A reinforcement system and monitoring method for broken sandstone rock mass on the roof of a grotto temple

Abstract

The present invention provides a reinforcement system and monitoring method for the broken sandstone rock mass of a grotto temple roof. The reinforcement system includes: a concrete beam, which spans the top of the grotto, with its support point located outside the grotto roof; an anchor rod, which penetrates the grotto roof and the concrete beam, with its bottom end anchored to the lower surface of the grotto roof and its top end anchored to the upper surface of the concrete beam; an anchor rod dynamometer, which is mounted on the top of the anchor rod and is used to monitor the stress on the anchor rod; and a bearing plate, with its bottom end penetrating the bearing plate. An anchoring device on the bottom end of the anchor rod presses the bearing plate against the lower surface of the grotto roof. This prevents the occurrence of localized dangerous rock masses on the roof. Since grottoes belong to the field of cultural relics protection projects, during reinforcement, disturbance to the grotto body is minimized as much as possible, and real-time, high-precision monitoring of the grotto body is performed after reinforcement.

Description

Technical Field

[0001] The present invention belongs to the technical field of grotto reinforcement, support and monitoring, and in particular relates to a reinforcement system and a monitoring method for a broken sandstone rock mass on a grotto temple roof. Background Art

[0002] Since their excavation, the stability of the grottoes has been vulnerable to cracks, water seepage, rock weathering, and human disturbances, as the geological environment has evolved. Cracks are the primary factor contributing to their instability. For flat-roofed grottoes, years of weathering, self-weight stress, and the redistribution of stress after excavation have led to numerous cracks in the walls and ceilings. Cracks in the cave roof, in particular, can easily divide the roof into several separate units, destabilizing the surrounding rock and posing a risk of collapse.

[0003] In the grotto reinforcement project, it is generally divided into the reinforcement of the cave cliff and the cave itself. Common methods include grouting of cracks around the cave, spray anchor reinforcement of the cave cliff, and reinforcement of the cave roof and side walls with anchor rods / cables. Conventional anchor rods have very small deformation, so prestress is generally applied to them by screwing nuts. The prestress value applied by this method is very small, which can only serve the purpose of reinforcement but not monitoring the reinforced rock mass.

[0004] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies in the prior art. Summary of the Invention

[0005] The object of the present invention is to provide a method for reinforcing and monitoring the broken sandstone rock mass of the top plate of a grotto temple, so as to at least solve the above-mentioned problems existing in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A reinforcement system for a broken sandstone rock mass of a grotto temple roof, the reinforcement system comprising:

[0008] A concrete beam, the concrete beam spanning the upper part of the grotto, with the support point of the concrete beam located outside the grotto roof;

[0009] Anchor rods, which penetrate the cave roof and concrete beams, with the bottom end of the anchor rods anchored on the lower surface of the cave roof and the top end of the anchor rods anchored on the upper surface of the concrete beams;

[0010] Anchor dynamometer, which is installed at the top of the anchor and is used to monitor the stress condition of the anchor;

[0011] The bottom end of the anchor rod passes through the bearing plate, and the anchoring device on the bottom end of the anchor rod presses the bearing plate onto the lower surface of the cave roof.

[0012] In the above-mentioned reinforcement system for the broken sandstone rock mass of the cave temple roof, preferably, the concrete beam is an N-shaped beam, and the two vertical sides of the N-shaped beam are arranged above the cave and are located outside the vertical projection of the cave roof;

[0013] The horizontal side of the n-shaped beam is erected on the two vertical sides, and the horizontal side of the n-shaped beam spans above the cave ceiling, and there is a gap between the horizontal side of the n-shaped beam and the cave ceiling;

[0014] The concrete beam is a reinforced concrete structure.

[0015] In the reinforcement system for the broken sandstone rock mass of the cave temple roof as described above, preferably, an anti-rust sleeve is provided on the anchor rod between the horizontal side of the N-shaped beam and the cave roof, and the anti-rust sleeve is used to protect the anchor rod.

