Early warning system and method for railway bed sulfate erosion disease based on ion electrodialysis

Abstract

The invention discloses a railway roadbed sulfate erosion disease early warning system and method based on ion electrodialysis. The system comprises a closed detection box, an electric field generation device and a sulfate content detection device, and the interior of the detection box is sequentially divided into a filtering bin, a clear water bin and a detection bin from left to right; at least one stage of impurity filtering layer is arranged between the filtering bin and the clear water bin; an electrodialysis anion membrane is arranged between the clear water bin and the detection bin to separate the two bin bodies, a cathode of the electric field generation device is positioned in the clear water bin, and an anode is positioned in the detection bin; the sulfate content detection device is used for detecting the sulfate content in the detection bin; the electrodialysis anion membrane is used for allowing sulfate ions to selectively pass through under the action of an electric field and enter the detection bin from the clear water bin; the filter bin is used for containing a water sample to be detected, the detection bin is used for containing a Ba < 2 + > solution, the water sample to be detected enters the clear water bin after being filtered by the impurity filter layer, and sulfate ions in the clear water bin enter the detection bin to react with Ba < 2 + >.

Description

Technical Field

[0001] The 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 disease based on ion electrodialysis. Background Art

[0002] Railway subgrade transition sections are sections that require special treatment when connecting subgrades and structures, such as transition areas at the junctions of embankments and bridge abutments, embankments and transverse structures, embankments and cuttings, cuttings and tunnels. Setting up transition sections can gradually change the stiffness of the track, thereby reducing the vibration of trains and lines, slowing down the deformation of subgrade structures, and ensuring safe, stable and comfortable operation of trains. Railway subgrade transition sections are usually constructed using cement graded crushed stone, which is prepared by dry mixing cement and graded crushed stone that meet the requirements of the specifications and then adding water to mix. They mainly play a role in stiffness transition between different sections (bridges, tunnels, and roads), and are an important guarantee for the smooth operation of trains.

[0003] In recent years, the problem of high-speed railway embankment arching deformation has become very prominent, especially the arching problem of embankment transition section due to sulfate erosion has become increasingly serious. 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 in the preparation of cement-graded crushed stone, thereby directly introducing a large amount of sulfate into the cement-graded crushed stone material. The sulfate further reacts with the cement in the cement-graded crushed stone 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 embankment 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 products in the cement-graded gravel to produce expansive substances, mainly ettringite, which causes volume expansion and eventually leads to the arching of the roadbed.

[0004] The arching disease caused by sulfate erosion is characterized by hidden location, slow development and irreversible reaction, making it a railway roadbed durability disease that cannot be predicted in advance and extremely difficult to treat afterwards. High-speed rail has very strict requirements on the amount of arch deformation of the roadbed, which is difficult to distinguish directly with the naked eye. Usually, the railcar running on the rail detects the deformation of the track surface, and then comprehensively judges that it is caused by a reaction inside the roadbed. Then, the sampling is sent to the laboratory for testing through on-site drilling to verify that the sulfate content exceeds the standard, and finally it is determined that the roadbed arching is caused by sulfate erosion. At present, the test method for sulfate erosion is only to observe the arching deformation on site first, then drill and sample on site and send it to the laboratory for testing to verify whether the sulfate content exceeds the standard, and finally determine whether the roadbed arching is caused by sulfate erosion. Obviously, this detection method can only be implemented after obvious arching deformation is found, that is, it is possible to determine whether sulfate erosion has occurred. When the chemical reaction of sulfate attack inside the roadbed has already occurred, but the swelling products have not yet accumulated enough to produce obvious macroscopic deformation, there is no early warning. However, when obvious and detectable arch deformation occurs, the disease is already very serious, and it may be necessary to make a difficult decision to slow down or stop the high-speed rail, which seriously threatens the safety and stable operation of the high-speed rail. In addition, this method is time-consuming, inefficient, and greatly affected by human factors. Therefore, it is urgent to develop a measurement method that can detect and prompt potential diseases in a timely manner in the early stage of the reaction, especially when the reaction conditions are met but have not yet reacted or have just reacted, which 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 provide an early warning system and method for railway roadbed sulfate erosion damage based on ion electrodialysis in view of the above problems.

