Method for accelerated corrosion test of anchor rod based on surrounding rock dissolution, stress and temperature

Abstract

The application discloses an anchor rod accelerated corrosion test method based on surrounding rock dissolution, stress and temperature, which comprises the following steps: step one, determining the actual temperature value, corrosion ion composition and PH value of seawater, and preparing a corrosion solution; step two, obtaining 12 groups of surrounding rock test blocks in a roadway, putting the test blocks into a vacuum container and adding the corrosion solution, taking out the corroded surrounding rock test blocks, and collecting the dissolution solution; step three, installing an anchor rod on each surrounding rock test block and adjusting the prestress of the anchor rod; step four, placing the surrounding rock test blocks in a liquid storage tank and adding the dissolution solution to the liquid storage tank; step five, after a corrosion period, taking down the anchor rod, and calculating the corrosion rate and corrosion weight loss rate of the anchor rod; step six, performing phase analysis on the corrosion products on the surface of the anchor rod, testing the mechanical properties of the anchor rod and a tray, obtaining the fracture characteristics of the surface of the anchor rod, and analyzing the corrosion mechanism. The application considers the influence of the dissolution of surrounding rock and seawater on the corrosion of the anchor rod, truly simulates the corrosion condition of seawater on the anchor rod under the surrounding rock environment, and accurately judges the actual service life of the anchor rod.

Description

Technical Field

[0001] This invention relates to the field of mining engineering technology, specifically to a method for accelerating the corrosion test of anchor bolts based on the effects of surrounding rock karstification, stress, and temperature. Background Technology

[0002] With the increase in mining depth, mining area, and mining intensity, the instability of roadways intensifies. Deep roadways exhibit dynamic phenomena such as high ground stress, strong mining-induced effects, and large deformation of the surrounding rock, which increase the difficulty of roadway support. Based on roadway geology and production conditions, my country has developed various roadway surrounding rock control technologies, including support methods, reinforcement methods, stress control methods, and combined support methods. Through years of research and practice, a roadway support system has been formed, with bolt and cable support as the main support method, and multiple support methods coexisting. This has solved numerous roadway support problems and supported safe and efficient mine production.

[0003] However, the continuous development of deep mining in coastal areas has brought new challenges—the corrosion failure of anchoring materials. Coastal mines often face corrosion challenges from the seawater environment. Seawater itself, as an corrosive medium, contains a high concentration of corrosive ions that accelerate the corrosion of the anchoring system. Furthermore, in harsh environments, the surrounding rock and seawater also undergo dissolution. When calculating the service life of anchor bolts, previous researchers typically only considered the impact of the corrosive environment on the anchor bolts, neglecting whether the dissolution of the surrounding rock and seawater would further affect the corrosion of the anchor bolts. Ignoring the impact of the dissolution of the surrounding rock and seawater on the mechanical properties of the anchor bolts limits the assessment of their service life and the effectiveness of anti-corrosion treatment.

[0004] In practical engineering, anchor bolts are subjected to a complex environment with multiple factors such as temperature, humidity, and surrounding rock stress for extended periods. Only by comprehensively considering all environmental factors can accurate anchor bolt parameters be obtained. However, on-site corrosion testing of anchor bolts is inconvenient and easily affected by other factors, while traditional indoor accelerated corrosion tests and mechanical performance tests simply consider the reaction between the support system and the corrosive environment. Therefore, it is necessary to design an accelerated corrosion testing method for anchor bolts based on the effects of surrounding rock dissolution, stress, and temperature. This method is crucial for clarifying the impact of the actual environment on the mechanical properties of anchor bolts, accurately assessing their service life, and implementing corresponding anti-corrosion measures based on the effects of dissolution. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, the present invention aims to propose an accelerated corrosion test method for anchor bolts based on the effects of surrounding rock dissolution, stress, and temperature. This method solves the problem that the current approach only considers the impact of the corrosive environment on anchor bolts, neglecting the influence of the dissolution effect of surrounding rock and seawater on the anchor bolt corrosion process, which limits the assessment of anchor bolt service life and the anti-corrosion treatment of anchor bolts.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature includes the following steps:

[0008] Step 1: Take seawater from the vicinity of the coastal mine, measure the corrosive ion composition, pH value, and actual temperature of the seawater, determine the type of corrosive solution, prepare the corrosive solution for later use based on the measurement results, and measure the initial pH value of the corrosive solution.

