Tunnel construction intelligent ventilation control system and method

Abstract

The present application relates to a kind of tunnel construction intelligent ventilation control system and method, belong to tunnel construction ventilation technical field.The technology aims at solving the problems of existing ventilation control method response lag, regulation extensive and high energy consumption.Control system mainly uses controller to connect respectively adjustable speed ventilating fan, first carbon monoxide sensor group arranged at 30-50m from tunnel working face, second carbon monoxide sensor group arranged at 50-100m and wind speed sensor installed in the outlet of ventilation duct;When the concentration monitored by first sensor group exceeds threshold value, controller first commands fan to run at maximum speed for first preset time, then according to the concentration change gradient obtained by second sensor group and the current air supply wind speed of wind speed sensor, the required air volume is calculated, and finally the fan is stably controlled to run at 60%-90% of rated maximum speed.The system is mainly used to realize safe, efficient and energy-saving intelligent ventilation control in the process of tunnel construction.

Description

Technical Field

[0001] This invention relates to the field of tunnel ventilation technology. More specifically, this invention relates to an intelligent ventilation control system for tunnel construction. Background Technology

[0002] During tunnel construction, processes such as drilling, blasting, and muck removal generate pollutants such as carbon monoxide. If these pollutants are not promptly removed through the ventilation system, their concentration inside the tunnel can easily exceed standards, threatening the health and safety of construction workers. Therefore, the ventilation system is a crucial supporting facility for tunnel construction. Currently, commonly used tunnel ventilation systems and control methods still have many problems in practical applications, making it difficult to meet the demands of intelligent and efficient construction.

[0003] First, the existing ventilation systems suffer from insufficient accuracy and timeliness in pollutant monitoring. Most systems deploy carbon monoxide sensors only at a single location inside the tunnel, or the sensors are positioned too far from the working face (e.g., exceeding 100m), failing to accurately capture concentration changes in the core pollution area within 30-50m of the working face—this area represents the initial diffusion range of pollutants after generation, exhibiting the highest concentration and directly impacting the working environment of construction workers. Single or remote sensor placements are prone to concentration monitoring lags, leading to delayed emergency ventilation by fans and increasing the risk of pollutant exceedances. Simultaneously, some systems lack wind speed monitoring devices, making it impossible to monitor the airflow efficiency at the ventilation duct outlets in real time. Even if excessive concentrations are detected, it's difficult to determine whether the current airflow is sufficient to effectively dilute the pollutants, further reducing the accuracy of ventilation control.

[0004] Secondly, the existing systems' airflow regulation methods are rather crude, resulting in energy waste and equipment wear and tear. Traditional ventilation systems often employ a control logic of fixed-speed operation or running at full speed to the end. If operating at a fixed speed for an extended period, when the concentration of pollutants inside the tunnel suddenly increases (such as after blasting), the fixed airflow cannot quickly reduce the concentration, easily leading to safety hazards. If operating at the rated maximum speed regardless of the pollutant concentration, continuing to operate at high speed during processes with lower pollutant concentrations (such as support work) or after the concentration has dropped to a safe range will result in significant energy waste. Furthermore, prolonged full-load operation of the fans can easily lead to bearing wear, motor overheating, and shortened equipment lifespan. Some systems that attempt to dynamically adjust airflow also suffer from poor regulation because they lack a scientific basis for airflow calculation and rely solely on manual experience to adjust the speed. This fails to accurately match the required airflow based on the pollutant diffusion trend and the actual supply air velocity.

[0005] Finally, existing systems have a low level of automation, rely on manual intervention, and have limited applicability. Most ventilation systems require staff to periodically enter the tunnel to read sensor data and manually adjust fan speeds, which not only increases the labor intensity of manual inspections but also raises personnel safety risks in long-distance (e.g., over 1000m) or high-risk (e.g., high-dust) tunnels. Furthermore, manual adjustments suffer from response lag—when the concentration inside the tunnel suddenly exceeds the standard, it typically takes 5-10 minutes from the moment the abnormal concentration is detected to the adjustment of the fan speed, during which time pollutants may continue to spread. Moreover, human experience is difficult to adapt to the pollution characteristics of different types of tunnels (e.g., highway and water conservancy tunnels) or different construction procedures, resulting in limited applicability of the same ventilation system in different scenarios. Parameters need to be readjusted for specific working conditions, increasing construction costs and operational complexity. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] Another objective of this invention is to provide an intelligent ventilation control system for tunnel construction. Through multi-layered precise monitoring and rapid emergency response, it can detect the risk of excessive carbon monoxide concentration in advance and quickly reduce the concentration to ensure the safety of construction personnel and comply with industry standards. It adopts a stepped control logic to dynamically adapt the air volume to avoid rough operation of fans, reduce energy consumption and extend equipment life. It realizes full automation of ventilation control process to reduce the risk and labor intensity of manual inspection, improve the timeliness and reliability of response and reduce the probability of safety accidents caused by human operation errors. It can also flexibly adapt to different types of tunnels and construction procedures. Moreover, the core components are standardized products with strong versatility, low procurement and maintenance costs, and facilitate the transformation, upgrading and promotion of existing systems and technology.

[0008] To achieve these objectives and other advantages according to the present invention, an intelligent ventilation control system for live tunnel construction is provided, comprising: a controller, a ventilation fan with adjustable speed, a first carbon monoxide sensor group, a second carbon monoxide sensor group, and a wind speed sensor, wherein the controller is communicatively connected to the ventilation fan, the first carbon monoxide sensor group, the second carbon monoxide sensor group, and the wind speed sensor, respectively. The ventilation fan is used to force fresh air into the tunnel working face through the ventilation duct. The first carbon monoxide sensor group is arranged within a range of 30-50m from the tunnel working face, and the second carbon monoxide sensor group is arranged within a range of 50-100m from the tunnel working face. The wind speed sensor is arranged at the outlet of the ventilation duct. The controller is configured to perform the following operations: When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds a preset first concentration threshold, a first control command is generated, which commands the ventilation fan to run at its rated maximum speed for a first preset duration. After the first preset duration ends, the carbon monoxide concentration data detected by the second carbon monoxide sensor group is acquired, and the carbon monoxide concentration change gradient at the location of the second carbon monoxide sensor group is calculated. At the same time, the current air supply speed detected by the wind speed sensor is acquired. Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated through a preset control model, and a second control command is generated. The second control command commands the ventilation fan to adjust to a stable speed, which is 60%-90% of the rated maximum speed of the ventilation fan.

[0009] Preferably, both the first carbon monoxide sensor group and the second carbon monoxide sensor group are multi-parameter gas sensor groups used to simultaneously monitor carbon monoxide concentration and nitrogen oxide concentration; the controller is further configured to perform the following operations: Based on the data monitored by the multi-parameter gas sensor group, the concentration change gradient G of carbon monoxide is calculated respectively. co and the concentration gradient G of nitrogen oxides nox ; G co With the first gradient threshold G coT Compare and put G nox With the second gradient threshold G noxT The comparison is made, wherein the first gradient threshold G coT Less than the second gradient threshold G noxT ; When G co ≥G coT And G nox <G noxT At that time, carbon monoxide was determined to be the dominant pollutant, and the required air volume was calculated using the first control model; When G nox ≥G noxT And G co <G coT When nitrogen oxides are identified as the dominant pollutant, a second control model is used to calculate the required air volume. This second control model is configured such that, for the same concentration change gradient input value, the required air volume calculated by it is 15%-25% higher than the required air volume calculated by the first control model. When G co ≥G coT And G nox ≥G noxTWhen the pollution is determined to be a complex pollution state, the larger value between the calculation results of the first control model and the second control model is selected as the final required air volume.

[0010] Preferably, the controller is further configured to perform the following operations: while generating the first control command that commands the ventilation fan to operate at its rated maximum speed, a timer is started; Based on the initial carbon monoxide concentration value C1 when the first control command is generated, the corresponding maximum allowable continuous running time T1 is calculated through a preset duration calculation model, where the larger the value of C1, the smaller the value of T1. While the ventilation fan is operating at its rated maximum speed, the current carbon monoxide concentration (C2) is monitored in real time. When the continuous running time of the ventilation fan reaches the first preset duration and C2 drops below the second concentration threshold, wherein the second concentration threshold is 40%-60% of the first concentration threshold, the controller generates a delay control command. The delay control command instructs the ventilation fan to continue operating at the rated maximum speed for a delay time T2, where T2 = k × T1, k is a coefficient and its value ranges from 0.1 to 0.3; After T2 ends, the controller then performs the operations of acquiring data from the second carbon monoxide sensor group, calculating the concentration change gradient, and generating the second control command.