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

[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 in sequence; 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 chamber bodies, 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 also 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 comprises one of the following structures or a combination of the two:

[0011] Structure 1: A current sensor is provided in the detection chamber, and a signal output end of the current sensor is connected to a signal input end of the controller, and a signal output end of the controller is connected to the 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 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 send the detection results obtained by the controller to the host computer. The wireless communication module can upload the detection results to the host computer through GPRS or the protocol of the LPWAN Internet of Things for manual viewing. The host computer can be a mobile phone, tablet or computer, and the monitoring personnel read the current through the host computer. The wireless communication module can be a ZigBee wireless communication 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, a multi-stage impurity filter layer is provided in the filter bin, and the impurity filter layer is a filter mesh or a filter membrane; an overflow port is also provided at the top of the filter bin for overflowing excess water; a sewage outlet is provided at the bottom of the filter bin for discharging solid impurities;

[0014] The height of the filter bin is higher than that of the clean water bin. A filter is arranged 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 and then passes through the filter into the clean water bin. When the early warning system is used at the railway subgrade site, it can enter the detection bin to trigger the 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 erosion disease 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 on the top of the filter bin, and the water pipe is connected to the water inlet of the filter bin to drain the water gathered in the subgrade into the water pipe into the filter bin.

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

[0018] S1. Laying the monitoring system: drilling a hole 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 hole;

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

[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 is occurring in the roadbed 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, and 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 to the bottom. 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 reaches the voltage upper limit, if it reaches the voltage upper limit, execute step S24, if it does not reach the voltage upper limit, return to execute step S22;

[0027] S24, 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, it is considered that the sulfate content reaches the threshold value, and the controller controls the first alarm device to 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 reaches the 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: when only one of the first alarm device and the second alarm device alarms and the other does not alarm, it means 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, and the railway subgrade structure faces the risk of sulfate erosion or sulfate erosion disease has occurred, and it should be rectified in time.

[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 with the railway damage and maintenance costs caused by sulfate erosion, the economic benefits of this method are significant. Placing the system of the present invention in the roadbed can monitor the sulfate erosion of the railway roadbed in real time. Compared with regular sampling and sending it to the laboratory for testing, on-site real-time monitoring greatly reduces labor costs and time costs.

[0035] 4. Safety: Sulfate erosion may lead to instability of the railway subgrade, thus affecting the safe operation of trains. Through timely detection, this risk can be effectively reduced, the safety of railway transportation can be guaranteed, and the implementation process of this method is harmless to the railway subgrade.

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

[0037] Figure 1 It 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 It is a schematic diagram of the structure of the early warning system for railway roadbed sulfate attack disease of the present invention in a certain embodiment.

[0040] Figure 4 It is a schematic diagram of the structure of the early warning system for railway roadbed sulfate attack disease of the present invention in a certain embodiment.

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

[0042] Figure 6 It is a schematic diagram of the control flow of the early warning system for railway roadbed sulfate erosion in a certain embodiment of the present invention.

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

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

[0045] Detection box 1, impurity filtering 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 in conjunction with 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: The electrodialysis anion membrane realizes ion migration under the action of a 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 systems, 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 stabilized power supply (UNI-T, model UTP1605S) was used as an electric field generating device, the cathode of the electric field generating device was placed in water containing sulfate, and the anode of the electric field generating device was placed in a solution containing BaCl2. A DC stabilized power supply is an electronic device that can provide 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 is carried out in the laboratory.

[0055] Experimental device: laboratory H-type double-chamber electrolytic cell (sealed type) and DC regulated power supply are 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 1As shown in the figure, pour different solutions into the left and right chambers respectively. The DC stabilized power supply is used as an electric field generating device. Connect the power plug of the DC stabilized power supply to the AC socket, connect the alligator clip test line of the DC stabilized power supply to the electrode, and place 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 stabilized power supply.

[0057] According to the provisions of the "Railway Concrete Structure Durability Design Code" on the action level of chemical corrosion environment, 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 stage of the experiment

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

[0060] Principle: The sulfate ions in the left chamber pass through the electrodialysis anion membrane and enter the right chamber, where they react with BaCl2 to form BaSO4 precipitates. Since the BaSO4 precipitate is not conductive, it causes a change in the current.