[0009] Step 2: Select rock walls in the tunnel that have not been eroded by seawater to obtain at least 12 sets of surrounding rock test blocks, each set of surrounding rock test blocks including multiple surrounding rock test blocks.

[0010] All surrounding rock test blocks were placed in a vacuum container and a corrosion solution was added. The vacuum container was then sealed, and the surrounding rock test blocks were subjected to forced saturation by vacuuming. After the corrosion process of the surrounding rock test blocks was completed, the corrosion solution was collected, and the composition of the corrosion solution was analyzed by infrared spectroscopy to determine the corrosion products.

[0011] Step 3: Remove the surrounding rock test blocks from the vacuum container and drill through holes in each surrounding rock test block.

[0012] Select anchor rods of the same specifications and length, weigh each anchor rod and record the weight m0. Then, install all anchor rods onto the corresponding surrounding rock test blocks and adjust the prestress of all anchor rods to the same prestress value.

[0013] Step four: Place each group of surrounding rock test blocks into a storage tank and place a pad at the bottom of each surrounding rock test block. Then, add solvent into the storage tank so that the surrounding rock test blocks and anchor rods are completely immersed in the solvent.

[0014] The etching solution is heated to ensure that its temperature remains consistent with the actual temperature value in step one.

[0015] Record the time when the etching solution is first added and measure the initial pH value of the etching solution.

[0016] Step 5: Take two weeks as a corrosion cycle. After the first corrosion cycle is completed, take out a set of surrounding rock test blocks and remove the anchor rods from the surrounding rock test blocks, and extract the corrosion products on the surface of the anchor rods.

[0017] Afterwards, the anchor bolt surface was derusted by pickling, the corroded anchor bolt was weighed and the weight m1 of the corroded anchor bolt was recorded, and the corrosion rate and corrosion weight loss rate of the anchor bolt were calculated.

[0018] The formula for calculating the corrosion rate is as follows:

[0019]

[0020] Where: m0 is the mass of the anchor rod before corrosion, m1 is the mass of the anchor rod after corrosion, S is the surface area of ​​the anchor rod, and t is the corrosion time;

[0021] The formula for calculating corrosion weight loss rate is as follows:

[0022]

[0023] In the formula: V is the corrosion weight loss rate; Δm is the mass difference of the anchor rod before and after corrosion, and m is the mass before corrosion.

[0024] Step six: Extract the solvent from the storage tank, analyze the chemical composition of the solvent using infrared spectroscopy, and compare it with the chemical composition of the solvent when it was first added to analyze the changes in the solvent.

[0025] XRD was used to analyze the phase composition of corrosion products on the surface of the anchor bolt to determine the type of corrosion products and analyze the corrosion mechanism of the anchor bolt.

[0026] Pull-out tests were conducted on the corroded anchor rods, and compression tests were conducted on the trays to obtain the mechanical property parameters of the corroded anchor rods and trays, respectively.

[0027] Subsequently, the surface fracture surface of the anchor rod was scanned using an electron microscope to obtain the surface fracture characteristics.

[0028] Step 7: After each corrosion cycle, take out another set of surrounding rock test blocks and repeat the operations of Step 5 and Step 6, and so on, until the last set of surrounding rock test blocks.

[0029] Data analysis and corrosion mechanism analysis were conducted to determine the impact of the surrounding rock and seawater environment on the mechanical properties of the anchor bolt.