[0016] In the reinforcement system for the broken sandstone rock mass of the cave temple roof as described above, preferably, the diameter of the anti-rust sleeve is smaller than the diameter of the borehole where the anchor rod is located, so that the anti-rust sleeve can partially extend into the borehole, and a water-draining and sealing treatment is performed between the anti-rust sleeve and the borehole.

[0017] The above-mentioned reinforcement system for the broken sandstone rock mass of the cave temple roof preferably comprises a plurality of n-shaped beams arranged in parallel in the extension direction of the cave, and a plurality of anchor rods are anchored and supported on the horizontal side of each n-shaped beam;

[0018] The bearing plate connected to the bottom of each anchor rod is an integrated structure, and the bearing plate covers the lower surface of the cave roof.

[0019] As described above, in the reinforcement system for the broken sandstone rock mass of the cave temple roof, preferably, the bearing plate is provided with an upper recess at the drilling position corresponding to the anchor rod installation, the upper recess is embedded in the drill hole, the bottom end of the anchor rod passes through the bottom of the groove of the upper recess and extends into the upper recess, and a nut is threadedly connected to the bottom end of the anchor rod.

[0020] In the reinforcement system for the broken sandstone rock mass of the cave temple roof as described above, preferably, the top of the anchor rod passes through the upper surface of the horizontal side of the n-shaped beam, and a first gasket, an anchor rod dynamometer, a sleeve assembly and a nut are sequentially sleeved on the top of the anchor rod from bottom to top;

[0021] The sleeve assembly includes a sleeve, a vertebral body and a second gasket. Multiple vertebral bodies are sleeved on the outer periphery of the anchor rod, and multiple vertebral bodies are aligned and extended into the sleeve; multiple second gaskets are sleeved on the outer periphery of the anchor rod, and multiple second gaskets are aligned and extended into the vertebral body.

[0022] The present application also provides a monitoring method for the broken sandstone rock mass of the grotto temple roof, the monitoring method using the reinforcement system for the broken sandstone rock mass of the grotto temple roof as described above, the monitoring method comprising the following steps:

[0023] Step 1: Clean the top of the cave and grout the surrounding rock cracks;

[0024] Step 2: Construct the concrete beams by excavating grooves symmetrically on both sides of the top plate above the cave roof, then tie the steel bars of the N-shaped beams, set up the formwork and pour concrete for the N-shaped beams;

[0025] Step 3: Drill holes on the cave roof and the N-shaped beam, and drill holes through the cave roof and the N-shaped beam at the same time;

[0026] Step 4: Install the anchor rod and the anchor rod dynamometer in the drill hole; install the anti-rust sleeve between the corresponding drill holes of the cave roof and the N-beam, and perform water-draining and sealing treatment between the anti-rust sleeve and the drill hole; then, pass the anchor rod through the N-beam, the anti-rust sleeve and the cave roof from top to bottom, and the lower end of the anchor rod passes through the carbon fiber plate and is fixed to the cave roof with a nut; the upper end of the anchor rod passes through the first gasket, the anchor rod dynamometer, the sleeve assembly and the nut is installed;

[0027] Step 5: Anchor grouting: insert the grouting pipe into the gap between the drill hole and the anchor, and grout the anchor through the grouting pipe; after the grouting solidifies, seal the cave roof and tighten the nut at the lower end of the anchor;

[0028] Step 6: Apply prestress to the anchor rod so that the upper part of the dynamometer is under pressure;

[0029] Step 7: Aging treatment: After the construction is completed, the top plate of the cave will be aged to ensure the overall color consistency of the cave.

[0030] In the monitoring method for the broken sandstone rock mass of the cave temple roof as described above, preferably, in step 4, a plurality of centering brackets are provided on the anchor rod, and the centering brackets are used to keep the anchor rod in the center position of the drill hole.

[0031] In the monitoring method for the broken sandstone rock mass of the cave temple roof as described above, preferably, in step 6, the nut on the top of the anchor rod is first removed, and a through-hole jack is installed on the top plate of the anchor rod, the front section of the through-hole jack is in contact with the first gasket, and then the anchor rod is tensioned to apply prestress, and after the prestress is applied, the nut is tightened on the top of the anchor rod.

