Freezing wall on-line monitoring method and system for tunnel freezing engineering

Abstract

The present application relates to the technical field of tunnel freezing engineering monitoring, in particular to a freezing wall online monitoring method and system for tunnel freezing engineering. Time series data of the temperature of each freezing pipe monitoring point is obtained, the soil layer looseness degree and freezing interference index are quantified through the temperature difference, amplitude trend and fluctuation characteristics of the monitoring point, and the foregoing two indexes are further combined with the position distribution of the freezing pipe monitoring point to determine the freezing liquid demand index of each freezing pipe. The freezing liquid correction value is dynamically adjusted according to the freezing liquid demand index, which is used to match the actual cold demand. Through time series analysis of the chaotic index of the freezing liquid correction value of each freezing pipe, the delivery pause evaluation index is calculated. If the evaluation index is out of limit, the circulation of the low demand freezing pipe is paused, the high demand pipe is operated according to the correction value, otherwise the full pipe dynamic adjustment is maintained. The method quantifies the soil layer characteristics and interference factors through multi-parameter coupling, realizes accurate adaptation of cold supply, and effectively controls the uniformity of the freezing wall.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel freezing engineering monitoring, and particularly relates to a freezing wall online monitoring method and system for tunnel freezing engineering. BACKGROUND

[0002] In tunnel engineering, the freezing method is an important construction auxiliary technology, which is especially suitable for complex geological conditions such as water-rich soft stratum. The method arranges freezing pipes around the tunnel, circulates low-temperature frozen liquid, freezes the surrounding soil layer to form a closed freezing wall, and thus plays a role of temporary support and water isolation. In the tunnel freezing engineering, it is crucial to uniformly adjust the temperature at different positions of the freezing wall. Uneven temperature distribution will lead to differences in the strength and thickness of the freezing wall, forming structural weak links and significantly increasing the risk of water inrush and sand gushing.

[0003] In the prior art, the temperature threshold is fixed and compared with the actual temperature value at each position to control the frozen liquid flow of the freezing pipe, thereby realizing the monitoring process of the freezing wall. However, due to the complex and variable geological conditions of tunnel engineering in the tunnel environment, the temperature is easily affected by underground water flow, soil layer, thermal bridge effect, etc. These factors will cause different disturbances to the temperature at different positions. Therefore, if the differences in the disturbance of the temperature at different positions are ignored and the temperature threshold is uniformly set for frozen liquid flow control, the monitoring and control of the freezing wall will have great blindness. SUMMARY

[0004] In order to solve the technical problem that the geological conditions of tunnel engineering are complex and variable, the temperature is easily affected by underground water flow, soil layer, thermal bridge effect, etc. These factors will cause different disturbances to the temperature at different positions. Therefore, if the differences in the disturbance of the temperature at different positions are ignored and the temperature threshold is uniformly set for frozen liquid flow control, the monitoring and control of the freezing wall will have great blindness. The purpose of the present application is to provide a freezing wall online monitoring method and system for tunnel freezing engineering, and the technical solution is as follows:

[0005] A freezing wall online monitoring method for tunnel freezing engineering, comprising:

[0006] obtaining temperature time series data at each monitoring point on each freezing pipe;

[0007] At each time, based on the difference characteristics between the temperature values at all monitoring points, and analyzing the amplitude change trend of the temperature values of each monitoring point within a preset time window, a looseness index at each monitoring point is determined; at each time, the fluctuation change characteristics of the temperature values of all monitoring points within a preset time window are analyzed to determine a freezing interference index at each monitoring point;

[0008] At each time, based on the positional relationship between the monitoring points on the freezing pipe and the liquid supply main, and in combination with the looseness index and the freezing interference index corresponding to each monitoring point, a freezing liquid demand index of each freezing pipe is determined; at each time, the preset freezing liquid flow value is adjusted according to the freezing liquid demand index of each freezing pipe to obtain a freezing liquid correction value of each freezing pipe.

[0009] At all times, based on the degree of disorder of the freezing liquid correction values of all freezing pipes, the freezing liquid correction values of the freezing pipes are compared for monitoring the freezing wall at the current time.

[0010] Further, the method for obtaining the looseness index comprises:

[0011] At each time, the temperature value at each monitoring point is compared with the temperature value at other monitoring points in terms of difference characteristics, so as to determine a first looseness factor at each monitoring point.

[0012] A preset time window corresponding to each time is determined, and at each time, the amplitude change trend of the temperature values of each monitoring point within the preset time window is analyzed to determine a second looseness factor at each monitoring point.

[0013] At each time, the sum of the first looseness factor and the second looseness factor of each monitoring point is normalized to obtain the looseness index at each monitoring point.

[0014] Further, the method for obtaining the first looseness factor comprises:

[0015] Optionally, one monitoring point is taken as a to-be-tested point, and the remaining monitoring points are taken as reference points.

[0016] At each time, the temperature value difference between the to-be-tested point and each reference point is calculated as a temperature difference factor.

[0017] The sum of all temperature value difference factors corresponding to the to-be-tested point at each time is normalized to obtain the first looseness factor at the to-be-tested point.

[0018] Further, the method for obtaining the second looseness factor comprises:

[0019] At each time, within the preset time window of each monitoring point, a first-order difference sequence of the temperature value sequence is calculated.

