A hydrophobic anti-corrosion anchor rod for roof surrounding rock instability early warning and a use method thereof

Abstract

The application discloses a hydrophobic anti-corrosion anchor rod for roof surrounding rock instability early warning and a use method, and relates to the technical field of anchor rod support.The anchor rod comprises a hydrophobic anchor rod, a monitoring and early warning assembly and a drainage assembly; the hydrophobic anchor rod comprises a hollow rod body, a plurality of groups of flow guide holes are uniformly arranged on the surface of the hollow rod body in the axial direction, an epoxy resin anti-corrosion outer coating is covered on the outer wall of the hollow rod body, and a plurality of magnesium alloy anode blocks are installed on the inner wall of the hollow rod body; the monitoring and early warning assembly comprises a first water pressure sensor, a second water pressure sensor, a flow sensor and a display panel; and the drainage assembly comprises a drainage interface, a water guide pipe and a drainage groove.The application judges the damage degree of the roof surrounding rock by calculating the water permeability coefficient of the roof surrounding rock, displays early warning information on the display panel in real time, and simultaneously realizes the triple functions of surrounding rock hydrophobic pressure reduction, anchor rod anti-corrosion and roof instability early warning, so that the problems of easy corrosion of the anchor rod in the water-rich roof roadway, disconnection of drainage and monitoring and early warning lag can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of anchor bolt support technology, specifically to a hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability and its application method. Background Technology

[0002] In the support engineering of water-rich rock strata, long-term seepage of groundwater in the roof aquifer not only weakens the mechanical strength of the surrounding rock and aggravates the development of fractures, greatly increasing the risk of roof instability and collapse, but also directly corrodes metal support components, causing anchor bolt corrosion failure and seriously shortening the service life of the support system. It is one of the key problems restricting safe and efficient production in mines.

[0003] Currently, there are still many shortcomings in the treatment and support technologies for water-rich roof roadways. First, drainage and pressure reduction are independent of roadway support, resulting in cumbersome and redundant construction procedures. In existing projects, drainage and support are carried out independently, leading to numerous drilling operations, high labor and equipment costs, and an inability to achieve "multi-purpose drilling," resulting in poor project economics. Second, early warning of roof instability is delayed, and the reliability of monitoring results is insufficient. Existing roof monitoring mainly relies on displacement and stress sensors, which can only capture instability signals after macroscopic deformation and significant stress changes occur in the surrounding rock, resulting in poor early warning capabilities. At the same time, most monitoring systems require the installation of transmission cables, which lead to high equipment failure rates and maintenance difficulties in the humid and dusty underground environment, making it difficult to achieve long-term real-time online monitoring of the entire cross-section. Third, the corrosion rate of metal structures is rapid in water-rich environments. Among the current mainstream anti-corrosion solutions, hot-dip galvanizing and thermal spraying zinc coating anti-corrosion processes require dedicated hot processing production lines, resulting in high zinc raw material consumption and high processing energy consumption, significantly increasing the cost of anti-corrosion treatment for a single anchor bolt, lacking economic efficiency and practicality.

[0004] In summary, there is an urgent need for a multi-functional anchor bolt that can integrate "support-drainage-early warning-corrosion prevention" to solve a series of problems such as multiple on-site construction procedures, delayed early warning, and high corrosion prevention costs, thereby meeting the engineering requirements for long-term safe use of water-rich roof roadways. Summary of the Invention

[0005] To address the aforementioned issues, this invention discloses a hydrophobic anti-corrosion anchor bolt and method for early warning of roof rock instability. It integrates hydrophobic pressure reduction, low-cost anti-corrosion, and instability early warning functions, and features convenient construction, high system monitoring efficiency, and strong data reliability.

[0006] According to the present invention, a hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability is provided, comprising a hydrophobic anchor bolt, a monitoring and early warning component, and a drainage component; The hydrophobic anchor bolt includes a hollow rod body, a tray and a nut. Multiple sets of drainage holes are evenly distributed along the axial direction on the surface of the hollow rod body. The outer wall of the hollow rod body is covered with an epoxy resin anti-corrosion coating. Several magnesium alloy anode blocks are installed on the inner wall of the hollow rod body. The monitoring and early warning component includes a first water pressure sensor, a second water pressure sensor, a flow sensor, and a display panel. The first water pressure sensor is located at the upper part of the hollow rod, the second water pressure sensor is located at the midpoint of the axial direction of the hollow rod, and the flow sensor is located at the lower part of the hollow rod. The first water pressure sensor, the second water pressure sensor, and the flow sensor are all installed inside the hollow rod and are wirelessly connected to the display panel. The display panel is installed on the exposed end of the hollow rod through a display panel fixing sleeve and has a built-in microcontroller, a data storage module, and a graded early warning module. The drainage assembly includes a drainage interface, a water guide pipe, and a drainage trough; the drainage interface is located at the bottom of the hollow rod and communicates with the interior of the hollow rod; a solenoid valve is installed inside the drainage interface; one end of the water guide pipe is detachably connected to the drainage interface, and the other end is connected to the drainage trough.