[0011] Preferably, the controller is further configured to perform the following operations: Real-time monitoring of the output signal status of the first carbon monoxide sensor group and the second carbon monoxide sensor group; When the output signal of the first carbon monoxide sensor group or the second carbon monoxide sensor group is continuously abnormal, it is determined that a sensor malfunction has occurred. The abnormal output signal includes signal loss and exceeding the preset range of the sensor. When a sensor malfunction is detected, the controller generates a fault control command; the fault control command instructs the ventilation fan to run continuously at a fixed speed of 70%-80% of its rated maximum speed; at the same time as generating the fault control command, the controller starts a fault timer; when the fault timer reaches the preset fault handling duration, the controller automatically attempts to restore the normal intelligent ventilation control logic.

[0012] Preferably, the controller is communicatively connected to a construction plan input device; the controller is further configured to perform the following operations: The construction plan input device obtains information on current or upcoming construction procedures, including drilling, blasting, slag removal, and support. Based on the construction procedure information, the corresponding baseline ventilation configuration is retrieved from the preset procedure-ventilation strategy mapping table; wherein, the baseline ventilation configuration corresponding to the blasting procedure is to set the first concentration threshold to a first value and adjust the setting range of the stable speed of the ventilation fan to 80%-90% of the rated maximum speed; the baseline ventilation configuration corresponding to the slag removal procedure is to set the first concentration threshold to a second value and adjust the setting range of the stable speed of the ventilation fan to 60%-70% of the rated maximum speed, wherein the first value is less than the second value; Simultaneously with initiating the construction process, the controller loads the corresponding baseline ventilation configuration and performs corresponding control operations based on this configuration.

[0013] Preferably, the controller is further configured to perform the following operations: When the ventilation fan runs continuously at the stable speed for a duration exceeding the first duration threshold, and during this period the concentration value monitored by the first carbon monoxide sensor group remains below the third concentration threshold, a low-power operation mode is activated. The low-power operation mode controls the ventilation fan to operate alternately within a preset working cycle; wherein, each working cycle includes a running segment and a stopping segment, the length of the running segment is set to 1.5-2.5 times the length of the stopping segment, and the speed of the ventilation fan during the running segment is set to 40%-50% of the rated maximum speed.

[0014] Preferably, the controller is further configured to perform the following operations: During the period when the ventilation fan runs continuously at the stable speed for more than the second duration threshold, monitoring data from the first carbon monoxide sensor group and the second carbon monoxide sensor group are continuously acquired. Calculate the average difference ΔC between the readings of the first carbon monoxide sensor group and the readings of the second carbon monoxide sensor group; when the absolute value of the average difference ΔC continuously exceeds a preset difference threshold ΔC... T When the time comes, a sensor calibration prompt signal is generated; the sensor calibration prompt signal contains indication information that the first carbon monoxide sensor group or the second carbon monoxide sensor group needs to be calibrated.

[0015] This invention also discloses a method for intelligent ventilation control in tunnel construction based on the aforementioned intelligent ventilation control system, characterized by comprising the following steps: The carbon monoxide concentration within a range of 30-50m from the tunnel working face is monitored using the first carbon monoxide sensor group. The carbon monoxide concentration within a range of 50-100m from the tunnel working face is monitored using a second carbon monoxide sensor group. The airflow velocity at the outlet of the ventilation duct is monitored using a wind speed sensor. When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds the preset first concentration threshold, the ventilation fan is controlled to run at the rated maximum speed for a first preset time. After the first preset time period ends, the carbon monoxide concentration data monitored by the second carbon monoxide sensor group is acquired, and the gradient of carbon monoxide concentration change at the location of the second carbon monoxide sensor group is calculated. Simultaneously, the current supply air speed monitored by the wind speed sensor is acquired; Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated using a preset control model, and the ventilation fan is controlled to operate at a stable speed between 60% and 90% of its rated maximum speed.

[0016] The present invention has at least the following beneficial effects: First, through multi-layered precise monitoring and rapid emergency response, the risk of carbon monoxide concentration exceeding the standard can be detected in advance and the concentration can be quickly reduced, effectively ensuring the safety of tunnel construction personnel and meeting the relevant industry safety standards.

[0017] Secondly, a stepped control logic is adopted to dynamically adapt the air volume, avoiding rough operation of the fan, significantly reducing energy consumption, and extending the service life of the ventilation equipment.

[0018] Third, it achieves full automation of ventilation control, reduces the risks and labor intensity of manual inspections, improves the timeliness and reliability of ventilation response, and reduces the probability of safety accidents caused by human error.

[0019] Fourth, it is flexible and adaptable to different types of tunnels and construction procedures, and its core components are standardized products with strong versatility, low procurement and maintenance costs, and facilitate the transformation, upgrading and promotion of existing systems and technologies.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the technical solutions, so that those skilled in the art can implement it based on the description.

[0022] This invention discloses an intelligent ventilation control system for tunnel construction, including a controller, a ventilation fan with adjustable speed, a first carbon monoxide sensor group, a second carbon monoxide sensor group, and a wind speed sensor. The controller is communicatively connected to the ventilation fan, the first carbon monoxide sensor group, the second carbon monoxide sensor group, and the wind speed sensor. The ventilation fan is used to force fresh air into the tunnel working face through the ventilation duct. The first carbon monoxide sensor group is arranged within a range of 30-50m from the tunnel working face, and the second carbon monoxide sensor group is arranged within a range of 50-100m from the tunnel working face. The wind speed sensor is arranged at the outlet of the ventilation duct. The controller is configured to perform the following operations: When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds a preset first concentration threshold, a first control command is generated, which commands the ventilation fan to run at its rated maximum speed for a first preset duration. After the first preset duration ends, the carbon monoxide concentration data detected by the second carbon monoxide sensor group is acquired, and the carbon monoxide concentration change gradient at the location of the second carbon monoxide sensor group is calculated. At the same time, the current air supply speed detected by the wind speed sensor is acquired. Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated through a preset control model, and a second control command is generated. The second control command commands the ventilation fan to adjust to a stable speed, which is 60%-90% of the rated maximum speed of the ventilation fan.

[0023] In the above technical solution, the intelligent ventilation control system for tunnel construction can use an industrial-grade PLC controller. This controller must have at least 8 analog input interfaces (for receiving sensor signals) and 2 analog output interfaces (for controlling fan speed), and support the Modbus communication protocol. The ventilation fan can be a variable frequency centrifugal ventilation fan, and its rated air volume must match the tunnel cross-sectional area (e.g., cross-sectional area 10-20m²). 2 For tunnels, a rated air volume of 2000-4000m³ / h can be selected. 3 The fan has a speed of 0-50Hz and a variable frequency speed regulation range. The first and second carbon monoxide sensor groups can be equipped with electrochemical carbon monoxide sensors, with a measurement range of 0-100ppm, an accuracy of ±2ppm (within the range of 0-50ppm), and a response time of ≤30 seconds; the wind speed sensor can be a pipeline wind speed transmitter, with a measurement range of 0-20m / s, an output of 4-20mA analog signal, and an accuracy of ±0.1m / s. These devices are all readily available products on the market.

[0024] During assembly, the ventilation fan is installed on a flat concrete foundation outside the tunnel entrance, with a foundation flatness error not exceeding ±5mm. The fan and foundation are connected by rubber shock-absorbing pads to reduce vibration. One end of the ventilation duct is sealed to the fan outlet via a flange, with oil-resistant rubber gaskets installed between the flanges. The duct is laid along the top or sidewall of the tunnel, with a duct support installed every 10m. The support is fixed to the tunnel wall with expansion bolts, and the horizontal distance between the duct outlet and the tunnel working face does not exceed 5m. The first carbon monoxide sensor group is evenly distributed at three locations 35m, 40m, and 45m away from the tunnel working face. The sensor at each location is fixed to the tunnel sidewall by an L-shaped angle steel bracket, with the bottom of the bracket 1.5m above the ground. The sensor probe faces the tunnel working face to avoid collision with construction equipment. The second carbon monoxide sensor group is evenly distributed at three locations 60m, 75m, and 90m from the tunnel working face, installed in the same manner as the first sensor group, and at the same height on the tunnel sidewall. The wind speed sensor is installed inside the ventilation duct outlet at its center via a dedicated flange, which is welded to the duct. The sensor probe axis is aligned with the airflow direction within the duct. The controller is installed in the distribution box at the tunnel entrance, which is fixed to a steel structure support next to the ventilation fan at a height of 1.2m. All sensors are connected via RVVP 2×1.0mm. 2 The shielded cable connects to the analog input interface of the controller, and the frequency converter of the ventilation fan is connected via RVV 3×2.5mm. 2 The cables are connected to the analog output interface of the controller. All cables are protected by galvanized steel pipes, which are fixed along the tunnel rock wall.

[0025] Before the system is officially put into operation, parameter presets and control model calibrations must be completed: the first concentration threshold in the controller is set to 24 ppm, which is determined with reference to the safe limit of carbon monoxide concentration in the tunnel construction environment in the "Coal Mine Safety Regulations"; the first preset duration is set to 30 minutes, based on the conventional purification cycle of pollutant diffusion after a single blast in tunnel construction, and verified by multiple sets of tunnel ventilation experiments; the stable speed range is set to 60%-90% of the rated maximum speed of the ventilation fan, where "rated maximum speed" is defined as the rated speed marked on the ventilation fan product nameplate, that is, the optimal operating speed under the fan's design conditions. For example, if the rated speed marked on the nameplate of a certain model of variable frequency centrifugal fan is 1450 r / min, then the rated maximum speed of the fan is calculated as 1450 r / min, and the stable speed needs to be controlled between 870-1305 r / min.