[0020] In the first-order difference sequence, the number of positive values is taken as an increase quantity factor, and the ratio of the increase quantity factor to the total number of values in the first-order difference sequence is taken as an increase proportion factor;

[0021] The product of the normalized value of the mean of all values in the first-order difference sequence and the increase proportion factor is normalized to obtain a second looseness factor at each monitoring point.

[0022] Further, the method for obtaining the frozen interference index comprises:

[0023] At each time, within a preset time window at each monitoring point, curve data corresponding to the temperature value is obtained;

[0024] In each of the curve data, the difference between the maximum value and the minimum value is taken as a fluctuation range;

[0025] The number of extreme points in each of the curve data is taken as an extreme value quantity parameter, and the ratio of the extreme value quantity parameter of each curve data to the maximum value in the extreme value quantity parameters of all curve data is taken as a fluctuation frequency factor;

[0026] According to the fluctuation range and the fluctuation frequency factor corresponding to each monitoring point, a frozen interference index at each monitoring point is determined, and the fluctuation range and the fluctuation frequency factor are positively correlated with the frozen interference index.

[0027] Further, the method for obtaining the frozen liquid demand index comprises:

[0028] For any monitoring point, along the freezing pipe to which the monitoring point belongs, the length from the monitoring point to the liquid supply main is determined as a distance factor;

[0029] The value of the negative correlation mapping of the frozen interference index at the monitoring point is taken as a cooling demand factor of the monitoring point;

[0030] The product of the cooling demand factor, the corresponding looseness index, and the distance factor of the monitoring point is normalized to obtain a cooling demand index of the monitoring point;

[0031] On each freezing pipe, the number of monitoring points with a cooling demand index greater than a preset cooling demand threshold is counted as a demand quantity factor;

[0032] The product of the mean of the cooling demand indices of all monitoring points on each freezing pipe and the demand quantity factor of each freezing pipe is normalized to obtain a frozen liquid demand index of each freezing pipe.

[0033] Further, the method for obtaining the refrigerant correction value comprises:

[0034] Taking the sum of the refrigerant demand index of each freeze pipe and the preset parameter as a flow adjustment factor;

[0035] Taking the product of the flow adjustment factor of each freeze pipe and the preset refrigerant flow value as the refrigerant correction value of each freeze pipe.

[0036] Further, the method for comparing the refrigerant correction values of the freeze pipes based on the degree of disorder of the refrigerant correction values of all the freeze pipes at all time points for freeze wall monitoring at the current time point comprises:

[0037] At each time point, analyzing the degree of disorder of the refrigerant correction values of all the freeze pipes to determine a refrigerant flow disorder index of the freeze wall;

[0038] In time sequence, sequentially traversing the time points from the current time point forward, stopping when the refrigerant distribution disorder index of the freeze wall at the traversed time point is less than a preset disorder threshold, taking the time point corresponding to the stopping time as an endpoint time point, taking the time interval between the current time point and the endpoint time point as a disorder duration, and taking the sum of the refrigerant distribution disorder indexes of the freeze wall at all the traversed time points as a disorder parameter;

[0039] Taking the normalized value of the product of the disorder duration, the disorder parameter, and the refrigerant flow disorder index of the freeze wall at the current time point as a refrigerant delivery suspension evaluation index;

[0040] When the refrigerant delivery suspension evaluation index is greater than a preset suspension threshold, suspending the delivery of refrigerant to the freeze pipes with a refrigerant demand index less than a preset refrigerant demand threshold and delivering refrigerant to the freeze pipes with a refrigerant demand index greater than or equal to the preset refrigerant demand threshold according to the refrigerant correction value among all the freeze pipes corresponding to the freeze wall;

[0041] When the refrigerant delivery suspension evaluation index is less than or equal to the preset suspension threshold, delivering refrigerant to all the freeze pipes according to the refrigerant correction value.

[0042] Further, the method for obtaining the refrigerant flow disorder index comprises:

[0043] At each time point, calculating the standard deviation of the refrigerant correction values of all the freeze pipes as a first disorder factor;

[0044] At each time point, taking the difference between the maximum value and the minimum value of the refrigerant correction values of all the freeze pipes as a second disorder factor;

[0045] The product of the first and second chaotic factors is normalized at each time point, and the normalized value is used as a frozen wall frozen liquid flow chaotic index at each time point.

[0046] The application discloses a frozen wall online monitoring system for a tunnel freezing project.

[0047] The application has the following advantages:

[0048] First, the temperature time series data of each monitoring point on each freezing pipe is acquired, which is used for grasping the temperature dynamics of the water stratum at the position to be frozen. Due to the influence of underground water flow, soil layer, thermal bridge effect and the like, the cold energy loss of part of the freezing pipes is caused, and the temperature of part of the monitoring points is lower than that of other positions. Under the long-time cumulative effect, the shape of the frozen wall is distorted. Therefore, by comparing the temperature value difference characteristics between the monitoring points and the amplitude change trend of the temperature values of the monitoring points at each time point, the looseness index of each monitoring point is obtained, the heat conduction performance of different regions can be more accurately evaluated, and the uneven freezing caused by the difference in soil layer conditions is avoided. Meanwhile, the fluctuation change characteristics of the temperature values of the monitoring points are analyzed, the influence of external interference such as underground water seepage and construction disturbance on the freezing process is effectively identified, and the freezing interference index is calculated. Further, the cold energy loss of the refrigerant is different when the refrigerant reaches different positions in the freezing pipe. Therefore, the position distribution of the monitoring points on the freezing pipe is considered, and the looseness index and the freezing interference index are combined to determine the refrigerant demand index of each freezing pipe, which is used for realizing accurate regulation and control of the refrigerant flow to obtain a refrigerant correction value. By dynamically adjusting the refrigerant flow, the refrigerant supply of each freezing pipe is matched with the actual demand. However, when the refrigerant correction values required by different freezing pipes are quite different, the flow adjustment of different freezing pipes cannot make the temperature of the frozen wall around different freezing pipes adjust to be consistent as soon as possible, and the refrigerant circulation process of part of the freezing pipes should be stopped. Therefore, the chaotic degree of the refrigerant correction values of all the freezing pipes is analyzed at all times, so that the refrigerant correction values of the freezing pipes are compared to monitor the uniformity of the frozen wall. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art and the advantages thereof, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the field, other drawings can be obtained based on these drawings without any creative effort.

[0050] Figure 1 A method flow chart of a freezing wall online monitoring method for a tunnel freezing engineering provided by an embodiment of the present application;

[0051] Figure 2 A method flow chart of a loose index acquisition method provided by an embodiment of the present application;

[0052] Figure 3 A pipeline arrangement schematic diagram provided by an embodiment of the present application;

[0053] Figure 4 A system block diagram of a freezing wall online monitoring system for a tunnel freezing engineering provided by an embodiment of the present application;

[0054] Figure 5 A system structure schematic diagram of a freezing wall online monitoring system for a tunnel freezing engineering provided by an embodiment of the present application;

[0055] The figure mark: 1-monitoring point, 2-liquid supply main pipe, 3-freezing pipe, d-length from the monitoring point to the liquid supply main pipe. DETAILED DESCRIPTION

[0056] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined purposes, the following will combine the drawings and the preferred embodiments to specifically describe the specific implementation, structure, features and effects of the freezing wall online monitoring method and system for a tunnel freezing engineering according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0058] The following will specifically describe the specific scheme of the freezing wall online monitoring method and system for a tunnel freezing engineering provided by the present application in combination with the drawings.

[0059] Please refer to Figure 1FIG. 1 shows a flow chart of a method for tunnel freezing engineering-oriented frozen wall online monitoring method according to an embodiment of the present application, which comprises the following steps:

[0060] Step S1: Obtain temperature time series data at each monitoring point on each freezing pipe.

[0061] The frozen wall is a cylindrical frozen soil structure formed in loose water-bearing strata through artificial refrigeration technology. The formation of the frozen wall depends on the circulation of refrigerants in the freezing pipes, which absorb the heat of the strata, causing the temperature of the surrounding soil to drop below freezing point, thereby forming frozen soil. In the construction of the frozen wall, the liquid supply main pipe is responsible for transporting refrigerants from the refrigeration unit to each freezing pipe, which is the starting point of refrigerant transportation. The freezing pipe is a pipeline for transporting refrigerants (such as low-temperature brine) to the strata, branching from the liquid supply main pipe. The freezing pipes are usually arranged according to a certain layout and spacing to ensure that the refrigerants are evenly distributed to the areas that need to be frozen.

[0062] In the tunnel freezing project, it is crucial to adjust the temperature at different positions of the frozen wall consistently. Uneven temperature distribution can cause differences in the strength and thickness of the frozen wall, forming structural weak links and significantly increasing the risk of water permeation and sand gushing. Therefore, actively adjusting the delivery of frozen liquid can ensure the uniform development of the frozen wall, forming a continuous, complete and design-strength-satisfying closed barrier, which is a key control measure to ensure construction safety and stratum stability.

[0063] Firstly, temperature time series data at each monitoring point on each freezing pipe can be obtained. Specifically, a monitoring point is set every 5 meters on each freezing pipe. On the monitoring point on the circular cross-section, five temperature sensors are installed at equal intervals along the freezing pipe, and the average of the temperature values monitored by the five temperature sensors is taken as the temperature value at the monitoring point. Thus, the temperature time series data at each monitoring point on each freezing pipe is obtained. The collection frequency of the temperature time series data is one minute, and the length can be set to half an hour from the current time.

[0064] It should be noted that the installation interval and number of temperature sensors, the collection frequency and length of temperature time series data can be adjusted according to the implementation scenario, which is not limited here.

[0065] Step S2: At each time, based on the difference characteristics between the temperature values at all monitoring points, and analyzing the amplitude variation trend of the temperature values of each monitoring point within a preset time window, the loose index at each monitoring point is determined; at each time, the fluctuation variation characteristics of the temperature values of all monitoring points within a preset time window are analyzed, and the frozen interference index at each monitoring point is determined.

[0066] The tunnel geological conditions are complex, the loose degree of soil layer is significantly different (such as the junction of water-rich sand layer and hard rock), the freezing process is essentially the process of cold conduction through the soil layer, the loose soil layer has a small contact area between particles, a high porosity and a lower thermal conductivity than the dense soil layer, so in order to make different soil layers reach the same freezing depth, the freezing flow of the soil layer with a higher loose degree needs to be increased to compensate for the heat resistance loss.