[0007] Preferably, a first filter screen is embedded in the inner wall of the hollow rod, and the magnesium alloy anode block is disposed between the outer surface of the first filter screen and the inner wall of the hollow rod; a second filter screen is connected to the inner side of the first filter screen by a snap fastener, and the first water pressure sensor, the second water pressure sensor and the flow sensor are all embedded in the inner surface of the second filter screen.

[0008] Preferably, the first filter screen is a stainless steel filter screen, which is embedded and fixed to the inner wall of the hollow rod with an interference fit; the second filter screen is a non-woven composite filter screen, and the filtration pore size of the second filter screen is smaller than that of the first filter screen.

[0009] Preferably, a water-sealed expansion sleeve is fitted onto the lower part of the hollow rod, and the water-sealed expansion sleeve is positioned above the tray.

[0010] Preferably, a limiting ring is integrally formed on the top outer wall of the hollow rod body, and an expansion shell body and a conical expansion head are sleeved on the top of the hollow rod body. The expansion shell body is located above the limiting ring, and its inner diameter is smaller than the outer diameter of the limiting ring. The outer surface of the expansion shell body is provided with anti-slip teeth. The conical expansion head is located between the expansion shell body and the hollow rod body. The inner surface of the conical expansion head is provided with an internal thread that is threaded to the hollow rod body, and its outer surface is provided with an anti-rotation limiting block. The inner surface of the expansion shell body is provided with a limiting groove that cooperates with the anti-rotation limiting block.

[0011] Another method for using the hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability, as described above, disclosed in this invention, includes the following steps: S1. Drill holes at the designed location in the surrounding rock of the roof, insert the assembled drainage anchor into the drill hole, rotate the hollow rod body clockwise so that the conical expansion head moves downward along the axial direction of the hollow rod body, push the expansion shell body to open radially, and clamp the hole wall to achieve anchoring; S2. First, install the water-sealed expansion sleeve, then install the tray and nut, and finally tighten the nut to fix the tray. S3. Connect the drain interface to the water pipe, connect the water pipe to the drain trough, and the system will automatically enter the initialization mode to complete the hydrostatic pressure measurement and the calibration of the initial reference permeability coefficient K0. S4. Enter normal monitoring mode. The second water pressure sensor and flow sensor collect data in real time and wirelessly transmit it to the display panel. The microcontroller calculates the real-time permeability coefficient K and ratio K / K0, and then transmits the information to the graded early warning module for early warning. S5. Take corresponding graded disposal measures according to different levels of damage; S6. Regularly use the extended nylon brush to clean the blockage between the filter screens inside the rod. When cleaning, the drain interface needs to be removed. After cleaning, reinstall the drain interface and repeat the S3-S5 operation.

[0012] Preferably, in S3, the initialization mode includes the following steps: S31. The microcontroller closes the solenoid valve, and the water in the surrounding rock enters the hollow rod body through the guide hole. S32. The flow sensor monitors the flow rate changes in the hollow rod in real time. When the flow rate readings are all 0 for three consecutive times and remain so for more than five minutes, it is determined that the hollow rod is completely filled with water and the water flow is still. S33. At this time, the first water pressure sensor measures the original static water pressure P1 of the surrounding rock and transmits it to the display panel. S34. After the measurement is completed, the microcontroller automatically opens the solenoid valve, and the system enters the initial reference permeability coefficient measurement mode. S35. Read the measured value Q of the flow sensor and calculate the total head difference Δh. After the flow rate Q and the total head difference Δh stabilize, calculate the real-time permeability coefficient K. When the change rate of the real-time permeability coefficient K value of five consecutive measurements is less than 5%, take the average value of the five measurements as the initial process number K0 and store it.

[0013] The preferred method for calculating the total head difference Δh includes the following steps: S351. Determine the reference plane as the horizontal plane of the tunnel floor; S352. Pre-measure and store the installation height z1 of the first water pressure sensor and the installation height z2 of the second water pressure sensor; S353, Read the measured value P2 of the second water pressure sensor; S354. Calculate the first total head H1=z1+P1 / (ρg) and the second total head H2=z2+P2 / (ρg) respectively, where ρ is the density of water and g is the acceleration due to gravity. S355. Calculate the total head difference Δh = H1 - H2.

[0014] Preferably, the real-time permeability coefficient K value calculation formula is K=Q•ln(R / r0) / (2πL•Δh), where R is the dewatering influence radius, which is determined through on-site pumping tests; r0 is the inner diameter of the anchor rod; L is the axial length of the hollow rod body.

