A monitoring and early warning method suitable for composite heat pipe foundation in permafrost region

Abstract

The present application belongs to the technical field of permafrost foundation engineering detection, and particularly relates to a monitoring and early warning method suitable for a composite heat pipe foundation in a permafrost region. The monitoring and early warning method comprises: arranging temperature sensors, strain sensors and heat flow sensors on the composite heat pipe foundation to collect corresponding monitoring data in real time; calculating temperature, strain and heat flow normalization indexes; constructing a composite heat pipe foundation thawing settlement risk comprehensive evaluation index system; setting a hierarchical early warning mechanism and corresponding level active regulation trigger conditions. The present application provides technical support for the safe operation and maintenance of the composite heat pipe foundation in the permafrost region, solves the problems of insufficient early warning accuracy and imperfect hierarchical early warning system in the traditional monitoring method, can more accurately evaluate the foundation thawing settlement risk and timely take control measures, and provides theoretical and technical support for the long-term service safety of the engineering in the permafrost region.

Description

Technical Field

[0001] This invention belongs to the field of foundation engineering testing technology in permafrost regions, specifically relating to a monitoring and early warning method suitable for composite heat pipe foundations in permafrost regions. Background Technology

[0002] In permafrost regions, foundations are subjected to multiple thermal disturbances during their service life, including climate warming, building heat dissipation, and construction disturbances. This causes the permafrost upper limit to shift downwards and the thermal stability of the permafrost to continuously deteriorate, leading to deformation problems such as soil thaw settlement and uneven ground settlement. Ultimately, this results in a series of engineering defects such as foundation cracking and superstructure deformation. Composite heat pipe foundations, with their efficient heat transfer and thermal regulation characteristics, can regulate the thermal balance of the permafrost surrounding the foundation and effectively inhibit thaw settlement. They are an effective measure for preventing engineering defects in permafrost regions and are now widely used in the construction of roads, buildings, bridges, and other projects in permafrost areas.

[0003] Because the operating conditions of composite heat pipe foundations are influenced by multiple factors such as ambient temperature, geological conditions, and heat pipe status, melt-settlement risks are both hidden and dynamic. Therefore, establishing efficient melt-settlement monitoring and early warning methods has become an urgent need for engineering construction in permafrost regions. Current monitoring technologies still have shortcomings: First, they mostly rely on monitoring single physical quantities, lacking the coordinated acquisition of thermodynamic and mechanical parameters, making it difficult to comprehensively reveal the evolution of melt-settlement risks; second, a scientifically sound risk assessment system has not been established, relying heavily on subjective judgment based on raw data, making quantitative assessment impossible; third, anomaly early warning methods are crude, often using fixed thresholds, easily affected by dynamic environmental fluctuations leading to false alarms and missed alarms, and lacking linkage with heat pipe regulation, making it difficult to achieve integrated management of monitoring, assessment, early warning, and regulation.

[0004] To address the aforementioned issues, there is an urgent need to develop a multi-dimensional, precise, and integrated monitoring and early warning method to solve problems such as the impact of multiple thermal disturbances on composite heat pipe foundations in permafrost regions, the difficulty in controlling the thermal stability of permafrost, the lag in identifying thaw settlement risks, the high rate of misjudgment of anomalies, and the inability to regulate thermal conditions, thereby improving the safety and durability of engineering structures. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a monitoring and early warning method for composite heat pipe foundations in permafrost regions. By using multiple sensors to collaboratively collect data, constructing a risk scoring system that integrates multiple indicators, setting graded early warnings, and coordinating the operation mode of the heat pipe, this method achieves accurate monitoring, dynamic early warning, and proactive prevention and control of melt-settlement risks, thereby improving the operational stability and engineering safety of composite heat pipe foundations.

