JP6911260B2 - Concrete partial cooling method and circulation cooling system - Google Patents

Description

The present invention mainly relates to post-cooling of concrete, and more specifically, a concrete partial cooling method capable of partially cooling concrete after setting an appropriate end time in advance, and a circulation cooling system. It is about.

Concrete is one of the most important construction materials along with steel materials, and is used in various structures such as civil engineering structures such as dams, tunnels, and bridges, and building structures such as apartment buildings and office buildings. This concrete structure may be manufactured in advance at a factory or the like and transported to a predetermined place, but in the case of a civil engineering structure or a building structure, it is often directly constructed at a predetermined place (site). In any case, the concrete structure is constructed by driving concrete (fresh concrete) in a state where cement, water, aggregate, etc. are kneaded into the formwork, waiting for the concrete to harden, and then removing the formwork.

As mentioned above, concrete is a material that hardens with the passage of time, and as time passes, the internal temperature rises due to the hydration reaction of concrete, its strength also rises, and its elastic modulus also improves. Is. By the way, cracks may occur in the process of changing from fresh concrete to "hardened concrete" or while it is being used as a structure after hardening. Some cracks in concrete are harmless and do not affect the use of the structure, while others are harmful cracks that have a significant impact on the use. Therefore, the cause and mechanism of cracking have been clarified in many parts, and various methods have been adopted for countermeasures.

The types of cracks are classified according to the cause of their occurrence, and are further classified into the cause before concrete hardening and the cause after hardening. Causes before curing include "initial cracks" caused by movement of the mold and abnormal condensation of cement, and "plastic shrinkage cracks" caused by rapid drying of the surface during curing. On the other hand, the causes after curing include "dry shrinkage cracks" caused by shrinkage of cement gel due to water loss, "physical and chemical cracks" caused by corrosion of reinforcing bars and alkali-aggregate reaction, and excessive load. Examples include "structural cracks" caused by action and subsidence of structures.

Further, in a concrete structure having a relatively large member thickness (so-called mass concrete), temperature cracking may become a problem. These temperature cracks are roughly classified into those caused by internal restraint and those caused by external restraint, and the process (mechanism) until the crack occurs is different for each.

In the process of hardening concrete, water reacts with cement, and at that time, heat of hydration is generated, so the temperature of concrete rises over time. However, if the outside air temperature is low, the surface temperature of the concrete does not rise so much in the portion near the concrete surface (outer peripheral portion) due to heat dissipation (heat transfer) to the outside air. As a result, a remarkable temperature difference is generated between the inside and the outer periphery of the concrete, and while the inside is thermally expanded, the outer periphery is not so thermally expanded, so that a tensile force acts on the outer periphery. What is generated by this tensile force is temperature cracking due to internal restraint.

On the other hand, when the concrete reaches a predetermined temperature, the temperature drops, and the concrete tends to shrink as a whole as the temperature drops. However, where it is in contact with existing concrete or the like, it cannot be freely contracted because it is in a restrained state. As a result, a tensile force acts on the part of the concrete that is constrained to the outside. What is generated by this tensile force is temperature cracking due to external restraint. It should be noted that temperature cracks due to external restraint often result in cracks penetrating the skeleton.

As described above, although the generation mechanism differs between the temperature cracks due to internal restraint and the temperature cracks due to external restraint, they are common in that the cause is the temperature rise of concrete caused by the heat of hydration of cement. Therefore, as a measure against temperature cracks, a method of suppressing the temperature rise of concrete has become the mainstream. For example, as a measure at the time of design, in order to suppress the rise in heat of hydration, the formulation design is devised, such as the use of low heat generation cement, the reduction of the amount of cement, and the use of an admixture that reduces the heat of hydration. .. Alternatively, the installation of crack-inducing joints may be planned for the purpose of inducing cracks in places where cracks are relatively unaffected.