[0067] At the same time, if the temperature of a monitoring point is significantly higher than the surrounding, it indicates that the thermal conductivity of the soil layer in this area is poor (possibly due to loose and high gas content). The loose soil layer has a large thermal resistance and slow cold conduction, and the temperature may rise due to heat convection, while the temperature of the dense soil layer drops steeply, so by analyzing the difference between the temperature values of all monitoring points at each time and the amplitude trend of the temperature values of each monitoring point in a preset time window, the loose index of each monitoring point is determined, which is used to reflect the thermal conductivity of the soil layer and provide a correction basis for the subsequent freezing liquid demand calculation.

[0068] Preferably, in an embodiment of the present application, the method for obtaining the loose index comprises:

[0069] Please refer to Figure 2 , which shows the method flowchart of the method for obtaining the loose index in an embodiment of the present application, and the method comprises the following steps:

[0070] Step S201: At each time, the temperature value at each monitoring point is compared with the temperature value at other monitoring points in terms of difference characteristics, so as to determine the first loose factor at each monitoring point.

[0071] For the convenience of explanation and description, an optional monitoring point is taken as the to-be-measured point, and the remaining monitoring points are taken as reference points.

[0072] At each time, the temperature difference between the to-be-measured point and each reference point is calculated as a temperature difference factor, and if the temperature difference factor is greater than 0 and greater, it indicates that the temperature value of the to-be-measured point is higher than that of the reference point, and the thermal conductivity of the to-be-measured point is poorer than that of the reference point, possibly due to loose and high gas content.

[0073] At this time, there is a temperature difference factor between the to-be-measured point and each reference point at each time, and finally, the sum of all temperature difference factors corresponding to each time of the to-be-measured point is normalized as the first loose factor of the to-be-measured point. Based on the foregoing analysis, the greater the first loose factor, the greater the loose degree of the soil layer at the position of the to-be-measured point, and the freezing liquid flow needs to be increased to overcome the heat resistance. Since the temperature difference factor may have positive and negative values, the normalization method here can adopt the function .

[0074] At this point, based on the above method, the first loose factor at each monitoring point at each time can be obtained.

[0075] Step S202: Determine the preset time window corresponding to each time, at each time, analyze the amplitude variation trend of the temperature value of each monitoring point in the preset time window, and determine the second loose factor at each monitoring point.

[0076] Since the loose soil layer is slow in cold conduction, and even possible temperature rebound phenomenon due to thermal convection, at each time, the preset time window of each monitoring point is determined, and the first-order difference sequence of the temperature value sequence is calculated in the preset time window.

[0077] In the first-order difference sequence, the number of positive values is counted as the number of rising factors. The greater the number of rising factors, the more the number of rebound phenomena, and the higher the possibility of loose soil layer. The ratio of the number of rising factors to the total number of values in the first-order difference sequence is taken as the rising proportion factor.

[0078] Finally, the product of the normalized value of the mean of all values in the first-order difference sequence and the normalized value of the rising proportion factor is taken as the second loose factor at each monitoring point. The greater the second loose factor, the greater the degree of soil layer loosening at the location of the monitoring point, and the need to increase the flow of refrigerant to overcome the thermal resistance. Since the values in the first-order difference sequence may be positive or negative, the function .

[0079] Step S203: At each time, the first loose factor and the second loose factor of each monitoring point are fused to obtain the loose index at each monitoring point.

[0080] Based on the analysis in the foregoing steps S201 and S202, the first loose factor and the second loose factor of each monitoring point are positively correlated with the degree of loosening at the monitoring point. Therefore, at each time, the normalized value of the sum of the first loose factor and the second loose factor of each monitoring point is taken as the loose index at each monitoring point, and the greater the loose index, the higher the degree of soil layer loosening, and the greater the need for compensation for the flow of refrigerant in the subsequent process. The normalization is a well-known technical means to those skilled in the art, and the selection of the normalization function can be linear normalization or standard normalization, and the specific normalization method is not limited herein.

[0081] It should be noted that the size of the preset time window in this embodiment of the present application is 5 time points, which is composed of each time point and the 4 time points closest to each time point; in other embodiments, the size of the preset time window can be adjusted according to the implementation scene, which is not limited here.

[0082] In the tunnel freezing engineering, different freezing interferences have different influences on the freezing wall of the frozen liquid conveying pipeline, for example, when the influence of the underground water flow on the freezing wall is significantly greater than the thermal bridge effect, this will cause the temperature change of the position affected by the underground water flow to be more frequent than the position affected by the thermal bridge effect in the same period, so the greater the interference degree, the greater the temperature variability. In order to avoid the frequent and large degree of increase and decrease of the frozen liquid flow caused by the frequent temperature change, when the temperature is adjusted by controlling the frozen liquid flow, the adjustment degree should not be too large. Here, the fluctuation change characteristics of the temperature values of all monitoring points in the preset time window can be analyzed at each time point to determine the freezing interference index at each monitoring point, which is used to quantify the temperature variability.