[0006] S1. Install temperature sensors and strain gauges on the foundation slab, and install heat flow sensors around the heat pipes to acquire the foundation surface temperature in real time. T s (t Annual average ground temperature T cp ,strain e ( t ), heat extraction E cap ( t ); S2. Calculate the temperature normalization index, strain normalization index, and heat flux normalization index; S3. Construct a comprehensive risk scoring system for sinking and melting. R ( t ); S4. Automatic adjustment based on data scrolling. R ( t Risk Score: Calculate the dynamic melt-down comprehensive risk score using data from the most recent time period. R ( t mean m R ; S5. Establish a tiered early warning mechanism. m R <0.3, 0.3≤ m R <0.5, 0.5≤ m R <0.7, m R ≥0.7 corresponds to low risk, medium risk, relatively high risk, and high risk, respectively; S6. Based on the early warning judgment results of the steps, the operation modes of the horizontal heat pipes and vertical heat pipes in the composite heat pipe foundation are linked and controlled to achieve the control of the foundation's thermal condition.

[0007] Preferably, the normalized indices for temperature, heat flux, and strain mentioned in step S2 are calculated as follows: ; ; in, i T (t) is the temperature normalization index; i E (t) is the heat flux normalization index; i S (t) is the strain normalization index; T s ( t The base surface temperature is collected in real time. T cp The annual average ground temperature (usually a negative value); e ∗ Based on the maximum allowable strain; ε( tThis serves as the basis for real-time data acquisition of strain. E cap ( t (This represents the cumulative heat extracted.) E rep Extract the required amount of heat.

[0008] Preferably, the cumulative heat extraction is calculated as follows: ; in, E cap ( t The total amount of heat extracted is expressed in J. or sys The system heat exchange efficiency coefficient; q h The heat extracted per unit length of a horizontal heat pipe, expressed in W / m; N h This refers to the number of horizontal heat pipes. L h This refers to the length of the horizontal heat pipe evaporation section, in meters (m). q v The heat extracted per unit length of a vertical heat pipe, expressed in W / m; N v This refers to the number of vertical heat pipes. L e This is the length of the vertical heat pipe evaporation section, in meters (m).

[0009] Preferably, the required heat extraction is calculated as follows: ; in, k It is the basic equivalent thermal conductivity, with units of W / (m·K); A This refers to the heat exchange area, expressed in m². L The latent heat of phase transition of ice; r This refers to the density of frozen soil, expressed in kg / m³. V The volume of frozen soil that needs to be protected is expressed in m³. x i Ice phase volume fraction.

[0010] Preferably, the comprehensive risk scoring system for melting and sinking described in step S3 R (t) is constructed as follows: ; Among them, temperature weight w T ≥0, deformation rate weight w S ≥0, heat transfer weight w E ≥0, and wT + w S + w E =1.

[0011] Preferably, a rolling baseline algorithm is used for comprehensive risk scoring of meltwater subsidence. R ( t Automatic adjustment is performed, using monitoring data from the most recent time period to calculate a dynamic comprehensive risk score for landslide subsidence. R ( t mean m R .

[0012] Preferably, the mean value obtained from the thawing and settlement critical risk score of permafrost regions and the engineering risk tolerance is combined with the mean value obtained from the tuning in step S4. m R A tiered early warning mechanism has been established, clearly defining the criteria for determining different risk levels, as follows: (1) Low risk: m R <0.3 indicates that the composite heat pipe foundation is operating stably, the surrounding permafrost is in a stable frozen state, and there is no obvious risk of thaw settlement; (2) Medium risk: 0.3≤ m R <0.5 indicates a slight abnormality in the foundation's operating condition, a slight increase in the frozen soil temperature, or slight deformation of the foundation, posing a potential risk of thaw settlement. (3) Higher risk: 0.5≤ m R <0.7 indicates significant abnormalities in foundation operation, accelerated thawing of permafrost, foundation deformation approaching the allowable limit, and a high risk of thaw settlement. (4) High risk: m R A value ≥0.7 indicates a serious abnormality in the foundation's operation, with a large amount of permafrost melting, foundation deformation exceeding the safe range, and a high risk of thaw settlement accidents, requiring emergency treatment.

