Water conservancy mass concrete temperature control optimization method

Abstract

This invention provides a method for optimizing temperature control in large-volume hydraulic concrete, relating to the field of computer-aided engineering technology. The invention corrects the initial temperature field of the finite element model based on measured temperature values ​​and dynamically determines the candidate range of cooling water inlet temperature according to the current cooling rate, ensuring that each candidate range adapts to the cooling requirements. It achieves an accurate calculation starting point without laboratory testing, shortening the optimization cycle and reducing costs. By pairing candidate inlet water temperature values ​​with thermal resistance values ​​and substituting them into the finite element model to predict the temperature field, it determines the temperature safety margin, temperature difference safety margin, and temperature fluctuation stability index, using these three indices to evaluate the temperature control effect. This avoids the risk of sudden temperature drops caused by a single criterion. By selecting the feasible combination with the smallest deviation between the predicted temperature and the target control temperature as the target temperature control parameter, it achieves refined selection for each time period, ensuring that the internal temperature approaches the preset cooling target and that the cooling process proceeds smoothly.

Description

Technical Field

[0001] This invention relates to the field of computer-aided engineering technology, specifically to a method for optimizing temperature control in large-volume hydraulic concrete. Background Technology

[0002] After large-volume concrete is poured, the cement hydration reaction releases a large amount of heat. Due to the large volume of concrete and its poor thermal conductivity, the internal heat is difficult to dissipate in time, resulting in a significantly higher internal temperature than the surface temperature. When the temperature difference between the inside and outside is too large, the resulting thermal tensile stress exceeds the early tensile strength of the concrete, which will cause temperature cracks. This seriously affects the safety and durability of the engineering structure. Therefore, in the construction of large-volume concrete, it is necessary to optimize temperature control parameters such as the spacing of cooling water pipes, water flow rate, water temperature, and insulation layer thickness to control the maximum internal temperature of the concrete and the temperature difference between the inside and outside within the safe limits.

[0003] In the prior art, CN110728093A discloses a method for optimizing temperature control of large-volume concrete. This method involves collecting on-site temperature and displacement history data, then pouring test concrete specimens into a dedicated concrete temperature-constrained stress testing device according to the on-site mix proportions. The collected data is input into the device to simulate real temperature changes and displacement histories in the laboratory. The device's displacement constraint system is then activated to conduct temperature stress tests with different degrees of constraint, obtaining the concrete's constraint stress history and tensile strength parameters. These are then repeatedly compared with the test values ​​using a finite element model to invert and obtain the concrete's true elastic modulus, linear expansion coefficient, creep coefficient, and other material parameters. Finally, the inverted parameters are imported into the actual structural finite element model to calculate the cracking risk coefficient, and the temperature history output by the testing device is iteratively adjusted until the crack resistance requirements are met.

[0004] However, the aforementioned existing technologies have the following shortcomings: Concrete specimens are prepared by on-site mixing and temperature and displacement history is simulated in the laboratory. Temperature stress tests and axial tensile tests with different degrees of constraint are carried out to invert material parameters. This process requires specialized testing equipment and the test cycle covers the entire age of the concrete, which cannot meet the real-time adjustment needs of temperature control schemes on the construction site.

[0005] Existing technologies use the ratio of the calculated constraint stress to the tensile strength as the cracking risk coefficient. When the coefficient does not meet the requirements, the temperature history is repeatedly adjusted and recalculated. However, the stability of temperature change during the cooling process is not quantitatively analyzed and constrained. If the cooling rate is too fast or the temperature jumps drastically in adjacent time periods, uneven thermal stress distribution will be generated inside the concrete, increasing the risk of cracking.

[0006] The process of concrete cooling from its peak hydration heat temperature to its target final temperature involves multiple stages. The hydration heat release rate, internal temperature state, and external environmental influences are all different in each stage. Existing technologies have not established a temperature control period segmentation mechanism, nor have they dynamically determined a reasonable combination range of cooling water inlet temperature and insulation measures based on the actual cooling requirements of different periods.

[0007] The comparison file requires a complete finite element modeling and nonlinear iterative solution after each temperature history adjustment. It does not utilize known engineering information such as the cooling rate to preliminarily screen the feasible combination range of cooling water inlet temperature and thermal resistance of insulation material, resulting in a large number of unnecessary finite element analysis calculations, which makes it difficult to meet the computational efficiency requirements of real-time optimization on site.

[0008] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a method for optimizing temperature control of large-volume hydraulic concrete to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: A method for optimizing temperature control of large-volume hydraulic concrete, comprising the following steps: Establish a finite element model of the temperature field of the target concrete structure, obtain the maximum internal temperature limit and the internal-external temperature difference limit of the target large-volume concrete structure, and collect the measured temperature values ​​of each temperature monitoring point at the beginning of the temperature control period. The temperature monitoring points include internal monitoring points and surface monitoring points. Based on the measured temperature values ​​at each temperature monitoring point, the initial temperature field of the finite element model during the temperature control period is corrected. Based on the temperature drop between the measured temperature values ​​at the internal monitoring points at the beginning of the temperature control period and the target control temperature at the end of the temperature control period, the candidate range of cooling water inlet temperature during the temperature control period is determined. Multiple inlet water temperature values ​​are selected within the candidate range of cooling water inlet temperature, and multiple thermal resistance values ​​are selected within the range of thermal resistance values ​​of insulation material. Multiple inlet water temperature values ​​and multiple thermal resistance values ​​are paired to form multiple candidate temperature control parameter combinations. Substitute each candidate temperature control parameter combination into the finite element model to predict the temperature field, and obtain the predicted temperature trajectory of the internal monitoring point and surface monitoring point corresponding to each candidate temperature control parameter combination during the current temperature control period. Based on the predicted temperature trajectory, determine the temperature safety margin, temperature difference safety margin, and temperature fluctuation stability index corresponding to each candidate temperature control parameter combination, and take the candidate temperature control parameter combination that meets the preset requirements as the feasible temperature control parameter combination. From the feasible temperature control parameter combinations, select the candidate temperature control parameter combination with the smallest absolute value of the deviation between the predicted temperature of the internal monitoring point and the target control temperature at the end of the current temperature control period as the target temperature control parameter for the current temperature control period.

[0011] Furthermore, correcting the initial temperature field of the finite element model during the temperature control period includes: assigning the measured temperature values ​​of each temperature monitoring point to the corresponding positions in the finite element model, and calculating the temperature of the remaining positions based on the temperature of each corresponding position to form the initial temperature field of the current period. When estimating the temperature at other locations, the temperature distribution is estimated based on the spatial relationship between each temperature monitoring point and the other locations.

[0012] Furthermore, for each of the remaining locations, an influence range is defined with the remaining location as the center and a preset influence radius is used to filter out temperature monitoring points located within the influence range; Calculate the spatial distance between the remaining location and each selected temperature monitoring point, use the reciprocal of the spatial distance as the initial weight of each selected temperature monitoring point to the remaining location, and perform normalization to obtain the influence weight of each selected temperature monitoring point. The measured temperature values ​​of each selected temperature monitoring point are weighted and averaged according to the corresponding influence weights to obtain the estimated temperature values ​​of the remaining locations.