[0083] Preferably, in one embodiment of the present application, the freezing interference index acquisition method comprises:

[0084] In each time point, the temperature values in the preset time window of each monitoring point are curve fitted to obtain the curve data corresponding to the temperature values. The curve fitting here can use the least square method, which is a known technology and will not be described here.

[0085] In each curve data, the difference between the maximum value and the minimum value is taken as the fluctuation range, and the greater the fluctuation range, the greater the change amplitude of the temperature value in the curve data, that is, the fluctuation is more obvious, and the interference degree is stronger.

[0086] At the same time, since the extreme point is the position where the data change trend changes, if the number of extreme points is greater, it means that the temperature change trend has changed more times, and the fluctuation is more significant, so the number of extreme points in each curve data is taken as the extreme number parameter.

[0087] Then the ratio of the extreme number parameter of each curve data to the maximum value in all extreme number parameters of the curve data is taken as the fluctuation frequency factor, and the greater the fluctuation frequency factor, the greater the fluctuation of the temperature value in the curve data.

[0088] Based on the foregoing analysis, the fluctuation range and the fluctuation frequency factor of each monitoring point are positively correlated with the fluctuation degree of the temperature data thereof, that is, positively correlated with the interference degree. Therefore, in the embodiment of the present application, the product of the fluctuation range and the fluctuation frequency factor corresponding to each monitoring point is normalized, and the value after normalization is taken as the freezing interference index of each monitoring point. The greater the freezing interference index, the more obvious the temperature fluctuation at the monitoring point, and the less suitable the adjustment degree of the refrigerant flow is in subsequent adjustment.

[0089] Step S3: At each time, based on the positional relationship between the monitoring points on the freezing pipe and the liquid supply main, and in combination with the looseness index and the freezing interference index corresponding to each monitoring point, the refrigerant demand index of each freezing pipe is determined. At each time, the preset refrigerant flow value is adjusted according to the refrigerant demand index of each freezing pipe, and the refrigerant correction value of each freezing pipe is obtained.

[0090] In addition to the two indexes calculated in step S2, which can be used for subsequent adjustment of the refrigerant flow, different distances between different positions on the freezing pipe and the liquid supply main will result in different losses of cold energy when the refrigerant circulates in the pipeline and reaches each monitoring point. Therefore, the influence of the loss of cold energy should also be considered when adjusting the refrigerant flow subsequently.

[0091] Therefore, at each time, the positional relationship between the monitoring points on the freezing pipe and the liquid supply main is analyzed, and in combination with the looseness index and the freezing interference index corresponding to each monitoring point, the refrigerant demand index of each freezing pipe is calculated.

[0092] Preferably, in an embodiment of the present application, the method for obtaining the refrigerant demand index comprises:

[0093] For any monitoring point on the freezing pipe, the length of the monitoring point to the liquid supply main along the freezing pipe to which the monitoring point belongs is determined as a distance factor. The greater the distance factor, the farther the distance between the monitoring point and the liquid supply main, and the greater the loss of cold energy, and the greater the demand for refrigerant. Please refer to Figure 3 Fig. 1 shows a schematic diagram of the pipeline arrangement in an embodiment of the present application.

[0094] Since the greater the freezing interference index, the more obvious the temperature fluctuation at the monitoring point, and the less suitable the adjustment degree of the refrigerant flow is in subsequent adjustment, the freezing interference index at each monitoring point is subjected to negative correlation mapping processing to correct the logical relationship, and the cooling demand factor of each monitoring point is obtained. The greater the cooling demand factor, the higher the degree of demand for refrigerant, and the greater the adjustment degree. The negative correlation mapping processing can be performed by using the formula wherein, denotes an exponential function with the natural constant e as the base, and x denotes the independent variable.

[0095] Because the greater the loose index, the higher the degree of looseness of the soil layer, and the greater the need for compensation for the greater flow of chilled liquid in the subsequent process, the product of the normalized value of the cooling demand factor of each monitoring point, the corresponding loose index, and the distance factor, is taken as the cooling demand index of the monitoring point, and the greater the cooling demand index, the greater the cooling demand at the monitoring point, and the greater the degree of flow adjustment of the chilled liquid. The normalization is a technical means familiar to those skilled in the art, and the selection of the normalization function can be linear normalization or standard normalization, and the specific normalization method is not limited herein.

[0096] Then, on each freezing pipe, the number of monitoring points with a cooling demand index greater than a preset cooling demand threshold is counted as a demand quantity factor, and the greater the demand quantity factor, the more monitoring points on the freezing pipe have a high demand for chilled liquid.

[0097] Finally, the product of the mean value of the cooling demand index of all monitoring points on each freezing pipe and the demand quantity factor of each freezing pipe is normalized as the chilled liquid demand index of each freezing pipe, and the greater the chilled liquid demand index of a certain freezing pipe, the greater the flow of chilled liquid passing through the freezing pipe should be. The normalization is a technical means familiar to those skilled in the art, and the selection of the normalization function can be linear normalization or standard normalization, and the specific normalization method is not limited herein.

[0098] It should be noted that the preset cooling demand threshold in the embodiment of the present application is 0.8, and the specific value can be adjusted according to the implementation scenario, which is not limited herein.