[0015] Preferably, the graded early warning in S4 is specifically as follows: when K / K0≤1.5, it is determined as a normal state, and no indicator light is on; when 1.5<K / K0≤3, it is determined as slight damage, and a blue indicator light is on; when 3<K / K0≤5, it is determined as moderate damage, and a yellow indicator light is on; when K / K0>5, it is determined as severe damage, a red indicator light is on and an acousto-optic alarm is triggered.

[0016] Compared with the prior art, the advantages of the hydrophobic anti-corrosion anchor rod for roof surrounding rock instability early warning and the use method thereof disclosed in the present invention are as follows: 1. The present invention integrates the anchoring support and active dewatering functions into a single anchor rod, realizing multi-purpose use of one rod, eliminating the independent process of separately constructing dewatering holes, reducing the drilling workload, and significantly lowering labor and equipment costs.

[0017] 2. The present invention takes the groundwater of the surrounding rock as the core monitoring medium, and multiple sensors synchronously collect seepage data to calculate the permeability coefficient, so that the monitoring dimension is more comprehensive and accurate. Meanwhile, the supporting graded early warning mechanism accurately matches the multi-dimensional engineering requirements on site.

[0018] 3. The present invention adopts a dual anti-corrosion scheme of epoxy resin outer coating plus embedded magnesium alloy anode block, which does not require the hot-dip galvanizing process with high energy consumption and high material consumption, greatly reduces material and construction costs, is easy to install and can prolong the support service life. Brief Description of the Drawings

[0019] In order to more clearly describe the technical solutions of the embodiments of the present invention or the prior art, the accompanying drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0020] Figure 1 is a schematic diagram of the arrangement of the present invention in water-bearing surrounding rock.

[0021] Figure 2 is a longitudinal sectional view of the anchor rod in an unanchored state.

[0022] Figure 3 is a longitudinal sectional view of the anchor rod in an anchored state.

[0023] Figure 4 is a three-dimensional structural diagram of the anchor head part of the anchor rod.

[0024] Figure 5 This is a cross-sectional view of the anchor bolt.

[0025] Figure 6 This is a longitudinal cross-sectional view of the drainage interface.

[0026] Figure 7 This is a diagram for determining the instability state of the surrounding rock of the roof.

[0027] In the diagram: 1-surrounding rock; 2-drainage anchor; 21-hollow rod body; 211-drainage hole; 212-epoxy resin anti-corrosion outer coating; 213-first filter screen; 214-second filter screen; 215-clasp; 216-magnesium alloy anode block; 22-expansion shell body; 23-conical expansion head; 24-limiting ring; 25-water-sealing expansion sleeve; 26-tray; 27-nut; 3-monitoring and early warning component; 31-first water pressure sensor; 32-second water pressure sensor; 33-flow sensor; 34-display panel fixing sleeve; 35-display panel; 4-drainage interface; 41-solenoid valve; 5-water guide pipe; 51-spring clamp; 6-drainage trough. Detailed Implementation

[0028] The specific embodiments of the present invention will be briefly described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Figures 1-7 A preferred embodiment of the present invention is shown and analyzed in detail.

[0030] like Figure 1 The diagram illustrates a drainage-type anti-corrosion anchor bolt for early warning of roof instability. It is installed in the roof surrounding rock 1, which has a water-bearing sandstone structure. The anchor bolts include multiple drainage anchor bolts 2, a monitoring and early warning component 3, and a drainage component. The drainage anchor bolts 2 are arranged along the roadway roof at the designed spacing. The spacing and arrangement of the drainage anchor bolts 2 can be determined based on the roadway roof support design and on-site hydrogeological conditions. To ensure a continuous drainage and pressure reduction effect from the multiple drainage anchor bolts 2, the spacing is preferably less than or equal to the drainage influence range. The top of each drainage anchor bolt 2 is anchored into a stable rock layer (water-bearing sandstone), and the tail end is connected to a drainage interface 4. A water guide pipe 5 concentrates the drainage from the multiple drainage anchor bolts 2 and discharges it to a drainage trough 6 on the side of the roadway, achieving orderly drainage of water from the surrounding rock 1 and thus reducing the softening effect of groundwater on the roof. The monitoring and early warning component 3 is installed for each drainage anchor bolt 2, collecting seepage parameters in real time and issuing early warnings via a display panel 35.