[0013] Furthermore, based on the temperature drop, a candidate range for the cooling water inlet temperature during the temperature control period is determined, including: A preset range of cooling water inlet temperature is obtained, wherein the preset range has a preset upper limit and a preset lower limit, and the preset lower limit is used as the lower limit of the candidate range. The cooling range is compared with a preset benchmark cooling range. If the cooling range is less than or equal to the benchmark cooling range, the preset upper limit value is used as the upper limit value of the candidate range. If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the product of the excess amount and the preset adjustment coefficient is subtracted from the preset upper limit value to obtain the upper limit value of the candidate range. If the result of the subtraction is lower than the preset lower limit, then the preset lower limit is used as the upper limit of the candidate range.

[0014] Furthermore, multiple inlet water temperature values ​​are paired with multiple thermal resistance values ​​to form multiple candidate temperature control parameter combinations, specifically including: Within the candidate range of cooling water inlet temperature, multiple inlet temperature values ​​are selected at equal intervals according to the preset inlet temperature step size. Within the range of thermal resistance values ​​of insulation material, multiple thermal resistance values ​​are selected at equal intervals according to the preset thermal resistance step size. Each selected inlet water temperature value is combined with each selected thermal resistance value to obtain multiple sets of temperature control parameter combinations. The minimum allowable thermal resistance value is determined based on the temperature drop range. The thermal resistance value in each group of temperature control parameter combinations is compared with the minimum allowable thermal resistance value. Temperature control parameter combinations with thermal resistance values ​​lower than the minimum allowable thermal resistance value are eliminated, and temperature control parameter combinations that meet the conditions are retained as candidate temperature control parameter combinations.

[0015] Furthermore, the minimum allowable thermal resistance value is determined based on the temperature drop, specifically including: Obtain a preset reference cooling range and a reference thermal resistance value, and compare the cooling range with the reference cooling range; If the cooling range is less than or equal to the reference cooling range, then the reference thermal resistance value shall be used as the minimum allowable thermal resistance value. If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the reference thermal resistance value is added to the product of the excess amount and the preset adjustment coefficient to obtain the minimum allowable thermal resistance value.

[0016] Furthermore, based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the internal peak temperature within the current temperature control period is determined, and the difference between the preset maximum temperature limit and the internal peak temperature is the corresponding temperature safety margin. Based on the predicted temperature trajectories of the internal monitoring points and the surface monitoring points corresponding to each candidate temperature control parameter combination, the maximum internal and external temperature difference within the current temperature control period is determined. The maximum internal and external temperature difference is subtracted from the preset internal and external temperature difference limit, and the resulting difference is the corresponding temperature difference safety margin.

[0017] Furthermore, based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the sequence of the highest temperature value of the internal monitoring points changing with time is arranged in chronological order, the absolute value of the temperature change between two adjacent times is calculated, and the maximum value of the absolute value of the temperature change among all adjacent times is taken as the temperature fluctuation stability index. Candidate temperature control parameter combinations that meet preset requirements for temperature safety margin, temperature difference safety margin, and temperature fluctuation stability are selected as feasible temperature control parameter combinations.

[0018] Furthermore, determine whether the current temperature control period is the last temperature control period in the entire cooling process; If it is the last temperature control period, then the target temperature control parameter is selected according to the method of minimizing the absolute value of the deviation; If it is not the last temperature control period, then from the feasible temperature control parameter combinations, select the set in which the predicted temperature of the internal monitoring point at the end of the current temperature control period is lower than the target control temperature, and the absolute value of the deviation is the smallest, as the target temperature control parameter for the current temperature control period.

[0019] Furthermore, when selecting the target temperature control parameter for the current temperature control period from the feasible temperature control parameter combinations, if there are multiple feasible temperature control parameter combinations with equal absolute deviation values, then the combination with the smallest temperature fluctuation stability index is selected as the target temperature control parameter for the current temperature control period.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention corrects the initial temperature field of the finite element model during the temperature control period based on the measured temperature values ​​of each temperature monitoring point, and dynamically determines the candidate range of cooling water inlet temperature based on the cooling amplitude of the current temperature control period. This allows different temperature control periods to adapt to the corresponding candidate range according to the actual cooling requirements, without relying on laboratory tests, to obtain an accurate calculation starting point and a reasonable parameter search space, thus shortening the optimization cycle and reducing implementation costs.

[0021] This invention also forms candidate temperature control parameter combinations by pairing inlet water temperature values ​​and thermal resistance values ​​within the candidate range, and substitutes them into a finite element model to predict the temperature field. It also determines the temperature safety margin, temperature difference safety margin, and temperature fluctuation stability index corresponding to each combination. The temperature control effect is evaluated by using three indicators, avoiding the risk of cracking caused by excessively fast cooling rate or sudden temperature drop that may result from screening based on a single criterion.

[0022] The present invention also selects the combination with the smallest absolute value of the deviation between the predicted temperature of the internal monitoring point and the target control temperature at the end of the current temperature control period from the feasible temperature control parameter combinations as the target temperature control parameter for the current temperature control period, thereby realizing the fine selection of temperature control parameters for each period, ensuring that the internal temperature at the end of each period accurately approaches the preset cooling target, and making the entire cooling process proceed smoothly according to the predetermined rhythm. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 This is a schematic diagram comparing the internal temperature drop in this embodiment. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0026] Example: Please see Figure 1 The present invention provides a technical solution: A method for optimizing temperature control of large-volume hydraulic concrete, comprising the following steps: Step 1: Establish a finite element model of the temperature field of the target concrete structure, obtain the maximum internal temperature limit and the internal-external temperature difference limit of the target large-volume concrete structure, and collect the measured temperature values ​​of each temperature monitoring point at the beginning of the temperature control period. The temperature monitoring points include internal monitoring points and surface monitoring points. The maximum internal temperature limit is used to determine whether the concrete interior will be damaged due to excessive temperature, while the internal and external temperature difference limit is used to determine whether cracks will occur due to excessive temperature difference.

[0027] In this embodiment, the temperature control period refers to any period during which temperature control adjustment is required. The entire cooling process begins after the internal temperature of the concrete reaches the peak of the heat of hydration and ends when the temperature drops to the target final temperature. During this period, it is divided into multiple consecutive temperature control periods. Each temperature control period independently executes steps 1 to 6 to determine the target temperature control parameters corresponding to that period. After the current temperature control period ends, the measured temperature value at the end of that period is used as the starting data for the next temperature control period, and the temperature control optimization for the next period continues until the internal temperature of the concrete drops to the target final temperature.

[0028] For each temperature monitoring point, the vertical distance from the monitoring point to the nearest surface boundary of the concrete structure is calculated, resulting in a set of distance values ​​for all monitoring points. This set of distance values ​​is then sorted, and starting from the end with the smallest distance, different distance values ​​are used as candidate thresholds to divide the monitoring points one by one. The degree of temperature difference between the internal monitoring point set and the surface monitoring point set divided under each candidate threshold is calculated. The candidate threshold that maximizes the degree of temperature difference between the two types of monitoring points is selected as the preset distance threshold. For differences in monitoring point layout schemes and structural dimensions in different projects, the specific value of the preset distance threshold can be directly input for adaptation without changing the execution logic of the method itself.