[0026] The preset control model uses a linear regression model, with the model expression Q=K×G×V, where Q is the required air volume (unit: m³ / s). 3 / h), G is the gradient of carbon monoxide concentration over time at the location of the second carbon monoxide sensor group (unit: ppm / min), V is the current supply wind speed monitored by the wind speed sensor (unit: m / s), and K is the correction coefficient, with a value ranging from 120 to 150, the specific value of which is determined based on the tunnel cross-sectional area, which is 10-15m². 2 K is set to 120, 15-20m 2 K is set to 135, 20-25m 2 When K is set to 150, this coefficient is obtained by fitting more than three ventilation experiments in tunnels of the same cross-sectional type. The experimental method is as follows: a known amount of carbon monoxide (e.g., 500 ppm) is released at the working face of the tunnel, the ventilation fan is started, the concentration data and wind speed data of the second sensor group are recorded every 1 minute, and the actual air volume is measured at the same time. The correspondence between "air volume-gradient-wind speed" is fitted by the least squares method, and finally the K value under different cross-sectional areas is determined.

[0027] The method for calculating the concentration gradient over time is as follows: Starting from the end of the first preset time period, continuously collect concentration data from the second carbon monoxide sensor group for 10 minutes, with a sampling frequency of 1 minute / time, acquiring a total of 10 concentration data points (denoted as C0, C1, C2...C9, unit: ppm, C0 is the starting point concentration, C9 is the concentration at the 10th minute); First, abnormal data are removed. If a data point exceeds the sensor's range (0-100ppm), or the difference between it and two adjacent data points exceeds 5ppm (e.g., the difference between C3 and C2 is 6ppm, and the difference between C3 and C4 is 7ppm), then the data point is determined to be an abnormal value, and is replaced by the average of the two preceding and following normal data points (e.g., replacing C3 with (C2+C4) / 2). If the number of abnormal data points exceeds 3, then collect data again for 10 minutes; After processing the abnormal data, calculate the concentration gradient over time G using a linear regression formula, the formula being G=(nΣt i C i -Σt i ΣC i ) / (nΣt i 2 -(Σt i ) 2 ), where n=10 (number of data points), t iFor the data collection time points (unit: min, t0=0, T1=1, ..., t9=9), if the calculated G value is positive, it indicates that the concentration increases over time, and the absolute value is substituted into the control model; if it is negative, it indicates that the concentration decreases over time, and the value is directly substituted into the model. Simultaneously, an effective judgment criterion for the concentration change gradient is set: when the absolute value of the calculated G value is ≥0.3 ppm / min, it is determined that the pollutant concentration change trend is obvious, and airflow calculation and speed adjustment based on the control model need to be performed; when the absolute value of the G value is <0.3 ppm / min, it is determined that the pollutant concentration has stabilized, and the current fan speed is maintained unchanged.

[0028] During system operation, the first carbon monoxide sensor group monitors the carbon monoxide concentration within a range of 30-50m from the tunnel working face in real time. If the concentration value detected by any sensor exceeds 24ppm for 3 consecutive seconds (to avoid misjudgment due to instantaneous interference), the sensor transmits the concentration signal to the controller through a shielded cable. The controller immediately generates the first control command, instructing the ventilation fan to run at its rated maximum speed. After the first preset duration of 30 minutes, the controller automatically starts the concentration data acquisition program of the second sensor group, collecting concentration data for 10 minutes at a frequency of 1 minute / time. At the same time, it acquires the current supply air velocity V detected by the wind speed sensor (taking the average wind speed within 10 minutes to reduce the impact of instantaneous wind speed fluctuations). After anomaly processing of the collected concentration data, the controller calculates the concentration gradient G over time using a linear regression formula. If the absolute value of G is ≥0.3ppm / min, G and V are substituted into the preset control model Q=K×G×V to calculate the required air volume Q. Then, based on the "air volume-speed" curve provided by the ventilation fan manufacturer (e.g., an air volume of 2100m³ / min at a fan speed of 870r / min), the required air volume is calculated. 3 / h, 1015r / min at 2450m 3 3325m at 1305r / min / h 3 ( / h) Find the fan speed corresponding to the required air volume Q, and ensure that the speed is between 60% and 90% of the rated maximum speed. If the calculated speed exceeds this range, take the boundary value of the range (e.g., when the calculated speed is 850 r / min, take 870 r / min corresponding to 60%; when the calculated speed is 1350 r / min, take 1305 r / min corresponding to 90%). The controller generates a second control command to adjust the ventilation fan to operate at this stable speed. If the absolute value of G is <0.3 ppm / min, the controller does not execute the model calculation and maintains the current rated maximum speed of the ventilation fan until the end of the next 30-minute cycle, then restarts the data acquisition and gradient calculation process.

[0029] This technical solution has significant advantages over existing conventional tunnel ventilation systems (such as fixed-speed ventilation systems and ventilation systems relying solely on a single set of sensors). Existing fixed-speed ventilation systems operate at a constant speed regardless of pollutant concentration, easily leading to excessive energy consumption at low concentrations or insufficient ventilation at high concentrations. Systems relying solely on a single set of sensors cannot comprehensively grasp the pollutant diffusion trend and are prone to misjudgments due to sensor malfunctions. This solution, however, by clearly defining equipment parameters, material selection, assembly details, and core calculation logic, ensures that those skilled in the art can directly purchase the equipment and install and debug it as required, achieving a complete reproduction of the technical solution. The system employs a closed-loop control mechanism: "first sensor group triggers emergency ventilation → full-speed operation for a preset duration → second sensor group calculates the time gradient → dynamic speed adjustment based on the model." This allows for rapid activation of strong ventilation when pollutant concentrations exceed limits, ensuring the safety of construction personnel, and precise adjustment of airflow based on concentration changes over time, avoiding energy waste.

[0030] In another technical solution, both the first carbon monoxide sensor group and the second carbon monoxide sensor group are multi-parameter gas sensor groups used to simultaneously monitor carbon monoxide concentration and nitrogen oxide concentration; the controller is further configured to perform the following operations: Based on the data monitored by the multi-parameter gas sensor group, the concentration change gradient G of carbon monoxide is calculated respectively. co and the concentration gradient G of nitrogen oxides nox ; G co With the first gradient threshold G coT Compare and put G nox With the second gradient threshold G noxT The comparison is made, wherein the first gradient threshold G coT Less than the second gradient threshold G noxT ; When G co ≥G coT And G nox <G noxT At that time, carbon monoxide was determined to be the dominant pollutant, and the required air volume was calculated using the first control model; When G nox ≥G noxT And G co <G coT When nitrogen oxides are identified as the dominant pollutant, a second control model is used to calculate the required air volume. This second control model is configured such that, for the same concentration change gradient input value, the required air volume calculated by it is 15%-25% higher than the required air volume calculated by the first control model. When G co ≥G coT And Gnox ≥G noxT When the pollution is determined to be a complex pollution state, the larger value between the calculation results of the first control model and the second control model is selected as the final required air volume.

[0031] In the above technical solution, the intelligent ventilation control system for tunnel construction uses multi-parameter gas sensor groups for both the first and second carbon monoxide sensor groups. These sensor groups can simultaneously monitor carbon monoxide and nitrogen oxide concentrations. The carbon monoxide measurement range is set to 0-100ppm with an accuracy of ±2ppm (0-50ppm range), and the nitrogen oxide measurement range is set to 0-20ppm with an accuracy of ±0.5ppm (0-10ppm range). Both have a response time ≤30 seconds and support 4-20mA analog signal output. These are mature products readily available on the market. The controller still uses an industrial-grade PLC controller, requiring an additional two analog input interfaces to receive nitrogen oxide concentration signals, ensuring simultaneous acquisition of data for both pollutants. During assembly, the installation position and fixing method of the multi-parameter gas sensor group are the same as described above. That is, the first multi-parameter sensor group is arranged at 35m, 40m and 45m away from the tunnel working face, and the second multi-parameter sensor group is arranged at 60m, 75m and 90m. All of them are fixed at a height of 1.5m on the non-working side wall of the tunnel, with the sensor probe facing the working face to avoid construction interference.

