An early warning system and method for railway subgrade sulfate attack based on ion electrodialysis

Abstract

The present invention discloses an early warning system and method for railway roadbed sulfate erosion disease based on ion electrodialysis. The system includes a closed detection box, an electric field generating device, and a sulfate content detecting device. The interior of the detection box is divided into a filter chamber, a clean water chamber, and a detection chamber from left to right. At least one level of impurity filtering layer is provided between the filter chamber and the clean water chamber. An electrodialysis anion membrane is provided between the clean water chamber and the detection chamber to separate the two chambers. The cathode of the electric field generating device is located in the clean water chamber, and the anode is located in the detection chamber. The sulfate content detecting device is used to detect the sulfate content in the detection chamber. The electrodialysis anion membrane is used to allow sulfate ions to selectively pass through under the action of the electric field and enter the detection chamber from the clean water chamber. The filter chamber is used to hold water samples to be tested, and the detection chamber is used to hold Ba 2+ The water sample to be tested is filtered through the impurity filter layer and then enters the clean water tank. The sulfate ions in the clean water tank enter the detection tank and react with Ba 2+ A reaction occurs.

Description

Technical Field

[0001] The present invention relates to the technical field of railway roadbed engineering, and in particular to an early warning system and method for railway roadbed sulfate erosion damage based on ion electrodialysis. Background Art

[0002] Railway subgrade transition sections are areas requiring special treatment where the subgrade meets other structures, such as those between embankments and bridge abutments, embankments and transverse structures, embankments and cuttings, and cuttings and tunnels. These transition sections gradually change the stiffness of the track, reducing vibration between trains and tracks, slowing deformation of the subgrade structure, and ensuring safe, smooth, and comfortable train operation. Railway subgrade transition sections are typically constructed using cement-graded crushed stone. These sections are made by dry-mixing cement and graded crushed stone that meet regulatory requirements, then adding water. They primarily serve to transition stiffness between different sections (bridges, tunnels, and roads) and are crucial for smooth train operation.

[0003] In recent years, the problem of high-speed railway roadbed deformation has become very prominent, especially the problem of roadbed transition section arching due to sulfate erosion has become increasingly serious. The sulfate erosion problem of cement-graded gravel 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 gravel with excessive sulfate content in the preparation of cement-graded gravel, thereby directly introducing a large amount of sulfate into the cement-graded gravel material. The sulfate further reacts with the cement in the cement-graded gravel and its hydration reaction products to generate expansive products, mainly ettringite, a colorless to yellow calcium aluminum sulfate mineral with a chemical formula of 3CaO·Al2O33CaSO4·32H2O. The amount of crystal water is related to the environment, causing volume expansion and ultimately leading to roadbed arching. (2) Exogenous sulfate erosion mainly refers to the presence of a large amount of sulfate in the environment (water and soil) of the roadbed transition section. Through the medium of water, sulfate comes into contact with cement-graded gravel and reacts with cement and its hydration reaction products in the cement-graded gravel to produce expansive substances mainly composed of ettringite, which causes volume expansion and eventually leads to the arching of the roadbed.

[0004] Sulfate attack-induced arching is characterized by its hidden location, slow development, and irreversible reaction, making it a persistent durability problem for railway subgrades that is difficult to predict and remediate. High-speed rail imposes strict limits on the amount of arching deformation in the subgrade, making it difficult to visually detect. Typically, a railcar detecting deformation on the track surface then, after considering various factors, determines that it is caused by a reaction within the subgrade. Samples are then drilled on-site and sent to a laboratory for testing to verify excessive sulfate levels, ultimately determining whether the arching is caused by sulfate attack. Current testing methods for sulfate attack rely on first observing arching deformation on-site, then drilling samples and sending them to a laboratory for testing to verify excessive sulfate levels and ultimately determine whether the arching is caused by sulfate attack. Obviously, this testing method can only be implemented after significant arching is detected, meaning it is only possible to determine whether sulfate attack has occurred. When the chemical reaction of sulfate attack within the roadbed has already occurred, but the expansive products have not yet accumulated enough to produce significant macroscopic deformation, there is no early warning. However, when obvious and detectable arching deformation occurs, the disease is already extremely serious, and the difficult decision of slowing down or stopping the high-speed rail may have to be made, seriously threatening the safety and stable operation of the high-speed rail. In addition, this method is time-consuming, inefficient, and highly affected by human factors. Therefore, there is an urgent need to develop a measurement method that can detect and indicate potential diseases in the early stages of the reaction, especially when the reaction conditions are met but the reaction has not yet occurred or has just occurred. It is simple to operate, less affected by human factors, low in cost, and will not affect railway operations. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned problems and provide an early warning system and method for railway subgrade sulfate erosion damage based on ion electrodialysis.

[0006] In order to achieve its purpose, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides an early warning system for railway roadbed sulfate erosion disease based on ion electrodialysis, comprising a closed detection box, an electric field generating device and a sulfate content detecting device, wherein the interior of the detection box is divided into a filter chamber, a clean water chamber and a detection chamber from left to right; an electric hatch or a filter screen is provided on the partition between the filter chamber and the clean water chamber for water to pass through, and at least one level of impurity filtering layer is provided between the filter chamber and the clean water chamber; an electrodialysis anion membrane is provided between the clean water chamber and the detection chamber to separate the two chambers, the cathode of the electric field generating device is located in the clean water chamber, and the anode is located in the detection chamber; the sulfate content detecting device is used to detect the sulfate content in the detection chamber; the impurity filtering layer is used to filter solid impurities, and the electrodialysis anion membrane is used to allow sulfate ions to selectively pass through under the action of the electric field and enter the detection chamber from the clean water chamber; the filter chamber is used to hold water samples to be tested, and the detection chamber is used to hold Ba 2+ The water sample to be tested is filtered through the impurity filter layer and then enters the clean water tank. The sulfate ions in the clean water tank enter the detection tank through the electrodialysis anion membrane and react with Ba 2+ A reaction occurs.