[0029] In this embodiment, the preset distance threshold is set to 0.5 meters. For concrete structures with a small thickness and thin cross section, the threshold can be appropriately reduced. For large structures with an ultra-thick cross section, the threshold can be appropriately increased. The specific value can be determined according to the actual engineering situation. Based on the vertical distance of each temperature monitoring point, if the distance is less than or equal to the preset distance threshold, the temperature monitoring point is classified as a surface monitoring point. If the distance is greater than the preset distance threshold, the monitoring point is classified as an internal monitoring point.

[0030] Temperature monitoring points closer to the surface boundary are significantly affected by environmental heat dissipation, and their temperature changes closely resemble the temperature characteristics of the concrete surface area. Therefore, they are classified as surface monitoring points to reflect the surface temperature status. Temperature monitoring points farther from the surface boundary are located in the core area inside the concrete. They are greatly affected by the heat of hydration and dissipate heat slowly, and their temperature changes reflect the internal temperature characteristics. Therefore, they are classified as internal monitoring points. In step 4, it is necessary to extract the highest temperature of the internal monitoring points and the lowest temperature of the surface monitoring points separately, and calculate the temperature difference between the inside and outside. Only by classifying the monitoring points into two categories according to the above classification rules can these two data points be clearly extracted from the predicted temperature trajectory.

[0031] Step 2: Based on the measured temperature values ​​of each temperature monitoring point, correct the initial temperature field of the finite element model during the temperature control period. Based on the temperature drop between the measured temperature values ​​of the internal monitoring points at the beginning of the temperature control period and the target control temperature at the end of the temperature control period, determine the candidate range of cooling water inlet temperature during the temperature control period. Correcting the initial temperature field of the finite element model during the temperature control period includes: assigning the measured temperature values ​​of each temperature monitoring point to the corresponding position in the finite element model, and calculating the temperature of the remaining positions based on the temperature of each corresponding position to form the initial temperature field of the current period. Before starting the calculation, each spatial location in the finite element model needs an initial temperature value. Temperature monitoring points have clearly defined embedded locations in the concrete structure. The measured temperatures at these locations are real and reliable known data. By directly assigning the measured temperature values ​​to the corresponding locations in the model, the temperatures at these known locations can be completely consistent with the actual situation, providing an accurate temperature reference for the entire model.

[0032] The number of temperature monitoring points is limited, covering only a few locations in the concrete structure. Most locations in the finite element model do not have corresponding measured temperature values. Without calculation, the initial temperature values ​​at these locations will be unknown, making it impossible to form a complete initial temperature field. Through calculation, the temperature values ​​at all other locations can be estimated using the known temperature values ​​of the monitoring points, forming a complete and continuous full-field initial temperature field.

[0033] When estimating the temperature at other locations, the temperature distribution is estimated based on the spatial relationship between each temperature monitoring point and the other locations.

[0034] The internal temperature of concrete is continuously distributed in space. The closer the distance between two locations, the closer their temperatures are; the farther apart they are, the greater the temperature difference may be. Using the spatial distance between the temperature monitoring point and the location to be estimated as a weighting criterion, the temperature monitoring point that is closer to the location to be estimated contributes more to the temperature of the location to be estimated, while the one that is farther away contributes less. This estimation method conforms to the physical laws of heat conduction and can accurately restore the true temperature distribution state inside the concrete.

[0035] For each of the remaining locations, an influence range is defined with the remaining location as the center and a preset influence radius is used to filter out temperature monitoring points located within the influence range; When extrapolating the temperature at an unknown location, not all temperature monitoring points have a significant impact on that location. The temperature values ​​of monitoring points far away from the location have a weak correlation with the actual temperature at that location. If all monitoring points are included in the calculation, it will not only increase the amount of calculation but may also introduce interference from irrelevant information. By defining an area of ​​influence centered on the location and focusing only on monitoring points within a certain range around it, the extrapolation can be more focused on the data that truly has an impact.

[0036] The radius of influence is a pre-set distance value. Based on the total number of temperature monitoring points and the geometric dimensions of the concrete structure, the principle is to ensure that at least three temperature monitoring points can be selected within the influence range of any location to be calculated. Different candidate values ​​are substituted into the finite element model for trial calculations, and the candidate value with the highest calculation accuracy is selected as the radius of influence. In this embodiment, the radius of influence is preset to 4.0 meters, which is applicable to all other locations. When the number of temperature monitoring points selected within the influence range of a certain other location is less than three, the radius of influence of that location is temporarily expanded to 5.0 meters, and the selection is re-selected to ensure that the number of monitoring points participating in the weighted calculation is not less than three, so as to ensure the reliability of the temperature calculation.

[0037] By defining the influence range and screening temperature monitoring points within it, the temperature calculation for each location to be estimated relies only on the most relevant monitoring data in its vicinity, avoiding interference from irrelevant data from afar. This improves the local accuracy and calculation efficiency of temperature estimation. At the same time, the preset uniform influence radius ensures that the screening rules for all locations are consistent, and the calculated initial temperature field is spatially continuous and smooth, conforming to the physical laws of temperature distribution inside concrete.

[0038] Calculate the spatial distance between the remaining location and each selected temperature monitoring point, use the reciprocal of the spatial distance as the initial weight of each selected temperature monitoring point to the remaining location, and perform normalization to obtain the influence weight of each selected temperature monitoring point. The reciprocal of spatial distance directly reflects the physical law that the closer the distance, the greater the influence. As the distance increases, the weight decreases rapidly. This is consistent with the law that the influence of temperature decreases with increasing distance in heat conduction. Using the reciprocal form is simple to calculate, does not require additional parameters, and has an intuitive physical meaning.

[0039] The initial weights of each monitoring point are calculated directly based on the reciprocal of the distance. The sum of these initial weights is usually not equal to 1. If normalization is not performed, the temperature value obtained by direct weighted average will deviate from the actual temperature range. The normalization process divides the initial weight of each temperature monitoring point by the sum of all initial weights, so that the sum of the influence weights after processing is equal to 1. In this way, the temperature value after weighted average will definitely be between the minimum and maximum values ​​of the temperature of each monitoring point, without abnormal deviation, thus ensuring the mathematical rationality of the calculation results.

[0040] The measured temperature values ​​of each selected temperature monitoring point are weighted and averaged according to the corresponding influence weights to obtain the estimated temperature values ​​of the remaining locations.

[0041] Multiplying the measured temperature value of each temperature monitoring point by its corresponding influence weight and then summing them allows nearby monitoring points to contribute more to the final result, while those farther away contribute less, making the calculated result more consistent with reality. In this scheme, the temperature of each of the remaining locations is unknown, but the temperatures of the surrounding temperature monitoring points are known. By using a weighted average, multiple known temperature values ​​can be combined into a unified calculated value, and this calculated value must be between the lowest and highest temperatures of the temperature monitoring points involved in the calculation, without any abnormal results exceeding the known temperature range. This method has a simple calculation process, which can be completed using only known spatial locations and temperature values.

[0042] All known temperature monitoring points and other locations together constitute a complete and continuous initial temperature field. This temperature field is faithful to the measured temperature values ​​of the temperature monitoring points and has a smooth spatial transition, providing an accurate starting point for subsequent finite element transient heat conduction analysis.

