the tunnel in the anchor prestressing application method provided in the embodiments of the present invention; Figure 6 In the anchor bolt prestressing application method provided in the embodiments of the present invention, a schematic diagram of the anchor bolt prestressing generation principle is shown, with the arrow indicating the direction of the pressure applied by the pad assembly to the tunnel surrounding rock through self-expansion; Figure 7 In the anchor bolt prestressing application method provided in the embodiment of the present invention, a schematic diagram of the anchor bolt prestressing supplementation principle is shown, with the arrow indicating the direction of the pressure applied by the self-expansion of the pad assembly to the surrounding rock of the tunnel.

[0020] Icons: 100 - Pad assembly; 110 - Shaft hole; 111 - Shaft hole one; 112 - Shaft hole two; 200 - Surrounding rock; 210 - Anchor bolt insertion hole; 300 - Resin anchoring agent; 1-Rear pad layer; 11-Solid metal body; 2-Middle pad layer; 21-Middle pad metal casing; 22-Inlet pipe; 23-Outlet pipe; 3-Front pad layer; 31-Front pad metal casing; 4-Self-expanding cement medicine bag; 401-Middle self-expanding cement medicine bag; 402-Front self-expanding cement medicine bag; 41-Inner packaging bag; 411-Quick-setting cement; 42-Outer packaging bag; 421-Self-expanding agent; 5 - Pressure-sensitive components; 51 - Data cables; 6-Anchor bolt; 7-Nut. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar labels and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings.

[0024] In the description of this invention, it should be noted that: Unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] The terms “front,” “rear,” “center,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0026] The terms “first,” “second,” “third,” etc., are used only for distinguishing descriptions and do not indicate totality or relative position in time and / or space, nor should they be construed as indicating or implying relative importance.

[0027] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the features of the following embodiments and optional embodiments can be combined with each other.

[0028] First aspect This embodiment provides a pad assembly applied to a tunnel anchor bolt support structure, referring to... Figure 1 , Figure 5 , Figure 6 and Figure 7 With the side facing the surrounding rock 200 in its installed state as its front side and the side away from the surrounding rock 200 as its rear side, the pad assembly 100 includes a rear pad layer 1, a middle pad layer 2 and a front pad layer 3 stacked from back to front.

[0029] Specifically: refer to Figure 2 The rear pad layer 1 includes a solid metal body 11 and a shaft hole 111 that penetrates the central region of the solid metal body 11 in the front-rear direction.

[0030] Reference Figure 3 The middle pad layer 2 includes a middle pad metal shell 21, a self-expanding cement medicine bag 4, an inlet pipe 22, and an outlet pipe 23. The middle pad metal shell 21 is cylindrical and has an axially penetrating inner cavity. The self-expanding cement medicine bag 4 is rolled up in the inner cavity of the middle pad metal shell 21, and the middle region of the self-expanding cement medicine bag 4 forms a second shaft hole 112 extending axially along the middle pad metal shell 21. The second shaft hole 112 is coaxial with the first shaft hole 111 provided on the aforementioned rear pad layer 1. The self-expanding cement medicine bag 4 is located inside the central pad metal shell 21, and includes an inner packaging bag 41 made of water-permeable material and an outer packaging bag 42 made of impermeable material. The inner packaging bag 41 is filled with quick-setting cement 411, and the space between the outer packaging bag 42 and the inner packaging bag 41 is filled with a self-expanding agent 421 that can self-expand after being immersed in water. The water inlet pipe 22 and the water outlet pipe 23 pass through the central pad metal shell 21 and the outer packaging bag 42 of the central pad layer 2, respectively, and come into contact with the self-expanding agent 421 of the central pad layer 2.

