A monitoring system and method for sulphate attack of railway subgrades based on diffusion osmosis

Abstract

The application discloses a monitoring system and method for sulfate erosion disease of a railway roadbed based on diffusion dialysis. 2+ The detection box comprises a box body and a box cover, and an impurity filtering layer and a diffusion dialysis membrane are arranged in the detection box. The inside of the detection box is divided into three cavities from left to right, namely, a sewage bin, a clean water bin and a detection bin. The impurity filtering layer is used for filtering solid impurities, and the diffusion dialysis membrane is used for selectively passing sulfate ions. The detection bin is used for containing Ba 2+ Solutions, and a conductivity detection device is further arranged in the detection bin and used for detecting the conductivity of the solution in the detection bin. The sewage bin is used for containing water samples to be detected, and the water samples enter the clean water bin after being filtered through the impurity filtering layer.

Description

Technical Field

[0001] This invention relates to the field of railway subgrade engineering technology, specifically to a monitoring system and method for sulfate erosion diseases of railway subgrade based on diffusion dialysis. Background Technology

[0002] Railway subgrade transition sections are areas requiring special treatment where the subgrade connects to structures, such as the transition zone between embankments and bridge abutments, embankments and transverse structures, embankments and cuttings, and cuttings and tunnels. Setting up transition sections allows for a gradual change in track stiffness and minimizes differential settlement, thereby reducing train and track vibration, mitigating subgrade deformation, and ensuring safe, smooth, and comfortable train operation. Railway subgrade transition sections are typically constructed using cement-graded crushed stone, prepared by dry mixing and adding water to cement and graded crushed stone that meet specifications. They primarily serve to transition stiffness between different sections (bridges, tunnels, and tracks), playing a crucial role in ensuring smooth train operation.

[0003] In recent years, the problem of arching deformation of high-speed railway subgrade has become very prominent, especially the problem of arching due to sulfate erosion in the transition section of the subgrade. The sulfate erosion problem of cement-graded crushed stone can be divided into two categories according to the source of sulfate: endogenous sulfate erosion and exogenous sulfate erosion. (1) Endogenous sulfate erosion mainly refers to the use of cement or graded crushed stone with excessive sulfate content when preparing cement-graded crushed stone, thereby directly introducing a large amount of sulfate into the interior of cement-graded crushed stone material. The sulfate reacts further with the cement and its hydration reaction products in the cement-graded crushed stone to generate expansive products, mainly ettringite, a colorless to yellow calcium aluminum sulfate mineral with the chemical formula 3CaO·Al2O33CaSO4·32H2O. The amount of crystal water is related to the environment, causing volume expansion, which eventually leads to the arching of the subgrade. (2) Exogenous sulfate erosion mainly refers to the presence of a large amount of sulfate in the environment (water, soil) of the roadbed transition section. Through the medium of water, it comes into contact with cement-graded crushed stone and reacts with the cement and its hydration reaction products in the cement-graded crushed stone to generate an expansive substance, mainly ettringite, which causes volume expansion and ultimately leads to the arching of the roadbed.

[0004] Sulfate erosion-induced arching is characterized by its hidden location, slow development, and irreversible reaction, making it a persistent and difficult-to-treat problem for railway subgrade durability. High-speed railways have very strict requirements on the amount of arching deformation in the subgrade, making it difficult to detect with the naked eye. Typically, a track vehicle traveling on the tracks detects deformation on the track surface, and after considering various factors, it is determined that the problem is caused by an internal reaction in the subgrade. Further on-site drilling and sampling are then conducted in a laboratory to verify that the sulfate content exceeds the standard, ultimately confirming that the arching is caused by sulfate erosion.