[0032] Before the system runs, parameter presets and model calibration must be completed: preset the first gradient threshold G in the controller. coT The second gradient threshold G is 0.2 ppm / min. noxT 0.3 ppm / min (G coT Less than G noxT This value is determined based on the diffusion characteristics of two pollutants during tunnel construction: carbon monoxide diffuses slowly, requiring airflow adjustment even with a small gradient; nitrogen oxides diffuse quickly, requiring a higher gradient to trigger intervention. Verified by more than three tunnel experiments, this threshold effectively distinguishes the dominant pollutant type. A first and second control model are pre-set, both linear regression models with the basic form Q=K×G×V (Q is the required airflow, G is the pollutant concentration gradient over time, and V is the supply air velocity). The correction coefficient K for the first control model (corresponding to carbon monoxide as the dominant pollutant) is... co The value is 120-150 (consistent with the above, determined according to the tunnel cross-sectional area); the correction coefficient K for the second control model (corresponding to nitrogen oxide dominance) is... nox The value ranges from 138 to 187.5 (i.e., K). co The second model calculates 15%-25% higher air volume than the first model under the same gradient input, ensuring that the calculated air volume is 15%-25% higher than that of the first model, for example, in a cross-sectional area of ​​15m². 2 Time Kco =135, K nox The correction coefficients for both models were obtained through experimental fitting: known amounts of carbon monoxide (500 ppm) and nitrogen oxides (50 ppm) were released at the tunnel working face, and the actual air volume required to reduce the pollutant concentration to a safe value under different gradients and wind speeds was recorded. The K values ​​of the two models were fitted using the least squares method to ensure the accuracy of the model calculations.

[0033] When the system is working, the multi-parameter sensor group collects the carbon monoxide concentration (C) in real time. co ) and nitrogen oxide concentration (C nox The controller receives monitoring data from two sets of sensors every minute. When the first sensor set detects that the carbon monoxide concentration exceeds the first concentration threshold (24 ppm), it triggers the fan to run at its rated maximum speed for a first preset time (30 minutes). Then, the controller begins to calculate the concentration gradient of the two pollutants over time: first, it calculates the concentration gradient of the second sensor set over 10 minutes... co Data (C) co0 -C co9 ) and C nox Data (C) nox0 -C nox9 Process them separately and remove outliers (C values ​​that exceed the measurement range or have a difference of more than 5 ppm from adjacent data). co C exceeding 1 ppm nox Outliers are replaced with the average of the preceding and following normal data), and then the linear regression formula G = (nΣt) is applied. i C i -Σt i ΣC i ) / (nΣt i 2 -(Σt i ) 2 (n=10, t) i The gradient G of carbon monoxide concentration change was calculated for the period from 0 to 9 minutes. co and the gradient of nitrogen oxide concentration G nox .

[0034] The controller then will G co With G coT (0.2ppm / min), G nox With G noxT (0.3ppm / min) for comparison: If G co ≥0.2ppm / min and G nox <0.3ppm / min, determined to be carbon monoxide as the dominant pollutant, the first control model is invoked, and G is substituted. coCalculate the required air volume Q based on the current supply air velocity V (10-minute average wind speed). co If G nox ≥0.3ppm / min and G co <0.2ppm / min, determined to be nitrogen oxides as the dominant pollutant, the second control model is invoked, and G is substituted. nox Calculate the required air volume Q with V. nox If G co ≥0.2ppm / min and G nox ≥0.3ppm / min, is judged as a complex pollution state, compare Q co With Q nox The larger of the values ​​is selected as the final required air volume Q. 终 Finally, the controller determines the value based on Q. 终 Based on the fan's "airflow-speed" curve, determine the corresponding stable speed (still 60%-90% of the rated maximum speed), generate a second control command to adjust the fan operation, and if the calculated speed exceeds the range, take the boundary value (e.g., take 60% if it is below 60%, take 90% if it is above 90%).

[0035] Compared to ventilation systems that only monitor a single pollutant, this technical solution offers significant advantages: existing systems focus only on carbon monoxide, easily overlooking nitrogen oxides (which are more toxic, diffuse faster, and require higher airflow to exhaust), potentially leading to nitrogen oxide exceedances; while this solution uses a multi-parameter sensor array to simultaneously monitor two core pollutants, combines gradient thresholds to distinguish the dominant type, and then matches different control models to ensure targeted airflow adjustment—for example, when nitrogen oxides dominate, the airflow is 15%-25% higher than when carbon monoxide dominates, which can quickly dilute the highly diffusive nitrogen oxides; in cases of combined pollution, a larger airflow is used to avoid any pollutant residue.

[0036] In another technical solution, the controller is further configured to perform the following operations: while generating the first control command to command the ventilation fan to operate at its rated maximum speed, a timer is started; Based on the initial carbon monoxide concentration value C1 when the first control command is generated, the corresponding maximum allowable continuous running time T1 is calculated through a preset duration calculation model, where the larger the value of C1, the smaller the value of T1. While the ventilation fan is operating at its rated maximum speed, the current carbon monoxide concentration (C2) is monitored in real time. When the continuous running time of the ventilation fan reaches the first preset duration and C2 drops below the second concentration threshold, wherein the second concentration threshold is 40%-60% of the first concentration threshold, the controller generates a delay control command. The delay control command instructs the ventilation fan to continue operating at the rated maximum speed for a delay time T2, where T2 = k × T1, k is a coefficient and its value ranges from 0.1 to 0.3; After T2 ends, the controller then performs the operations of acquiring data from the second carbon monoxide sensor group, calculating the concentration change gradient, and generating the second control command.

[0037] In the above technical solution, the intelligent ventilation control system for tunnel construction still uses an industrial-grade PLC controller, requiring the integration of a timer module (supporting millisecond-level timing accuracy, achievable through the controller's built-in timer function, requiring no additional external hardware) to accurately record the duration of the ventilation fan's operation at its rated maximum speed. The first and second carbon monoxide sensor groups utilize the aforementioned multi-parameter gas sensor groups to ensure simultaneous monitoring of carbon monoxide and nitrogen oxide concentrations. Their installation locations, fixing methods, and equipment parameters (measurement range, accuracy, response time) are consistent with the previous methods. Specifically, the first sensor group is positioned at 35m, 40m, and 45m from the tunnel working face, and the second sensor group is positioned at 60m, 75m, and 90m, fixed at a height of 1.5m on the non-working sidewall of the tunnel, with an IP65 protection rating to adapt to the tunnel environment. The selection and assembly requirements for ventilation fans, wind speed sensors, and ventilation ducts are also consistent with the previous methods, ensuring system component compatibility and operational stability.

[0038] Before the system runs, parameter presets and duration calculation model calibration must be completed: First, it is clear that the first concentration threshold is still 24 ppm, and the second concentration threshold is set to 50% of the first concentration threshold, i.e., 12 ppm (the value range is 40%-60%, and 50% is the middle value. After verification by multiple tunnel experiments, this value can effectively determine whether the pollutants have dropped to a low level and avoid premature adjustment of the rotation speed, which may cause the concentration to rebound). The preset duration calculation model is a linear correlation model, and its expression is T1=(C max -C1)×Kt, where T1 is the maximum permissible continuous operating time (in minutes), C1 is the initial carbon monoxide concentration value when the first control command is generated (in ppm, the average value of the monitoring values ​​of the three points of the first sensor group), C max The limit safe concentration of carbon monoxide in the tunnel construction environment is set at 50 ppm (referencing industry safety standards), and Kt is the duration factor (valued at 0.8-1.2, with a tunnel cross-sectional area of ​​10-15 m²). 2 When Kt=0.8, 15-20m 2 When Kt=1.0, 20-25m 2When Kt=1.2, this coefficient was determined through experiments: different concentrations of carbon monoxide were released in tunnels with different cross-sections, and the longest time it took for the fan to run at full speed until the concentration dropped to a safe value was recorded. The correlation between C1 and T1 was obtained by fitting the data. At the same time, the delay time coefficient k was set to 0.2 (the value range is 0.1-0.3, with 0.2 being the middle value, taking into account both the pollutant removal effect and energy consumption control. Experiments show that this value can ensure the continuous decrease of concentration while avoiding excessively prolonging the full-speed operation time). The first preset time was still 30 minutes.