[0061] Experimental Group-1

[0062] Test configuration: 200mg / L Na2SO4 solution in the left chamber, 0.2g / L BaCl2 solution + a large amount of 1mol / L HCl solution in the right chamber. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[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 current measured in the solution was low because of the low sulfate ion concentration. In actual application, when the sulfate ion concentration is low, a large amount of precipitation will not be produced, and the first alarm mechanism will not be activated. When enough precipitation accumulates after a long reaction time, the second alarm mechanism can 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] Test configuration: the left chamber is 1000mg / L Na2SO4 solution, the right chamber is 0.2g / L BaCl2 solution + a large amount of 1mol / L HCl solution. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[0069] The results are shown in Table 2. The sulfate ions in the left chamber passed through the electrodialysis anion membrane and reacted with the BaCl2 in the right chamber for precipitation. Under the constant current mode, the current dropped 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] Test configuration: 4000mg / L Na2SO4 solution in the left chamber, 0.2g / L BaCl2 solution + a large amount of 1mol / L HCl solution in the right chamber. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

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

[0075] Table 3

[0076]

[0077]

[0078] Experimental Group-4

[0079] Test configuration: the left chamber is 8000mg / L Na2SO4 solution, the right chamber is 0.2g / L BaCl2 solution + a large amount of 1mol / L HCl solution. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[0080] The results are shown in Table 4. The sulfate ions in the left chamber passed through the electrodialysis anion membrane and reacted with the BaCl2 in the right chamber for precipitation. Under the constant current mode, the current dropped 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] Purpose of the experiment: To verify whether the early warning system is effective in the presence of interfering ions (such as carbonate).

[0085] Principle: There may be other ions in the environment around the railway subgrade, such as carbonate ions. In this experiment, when there is an interfering ion carbonate, carbonate can pass through the electrodialysis anion membrane from the left chamber into the right chamber and react with BaCl2 to form BaCO3 precipitation. Since the right chamber contains HCl, HCl reacts with BaCO3 to dissolve the BaCO3 precipitation, avoiding the interference of BaCO3 precipitation on the current. The sulfate in the left chamber enters the right chamber and reacts with BaCl2 to form BaSO4 precipitation, which will not dissolve in HCl. Since the BaSO4 precipitation is not conductive, it will cause a change in the current.

[0086] Experimental Group-5

[0087] Test configuration: The solution in the left chamber contains Na2SO4 (1000mg / L) + Na2CO3 (4000mg / L), and the solution in the right chamber contains 0.2g / L BaCl2 solution + 1mol / L HCl solution. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[0088] The results are shown in Table 5. The sulfate ions in the left chamber passed through the electrodialysis anion membrane and reacted with the BaCl2 in the right chamber 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 in about 2 hours, at which time the second alarm mechanism will be activated.

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

[0090] Table 5

[0091]

[0092] Experimental Group-6

[0093] Test configuration: The left chamber is Na2SO4 (4000mg / L) + Na2CO3 (4000mg / L), and the right chamber is 0.2g / L BaCl2 solution + 1mol / L HCl solution. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[0094] The results are shown in Table 6. The sulfate ions in the left chamber passed through the electrodialysis anion membrane and reacted with the BaCl2 in the right chamber 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 in about 2 hours, which can activate the second alarm mechanism.

[0095] Table 6

[0096]

[0097] Experimental Group-7

[0098] Test configuration: The left chamber is Na2SO4 (10000mg / L) + Na2CO3 (4000mg / L), and the right chamber is 0.2g / L BaCl2 solution + 1mol / L HCl solution. The maximum voltage of the DC regulated power supply is 60V, and the set constant current value is 0.03A.