[0043] The candidate range for the cooling water inlet temperature during the temperature control period is determined based on the temperature drop rate, including: A preset range of cooling water inlet temperature is obtained, wherein the preset range has a preset upper limit and a preset lower limit, and the preset lower limit is used as the lower limit of the candidate range. The cooling water inlet temperature has a preset range determined by the equipment capacity, including an upper limit and a lower limit. The lower limit is the lowest inlet water temperature that the cooling system can provide, which is determined by the refrigeration unit's capacity. No matter how large the cooling demand is, the inlet water temperature cannot be lower than this lower limit. Therefore, the preset lower limit is directly used as the lower limit of the candidate range to ensure that the candidate range is always within the equipment capacity range.

[0044] The cooling range is compared with a preset benchmark cooling range. If the cooling range is less than or equal to the benchmark cooling range, the preset upper limit value is used as the upper limit value of the candidate range. The baseline cooling range is the amount of temperature reduction that concrete can achieve in the current period without active cooling water circulation, relying solely on natural surface heat dissipation and the concrete's own heat capacity. When the actual required cooling range does not exceed the baseline value, it means that active water cooling is not necessary, and the inlet water temperature can be set to the preset upper limit value. Even the weakest cooling capacity can meet the requirements. When the actual cooling range exceeds the baseline value, the excess must be carried away by active cooling water circulation. The inlet water temperature needs to be adjusted downward from the preset upper limit value. The greater the excess, the larger the adjustment range.

[0045] The baseline cooling range is a fixed value calculated in advance using a finite element model. Before officially starting optimization, a separate simulation is performed using the finite element model. The cooling water inlet temperature is set to the highest value that the equipment can provide, and the thermal resistance of the insulation material is set to the median value within the range. All other conditions remain unchanged. The initial temperature field uses the measured temperature value at the beginning of the current temperature control period. Finite element analysis is performed, and the highest internal monitoring point temperature value at the end of the current temperature control period is extracted from the analysis results. The difference between the highest measured internal monitoring point temperature at the beginning of the current temperature control period and the highest temperature value at the end of the period is the preset baseline cooling range.

[0046] If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the product of the excess amount and the preset adjustment coefficient is subtracted from the preset upper limit value to obtain the upper limit value of the candidate range. The excess amount refers to the additional temperature reduction that needs to be achieved through active cooling. For every 1°C decrease in the inlet water temperature, the internal temperature of the concrete does not necessarily decrease by 1°C. There is a proportional relationship between the two. The adjustment coefficient reflects the correspondence between the decrease in inlet water temperature and the decrease in internal concrete temperature. The value is less than 1. The product of the excess amount and the adjustment coefficient is the amount by which the upper limit of the inlet water temperature needs to be adjusted downward. The larger the excess amount, the larger the adjustment required, and the lower the upper limit of the candidate range. This is used to screen out parameter combinations with excessively high inlet water temperature and insufficient cooling capacity.

[0047] In this embodiment, the preset adjustment coefficient is determined as follows: Before formally optimizing the temperature control parameters, two simulations are performed using a finite element model. Both simulations use the measured temperature value at the beginning of the current temperature control period as the initial temperature field, and the thermal resistance of the insulation material is set to the median value within the range. In the first simulation, the cooling water inlet temperature is set to the upper limit of the preset range. After the simulation, the highest internal monitoring point temperature at the end of the current period is extracted and recorded as the first temperature value. In the second simulation, the cooling water inlet temperature is set to the lower limit of the preset range. After the simulation, the highest internal monitoring point temperature at the end of the current period is extracted and recorded as the second temperature value. The difference between the first temperature value and the second temperature value is calculated, which is the magnitude of the decrease in the highest internal monitoring point temperature when the inlet water temperature drops from the upper limit to the lower limit. This difference is then divided by the difference between the upper and lower limits of the inlet water temperature to obtain the magnitude of the decrease in the highest internal monitoring point temperature for every 1°C decrease in the inlet water temperature. This ratio is the preset adjustment coefficient.

[0048] Two pre-simulations simulated two extreme cases of cooling capacity. The first pre-simulation set the inlet water temperature to the upper limit, representing the cooling system operating at its weakest capacity. The second pre-simulation set the inlet water temperature to the lower limit, representing the cooling system operating at its strongest capacity. By comparing the differences in the internal temperature response of the concrete under the two extreme conditions, a complete quantitative relationship can be obtained regarding the impact of changes in inlet water temperature on the internal temperature in the current state of the concrete.

[0049] The first temperature value corresponds to the internal temperature after the weakest cooling period ends, and the second temperature value corresponds to the internal temperature after the strongest cooling period ends. The difference between the two reflects the maximum temperature control range that can be achieved by adjusting the inlet water temperature during the current period. The larger the difference, the more significant the influence of the inlet water temperature on the internal temperature, and the more effective the adjustment of the inlet water temperature. The smaller the difference, the more limited the influence of the inlet water temperature, and the more likely it is to rely on insulation measures or extend the cooling time.

[0050] The difference between the upper and lower limits of the inlet water temperature is the maximum water temperature regulation range that the cooling system can provide. Dividing the total decrease in internal temperature by the total range of inlet water temperature regulation yields an average proportional relationship, that is, how many degrees the internal temperature decreases for every 1°C decrease in inlet water temperature. This ratio establishes a quantitative relationship between the change in inlet water temperature and the change in the internal temperature of the concrete.

[0051] If the result of the subtraction is lower than the preset lower limit, then the preset lower limit is used as the upper limit of the candidate range.

[0052] When the temperature drop is extremely large, the upper limit calculated based on the excess may be lower than the lower limit of the equipment's capacity. At this point, the cooling system can no longer provide a lower inlet water temperature and can only operate at the maximum cooling capacity. Therefore, the preset lower limit is taken as the upper limit of the candidate range, and the candidate range is compressed to the lower limit.

[0053] Step 3: Select multiple inlet water temperature values ​​within the candidate range of cooling water inlet temperature, and select multiple thermal resistance values ​​within the range of thermal resistance values ​​of insulation material. Pair the multiple inlet water temperature values ​​with the multiple thermal resistance values ​​to form multiple candidate temperature control parameter combinations. Multiple inlet water temperature values ​​are paired with multiple thermal resistance values ​​to form multiple candidate temperature control parameter combinations, specifically including: Within the candidate range of cooling water inlet temperature, multiple inlet temperature values ​​are selected at equal intervals according to the preset inlet temperature step size. Within the range of thermal resistance values ​​of insulation material, multiple thermal resistance values ​​are selected at equal intervals according to the preset thermal resistance step size. The inlet water temperature step size is determined comprehensively based on the candidate range span of the current temperature control period and the engineering accuracy requirements. It is usually taken as one-fifteenth to one-tenth of the candidate range span. For example, if the candidate range of the current temperature control period is 10℃ to 20℃, with a span of 10℃, then the inlet water temperature step size range is 0.67℃ to 1.0℃, and 0.8℃ is taken. More than ten sampling points are selected at equal intervals within the candidate range, which can ensure sufficient optimization resolution without causing too many finite element analysis times due to excessive sampling. For periods with large cooling requirements and significantly compressed candidate ranges, the candidate range span is small. In this case, the step size can be appropriately reduced to 0.5℃ to ensure that there are still enough sampling points within the narrow range.