[0031] Reference Figure 4 The front pad layer 3 includes a front pad metal shell 31 and a self-expanding cement medicine bag 4 disposed inside the front pad metal shell 31. The front pad metal shell 31 is cylindrical and has an axially penetrating inner cavity. The self-expanding cement medicine bag 4 is rolled up in the inner cavity of the front pad metal shell 31, and a second axial hole 112 extending axially along the front pad metal shell 31 is formed in the middle region of the self-expanding cement medicine bag 4. This second axial hole 112 is coaxial with the first axial hole 111 provided on the aforementioned rear pad layer 1. The self-expanding cement medicine bag 4 disposed inside the front pad metal shell 31 includes an inner packaging bag 41 and an outer packaging bag 42. Both the inner packaging bag 41 and the outer packaging bag 42 are made of water-permeable material. The inner packaging bag 41 is filled with quick-setting cement 411, and a self-expanding agent 421 that can self-expand after immersion in water is filled between the outer packaging bag 42 and the inner packaging bag 41.

[0032] In anchor bolt support engineering, the anchor bolt prestressing method using the pad assembly provided in this embodiment to apply prestress to the anchor bolt includes at least the following steps: Anchor the front end of anchor bolt 6 to the inside of the surrounding rock 200 of the tunnel; Immerse the pad assembly 100 in water, ensuring that the external interfaces of its inlet pipe 22 and outlet pipe 23 are not submerged. At this time: due to the self-expanding cement medicine bag 4 (i.e., Figure 6 The outer packaging bag of the self-expanding cement medicine bag 401 in the middle shown is made of waterproof material, so water cannot enter the interior of the self-expanding cement medicine bag 401 in the middle; at the same time, because the self-expanding cement medicine bag 4 (i.e., the self-expanding cement medicine bag 4 inside the front pad metal shell 31) Figure 6 The inner and outer double-layer packaging bags of the front self-expanding cement medicine bag 402 shown are both made of water-permeable material. Water can enter the interior of the front self-expanding cement medicine bag 402 through the opening of the front pad metal shell 31 and come into contact with the self-expanding agent 421 and the quick-setting cement 411. Once the self-expanding cement medicine bag at the front no longer produces air bubbles, such as Figure 6 As shown, the pad assembly 100 is fitted onto the outside of the tail end of the anchor rod 6 along the shaft holes 110 of each pad layer (shaft hole 111 of the rear pad layer 1, shaft holes 112 of the middle pad layer 2 and the front pad layer 3 respectively). The nut 7 is threaded onto the tail end of the anchor rod 6 to press the pad assembly 100 between the outer wall of the surrounding rock 200 and the nut 7. Figures 5 to 7 As shown, the surrounding rock 200, the front pad layer 3, the middle pad layer 2, the rear pad layer 1, and the nut 7 are arranged closely from front to back. The front self-expanding cement medicine bag 402 is fitted outside the anchor rod 6 and is enclosed in the space formed by the surrounding rock 200, the front pad metal shell 31, and the middle self-expanding cement medicine bag 401.

[0033] After a period of time, the quick-setting cement 411 in the front self-expanding cement bag will rapidly solidify after absorbing water. At this time, the self-expanding agent 421 in the front self-expanding cement bag 402 will gradually expand in volume after reacting with water. The self-expanding agent 421 will generate a large expansion pressure on the surrounding rock. According to the law of interaction of forces, the initial expansion pressure caused by the self-expanding agent 421 on the surrounding rock 200 will achieve a certain degree of tension on the anchor rod 6, that is, apply prestress to the anchor rod 6. The expansion effect of the self-expanding agent 421 basically ends after about 18 hours. Therefore, the prestressing of the anchor rod 6 ends 18 hours after installation, and the prestress of the anchor rod tends to stabilize thereafter. After a period of time, the initial prestress decreases. At this point, it can be... Figure 7As shown, water is supplied to the inner packaging bag 42 of the self-expanding cement bag 401 through the water inlet pipe 22. The supplied water reacts with the self-expanding agent 421 inside to cause self-expansion. At the same time, the water seeps into the inner packaging bag 41 of the self-expanding cement bag 401 and reacts with the quick-setting cement 411. The quick-setting cement 411 solidifies rapidly, and the self-expanding agent 421 gradually expands to supplement the prestress and avoid unsafe problems caused by the prestress decay.