[0099] The results are shown in Table 7. The sulfate ions in the left chamber passed through the electrodialysis membrane and reacted with the BaCl2 in the right chamber to precipitate (see Table 7). Figure 2 ), no current drop occurs in the constant current mode, 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 precipitation begins to form obviously after about 1 hour, 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 generating device 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 to apply voltage V0 to form an electric field on both sides of the electrodialysis anion membrane. If BaSO4 precipitation is 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 precipitation, 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 resistance rise caused by the formation of precipitation and the current lower than the set value will not be restored by increasing the voltage. At this time, it is determined that a large amount of precipitation has been generated, and an alarm is triggered. The advantages of doing this are: first, the principle is simple, and the reaction amount of sulfate can be detected by electrical signals; second, the fault tolerance is high. Even if some trace precipitation is generated and the current decreases, 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, it can be ensured that the electric field loaded on both ends of the electrodialysis anion membrane is always at a large value, ensuring the efficiency of sulfate ions passing through the membrane with the help of the electric field, and will not cause the sulfate ions to pass through the membrane. The surface of the membrane will not be blocked by the generated precipitation, which will cause a significant decrease in the detection efficiency; because in the long-term monitoring process, other ions existing in nature enter the early warning system to generate a small amount of precipitation. The situation cannot be ruled out. After the generation, the voltage can be increased to compensate for the decrease in the passing efficiency caused by such precipitation blocking the electrodialysis anion membrane (the physical meaning of the consistent current is that the total amount of ion 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 early warning system for railway roadbed sulfate erosion disease based on ion electrodialysis of the present invention is mainly composed of a closed detection box (insulating 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 in sequence; 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 also added to the detection chamber to remove the influence of carbonate ions contained in the water sample on the detection results. Carbonate may or may not exist in the railway subgrade. For the detection of sections where carbonate is 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 the carbonate entering the detection chamber is dissolved by the 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 judge whether the water sample to be tested contains sulfate by the change of the solution current. Preferably, the current detection device and the electric field generating device are integrated devices, and a DC regulated power supply can be used.

[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 provided in the detection chamber, such as Figure 7As shown, a signal output end of the current sensor is connected to a signal input end of the controller, and a signal output end of the controller is connected to the 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. 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 send the detection result obtained by the controller to the host computer. The wireless communication module can upload the detection result to the host computer through GPRS or the protocol of the LPWAN Internet of Things for manual viewing. The host computer can be a mobile phone, tablet or computer, and the monitoring personnel read the current through the host computer. The wireless communication module can be a ZigBee wireless communication 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 bin is provided with a multi-stage impurity filter layer. Preferably, a secondary impurity filter layer is provided in the filter bin to divide the inside of the filter bin into three bins. The multi-stage filtration removes solid impurities. Heavier impurities such as particles and dust will be deposited preferentially at the bottom of each bin and will not clog the impurity filter layer, thereby preventing impurities from entering the clean water bin and the detection bin to affect the detection. The impurity filter layer is a filter screen or a filter membrane.

[0115] In some embodiments, Figure 4 As shown, the height of the filter bin is higher than that of the clean water bin, and a filter is arranged on the upper part of the partition between the filter bin and the clean water bin for water to pass through. Such arrangement facilitates the water in the filter bin to accumulate to a certain volume and reach a certain water pressure, and then enter the clean water bin through the filter after reaching the filter height. 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 bin, and the water pipe is connected to the water inlet of the filter bin to drain the water gathered in the water pipe from the roadbed into the filter bin.

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

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

[0121] The test chamber contains Ba with known concentration. 2+ Solution, the water sample to be tested enters the clean water tank after filtering out impurities from the filter tank. 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 tank 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 chamber and meet Ba 2+ The reaction generates BaSO4 precipitate. There are two ways to determine whether there is SO4 2- Enter the inspection chamber:

[0122] The first one: Since BaSO4 is not 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 determine 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 has 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 actual application, water samples are collected by drilling holes at railway subgrades where sulfate erosion is observed. Holes are drilled from the side of the subgrade to the inside of the subgrade, and then a water pipe is inserted for drainage. Water samples are collected at the end of the water pipe using a glass bottle. Alternatively, water samples are directly collected from the drainage ditch of the subgrade, which can also reflect the sulfate erosion situation to a certain extent. The collected water samples are sent to the laboratory and tested using the monitoring system of the present invention.

[0128] Example 3 A real-time monitoring method for railway roadbed sulfate erosion

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

[0130] S1. Laying the monitoring system: drilling a hole 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 hole;

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

[0132] In order to improve the accuracy of reflecting the sulfate erosion situation inside the roadbed, multiple water diversion holes 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 hole. The lower water pipe is longer than the upper water pipe and is used to collect water leaking from the top to the bottom. 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 samples 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 is occurring in the roadbed 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 reaches the voltage upper limit, if it reaches the voltage upper limit, execute step S24, if it does not reach the voltage upper limit, return to execute step S22;

[0139] S24, 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, it is considered that the sulfate content reaches the threshold value, and the controller controls the first alarm device to 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 reaches the threshold value, and the second alarm device is controlled to alarm.