[0008] Preferably, the solution in the detection chamber further contains hydrochloric acid or nitric acid to remove the influence of carbonate ions in the water sample to be tested;

[0009] The sulfate content detection device is a current detection device, which is used to detect the current of the solution in the detection chamber and judge whether the water sample to be tested contains sulfate by the change of the solution current. Or,

[0010] The sulfate content detection device includes one or a combination of the following structures:

[0011] Structure 1: A current sensor is installed in the detection chamber. The signal output terminal of the current sensor is connected to a signal input terminal of the controller, and a signal output terminal of the controller is connected to the first alarm device. The controller is used to obtain the detection results of the current sensor and the voltage value of the electric field generator. The electric field generator is set to constant current mode. If the voltage of the electric field generator reaches the upper voltage limit and the current value in the solution detected by the current sensor is lower than the set value, the controller controls the first alarm device to alarm. A wireless communication module can also be used to transmit the detection results obtained by the controller to a host computer. The wireless communication module can upload the detection results to the host computer via GPRS or LPWAN Internet of Things protocol for manual review. The host computer can be a mobile phone, tablet, or computer. The monitoring personnel read the current readings through the host computer. The wireless communication module can be a ZigBee wireless communication module or a Wi-Fi wireless communication module.

[0012] Structure 2: A laser emitting device is provided on one side of the detection chamber, and a laser receiving device is provided on the other side of the detection chamber. The output end of the laser receiving device is connected to a signal input end of the controller, and a signal output end of the controller is connected to the second alarm device. When the laser receiving device cannot receive the light emitted by the laser emitting device, the signal is transmitted to the controller, and the controller controls the second alarm device to alarm.

[0013] Preferably, the filter chamber is provided with a multi-stage impurity filter layer, and the impurity filter layer is a filter mesh or a filter membrane; the top of the filter chamber is also provided with an overflow port for overflowing excess water; the bottom of the filter chamber is provided with a sewage outlet for discharging solid impurities;

[0014] The height of the filter bin is higher than that of the clean water bin. A filter is set on the upper part of the partition between the filter bin and the clean water bin for water to pass through. The water in the filter bin accumulates to the height of the filter before passing through the filter and entering the clean water bin. When the early warning system is used at the railway subgrade site, it can enter the detection bin to trigger detection only after sufficient water samples have accumulated.

[0015] Preferably, the electric door is connected to a controller, and the controller controls the electric door to open periodically; or, the electric door control end is connected to a timing output end of a timer, and the timer controls the electric door to open periodically.

[0016] Preferably, the early warning system for railway subgrade sulfate attack based on ion electrodialysis also includes a water pipe, the top of which is open and the cross-section of which is U-shaped or V-shaped; a water inlet is provided at the top of the filter tank, and the water pipe is connected to the water inlet of the filter tank to drain the water gathered in the water pipe from the roadbed into the filter tank.

[0017] A second aspect of the present invention provides a real-time monitoring method for railway subgrade sulfate attack damage, using any of the above-mentioned early warning systems for monitoring, comprising the following steps:

[0018] S1. Laying the monitoring system: drilling a channel from the bottom of the side of the railway roadbed to the inside of the roadbed, and placing the early warning system of the present invention into the drilled channel;

[0019] A water diversion channel is drilled obliquely downward on the side of the roadbed, a water pipe is placed in the water diversion channel, the end of the water diversion pipe is connected to the water inlet of the filter tank of the early warning system, and the water collected in the water diversion pipe is introduced into the filter tank;

[0020] S2. Real-time monitoring: monitor the sulfate content in the detection chamber. When the sulfate content reaches the set threshold, it means that SO4 is detected in the water sample. 2- ions, sulfate attack in the roadbed is occurring or will be affected by sulfate attack in the future.

[0021] In step S1, multiple water diversion channels arranged in the same straight line are drilled from top to bottom on the side of the roadbed. A water pipe is placed in each water diversion channel. The lower water pipe is longer than the upper water pipe and is used to collect water leaking from the top downward. The water collected from the upper, middle and lower parts of the roadbed converges in the lowest water pipe. The end of the lowest water pipe is connected to the water inlet of the filter chamber to introduce the collected water sample into the filter chamber.

[0022] In step S2, the method for determining whether the sulfate content reaches the threshold value is any one of the following two methods or a combination of the two:

[0023] Method 1:

[0024] S21, start the electric field generating device, set a constant current value I0 on the electric field generating device, and apply a voltage V0 to form an electric field on both sides of the electrodialysis anion membrane;

[0025] S22, a current sensor detects a current value in the solution in the detection chamber;

[0026] S23. When the current value is lower than the set value, the controller determines whether the voltage of the electric field generating device has reached the voltage upper limit. If so, step S24 is executed. If not, step S22 is returned to execution.

[0027] S24. If the voltage of the electric field generating device reaches the upper voltage limit and the current value in the solution detected by the current sensor is lower than the set value, it is considered that the sulfate content has reached the threshold value, and the controller controls the first alarm device to sound an alarm;

[0028] Method 2:

[0029] The laser receiving device receives the light emitted by the laser emitting device. When the laser receiving device cannot receive the light emitted by the emitting device, it is considered that the sulfate content has reached a threshold value, and the second alarm device is controlled to alarm.