[0030] Furthermore, in step two, surrounding rock blocks are removed from the selected rock wall by drilling or sawing, and the surrounding rock blocks are processed into surrounding rock test blocks. The surrounding rock test blocks are long strips with square cross sections, and each surrounding rock test block has the same size.

[0031] In step three, the through hole is located at the center of the end face of the surrounding rock test block. The through hole extends along the length of the surrounding rock test block, and its diameter is 1.1 to 1.25 times the diameter of the anchor rod.

[0032] Furthermore, in step two, the corrosion period of the surrounding rock specimen in the vacuum container is 30 days. During this period, the vacuum container is opened every three days to sample the corrosion solution and measure its pH value.

[0033] When the absolute value of the difference between the pH value of the etching solution and its initial pH value is less than 0.5, the pH value of the etching solution is adjusted to the initial pH value by adding HCl or NaOH into the vacuum container, and then the vacuum container is opened and evacuated again.

[0034] Furthermore, in step three, when installing the anchor rod, first insert the anchor rod into the through hole of the surrounding rock test block, and after one end of the anchor rod passes out of the surrounding rock test block, tighten the positioning nut.

[0035] After placing the tray and the seismic pressure gauge at the other end of the anchor rod located outside the surrounding rock test block, tighten the locking nut to apply prestress to the anchor rod, and determine the prestress value of the anchor rod through the seismic pressure gauge.

[0036] Finally, the shock-resistant pressure gauge is sealed in a sealed package.

[0037] Furthermore, based on the pH value of the seawater measured in step one, the corrosive solution is a strong acid solution or a strong alkali solution prepared by adding HCl or NaOH to a salt solution. Each corrosive solution reacts with the surrounding rock, and the resulting dissolution products are different.

[0038] Furthermore, the storage tank is a rectangular shell structure with an open top, and the surrounding rock test block is placed in the center inside the storage tank. The distance between the outer wall of the test block and the inner wall of the storage tank is not less than 1 / 2 of the width of the surrounding rock test block.

[0039] The bottom of the storage tank is equipped with multiple heat-conducting pipes for heating the solvent, and a temperature sensor is installed inside the storage tank.

[0040] The distance between the surface of the corrosive liquid and the upper surface of the surrounding rock test block is not less than 5 cm, and the process of accelerated corrosion of the anchor bolt is carried out in an open environment.

[0041] Furthermore, during the accelerated corrosion process of the anchor bolt, the solution in the storage tank is sampled regularly and the pH value is measured.

[0042] When the absolute value of the difference between the pH value of the etching solution and its initial pH value is less than 0.5, the pH value of the etching solution is adjusted to the initial pH value by adding HCl or NaOH to the storage tank.

[0043] Furthermore, after the anchor bolt is installed on the surrounding rock test block, its prestress value is 30% to 45% of the anchor bolt yield stress.

[0044] During the accelerated corrosion process of the anchor bolt, the value of the anchor bolt prestress should be observed periodically using a shock-resistant pressure gauge. If the prestress is lost, the anchor bolt prestress should be restored to the initial prestress value by tightening the lock nut.

[0045] Furthermore, each group of surrounding rock test blocks includes three surrounding rock test blocks. In step five, the three anchor rods removed from the surrounding rock test blocks are weighed after being corroded by the solvent. The corrosion rate and corrosion weight loss rate of each anchor rod are calculated to obtain the average corrosion rate and average corrosion weight loss rate of the anchor rods in each group of surrounding rock test blocks.

[0046] Furthermore, the corroded anchor bolts were installed on a mechanical performance testing machine to obtain their yield strength and ultimate strength.

[0047] A compression test was conducted on the corroded pallet to measure its compressive strength.