[0034] The key points of the above construction steps in this embodiment include: (1) Anchor the front end of the anchor rod 6 into the surrounding rock 200 to provide a far-end fixed support point for the anchor rod 6, so that the expansion force generated by the subsequent pad assembly 100 can be converted into an axial tensile force on the anchor rod 6. (2) Only the front self-expanding cement medicine bag 402 is allowed to seep into water, while the middle self-expanding cement medicine bag 401 remains dry inside because the outer packaging bag 42 is waterproof. This achieves selective activation of the front self-expanding cement medicine bag 402 and enables the pad assembly 100 to pre-expand before installation. (3) such as Figure 6 As shown, after the front self-expanding cement bag 402 stops producing gas, the partially expanded pad assembly 100 is fitted over the outside of the anchor rod 6 and pressed between the surrounding rock 200 and the nut 7. The surrounding rock 200, the front pad layer 3, the middle pad layer 2, the rear pad layer 1, and the nut 7 are arranged tightly from front to back to form a closed force transmission system. The installation after the front self-expanding cement bag 402 stops producing gas ensures that the expansion reaction inside the front self-expanding cement bag 402 enters a stable expansion stage, thus avoiding the bag from breaking or deforming out of control during the installation process. (4) such as Figure 6 As shown, the self-expanding agent 421 inside the front self-expanding cement bag 402 continuously absorbs water and expands, pushing the surrounding rock 200 forward and the middle pad layer 2, the rear pad layer 1 and the nut 7 backward. At this time, since the front end of the anchor rod 6 has been anchored inside the surrounding rock 200, the rod body of the anchor rod 6 will be axially stretched and prestressed. After 18 hours, the prestress tends to stabilize. (5) After a period of time, the applied initial prestress decreases. At this time, such as Figure 7 As shown, water is supplied to the interior of the self-expanding cement bag 401 in the middle through the water inlet pipe 22. The quick-setting cement 411 inside the self-expanding cement bag 401 solidifies. The self-expanding agent 421 inside the self-expanding cement bag 401 continuously absorbs water and expands to generate secondary expansion pressure. This secondary expansion pressure will provide a certain supplement to the prestress.

[0035] In this embodiment, it is important to note that: Regarding quick-setting cement 411 and self-expanding agent 421: Quick-setting cement 411 is a special cement that can quickly harden and reach high strength in a short time. Its main components include silicate cement clinker, aluminate accelerators, water-reducing agents, mineral admixtures, etc., and it is usually used in projects that require rapid repair or reinforcement. Self-expanding agent 421 is an admixture that enables cement-based materials to expand in volume during the hardening process. Its main components include anhydrous calcium sulfoaluminate, calcium oxide, alum stone, gypsum, retarders / accelerators, etc., and it is mainly used to compensate for shrinkage, prevent cracking, and improve density. Both materials are existing technologies, and their specific component designs will not be elaborated here. In some optional implementations, the volume of the selected self-expanding agent 421 before immersion in water is V1, and the maximum volume that can expand after immersion in water is V2. Then: 2V1≤V2≤3V1; the compressive strength of the selected quick-setting cement 411 after immersion in water for 1 hour is greater than or equal to 20MPa. For packaging bags made of permeable materials, materials such as non-woven fabric, glass fiber filter cloth, nylon / polyester monofilament filter cloth, cotton gauze, or linen can be selected. Their characteristic is that only water molecules are allowed to pass through, while the self-expanding agent 421 and its flocculent or particulate reactants with water are not allowed to pass through. The prestress value applied to the anchor bolt 6 is related to the amount of self-expanding agent 421 added. During application, the amount of self-expanding agent 421 added can be adjusted to flexibly change the magnitude of the prestress value applied to the anchor bolt 6 to adapt to different engineering standards.

[0036] The pad assembly and the anchor prestressing application method using it provided in this embodiment can achieve at least the following beneficial effects: ①The anchor rod 6 is tensioned and the initial prestress is applied by the self-expansion effect of the front self-expanding cement bag 402 after reacting with water. The application process does not involve the use of external equipment to tension the anchor rod 6, and there is no step of using locking anchors. This eliminates the two processes of mechanical tensioning and anchoring locking of the anchor rod 6 in the traditional prestress application process, reduces construction steps, and improves construction efficiency. ② The application process does not involve the use of external equipment to tension the anchor rod 6, and there is no step of using locking anchors, which effectively avoids the problem of sudden drop in prestress that occurs when locking traditional anchors, and the prestress value applied to the anchor rod 6 is relatively stable; ③ During the service period of the anchor bolt, water is added to the self-expanding cement bag 401 in the middle through the reserved water inlet pipe 22. After adding water, expansion pressure is generated again, which can replenish the anchor bolt prestress lost during the service period.