[0142] The method of combining the two methods to determine whether the sulfate content has reached the threshold is: when only one of the first alarm device and the second alarm device alarms, and the other does not alarm, it means that there is a small amount of sulfate in the water sample; when the first alarm device and the second alarm device alarm successively or alarm at the same time, it is judged that the water sample to be tested contains a large amount of sulfate, and the railway subgrade structure is facing the risk of sulfate erosion or sulfate erosion disease has occurred, and it should be rectified in time. 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. It should be observed until the second alarm device sounds an alarm; if the second alarm device also sounds an alarm later, it means that there is a large amount of sulfate ions in the water sample, and it is necessary to promptly treat the railway sulfate erosion disease. (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, and 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 promptly treated. (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, which should be treated.

Claims

1. An early warning system for railway subgrade sulfate attack based on ion electrodialysis, characterized in that: It includes a closed detection box, an electric field generating device and a sulfate content detecting device, wherein the interior of the detection box is sequentially divided into a filtering chamber, a clean water chamber and a detection chamber from left to right; An electric hatch or filter screen is provided on the partition between the filter bin and the clean water bin for water to pass through, and at least one level of impurity filtration layer is provided between the filter bin and the clean water bin; an electrodialysis anion membrane is provided between the clean water bin and the detection bin to separate the two bins, the cathode of the electric field generating device is located in the clean water bin, and the anode is located in the detection bin; The sulfate content detection 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 filtering 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+ A reaction occurs.

2. The early warning system for railway subgrade sulfate attack based on ion electrodialysis according to claim 1 is characterized by: 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; 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 early warning system for railway subgrade sulfate attack based on ion electrodialysis according to claim 1 is characterized by: The sulfate content detection device comprises one of the following structures or a combination of the two: Structure 1: A current sensor is arranged in the detection chamber, a signal output end of the current sensor is connected to a signal input end of the controller, and a signal output end of the controller is connected to the 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.

4. The early warning system for railway subgrade sulfate attack based on ion electrodialysis according to claim 1 is characterized by: The filter bin is provided with a multi-stage impurity filter layer, the impurity filter layer is a filter screen or a filter membrane; the top of the filter bin 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.

5. The early warning system for railway subgrade sulfate attack based on ion electrodialysis according to claim 1 is characterized by: 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.

6. The early warning system for railway subgrade sulfate attack based on ion electrodialysis according to claim 1, characterized in that: The early warning system for railway roadbed sulfate erosion disease 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 on the top of the filter bin, and the water pipe is connected to the water inlet of the filter bin to drain the water gathered in the roadbed into the water pipe into the filter bin.

7. A real-time monitoring method for railway roadbed sulfate erosion damage, characterized in that: Monitoring using the early warning system according to any one of claims 1 to 6 comprises the following steps: S1. Laying the monitoring system: drilling a hole 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 hole; A water diversion channel is drilled obliquely downward on the side of the roadbed, a water guide pipe is placed in the water diversion channel, the end of the water guide pipe is connected to the water inlet of the filter bin of the early warning system, and the water collected in the water guide pipe is introduced into the filter bin; 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 will be affected by sulfate attack in the future.

8. The real-time monitoring method for railway roadbed sulfate attack according to claim 7, 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, and 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 to the bottom. 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.

9. The real-time monitoring method for railway roadbed sulfate attack according to claim 7, 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 reaches the voltage upper limit, if it reaches the voltage upper limit, execute step S24, if it does not reach the voltage upper limit, return to execute step S22; S24, 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, it is considered that the sulfate content reaches the threshold value, and the controller controls the first alarm device to 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 reaches the threshold value, and the second alarm device is controlled to alarm.

10. The real-time monitoring method for railway roadbed sulfate attack according to claim 9, characterized in that: The judgment method of combining the two methods to determine whether the sulfate content has reached the threshold is: when only one of the first alarm device and the second alarm device alarms and the other does not alarm, it means 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, and the railway subgrade structure faces the risk of sulfate erosion or sulfate erosion disease has occurred, and it should be rectified in time.

Images