[0030] The judgment method of combining the two methods to determine whether the sulfate content has reached the threshold is as follows: when only one of the first alarm device and the second alarm device alarms and the other does not alarm, it indicates that a small amount of sulfate ions exists in the water sample; when the first alarm device and the second alarm device alarm successively or simultaneously, it is judged that the water sample to be tested contains a large amount of sulfate ions, the railway subgrade structure faces the risk of sulfate erosion or sulfate erosion disease has occurred, and timely remediation should be carried out.

[0031] The beneficial effects of the present invention are:

[0032] 1. Accuracy: Through testing and calculation, it can be determined whether the roadbed transition section has suffered sulfate erosion and the extent of erosion.

[0033] 2. Preventive: By regularly inspecting the railway subgrade, sulfate attack problems can be discovered in time before they become serious and corresponding preventive measures can be taken, thereby extending the service life of the railway.

[0034] 3. Economical: Compared to the damage and repair costs of railways caused by sulfate attack, the economic benefits of this method are significant. By placing the system in the roadbed, the railway subgrade can be monitored for sulfate attack in real time. Compared to periodic sampling and laboratory testing, on-site real-time monitoring significantly reduces labor and time costs.

[0035] 4. Safety: Sulfate erosion can lead to railway subgrade instability, which in turn affects the safe operation of trains. Timely detection can effectively reduce this risk and ensure the safety of railway transportation. This method is also harmless to the railway subgrade.

[0036] 5. Wide applicability: This method is not only applicable to the assessment of new railway subgrades, but also to the inspection and maintenance of existing railway subgrades. The early warning system of the present invention can be used in the laboratory or for real-time monitoring and early warning of subgrades on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the assembly diagram of the verification experimental device in Example 1.

[0038] Figure 2 This is the observation diagram of the experimental results of the electrodialysis anion membrane ions passing through the experimental group-7.

[0039] Figure 3 Schematic diagram of the structure of the early warning system for railway subgrade sulfate attack according to a certain embodiment of the present invention.

[0040] Figure 4 Schematic diagram of the structure of the early warning system for railway subgrade sulfate attack according to a certain embodiment of the present invention.

[0041] Figure 5 yes Figure 3 Schematic diagram of the structure of the central water pipe.

[0042] Figure 6 The figure is a control flow diagram of a certain embodiment of the early warning system for railway subgrade sulfate attack diseases according to the present invention.

[0043] Figure 7 The present invention is a schematic diagram of on-site installation and monitoring of a railway subgrade sulfate attack disease monitoring system in a subgrade.

[0044] Figure 3-6 , the elements or structures indicated by the reference numerals are:

[0045] Detection box 1, impurity filtration layer 2, electrodialysis anion membrane 3, filtration chamber 4, clean water chamber 5, detection chamber 6, electric field generating device 7, laser emitting device 8, laser receiving device 9, water pipe 10, electric hatch 11, first alarm device 12, wireless communication module 13, controller 14, current sensor 15. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the embodiments, but the present invention is not limited thereto.

[0047] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0048] Sources of main materials and reagents:

[0049] Electrodialysis anion membrane: Electrodialysis anion membrane realizes ion migration under the action of DC electric field, allowing anions to pass through the membrane while blocking cations. The electrodialysis anion membrane used in the present invention is an anion membrane suitable for sulfate system, allowing sulfate ions to pass through the membrane while blocking Ba 2+ The membrane was purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1RL.

[0050] Barium chloride: BaCl2, commercially available.

[0051] Main equipment:

[0052] A DC regulated power supply (UNI-T, model UTP1605S) was used as an electric field generator. The cathode of the generator was placed in water containing sulfate, and the anode was placed in a solution containing BaCl2. A DC regulated power supply is an electronic device that provides a stable DC power supply to a load.

[0053] Example 1

[0054] In this embodiment, a preliminary experiment for feasibility verification of the detection principle was conducted in the laboratory.

[0055] Experimental device: laboratory H-type double-chamber electrolytic cell (sealed type) and DC regulated power supply were used.

[0056] A total of 7 groups of experiments were set up. In each group of experiments, a set of H-type double-chamber electrolytic cells was used. The side mouths of the left and right chamber electrolytic cell bottles were connected, and the electrodialysis anion membrane was installed at the connection point and fixed with stainless steel clips (such as Figure 1(as shown), pour different solutions into the left and right chambers, respectively. Use a DC regulated power supply as the electric field generator. Connect the power plug of the DC regulated power supply to an AC outlet. Connect the alligator clip test leads of the DC regulated power supply to the electrodes, with the anode in the right chamber containing BaCl2 and the cathode in the left chamber containing Na2SO4. After turning on the device, continuously observe the current value in the solution displayed by the DC regulated power supply.

[0057] According to the provisions of the "Railway Concrete Structure Durability Design Code" on the action level of chemical corrosion environment, set the SO4 2- Concentration: In this regulation, the H1 level is 200-1000 mg / L, the H2 level is 1000-4000 mg / L, the H3 level is 4000-10000 mg / L, and the H4 level is 10000-20000 mg / L.

[0058] 1. The first phase of the experiment

[0059] Objective: To verify the effectiveness of the early warning system under different sulfate concentrations.

[0060] Principle: The sulfate ions in the left ventricle pass through the electrodialysis negative membrane and enter the right ventricle, where they react with BaCl2 to form BaSO4 precipitates. Since BaSO4 precipitates are non-conductive, they cause changes in current.

[0061] Experimental Group-1

[0062] Experimental setup: The left ventricle was filled with a 200 mg / L Na₂SO₄ solution, and the right ventricle was filled with a 0.2 g / L BaCl₂ solution combined with a large amount of 1 mol / L HCl solution. The DC power supply had a maximum voltage of 60 V and a constant current of 0.03 A.