[0013] Preferably, based on the early warning judgment result of step S5, the operation modes of the horizontal and vertical heat pipes in the composite heat pipe foundation are linked and controlled to achieve active control of the foundation's thermal condition and curb the development of melt-sinking risk. The specific control strategy is as follows: (1) When the risk is determined to be low, maintain the normal operation mode of the horizontal heat pipe and the vertical heat pipe, conduct routine monitoring, and check the operating status of the sensor and heat pipe system regularly. (2) When the risk level is determined to be medium, the monitoring frequency should be increased, and the changing trends of temperature, strain and heat extraction should be analyzed in real time. At the same time, the number of heat pipes should be adjusted appropriately to improve the heat extraction efficiency. (3) When the risk level is determined to be high or high, immediately adjust the spacing and number of horizontal and vertical heat pipes to maximize the heat extraction capacity of the heat pipe system, quickly reduce the temperature of the foundation and surrounding frozen soil, and at the same time activate the emergency monitoring plan, arrange personnel to be on duty on site, and take timely auxiliary measures such as reinforcement and heat pipe installation until the risk level drops to medium risk or below.

[0014] Useful Explanation This invention discloses a monitoring and early warning method for composite heat pipe foundations in permafrost regions, belonging to the field of foundation engineering testing technology. Addressing the technical challenges of composite heat pipe foundations in permafrost regions being susceptible to extreme environmental influences, having difficulty accurately predicting melt-settlement risks, and exhibiting low efficiency in passive control, this invention achieves intelligent and precise control of melt-settlement risks for composite heat pipe foundations through a closed-loop system of multi-parameter precise monitoring, multi-index normalization processing, dynamic risk scoring modeling, and hierarchical early warning and linkage control. Compared to existing technologies, this invention has the following significant advantages: 1. Normalization eliminates dimensional differences and quantifies risk assessment.

[0015] In step S2, this invention constructs three normalized indices: temperature, heat flow, and strain. Through mathematical transformation, it eliminates dimensional differences and numerical magnitude deviations among different physical quantities, converting abstract environmental parameters, structural deformation, and heat exchange efficiency into standardized values ​​within the 0-1 range. This design solves the technical challenge of directly comparing and integrating different types of monitoring data, providing a scientific and unified calculation benchmark for subsequent risk scoring. It avoids assessment distortion caused by differences in data units and magnitudes, significantly improving the accuracy and comparability of risk quantification.

[0016] 2. A comprehensive risk scoring system for financial settlement is used to characterize the risk level.

[0017] In step S3 of this invention, a comprehensive risk scoring system for landslide subsidence is constructed based on normalized indicators. R ( t ), and through temperature weight w T Deformation rate weight w S Heat exchange weight w E Flexible configuration (meeting w T +w S +w E =1), the weight ratio can be adjusted according to the core control needs of different engineering scenarios to achieve a refined and personalized assessment of melting and sinking risks.

[0018] 3. Tiered early warning and coordinated regulation.

[0019] The graded risk and graded linkage heat pipe regulation enables early warning and in-process control, improves basic stability, reduces operation and maintenance costs, and has strong engineering adaptability. Attached Figure Description

[0020] Figure 1 A flowchart illustrating the steps of a monitoring and early warning method for composite heat pipe foundations applicable to permafrost regions; Figure 2 A diagram illustrating a graded early warning mechanism applicable to composite heat pipe foundations in permafrost regions; Figure 3 This is a schematic diagram of a monitoring and early warning method for composite heat pipe foundations applicable to permafrost regions. The composite heat pipe foundation includes A-vertical two-phase closed heat pipe, B-two-phase closed horizontal loop heat pipe, C-foundation, D-temperature-strain monitoring node, and E-heat flow monitoring node. Detailed Implementation

[0021] To more clearly illustrate the objectives, technical solutions, and advantages of this invention, the following section will provide an in-depth analysis and explanation of a monitoring and early warning method for composite heat pipe foundations in permafrost regions, in conjunction with the accompanying drawings and embodiments. The specific implementation methods, structure, features, and effects are detailed below.

[0022] Among them, the appendix Figure 1 A flowchart illustrating the steps of a monitoring and early warning method for composite heat pipe foundations applicable to permafrost regions; attached. Figure 2 This document presents a schematic diagram of a composite heat pipe foundation for a monitoring and early warning method applicable to composite heat pipe foundations in permafrost regions; Appendix Table 1 shows a diagram of a graded early warning mechanism applicable to composite heat pipe foundations in permafrost regions; and clearly marks the relevant components in the system and their installation locations, facilitating the understanding of the monitoring system layout.