Typical measures against temperature cracks during construction include pre-cooling, post-cooling, and long-term heat insulation curing. Pre-cooling cools the fresh concrete at the time of driving, and various cooling methods are adopted, such as using flake-shaped ice as the mixing water and injecting liquid nitrogen during mixing with a mixer or truck agitator. Has been done.

Post-cooling includes a method of providing a temperature diffusion surface inside the skeleton such as a cooling slot to promote natural cooling, and pipe cooling in which cooling water is passed through a pipe to cool concrete. In this pipe cooling, a cooling pipe such as a thin-walled steel pipe (hereinafter referred to as "cooling pipe") is laid in the skeleton in advance, and low-temperature water, air, etc. (hereinafter referred to as "refrigerant") is introduced into the cooling pipe after concrete is poured. It is a rational and economical method that can be realized with relatively simple equipment and work by simply sending it to.

Conventionally, the main purpose of post-cooling has been to lower the maximum temperature of concrete (hereinafter referred to as "peak temperature"), and to raise the peak temperature of the entire member to a predetermined temperature (ambient temperature or expected final temperature) at an early stage. It was supposed to be lowered. Therefore, it is common to post-cool the entire concrete that has been driven in, and finish it when a predetermined period (several hours to half a day) has passed from the time when it was judged that the peak temperature was reached. there were. However, as a result of research, the inventors have found that it is more effective to partially post-cool the concrete that has been driven in for temperature cracks due to external restraint. For convenience of explanation, the cooling performed on the entire concrete is referred to as "total cooling", and the cooling performed partially is referred to as "partial cooling".

When the externally constrained portion (hereinafter referred to as “constrained portion”) is partially cooled, the maximum temperature of the constrained portion is reduced and the tensile stress of the entire member becomes uniform, and as a result, the local portion is locally constrained. It is possible to prevent the crack index from becoming small. Further, by providing a cooling range (hereinafter referred to as "cooling range") and a non-cooling range (hereinafter referred to as "non-cooling range"), a "tag tightening effect" can be obtained, which is more effective. It is possible to suppress temperature cracks due to external restraint. Hereinafter, this "tag tightening effect" will be described.

Naturally, the temperature state differs between the cooling range and the non-cooling range, and therefore, the timing of conversion from thermal expansion to contraction and the mode of shape change associated with contraction also differ. In other words, as shown in FIG. 1, the cooling range and the non-cooling range appear to behave differently. FIG. 1 is a model diagram showing a shape change between an expansion period and a systole in concrete subject to external restraint. FIG. 1A shows a case where post-cooling is not performed, and FIG. 1B shows a case where partial cooling is performed. There is. As shown in FIG. 1 (b), focusing on the non-cooling range at the time of contraction, the non-cooling range tries to contract the cooling range by itself contracting, that is, the non-cooling is performed so as to introduce a compressive force into the cooling range. It can be seen that the range is deformed. As a result, even if a tensile force is generated in the cooling range (that is, the confined portion) due to the external restraint, the tensile force is reduced (relaxed) by the effect of introducing the compressive force from the non-cooling range, and the temperature cracks due to the external restraint. Is suppressed. The effect of reducing the tensile force due to the compressive force from this non-cooling range is the above-mentioned "tag tightening effect".

For the reasons explained above, the inventors have concluded that "partial cooling", which cools only the confined portion, is effective as a countermeasure against temperature cracks due to external restraint. So far, although the technique of simply partially cooling has been shown in Patent Document 1, partial cooling based on the above reason has not been proposed.

Japanese Unexamined Patent Publication No. 2016-11582

By the way, as described above, temperature cracking due to external restraint occurs due to the restraint of heat shrinkage due to the temperature drop, and the greater the degree of the temperature drop, the more likely it is to occur. Therefore, post-cooling is performed to lower the peak temperature of concrete, but cooling increases heat shrinkage, and the stagnation of the rise in concrete temperature delays the development of its strength, resulting in cracks. There is also an aspect that it becomes easier. Therefore, the cooling is completed at an early stage, that is, when a predetermined period has elapsed from the time when it is determined that the peak temperature has been reached. The reason why the temperature is continued for a predetermined period after reaching the peak temperature is to prevent the temperature from rising (rebound) again.