[0063] The results are shown in Table 1. The sulfate ions in the left chamber passed through the electrodialysis anion membrane and reacted with the BaCl2 in the right chamber to precipitate, resulting in a current drop and the formation of a precipitate in the constant current mode.

[0064] In experimental group 1, the measured current in the solution was low due to the low sulfate ion concentration. In actual application, when the sulfate ion concentration is low, no large amount of precipitation will be produced, and the first alarm mechanism will not be activated. When the reaction time is long and enough precipitation has accumulated, the second alarm mechanism will be triggered.

[0065] Table 1

[0066] Time (h) Voltage (v) Current (A) 0 60 0.007 3 60 0.012 4 60 0.010 6 60 0.006 7 60 0 12 60 0

[0067] Experimental Group-2

[0068] Experimental setup: The left chamber contained a 1000mg / L Na₂SO₄ solution, and the right chamber contained a 0.2g / L BaCl₂ solution combined with a large amount of 1mol / L HCl solution. The DC power supply had a maximum voltage of 60V and a set constant current of 0.03A.

[0069] The results are shown in Table 2. The sulfate ions in the left ventricle passed through the electrodialysis anion membrane and reacted with BaCl2 in the right ventricle to produce a precipitation reaction. Under the constant current mode, the current decreased within 7 hours, and precipitation was observed around 4 hours.

[0070] Table 2

[0071] Time (h) Voltage (v) Current (A) 0 43.5 0.03 1 36.62 0.03 2 49.54 0.03 3 42.35 0.03 4 37.07 0.03 6 50.82 0.03 7 60 0.019

[0072] Experimental Group-3

[0073] Experimental setup: The left chamber was filled with a 4000mg / L Na2SO4 solution, and the right chamber was filled with a 0.2g / L BaCl2 solution combined with a large amount of 1mol / L HCl solution. The DC power supply had a maximum voltage of 60V and a set constant current of 0.03A.

[0074] The results are shown in Table 3. The sulfate ions in the left ventricle passed through the electrodialysis anion membrane and reacted with BaCl2 in the right ventricle to produce precipitation. Under the constant current mode, the current dropped within 4 hours and a large amount of precipitation was generated in a short time.

[0075] Table 3

[0076]

[0077]

[0078] Experimental Group-4

[0079] Experimental setup: The left chamber contained an 8000mg / L Na2SO4 solution, and the right chamber contained a 0.2g / L BaCl2 solution combined with a large amount of 1mol / L HCl solution. The DC power supply had a maximum voltage of 60V and a constant current of 0.03A.

[0080] The results are shown in Table 4. The sulfate ions in the left ventricle passed through the electrodialysis anion membrane and reacted with BaCl2 in the right ventricle for precipitation. Under the constant current mode, the current decreased after 5.5 hours, and a large amount of precipitation was generated in a short time (1.5 hours).

[0081] Table 4

[0082]

[0083] 2. Second Phase of the Experiment

[0084] Experimental purpose: To verify whether the early warning system is effective in the presence of interfering ions (such as carbonate).

[0085] Principle: Other ions, such as carbonate ions, may also exist in the environment surrounding the railway subgrade. In this experiment, when the interfering ion carbonate is present, carbonate can pass through the electrodialysis anion membrane from the left chamber into the right chamber and react with BaCl2 to form a BaCO3 precipitate. Since the right chamber contains HCl, HCl reacts with BaCO3 to dissolve the BaCO3 precipitate, preventing the BaCO3 precipitate from interfering with the current. However, sulfate ions from the left chamber enter the right chamber and react with BaCl2 to form a BaSO4 precipitate, which does not dissolve in HCl. Since the BaSO4 precipitate is non-conductive, it causes a change in the current.

[0086] Experimental Group-5

[0087] Experimental setup: The left ventricle contained 1000 mg / L Na₂SO₄ and 4000 mg / L Na₂CO₃. The right ventricle contained 0.2 g / L BaCl₂ and 1 mol / L HCl. The DC power supply had a maximum voltage of 60 V and a constant current of 0.03 A.

[0088] The results are shown in Table 5. The sulfate ions in the left ventricle passed through the electrodialysis negative membrane and reacted with BaCl2 in the right ventricle for precipitation. No current drop occurred in the constant current mode. This is because there are a large amount of sodium carbonate, hydrochloric acid, etc. as conductive substances in the system. Therefore, the first alarm mechanism will not be activated; but precipitation will begin to form after about 2 hours, at which time the second alarm mechanism will be activated.

[0089] In actual situations, when this occurs, other factors can be combined, such as analyzing whether a large amount of carbonates will appear at the roadbed location, to produce a comprehensive analysis of this situation. If there is no possibility of a large amount of carbonates appearing at the roadbed location, the above results can indicate that the roadbed is at risk of sulfate attack, but the concentration is not high. If there is a possibility of a large amount of carbonates at the roadbed location, further observation is required (this is because the presence of a large amount of carbonates and hydrochloric acid in the system can act as conductive materials, compensating for the decrease in conductivity caused by precipitation, so the first alarm mechanism is not activated); after further precipitation accumulation, until the conductivity gain effect of carbonates and hydrochloric acid is completely offset, the current will decrease, at which point it can be determined that the roadbed is at risk of sulfate attack.

[0090] Table 5

[0091]

[0092] Experimental Group-6

[0093] Experimental configuration: The left chamber contained 4000 mg / L Na2SO4 and 4000 mg / L Na2CO3, and the right chamber contained 0.2 g / L BaCl2 and 1 mol / L HCl. The maximum voltage of the DC regulated power supply was 60 V, and the set constant current was 0.03 A.