[0037] In summary, the pad assembly and the anchor bolt prestressing application method provided in this embodiment are convenient to operate during construction, can effectively avoid prestress loss caused by tensioning the locking device, and can effectively supplement the prestress lost by the anchor bolt 6 during its service life. It solves the problems of cumbersome anchor bolt prestressing application process, prestress loss during anchor bolt prestressing tensioning and locking process, and the inability to supplement prestress loss during subsequent long-term service, and has good promotion and application value.

[0038] Continue to refer to Figure 1 , Figure 5 , Figure 6 and Figure 7 In an optional embodiment of this example, the aforementioned pad assembly 100 further includes a pressure-sensitive element 5. This pressure-sensitive element 5 is pressed into the gap between the front surface of the solid metal body 11 of the rear pad layer 1 and the rear surface of the middle pad layer 2. A data line 51 is connected to the pressure-sensitive element 5, and the data output end of the data line 51 extends outside the gap between the front surface of the solid metal body 11 and the rear surface of the middle pad layer 2. This data line 51 is used to connect to a display device to monitor pressure data values. When the pressure data value is detected to have decreased to a preset value, water is added to the water inlet pipe 22 to replenish the prestress to the anchor rod 6. This embodiment uses real-time monitoring to remind workers to replenish prestress in a timely manner. Compared to periodic prestress replenishment, this dynamic replenishment method can replenish lost prestress more promptly and effectively, preventing structural damage or failure due to prestress loss and improving the safety and stability of the structure.

[0039] Reference Figure 1 and Figure 3 In an optional embodiment of this example, the water inlet pipe 22 and the water outlet pipe 23 are respectively located on opposite sides of the corresponding outer packaging bag 42. By setting the water inlet pipe and the water outlet pipe on opposite sides, an effective water flow channel can be formed, allowing water to enter the medicine bag quickly and evenly, and excess water to be discharged quickly when needed. This not only improves the efficiency of the water addition reaction, but also shortens the expansion reaction time, while reducing stress concentration and potential structural damage risks caused by uneven local expansion.

[0040] Reference Figure 1In an optional embodiment of this invention, the metal shell of the central pad layer 2 is provided with multiple self-expanding cement bags 4, each of which is connected to at least one inlet pipe 22 and at least one outlet pipe 23. In this embodiment, water can be injected into the central self-expanding cement bags 401 in stages as needed during the service of the structure, triggering their successive expansion reactions. This constructs a prestress maintenance mechanism that can be repeatedly activated, has a controllable temporal response, and is spatially adjustable, thereby realizing the periodic reconstruction and compensation of prestress and significantly improving the long-term load-bearing stability and durability of the structure.

[0041] In an optional embodiment of this example, filters are installed at the inlet pipe 22 and outlet pipe 23 where they are connected to the outer packaging bag 42, respectively, to allow water molecules to pass through while preventing the self-expanding agent 421 and the flocculent or particulate reaction product of the self-expanding agent 421 and water from passing through. This prevents the self-expanding agent 421 and the flocculent or particulate reaction product of the self-expanding agent 421 and water from being lost along the water pipes, and ensures that the self-expanding agent 421 inside the outer packaging bag 42 effectively applies expansion pressure in the forward and backward directions.

[0042] In an optional embodiment of this example, the solid metal body 11 of the rear pad layer 1, the metal outer shell 21 of the middle pad, and the metal outer shell 31 of the front pad are all made of steel.

[0043] Second aspect This embodiment provides a tunnel anchor bolt support structure, referring to... Figures 5 to 7 The tunnel anchor support structure includes an anchor 6, a nut 7, and a pad assembly 100 provided by any optional embodiment of the first aspect. The specific structure and achievable effect of the pad assembly 100 in this embodiment can be obtained by referring to the optional or preferred embodiments of the first aspect.