[0032] Beneficial effects:

[0033] The present invention mainly aims at reinforcing cracked roofs of grotto temples and caves to prevent the occurrence of local dangerous rock masses on the roofs. Since grottoes belong to the field of cultural relics protection projects, when implementing the reinforcement, the disturbance to the grotto body is minimized as much as possible, and the grotto body is monitored in real time with high precision after the reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings and the accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them:

[0035] Figure 1 is a cross-sectional view of a reinforcement system according to an embodiment of the present invention;

[0036] Figure 2 A top view of a reinforcement system according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the installation of an anchor rod and an anchor rod stress gauge according to an embodiment of the present invention;

[0038] Figure 4 for Figure 3 Middle Ⅰ-Ⅰ section top view;

[0039] Figure 5 for Figure 3 Top view of section II-II.

[0040] In the figure: 1. Concrete beam; 2. Carbon fiber plate; 3. Anti-rust sleeve; 4. Anchor rod; 5. First gasket; 6. Cone; 7. Anchor rod dynamometer; 8. Sleeve; 9. Second gasket; 10. Centering bracket; 11. Grouting pipe. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0042] In the description of the present invention, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0043] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0044] According to a specific embodiment of the present invention, Figure 1-5 As shown, the present invention provides a reinforcement system for the broken sandstone rock mass of the cave temple roof. The principles of the reinforcement system and the monitoring method are as follows: the reinforcement system mainly includes an anchor axial force dynamometer, a sleeve, a cone device, an anchor gasket and a nut for fixing the cone position. Near the cave roof, the reinforcement system mainly includes a carbon fiber plate for supporting the roof.

[0045] When using the above-mentioned reinforcement system for installation, after the anchor bolt is grouted, a sleeve, anchor bolt washer, and cone device are added between the overburden rock anchor bolt dynamometer and the nut. The top of the through-hole jack is brought into contact with the washer to apply prestress to the anchor bolt. When the force is applied, the washer and cone move toward the sensor, squeezing the sensor with the sleeve, thereby compressing the sensor. After the anchor bolt is prestressed, the cone position is fixed with a nut. The anchor bolt in the rock anchoring section is fixed to the cave ceiling using carbon fiber plates and nuts. After the anchor bolt is fixed, carbon fiber plates are set up at other locations on the cave ceiling to achieve uniform stress on the cave ceiling.

[0046] Specifically, a reinforcement system for the broken sandstone rock mass of the top plate of a cave temple, the reinforcement system includes: a concrete beam 1, the concrete beam 1 spans the upper position of the cave, and the support point of the concrete beam 1 is at the periphery of the cave top plate; an anchor rod 4, the anchor rod 4 passes through the cave top plate and the concrete beam 1, the bottom end of the anchor rod 4 is anchored on the lower surface of the cave top plate, and the top end of the anchor rod 4 is anchored on the upper surface of the concrete beam 1; an anchor rod dynamometer 7, the anchor rod dynamometer 7 is installed at the top end of the anchor rod 4, and is used to monitor the stress condition of the anchor rod 4; a bearing plate, the bottom end of the anchor rod 4 passes through the bearing plate, and the anchoring device on the bottom end of the anchor rod 4 presses the bearing plate against the lower surface of the cave top plate.

[0047] The reinforcement system is provided with a bearing plate, thereby increasing the contact area between the bottom end of the anchor rod 4 and the cave roof, so that the anchor rod 4 can more evenly support the cave roof; because the real-time monitoring of the cave, which allows a very small deformation, requires a large prestress to be applied to the anchor rod 4, so that the reading of the anchor rod dynamometer 7 can be more accurate, and thus the state of the reinforced rock mass can be fed back in real time; and the reinforcement system of the present application sets a concrete beam 1 above the cave roof, and avoids the support point of the concrete beam 1 from the relatively fragile cave roof, so that the top end of the anchor rod 4 can be anchored on the relatively solid concrete beam 1, thereby being able to apply a large prestress to the anchor rod 4, making it easier to install the anchor rod dynamometer 7, thereby achieving real-time monitoring of the cave, which allows a very small deformation. In this embodiment, the anchor rod 4 adopts the NPR anchor rod 4.