[0031] like Figure 2 , 3As shown, the hydrophobic anchor bolt 2 includes a hollow rod body 21, a tray 26, and a nut 27. The tray 26 and nut 27 are sequentially fitted onto the exposed end of the hollow rod body 21. The tray 26 is used to evenly transfer the anchoring force of the anchor bolt to the surface of the surrounding rock 1, and the nut 27 is used to apply the pre-tightening torque. The hollow rod body 21 integrates monitoring, filtration, and anti-corrosion functional components. Multiple sets of guide holes 211 are evenly distributed axially on the surface of the hollow rod body 21, with four guide holes 211 evenly distributed circumferentially around the hollow rod body 21, used to guide accumulated water in the fissures of the surrounding rock 1 into the internal flow channels of the hollow rod body 21. A water-sealable expansion sleeve 25 is fitted onto the lower part of the hollow rod body 21. The water-sealable expansion sleeve 25 is located above the tray 26 and is made of water-swellable rubber, used to fill the annular gap between the anchor hole opening and the hollow rod body 21, preventing water from the surrounding rock 1 from seeping out along the outer wall of the hollow rod body 21 into the roadway. Figure 4As shown, a limiting ring 24 is integrally formed on the top outer wall of the hollow rod 21. An expansion shell body 22 and a conical expansion head 23 are fitted onto the top of the hollow rod 21. The expansion shell body 22 is positioned above the limiting ring 24, with an inner diameter smaller than the outer diameter of the limiting ring 24 but slightly larger than the outer diameter of the hollow rod 21. The upper part of the expansion shell body 22 is a two-part cast steel structure, with anti-slip serrations machined on its outer surface to increase friction with the anchor hole wall. The limiting ring 24 restricts the axial downward movement of the expansion shell body 22. The inner diameter of the expansion shell body 22 is larger than the outer diameter of the hollow rod 21, creating a radial assembly gap between the expansion shell body 22 and the hollow rod 21. The conical expansion head 23 is positioned between the expansion shell body 22 and the hollow rod 21. The inner surface of the conical expansion head has internal threads that connect with the hollow rod 21, and its outer surface has an anti-rotation limiting block. The inner surface of the expansion shell body 22 has a limiting groove that mates with the anti-rotation limiting block. During installation, the conical expansion head 23 penetrates deep into the bottom of the hole and contacts the bottom of the hole, exerting a certain frictional force. When the hollow rod 21 is rotated, the conical expansion head initially remains stationary, while the hollow rod 21 moves axially upward relative to the conical expansion head, and the expansion shell body 22 also moves upward accordingly. At this time, the conical expansion head initially embeds into the expansion shell body 22 and radially expands the expansion shell body 22, so that the outer wall of the expansion shell body 22 contacts the surrounding rock 1 of the hole wall, forming an initial frictional constraint and remaining stationary. When the hollow rod 21 is rotated again, the hollow rod 21 does not produce axial displacement. At the same time, due to the cooperation of the anti-rotation limiting block and the limiting groove, the conical expansion head will not rotate circumferentially, but will only move axially downward along the hollow rod 21 under the action of the threaded pair to continue expanding the expansion shell body 22, so that the outer wall of the expansion shell body 22 clamps the surrounding rock 1 of the hole wall, achieving end mechanical anchoring. After anchoring is completed and nut 27 is tightened, the water-sealed expansion sleeve 25 is pressed between the tray 26 and the surrounding rock 1 at the orifice. Upon contact with groundwater, it expands in volume, completely filling the annular gap at the orifice, thus sealing the orifice. At this time, groundwater in the surrounding rock 1 enters the hollow rod body 21 through the guide hole 211. After being filtered by two-stage filters, it flows downward along the internal flow channel of the hollow rod body 21 and flows into the drainage channel 6 through the drainage interface 4 and the water guide pipe 5, thereby achieving drainage and pressure reduction of the surrounding rock 1, thus reducing the softening and erosion effect of the aquifer water flow on the roof surrounding rock 1. Under normal operating conditions, the first water pressure sensor 31, the second water pressure sensor 32, and the flow sensor 33 collect seepage water pressure and flow parameters in real time and wirelessly transmit them to the display panel 35. The microcontroller calculates the real-time permeability coefficient of the roof rock layer using the radial seepage formula. After comparing it with the initial reference permeability coefficient, it judges the degree of damage to the surrounding rock 1 and realizes graded early warning.