[0039] When the system is operating, if the average carbon monoxide concentration (data from 3 points) detected by the first sensor group exceeds 24 ppm for 3 consecutive seconds, the controller generates a first control command (commanding the ventilation fan to run at its rated maximum speed) and simultaneously starts the timer module to record the fan's full-speed operation time. At the same time as starting the first control command, the controller reads the average carbon monoxide concentration of the first sensor group as the initial concentration value C1, and substitutes it into the duration calculation model T1=(50-C1)×Kt to calculate the corresponding maximum allowable continuous operating time T1 (for example, when C1=35ppm and Kt=1.0, T1=(50-35)×1.0=15 minutes; when C1=40ppm and Kt=1.0, T1=(50-40)×1.0=10 minutes, reflecting the logic that the larger C1 is, the smaller T1 is). During the period when the fan is running at its rated maximum speed, the controller acquires the current carbon monoxide concentration value C2 of the first sensor group every 10 seconds (taking the average of the 3 data points) to monitor concentration changes in real time. When the fan has been running at full speed for the first preset duration (30 minutes), the controller first determines whether C2 has dropped below the second concentration threshold (12 ppm): If C2 ≤ 12 ppm, the controller generates a delay control command, ordering the fan to continue running at its rated maximum speed for a delay duration T2, where T2 = k × T1 (for example, when T1 = 15 minutes and k = 0.2, T2 = 3 minutes; when T1 = 10 minutes and k = 0.2, T2 = 2 minutes); if C2 > 12 ppm, the controller does not generate a delay control command and directly proceeds to the subsequent process. After T2, the controller stops the timer and begins the subsequent operations in the previous technical solution: acquiring the carbon monoxide and nitrogen oxide concentration data from the second sensor group, and calculating the concentration gradient G of the two pollutants over time. co With G noxBased on the current supply air velocity (the average wind velocity from the wind speed sensor over 10 minutes), and according to the dominant pollutant type, the corresponding control model (first or second control model) is invoked to calculate the required air volume. Finally, a second control command is generated to adjust the fan to a stable speed between 60% and 90% of its rated maximum speed. If, during the fan's full-speed operation (including the first preset duration and T2 duration), the timer displays the maximum allowable continuous operating time T1, regardless of whether C2 drops below 12 ppm, the controller will prematurely terminate full-speed operation and directly proceed to the subsequent gradient calculation and speed adjustment process. This prevents excessive energy consumption or equipment overload caused by prolonged full-speed operation of the fan.

[0040] Compared to ventilation systems without delay control and maximum allowable duration, this technical solution has significant advantages: Existing systems adjust the fan speed directly after the fan has run at full speed for a preset time, regardless of whether the pollutants have dropped to a low level, which may lead to a subsequent rebound due to unstable concentration; while this solution determines whether to extend the full-speed operation time by judging whether C2 has dropped to the second concentration threshold, ensuring that the pollutants are fully diluted; at the same time, the maximum allowable duration T1 limits the upper limit of the fan's full-speed operation, avoiding energy waste and equipment damage caused by the fan running at full speed for a long time when C1 is too high (the pollutant concentration is seriously exceeded).

[0041] In another technical solution, the controller is further configured to perform the following operations: Real-time monitoring of the output signal status of the first carbon monoxide sensor group and the second carbon monoxide sensor group; When the output signal of the first carbon monoxide sensor group or the second carbon monoxide sensor group is continuously abnormal, it is determined that a sensor malfunction has occurred. The abnormal output signal includes signal loss and exceeding the preset range of the sensor. When a sensor malfunction is detected, the controller generates a fault control command; the fault control command instructs the ventilation fan to run continuously at a fixed speed of 70%-80% of its rated maximum speed; at the same time as generating the fault control command, the controller starts a fault timer; when the fault timer reaches the preset fault handling duration, the controller automatically attempts to restore the normal intelligent ventilation control logic.

[0042] In the above technical solution, the intelligent ventilation control system for tunnel construction uses an industrial-grade PLC controller. In addition to the existing functions, a sensor signal status monitoring module needs to be added. This module can detect the output signal voltage or current value of the first and second multi-parameter gas sensor groups in real time through the analog input interface of the controller to determine whether the signal is normal. At the same time, a fault timer module needs to be integrated to support a timing range of 0-999 hours to record the duration of the fault state.

[0043] Before system operation, parameter presets must be completed: First, the normal range of the sensor output signal must be defined. Since the sensor uses a 4-20mA analog signal output, corresponding to a carbon monoxide concentration of 0-100ppm and a nitrogen oxide concentration of 0-20ppm, the "signal loss" is set as the sensor output current being below 3.8mA or above 20.2mA for 10 seconds (considering signal transmission error, a fluctuation range of ±0.2mA is reserved); "exceeding the preset range" is set as the concentration value corresponding to the sensor output current exceeding 0-100ppm (carbon monoxide) or 0-20ppm (nitrogen oxides) for 10 seconds (e.g., a current of 20mA corresponds to 100ppm carbon monoxide. If the current is above 20mA for 10 seconds, the corresponding concentration exceeds 100ppm, which is judged as exceeding the range). Meanwhile, the preset fault handling time is 2 hours (which can be adjusted according to the tunnel construction shift; a fault troubleshooting cycle of 2 hours is used in regular construction, which is in line with the response time of on-site maintenance personnel). In the fault state, the fixed speed range of the fan is set to 75% of the rated maximum speed (the value range is 70%-80%, and 75% is the middle value. Experiments have verified that this speed can ensure the basic ventilation needs of the tunnel and avoid the accumulation of pollutants, while avoiding energy waste due to excessive speed). The definition of "rated maximum speed" is the same as above, that is, the rated speed marked on the fan product nameplate.

[0044] When the system is working, the controller collects the output signals of the first and second sensor groups in real time through the signal status monitoring module and judges the signal every second: if the output signal of any sensor (any one of the first or second sensor groups) meets the conditions of "signal loss" or "exceeding the preset range" for 10 seconds, the controller immediately judges that a sensor failure has occurred and generates a fault control command, ordering the ventilation fan to switch from the current operating state to a fixed speed of 75% of the rated maximum speed for continuous operation; at the same time, the fault timer is started to accumulate the duration of the fault state. During fault operation, the controller continuously monitors the sensor signal status. If the sensor signal returns to normal (output current returns to 3.8-20.2mA, and the corresponding concentration is within the range), the fault control command is immediately terminated, and operation resumes according to the normal control logic before the fault. If the sensor signal does not recover, when the accumulated fault timer reaches the preset 2-hour fault handling time, the controller automatically attempts to restore the normal intelligent ventilation control logic. The specific operations include: re-initializing the sensor communication interface, clearing historical fault records, and rereading the real-time concentration data of the first and second sensor groups. If the reread signal is normal, the operation proceeds according to the process of the previous technical solution (calculating the concentration gradient, matching the control model, and adjusting the stable speed). If the reread signal is still abnormal, the fault speed operation continues, and a continuous alarm signal is issued through the external alarm device (such as an audible and visual alarm) to remind on-site maintenance personnel to inspect the sensors.

[0045] Compared to ventilation systems without sensor fault handling mechanisms, this technical solution has significant advantages: In existing systems, if sensors malfunction, the inability to obtain concentration data may cause the fan to stop or run at full speed continuously. Stopping may lead to excessive pollutants, while running at full speed wastes energy. In contrast, this solution monitors the sensor signal status in real time and immediately switches to a fixed operating mode of 75% of the rated speed in the event of a fault. This ensures ventilation of the tunnel foundation while avoiding excessive energy consumption. At the same time, the fault timer and automatic recovery logic reduce the frequency of manual intervention and adapt to scenarios where maintenance personnel cannot be on duty in real time during tunnel construction.

[0046] In another technical solution, the controller is communicatively connected to a construction plan input device; the controller is further configured to perform the following operations: The construction plan input device obtains information on current or upcoming construction procedures, including drilling, blasting, slag removal, and support. Based on the construction procedure information, the corresponding baseline ventilation configuration is retrieved from the preset procedure-ventilation strategy mapping table; wherein, the baseline ventilation configuration corresponding to the blasting procedure is to set the first concentration threshold to a first value and adjust the setting range of the stable speed of the ventilation fan to 80%-90% of the rated maximum speed; the baseline ventilation configuration corresponding to the slag removal procedure is to set the first concentration threshold to a second value and adjust the setting range of the stable speed of the ventilation fan to 60%-70% of the rated maximum speed, wherein the first value is less than the second value; Simultaneously with initiating the construction process, the controller loads the corresponding baseline ventilation configuration and performs corresponding control operations based on this configuration.

[0047] In the above technical solution, the intelligent ventilation control system for tunnel construction, based on the aforementioned technical solution, still uses an industrial-grade PLC controller. It needs to be connected to the construction plan input device via an RS485 communication interface. The construction plan input device can be an industrial-grade touch screen or an embedded input terminal with a keyboard (both are readily available devices on the market). It supports manual input or selection of the current / soon-to-be-performed construction procedures (drilling, blasting, slag removal, support) by the staff. The input device is installed on the operating platform next to the power distribution box at the tunnel entrance, at a height of 1.2m, which is convenient for operation and avoids direct coverage by construction dust.

[0048] Before the system runs, basic configuration and mapping table presets must be completed: First, establish a "process-ventilation strategy mapping table" in the controller to clarify the benchmark ventilation parameters corresponding to different construction processes—for the blasting process, the first concentration threshold is set to 18ppm (i.e., the first value, lower than other processes, because blasting will instantly generate a large amount of carbon monoxide and nitrogen oxides, requiring earlier emergency ventilation), and the fan stable speed setting range is adjusted to 85% of the rated maximum speed (the value range is 80%-90%, the intermediate value takes into account both rapid purification and equipment load); for the slag removal process, the first concentration threshold is set to 30ppm (i.e., the second value, the first value of 18ppm is lower than the first value of 18ppm). The second value is 30 ppm. Since only a small amount of dust and residual pollutants are generated during slag removal, there is no need to trigger strong ventilation prematurely. The stable speed setting range of the fan is adjusted to 65% of the rated maximum speed (the value range is 60%-70%, with the intermediate value balancing ventilation demand and energy consumption). For the drilling process, the first concentration threshold is set to 25 ppm, and the stable speed range is set to 70%-75% of the rated maximum speed. For the support process, the first concentration threshold is set to 28 ppm, and the stable speed range is set to 65%-70% of the rated maximum speed (the parameters for drilling and support processes are determined based on experiments on pollutant release during conventional tunnel construction to ensure that neither risks are overlooked nor energy is wasted). At the same time, the first preset duration remains 30 minutes, and the calculation model for the maximum allowable continuous running time, the delay time coefficient k, and other parameters are all consistent with the above to avoid parameter conflicts.