[0099] Based on the foregoing steps, the demand degree of each freezing pipe for chilled liquid can be obtained, so that at each moment, the preset chilled liquid flow value can be adjusted according to the chilled liquid demand index of each freezing pipe to obtain a chilled liquid correction value of each freezing pipe.

[0100] Preferably, in an embodiment of the present application, the method for obtaining the chilled liquid correction value comprises:

[0101] The sum of the chilled liquid demand index of each freezing pipe and a preset parameter is taken as a flow adjustment factor, and the greater the flow adjustment factor, the greater the chilled liquid flow required by the freezing pipe. In this embodiment of the present application, in order to prevent over-adjustment, the preset parameter is set to 1.

[0102] Finally, the product of the flow adjustment factor of each freezing pipe and the preset chilled liquid flow value is taken as the chilled liquid correction value of each freezing pipe.

[0103] The preset chilled liquid flow rate value in the embodiment of the present application is set to 10 m³ / h, and the specific flow rate can be set according to the implementation scene, without limitation.

[0104] Step S4: At all times, the chilled liquid correction values of all the freezing pipes are compared on the basis of the degree of disorder of the chilled liquid correction values of all the freezing pipes for monitoring the freezing wall at the current time.

[0105] The chilled liquid correction value reflects the flow rate of the chilled liquid required by each freezing pipe. However, if the chilled liquid correction values required by different freezing pipes differ too much during the whole freezing wall construction process and have lasted for a long time, adjusting the chilled liquid flow rates of different freezing pipes cannot quickly achieve the purpose of adjusting the temperature of the freezing wall to be consistent as soon as possible, and the phenomenon of uneven freezing still occurs. Therefore, in the embodiment of the present application, when monitoring the uniformity of the freezing wall, the degree of disorder of the chilled liquid correction values of the freezing pipes can be analyzed, and the time sequence is traversed forward to analyze the duration of the degree of disorder, and then it is judged whether the chilled liquid circulation of part of the freezing pipes needs to be stopped, so as to achieve the purpose of quick adjustment.

[0106] Preferably, in one embodiment of the present application, at all times, the chilled liquid correction values of all the freezing pipes are compared on the basis of the degree of disorder of the chilled liquid correction values of all the freezing pipes for monitoring the freezing wall at the current time, comprising:

[0107] At each time, the degree of disorder of the chilled liquid correction values of all the freezing pipes is analyzed to determine the chilled liquid flow rate disorder index of the freezing wall. At each time, the standard deviation of the chilled liquid correction values of all the freezing pipes is calculated as a first disorder factor. The first disorder factor can reflect the distribution dispersion degree of the chilled liquid correction values of all the freezing pipes. The greater the value, the more significant the difference between the chilled liquid correction values. At the same time, at each time, the difference between the maximum value and the minimum value of the chilled liquid correction values of all the freezing pipes is calculated as a second disorder factor. The second disorder factor can reflect the numerical range of the chilled liquid correction values of all the freezing pipes. The greater the value, the wider the numerical fluctuation range, and the greater the degree of disorder. Therefore, at each time, the product of the first disorder factor and the second disorder factor after normalization is taken as the chilled liquid flow rate disorder index of the freezing wall at each time. Based on the foregoing analysis, the greater the chilled liquid flow rate disorder index, the more different the chilled liquid correction values required by different freezing pipes at the same time. The normalization is a technical means familiar to those skilled in the art. The selection of the normalization function can be linear normalization or standard normalization, and the specific normalization method is not limited herein.

[0108] Then the time of the chaotic state is evaluated in time sequence and the accumulated fluctuation intensity: from the current time, the historical time is sequentially traversed in time sequence, when the frozen wall frozen liquid distribution chaos index at the traversed time is less than the preset chaos threshold, the traversal is stopped, the time corresponding to the stop is regarded as the end time, the time interval between the current time and the end time is regarded as the chaotic duration, and the sum of the frozen wall frozen liquid distribution chaos index at all traversed times is regarded as the chaos parameter. The greater the chaotic duration, the longer the chaotic situation of the frozen liquid correction value lasts, the greater the chaos parameter, the greater the cumulative fluctuation, and thus the need to pause the frozen liquid delivery to some frozen pipes for balancing the freezing of the frozen wall at all positions.

[0109] The current state of the frozen wall, the duration of the chaotic state of the frozen wall, and the accumulated fluctuation are combined: the product of the chaotic duration, the chaos parameter, and the frozen liquid flow chaos index of the frozen wall at the current time is normalized to obtain the frozen liquid delivery pause evaluation index. The greater the frozen liquid delivery pause evaluation index, the greater the need to pause the frozen liquid delivery at the current time. The normalization is a well-known technique for those skilled in the art, and the normalization function can be linear normalization or standard normalization. The specific normalization method is not limited here.

[0110] Therefore, when the frozen liquid delivery pause evaluation index is greater than the preset pause threshold, in order to faster keep the freezing degree of each position of the frozen wall consistent, the frozen liquid delivery to the frozen pipe with a frozen liquid demand index less than the preset frozen liquid demand threshold is paused in all frozen pipes corresponding to the frozen wall, and the frozen liquid delivery to the frozen pipe with a frozen liquid demand index greater than or equal to the preset frozen liquid demand threshold is performed according to the frozen liquid correction value; otherwise, when the frozen liquid delivery pause evaluation index is less than or equal to the preset pause threshold, the frozen liquid delivery to all frozen pipes according to the frozen liquid correction value is directly performed.