[0054] The thermal resistance step size is determined based on the adjustable precision and range of values ​​of the insulation material at the construction site. The thermal resistance of the insulation material is achieved by adjusting the thickness of the insulation layer or changing the type of insulation material. In actual construction, the adjustment precision of thermal resistance is usually around 0.1 to 0.2 square Kelvin per watt. Therefore, the thermal resistance step size is usually 0.1 or 0.2. Within this range, ten to fifteen sampling points are selected, which roughly match the number of sampling points for the inlet water temperature to ensure a balanced sampling density in both dimensions. After the full combination, the total number of candidate parameter combinations is controlled within several hundred groups, which can fully cover the parameter space and keep the total calculation volume of the subsequent finite element analysis within an acceptable range.

[0055] Each selected inlet water temperature value is combined with each selected thermal resistance value to obtain multiple sets of temperature control parameter combinations. The minimum allowable thermal resistance value is determined based on the temperature drop range. The thermal resistance value in each group of temperature control parameter combinations is compared with the minimum allowable thermal resistance value. Temperature control parameter combinations with thermal resistance values ​​lower than the minimum allowable thermal resistance value are eliminated, and temperature control parameter combinations that meet the conditions are retained as candidate temperature control parameter combinations.

[0056] Cooling water inlet temperature and insulation material thermal resistance are two independent and adjustable temperature control parameters that can be used in combination during actual construction. The inlet water temperature determines the rate at which the cooling water pipes remove heat from the concrete, while the insulation material thermal resistance determines the rate at which the concrete surface dissipates heat to the environment. Together, they determine the magnitude of the temperature drop inside the concrete and the size of the temperature difference between the inside and outside during the current temperature control period. By combining the values ​​selected from these two dimensions, all possible combinations can be generated, ensuring that no potentially optimal parameter combination is overlooked.

[0057] Combinations with thermal resistance values ​​lower than the minimum allowable thermal resistance value indicate insufficient insulation capacity. Under the combined effect of strong cooling, such combinations are very likely to cause the internal and external temperature differences to exceed the standard. Screening them out in advance can avoid selecting dangerous combinations with strong cooling capacity but insufficient insulation, reduce the amount of calculation in subsequent finite element analysis, and improve optimization efficiency and the reliability of results.

[0058] The minimum allowable thermal resistance value is determined based on the temperature drop, specifically including: Obtain a preset reference cooling range and a reference thermal resistance value, and compare the cooling range with the reference cooling range; The reference thermal resistance value refers to the minimum thermal resistance value of the insulation material that corresponds to the reference cooling range and meets the internal and external temperature difference limit requirements. In this embodiment, the reference thermal resistance value is preset in the following way: Before optimizing the temperature control parameters, a pre-simulation calculation is performed using a finite element model. The cooling water inlet temperature is set to the upper limit of the preset range, and the thermal resistance of the insulation material is set to the middle value of the range. The measured temperature data of each temperature monitoring point at the beginning of the current temperature control period is used as the initial temperature field. After the pre-simulation is completed, the maximum difference between the highest temperature value of all internal monitoring points and the lowest temperature value of all surface monitoring points in the current temperature control period is extracted from the calculation results. If the maximum difference does not exceed the preset internal and external temperature difference limit, the middle value of the thermal resistance range of the insulation material is used as the reference thermal resistance value. If the maximum difference exceeds the preset internal and external temperature difference limit, the thermal resistance value of the insulation material is gradually increased. After each increase, the simulation analysis is performed again until the maximum difference does not exceed the internal and external temperature difference limit. The corresponding thermal resistance value of the insulation material at this time is used as the reference thermal resistance value.

[0059] If the cooling range is less than or equal to the reference cooling range, then the reference thermal resistance value shall be used as the minimum allowable thermal resistance value. When the cooling demand is small and the cooling system does not need to be strengthened, the cooling rate inside the concrete is slow, and the temperature difference between the inside and outside is naturally small. At this time, the insulation capacity corresponding to the reference thermal resistance value is sufficient to maintain a safe temperature difference range. There is no need to increase the insulation requirements. The reference thermal resistance value can be directly used as the minimum allowable thermal resistance value, which can avoid imposing excessively high insulation requirements and reduce construction costs and difficulties.

[0060] If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the reference thermal resistance value is added to the product of the excess amount and the preset adjustment coefficient to obtain the minimum allowable thermal resistance value.

[0061] When the temperature drop exceeds the benchmark temperature drop, it indicates that the current cooling task exceeds the capacity of the concrete to dissipate heat naturally. Active cooling must be enhanced by reducing the inlet temperature of the cooling water. The stronger the cooling, the faster the internal temperature drops, and the greater the temperature difference between the inside and outside. If the insulation requirements are not increased accordingly, the excessive heat dissipation from the surface will lead to an excessive temperature difference between the inside and outside, resulting in temperature cracks. Therefore, the larger the portion exceeding the benchmark temperature drop and the higher the cooling intensity, the lower the minimum insulation capacity required must be.

[0062] The excess amount represents the additional cooling required through active cooling. The preset adjustment coefficient quantitatively describes the amount by which the minimum thermal resistance needs to be increased for every 1°C increase in cooling. Multiplying the excess amount by the preset adjustment coefficient converts the additional cooling requirement into the required additional insulation capacity. Adding this increment to the baseline thermal resistance value yields the minimum insulation requirement to meet the current cooling demand.

[0063] In this embodiment, the preset adjustment coefficient is determined in the following way: based on the obtained reference thermal resistance value, a pre-simulation calculation is performed again. The measured temperature value at the beginning of the current temperature control period is used as the initial temperature field, the cooling water inlet temperature is set as the upper limit of the preset range, and the cooling range is set as the preset maximum allowable cooling range, that is, the maximum allowable temperature drop inside the concrete in engineering. The thermal resistance value of the insulation material is adjusted again so that the maximum internal and external temperature difference in the current temperature control period does not exceed the preset internal and external temperature difference limit. The thermal resistance value at this time is recorded as the thermal resistance value corresponding to the maximum cooling range.

[0064] Calculate the difference between the maximum allowable temperature drop and the reference temperature drop as the temperature drop increment. Calculate the difference between the thermal resistance value corresponding to the maximum temperature drop and the reference thermal resistance value as the thermal resistance increment. Divide the thermal resistance increment by the temperature drop increment, and the resulting ratio is the preset adjustment coefficient.

[0065] The maximum allowable cooling range is the limit of the internal temperature of concrete that is allowed to drop within a single time period in engineering. It represents the most extreme cooling requirement. Under this extreme condition, the cooling system needs to operate at its strongest capacity, the inlet water temperature may drop to the lowest level, and the temperature difference between the inside and outside of the concrete reaches the most dangerous state where it is most likely to exceed the standard. Under this condition, the critical thermal resistance value that just meets the temperature difference limit is found, and the maximum heat preservation capacity that may be needed in the entire cooling process is obtained.

[0066] The difference between the maximum cooling range and the baseline cooling range represents the complete range of cooling demand from minimum to maximum. The difference between the maximum thermal resistance value and the baseline thermal resistance value represents the complete range of insulation demand from minimum to maximum. Dividing the increase in thermal resistance value by the increase in cooling range yields the quantitative proportion by which thermal resistance needs to increase for every 1°C increase in cooling range. This ratio reflects the correspondence between the change in cooling intensity and the change in insulation demand under the current thermal characteristics of concrete structures.