[0049] When the system is in operation, staff select the upcoming construction procedure (e.g., "blasting") via the construction plan input device. The input device transmits the procedure signal to the controller via an RS485 interface. Upon receiving the signal, the controller immediately retrieves the corresponding baseline ventilation configuration from the "procedure-ventilation strategy mapping table" (e.g., the first concentration threshold of 18 ppm and stable speed range of 80%-90% for blasting) and loads it into the control program. Simultaneously with the start of the construction procedure (e.g., the start of the blasting operation's timing), the controller executes control operations based on the loaded baseline configuration: If it is a blasting procedure, when the first sensor group detects a carbon monoxide concentration exceeding 18 ppm, the fan is immediately triggered to run at its rated maximum speed; after a preset 30-minute period, the concentration change gradient is calculated, and the fan is ultimately adjusted to a stable value of 80%-90% of its rated speed to ensure rapid discharge of high-concentration pollutants generated by the blasting. For slag removal processes, the fan is only triggered to run at full speed when the first sensor group detects a carbon monoxide concentration exceeding 30 ppm. The subsequent stable speed is controlled at 60%-70% of the rated speed to avoid energy waste during the low-pollution period of slag removal. If the construction process changes (e.g., from blasting to slag removal), staff update the process information via the input device, and the controller switches to the corresponding baseline ventilation configuration in real time without restarting the system, ensuring that the ventilation strategy is adjusted synchronously when processes are connected.

[0050] Compared to traditional systems with fixed ventilation parameters, this technical solution has significant advantages: Traditional systems use the same set of concentration thresholds and rotation speed ranges regardless of the construction process. During blasting, excessively high thresholds may lead to excessive pollutants, and excessively high rotation speeds may waste energy during slag removal. In contrast, this solution achieves "process-adaptive" ventilation control through construction plan input and strategy mapping tables—high-pollution processes (blasting) use low thresholds and high rotation speeds for rapid pollution control; low-pollution processes (slag removal) use high thresholds and low rotation speeds for energy saving and consumption reduction.

[0051] In another technical solution, the controller is further configured to perform the following operations: When the ventilation fan runs continuously at the stable speed for a duration exceeding the first duration threshold, and during this period the concentration value monitored by the first carbon monoxide sensor group remains below the third concentration threshold, a low-power operation mode is activated. The low-power operation mode controls the ventilation fan to operate alternately within a preset working cycle; wherein, each working cycle includes a running segment and a stopping segment, the length of the running segment is set to 1.5-2.5 times the length of the stopping segment, and the speed of the ventilation fan during the running segment is set to 40%-50% of the rated maximum speed.

[0052] In the above technical solution, the intelligent ventilation control system for tunnel construction uses an industrial-grade PLC controller. A low-power operation mode control module needs to be added to the original functions. This module can realize the alternating control of the running period and the stop period through the internal program logic of the controller without the need for additional external hardware. At the same time, a first duration threshold needs to be preset to determine whether to trigger the low-power mode.

[0053] Before system operation, key parameters need to be preset: First, set the first duration threshold to 4 hours (this value is determined based on the normal duration of tunnel construction intervals or low-pollution processes (such as the later stages of support). Verified by multiple tunnel experiments, 4 hours can both prevent short-term concentration fluctuations from falsely triggering the low-power mode and ensure timely energy-saving operation under long-term low-pollution conditions); Second, set the working cycle parameters for the low-power operation mode—each working cycle includes one running segment and one stopping segment, with the running segment length set to 20 minutes and the stopping segment length set to 10 minutes (meeting the requirement that the running segment length is 1.5-2.5 times the stopping segment length, and the ratio of 20 minutes to 10 minutes is 2:1, falling within the middle of this range, balancing...). The requirements are to "maintain air circulation in the tunnel" and "maximize energy saving"; at the same time, the speed of the ventilation fan during operation is set to 45% of the rated maximum speed (the value range is 40%-50%, and 45% is the middle value. For example, if the rated maximum speed of the fan is 1450 r / min, then the speed during operation is 652.5 r / min. Experiments have verified that this speed can ensure that there is no significant accumulation of pollutants in the tunnel during the shutdown period, and the energy consumption is reduced by about 40% compared with the stable speed (60%-90% of the rated speed); in addition, the third concentration threshold is set to 8 ppm (this value refers to the long-term allowable lower limit of carbon monoxide concentration in tunnels in the "Coal Mine Safety Regulations". It ensures that the air quality in the tunnel is at a safe level when it is below this value, and the low power consumption mode can be activated).

[0054] When the system is working, the controller monitors the operating status of the ventilation fan in real time: when the fan is running at a stable speed (60%-90% of the rated maximum speed), the controller starts to accumulate the continuous running time of the stable speed, and acquires the monitoring data of the first carbon monoxide sensor group every 10 seconds (taking the average value of the concentration of 3 points) to determine whether the concentration value is continuously lower than the third concentration threshold (8ppm). If both conditions are met—"continuous operation at stable speed for more than 4 hours" and "the concentration monitored by the first carbon monoxide sensor group remains below 8 ppm during this period" ("remaining below" means the concentration value never exceeds 8 ppm and there are no abnormal sensor signals)—the controller immediately triggers a low-power operation mode and controls the fan to run according to a preset work cycle. First, the fan is controlled to run at 45% of its rated maximum speed (e.g., 652.5 r / min) for 20 minutes (running period). During this period, the airflow speed is monitored by the wind speed sensor to ensure that the air volume meets the basic ventilation requirements. After the running period ends, the controller controls the fan to stop running for 10 minutes (stop period). During the stop period, the concentration data of the first carbon monoxide sensor group is continuously monitored. If the concentration exceeds 8 ppm at any time during the stop period, the low-power mode is immediately terminated, and the fan is controlled to resume operation at the previous stable speed. If the concentration remains below 8 ppm during the stop period, the cycle of "20 minutes of operation + 10 minutes of stop" continues. During low-power mode operation, if the concentration of the first carbon monoxide sensor group continuously exceeds 8 ppm, or if the operator updates the process to a high-pollution procedure (such as blasting) through the construction plan input device, the controller will immediately exit the low-power mode and re-execute the normal control logic of "concentration monitoring - threshold judgment - speed adjustment" to ensure that pollutants are discharged in a timely manner.

[0055] Compared to ventilation systems without a low-power mode, this technical solution offers significant energy-saving advantages: traditional systems maintain a high and stable operating speed even under long-term low-pollution conditions, resulting in energy waste; while this solution activates the low-power mode only when air quality is safe and consistently stable by setting dual trigger conditions of duration and concentration, thus avoiding the risk of pollutant accumulation and significantly reducing energy consumption.

[0056] In another technical solution, the controller is further configured to perform the following operations: During the period when the ventilation fan runs continuously at the stable speed for more than the second duration threshold, monitoring data from the first carbon monoxide sensor group and the second carbon monoxide sensor group are continuously acquired. Calculate the average difference ΔC between the readings of the first carbon monoxide sensor group and the readings of the second carbon monoxide sensor group; when the absolute value of the average difference ΔC continuously exceeds a preset difference threshold ΔC... TWhen the time comes, a sensor calibration prompt signal is generated; the sensor calibration prompt signal contains indication information that the first carbon monoxide sensor group or the second carbon monoxide sensor group needs to be calibrated.

[0057] In the above technical solution, the intelligent ventilation control system for tunnel construction, based on the aforementioned technical solution, uses an industrial-grade PLC controller. It needs to add a sensor data difference calculation module through the internal program to calculate the average difference ΔC between the readings of the first and second multi-parameter gas sensor groups (simultaneously monitoring carbon monoxide and nitrogen oxide concentrations) in real time, and determine whether to trigger a calibration prompt; at the same time, it needs to integrate a second duration threshold parameter to limit the time range of concentration difference monitoring.