[0111] It should be noted that the preset chaos threshold is 0.6, the preset pause threshold is 0.8, and the preset frozen liquid demand threshold is 0.4. The specific values can be adjusted according to the implementation scenario, and are not limited here.

[0112] In summary, first, the temperature time series data of each monitoring point on each freezing pipe is obtained, which is used to master the temperature dynamics of the water stratum at the position to be frozen. Due to the influence of underground water flow, soil layer, thermal bridge effect and the like, part of the cold energy transported by the freezing pipe will be lost, and the temperature at part of the monitoring points will be lower than that at other positions. Long-term cumulative effect will cause distortion of the shape of the frozen wall. Therefore, by comparing the difference characteristics of the temperature values of the monitoring points at each time and the amplitude change trend of the temperature values of the monitoring points, the looseness index of each monitoring point is obtained, the heat conduction performance of different regions can be more accurately evaluated, and uneven freezing caused by differences in soil conditions is avoided. At the same time, the fluctuation change characteristics of the temperature values of the monitoring points are analyzed, the influence of external interference such as underground water seepage and construction disturbance on the freezing process is effectively identified, and the freezing interference index is calculated. Further, the cold energy loss of the refrigerant is different when the refrigerant reaches different positions in the freezing pipe. Therefore, the position distribution of the monitoring points on the freezing pipe is considered, and the refrigerant demand index of each freezing pipe is determined by combining the looseness index and the freezing interference index, which is used to realize accurate regulation of the refrigerant flow to obtain the refrigerant correction value. By dynamically adjusting the refrigerant flow, the refrigerant supply of each freezing pipe is matched with the actual demand. However, when the refrigerant correction values required by different freezing pipes are quite different, the refrigerant circulation process of part of the freezing pipes should be stopped, because the purpose of adjusting the temperature of the frozen wall of different freezing pipes as soon as possible cannot be achieved by adjusting the flow of different freezing pipes. Therefore, the degree of disorder of the refrigerant correction values of all freezing pipes at all times is analyzed, and the refrigerant correction values of the freezing pipes are compared to monitor the uniformity of the frozen wall.

[0113] The embodiment of the present application also provides a frozen wall online monitoring system for a tunnel freezing project, please refer to Figure 4 which shows a system block diagram, comprising: a data acquisition module 401, used to realize step S1 in the method embodiment; a freezing condition analysis module 402, used to realize step S2 in the method embodiment; a refrigerant flow determination module 403, used to realize step S3 in the method embodiment; and a frozen wall monitoring module 404, used to realize step S4 in the method embodiment.

[0114] It should be noted that the system provided in the above embodiment is only exemplified by the division of the above functional modules, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the computer device is divided into different functional modules to complete all or part of the functions described above. In addition, the frozen wall online monitoring system for a tunnel freezing project and the frozen wall online monitoring method for a tunnel freezing project provided in the above embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0115] Referring to Figure 5 Fig. 1 shows a system structure diagram of a freezing wall online monitoring system for tunnel freezing engineering according to an embodiment of the present application, which comprises a processor 500, a memory 501, a bus 502 and a communication interface 503, and the processor 500, the communication interface 503 and the memory 501 are connected through the bus 502; wherein the memory 501 can contain a high-speed random access memory, the bus 502 can be an ISA bus, a PCI bus or an EISA bus, etc., the processor 500 can be an integrated circuit chip with signal processing capability; the memory 501 stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set are loaded and executed by the processor to realize steps in a freezing wall online monitoring method for tunnel freezing engineering.

[0116] It should be noted that the above-mentioned sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0117] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. Each embodiment mainly describes the difference from other embodiments.