[0032] like Figure 5As shown, the outer wall of the hollow rod 21 is covered with an epoxy resin anti-corrosion coating 212, formed by electrostatic spraying, creating a dense physical anti-corrosion barrier to prevent external corrosion. Four magnesium alloy anode blocks 216 are evenly distributed along the axial direction of the hollow rod 21 on its inner wall. Each magnesium alloy anode block 216 is approximately 10mm × 10mm × 50mm in size. Through electrochemical cathodic protection, corrosion preferentially occurs, thus protecting the inner wall of the metal hollow rod 21. This, together with the epoxy resin coating, forms a dual anti-corrosion system, significantly extending the service life of the anchor bolt. A first filter screen 213 is embedded in the inner wall of the hollow rod 21. The first filter screen 213 is a stainless steel filter screen with a pore size of approximately 5mm, and is interference-fitted and fixed to the inner wall of the hollow rod 21. It is used to filter large particles of silt and sand from seepage in the surrounding rock 1, preventing blockage of the internal flow channels and sensors. The first filter screen 213 is connected to the second filter screen 214 via clips 215 on its inner side. The clips 215 are stainless steel elastic clips, and three sets are evenly arranged along the axial direction of the hollow rod 21, with four clips evenly distributed around the circumference of each set. The second filter screen 214 is a non-woven composite filter screen with a pore size of 1mm, used to filter fine particles of silt in seepage water, ensuring long-term unobstructed flow between the internal sensor and the internal flow channel, forming a two-stage filtration structure with the first filter screen 213. Specifically, the first filter screen 213 is an irregularly shaped filter screen adapted to the shape of the inner wall of the hollow rod 21. At the position corresponding to the magnesium alloy anode block 216, the first filter screen 213 partially forms a raised covering portion, covering and fixing the magnesium alloy anode block 216. During installation, the magnesium alloy anode block 216 can be first installed at the corresponding position on the outer surface of the first filter screen 213, and then the first filter screen 213 can be completely embedded into the hollow rod 21.

[0033] The monitoring and early warning component 3 includes a first water pressure sensor 31, a second water pressure sensor 32, a flow sensor 33, and a display panel 35. The first water pressure sensor 31 is located in the static water cavity at the top of the hollow rod 21, approximately 300mm from the top of the hollow rod 21, and above a set of guide holes 211 at the highest point, used to measure the original static water pressure of the surrounding rock 1. The second water pressure sensor 32 is located at the axial midpoint of the hollow rod 21, used to measure the dynamic water pressure of seepage inside the hollow rod 21. The flow sensor 33 is located at the lower part of the hollow rod 21, above the drainage interface 4, and below a set of guide holes 211 at the lowest point, used to measure the drainage volume of the anchor bolt in real time. The first water pressure sensor 31, the second water pressure sensor 32, and the flow sensor 33 are all embedded in the surface of the second filter screen 214, and have a built-in low-power wireless transmission module for wireless communication with the display panel 35, eliminating the need for cabling and facilitating installation and maintenance. The display panel 35 is mounted on the exposed end of the hollow rod 21 via a display panel mounting sleeve 34. The display panel mounting sleeve 34 is an engineering plastic clamp structure that fits the outer diameter of the hollow rod 21. The display panel 35 integrates a microcontroller, a data storage module, a graded warning module, and an explosion-proof lithium battery, and has data calculation, storage, warning display, and audible and visual alarm functions. Specifically, the microcontroller is used to control the on / off state of the solenoid valve 41, collect sensor data, calculate the permeability coefficient, and issue warning signals; the data storage module is used to store the collected and calculated data; and the graded warning module can provide graded warnings based on the ratio of the real-time permeability coefficient to the initial reference permeability coefficient using indicator lights of different colors.

[0034] The drainage assembly includes a drainage interface 4, a water guide pipe 5, and a drainage channel 6. For example... Figure 6 As shown, the drain interface 4 is coaxially located at the bottom end of the hollow rod 21, threadedly connected to the hollow rod 21, and communicates with the internal flow channel of the hollow rod 21. A solenoid valve 41 is installed inside the drain interface 4. The solenoid valve 41 is an explosion-proof normally closed type, wirelessly communicating with the microcontroller of the display panel 35. Its on / off state is controlled by the microcontroller inside the display panel 35. It closes the flow channel only during the initial hydrostatic pressure calibration stage, and remains normally open during normal drainage, thus enabling the switching between hydrostatic pressure measurement and normal drainage modes. One end of the water guide pipe 5 is detachably connected to the drain interface 4, and the other end is connected to the drain trough 6. Specifically, the end of the water guide pipe 5 connected to the drain interface 4 is directly sleeved onto the outer side of the lower end of the drain interface 4, and a spring clamp 51 is used to tighten it for sealing and preventing detachment. When cleaning the accumulated residue on the two-stage filter screen, unscrew the drain interface 4 along with the solenoid valve 41 and the water guide pipe 5 as a whole, use an extended cleaning brush to clean the inside, and then reposition it.

[0035] Another method for using a hydrophobic anti-corrosion anchor bolt for early warning of instability of the surrounding rock of the roof, as described above, disclosed in this invention, includes the following steps: S1. Mark the preset points on the water-rich roof rock 1 according to the roadway roof support design drawings, and drill holes vertically to the roof. Control the drilling depth to ensure that the anchoring section of the anchor bolt enters the upper stable water-bearing sandstone layer by no less than 500mm. After drilling, clean the hole until no powder or slag is sprayed out of the hole to avoid the residue in the hole affecting the anchoring and monitoring effect. Insert the assembled drainage anchor bolt 2 into the drill hole. Use a socket wrench to engage the exposed end structure of the hollow rod body 21. Rotate the hollow rod body 21 clockwise. Utilize the mating structure of the internal thread of the conical expansion head 23 and the external thread of the hollow rod body 21 to make the conical expansion head 23 move downward along the axial direction of the hollow rod body 21, wedge into the inner side of the expansion shell body 22, and push the two halves of the expansion shell body 22 to open radially and synchronously until the anti-slip teeth on the outer surface of the expansion shell body 22 are completely embedded in the surrounding rock 1 of the hole wall. Use a torque wrench to reach the preset anchoring torque to complete the mechanical anchoring of the end.