[0048] Concrete beam 1 is an N-shaped beam, the two vertical sides of which are arranged above the cave and are located on the periphery of the vertical projection of the cave roof; the horizontal side of the N-shaped beam is erected on the two vertical sides, and the horizontal side of the N-shaped beam spans above the cave roof, and there is a gap between the horizontal side of the N-shaped beam and the cave roof; concrete beam 1 is a reinforced concrete structure.

[0049] The two vertical sides of the N-shaped beam are supported on the periphery of the cave roof, and the bottom of the roof is hollow, which means that the two vertical sides of the N-shaped beam are supported on the non-hollow cave, ensuring that the supporting foundation of the N-shaped beam is more solid; and the horizontal sides of the N-shaped beam are erected on the two sides, so that the horizontal sides of the N-shaped beam will not contact the cave roof, and the horizontal sides of the N-shaped beam can be set horizontally, which can ensure that the anchor dynamometer 7 is subjected to horizontal force, making the measurement more accurate and reducing the measurement error that may be caused by the unevenness of the rock layer overlying the cave.

[0050] The N-shaped beam not only ensures construction quality, but also reduces design dimensions, reduces deadweight, and facilitates maintenance. In this embodiment, the vertical sides of the N-shaped beam serve as the two buttresses for the concrete beam 1. A groove is excavated on each side above the cave roof. The N-shaped beam's reinforcement is then tied, and formwork is erected before concrete is poured. Excavating the groove at the cave roof allows the N-shaped beam to be more securely positioned there.

[0051] An anti-rust sleeve 3 is provided on the anchor rod 4 between the horizontal edge of the N-beam and the cave roof to protect the anchor rod 4. Since the anchor rod 4 between the horizontal edge of the N-beam and the cave roof is exposed to the air, this part of the anchor rod 4 is very prone to rust and corrosion. The anti-rust sleeve 3 can provide good protection for the anchor rod 4.

[0052] The diameter of the anti-rust sleeve 3 is smaller than the diameter of the borehole where the anchor rod 4 is located, so that the anti-rust sleeve 3 can partially extend into the borehole, and a water-draining and sealing treatment is performed between the anti-rust sleeve 3 and the borehole. The partially exposed portion of the anchor rod 4 is treated with anti-corrosion, and the size of the anti-rust sleeve 3 is slightly smaller than the size of the borehole so that the contact position between the anti-rust sleeve 3, the concrete beam 1 and the rock can be embedded in the borehole. After the anti-rust sleeve 3 is placed, the upper and lower contact positions are waterproofed and sealed. In this embodiment, the diameter of the anti-rust sleeve 3 is smaller than the borehole, so that the anti-rust sleeve 3 can be inserted into the borehole; filling the space between the anti-rust sleeve 3 and the borehole with sealant can ensure that the anti-rust sleeve 3 can have a better sealing and protective effect on the anchor rod 4.

[0053] A plurality of n-shaped beams are arranged in parallel in the extension direction of the cave, and a plurality of anchor rods 4 are anchored and supported on the horizontal side of each n-shaped beam; the bearing plate connected to the bottom of each anchor rod 4 is an integrated structure, and the bearing plate covers the lower surface of the cave roof.

[0054] In this embodiment, multiple N-shaped beams are arranged in parallel to ensure more uniform support for the cave roof. The supporting plate is a carbon fiber plate 2, a one-piece structure that covers the lower surface of the cave roof, ensuring greater load-bearing capacity. Specifically, the supporting plate comprises multiple U-shaped plates joined together, with anchor rods 4 connected to parallel edges of the supporting plates to provide uniform support.

[0055] The bearing plate is provided with an upper recess at the drilling position corresponding to the installation of the anchor rod 4. The upper recess is embedded in the drilling hole. The bottom end of the anchor rod 4 passes through the bottom of the groove of the upper recess and extends into the upper recess. A nut is threadedly connected to the bottom end of the anchor rod 4.