[0067] Step 4: Substitute each candidate temperature control parameter combination into the finite element model to predict the temperature field, and obtain the predicted temperature trajectory of the internal monitoring point and surface monitoring point corresponding to each candidate temperature control parameter combination during the current temperature control period. Multiple candidate temperature control parameter combinations have been generated previously. Each combination includes an inlet water temperature value and a thermal resistance value. Whether these parameter combinations can meet the cooling requirements of the current temperature control period, whether they will exceed the temperature limit, and whether they will exceed the temperature difference limit cannot be determined by screening alone. It is necessary to calculate the actual temperature response of each parameter combination under the current thermal state and boundary conditions of the concrete through a finite element model in order to obtain an accurate evaluation basis.

[0068] Internal monitoring points reflect the temperature status of the core area of ​​the concrete, and their highest temperature value is used to determine whether the temperature exceeds the limit. Surface monitoring points reflect the temperature status of the boundary area of ​​the concrete, and the difference between their lowest temperature value and the highest internal temperature value is used to determine whether the internal and external temperature difference exceeds the limit. Each of the two types of monitoring points forms a temperature curve that changes over time, i.e., a predicted temperature trajectory. Only by extracting these two types of trajectories can we fully evaluate the performance of a set of temperature control parameters in terms of both internal temperature control and internal and external temperature difference control.

[0069] Table 1: Finite element method temperature field prediction results (partial feasible combinations) Table 1 shows the finite element temperature field prediction results (some feasible combinations). According to Table 1, after substituting each candidate temperature control parameter combination into the finite element model for temperature field prediction, there are significant differences in the internal peak temperature, minimum surface temperature, and maximum internal-external temperature difference corresponding to different parameter combinations. As the inlet water temperature increases from 10.0℃ to 14.0℃, the internal peak temperature gradually increases from 58.3℃ to 63.1℃, and the cooling effect gradually weakens. As the thermal resistance increases, the minimum surface temperature increases, and the internal-external temperature difference decreases. The prediction results provide a quantitative basis for the subsequent evaluation of the three indicators. The internal peak temperature of each combination does not exceed the maximum temperature limit of 65℃, and the maximum internal-external temperature difference does not exceed the limit of 25℃. However, the safety margins of different combinations differ significantly.

[0070] Please see Figure 2 , Figure 2This diagram illustrates the internal temperature drop comparison in this embodiment. Existing methods combine laboratory experiments with finite element analysis. They involve fabricating concrete specimens for temperature stress testing, inverting material parameters, and importing the results into a finite element model to calculate the cracking risk coefficient. Using this coefficient as the sole criterion, the temperature history is iteratively adjusted until the crack resistance requirements are met. The diagram shows that both curves exhibit a continuous downward trend. The existing method's cooling curve is steep in the early stages and almost stagnant in the later stages, indicating a rapid temperature drop in a short period. In contrast, the cooling curve of this embodiment shows an approximately uniform drop without significant steep drops. This comparison demonstrates that the present invention effectively controls the cooling rate at different stages through the constraint of the temperature fluctuation stability index, ensuring a smooth cooling process and effectively reducing the cracking risk caused by excessive temperature stress gradients. This improves the safety and durability of large-volume concrete structures.

[0071] Step 5: Based on the predicted temperature trajectory, determine the temperature safety margin, temperature difference safety margin, and temperature fluctuation stability index corresponding to each candidate temperature control parameter combination, and take the candidate temperature control parameter combination that meets the preset requirements as the feasible temperature control parameter combination. Based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the internal peak temperature within the current temperature control period is determined. The difference between the preset maximum temperature limit and the internal peak temperature is the corresponding temperature safety margin. The internal peak temperature is the highest temperature value among all internal monitoring points at all times during the current temperature control period. It represents the most extreme temperature state that may occur inside the concrete under the action of the candidate temperature control parameter combination. Once the maximum internal temperature of the concrete exceeds the limit, the heat of hydration will accumulate and cannot be dissipated in time, causing internal micro-cracks or even strength loss. Only by determining the internal peak temperature can we judge whether the parameter combination is qualified in terms of internal temperature control.

[0072] The maximum temperature limit is the upper limit of the allowable temperature inside concrete specified in the engineering design. It is a safety red line that cannot be crossed. Subtracting the internal peak temperature from the limit directly reflects the safety margin of the current parameter combination in terms of internal temperature control. The difference is defined as the temperature safety margin. A positive difference indicates that the internal peak temperature is lower than the limit. The larger the difference, the safer it is. A zero difference indicates that it is just at the critical state. A negative difference indicates that the internal peak temperature has exceeded the limit, and the temperature control parameter combination is unqualified.

[0073] Based on the predicted temperature trajectories of the internal monitoring points and the surface monitoring points corresponding to each candidate temperature control parameter combination, the maximum internal and external temperature difference within the current temperature control period is determined. The maximum internal and external temperature difference is subtracted from the preset internal and external temperature difference limit, and the resulting difference is the corresponding temperature difference safety margin.

[0074] During the temperature control period, the temperatures at the internal and surface monitoring points are not constant but change continuously over time. The internal temperature gradually decreases due to the combined effects of hydration heat and cooling water pipes, while the surface temperature also changes due to environmental heat dissipation and insulation measures. The difference between the two is different at each moment. Looking at the temperature difference at a single moment cannot reflect the most dangerous state throughout the entire temperature control period. The maximum internal and external temperature difference is the maximum value of the difference between the highest internal temperature and the lowest surface temperature at all moments during the entire temperature control period. It represents the most extreme temperature gradient that the concrete may experience under the action of this candidate temperature control parameter combination. Only by determining this maximum value can we accurately judge whether the temperature control parameter combination is safe in terms of temperature difference control.

[0075] The internal and external temperature difference limit is the safe upper limit of the temperature difference between the inside and outside of concrete as specified in the engineering design. Exceeding this limit will generate excessive temperature stress inside the concrete, leading to surface cracks or even through cracks. Subtracting the maximum internal and external temperature difference from the limit, the difference directly reflects the safety margin of the current temperature control parameter combination in terms of temperature difference control. The difference is defined as the temperature difference safety margin. A positive difference indicates that the maximum temperature difference is below the limit and is safe. A difference of zero indicates that it is in a critical state. A negative difference indicates that the maximum temperature difference has exceeded the standard and the parameter combination is unqualified in terms of temperature difference control.

[0076] Based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the sequence of the highest temperature value of the internal monitoring points changing with time is arranged in chronological order. The absolute value of the temperature change between two adjacent times is calculated, and the maximum value of the absolute value of the temperature change among all adjacent times is taken as the temperature fluctuation stability index. The internal monitoring points are located in the core area of ​​the concrete structure, which is where the heat of hydration accumulates the most, the temperature is the highest, and the changes are the most significant during the cooling process. The temperature fluctuations at this location are the most drastic in the entire structure, and it is also the weakest link most prone to stress concentration due to sudden temperature drops. Taking the sequence of the highest internal temperature values ​​to evaluate the fluctuations can capture the most dangerous change characteristics during the cooling process. If the change of the highest internal temperature is stable, the temperature changes at other locations are usually also stable.