[0036] S2. After the end anchoring is completed, install the water-sealable expansion sleeve 25, tray 26 and nut 27 in sequence on the exposed section of the hollow rod 21. Adjust the tray 26 to fit tightly against the surface of the surrounding rock 1 of the top plate. Tighten the nut 27 with a torque wrench and apply the set pre-tightening torque. At this time, the water-sealable expansion sleeve 25 is located between the surrounding rock 1 at the borehole and the hollow rod 21. When water seeps in, it will automatically expand to fill the annular gap between the borehole wall and the hollow rod 21, blocking the seepage path of groundwater along the outer wall of the hollow rod 21 and achieving borehole sealing.

[0037] S3. Secure the drainage interface 4 of the built-in solenoid valve 41 to the bottom of the hollow rod 21 by screwing it in. Then, secure one end of the water guide pipe 5 to the drainage interface 4 and connect the other end to the drainage trough 6 on the side of the tunnel. Check and confirm that the pipeline connection is not loose and there is no leakage. The display panel 35 is fixed to the exposed side of the hollow rod 21 by the display panel fixing sleeve 34, which is convenient for on-site inspection personnel to observe the data. Then, turn on the power switch of the display panel 35. After the system is powered on, it will automatically enter the initialization mode. In this mode, the microcontroller first outputs a signal to close the solenoid valve 41, so that the groundwater in the fissure of the surrounding rock 1 enters the interior of the hollow rod 21 through the guide hole 211 under the action of the water head difference. After being filtered by two-stage filter screens, it flows downward along the flow channel. The flow sensor 33 collects the flow data in the rod in real time and transmits it to the microcontroller. When the flow rate readings are all 0 for three consecutive times and remain stable for more than five minutes, it is determined that the internal cavity of the hollow rod 21 is completely filled with water and the water flow is static. At this time, the first water pressure sensor 31 collects the original static water pressure P1 of the surrounding rock 1 under this state and wirelessly transmits the data to the display panel 35 for storage. After the static water pressure measurement is completed, the microcontroller automatically controls the solenoid valve 41 to open, and the system enters the drainage state, allowing the water in the surrounding rock 1 to be continuously discharged through the anchor rod to the drainage channel 6. The measured value Q of the flow sensor 33 is read and the total head difference Δh is calculated. After the drainage flow rate Q and the total head difference Δh tend to stabilize, the microcontroller continuously calculates the real-time permeability coefficient K value at preset intervals. When the change rate of the permeability coefficient K value obtained from five consecutive calculations is less than 5%, it is determined that the seepage field has reached a stable state. The average value of the five measurements is taken as the initial reference permeability coefficient K0 and stored. After the initialization calibration is completed, the solenoid valve 41 is kept open, and the system automatically switches to the normal monitoring mode.

[0038] The method for calculating the total head difference Δh includes the following steps: S351. Determine the reference plane as the horizontal plane of the tunnel floor; S352, Pre-measure and store the installation height z1 of the first water pressure sensor 31 and the installation height z2 of the second water pressure sensor 32; S353, Read the measured value P2 of the second water pressure sensor 32; S354. Calculate the first total head H1=z1+P1 / (ρg) and the second total head H2=z2+P2 / (ρg) respectively, where ρ is the density of water and g is the acceleration due to gravity. S355. Calculate the total head difference Δh = H1 - H2.

[0039] The formula for calculating the real-time permeability coefficient K is K=Q•ln(R / r0) / (2πL•Δh), where R is the radius of influence of the drainage, that is, the effective radius of the groundwater drawdown funnel formed in the aquifer of the top plate when a single anchor rod continuously drains water, which can be determined by on-site pumping tests; r0 is the inner diameter of the hollow rod body 21 of the anchor rod; and L is the axial length of the hollow rod body 21.