[0048] By adopting the above technical solution, the beneficial technical effects of this invention are as follows: This invention considers the dissolution effect of surrounding rock and seawater, as well as the combined effects of prestress and temperature on anchor bolt corrosion, allowing for more accurate calculation of the impact of the corrosive environment on anchor bolt durability and service life. Corrosion prevention measures can be implemented when used in different roadways. By preparing different corrosive solutions, the effects of different pH levels and ion concentrations on the mechanical properties of anchor bolts can be studied. Simultaneously, multiple groups of anchor bolts are tested, and mechanical property tests are conducted on anchor bolts with different immersion times, significantly shortening the testing time and allowing for the acquisition of the impact of different corrosion times on the mechanical properties of anchor bolts. Attached Figure Description

[0049] Figure 1 This is a three-dimensional schematic diagram of the combined structure of the surrounding rock test block, anchor bolt, and related components of the present invention.

[0050] Figure 2 yes Figure 1 Left view of the combined structure.

[0051] Figure 3 yes Figure 1 The front view of the combined structure.

[0052] Figure 4 This is a diagram illustrating the working state of the accelerated corrosion test method for anchor bolts under the influence of surrounding rock erosion, stress, and temperature, based on the present invention. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the accompanying drawings:

[0054] Implementation examples, in conjunction with Figures 1 to 4 An accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature effects includes the following steps:

[0055] Step one involves collecting environmental characteristics and basic properties of the anchor bolt material within the anchoring area, and then configuring experimental parameters based on these characteristics and properties. The anchor bolts used in the roadway are threaded steel anchor bolts with a yield strength of 300 MPa.

[0056] Seawater samples were collected from the vicinity of the coastal mine. The composition of corrosive ions, pH value, and actual temperature of the seawater were measured. The type of corrosive solution used to accelerate the corrosion of the anchor bolts was determined by measuring the seawater temperature daily over a specific period. The actual temperature was calculated as the average temperature of the seawater within the mine's tunnels. Based on the measured pH value, a suitable corrosive solution was prepared and its initial pH value was determined. Depending on the measured pH value, the corrosive solution was prepared by adding HCl or NaOH to a salt solution, resulting in either a strong acid or a strong alkali solution. It is important to emphasize that each corrosive solution reacts with the surrounding rock, producing different dissolution products. In this embodiment, the corrosive solution was a strong acid solution prepared by adding HCl to a 0.1 mol / L NaCl salt solution, with a pH of 4.

[0057] Step two: Within the tunnel, rock walls that have not been eroded by seawater were selected to obtain 12 sets of surrounding rock test blocks 1. Each set of surrounding rock test blocks 1 consisted of three surrounding rock test blocks 1. The surrounding rock blocks were removed from the selected rock walls using drilling or sawing methods, and processed into surrounding rock test blocks 1. The surrounding rock test blocks 1 were rectangular strips with identical dimensions. Simultaneously, multiple sets of pad blocks 6, equal in number to the surrounding rock test blocks 1, were cut from the selected rock walls. Each set of pad blocks 6 consisted of four pad blocks 6, which were rectangular surrounding rock blocks with dimensions of 3cm*3cm*8cm.

[0058] All surrounding rock specimens 1 were placed in a vacuum container and corrosive liquid was added. Simultaneously, all pads 6 were added to the vacuum container. The container was then sealed, and the surrounding rock specimens 1 were subjected to forced vacuum saturation, allowing the corrosive liquid to penetrate the pores of the specimens and accelerate the corrosion reaction. After the corrosion process was complete, the corrosive liquid was collected, and its composition was analyzed using infrared spectroscopy to determine the corrosion products.

[0059] The corrosion period for the surrounding rock specimen 1 in the vacuum container was 30 days. During this period, the vacuum container was opened every three days to sample the corrosive solution and determine its pH value. After 30 days, the vacuum container was opened, and all surrounding rock specimens 1 and all pad blocks 6 were removed. The leaching solution was collected and stored for later use.

[0060] When the absolute value of the difference between the pH value of the corrosive solution and its initial pH value is less than 0.5, the pH value of the corrosive solution is adjusted to the initial pH value by adding HCl or NaOH to the vacuum container, and then the vacuum container is opened and re-vacuumed. This ensures that the accelerated dissolution effect of the corrosive solution on the surrounding rock specimen 1 is sustainable.