[0056] The bottom of the anchor rod 4 is anchored to the lower surface of the cave ceiling by a nut, and the bearing plate is also lowered and pressed against the cave ceiling. In this embodiment, by providing an upper recess on the bearing plate, not only can the nut at the bottom of the anchor rod 4 be hidden in the upper recess, but the upper recess can also serve as a positioning member between the bearing plate and the drill hole to ensure the accuracy of the installation position of the bearing plate. Finally, the upper recess is equivalent to a reinforcement member on the bearing plate, and the cross-section of the upper recess is circular. The upper recess is a cylindrical shape protruding upward on the bearing plate, so that the nut for tightening the anchor rod 4 does not need to be directly pressed against the bearing plate, and the force is transferred to the upper recess, which also greatly improves the situation where the bearing plate is subjected to high stress, ensuring that the bearing plate has a longer service life.

[0057] The top end of the anchor rod 4 passes through the upper surface of the horizontal side of the n-shaped beam, and the first gasket 5, the anchor rod dynamometer 7, the sleeve assembly and the nut are sequentially sleeved on the top end of the anchor rod 4 from bottom to top; the sleeve assembly includes a sleeve 8, a vertebral body 6 and a second gasket 9, and multiple vertebral bodies 6 are sleeved on the periphery of the anchor rod 4, and multiple vertebral bodies 6 are matched and extended into the sleeve 8; multiple second gaskets 9 are sleeved on the periphery of the anchor rod 4, and multiple second gaskets 9 are matched and extended into the vertebral body 6.

[0058] In this embodiment, the plurality of vertebrae 6 are positioned around the plurality of second gaskets 9, and the sleeve 8 is positioned around the plurality of vertebrae 6. The second gaskets 9 are wedge-shaped gaskets. By providing two sets of wedge-shaped structures (i.e., the wedge-shaped gaskets and the vertebrae 6), the sleeve 8 can be more securely locked on the anchor rod 4. At the same time, a greater preload force is applied to the anchor rod 4, causing the sleeve 8 to press against the anchor rod dynamometer 7. The first gasket 5 is a steel gasket. When the first gasket 5 is aligned, it has a frustum shape with a wider upper portion and a narrower lower portion.

[0059] The wedge-shaped washer is used to ensure that the anchor rod 4 can pass through the cone before the washer is placed. It is also used to secure the anchor rod 4 after the anchor rod 4 passes through the cone. The size of the wedge-shaped washer is consistent with the size of the front section of the through-hole jack. When the through-hole jack is used to prestress the anchor rod 4, the force applied by the tensioning machine is mainly applied to the washer position, and the degree of tension is determined by the downward movement of the washer. In other words, the installation of the wedge-shaped washer makes it easier to prestress the anchor rod 4.

[0060] The present application also provides a monitoring method for a broken sandstone rock mass on a grotto temple roof, the monitoring method using the above-mentioned reinforcement system for the broken sandstone rock mass on the grotto temple roof, and the monitoring method comprising the following steps:

[0061] Step 1: Clean the top of the cave and grout the surrounding rock cracks; on the one hand, ensure the stability of the cave top rock; on the other hand, prevent water seepage from the cave top, providing a seepage channel for rainwater to penetrate into the cave, affecting the stability of the overlying rock layer of the cave and affecting the grouting effect.

[0062] Step 2: Construct concrete beam 1 by excavating grooves symmetrically on both sides of the top plate above the cave roof, then tie the steel bars of the N-shaped beam, set up the formwork and pour concrete on the N-shaped beam;

[0063] Step 3: Drill holes on the cave roof and the N-shaped beam, and the holes penetrate the cave roof and the N-shaped beam at the same time. In this embodiment, the drilling position is determined according to the expansion of the cracks in the cave roof. While drilling above the cave roof, steel columns are used inside the cave to temporarily support the cave to prevent the drilling from causing instability of the cave roof. The monitoring data of the steel columns is observed at all times and the monitoring data is fed back to the construction.