[0094] The results are shown in Table 6. The sulfate ions in the left ventricle passed through the electrodialysis anion membrane and reacted with BaCl2 in the right ventricle for precipitation. No current drop occurred in the constant current mode. This is because there are a large amount of sodium carbonate, hydrochloric acid, etc. as conductive substances in the system. Therefore, the first alarm mechanism will not be activated; but precipitation begins to form after about 2 hours, which can activate the second alarm mechanism.

[0095] Table 6

[0096]

[0097] Experimental Group-7

[0098] Experimental configuration: The left chamber contained 10,000 mg / L Na₂SO₄ and 4,000 mg / L Na₂CO₃, and the right chamber contained 0.2 g / L BaCl₂ and 1 mol / L HCl. The maximum voltage of the DC regulated power supply was 60 V, and the set constant current was 0.03 A.

[0099] The results are shown in Table 7. The sulfate ions in the left ventricle passed through the electrodialysis membrane and reacted with the BaCl2 in the right ventricle to precipitate (as shown in Table 7). Figure 2 ), no current drop occurs in constant current mode. This is because there are a large amount of sodium carbonate, hydrochloric acid, etc. as conductive substances in the system, so the first alarm mechanism will not be activated; but after about 1 hour, precipitation begins to form, which can activate the second alarm mechanism.

[0100] Table 7

[0101]

[0102]

[0103] The detection and early warning principles of this embodiment are as follows:

[0104] In constant current mode (the electric field generator automatically adjusts the applied voltage to ensure a constant current in the solution), the current change in the solution is measured to determine whether the conductivity has dropped significantly due to the formation of precipitation, and then an alarm is triggered.

[0105] The detailed principle is as follows: first, set a constant current value I0 on the electric field generating device, start the device and apply voltage V0 to form an electric field on both sides of the electrodialysis anion membrane. If BaSO4 precipitates are generated, the resistance of the solution will increase and the current in the solution will decrease. In order to ensure that the current reaches the set value, the device will automatically increase the voltage to V1 so that the current in the solution reaches I0 again; next, under the action of the electric field, sulfate ions continue to pass through the electrodialysis anion membrane and react with BaSO4. 2+ The reaction generates a precipitate, and the resistance rises again, causing the current to drop. The device increases the voltage to V2 again to make the current reach I0 again, and this cycle repeats until the voltage reaches the upper limit V of the device. max , the subsequent increase in resistance caused by precipitation, which in turn causes the current to fall below the set value, cannot be restored by increasing the voltage. In this case, it is determined that a large amount of precipitation has been generated, and an alarm is issued. The advantages of this approach are: first, the principle is simple, and the amount of sulfate reaction can be detected through electrical signals; second, it has high fault tolerance. Even if some trace precipitation is generated, causing the current to drop, the detection can be restored by increasing the voltage. Only when a large amount of sulfate ions enter the system will an alarm be triggered. This corresponds to the actual situation that only the presence of a large amount of sulfate will endanger the safety of the roadbed structure; third, by setting the constant current mode, the electric field loaded on both ends of the electrodialysis anion membrane can be ensured to be always at a large value, ensuring the efficiency of sulfate ions passing through the membrane with the help of the electric field, and preventing the formation of precipitation blocking the membrane surface, resulting in a significant decrease in sulfate ion permeability and a decrease in detection efficiency. Because during long-term monitoring, the possibility of other ions existing in nature entering the warning system and causing a small amount of precipitation cannot be ruled out. After the formation of precipitation, increasing the voltage can compensate for the decrease in permeability caused by such precipitation blocking the electrodialysis anion membrane (the physical meaning of current consistency is that the total amount of ionic charge passing through the membrane per unit time is the same).

[0106] Example 2: An early warning system for railway subgrade sulfate attack based on ion electrodialysis

[0107] like Figure 3The invention shows an early warning system for sulfate erosion disease on railway subgrade based on ion electrodialysis, which is mainly composed of a closed detection box (insulated shell), an electric field generating device, and a sulfate content detecting device. The interior of the detection box is divided into a filter chamber, a clean water chamber and a detection chamber from left to right; an electric hatch or a filter screen is provided on the partition between the filter chamber and the clean water chamber for water to pass through, and at least one level of impurity filtering layer is provided between the filter chamber and the clean water chamber; an electrodialysis anion membrane is provided between the clean water chamber and the detection chamber to separate the two chambers, the cathode of the electric field generating device is located in the clean water chamber, and the anode is located in the detection chamber; the sulfate content detecting device is used to detect the sulfate content in the detection chamber; the impurity filtering layer is used to filter solid impurities, and the electrodialysis anion membrane is used to allow sulfate ions to selectively pass through under the action of a DC electric field and enter the detection chamber from the clean water chamber; the filter chamber is used to hold water samples to be tested, and the detection chamber is used to hold Ba 2+ The water sample to be tested is filtered through the impurity filter layer and then enters the clean water tank. The sulfate ions in the clean water tank enter the detection tank through the electrodialysis anion membrane and react with Ba 2+ Preferably, the Ba 2+ The solution is selected from BaCl2 solution.

[0108] In some embodiments, hydrochloric acid solution is added to the detection chamber to remove the influence of carbonate ions in the water sample on the detection results. The railway subgrade may or may not contain carbonate ions. For the detection of sections where carbonate ions are found in advance, in addition to adding Ba 2+ In addition to the solution, hydrochloric acid or nitric acid can also be added. The BaCO3 precipitate generated by carbonate entering the detection chamber is dissolved by hydrochloric acid or nitric acid to avoid affecting the test results.

[0109] In some embodiments, the sulfate content detection device is a current detection device, which is used to detect the current of the solution in the detection chamber and determine whether the water sample to be tested contains sulfate by changes in the solution current. Preferably, the current detection device and the electric field generating device are integrated into a device and can use a DC regulated power supply.