[0061] Step 3: Remove the surrounding rock test block 1 from the vacuum container and drill through holes in each of the surrounding rock test blocks 1. The through holes are located at the center of the end face of the surrounding rock test block 1 and extend along the length of the surrounding rock test block 1. The diameter of the through holes is 1.1 to 1.25 times the diameter of the anchor rod 2, so as to ensure that there is a certain cavity between the anchor rod 2 and the inner wall of the through hole after the anchor rod 2 is inserted into the through hole. The eroding liquid enters the annular cavity between the anchor rod 2 and the inner wall of the through hole, which accelerates the corrosion of the anchor rod 2.

[0062] Anchor bolts 2 of identical specifications and lengths were selected, with the number of anchor bolts 2 equal to and corresponding one-to-one with the number of surrounding rock test blocks 1. The diameter of the anchor bolts was 40 mm, and their length was 750 mm. The weight m0 of each anchor bolt 2 was weighed and recorded. Then, all anchor bolts 2 were installed onto their corresponding surrounding rock test blocks 1, and the prestress of all anchor bolts 2 was adjusted to the same prestress value, which was 30% of their yield stress.

[0063] Specifically, when installing the anchor rod 2, the anchor rod 2 is first inserted into the through hole of the surrounding rock test block 1. After one end of the anchor rod 2 passes through the surrounding rock test block 1, the positioning nut 44 is screwed on. The positioning nut 44 limits the anchor rod 2 and prevents it from detaching from the surrounding rock test block 1 when prestress is applied to the anchor rod 2.

[0064] After placing the tray 3 and the seismic pressure gauge 5 sequentially at the other end of the anchor rod 2 outside the surrounding rock test block 1, tighten the locking nut 4 to apply prestress to the anchor rod 2. Determine the prestress value of the anchor rod 2 using the seismic pressure gauge 5. After the anchor rod 2 is installed into the surrounding rock test block 1, its prestress value is adjusted to 30% of the yield stress of the anchor rod 2.

[0065] Finally, the shock-resistant pressure gauge 5 is sealed in a sealed container. Specifically, the gauge head is sealed in a transparent, corrosion-resistant packaging bag to prevent the corrosive liquid from corroding the gauge and causing damage.

[0066] Step four: Place each group of surrounding rock test blocks 1 into a storage tank 8, and place a set of pads 6 at the bottom of each surrounding rock test block 1. The four pads 6 in the same group are placed at the four corners of the bottom of the surrounding rock test block 1. Then, add the solvent 7 into the storage tank 8, ensuring that the surrounding rock test block 1 and the anchor rod 2 are completely immersed in the solvent, with all six sides of the surrounding rock test block 1 in full contact with the solvent 7. Heat the solvent in the storage tank 8 through the heat pipe 10, ensuring that the temperature of the solvent 7 remains consistent with the actual temperature value in step one. During operation, a temperature sensor installed in the storage tank 8 monitors the temperature change of the solvent in real time, ensuring that the absolute value of the difference between the temperature of the solvent 7 and the actual temperature value does not exceed 2℃, and that the temperature during the accelerated corrosion process of the anchor rod remains consistent with the temperature inside the coastal mine roadway.

[0067] Record the time when the first solvent 7 was added and measure the initial pH value of the solvent.

[0068] The liquid storage tank 8 is a rectangular shell structure with an open top. The surrounding rock test block 1 is placed in the center of the liquid storage tank, and the distance between its outer wall and the inner wall of the liquid storage tank 8 is not less than 1 / 2 of the width of the surrounding rock test block 1. The distance between the liquid surface of the corrosive liquid and the upper surface of the surrounding rock test block 1 is not less than 5cm, and the process of accelerated corrosion of the anchor bolt 2 is carried out in an open environment.