[0005] Currently, the only testing method for sulfate erosion involves first observing the arching deformation on-site, then drilling holes to collect samples for laboratory testing to verify whether the sulfate content exceeds the standard, ultimately determining whether sulfate erosion is the cause of the roadbed arching. Clearly, this method can only be implemented after significant arching deformation is observed, meaning it's only possible to determine if sulfate erosion has occurred. When the chemical reaction of sulfate erosion has already occurred within the roadbed, but before the expansion products have accumulated sufficiently to produce significant macroscopic deformation, early warning is impossible. However, once obvious and detectable arching deformation occurs, the damage is already extremely severe, potentially necessitating difficult decisions such as reducing high-speed rail speeds or halting operations, seriously threatening the safe and stable operation of high-speed rail. Furthermore, this method is time-consuming, inefficient, and highly susceptible to human intervention. Therefore, there is an urgent need to develop a measurement method that can promptly detect and alert to potential damage in the early stages of the reaction, especially when reaction conditions are met but before or just beginning to react; a method that is simple to operate, less affected by human intervention, low in cost, and does not disrupt railway operations. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a monitoring system and method for sulfate erosion damage to railway subgrade based on diffusion dialysis.

[0007] To achieve its objective, the present invention employs the following technical solution:

[0008] The first aspect of the present invention provides a monitoring system for sulfate erosion disease of railway subgrade based on diffusion dialysis, including a detection box, the detection box including a box body and a box cover, the detection box is provided with an impurity filter layer and a diffusion dialysis membrane, and the detection box is divided into three chambers from left to right: sewage chamber, clean water chamber and detection chamber;

[0009] The impurity filter layer is used to filter solid impurities; the diffusion dialysis membrane is used to selectively allow sulfate ions to pass through; the detection chamber is used to hold Ba. 2+ The solution detection chamber is also equipped with a conductivity detection device to detect the conductivity of the solution in the detection chamber; the wastewater chamber is used to hold the water sample to be tested, and the water sample enters the clear water chamber after being filtered through the impurity filter layer.

[0010] Preferably, the impurity filtration layer is composed of multiple layers of filter mesh or a filter membrane.

[0011] Preferably, the top of the sewage tank is provided with an overflow outlet for overflowing excess water; the bottom of the sewage tank is provided with a drain outlet for discharging solid impurities.

[0012] Preferably, the conductivity detection device is a conductivity sensor or a conductivity probe of a conductivity meter, and the conductivity probe is connected to an external conductivity meter; the Ba 2+ The solution was selected from BaCl2 solution.

[0013] Preferably, the monitoring system further includes a water guide pipe, the top of which is open, and the cross-section of which is U-shaped or V-shaped;

[0014] The top of the sewage tank is equipped with a water inlet, and a water pipe is connected to the water inlet of the sewage tank to guide the water collected in the water pipe from the roadbed into the sewage tank.

[0015] Preferably, the monitoring system further includes an alarm device, a wireless communication module, and a controller. The conductivity detection device is a conductivity sensor. The controller is used to obtain the detection result of the conductivity sensor. The wireless communication module is used to send the detection result obtained by the controller to a host computer. The signal output terminal of the conductivity sensor is connected to the signal input terminal of the controller, and a signal output terminal of the controller is connected to the alarm device.

[0016] Preferably, the alarm device is a sound alarm or a warning light, which emits an alarm signal when the conductivity is lower than a preset threshold; the host computer is a mobile phone, tablet or computer.

[0017] A second aspect of the present invention provides a real-time monitoring method for sulfate erosion damage to railway subgrade, using the aforementioned monitoring system, comprising the following steps:

[0018] S1. Laying the monitoring system: Drilling holes from the bottom of the side of the railway subgrade into the subgrade, and placing the monitoring system into the drilled holes;

[0019] Water diversion channels are drilled at an angle downwards on the side of the roadbed, and water pipes are placed into the water diversion channels. The end of the water pipe is connected to the inlet of the sewage tank of the monitoring system, and the water collected in the water pipe is introduced into the sewage tank.

[0020] S2. Real-time monitoring: Monitors the conductivity data in the detection chamber. When the conductivity value approaches or reaches the set threshold, it indicates that SO4 has been detected in the water sample. 2- Ions indicate that sulfate erosion is occurring or will occur in the roadbed.

[0021] Preferably, in step S1, multiple water diversion channels are drilled from top to bottom on the side of the roadbed. The multiple water diversion channels are arranged in a straight line. A water guide pipe is placed in each water diversion channel. The lower water guide pipe is longer than the upper water guide pipe and is used to collect water that seeps from top to bottom. The end of the lowermost water guide pipe is connected to the inlet of the sewage tank to introduce the collected water sample into the sewage tank.