[0110] In some embodiments, the sulfate content detection device includes one or a combination of the following structures:

[0111] Structure 1: A current sensor is set in the detection chamber, such as Figure 7As shown, the signal output terminal of the current sensor is connected to a signal input terminal of the controller, and a signal output terminal of the controller is connected to the first alarm device. The controller is used to obtain the detection results of the current sensor and the voltage value of the electric field generating device. The electric field generating device is set to constant current mode. If the voltage of the electric field generating device reaches the upper voltage limit and the current value in the solution detected by the current sensor is lower than the set value, the controller controls the first alarm device to alarm. A wireless communication module can also be used to transmit the detection results obtained by the controller to a host computer. The wireless communication module can upload the detection results to the host computer via GPRS or LPWAN Internet of Things protocol for manual review. The host computer can be a mobile phone, tablet, or computer, and the monitoring personnel can read the current through the host computer. The wireless communication module can be a ZigBee wireless communication module or a Wi-Fi wireless communication module.

[0112] Structure 2: A laser emitting device is provided on one side of the detection chamber, and a laser receiving device is provided on the other side of the detection chamber. The output end of the laser receiving device is connected to a signal input end of the controller, and a signal output end of the controller is connected to the second alarm device. When the laser receiving device cannot receive the light emitted by the laser emitting device, the signal is transmitted to the controller, and the controller controls the second alarm device to alarm.

[0113] Preferably, the first alarm device or the second alarm device is a sound alarm or a warning light.

[0114] In some embodiments, the filter chamber is provided with a multi-stage impurity filtration layer. Preferably, a secondary impurity filtration layer is provided in the filter chamber to divide the interior of the filter chamber into three chambers. Multi-stage filtration removes solid impurities. Heavier impurities such as particles and dust will preferentially settle at the bottom of each chamber and will not clog the impurity filtration layer, thereby preventing impurities from entering the clear water chamber and the detection chamber and affecting detection. The impurity filtration layer is a filter mesh or a filter membrane.

[0115] In some embodiments, as Figure 4 As shown, the height of the filter bin is higher than that of the clean water bin, and a filter is set on the upper part of the partition between the filter bin and the clean water bin for water to pass through. This arrangement makes it easy for the water in the filter bin to accumulate to a certain volume, reach a certain water pressure, and reach the filter height before passing through the filter to enter the clean water bin. When the early warning system is used at the railway roadbed site, it can enter the detection bin to trigger the detection alarm only after sufficient water samples have accumulated.

[0116] In some embodiments, the electric door is connected to a controller, and the controller controls the electric door to open periodically.

[0117] In some embodiments, the electric door control terminal is connected to a timing output terminal of a timer, and the timer controls the electric door to open periodically.

[0118] In some embodiments, the early warning system of the present invention further comprises a water conduit, such as Figure 5 As shown, the top of the water pipe is open, and the cross-section of the water pipe is U-shaped or V-shaped; a water inlet is provided on the top of the filter tank, and the water pipe is connected to the water inlet of the filter tank to drain the water gathered in the water pipe from the roadbed into the filter tank.

[0119] In some embodiments, the top of the filter tank is further provided with an overflow port for overflowing excess water; the bottom of the filter tank is provided with a sewage outlet for discharging solid impurities.

[0120] The working principle of the railway roadbed sulfate attack early warning system of the present invention is:

[0121] The test chamber is filled with Ba of known concentration 2+ Solution, the water sample to be tested is filtered out of impurities from the filter chamber and enters the clean water chamber. If the water sample contains SO4 2- ions, under the action of an external electric field, SO4 2- Ions enter the detection chamber from the clean water chamber through the electrodialysis anion membrane, and Ba 2+ Cannot pass through the electrodialysis anion membrane into the clean water tank, SO4 2- Enter the inspection room and 2+ The reaction generates BaSO4 precipitate. There are two ways to determine whether there is SO4 2- Entering the inspection chamber:

[0122] The first one: Since BaSO4 is non-conductive, it causes the solution current to change. The electric field generator is set to constant current mode. After the generated BaSO4 precipitation causes the current to drop, the electric field generator automatically increases the voltage to maintain constant current. If the voltage of the electric field generator reaches the upper voltage limit and the current value in the solution is lower than the set value, it means that there is a certain amount of SO4 in the water sample to be tested. 2- The monitoring personnel will judge whether sulfate erosion has occurred or is about to occur in the roadbed structure based on the alarm situation, and take timely remediation measures.

[0123] The second type: After BaSO4 precipitation is generated in the detection chamber, the precipitation will block the light emitted by the laser emitting device, causing the laser receiving device to be unable to receive the light emitted by the laser emitting device, and the second alarm device will sound an alarm.

[0124] Ba 2+ With SO4 2- The reaction equation is as follows:

[0125]

[0126] In actual application, sulfate ions are almost undetectable in water samples taken from roadbed sections where sulfate erosion has not occurred, while sulfate ions are present in water samples taken from roadbed sections where sulfate erosion is a risk or where sulfate erosion has already occurred. As long as the BaCl2 content in the storage tank is sufficient, it is possible to detect whether sulfate ions have entered and caused a significant change in the solution current or caused the laser receiving device to be unable to receive the light emitted by the transmitting device. It is worth noting that due to the SO4 2- Ba as an ion indicator 2+ The filling capacity is limited, and the equipment deployed in the field is supplemented. 2+ Therefore, the device needs to be taken out and Ba injected into the detection chamber again after a period of service. 2+ solution.

[0127] In practical applications, water samples are collected by drilling holes at railway subgrade sites where sulfate attack is observed. Holes are drilled from the sides of the subgrade toward the interior, then piped into the subgrade for drainage. Water samples are collected at the end of the pipe using glass bottles. Alternatively, water samples can be collected directly from the subgrade's drainage ditch, which can also provide a certain degree of insight into sulfate attack. The collected water samples are then sent to a laboratory for testing using the monitoring system of the present invention.