[0069] The bottom of the storage tank 8 is equipped with multiple heat-conducting pipes 10. The heat-conducting pipes are existing electric heating glass tubes. The heat-conducting pipes are used to heat and keep the corrosive liquid 7 in the storage tank 8. The storage tank 8 is equipped with a temperature sensor. The temperature sensor collects the temperature data of the etchant 7 in real time. The working state of the electric heating glass tube is controlled by a PLC controller to keep the etchant at a certain temperature range, which is compatible with the average temperature of the seawater in the tunnel.

[0070] During the accelerated corrosion process of anchor bolt 2, the value of the prestress of anchor bolt 2 is observed periodically by using the shock-resistant pressure gauge 5. If the prestress is lost, the prestress of anchor bolt 2 is restored to the initial prestress value by tightening the locking nut 4.

[0071] During the accelerated corrosion process of anchor bolt 2, the pH value of the etchant in the storage tank is sampled and measured periodically. When the absolute value of the difference between the pH value of the etchant and its initial pH value is less than 0.5, the pH value of the etchant is adjusted to the initial pH value by adding HCl or NaOH to the storage tank, so that the corrosive effect of the etchant on anchor bolt 2 is always kept within a certain sustainable range.

[0072] Step 5: Take two weeks as a corrosion cycle. After the first corrosion cycle is completed, take out a set of surrounding rock test blocks 1 and remove the anchor rods 2 on the surrounding rock test blocks 1, and extract the corrosion products on the surface of the anchor rods 2.

[0073] Subsequently, the three anchor rods 2 removed from the surrounding rock test block 1 were derusted by acid washing. The three anchor rods 2 after derusting were weighed and their weights m1 were recorded. The corrosion rate and corrosion weight loss rate of each anchor rod 2 were calculated. Furthermore, the average corrosion rate and average corrosion weight loss rate of the anchor rods 2 in each group of surrounding rock test blocks 1 were calculated.

[0074] The formula for calculating the corrosion rate is as follows:

[0075]

[0076] In the formula: m0 is the mass of the anchor rod before corrosion, m1 is the mass of the anchor rod after corrosion, S is the surface area of ​​the anchor rod, and t is the corrosion time.

[0077] The formula for calculating corrosion weight loss rate is as follows:

[0078]

[0079] In the formula: V is the corrosion weight loss rate; Δm is the mass difference of the anchor rod before and after corrosion, and m is the mass before corrosion.

[0080] In step five,

[0081] Step six: Extract the solvent from the storage tank, analyze the chemical composition of the solvent using infrared spectroscopy, and compare it with the chemical composition of the solvent when it was first added to analyze the changes in the solvent.

[0082] XRD was used to analyze the phase composition of corrosion products on the surface of anchor bolt 2 to determine the type of corrosion products and analyze the corrosion mechanism of anchor bolt 2.

[0083] The corroded anchor bolt 2 was installed on a mechanical property testing machine, and a pull-out test was performed on it to obtain its yield strength and ultimate strength. A compression test was then performed on the corroded pallet 3 to measure its compressive strength.

[0084] Subsequently, the surface fracture surface of anchor bolt 2 was scanned using an electron microscope to obtain the surface fracture characteristics.

[0085] Step 7: After each corrosion cycle, take out another set of surrounding rock test blocks 1 and repeat the operations of Step 5 and Step 6, and so on, until the last set of surrounding rock test blocks 1.

[0086] After the corrosion test of 12 sets of anchor bolts was completed, the mechanical performance data of the 12 sets of anchor bolts were analyzed using a data analysis system. The curves of anchor bolt corrosion time versus corrosion weight loss were plotted, the corrosion mechanism was analyzed to obtain the anchoring corrosion damage mechanism, and the influence of the surrounding rock and seawater environment on the mechanical performance of anchor bolts was determined.