[0044] In the installed state, the front end of the anchor rod 6 is anchored inside the surrounding rock 200 of the tunnel. The pad assembly 100 and the nut 7 are both sleeved on the outside of the tail end of the anchor rod 6. The nut 7 is threaded to the anchor rod 6 to press the pad assembly 100 between the outer wall of the surrounding rock 200 and the nut 7. The data cable 51, the water inlet pipe 22 and the water outlet pipe 23 are all extended to the outside of the secondary lining structure of the tunnel through pre-embedded pipes.

[0045] Third aspect This embodiment provides a method for applying prestress to an anchor bolt. This method utilizes the pad assembly provided in any optional embodiment of the first aspect, referring to… Figures 1 to 7 The method for applying prestress to the anchor bolt includes at least the following steps: Anchor the front end of anchor bolt 6 to the inside of the surrounding rock 200 of the tunnel; Immerse the pad assembly 100 in water, ensuring that the external interfaces of its data cable 51, water inlet pipe 22, and water outlet pipe 23 are not submerged. After the self-expanding cement bag 4 of the front pad layer 3 no longer produces air bubbles, fit the pad assembly 100 along the shaft hole 110 of each pad layer onto the outside of the tail end of the anchor rod 6. Thread the nut 7 onto the tail end of the anchor rod 6 to press the pad assembly 100 between the outer wall of the surrounding rock 200 and the nut 7.

[0046] For more specific construction methods and prestressing application principles, please refer to the relevant description in the first part.

[0047] Continue to refer to Figures 1 to 7 In an optional embodiment of this example, the data output terminal of the data cable 51 is connected to the display device, and the pressure data value is monitored through the display device. When the pressure data value is detected to decline to a preset value, water is added to the water inlet pipe 22 to supplement the prestress to the anchor rod 6.

[0048] Reference Figure 5 In an optional embodiment of this example, the step of anchoring the front end of the anchor rod 6 into the tunnel surrounding rock 200 includes: drilling an anchor rod insertion hole 210 into the tunnel surrounding rock 200, inserting the front end of the anchor rod 6 into the drilled anchor rod insertion hole 210, and pressing resin anchoring agent 300 into the anchor rod insertion hole 210.

[0049] Finally, it should be noted that: The embodiments and optional implementations described above in this specification are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing optional implementations, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Furthermore, it is emphasized again that, in the absence of conflict, the features of the embodiments and optional implementations in the embodiments in this specification can be combined with each other.

Claims

1. A mat plate assembly for use in a tunnel anchor support structure, the mat plate assembly having a front side and a back side, the front side facing towards the surrounding rock (200) in the installed state of the mat plate assembly, the back side facing away from the surrounding rock (200), characterized in that The mat assembly (100) comprises, from back to front, a rear mat layer (1), a middle mat layer (2), and a front mat layer (3). The rear mat layer (1) comprises a solid metal body (11) and an axial hole (111) penetrating a middle region of the solid metal body (11) in a front-rear direction; The middle mat layer (2) and the front mat layer (3) each comprise a metal shell and a self-expanding cement cartridge (4); the metal shell is in a cylindrical shape and has an internal cavity extending in an axial direction, and the self-expanding cement cartridge (4) is wound in the internal cavity; a middle region of the self-expanding cement cartridge (4) forms an axial hole (112) extending in the axial direction of the metal shell, and the axial hole (112) is coaxial with the axial hole (111); the self-expanding cement cartridge (4) comprises an inner layer packaging bag (41) and an outer layer packaging bag (42); the inner layer packaging bag (41) is filled with quick-setting cement (411), and the outer layer packaging bag (42) is filled with a self-expanding agent (421) that can self-expand after being immersed in water. The inner layer packaging bag (41) and the outer layer packaging bag (42) of the front mat layer (3) are each made of a water-permeable material; the inner layer packaging bag (41) of the middle mat layer (2) is made of a water-permeable material, and the outer layer packaging bag (42) is made of a water-impermeable material; the middle mat layer (2) further comprises a water inlet pipe (22) and a water outlet pipe (23), and the water inlet pipe (22) and the water outlet pipe (23) respectively pass through the metal shell and the outer layer packaging bag (42) of the middle mat layer (2) to contact the self-expanding agent (421).