[0077] The temperature change between adjacent time periods directly reflects the rate at which the internal temperature of the concrete decreases per unit time. Taking the absolute value is to measure the magnitude of the change. Whether it is heating or cooling, if the magnitude is too large, it will generate uneven thermal stress. If the change between adjacent time periods is not calculated, and only the temperature difference between the beginning and end of the time period is considered, it is impossible to detect whether there was a sharp drop in temperature in a short period of time in the middle.

[0078] The temperature change varies throughout the entire temperature control period. The maximum value represents the largest sudden drop in concrete internal temperature at a certain moment under the action of the candidate temperature control parameter combination. The larger the value, the faster the cooling rate is at a certain moment, resulting in a larger temperature stress gradient and a higher risk of cracking. Focusing only on the average or cumulative value will mask the risk of local damage caused by instantaneous and violent fluctuations. Taking the maximum value as the evaluation index can ensure that the cooling rate at any moment during the entire temperature control period is within a controllable range.

[0079] Candidate temperature control parameter combinations that meet preset requirements for temperature safety margin, temperature difference safety margin, and temperature fluctuation stability are selected as feasible temperature control parameter combinations.

[0080] The preset conditions are as follows: the temperature safety margin and the temperature difference safety margin must be greater than or equal to zero, because these two indicators directly correspond to the two safety red lines for temperature control of large-volume concrete. If either one is breached, it means that the concrete is at risk of cracking. The temperature fluctuation stability must not exceed a preset stability threshold. The preset stability threshold is a quantitative standard used to judge whether the cooling process is stable. Different candidate thresholds are selected and substituted into the finite element model for trial calculation. When the threshold is too small, there are too few parameter combinations that meet the requirements. When the threshold is too large, the constraint effect on temperature fluctuation is insufficient. The candidate value that meets the preset conditions and whose number of parameter combinations meets the requirements of the engineering selection range is selected as the stability threshold.

[0081] In this embodiment, the preset stability threshold is 1.0℃, which corresponds to a relatively strict safety standard and is suitable for important structural parts with high requirements for crack control. For general structural parts or periods with gradual cooling demand, this threshold can be appropriately relaxed to 1.5℃. Between any two adjacent time points during the temperature control period, the decrease in the highest temperature value of the monitoring point inside the concrete must not exceed 1.0℃. If the temperature fluctuation stability index obtained after calculation of a candidate temperature control parameter combination exceeds this 1.0℃ threshold, it indicates that under the action of this temperature control parameter combination, there is a drastic cooling inside the concrete in a short period of time, which may generate an excessive temperature stress gradient and increase the risk of cracking.

[0082] By establishing a comprehensive evaluation and admission mechanism based on three indicators, a multi-dimensional and all-time comprehensive safety assessment can be achieved. This avoids the possibility of selecting combinations of parameters with hidden risks due to a single evaluation dimension. Only combinations that are fully verified as safe in this stage are eligible for final selection. This allows the final selection decision to focus on finding the solution that is closest to the target temperature without having to worry about its basic safety. This simplifies the final decision-making logic and ensures the reliability of the final result.

[0083] Step 6: Select the candidate temperature control parameter combination with the smallest absolute value of the deviation between the predicted temperature of the internal monitoring point and the target control temperature at the end of the current temperature control period from the feasible temperature control parameter combinations as the target temperature control parameter for the current temperature control period.

[0084] Determine whether the current temperature control period is the last temperature control period in the entire cooling process; If it is the last temperature control period, then the target temperature control parameter is selected according to the method of minimizing the absolute value of the deviation; If it is not the last temperature control period, then from the feasible temperature control parameter combinations, select the set in which the predicted temperature of the internal monitoring point at the end of the current temperature control period is lower than the target control temperature, and the absolute value of the deviation is the smallest, as the target temperature control parameter for the current temperature control period.

[0085] The entire cooling process of large-volume concrete consists of multiple consecutive temperature control periods, each with its own cooling target. The goal of the last temperature control period is to precisely reduce the internal temperature of the concrete to the final target temperature required by the project. The core task of this period is accuracy, allowing the temperature to slightly exceed or fall below the target value while meeting the standard, as long as the deviation is minimal.

[0086] Unlike the last temperature control period, after these intermediate periods, the concrete will enter the next temperature control period to continue cooling. If the predicted temperature at the end of this temperature control period is not lower than the target control temperature, it means that the current temperature control period has failed to reach the target control temperature. The starting temperature of the next temperature control period will be higher than the original planned value, and the total cooling range to be completed will be increased on the basis of the original plan. If the next period is short, the cooling rate will be forced to accelerate significantly, the temperature fluctuation stability will deteriorate, and the risk of cracking will increase. If the period is long, although the extra task can be distributed by extending the cooling time, a lower inlet water temperature or stronger cooling measures will still be required, and the range of candidate temperature control parameters will be limited. In any case, the cooling task left over from this period will increase the control pressure of the next period and may be transmitted to subsequent periods along the time direction, disrupting the predetermined rhythm of the entire cooling curve.

[0087] If the predicted temperature is lower than the target control temperature at the end of this temperature control period, it means that the cooling task has been exceeded during this period, and the concrete temperature has dropped lower than originally planned. This is beneficial for the next temperature control period, as the starting temperature of the concrete will be lower and closer to the target control temperature. The cooling range required in the next temperature control period will be smaller and the task will be easier. This means that gentler cooling measures can be adopted in the next period, the cooling rate can be smoother, the temperature fluctuation will be smaller, and the risk of cracking will be lower.

[0088] When selecting the target temperature control parameter for the current temperature control period from the feasible temperature control parameter combinations, if there are multiple feasible temperature control parameter combinations with equal absolute deviation values, then the combination with the smallest temperature fluctuation stability index is selected as the target temperature control parameter for the current temperature control period.

[0089] When the absolute values ​​of the deviations between the predicted temperature and the target control temperature of multiple feasible temperature control parameter combinations are equal, it means that they perform completely identically in terms of temperature control accuracy. In this case, if a set is randomly selected, it may result in a parameter combination with drastic fluctuations during the cooling process, which is detrimental to the crack resistance of concrete. The temperature fluctuation stability index measures the smoothness of the internal temperature change of concrete during the current temperature control period. The smaller the index, the smoother the cooling process and the more uniform the temperature stress distribution, which is more beneficial to the crack resistance of concrete. Under the condition of the same accuracy, selecting a parameter combination with a more stable cooling process can obtain better crack resistance without sacrificing the temperature control accuracy.

[0090] Table 2: Evaluation Results of Triple Indicators and Selection of Target Temperature Control Parameters Table 2 shows the evaluation results of the triple index and the selection of target temperature control parameters. According to Table 2, among the feasible temperature control parameter combinations, the temperature safety margin and temperature difference safety margin of each combination are positive, and the temperature fluctuation stability index does not exceed the preset threshold of 1.0℃. This indicates that all retained candidate combinations meet the triple safety requirements. In the final selection of target parameters, the absolute value of the deviation between the predicted internal temperature of combination 2 (55.3℃) and the target control temperature (55.0℃) is 0.3℃, the smallest among all feasible combinations. Therefore, it was selected as the target temperature control parameter for the current temperature control period. This result demonstrates that the present invention, through the triple index evaluation mechanism, can effectively screen out parameter combinations with potential safety hazards and achieve refined selection of temperature control parameters through the principle of minimum deviation, enabling the internal temperature of the concrete to accurately approach the preset cooling target.