[0022] Preferably, the monitoring system is periodically removed from the roadbed ducts, and the Ba in the detection chamber is replaced. 2+ The solution was used to clean impurities from the sewage tank.

[0023] The beneficial effects of this invention are:

[0024] 1. Accuracy: Through testing and calculation, it can be determined whether the roadbed transition section has suffered sulfate erosion, and the amount of sulfate (SO4) in the railway roadbed can be calculated. 2- The content of ) and its degree of erosion on roadbed materials.

[0025] 2. Preventative: Regular inspections of railway subgrades can detect sulfate corrosion problems before they become severe and allow for timely preventative measures, thereby extending the service life of the railway.

[0026] 3. Economic Efficiency: Compared to the railway damage and repair costs caused by sulfate corrosion, this method offers significant economic benefits. Placing the system of this invention in the roadbed allows for real-time monitoring of sulfate corrosion on the railway subgrade. Compared to periodic sampling and sending samples to a laboratory for testing, on-site real-time monitoring greatly reduces labor and time costs.

[0027] 4. Safety: Sulfate corrosion can lead to instability in railway subgrade, thereby affecting the safe operation of trains. Timely detection can effectively reduce this risk, ensuring the safety of railway transportation, and the implementation of this method is harmless to the railway subgrade.

[0028] 5. Wide applicability: This method is applicable not only to the subgrade assessment of newly built railways, but also to the subgrade inspection and maintenance of existing railways. Attached Figure Description

[0029] Figure 1 This is the assembly diagram of the verification experimental apparatus in Example 1.

[0030] Figure 2 This is an observation diagram of the ion transmission through the diffusion dialysis membrane in experimental group-1.

[0031] Figure 3 This is a diagram showing the experimental results of ion transmission through the diffusion dialysis membrane in experimental group-2.

[0032] Figure 4 This is a schematic diagram of the monitoring system for sulfate erosion of railway subgrade according to one embodiment of the present invention.

[0033] Figure 5 yes Figure 4 A schematic diagram of the central water pipe.

[0034] Figure 6This is a schematic diagram of the on-site installation and monitoring of the railway subgrade sulfate erosion monitoring system of the present invention in the subgrade.

[0035] Figure 7 This is a schematic diagram of the control flow of the monitoring system for sulfate erosion of railway subgrade according to a certain embodiment of the present invention.

[0036] Figure 4-7 In the accompanying drawings, the elements or structures indicated by the reference numerals are:

[0037] 1. Detection box; 2. Impurity filter layer; 3. Diffusion dialysis membrane; 4. Wastewater tank; 5. Clean water tank; 6. Detection tank; 7. Conductivity detection device; 8. Water pipe; 9. Alarm device; 10. Wireless communication module; 11. Controller. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0040] The diffusion dialysis anion / cation membrane is the core of diffusion dialysis, often simply referred to as anion / cation membrane. An anion / cation membrane is a polymer membrane containing ionic groups that selectively allows ions in solution to pass through. Its structure consists of three parts: a polymer backbone, stationary groups, and mobile ions. Based on the type of charge, they are mainly divided into anion membranes and cation membranes. Anion membranes have positively charged stationary groups in their polymer backbone, allowing selective passage of anions while blocking cations; cation membranes have negatively charged stationary groups in their polymer backbone, allowing selective passage of cations while blocking anions. Currently, various acid recovery diffusion dialysis membranes are available on the market, capable of separating different acids, such as hydrochloric acid and sulfuric acid. Different products are selected depending on the target acid being separated. This invention applies a sulfuric acid diffusion dialysis anion membrane to the sulfate ion detection process of this invention.

[0041] Main materials and reagent sources:

[0042] Filter membrane: Commercially available, filters solid impurities, allows water to pass through, and is resistant to water immersion.

[0043] Sulfuric acid diffusion dialysis membrane (anion membrane): purchased from Shandong Tianwei Membrane Technology Co., Ltd., model DDA3.

[0044] Barium chloride: BaCl2, commercially available.