[0064] Step 4: Install the anchor rod 4 and the anchor rod dynamometer 7 in the drilled hole. Install the anti-rust sleeve 3 between the corresponding drilled holes in the cave roof and the N-beam, and perform a water-draining and sealing treatment between the anti-rust sleeve 3 and the drilled hole. Then, the anchor rod 4 is passed through the N-beam, the anti-rust sleeve 3, and the cave roof from top to bottom. The lower end of the anchor rod 4 passes through the carbon fiber plate 2 and is fixed to the cave roof with a nut. The upper end of the anchor rod 4 passes through the first gasket 5, the anchor rod dynamometer 7, the sleeve assembly, and the nut is installed. In step 4, multiple centering brackets 10 are installed on the anchor rod 4 to maintain the anchor rod 4 in the center of the drilled hole, so that the anchor rod 4 remains vertical.

[0065] Step 5: Grouting the anchor rod 4, inserting the grouting pipe 11 into the gap between the drill hole and the anchor rod 4, and grouting the anchor rod 4 through the grouting pipe 11; after the grouting solidifies, the cave roof is sealed and the nut at the lower end of the anchor rod 4 is tightened; the lower end of the anchor rod 4 is tightened to facilitate subsequent application of prestress;

[0066] Step 6: Apply prestress to the anchor rod 4 so that the upper part of the dynamometer is subjected to pressure; in step 6, remove the nut on the top of the anchor rod 4 first, install a through-hole jack on the top plate of the anchor rod 4, and the front section of the through-hole jack contacts the first gasket 5, then tension the anchor rod 4 to apply prestress, and after the prestress is applied, tighten the nut at the top of the anchor rod 4; after placing the jack in position, tension the anchor rod 4. At this time, the force applied to the anchor rod 4 is opposite to the force applied to the gasket, so that the cone moves in the direction of the force applied to the gasket. The cone is connected to the sleeve 8. When the cone moves, the sleeve 8 squeezes the anchor rod dynamometer 7, so that the upper part of the dynamometer is subjected to pressure, thereby achieving the purpose of applying prestress to the anchor rod 4 and causing the anchor rod dynamometer 7 to be compressed.

[0067] Step 7: Aging treatment: After the construction is completed, the top of the cave will be aged to ensure the overall color of the cave is consistent. In order to maintain the overall artistic value of the cave, the top of the cave needs to be aged after the construction is completed to ensure that the color of the construction area does not affect the overall color of the cave and does not damage the viewing experience of the cave.

[0068] In summary, in the technical solutions of the reinforcement system and monitoring method for the broken sandstone rock mass of the cave temple roof provided by the present invention, since real-time monitoring of projects such as caves with very small allowable deformation is required, it is necessary to apply a large prestress to the anchor rods so that the readings of the anchor dynamometers can be more accurate, and thus real-time feedback on the status of the reinforced rock mass can be achieved; and the reinforcement system of the present application can apply a large prestress to the anchor rods by setting a concrete beam above the cave roof, which makes it easier to install the anchor dynamometer, thereby realizing real-time monitoring of projects such as caves with very small allowable deformation.