[0058] Before system operation, key parameters need to be preset: First, set the second duration threshold to 2 hours (this value is determined based on the normal operating cycle of the tunnel ventilation system; experimental verification shows that 2 hours can cover the time required for sensor readings to stabilize and can also promptly detect sensor drift problems during long-term operation); second, set the difference threshold ΔC. T —Regarding carbon monoxide concentration, ΔC T Set to 5 ppm (referencing the sensor's accuracy range of ±2 ppm, considering the concentration decay due to natural diffusion of pollutants in the tunnel (normally, the concentration decreases with distance from the working face; the average concentration of the first sensor group should be higher than that of the second sensor group, with the absolute value of the difference usually not exceeding 3 ppm). A threshold of 5 ppm can effectively distinguish between "normal concentration differences" and "sensor calibration deviations"); for nitrogen oxide concentration, ΔC T Set the threshold to 1.5 ppm (considering its ±0.5 ppm accuracy and faster diffusion characteristics, the absolute value of the normal difference is usually no more than 0.8 ppm, and the 1.5 ppm threshold can avoid falsely triggering calibration prompts); at the same time, clarify the calculation rules for the average difference ΔC: collect the average concentration of the three points of the first sensor group every 5 minutes (denoted as C). 1平 For example, the carbon monoxide concentration is the arithmetic mean of readings at 35m, 40m, and 45m, and the average concentration of the three points of the second sensor group (denoted as C). 2平 (The arithmetic mean of the readings at 60m, 75m, and 90m is taken), ΔC = C 1平 -C 2平 (Round to one decimal place), if the calculation result is negative (i.e., C) 1平 <C 2平 If the value does not conform to the normal pattern of pollutant diffusion, then the absolute value is used for judgment.

[0059] When the system is working, if the ventilation fan runs continuously at a stable speed (60%-90% of the rated maximum speed) for more than the second time threshold (2 hours), the controller will automatically start the sensor reading difference monitoring process: at a frequency of once every 5 minutes, it will synchronously collect carbon monoxide and nitrogen oxide concentration data from the first and second sensor groups, and calculate the corresponding ΔC (carbon monoxide ΔC). co Nitrogen oxides ΔC nox The controller determines whether the absolute value of ΔC exceeds the preset ΔC for three consecutive times (i.e., within 15 minutes). T —If ΔC co The absolute value is ≥5 ppm for 3 consecutive times, or ΔC nox If the absolute value is ≥1.5ppm for three consecutive times, the controller immediately generates a sensor calibration prompt signal; this prompt signal contains clear indication information: if only ΔC co Exceeding the limit, the system prompts "The first or second carbon monoxide sensor group needs calibration" (further assessment using single data points: if C...). 1平 If the concentration is significantly higher than the normal range (e.g., exceeding 20 ppm, even though the tunnel has no highly polluting processes), then the first sensor group should be calibrated first; if C 2平 Much higher than C 1平 (If the difference is -8ppm, then the second sensor group calibration will be prompted first); if only ΔC nox If the value exceeds the limit, a message will be displayed stating "Neither the first nor the second nitrogen oxide sensor group needs calibration." If both exceed the limit, both sensor groups will be prompted for calibration simultaneously. The calibration prompt signal can be emitted via an external audible and visual alarm (buzzer + red indicator light) connected to the controller, or transmitted via a communication interface to a display screen in the tunnel control room, visually displaying the type of sensor group requiring calibration. This facilitates maintenance personnel bringing calibration equipment (such as a standard gas calibrator) into the tunnel for calibration operations. After calibration, the staff can clear the calibration prompt signal using the controller's reset button, and the system will resume normal differential monitoring and ventilation control logic.

[0060] Compared to ventilation systems without sensor calibration prompts, this technical solution offers significant advantages: traditional systems cannot detect sensor drift in a timely manner (such as sensor readings becoming too high or too low after prolonged use), potentially leading to distorted concentration monitoring data. For example, if the first sensor group drifts too high, it may falsely trigger the fan to run at full speed, wasting energy; if the second sensor group drifts too low, it will cause deviations in concentration gradient calculations, affecting the accuracy of airflow regulation. This solution, however, continuously monitors the consistency of readings from both sensor groups by setting time and difference thresholds. It promptly triggers calibration prompts when sensor drift occurs, ensuring the accuracy of concentration data and providing a reliable basis for subsequent ventilation control.

[0061] This invention also discloses a method for intelligent ventilation control in tunnel construction based on the aforementioned intelligent ventilation control system, characterized by comprising the following steps: The carbon monoxide concentration within a range of 30-50m from the tunnel working face is monitored using the first carbon monoxide sensor group. The carbon monoxide concentration within a range of 50-100m from the tunnel working face is monitored using a second carbon monoxide sensor group. The airflow velocity at the outlet of the ventilation duct is monitored using a wind speed sensor. When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds the preset first concentration threshold, the ventilation fan is controlled to run at the rated maximum speed for a first preset time. After the first preset time period ends, the carbon monoxide concentration data monitored by the second carbon monoxide sensor group is acquired, and the gradient of carbon monoxide concentration change at the location of the second carbon monoxide sensor group is calculated. Simultaneously, the current supply air speed monitored by the wind speed sensor is acquired; Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated using a preset control model, and the ventilation fan is controlled to operate at a stable speed between 60% and 90% of its rated maximum speed.

[0062] In the above technical solution, the intelligent ventilation control method for tunnel construction is based on the intelligent ventilation control system for tunnel construction. The selection, assembly, and parameter preset of each component in the system must be consistent with the specific implementation of the aforementioned technical solution: the first carbon monoxide sensor group selects an electrochemical carbon monoxide sensor (range 0-100ppm, accuracy ±2ppm, response time ≤30 seconds), which is evenly arranged at 35m, 40m, and 45m away from the tunnel working face and fixed at a height of 1.5m on the non-working side wall of the tunnel; the second carbon monoxide sensor group selects the same model. The sensors are positioned at 60m, 75m, and 90m from the tunnel working face, with the installation method consistent with the first sensor group. The wind speed sensor is a duct-type wind speed transmitter (range 0-20m / s, accuracy ±0.1m / s), installed in the center of the ventilation duct outlet. The ventilation fan is a variable frequency centrifugal fan (rated maximum speed as indicated on the product nameplate, such as 1450r / min). The controller is an industrial-grade PLC controller with analog input / output interfaces and data processing functions. All components are connected to the controller via shielded cables to ensure stable data transmission.

[0063] Before the system runs, basic parameter configurations must be completed in the controller: set the first concentration threshold to 24 ppm, the first preset duration to 30 minutes, and the stable speed range to 60%-90% of the rated maximum speed of the ventilation fan; the preset control model is a linear regression model, with the expression Q=K×G×V (Q is the required air volume, in m³ / s). 3 / h; G is the concentration gradient of the second sensor group over time, in ppm / min; V is the current supply air velocity, in m / s; K is the correction factor, taken according to the tunnel cross-sectional area, 10-15m². 2 When K=120, 15-20m 2 When K=135, 20-25m 2 (When K=150, it was obtained by fitting through tunnel ventilation experiment); At the same time, the calculation rules for the concentration change gradient were clarified: Starting from the end of the first preset time period, the concentration data of the second sensor group was continuously collected for 10 minutes (sampling frequency 1 minute / time). After removing outliers that exceeded the range or had a difference of more than 5 ppm from adjacent data, the gradient G was calculated by linear regression formula to ensure that the gradient data reflects the true trend of concentration change over time.

[0064] The specific execution steps of this control method are as follows: The first step is to start sensor monitoring: The first carbon monoxide sensor group monitors the carbon monoxide concentration in real time within a range of 30-50m from the tunnel working face, collecting concentration data from 3 points every 10 seconds and taking the average value (denoted as C1); the second carbon monoxide sensor group simultaneously monitors the carbon monoxide concentration in a range of 50-100m from the tunnel working face, collecting concentration data from 3 points every minute and taking the average value (denoted as C2); the wind speed sensor monitors the airflow speed at the ventilation duct outlet in real time, collecting data every 30 seconds and taking the average value of 5 consecutive data (denoted as V). All monitoring data are transmitted to the controller in real time.

[0065] The second step is to trigger emergency ventilation: The controller continuously compares C1 with the first concentration threshold (24ppm). If C1 exceeds 24ppm for 3 consecutive seconds (to avoid accidental triggering due to momentary interference), the controller immediately generates a control command to control the ventilation fan to run at the rated maximum speed (e.g., 1450r / min) and starts a timer to record the running time, ensuring rapid dilution of high concentrations of pollutants near the work surface.

[0066] The third step is to calculate the concentration gradient and wind speed: After the fan runs at its rated maximum speed for the first preset time (30 minutes), the controller stops the timer and automatically retrieves the concentration data (a total of 10 C2 values) stored in the second sensor group over the past 10 minutes. After removing outliers according to preset rules, the data is then calculated using the linear regression formula G = (nΣt) i C 2i - Σti ΣC 2i ) / (nΣti 2 -(Σti) 2 (n=10, t) i The concentration gradient G over time is calculated (0-9 min); at the same time, the average wind speed data of the wind speed sensor over the past 5 minutes is retrieved to determine the current supply wind speed V.