[0023] Please see the appendix Figure 1 The document presents a flowchart illustrating the steps of a monitoring and early warning method for composite heat pipe foundations in permafrost regions, as described in this invention. The method includes the following steps: S1. Install temperature sensors and strain gauges on the foundation slab, and install heat flow sensors around the heat pipes to acquire the foundation surface temperature in real time. T s ( t Annual average ground temperature T cp ,strain e ( t ), heat extraction E cap ( t ).

[0024] Preferably, temperature sensors and strain gauges are evenly arranged at 2m×2m intervals on the reinforced concrete base slab of the composite heat pipe foundation. The temperature sensors are PT100 platinum resistance temperature sensors with a measurement range of -50℃ to 80℃ and an accuracy of ±0.1℃, used to collect the real-time temperature of the foundation's bottom surface.T s ( t The strain gauge uses a fiber optic strain gauge with a measurement range of -3000με to 3000με and an accuracy of ±1με, used for real-time acquisition of the basic strain ε. t Used to collect real-time heat flow data around the heat pipe, and then calculate the cumulative heat extraction. E cap ( t In this embodiment T cp =-2.5℃, maximum allowable strain ε of the foundation ∗ =2000με.

[0025] S2. Calculate the temperature normalization index, strain normalization index, and heat flux normalization index.

[0026] Preferred temperature normalization index: ; in, T s ( t The temperature of the base surface (in °C) is collected in real time. T cp =-2.5℃ (annual average ground temperature, negative value); when T s ( t )≤ T cp hour, =0 indicates that the base surface temperature is in a stable frozen state; when T s ( t When ≥0℃, =1 indicates that the surface temperature of the foundation has reached the freezing point, and the permafrost is at risk of thawing; when T cp < T s ( t When <0℃, The value ranges from 0 to 1; the higher the value, the greater the risk of permafrost thawing.

[0027] Preferred strain normalization index: ; in, e ∗ Based on the maximum allowable strain; ε( t This serves as the basis for real-time data acquisition of strain. The value ranges from 0 to 1. The larger the value, the closer the foundation deformation is to the allowable limit, and the higher the risk of melting and settling.

[0028] Preferred heat flux normalization index: ; in, E cap  (t) represents the cumulative heat extracted (unit: J); E rep The required heat to be extracted (unit: J); i E The value of (t) ranges from 0 to 1. The smaller the value, the better the heat pipe system can meet the demand and the more stable the frozen state of the permafrost. The larger the value, the less the heat pipe can meet the demand and the risk of the permafrost melting.

[0029] Calculations need to be performed separately first. E cap (t) and E rep Then substitute into the formula to calculate. i E (t).

[0030] Preferably, the cumulative heat extraction is calculated as follows: ; The parameters are set as follows: system heat exchange efficiency coefficient or sys =0.85; Heat extraction per unit length of a horizontal heat pipe =80W / m, length of horizontal heat pipe evaporation section =12m, number of vertical heat pipes =16 tubes; q units of vertical heat pipes can extract heat per unit length. v =100W / m, length of vertical heat pipe evaporation section =8m, number of vertical heat pipes Nv=20; t is the collection time (unit: s).

[0031] Preferably, the required heat extraction is calculated as follows: ; The parameters are set as follows: basic equivalent thermal conductivity k =1.8w / (m·k); heat exchange area A =36m²; latent heat of phase change of ice L =334kJ / kg; density of frozen soil r =1900 kg / m³; Volume of frozen soil requiring protection V =288m³; Ice phase volume fraction x i =0.6; T s (t) represents the real-time base surface temperature. T cp=-2.5℃, t This refers to the data collection time.

[0032] S3. Construct a comprehensive risk scoring system for sinking and melting. R ( t ).

[0033] Preferably, the comprehensive risk scoring system for melting and sinking described in step S3 R ( t ) Construct as follows: ; Among them, temperature weight w T ≥0, deformation rate weight w S ≥0, heat transfer weight w E ≥0, and w T + w S + w E =1. Each weight can be adjusted based on the actual working conditions, such as geological conditions, engineering grade, and permafrost type in the permafrost region, to ensure the relevance and accuracy of the risk assessment (initial weight can be set to 1). w T =0.4, w S =0.3, w E =0.3). For example, in areas with poor permafrost stability, the temperature weight can be increased. w T and strain weight w S In areas where heat pipe systems play a crucial role in permafrost protection, the heat transfer weight can be increased. w E .