[0087] This embodiment provides an accelerated corrosion test method for anchor bolts based on the effects of surrounding rock karstification, stress, and temperature. The pH value of the corrosive solution is adjusted according to the environment in which the anchor bolt is located. Simultaneously, the stress on the anchor bolt is made to match the actual stress conditions underground, accurately reproducing the corrosion environment and actual stress conditions of the anchor bolt underground. This allows for the precise determination of the mechanical performance parameters of the anchor bolt under continuous underground corrosion, resulting in accurate and reliable test results. This invention is more consistent with field conditions, enabling more precise acquisition of the mechanical properties of anchor bolts under corrosive operating environments, thus allowing for more accurate calculation of service life. This facilitates the implementation of corresponding anti-corrosion measures for different service roadways.

[0088] For any parts not mentioned in this invention, existing technologies can be used or referenced.

[0089] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0090] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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 limitations on this invention.

[0091] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A test method for accelerated corrosion of anchor bolts based on the effects of surrounding rock karstification, stress, and temperature, characterized in that, Includes the following steps: Step 1: Take seawater from the vicinity of the coastal mine, measure the corrosive ion composition, pH value, and actual temperature value of the seawater, determine the type of corrosive solution, prepare the corrosive solution for later use based on the measurement results, and measure the initial pH value of the corrosive solution. Step 2: Select rock walls in the tunnel that have not been eroded by seawater to obtain at least 12 sets of surrounding rock test blocks, each set of surrounding rock test blocks including multiple surrounding rock test blocks; All surrounding rock test blocks were placed in a vacuum container and a corrosion solution was added. The vacuum container was sealed and the surrounding rock test blocks were evacuated to force saturation. After the corrosion process of the surrounding rock test blocks was completed, the corrosion solution was collected and the composition of the corrosion solution was analyzed by infrared spectroscopy to determine the corrosion products. Step 3: Remove the surrounding rock test blocks from the vacuum container and drill through holes in each surrounding rock test block. Select anchor rods of the same specifications and length, weigh each anchor rod and record the weight m0. Then, install all anchor rods onto the corresponding surrounding rock test blocks and adjust the prestress of all anchor rods to the same prestress value. Step 4: Place each group of surrounding rock test blocks into a liquid storage tank and place a pad at the bottom of each surrounding rock test block. Then, add solvent into the liquid storage tank so that the surrounding rock test blocks and anchor rods are completely immersed in the solvent. The etching solution is heated to ensure that its temperature remains consistent with the actual temperature value in step one. Record the time of the first addition of the etching solution and measure the initial pH value of the etching solution; Step 5: Take two weeks as a corrosion cycle. After the first corrosion cycle is completed, take out a set of surrounding rock test blocks and remove the anchor rods from the surrounding rock test blocks, and extract the corrosion products on the surface of the anchor rods. Afterwards, the anchor bolt surface was derusted by pickling, the corroded anchor bolt was weighed and the weight m1 of the corroded anchor bolt was recorded, and the corrosion rate and corrosion weight loss rate of the anchor bolt were calculated. The formula for calculating the corrosion rate is as follows: ； Where: m0 is the mass of the anchor rod before corrosion, m1 is the mass of the anchor rod after corrosion, S is the surface area of ​​the anchor rod, and t is the corrosion time; The formula for calculating corrosion weight loss rate is as follows: ； In the formula: V is the corrosion weight loss rate; denoted as the mass difference of the anchor bolt before and after corrosion, where m is the mass before corrosion. Step 6: Extract the solvent from the storage tank, analyze the chemical composition of the solvent using infrared spectroscopy, and compare it with the chemical composition of the solvent when it was first added to analyze the changes in the composition of the solvent. XRD was used to analyze the phase composition of corrosion products on the surface of the anchor bolt to determine the type of corrosion products and analyze the corrosion mechanism of the anchor bolt. Pull-out tests were conducted on the corroded anchor rods, and compression tests were conducted on the trays to obtain the mechanical property parameters of the corroded anchor rods and trays, respectively. Subsequently, the surface fracture surface of the anchor bolt was scanned using an electron microscope to obtain the surface fracture characteristics; Step 7: After each corrosion cycle, take out another set of surrounding rock test blocks and repeat the operations of Step 5 and Step 6, and so on, until the last set of surrounding rock test blocks; perform data analysis and corrosion mechanism analysis to determine the impact of the surrounding rock seawater environment on the mechanical properties of the anchor bolt. In step two, the corrosion period of the surrounding rock specimen in the vacuum container is 30 days. During this period, the vacuum container is opened every three days to take samples of the corrosion solution and measure the pH value of the corrosion solution. When the absolute value of the difference between the pH value of the etching solution and its initial pH value is less than 0.5, the pH value of the etching solution is adjusted to the initial pH value by adding HCl or NaOH into the vacuum container, and then the vacuum container is opened and evacuated again. In step three, the through hole is located at the center of the end face of the surrounding rock test block, and the through hole extends along the length of the surrounding rock test block, with a diameter of 1.1 to 1.25 times the diameter of the anchor rod; In step three, when installing the anchor rod, first insert the anchor rod into the through hole of the surrounding rock test block, and after one end of the anchor rod passes out of the surrounding rock test block, tighten the positioning nut. After placing the tray and the seismic pressure gauge at the other end of the anchor rod located outside the surrounding rock test block, tighten the locking nut to apply prestress to the anchor rod, and determine the prestress value of the anchor rod through the seismic pressure gauge. Finally, the shock-resistant pressure gauge is sealed in a sealed package. The storage tank is a rectangular shell structure with an open top. The surrounding rock test block is placed in the center of the storage tank, and the distance between its outer wall and the inner wall of the storage tank is not less than 1 / 2 of the width of the surrounding rock test block. The bottom of the storage tank is equipped with multiple heat-conducting pipes for heating the solvent, and a temperature sensor is installed inside the storage tank. The distance between the surface of the corrosive liquid and the upper surface of the surrounding rock test block is not less than 5 cm, and the process of accelerated corrosion of the anchor bolt is carried out in an open environment.

2. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 1, is characterized in that... In step two, surrounding rock blocks are removed from the selected rock wall by drilling or sawing. The surrounding rock blocks are then processed into surrounding rock test blocks, which are long strips with square cross sections and all surrounding rock test blocks have the same size.

3. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 1, is characterized in that... Based on the pH value of the seawater measured in step one, the corrosive solution is a strong acid solution or a strong alkali solution prepared by adding HCl or NaOH to a salt solution. Each corrosive solution reacts with the surrounding rock, and the resulting dissolution products are different.

4. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 3, is characterized in that... During the accelerated corrosion process of anchor bolts, samples of the leaching solution in the storage tank should be taken regularly and the pH value measured. When the absolute value of the difference between the pH value of the etching solution and its initial pH value is less than 0.5, the pH value of the etching solution is adjusted to the initial pH value by adding HCl or NaOH to the storage tank.

5. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 1, characterized in that, After the anchor bolt is installed into the surrounding rock test block, its prestress value is 30% to 45% of the anchor bolt's yield stress; During the accelerated corrosion process of the anchor bolt, the value of the anchor bolt prestress should be observed periodically using a shock-resistant pressure gauge. If the prestress is lost, the anchor bolt prestress should be restored to the initial prestress value by tightening the lock nut.

6. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 1, characterized in that, Each group of surrounding rock test blocks includes three surrounding rock test blocks. In step five, the three anchor rods removed from the same group of surrounding rock test blocks are weighed after being corroded by the solvent. The corrosion rate and corrosion weight loss rate of each anchor rod are calculated, and the average corrosion rate and average corrosion weight loss rate of the anchor rods in each group of surrounding rock test blocks are further obtained.

7. The accelerated corrosion test method for anchor bolts based on surrounding rock karstification, stress, and temperature as described in claim 1, characterized in that, The corroded anchor rods were installed on a mechanical performance testing machine to obtain the yield strength and ultimate strength of the corroded anchor rods. A compression test was conducted on the corroded pallet to measure its compressive strength.

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