[0045] Example 1

[0046] I. Experimental Methods

[0047] In this embodiment, a preliminary experiment was conducted in the laboratory to verify the feasibility of the detection principle and to verify whether different ions can diffuse through the sulfuric acid dialysis membrane.

[0048] Experimental setup: A laboratory-type H-chamber electrolytic cell (sealed type) was used.

[0049] Four experimental groups were set up: Experimental Group-1, Experimental Group-2, Control Group-1, and Control Group-2. For each group, an H-type dual-chamber electrolytic cell was used. The side nozzles of the left and right chamber electrolytic cell bottles were connected. A sulfuric acid diffusion dialysis membrane (hereinafter referred to as the diffusion dialysis membrane) was installed at the connection point and fixed with stainless steel clamps (e.g., ...). Figure 1 As shown, different solutions were poured into the left and right chambers respectively. The conductivity of the solutions in the electrolytic cells of the left and right chambers was measured by a conductivity meter at 0 days, 7 days and 30 days respectively. The changes in conductivity in the two chambers were used to verify whether the ions in the left and right chambers could pass through the intermediate diffusion dialysis membrane.

[0050] 1. Experimental Group-1

[0051] Experimental setup: The solution in the left chamber was prepared by adding 0.6 g of anhydrous sodium sulfate to 230 g of 0.0001 mol / L NaOH solution and stirring until homogeneous. The solution in the right chamber was 230 g of 0.1 mol / L BaCl2 aqueous solution. A diffusion dialysis membrane was placed between the side nozzles of the two chambers.

[0052] Objective: To verify whether sulfate ions present in the alkaline solution in the left chamber can enter the right chamber through a diffusion dialysis membrane and react with BaCl2 therein to undergo a precipitation reaction, leading to a decrease in the conductivity of the solution in the right chamber.

[0053] 2. Experimental Group-2

[0054] Experimental setup: The left chamber contains a solution prepared with 230g of purified water and 0.6g of anhydrous sodium sulfate, and the right chamber contains 230g of 0.1mol / L BaCl2 aqueous solution. A diffusion dialysis membrane is placed between the side nozzles of the two chambers.

[0055] Objective: To verify whether sulfate ions present in the neutral solution in the left chamber can enter the right chamber through a diffusion dialysis membrane and react with BaCl2 therein to undergo a precipitation reaction, leading to a decrease in the conductivity of the solution in the right chamber.

[0056] 3. Control group -1

[0057] Experimental setup: The left chamber contains a solution prepared with 150g of purified water and 0.6g of anhydrous sodium sulfate, the right chamber contains 150g of purified water, and a diffusion dialysis membrane is placed between the side nozzles of the two chambers.

[0058] Objective: To verify whether sodium sulfate in the left ventricle can pass through a diffusion dialysis membrane.

[0059] 4. Control group -2

[0060] Experimental setup: 158g of pure water in the left chamber, 158g of 0.1mol / L BaCl2 aqueous solution in the right chamber, and a diffusion dialysis membrane between the side nozzles of the two chambers.

[0061] Objective: To verify whether barium chloride in the right chamber can pass through the diffusion dialysis membrane.

[0062] II. Experimental Results

[0063] The experimental results of the four groups are shown in Tables 1-4.

[0064] 1. Experimental Group-1

[0065] The results are shown in Table 1. The conductivity of the solutions in the left and right chambers decreased to varying degrees, indicating that sulfate ions in the left chamber passed through the diffusion dialysis membrane into the right chamber and underwent a precipitation reaction with BaCl2 in the right chamber. Figure 2 This leads to a decrease in the conductivity of the solution in the right chamber.

[0066] Table 1. Conductivity test results of Experimental Group-1

[0067]

[0068] 2. Experimental Group-2

[0069] The results are shown in Table 2. The conductivity of the solutions in the left and right chambers decreased to varying degrees, indicating that sulfate ions in the left chamber passed through the diffusion dialysis membrane into the right chamber and underwent a precipitation reaction with BaCl2 in the right chamber (e.g., ...). Figure 3 This leads to a decrease in the conductivity of the solution in the right chamber.