[0128] Example 3: A real-time monitoring method for railway subgrade sulfate erosion damage

[0129] The railway roadbed sulfate attack disease early warning system of the present invention in Example 2 is used for detection, and real-time monitoring is performed on railway roadbed sections where sulfate attack is suspected or predicted to occur. The early warning system of the present invention can be manufactured as a small or micro device and placed inside the roadbed. The operation is carried out according to the following steps (the on-site monitoring schematic diagram is shown in FIG). Figure 6 shown):

[0130] S1. Laying the monitoring system: drilling a channel from the bottom of the side of the railway roadbed to the inside of the roadbed, and placing the early warning system of the present invention into the drilled channel;

[0131] A water diversion channel is drilled obliquely downward on the side of the roadbed, a water pipe is placed in the water diversion channel, the end of the water diversion pipe is connected to the water inlet of the filter tank of the early warning system, and the water collected in the water diversion pipe is introduced into the filter tank;

[0132] In order to improve the accuracy of reflecting the sulfate erosion situation inside the roadbed, multiple water diversion channels arranged in the same straight line are drilled from top to bottom on the side of the roadbed. A water pipe is placed in each water diversion channel. The lower water pipe is longer than the upper water pipe and is used to collect water leaking from the top downward. The water collected from the upper, middle and lower parts of the roadbed converges in the lowest water pipe. The end of the lowest water pipe is connected to the water inlet of the filter tank to introduce the collected water sample into the filter tank.

[0133] S2. Real-time monitoring: monitor the sulfate content in the detection chamber. When the sulfate content reaches the set threshold, it means that SO4 is detected in the water sample. 2- ions, sulfate attack in the roadbed is occurring or will be affected by sulfate attack in the future.

[0134] The method for determining whether the sulfate content reaches the threshold is either or a combination of the following two methods:

[0135] Method 1:

[0136] S21, start the electric field generating device, set a constant current value I0 on the electric field generating device, and apply a voltage V0 to form an electric field on both sides of the electrodialysis anion membrane;

[0137] S22, a current sensor detects a current value in the solution in the detection chamber;

[0138] S23. When the current value is lower than the set value, the controller determines whether the voltage of the electric field generating device has reached the voltage upper limit. If so, step S24 is executed. If not, step S22 is returned to execution.

[0139] S24. If the voltage of the electric field generating device reaches the upper voltage limit and the current value in the solution detected by the current sensor is lower than the set value, it is considered that the sulfate content has reached the threshold value, and the controller controls the first alarm device to sound an alarm;

[0140] Method 2:

[0141] The laser receiving device receives the light emitted by the laser emitting device. When the laser receiving device cannot receive the light emitted by the emitting device, it is considered that the sulfate content has reached a threshold value, and the second alarm device is controlled to alarm.

[0142] The method of combining two methods to determine whether the sulfate content has reached the threshold is as follows: when only one of the first alarm device and the second alarm device sounds an alarm and the other does not, it indicates that a small amount of sulfate ions exists in the water sample; when the first alarm device and the second alarm device both sound an alarm successively or simultaneously, it is judged that the water sample to be tested contains a large amount of sulfate ions, and the railway subgrade structure is facing the risk of sulfate erosion or sulfate erosion disease has occurred, and timely remediation should be carried out. The specific judgment method is:

[0143] (1) When the first alarm device sounds an alarm but the second alarm device does not, it means that the water sample to be tested contains a certain amount of sulfate ions, but it should not be considered that there is a large amount of sulfate. The observation should be continued until the second alarm device sounds an alarm. If the second alarm device also sounds an alarm, it means that there is a large amount of sulfate ions in the water sample, and the railway sulfate erosion disease needs to be promptly rectified. (2) When the first alarm device does not sound an alarm but the second alarm device sounds an alarm, it is judged that BaSO4 precipitation has been generated, blocking the laser generator, causing the second alarm device to sound an alarm. Therefore, in this case, it is judged that the water sample contains sulfate ions, but has not yet reached the limit of the first alarm mode. It may be because the position of the generated BaSO4 precipitation just blocks the laser generator. Whether the water sample contains a large amount of sulfate ions still needs to be observed. If the first alarm device also sounds an alarm in the future, it can be determined that there is a large amount of sulfate ions in the water sample. It should be considered that the railway subgrade structure is facing the risk of sulfate erosion or sulfate erosion disease has occurred, and it should be rectified in time. (3) When the first alarm device and the second alarm device sound an alarm at the same time, it can be directly determined that a large amount of sulfate has entered the system, and the subgrade structure is facing the risk of sulfate erosion, and it should be dealt with.