[0040] S4. In normal monitoring mode, the system automatically collects monitoring data every ten minutes. The second water pressure sensor 32 collects the water pressure value at the corresponding location, and the flow sensor 33 collects the real-time drainage flow. All data is transmitted wirelessly to the microcontroller on the display panel 35. The microcontroller then calculates the real-time permeability coefficient K and the ratio K / K0 of the real-time permeability coefficient to the initial reference permeability coefficient. The graded early warning module determines the state of the surrounding rock 1 based on the ratio range and triggers the corresponding early warning. Figure 7 As shown, when K / K0≤1.5, it is judged as a normal and stable state, with no significant expansion of the fissures in the surrounding rock 1, and no indicator light on the early warning system illuminates; when 1.5<K / K0≤3, it is judged as a slightly damaged state, with micro-fissures inside the surrounding rock 1 beginning to develop and expand, and the permeability coefficient increasing slightly, and the blue indicator light illuminates; when 3<K / K0≤5, it is judged as a moderately damaged state, with the fissures in the surrounding rock 1 further expanding and connecting, the plastic zone expanding, and the permeability coefficient increasing significantly, and the yellow indicator light illuminates; when K / K0>5, it is judged as a severely damaged state, with a through-flow water-conducting fissure forming in the surrounding rock 1, posing a risk of water inrush and roof instability, and the red indicator light remains on and triggers a continuous audible and visual alarm.

[0041] S5. Implement corresponding graded response measures based on different warning levels; maintain daily monitoring frequency under normal and stable conditions, requiring no additional intervention; under minor damage conditions, arrange for inspection personnel to patrol the roof of the area every four hours, focusing on observing changes in the deformation and water seepage of the surrounding rock 1, requiring no additional support; under moderate damage conditions, install drainage anchors 2 between the existing anchors to expand the water conduit, controlling the expansion of cracks in the surrounding rock 1 through the synergistic effect of drainage and pressure reduction and anchoring support. After reinforcement, monitor the changes in permeability coefficient in real time using the anchors until... If the ratio remains stable below 1.5 for seven consecutive days, the stability of the surrounding rock 1 is effectively controlled. Under severe damage conditions, a combined support scheme of "dense drainage anchor bolt group 2 + fixed-point deep hole grouting" is adopted. First, the drainage anchor bolts 2 are installed to form dense drainage channels to quickly drain the water in the aquifer fissures and reduce the pore water pressure. If the single-point water inflow continues to increase after the installation and the permeability coefficient increases instead of decreasing, grouting is required to seal the abnormal monitoring area. Before grouting, the solenoid valve 41 of the corresponding monitoring area anchor bolt must be closed and sealing measures must be taken to prevent the grouting effect from being affected.

[0042] S6. Regularly use the extended nylon brush to clean the blockage between the filter screens inside the rod. When cleaning, the solenoid valve 41 must be closed and the drain interface 4 removed. After cleaning, the drain interface 4 should be reinstalled and the S3-S5 operation should be performed again.

[0043] The above description of the disclosed embodiments enables those skilled in the art to make and use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hydrophobic, corrosion-resistant anchor bolt for early warning of roof rock instability, characterized in that, It includes a drainage anchor (2), a monitoring and early warning component (3), and a drainage component; The hydrophobic anchor (2) includes a hollow rod body (21), a tray (26) and a nut (27). The hollow rod body (21) has multiple sets of guide holes (211) evenly distributed along the axial direction on its surface. The outer wall of the hollow rod body (21) is covered with an epoxy resin anti-corrosion coating (212). Several magnesium alloy anode blocks (216) are installed on the inner wall of the hollow rod body (21). The monitoring and early warning component (3) includes a first water pressure sensor (31), a second water pressure sensor (32), a flow sensor (33), and a display panel (35); the first water pressure sensor (31) is located on the upper part of the hollow rod (21), the second water pressure sensor (32) is located at the midpoint of the axial direction of the hollow rod (21), and the flow sensor (33) is located on the lower part of the hollow rod (21); the first water pressure sensor (31), the second water pressure sensor (32), and the flow sensor (33) are all installed inside the hollow rod (21) and are wirelessly connected to the display panel (35); the display panel (35) is installed on the exposed end of the hollow rod (21) through a display panel fixing sleeve (34), and has a built-in microcontroller, a data storage module, and a graded early warning module; The drainage assembly includes a drainage interface (4), a water guide pipe (5), and a drainage trough (6); the drainage interface (4) is located at the bottom of the hollow rod body (21) and communicates with the interior of the hollow rod body (21); a solenoid valve (41) is provided inside the drainage interface (4); one end of the water guide pipe (5) is detachably connected to the drainage interface (4), and the other end is connected to the drainage trough (6).

2. The hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability as described in claim 1, characterized in that, The hollow rod (21) has a first filter screen (213) embedded in its inner wall. The magnesium alloy anode block (216) is disposed between the outer surface of the first filter screen (213) and the inner wall of the hollow rod (21). The inner side of the first filter screen (213) is connected to a second filter screen (214) by a buckle (215). The first water pressure sensor (31), the second water pressure sensor (32) and the flow sensor (33) are all embedded in the inner surface of the second filter screen (214).

3. A hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability according to claim 2, characterized in that, The first filter screen (213) is a stainless steel filter screen, which is embedded and fixed to the inner wall of the hollow rod (21) with an interference fit; the second filter screen (214) is a non-woven composite filter screen, and the filter pore size of the second filter screen (214) is smaller than that of the first filter screen (213).