[0070] Table 2. Conductivity test results of Experimental Group-2

[0071]

[0072] 3. Control group -1

[0073] The results are shown in Table 3. After a period of time, due to the concentration difference of sulfate ions in the left and right chambers, sulfate ions passed from the left chamber to the right chamber through the diffusion dialysis membrane, causing a change in conductivity. This indicates that using this type of diffusion dialysis membrane allows sulfate ions to pass selectively.

[0074] Table 3. Conductivity test results of control group-1

[0075]

[0076]

[0077] 4. Control group -2

[0078] The results are shown in Table 4. After 30 days, the conductivity of the solution in the left and right chambers did not change significantly, indicating that although there was a concentration difference of BaCl2 in the two chambers, BaCl2 could not pass through the diffusion dialysis membrane.

[0079] Table 4. Conductivity test results of control group-2

[0080]

[0081] The above results show that:

[0082] When the left chamber contained sodium sulfate solution and the right chamber contained pure water (control group-1), sulfate ions entered the right chamber through the diffusion dialysis membrane, causing a significant increase in the conductivity of the solution in the right chamber, while the conductivity of the solution in the left chamber decreased. When the left chamber contained pure water and the right chamber contained BaCl2 solution (control group-2), since BaCl2 cannot pass through the diffusion dialysis membrane (water molecules also cannot pass through the diffusion dialysis membrane), the conductivity of the solutions in the left and right chambers remained almost unchanged even after 30 days of experimentation.

[0083] In railway subgrade engineering, a large amount of cement-based materials are used, such as concrete and mortar, including cement-graded crushed stone, which are all alkaline. In addition, water in nature is generally neutral or slightly alkaline. Therefore, sodium sulfate in experimental group-1 was prepared with NaOH solution, and sodium sulfate in experimental group-2 was prepared with pure water. These two sets of experiments can simulate the main conditions in railway subgrade engineering and in nature.

[0084] The above four sets of experiments demonstrate that the decrease in conductivity of the solutions in the left and right chambers of experimental groups-1 and-2 is due to the reaction of sulfate ions from the left chamber into the right chamber and their reaction with BaCl2, rather than the decrease in conductivity of the right chamber solution caused by BaCl2 entering the left chamber. The diffusion dialysis membrane can prevent BaCl2 from moving from the high-concentration right chamber to the low-concentration left chamber, thus maintaining a higher concentration in the right chamber. This allows BaCl2 to precipitate and react with sulfate ions that might enter the right chamber from the left, leading to a decrease in the conductivity of the right chamber solution. This invention utilizes BaCl2… 2+ Solution and SO4 2- Using ionic reactions to determine whether sulfate erosion has occurred in railway subgrade by observing changes in solution conductivity is feasible, and the monitoring method is accurate and reliable.

[0085] Example 2: A monitoring system for sulfate erosion disease in railway subgrade based on diffusion dialysis

[0086] like Figure 4The monitoring system for sulfate erosion of railway subgrade based on diffusion dialysis of the present invention mainly consists of a detection box 1, which includes a box body and a box cover. The detection box 1 is internally equipped with an impurity filter layer 2 and a diffusion dialysis membrane 3, dividing the interior of the detection box 1 into three chambers from left to right: a wastewater chamber 4, a clean water chamber 5, and a detection chamber 6. The impurity filter layer 2 is used to filter solid impurities, and the diffusion dialysis membrane 3 is used to selectively allow sulfate ions to pass through. The detection chamber 6 is used to hold Ba... 2+ The test chamber 6 is also equipped with a conductivity detection device 7 to detect the conductivity of the solution in the test chamber 6; the wastewater chamber 4 is used to hold the water sample to be tested. After the water sample is filtered through the impurity filter layer 2, it enters the clear water chamber 5. The sulfate ions in the water in the clear water chamber 5 pass through the diffusion dialysis membrane 3 and enter the test chamber 6, causing the conductivity of the solution in the test chamber 6 to decrease. Based on this, the monitoring personnel determine that the water sample contains sulfate ions.