[0091] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0092] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0093] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0094] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for optimizing temperature control in large-volume hydraulic concrete, characterized in that, The specific steps include: Step 1: Establish a finite element model of the temperature field of the target concrete structure, obtain the maximum internal temperature limit and the internal-external temperature difference limit of the target large-volume concrete structure, and collect the measured temperature values ​​of each temperature monitoring point at the beginning of the temperature control period. The temperature monitoring points include internal monitoring points and surface monitoring points. Step 2: Based on the measured temperature values ​​of each temperature monitoring point, correct the initial temperature field of the finite element model during the temperature control period. Based on the temperature drop between the measured temperature values ​​of the internal monitoring points at the beginning of the temperature control period and the target control temperature at the end of the temperature control period, determine the candidate range of cooling water inlet temperature during the temperature control period. Step 3: Select multiple inlet water temperature values ​​within the candidate range of cooling water inlet temperature, and select multiple thermal resistance values ​​within the range of thermal resistance values ​​of insulation material. Pair the multiple inlet water temperature values ​​with the multiple thermal resistance values ​​to form multiple candidate temperature control parameter combinations. Step 4: Substitute each candidate temperature control parameter combination into the finite element model to predict the temperature field, and obtain the predicted temperature trajectory of the internal monitoring point and surface monitoring point corresponding to each candidate temperature control parameter combination during the current temperature control period. Step 5: Based on the predicted temperature trajectory, determine the temperature safety margin, temperature difference safety margin, and temperature fluctuation stability index corresponding to each candidate temperature control parameter combination, and take the candidate temperature control parameter combination that meets the preset requirements as the feasible temperature control parameter combination. Step 6: Select the candidate temperature control parameter combination with the smallest absolute value of the deviation between the predicted temperature of the internal monitoring point and the target control temperature at the end of the current temperature control period from the feasible temperature control parameter combinations as the target temperature control parameter for the current temperature control period.

2. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: Correcting the initial temperature field of the finite element model during the temperature control period includes: assigning the measured temperature values ​​of each temperature monitoring point to the corresponding position in the finite element model, and calculating the temperature of the remaining positions based on the temperature of each corresponding position to form the initial temperature field of the current period. When estimating the temperature at other locations, the temperature distribution is estimated based on the spatial relationship between each temperature monitoring point and the other locations.

3. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 2, characterized in that: For each of the remaining locations, an influence range is defined with the remaining location as the center and a preset influence radius is used to filter out temperature monitoring points located within the influence range; Calculate the spatial distance between the remaining location and each selected temperature monitoring point, use the reciprocal of the spatial distance as the initial weight of each selected temperature monitoring point to the remaining location, and perform normalization to obtain the influence weight of each selected temperature monitoring point. The measured temperature values ​​of each selected temperature monitoring point are weighted and averaged according to the corresponding influence weights to obtain the estimated temperature values ​​of the remaining locations.

4. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: The candidate range for the cooling water inlet temperature during the temperature control period is determined based on the temperature drop rate, including: A preset range of cooling water inlet temperature is obtained, wherein the preset range has a preset upper limit and a preset lower limit, and the preset lower limit is used as the lower limit of the candidate range. The cooling range is compared with a preset benchmark cooling range. If the cooling range is less than or equal to the benchmark cooling range, the preset upper limit value is used as the upper limit value of the candidate range. If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the product of the excess amount and the preset adjustment coefficient is subtracted from the preset upper limit value to obtain the upper limit value of the candidate range. If the result of the subtraction is lower than the preset lower limit, then the preset lower limit is used as the upper limit of the candidate range.

5. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 4, characterized in that: Multiple inlet water temperature values ​​are paired with multiple thermal resistance values ​​to form multiple candidate temperature control parameter combinations, specifically including: Within the candidate range of cooling water inlet temperature, multiple inlet temperature values ​​are selected at equal intervals according to the preset inlet temperature step size. Within the range of thermal resistance values ​​of insulation material, multiple thermal resistance values ​​are selected at equal intervals according to the preset thermal resistance step size. Each selected inlet water temperature value is combined with each selected thermal resistance value to obtain multiple sets of temperature control parameter combinations. The minimum allowable thermal resistance value is determined based on the temperature drop range. The thermal resistance value in each group of temperature control parameter combinations is compared with the minimum allowable thermal resistance value. Temperature control parameter combinations with thermal resistance values ​​lower than the minimum allowable thermal resistance value are eliminated, and temperature control parameter combinations that meet the conditions are retained as candidate temperature control parameter combinations.

6. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 5, characterized in that: The minimum allowable thermal resistance value is determined based on the temperature drop, specifically including: Obtain a preset reference cooling range and a reference thermal resistance value, and compare the cooling range with the reference cooling range; If the cooling range is less than or equal to the reference cooling range, then the reference thermal resistance value shall be used as the minimum allowable thermal resistance value. If the cooling range is greater than the reference cooling range, the excess amount of the cooling range beyond the reference cooling range is calculated, and the reference thermal resistance value is added to the product of the excess amount and the preset adjustment coefficient to obtain the minimum allowable thermal resistance value.

7. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: Based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the internal peak temperature within the current temperature control period is determined. The difference between the preset maximum temperature limit and the internal peak temperature is the corresponding temperature safety margin. Based on the predicted temperature trajectories of the internal monitoring points and the surface monitoring points corresponding to each candidate temperature control parameter combination, the maximum internal and external temperature difference within the current temperature control period is determined. The maximum internal and external temperature difference is subtracted from the preset internal and external temperature difference limit, and the resulting difference is the corresponding temperature difference safety margin.

8. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: Based on the predicted temperature trajectory of the internal monitoring points corresponding to each candidate temperature control parameter combination, the sequence of the highest temperature value of the internal monitoring points changing with time is arranged in chronological order. The absolute value of the temperature change between two adjacent times is calculated, and the maximum value of the absolute value of the temperature change among all adjacent times is taken as the temperature fluctuation stability index. Candidate temperature control parameter combinations that meet preset requirements for temperature safety margin, temperature difference safety margin, and temperature fluctuation stability are selected as feasible temperature control parameter combinations.

9. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: Determine whether the current temperature control period is the last temperature control period in the entire cooling process; If it is the last temperature control period, then the target temperature control parameter is selected according to the method of minimizing the absolute value of the deviation; If it is not the last temperature control period, then from the feasible temperature control parameter combinations, select the set in which the predicted temperature of the internal monitoring point at the end of the current temperature control period is lower than the target control temperature, and the absolute value of the deviation is the smallest, as the target temperature control parameter for the current temperature control period.

10. The method for optimizing temperature control of large-volume hydraulic concrete according to claim 1, characterized in that: When selecting the target temperature control parameter for the current temperature control period from the feasible temperature control parameter combinations, if there are multiple feasible temperature control parameter combinations with equal absolute deviation values, then the combination with the smallest temperature fluctuation stability index is selected as the target temperature control parameter for the current temperature control period.

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