Claims

1. An early warning system for railway subgrade sulfate attack based on ion electrodialysis, characterized by: It includes a closed detection box, an electric field generating device and a sulfate content detection device. The interior of the detection box is divided into a filtration chamber, a clean water chamber and a detection chamber from left to right. An electric hatch or filter is provided on the partition between the filter tank and the clean water tank for water to pass through, and at least one impurity filtration layer is provided between the filter tank and the clean water tank; an electrodialysis membrane is provided between the clean water tank and the detection tank to separate the two tank bodies, the cathode of the electric field generating device is located in the clean water tank, and the anode is located in the detection tank; The sulfate content detection device is used to detect the sulfate content in the detection chamber; the impurity filter layer is used to filter solid impurities, and the electrodialysis anion membrane is used to allow sulfate ions to selectively pass through under the action of the electric field and enter the detection chamber from the clean water chamber; the filter chamber is used to hold the water sample to be tested, and the detection chamber is used to hold Ba 2+ The water sample to be tested is filtered through the impurity filter layer and then enters the clean water tank. The sulfate ions in the clean water tank enter the detection tank through the electrodialysis anion membrane and react with Ba 2+ react; The sulfate content detection device includes one or a combination of the following structures: Structure 1: A current sensor is provided in the detection chamber, a signal output terminal of the current sensor is connected to a signal input terminal of a controller, and a signal output terminal of the controller is connected to a first alarm device; the controller is used to obtain the detection result of the current sensor and the voltage value of the electric field generating device; the electric field generating device is set to a constant current mode, and if the voltage of the electric field generating device reaches the voltage upper limit and the current value in the solution detected by the current sensor is lower than the set value, the controller controls the first alarm device to alarm; Structure 2: A laser emitting device is provided on one side of the detection chamber, and a laser receiving device is provided on the other side of the detection chamber. The output end of the laser receiving device is connected to a signal input end of the controller, and a signal output end of the controller is connected to the second alarm device. When the laser receiving device cannot receive the light emitted by the laser emitting device, the signal is transmitted to the controller, and the controller controls the second alarm device to alarm.

2. The railway subgrade sulfate attack early warning system based on ion electrodialysis according to claim 1, characterized in that: The solution in the detection chamber also contains hydrochloric acid or nitric acid, which is used to remove the influence of carbonate ions in the water sample to be tested.

3. The railway subgrade sulfate attack early warning system based on ion electrodialysis according to claim 1, characterized in that: The filter chamber is provided with a multi-stage impurity filter layer, which is a filter mesh or a filter membrane; the top of the filter chamber is also provided with an overflow port for overflowing excess water; A sewage outlet is provided at the bottom of the filter bin for discharging solid impurities; the height of the filter bin is higher than that of the clean water bin, and a filter screen is provided on the upper part of the partition between the filter bin and the clean water bin for water to pass through.

4. The railway subgrade sulfate attack early warning system based on ion electrodialysis according to claim 1, characterized in that: The electric door is connected to a controller, and the controller controls the electric door to open periodically; or, the electric door control terminal is connected to a timing output terminal of a timer, and the timer controls the electric door to open periodically.

5. The railway subgrade sulfate attack early warning system based on ion electrodialysis according to claim 1, characterized in that: The railway subgrade sulfate attack disease early warning system based on ion electrodialysis also includes a water pipe, the top of which is open and the cross-section of the water pipe is U-shaped or V-shaped; a water inlet is provided at the top of the filter chamber, and the water pipe is connected to the water inlet of the filter chamber to drain water gathered in the subgrade into the water pipe into the filter chamber.

6. A real-time monitoring method for railway subgrade sulfate erosion damage, characterized in that: Monitoring using the early warning system according to any one of claims 1 to 5 comprises the following steps: S1. Laying the monitoring system: drilling a channel from the bottom of the side of the railway roadbed to the inside of the roadbed, and placing the early warning system according to any one of claims 1 to 5 into the drilled channel; A water diversion channel is drilled obliquely downward on the side of the roadbed, a water pipe is placed in the water diversion channel, the end of the water diversion pipe is connected to the water inlet of the filter tank of the early warning system, and the water collected in the water diversion pipe is introduced into the filter tank; S2. Real-time monitoring: monitor the sulfate content in the detection chamber. When the sulfate content reaches the set threshold, it means that SO4 is detected in the water sample. 2- ions, sulfate attack is occurring in the roadbed or the roadbed will be affected by sulfate attack in the future.

7. The method for real-time monitoring of railway subgrade sulfate attack according to claim 6, characterized in that: In step S1, multiple water diversion channels arranged in the same straight line are drilled from top to bottom on the side of the roadbed. A water pipe is placed in each water diversion channel. The lower water pipe is longer than the upper water pipe and is used to collect water leaking from the top downward. The water collected from the upper, middle and lower parts of the roadbed converges in the lowest water pipe. The end of the lowest water pipe is connected to the water inlet of the filter chamber to introduce the collected water sample into the filter chamber.

8. The method for real-time monitoring of railway subgrade sulfate attack according to claim 6, characterized in that: In step S2, the method for determining whether the sulfate content reaches the threshold value is any one of the following two methods or a combination of the two: Method 1: S21, start the electric field generating device, set a constant current value I0 on the electric field generating device, and apply a voltage V0 to form an electric field on both sides of the electrodialysis anion membrane; S22, a current sensor detects a current value in the solution in the detection chamber; S23. When the current value is lower than the set value, the controller determines whether the voltage of the electric field generating device has reached the voltage upper limit. If so, step S24 is executed. If not, step S22 is returned to execution. S24. If the voltage of the electric field generating device reaches the upper voltage limit and the current value in the solution detected by the current sensor is lower than the set value, it is considered that the sulfate content has reached the threshold value, and the controller controls the first alarm device to sound an alarm; Method 2: The laser receiving device receives the light emitted by the laser emitting device. When the laser receiving device cannot receive the light emitted by the emitting device, it is considered that the sulfate content has reached a threshold value, and the second alarm device is controlled to alarm.

9. The method for real-time monitoring of railway subgrade sulfate attack according to claim 8, characterized in that: The judgment method of combining the two methods to determine whether the sulfate content has reached the threshold is as follows: when only one of the first alarm device and the second alarm device alarms and the other does not alarm, it indicates that a small amount of sulfate ions exists in the water sample; when the first alarm device and the second alarm device alarm successively or simultaneously, it is judged that the water sample to be tested contains a large amount of sulfate ions, the railway subgrade structure faces the risk of sulfate erosion or sulfate erosion disease has occurred, and timely remediation should be carried out.

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