Even if partial cooling is performed as a countermeasure against temperature cracks due to external restraint, it is important to stop cooling at an early stage in order to prevent an increase in heat shrinkage and a delay in strength development. However, as explained earlier, until now, it has only been said that "it will end after waiting for a predetermined period after reaching the peak temperature", and it is the time to properly (logically) end cooling (hereinafter, "" Not many proposals have been made regarding the technology for setting the "end of cooling". Furthermore, there has been no proposal for a technique for setting the final stage of cooling when partial cooling is performed. An object of the present invention is to provide a technique for setting a cooling end stage capable of accurately suppressing temperature cracks in partial cooling of concrete, and to provide a concrete partial cooling method and a circulation cooling system for realizing this. It is to be.

The present invention focuses on the point that, when partially cooling concrete, the minimum crack index of concrete is obtained, and the final cooling period is set based on the minimum crack index and the threshold value for the final stage. It was done based on an idea that did not exist.

The concrete partial cooling method of the present invention is a method of cooling only the "cooling range" of the target concrete, and is a method including a pre-analysis step and a cooling step. In the pre-analysis process, a "cooling end" is set to stop the cooling of the concrete, and in the cooling process, the concrete in the cooling range is cooled until the cooling end is reached. In the pre-analysis step, the minimum value of the crack index of concrete after driving is obtained as the "minimum crack index", and the final cooling period is set so that the minimum crack index exceeds the "final threshold" (preset).

The concrete partial cooling method of the present invention may be a method further including a temperature measuring step of measuring the concrete temperature after driving. In this case, in the pre-analysis step, the time when the concrete temperature after driving is maximized is calculated as the "temperature peak time", and the cooling period after the temperature peak time is obtained as the "post-peak cooling period". In the cooling process, the final cooling period is corrected based on the concrete temperature at the peak temperature obtained in the pre-analysis process, the concrete temperature obtained in the temperature measurement process, and the post-peak cooling period. To stop.

The concrete partial cooling method of the present invention can also be a method of setting a concrete cooling range in a pre-analysis step. In this case, the minimum crack index is obtained while changing the "analytical cooling range", and the "analytical cooling range" when this minimum crack index exceeds the preset "range threshold" is set as the actual cooling range. do. In addition, it is possible to set the cooling range for analysis by setting the range in the vertical direction, and to set the "cooling range with the specified height" based on this, or to set the range in the horizontal direction for analysis. It is also possible to set the above cooling range and set the "width-defined cooling range" based on this.

The concrete partial cooling method of the present invention may further include a heat insulation curing step of heat insulation curing in a "non-cooling range" in which partial cooling is not performed in the target concrete.

The concrete partial cooling method of the present invention can also be a method of cooling concrete in the cooling range by "pipe cooling". In this case, in the cooling step, the refrigerant is pumped by the pumping means into the cooling pipe embedded in the concrete in the cooling range in a substantially horizontal (including horizontal) posture to flow through.

The concrete partial cooling method of the present invention can also be a method of pipe cooling the tunnel lining concrete. In this case, in the cooling step, the refrigerant is pumped into the cooling pipe buried in the tunnel lining concrete in the cooling range in a substantially horizontal (including horizontal) posture by using a circulation cooling system. This circulation cooling system is equipped with a pumping means and a refrigerant cooling means installed on a mobile formwork carriage for tunnel lining concrete (hereinafter referred to as "centre"), and the refrigerant is pumped by the pumping means. The warmed refrigerant discharged from the cooling pipe is circulated and cooled by being cooled by the refrigerant cooling means.