[0069] It will be understood that the above description is merely exemplary and the embodiments of the present application do not limit this.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A reinforcement system for the broken sandstone rock mass of a cave roof, characterized in that: The reinforcement system includes: A concrete beam, the concrete beam spanning the upper part of the grotto, with the support point of the concrete beam located outside the grotto roof; Anchor rods, which penetrate the cave roof and concrete beams, with the bottom end of the anchor rods anchored on the lower surface of the cave roof and the top end of the anchor rods anchored on the upper surface of the concrete beams; Anchor dynamometer, which is installed at the top of the anchor and is used to monitor the stress condition of the anchor; A bearing plate, wherein the bottom end of the anchor rod passes through the bearing plate, and an anchoring device on the bottom end of the anchor rod presses the bearing plate against the lower surface of the cave roof. The concrete beam is an N-shaped beam, and the two vertical sides of the N-shaped beam are arranged above the cave and are located outside the vertical projection of the cave roof. The horizontal side of the n-shaped beam is erected on the two vertical sides, and the horizontal side of the n-shaped beam spans above the cave ceiling, and there is a gap between the horizontal side of the n-shaped beam and the cave ceiling; The concrete beam is a reinforced concrete structure; A plurality of n-shaped beams are arranged in parallel in the extension direction of the cave, and a plurality of anchor rods are anchored and supported on the horizontal side of each n-shaped beam; The bearing plate connected to the bottom of each anchor rod is an integrated structure, and the bearing plate covers the lower surface of the cave roof; the bearing plate is a carbon fiber plate; The bearing plate is provided with an upper concave portion corresponding to the drill hole position where the anchor rod is installed. The upper concave portion is embedded in the drill hole. The bottom end of the anchor rod passes through the bottom of the groove of the upper concave portion and extends into the upper concave portion. A nut is threadedly connected to the bottom end of the anchor rod. The top of the anchor rod passes through the upper surface of the horizontal side of the n-shaped beam, and the first washer, the anchor rod dynamometer, the sleeve assembly and the nut are sequentially sleeved on the top of the anchor rod from bottom to top; The sleeve assembly includes a sleeve, a cone and a second gasket. Multiple cones are sleeved on the outer periphery of the anchor rod, and multiple cones are matched and extended into the sleeve; multiple second gaskets are sleeved on the outer periphery of the anchor rod, and multiple second gaskets are matched and extended into the cone.

2. The reinforcement system for the broken sandstone rock mass of the cave roof according to claim 1 is characterized in that: An anti-rust sleeve is provided on the anchor rod between the horizontal edge of the N-shaped beam and the cave roof to protect the anchor rod.

3. The reinforcement system for the broken sandstone rock mass of the cave roof according to claim 2 is characterized in that: The diameter of the rust-proof sleeve is smaller than the diameter of the drill hole where the anchor rod is located, so that the rust-proof sleeve can partially extend into the drill hole, and a waterproof sealing treatment is performed between the rust-proof sleeve and the drill hole.

4. A monitoring method for a broken sandstone rock mass on a cave roof, the monitoring method using the reinforcement system for a broken sandstone rock mass on a cave roof as claimed in any one of claims 1 to 3, characterized in that: The monitoring method comprises the following steps: Step 1: Clean the top of the cave and grout the surrounding rock cracks; Step 2: Construct the concrete beams by excavating grooves symmetrically on both sides of the top plate above the cave roof, then tie the steel bars of the N-shaped beams, set up the formwork and pour concrete for the N-shaped beams; Step 3: Drill holes on the cave roof and the N-shaped beam, and drill holes through the cave roof and the N-shaped beam at the same time; Step 4: Install the anchor rod and the anchor rod dynamometer in the drill hole; install the anti-rust sleeve between the corresponding drill holes of the cave roof and the N-beam, and perform waterproof sealing treatment between the anti-rust sleeve and the drill hole; then, pass the anchor rod through the N-beam, the anti-rust sleeve and the cave roof from top to bottom, and the lower end of the anchor rod passes through the carbon fiber plate and is fixed to the cave roof with a nut; the upper end of the anchor rod passes through the first gasket, the anchor rod dynamometer, the sleeve assembly and the nut is installed; Step 5: Anchor grouting: insert the grouting pipe into the gap between the drill hole and the anchor, and grout the anchor through the grouting pipe; after the grouting solidifies, seal the cave roof and tighten the nut at the lower end of the anchor; Step 6: Apply prestress to the anchor rod so that the upper part of the dynamometer is under pressure; Step 7: Aging treatment: After the construction is completed, the top plate of the cave will be aged to ensure the overall color consistency of the cave.

5. The method for monitoring the broken sandstone rock mass of the cave roof according to claim 4, characterized in that: In step 4, a plurality of centering brackets are sleeved on the anchor rod, and the centering brackets are used to keep the anchor rod in the center position of the drill hole.

6. The method for monitoring the broken sandstone rock mass of the cave roof according to claim 4, characterized in that: In step 6, the nut at the top of the anchor rod is removed first, and a through-hole jack is installed at the top of the anchor rod, with the front end of the through-hole jack in contact with the first gasket. The anchor rod is then tensioned to apply prestress, and after the prestress is applied, the nut is tightened at the top of the anchor rod.

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