[0034] S4. Automatic adjustment based on data scrolling. R ( t Risk Score: Calculate the dynamic melt-down comprehensive risk score using data from the most recent time period. R mean of (t) m R S5. Set up a tiered early warning mechanism, see attached document. Figure 2 As shown.

[0035] Preferably, a risk level for thaw settlement in permafrost regions is set, as follows: (1) Low risk: m R<0.3 indicates that the composite heat pipe foundation is operating stably, the surrounding permafrost is in a stable frozen state, and there is no obvious risk of thaw settlement; (2) Medium risk: 0.3≤ m R <0.5 indicates a slight abnormality in the foundation's operating condition, a slight increase in the frozen soil temperature, or slight deformation of the foundation, posing a potential risk of thaw settlement. (3) Higher risk: 0.5≤ m R <0.7 indicates significant abnormalities in foundation operation, accelerated thawing of permafrost, foundation deformation approaching the allowable limit, and a high risk of thaw settlement. (4) High risk: m R A value ≥0.7 indicates a serious abnormality in the foundation's operation, with a large amount of permafrost melting, foundation deformation exceeding the safe range, and a high risk of thaw settlement accidents, requiring emergency treatment.

[0036] In this embodiment, the mean value obtained by tuning m R ≈0.55, satisfying 0.5≤ m R The risk level of melting and settling of the composite heat pipe foundation during this period is determined to be high, given the condition that the risk level is <0.7. The monitoring terminal immediately issues a high-risk warning signal to notify relevant maintenance personnel and displays the warning level, real-time monitoring data, and risk analysis report on the monitoring interface.

[0037] S6. Based on the early warning judgment results of the steps, the operation modes of the horizontal heat pipes and vertical heat pipes in the composite heat pipe foundation are linked and controlled to achieve the control of the foundation's thermal condition.

[0038] Preferably, based on the early warning judgment result (higher risk) of S5, the monitoring terminal automatically links and adjusts the operation mode of the horizontal heat pipe and the vertical heat pipe in the composite heat pipe foundation to control the thermal condition of the foundation and curb the development of melting and sinking risk.

[0039] Based on the same inventive concept as the above method, this embodiment of the invention also provides a layout diagram of a composite heat pipe foundation suitable for permafrost regions, which includes: a foundation, a heat pipe, a temperature sensor, a strain gauge, and a heat flow sensor.

[0040] Preferably, the layout diagram of a composite heat pipe foundation suitable for permafrost regions provided in this embodiment of the invention is attached. Figure 3 As shown.

[0041] In summary, this invention effectively solves the technical difficulties of existing technologies in permafrost regions, such as single monitoring dimensions, low early warning accuracy, and lack of dynamic control capabilities, through multi-sensor collaborative data acquisition, multi-index normalization processing, construction of a comprehensive risk scoring system for melt-settlement, hierarchical early warning, and coordinated control of heat pipes. It achieves accurate monitoring, dynamic early warning, and proactive prevention and control of melt-settlement risks, significantly improving the operational stability and engineering safety of composite heat pipe foundations. It can be widely applied to melt-settlement risk prevention and control projects for various composite heat pipe foundations in permafrost regions such as the Qinghai-Tibet Plateau and Northeast China, and has good engineering application value and promotion prospects.