[0087] In some embodiments, the impurity filter layer 2 is composed of multiple layers of filter mesh or a filter membrane; preferably, the multiple layers of filter mesh consist of three layers, with the first layer having a pore size of 1 mm, the second layer having a pore size of 0.5 mm, and the third layer having a pore size of 0.1 mm. Using multiple layers of filter mesh for sequential filtration can prevent large solid impurities from getting stuck in the pores of the small-pore filter mesh and causing blockage. Alternatively, the impurity filter layer 2 can be a commercially available water-resistant filter membrane that can filter solid impurities while allowing water to pass through.

[0088] In some implementations, such as Figure 5 As shown, the monitoring system for sulfate erosion of railway subgrade also includes a water pipe 8, which has an open top and a U-shaped or V-shaped cross-section. The top of the sewage tank 4 is equipped with an inlet, and the water pipe 8 is connected to the inlet of the sewage tank 4 to divert the water collected in the water pipe 8 from the subgrade into the sewage tank 4.

[0089] In some embodiments, the top of the sewage tank 4 is also provided with an overflow outlet for overflowing excess water.

[0090] In some embodiments, a drain outlet is provided at the bottom of the sewage tank 4 to discharge solid impurities, and the solid impurities in the sewage tank 4 can be cleaned periodically.

[0091] In some embodiments, the conductivity detection device 7 is a conductivity sensor or a conductivity probe of a conductivity meter, and the conductivity probe is connected to an external conductivity meter.

[0092] In some implementations, such as Figure 7As shown, the monitoring system for sulfate erosion of railway subgrade also includes an alarm device 9, a wireless communication module 10, and a controller 11. The conductivity detection device 7 is a conductivity sensor. The controller 11 is used to obtain the detection results from the conductivity sensor, and the wireless communication module 10 is used to send the detection results obtained by the controller 11 to a host computer. The signal output terminal of the conductivity sensor is connected to the signal input terminal of the controller 11, and one signal output terminal of the controller 11 is connected to the alarm device 9. The alarm device 9 can be an audible alarm or a warning light, which issues an alarm signal when the conductivity is lower than a preset threshold. The wireless communication module 10 can upload the detection results to the host computer via GPRS or LPWAN IoT protocol for manual viewing. The host computer can be a mobile phone, tablet, or computer. The wireless communication module 10 can be a ZigBee wireless communication module or a Wi-Fi wireless communication module. The conductivity sensor detects the conductivity of the solution in the detection chamber 6, and then the controller 11 and the wireless communication module 10 transmit the detection results to the host computer, where monitoring personnel can read the conductivity value.

[0093] The working principle of the monitoring system for sulfate erosion of railway subgrade in this invention is as follows:

[0094] The core principle is based on the passive diffusion principle driven by a concentration gradient, utilizing diffusion dialysis membranes. When two solutions of different concentrations are separated by a semi-permeable membrane (which only allows certain substances to pass through, such as SO42-),... 2- When separated by ions, the solute will spontaneously diffuse from the high concentration side to the low concentration side until the concentration reaches equilibrium. The detection chamber contains Ba at a known concentration. 2+ The solution contains a conductivity detection device to measure the conductivity of the solution. When SO4 2- Before the ions enter the detection chamber, the conductivity of the conductivity meter tends to a stable value. When SO4... 2- After the ions enter the detection chamber, Ba 2+ The solution will react with SO4 2- When ions react to form a precipitate, the conductivity will initially increase and then decrease. The increase is due to SO42-. 2- The entry of ions into this system causes an increase in the amount of conductive substances, while the decrease is due to SO4. 2- Ions and Ba 2+ A precipitation reaction occurs, reducing the amount of conductive substances. The conductivity data of the solution in the detection chamber is uploaded to the cloud, and personnel can observe the data changes via a host computer. When the data reaches a critical value, it indicates the accumulation of SO4 within the railway subgrade. 2- A high ion concentration indicates that sulfate attack is occurring or will occur in the future, requiring timely measures or methods. Ba 2+ With SO4 2- The reaction equation is shown below:

[0095]

[0096] Ba in the detection chamber 2+ Ba in solution 2+ The SO4 content in environmental water can be calculated using conductivity. 2- The content is used to assess the risk of sulfate corrosion to the project.