Claims

1. A method for monitoring a frozen wall for a tunnel freezing project, characterized in that, The method comprises: acquiring temperature time series data at each monitoring point on each freeze pipe; at each time, based on the difference characteristics between the temperature values at all monitoring points, and analyzing the amplitude change trend of the temperature values of each monitoring point within a preset time window, determining the looseness index at each monitoring point; at each time, analyzing the fluctuation change characteristics of the temperature values of all monitoring points within a preset time window, to determine the freeze interference index at each monitoring point; at each time, based on the positional relationship between the monitoring points on the freeze pipe and the liquid supply main, and combining the corresponding looseness index and freeze interference index of each monitoring point, the cold liquid demand index of each freeze pipe is determined; at each time, the preset cold liquid flow value is adjusted according to the cold liquid demand index of each freeze pipe to obtain the cold liquid correction value of each freeze pipe; at all times, based on the degree of disorder of the cold liquid correction values of all freeze pipes, the cold liquid correction values of the freeze pipes are compared for freeze wall monitoring at the current time; the method for obtaining the looseness index comprises: at each time, the temperature value at each monitoring point is compared with the temperature value at other monitoring points for difference characteristics, so as to determine the first looseness factor at each monitoring point; determine the preset time window corresponding to each time, at each time, analyze the amplitude change trend of the temperature values of each monitoring point within the preset time window, to determine the second looseness factor at each monitoring point; at each time, the sum of the first looseness factor and the second looseness factor of each monitoring point is normalized, and the value after normalization is taken as the looseness index at each monitoring point; the method for obtaining the freeze interference index comprises: at each time, within the preset time window of each monitoring point, the curve data corresponding to the temperature value is acquired; in each of the curve data, the difference between the maximum value and the minimum value is taken as the fluctuation range; the number of extreme points in each of the curve data is taken as an extreme value parameter, and the ratio of the extreme value parameter of each curve data to the maximum value in all extreme value parameters is taken as a fluctuation frequency factor; determine the freeze interference index at each monitoring point according to the fluctuation range and the fluctuation frequency factor corresponding to each monitoring point, and the fluctuation range and the fluctuation frequency factor are positively correlated with the freeze interference index; the method for obtaining the cold liquid demand index comprises: for any one monitoring point, along the freeze pipe to which the monitoring point belongs, the length from the monitoring point to the liquid supply main is determined as a distance factor; the freeze interference index at the monitoring point is negatively correlated and mapped, and the value after mapping is taken as the cooling demand factor of the monitoring point; the product of the cooling demand factor, the corresponding looseness index and the distance factor of the monitoring point is normalized, and the value after normalization is taken as the cooling demand index of the monitoring point; on each freeze pipe, the number of monitoring points with cooling demand index greater than a preset cooling demand threshold is counted as a demand quantity factor; the product of the mean value of the cooling demand index of all monitoring points on each freeze pipe and the demand quantity factor of each freeze pipe is normalized, and the value after normalization is taken as the cold liquid demand index of each freeze pipe; The method for obtaining the correction value of the refrigerant includes: Taking the sum of the refrigerant demand index of each freeze pipe and the preset parameter as a flow adjustment factor; Taking the product of the flow adjustment factor of each freeze pipe and the preset refrigerant flow value as the refrigerant correction value of each freeze pipe.

2. The method for monitoring the freezing wall in the tunnel freezing project according to claim 1, characterized in that, The method for obtaining the first loose factor includes: Optionally, one monitoring point is taken as a to-be-tested point, and the remaining monitoring points are taken as reference points; At each time point, the temperature value difference between the to-be-tested point and each reference point is calculated as a temperature difference factor; The normalized value of the sum of all temperature value difference factors of the to-be-tested point at each time point is taken as the first loose factor of the to-be-tested point.

3. The method of claim 1, wherein the method is applied to a tunnel freezing project. The method for obtaining the second loose factor includes: At each time point, a first-order difference sequence of the temperature value sequence is calculated within a preset time window of each monitoring point; In the first-order difference sequence, the number of positive values is counted as a rising number factor, and the ratio of the rising number factor to the total number of values in the first-order difference sequence is taken as a rising proportion factor; The product of the normalized value of the mean of all values in the first-order difference sequence and the rising proportion factor is normalized to obtain the second loose factor of each monitoring point.

4. The method of claim 1, wherein the method is applied to a tunnel freezing project. The method for comparing the refrigerant correction values of the freeze pipes on the basis of the degree of disorder of the refrigerant correction values of all freeze pipes at all time points for freeze wall monitoring at the current time point includes: At each time point, the degree of disorder of the refrigerant correction values of all freeze pipes is analyzed to determine a refrigerant flow disorder index of the freeze wall; In time sequence, the time points are sequentially traversed from the current time point, and the traversal is stopped when the refrigerant distribution disorder index of the freeze wall at the time point is less than a preset disorder threshold, the time point corresponding to the stopping is taken as an endpoint time point, the time interval between the current time point and the endpoint time point is taken as a disorder duration, and the sum of the refrigerant distribution disorder indexes of the freeze wall at all traversed time points is taken as a disorder parameter; The normalized value of the product of the disorder duration, the disorder parameter, and the refrigerant flow disorder index of the freeze wall at the current time point is taken as a refrigerant delivery suspension evaluation index; When the refrigerant delivery suspension evaluation index is greater than a preset suspension threshold, the delivery of the refrigerant is suspended for the freeze pipes with a refrigerant demand index less than a preset refrigerant demand threshold among all freeze pipes corresponding to the freeze wall, and the delivery of the refrigerant is performed according to the refrigerant correction value for the freeze pipes with a refrigerant demand index greater than or equal to the preset refrigerant demand threshold; When the refrigerant delivery suspension evaluation index is less than or equal to the preset suspension threshold, the delivery of the refrigerant is performed according to the refrigerant correction value for all freeze pipes.

5. The method for monitoring the freezing wall of the tunnel freezing project according to claim 4, characterized in that, The method for obtaining the refrigerant flow disorder index includes: At each time point, the standard deviation of the refrigerant correction values of all freeze pipes is calculated as a first disorder factor; At each time point, the difference between the maximum value and the minimum value of the refrigerant correction values of all freeze pipes is taken as a second disorder factor; At each time, the normalized value of the product of the first and second chaotic factors is taken as the frozen liquid flow chaotic index of the frozen wall at each time.

6. A freezing wall online monitoring system for a tunnel freezing project, characterized in that, The application relates to a tunnel freezing engineering frozen wall online monitoring method, and comprises a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the processor loads and executes the at least one instruction, the at least one program, the code set or the instruction set to realize the steps of the tunnel freezing engineering frozen wall online monitoring method according to any one of claims 1-5.

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