[0067] The fourth step is to determine and adjust the stable speed: The controller substitutes the calculated G and V into the preset control model Q=K×G×V to calculate the required air volume Q; then, according to the "air volume-speed" curve provided by the ventilation fan manufacturer, it finds the fan speed that matches Q; if the speed is within 60%-90% of the rated maximum speed, the controller generates a control command to adjust the fan to operate stably at that speed; if the calculated speed is lower than 60%, it is adjusted to 60% of the rated speed; if it is higher than 90%, it is adjusted to 90% of the rated speed, ensuring that the fan operation meets the ventilation requirements while avoiding excessive speed that could lead to energy waste or equipment overload.

[0068] Compared with traditional tunnel ventilation control methods (such as manually adjusting fan speed and fixed air volume ventilation), this control method has significant advantages in practicality and reliability: traditional methods rely on manual monitoring and adjustment of concentration, which is slow to respond and prone to human error; fixed air volume ventilation cannot dynamically adapt to changes in pollutants, which may lead to excessive energy consumption or concentration exceeding the standard; while this method forms a closed-loop control of "monitoring-judgment-adjustment" through real-time monitoring by sensors, automatic calculation by the controller and dynamic speed adjustment, which can achieve precise air volume matching without manual intervention.

[0069] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and technical solutions shown and described herein.

Claims

1. An intelligent ventilation control system for tunnel construction, characterized in that, It includes a controller, a speed-adjustable ventilation fan, a first carbon monoxide sensor group, a second carbon monoxide sensor group, and a wind speed sensor. The controller is communicatively connected to the ventilation fan, the first carbon monoxide sensor group, the second carbon monoxide sensor group, and the wind speed sensor, respectively. The ventilation fan is used to force fresh air into the tunnel working face through the ventilation duct. The first carbon monoxide sensor group is arranged within a range of 30-50m from the tunnel working face, and the second carbon monoxide sensor group is arranged within a range of 50-100m from the tunnel working face. The wind speed sensor is arranged at the outlet of the ventilation duct. The controller is configured to perform the following operations: When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds a preset first concentration threshold, a first control command is generated, which commands the ventilation fan to run at its rated maximum speed for a first preset duration. After the first preset duration ends, the carbon monoxide concentration data detected by the second carbon monoxide sensor group is acquired, and the carbon monoxide concentration change gradient at the location of the second carbon monoxide sensor group is calculated. At the same time, the current air supply speed detected by the wind speed sensor is acquired. Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated through a preset control model, and a second control command is generated. The second control command commands the ventilation fan to adjust to a stable speed, which is 60%-90% of the rated maximum speed of the ventilation fan.

2. The intelligent ventilation control system for tunnel construction as described in claim 1, characterized in that, Both the first and second carbon monoxide sensor groups are multi-parameter gas sensor groups used to simultaneously monitor carbon monoxide and nitrogen oxide concentrations; the controller is further configured to perform the following operations: Based on the data monitored by the multi-parameter gas sensor group, the concentration change gradient G of carbon monoxide is calculated respectively. co and the concentration gradient G of nitrogen oxides nox ; G co With the first gradient threshold G coT Compare and put G nox With the second gradient threshold G noxT The comparison is made, wherein the first gradient threshold G coT Less than the second gradient threshold G noxT ; When G co ≥G coT And G nox <G noxT At that time, carbon monoxide was determined to be the dominant pollutant, and the required air volume was calculated using the first control model; When G nox ≥G noxT And G co <G coT When nitrogen oxides are identified as the dominant pollutant, a second control model is used to calculate the required air volume. This second control model is configured such that, for the same concentration change gradient input value, the required air volume calculated by it is 15%-25% higher than the required air volume calculated by the first control model. When G co ≥G coT And G nox ≥G noxT When the pollution is determined to be a complex pollution state, the larger value between the calculation results of the first control model and the second control model is selected as the final required air volume.

3. The intelligent ventilation control system for tunnel construction as described in claim 2, characterized in that, The controller is further configured to perform the following operations: while generating the first control command that commands the ventilation fan to operate at its rated maximum speed, a timer is started; Based on the initial carbon monoxide concentration value C1 when the first control command is generated, the corresponding maximum allowable continuous running time T1 is calculated through a preset duration calculation model, where the larger the value of C1, the smaller the value of T1. While the ventilation fan is operating at its rated maximum speed, the current carbon monoxide concentration (C2) is monitored in real time. When the continuous running time of the ventilation fan reaches the first preset duration and C2 drops below the second concentration threshold, wherein the second concentration threshold is 40%-60% of the first concentration threshold, the controller generates a delay control command. The delay control command instructs the ventilation fan to continue operating at the rated maximum speed for a delay time T2, where T2 = k × T1, k is a coefficient and its value ranges from 0.1 to 0.3; After T2 ends, the controller then performs the operations of acquiring data from the second carbon monoxide sensor group, calculating the concentration change gradient, and generating the second control command.

4. The intelligent ventilation control system for tunnel construction as described in claim 3, characterized in that, The controller is further configured to perform the following operations: Real-time monitoring of the output signal status of the first carbon monoxide sensor group and the second carbon monoxide sensor group; When the output signal of the first carbon monoxide sensor group or the second carbon monoxide sensor group is continuously abnormal, it is determined that a sensor malfunction has occurred. The abnormal output signal includes signal loss and exceeding the preset range of the sensor. When a sensor malfunction is detected, the controller generates a fault control command; the fault control command instructs the ventilation fan to run continuously at a fixed speed of 70%-80% of its rated maximum speed; at the same time as generating the fault control command, the controller starts a fault timer; when the fault timer reaches the preset fault handling duration, the controller automatically attempts to restore the normal intelligent ventilation control logic.

5. The intelligent ventilation control system for tunnel construction as described in claim 4, characterized in that, The controller is communicatively connected to a construction plan input device; the controller is further configured to perform the following operations: The construction plan input device obtains information on current or upcoming construction procedures, including drilling, blasting, slag removal, and support. Based on the construction procedure information, the corresponding baseline ventilation configuration is retrieved from the preset procedure-ventilation strategy mapping table; wherein, the baseline ventilation configuration corresponding to the blasting procedure is to set the first concentration threshold to a first value and adjust the setting range of the stable speed of the ventilation fan to 80%-90% of the rated maximum speed; the baseline ventilation configuration corresponding to the slag removal procedure is to set the first concentration threshold to a second value and adjust the setting range of the stable speed of the ventilation fan to 60%-70% of the rated maximum speed, wherein the first value is less than the second value; Simultaneously with initiating the construction process, the controller loads the corresponding baseline ventilation configuration and performs corresponding control operations based on this configuration.

6. The intelligent ventilation control system for tunnel construction as described in claim 5, characterized in that, The controller is further configured to perform the following operations: When the ventilation fan runs continuously at the stable speed for a duration exceeding the first duration threshold, and during this period the concentration value monitored by the first carbon monoxide sensor group remains below the third concentration threshold, a low-power operation mode is activated. The low-power operation mode controls the ventilation fan to operate alternately within a preset working cycle; wherein, each working cycle includes a running segment and a stopping segment, the length of the running segment is set to 1.5-2.5 times the length of the stopping segment, and the speed of the ventilation fan during the running segment is set to 40%-50% of the rated maximum speed.

7. The intelligent ventilation control system for tunnel construction as described in claim 6, characterized in that, The controller is further configured to perform the following operations: During the period when the ventilation fan runs continuously at the stable speed for more than the second duration threshold, monitoring data from the first carbon monoxide sensor group and the second carbon monoxide sensor group are continuously acquired. Calculate the average difference ΔC between the readings of the first carbon monoxide sensor group and the readings of the second carbon monoxide sensor group; When the absolute value of the average difference ΔC continuously exceeds the preset difference threshold ΔC T When the time comes, a sensor calibration prompt signal is generated; the sensor calibration prompt signal contains indication information that the first carbon monoxide sensor group or the second carbon monoxide sensor group needs to be calibrated.

8. A method for intelligent ventilation control in tunnel construction based on the intelligent ventilation control system for tunnel construction as described in claim 1, characterized in that, Includes the following steps: The carbon monoxide concentration within a range of 30-50m from the tunnel working face is monitored using the first carbon monoxide sensor group. The carbon monoxide concentration within a range of 50-100m from the tunnel working face is monitored using a second carbon monoxide sensor group. The airflow velocity at the outlet of the ventilation duct is monitored using a wind speed sensor. When the carbon monoxide concentration value detected by the first carbon monoxide sensor group exceeds the preset first concentration threshold, the ventilation fan is controlled to run at the rated maximum speed for a first preset time. After the first preset time period ends, the carbon monoxide concentration data monitored by the second carbon monoxide sensor group is acquired, and the gradient of carbon monoxide concentration change at the location of the second carbon monoxide sensor group is calculated. Simultaneously, the current supply air speed monitored by the wind speed sensor is acquired; Based on the carbon monoxide concentration change gradient and the current air supply speed, the required air volume is calculated using a preset control model, and the ventilation fan is controlled to operate at a stable speed between 60% and 90% of its rated maximum speed.