[0097] In practical applications, water samples taken from roadbed sections without sulfate erosion show almost no detectable sulfate ions, while water samples taken from roadbeds at risk of or already experiencing sulfate erosion contain sulfate ions. As long as the BaCl2 storage tank of the detection system has sufficient BaCl2 content, it is possible to detect whether sulfate ions have entered and caused a significant change in the solution's conductivity. It is worth noting that because the equipment contains SO4... 2- Ba, as an ion indicator 2+ Limited filling capacity, supplementing Ba for field-deployed devices 2+ The difficulty is considerable, therefore the device needs to be removed and Ba re-injected into the detection chamber after a period of service. 2+ Solution.

[0098] Application Example 1: The monitoring system for sulfate erosion of railway subgrade according to the present invention is used for detection.

[0099] The monitoring system of Example 2 was constructed.

[0100] Preparation of simulated solution for water samples from railway subgrade affected by sulfate erosion: Add 0.6g of anhydrous sodium sulfate to 230g of 0.0001mol / L NaOH solution and stir until homogeneous to obtain the simulated solution. The concentration of sodium sulfate in the simulated solution is within the range of sulfate concentration in the water samples from railway subgrade affected by sulfate erosion.

[0101] 230g of 0.1mol / L BaCl2 aqueous solution was injected into the detection chamber of the monitoring system. 230g of the prepared simulation solution was injected into the wastewater chamber of the monitoring system. After the water from the wastewater chamber flowed into the clear water chamber, the conductivity of the solutions in both the clear water and detection chambers was measured. Subsequently, the conductivity of the solutions in both chambers was measured at 7 and 30 days. The test results are shown in Table 5.

[0102] Table 5. Conductivity test results of the simulated liquid

[0103]

[0104] Sulfate ions in the wastewater tank enter the detection chamber and react with Ba in the wastewater. 2+ The reaction causes a decrease in the conductivity of the solution in the detection chamber; the conductivity of the solution in the clear water chamber also decreases as sulfate ions move into the detection chamber.

[0105] In practical applications, water samples are taken by drilling holes at railway subgrade locations where sulfate erosion is observed. The holes are drilled from the side of the subgrade inwards, and a water pipe is inserted to guide the flow. The water sample is collected in a glass bottle at the end of the pipe. Alternatively, water samples can be taken directly from the subgrade's drainage ditches, which can also reflect the extent of sulfate erosion. The collected water samples are sent to a laboratory and tested using the monitoring system of this invention. If the water sample contains sulfate ions, the conductivity of the solution in the detection chamber will show a significant decrease.

[0106] Example 3: A method for real-time monitoring of sulfate erosion damage in railway subgrade

[0107] The railway subgrade sulfate erosion monitoring system of the present invention, as described in Example 2, is used for detection. Real-time monitoring is conducted on railway subgrade sections suspected of or predicted to be subject to sulfate erosion. The monitoring system of the present invention can be manufactured as a small or miniature device and placed inside the subgrade. The operation is performed according to the following steps (see the schematic diagram of the on-site monitoring). Figure 6 As shown):

[0108] S1. Laying the monitoring system: Drill holes horizontally from the bottom of the side of the railway subgrade into the subgrade, drilling to about the middle of the subgrade, and then place the monitoring system of the present invention into the drilled holes;

[0109] Water inlet channels are drilled at an angle downwards on the side of the roadbed to insert water pipes. The end of the water pipes is connected to the inlet of the sewage tank of the monitoring system, so that the water collected in the water pipes is introduced into the sewage tank.

[0110] To improve the accuracy of reflecting sulfate erosion inside the roadbed, multiple water diversion channels are drilled from top to bottom on the side of the roadbed, arranged in a straight line. A water guide pipe is placed in each water diversion channel, with the lower water guide pipe being longer than the upper one, to collect water seeping downwards from above. The water collected from the upper, middle, and lower parts of the roadbed converges in the lowermost water guide pipe, and the end of the lowermost water guide pipe is connected to the inlet of the sewage tank, introducing the collected water sample into the sewage tank.