[0042] The above provides a detailed description of a monitoring and early warning method for composite heat pipe foundations in permafrost regions, as provided by the present invention. Specific embodiments further illustrate the principles and implementation methods of the invention. It should be noted that the above embodiments are provided only to facilitate understanding of the method and its core concept, and are not intended to limit the invention. Those skilled in the art can make various improvements and modifications to the above method without departing from the basic principles of the invention. All improvements, modifications, and equivalent substitutions made based on the principles of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A monitoring and early warning method for composite heat pipe foundations in permafrost regions, characterized in that, Includes the following steps: S1. Install temperature sensors and strain gauges on the foundation slab, and install heat flow sensors around the heat pipes to obtain the temperature of the foundation slab in real time. T s ( t Annual average ground temperature T cp ,strain ε ( t ), heat extraction E cap ( t ); S2. Calculate the temperature normalization index, strain normalization index, and heat flux normalization index; S3. Construct a comprehensive risk scoring system for sinking and melting. R ( t ); S4. Automatic adjustment based on data scrolling. R ( t Risk Score: Calculate the dynamic melt-down comprehensive risk score using data from the most recent time period. R ( t mean μ R ; S5. Establish a tiered early warning mechanism. μ R <0.3, 0.3≤ μ R <0.5, 0.5≤ μ R <0.7, μ R ≥0.7 corresponds to low risk, medium risk, relatively high risk, and high risk, respectively; S6. Based on the early warning judgment result of step S5, the operation modes of the horizontal heat pipe and the vertical heat pipe in the composite heat pipe foundation are linked and controlled to realize the control of the foundation thermal condition.

2. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 1, characterized in that, The temperature sensor, strain gauge, and heat flow sensor mentioned in step S1 are all waterproof and low-temperature resistant models, suitable for extreme environmental conditions in permafrost regions.

3. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 1, characterized in that, The normalization index mentioned in step S2 is calculated as follows: ； ； in, θ T (t) is the temperature normalization index; θ E (t) is the heat flux normalization index; θ S (t) is the strain normalization index; T cp The annual average ground temperature (usually a negative value); ε ∗ Based on the maximum allowable strain; E cap (t) represents the cumulative heat extracted; E rep Extract the required amount of heat.

4. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 3, characterized in that, The E cap (t) is calculated as follows: ； in, E cap (t) Cumulative heat extracted, in J; η sys The system heat exchange efficiency coefficient; q h The heat extracted per unit length of a horizontal heat pipe, expressed in W / m; N h This refers to the number of horizontal heat pipes. L h This refers to the length of the horizontal heat pipe evaporation section, in meters (m). q v The heat extracted per unit length of a vertical heat pipe, expressed in W / m; N v This refers to the number of vertical heat pipes. L e This is the length of the vertical heat pipe evaporation section, in meters (m).

5. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 3, characterized in that, The required heat extraction E rep Calculate as follows: ； in, k It is the basic equivalent thermal conductivity, with units of W / (m·K); A This refers to the heat exchange area, expressed in m². L The latent heat of phase transition of ice; ρ This refers to the density of frozen soil, expressed in kg / m³. V The volume of frozen soil that needs to be protected is expressed in m³. ξ i Ice phase volume fraction.

6. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 1, characterized in that, In step S3, the comprehensive risk scoring system for melt-settlement is constructed by weighted summation of normalized indices of temperature, strain, and heat flux. The dynamic comprehensive risk score for melt-settlement is calculated as follows: ； Among them, temperature weight w T ≥0, deformation rate weight w S ≥0, heat transfer weight w E ≥0, and w T + w S + w E =1.

7. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 1, characterized in that, The automatic adjustment process based on rolling data described in step S4 is as follows: using data from the most recent time period, calculate the average of the comprehensive risk score for landslide subsidence. μ R At the same time, it identifies and removes outliers in the monitoring data caused by environmental fluctuations and sensor deviations, thus avoiding misjudgment.

8. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 1, characterized in that, In step S5, the graded early warning mechanism is set as follows based on the critical risk score for thaw settlement in permafrost regions and the engineering risk tolerance: μ R ＜0.3，0.3≤ μ R ＜0.5，0.5≤ μ R ＜0.7， μ R ≥0.7 ； The above formulas correspond to low risk, medium risk, relatively high risk, and high risk, respectively.

9. The monitoring and early warning method for composite heat pipe foundations in permafrost regions according to claim 8, characterized in that, When the risk level is determined to be low, routine monitoring is conducted; when the risk level is determined to be medium, the monitoring frequency is increased and the changing trends are analyzed. When the risk level is determined to be high or high, adjust the spacing and number of horizontal and vertical heat pipes to improve the heat extraction capacity of the heat pipe system and reduce the temperature of the foundation and surrounding frozen soil.

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