2. A pad assembly for use in a tunnel roof bolting configuration as claimed in claim 1 wherein, The mat assembly (100) further comprises a pressure-sensitive component (5) that is squeezed in a gap between a front side surface of the solid metal body (11) of the rear mat layer (1) and a rear side surface of the middle mat layer (2); a data line (51) is connected to the pressure-sensitive component (5), and a data output end of the data line (51) extends to outside the gap.

3. A pad assembly for use in a tunnel roof bolting configuration as claimed in claim 1 wherein, The metal shell of the middle mat layer (2) has a plurality of self-expanding cement cartridges (4) therein, and each self-expanding cement cartridge (4) is connected to at least one water inlet pipe (22) and at least one water outlet pipe (23).

4. A pad assembly for use in a tunnel roof bolting configuration as claimed in claim 1 wherein, A filter screen is installed at each pipe opening of the water inlet pipe (22) and the water outlet pipe (23) that connects to the outer layer packaging bag (42).

5. A pad assembly for use in a tunnel roof bolting configuration as claimed in claim 1 wherein, The solid metal body (11) and the metal shell are each made of steel.

6. A pad assembly for use in a tunnel roof bolting configuration as claimed in claim 1 wherein, The self-expanding agent (421) has a volume V1 before being immersed in water and a maximum volume V2 after being immersed in water, and 2V1≤V2≤3V1; the quick-setting cement (411) has a compressive strength greater than or equal to 20 MPa after being immersed in water for 1 hour.

7. A tunnel anchor support structure, characterised in that, The anchor rod (6), the nut (7) and the backing plate assembly (100) of any one of claims 1-6 are installed in a state that the front end of the anchor rod (6) is anchored inside the tunnel surrounding rock (200), the backing plate assembly (100) and the nut (7) are both sleeved outside the tail end of the anchor rod (6), the nut (7) is threadedly connected to the tail end of the anchor rod (6) to press the backing plate assembly (100) between the outer side wall of the surrounding rock (200) and the nut (7), and the water inlet pipe (22) and the water outlet pipe (23) both extend to the outside of the secondary lining structure of the tunnel through the pre-buried pipe.

8. A method of applying prestress to an anchor rod, characterized by, The anchor rod prestress application method using the backing plate assembly (100) of any one of claims 1 and 3-6 comprises the following steps: The front end of the anchor rod (6) is anchored inside the tunnel surrounding rock (200). The backing plate assembly (100) is immersed in water, and the outer interfaces of the data line (51), the water inlet pipe (22) and the water outlet pipe (23) are ensured not to be immersed in water, after the self-expanding cement cartridge (4) of the front backing plate layer (3) no longer generates bubbles, the backing plate assembly (100) is sleeved outside the tail end of the anchor rod (6) along the shaft hole (110) of each backing plate layer, and the nut (7) is threadedly connected to the tail end of the anchor rod (6) to press the backing plate assembly (100) between the outer side wall of the surrounding rock (200) and the nut (7).

9. A method according to claim 8, c h a r a c t e r i s e d i n that The backing plate assembly (100) further comprises a pressure-sensitive element (5) which is squeezed in the gap between the front side surface of the solid metal body (11) of the rear backing plate layer (1) and the rear side surface of the middle backing plate layer (2), a data line (51) is connected to the pressure-sensitive element (5), and the data output end of the data line (51) extends to the outside of the gap. The anchor rod prestress application method further comprises connecting the data output end of the data line (51) to a display device, monitoring the pressure data value through the display device, and adding water to the water inlet pipe (22) to supplement the prestress of the anchor rod (6) when the monitored pressure data value decays to a preset value.

10. The method according to claim 8, wherein The step of anchoring the front end of the anchor rod (6) inside the tunnel surrounding rock (200) comprises: Drilling an anchor rod insertion hole (210) into the tunnel surrounding rock (200), inserting the front end of the anchor rod (6) into the drilled anchor rod insertion hole (210), and pressing a resin anchoring agent (300) into the anchor rod insertion hole (210).

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