4. A hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability according to claim 1, characterized in that, The lower part of the hollow rod (21) is fitted with a water-sealing expansion sleeve (25), which is positioned above the tray (26).

5. A hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability according to claim 1, characterized in that, The hollow rod (21) has an integrally formed limiting ring (24) on its top outer wall. The hollow rod (21) is fitted with an expansion shell body (22) and a conical expansion head (23). The expansion shell body (22) is located above the limiting ring (24) and its inner diameter is smaller than the outer diameter of the limiting ring (24). The outer surface of the expansion shell body (22) is provided with anti-slip teeth. The conical expansion head (23) is located between the expansion shell body (22) and the hollow rod (21). The inner surface of the conical expansion head is provided with an internal thread that is threaded to the hollow rod (21). The outer surface is provided with an anti-rotation limiting block. The inner surface of the expansion shell body (22) is provided with a limiting groove that cooperates with the anti-rotation limiting block.

6. A method of using a hydrophobic anti-corrosion anchor bolt for early warning of roof rock instability as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Drill a hole at the designed position of the surrounding rock (1) of the top plate, insert the assembled drainage anchor (2) into the hole, rotate the hollow rod (21) clockwise, so that the conical expansion head (23) moves downward along the axial direction of the hollow rod (21), push the expansion shell body (22) to open radially, and clamp the hole wall to achieve anchoring; S2. First, install the water-sealing expansion sleeve (25), then install the tray (26) and nut (27), and finally tighten the nut (27) to fix the tray (26); S3. Connect the drain interface (4) to the water pipe (5), and connect the water pipe (5) to the drain trough (6). The system will automatically enter the initialization mode and complete the hydrostatic pressure measurement and the calibration of the initial reference permeability coefficient K0. S4. Enter normal monitoring mode. The second water pressure sensor (32) and flow sensor (33) collect data in real time and wirelessly transmit it to the display panel (35). The microcontroller calculates the real-time permeability coefficient K and ratio K / K0, and then transmits the information to the graded early warning module for early warning. S5. Take corresponding graded disposal measures according to different levels of damage; S6. Regularly use an extended nylon brush to clean the blockage between the filter screens inside the rod. When cleaning, the drain interface (4) needs to be removed. After cleaning, the drain interface (4) is installed and the S3-S5 operation is repeated.

7. The method of use according to claim 6, characterized in that, In S3, the initialization mode includes the following steps: S31, the microcontroller closes the solenoid valve (41), and the water in the surrounding rock (1) enters the hollow rod body (21) through the guide hole (211); S32, The flow sensor (33) monitors the flow change in the hollow rod (21) in real time. When the flow readings are all 0 for three consecutive times and remain so for more than five minutes, it is determined that the hollow rod (21) is completely filled with water and the water flow is still. S33. At this time, the first water pressure sensor (31) measures the original static water pressure P1 of the surrounding rock (1) and transmits it to the display panel (35). S34. After the measurement is completed, the microcontroller automatically opens the solenoid valve (41), and the system enters the initial reference permeability coefficient measurement mode; S35. Read the measured value Q of the flow sensor (33) and calculate the total head difference Δh. After the flow rate Q and the total head difference Δh stabilize, calculate the real-time permeability coefficient K. When the change rate of the real-time permeability coefficient K value of five consecutive measurements is less than 5%, take the average value of the five measurements as the initial process number K0 and store it.

8. The method of use according to claim 7, characterized in that, The method for calculating the total head difference Δh includes the following steps: S351. Determining the reference plane as the horizontal plane of the roadway floor; S352. Pre-measuring and storing the installation height z1 of the first water pressure sensor (31) and the installation height z2 of the second water pressure sensor (32); S353. Reading the measured value P2 of the second water pressure sensor (32); S354. Respectively calculating the first total water head H1=z1+P1 / (ρg) and the second total water head H2=z2+P2 / (ρg), where ρ is the density of water, and g is the gravitational acceleration; S355. Calculating the total water head difference Δh=H1-H2.

9. The method of use according to claim 8, characterized in that, The calculation formula for the real-time permeability coefficient K value is K=Q•ln(R / r0) / (2πL•Δh), where R is the dewatering influence radius, which is determined through on-site pumping test; r0 is the inner diameter of the anchor rod; L is the axial length of the hollow rod body (21).

10. The method of use according to claim 6, characterized in that, The specific hierarchical early warning in S4 is: when K / K0≤1.5, it is determined as a normal state, and no indicator light is on; when 1.5<K / K0≤3, it is determined as slight damage, and the blue indicator light is on; when 3<K / K0≤5, it is determined as moderate damage, and the yellow indicator light is on; when K / K0>5, it is determined as severe damage, the red indicator light is on and an acousto-optic alarm is triggered.

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