[0111] S2. Real-time monitoring: Monitors the conductivity data in the detection chamber. When the conductivity value approaches or reaches the set threshold, it indicates that SO4 has been detected in the water sample. 2- The presence of ions indicates that sulfate erosion is occurring or will occur in the roadbed, suggesting that staff should promptly address the damage to the corresponding roadbed sections.

Claims

1. A monitoring system for sulfate erosion damage in railway subgrade based on diffusion dialysis, characterized in that: The test chamber includes a body and a lid. Inside the test chamber, there is an impurity filtration layer and a diffusion dialysis membrane, which divide the interior of the test chamber into three chambers from left to right: a wastewater chamber, a clean water chamber, and a test chamber. The impurity filter layer is used to filter solid impurities, and the diffusion dialysis membrane is used to selectively allow sulfate ions to pass through. The testing chamber is used to hold Ba. 2+ The solution detection chamber is also equipped with a conductivity detection device to detect the conductivity of the solution in the detection chamber; the wastewater chamber is used to hold the water sample to be tested, and the water sample enters the clear water chamber after being filtered through the impurity filter layer; The monitoring system also includes an alarm device, a wireless communication module, and a controller. The conductivity detection device is a conductivity sensor. The controller is used to obtain the detection results from the conductivity sensor. The wireless communication module is used to send the detection results obtained by the controller to a host computer. The signal output terminal of the conductivity sensor is connected to the signal input terminal of the controller, and one signal output terminal of the controller is connected to the alarm device. The alarm device is a sound alarm or a warning light, which emits an alarm signal when the conductivity is lower than a preset threshold. The host computer is a mobile phone, tablet, or computer.

2. The monitoring system for sulfate erosion of railway subgrade based on diffusion dialysis according to claim 1, characterized in that: The impurity filtration layer is composed of multiple layers of filter mesh or a filter membrane.

3. The monitoring system for sulfate erosion of railway subgrade based on diffusion dialysis according to claim 1, characterized in that: The top of the sewage tank is also equipped with an overflow outlet for overflowing excess water; the bottom of the sewage tank is equipped with a drain outlet for discharging solid impurities.

4. The monitoring system for sulfate erosion of railway subgrade based on diffusion dialysis according to claim 1, characterized in that: The Ba 2+ The solution was selected from BaCl2 solution.

5. The monitoring system for sulfate erosion of railway subgrade based on diffusion dialysis according to claim 1, characterized in that: The monitoring system also includes a water guide pipe, the top of which is open, and the cross-section of which is U-shaped or V-shaped. The top of the sewage tank is equipped with a water inlet, and a water pipe is connected to the water inlet of the sewage tank to guide the water collected in the water pipe from the roadbed into the sewage tank.

6. A method for real-time monitoring of sulfate erosion damage in railway subgrade, characterized in that, Monitoring using the monitoring system described in claim 5 includes the following steps: S1. Laying the monitoring system: Drilling holes from the bottom of the side of the railway subgrade into the subgrade, and placing the monitoring system described in claim 5 into the drilled holes; Water diversion channels are drilled at an angle downwards on the side of the roadbed, and water pipes are placed into the water diversion channels. The end of the water pipe is connected to the inlet of the sewage tank of the monitoring system, and the water collected in the water pipe is introduced into the sewage tank. S2. Real-time monitoring: Monitors the conductivity data in the detection chamber. When the conductivity value approaches or reaches the set threshold, it indicates that SO4 has been detected in the water sample. 2- Ions indicate that sulfate erosion is occurring or will occur in the roadbed.

7. The real-time monitoring method according to claim 6, characterized in that: In step S1, multiple water diversion channels are drilled from top to bottom on the side of the roadbed. The multiple water diversion channels are arranged in a straight line. A water guide pipe is placed in each water diversion channel. The lower water guide pipe is longer than the upper water guide pipe and is used to collect water that seeps from the top down. The end of the lowermost water guide pipe is connected to the inlet of the sewage tank to introduce the collected water sample into the sewage tank.

8. The real-time monitoring method according to claim 6, characterized in that: The monitoring system is periodically removed from the roadbed ducts, and the Ba in the detection chamber is replaced. 2+ The solution was used to clean impurities from the sewage tank.

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