The circulation cooling system of the present invention allows the refrigerant to flow through a cooling pipe buried in a substantially horizontal (including horizontal) posture only in the cooling range of the tunnel lining concrete, and is used for analysis means, pumping means, and refrigerant cooling. It is equipped with means. The analysis means is a means for obtaining the minimum crack index of concrete after driving, and for obtaining the final cooling period so that the minimum crack index exceeds the threshold value for the final stage. Further, the refrigerant cooling means installed in the center is a means for cooling the refrigerant discharged from the cooling pipe, and the pumping means installed in the center also cools the refrigerant cooled by the refrigerant cooling means until the end of cooling. It is a means for pumping into the cooling pipe.

The concrete partial cooling method and the circulation cooling system of the present invention have the following effects.
(1) By reducing the maximum temperature of the restrained portion, the tensile stress of the entire member becomes uniform, and as a result, it is possible to prevent the crack index from becoming locally small.
(2) Since the "tag tightening effect" can be received, that is, the tensile force generated in the restrained portion is reduced, cracks can be suppressed more effectively.
(3) Since an appropriate cooling end can be set, temperature cracking can be suppressed more effectively.
(4) Since it is partially cooled, it is possible to significantly reduce the cost of equipment such as a cooling pipe and the cost of operation such as cooling as compared with the conventional overall cooling.
(5) Since an appropriate cooling end period is set, wasteful cost and labor due to unnecessary cooling can be eliminated, and the process can be quickly moved to the next process, which can contribute to shortening the construction period.
(6) When the tunnel lining concrete is partially cooled by using the circulation cooling system, it can be carried out together with the movement of the centre, so that the partial cooling can be performed extremely efficiently.

(A) is a model diagram showing the shape change of concrete in the expansion period and systole in the case where post-cooling is not performed, and (b) is a model diagram showing the shape change of concrete in the expansion period and systole in the case where partial cooling is performed. .. A model diagram schematically showing the cooling range and non-cooling range of the target concrete. Graph graph comparing the relationship between the elapsed time after concrete pouring and concrete stress in the case without cooling, the case with total cooling, and the case with partial cooling. (A) shows the relationship between the elapsed time after concrete driving and the concrete temperature in the case of no cooling, the case of partial cooling for only 1 day after driving, the case of partial cooling for 2 days after driving, and the case of partial cooling for 5 days after driving. A comparative graph, (b) shows the relationship between the elapsed time after concrete driving and concrete stress: a case without cooling, a case with partial cooling for only 1 day after driving, a case with partial cooling for 2 days after driving, and a case with 5 days after driving. The graph figure which compared in the case of partially cooling. The flow chart which shows the flow of the main process of the concrete partial cooling method of this invention. A flow chart showing an example of a procedure for setting a cooling range by performing a temperature stress analysis while changing the cooling range in the analysis. (A) is a model diagram in which temperature stress analysis is performed while changing the analytical cooling range, and (b) is a graph showing the results of temperature stress analysis while changing the analytical cooling range. The flow chart which shows an example of the procedure of setting the cooling end by a temperature stress analysis. (A) is a graph showing the change in the crack index when the analytical cooling period is 2 days, and (b) is a graph showing the change in the crack index when the analytical cooling period is 5.5 days. figure. The graph which shows the relationship between the cooling period in analysis and the minimum crack index. (A) is a model diagram showing a circulation cooling system installed in a tunnel mine, and (b) is a block diagram showing a main configuration of a circulation cooling system. A partial cross-sectional view showing a structure in which a part of the cooling pipe near the concrete wall surface can be removed. A partial cross-sectional view showing an end of a cooling pipe to which a grout hose having a diameter smaller than that of the cooling pipe is connected.

An example of the concrete partial cooling method of the present invention and the embodiment of the circulation cooling system will be described with reference to the drawings. The circulation cooling system of the present invention is used when implementing the concrete partial cooling method of the present invention for tunnel lining concrete. Therefore, the concrete partial cooling method of the present invention will be described first, and then the circulation cooling system of the present invention will be described.

1. 1. Concrete part cooling method (overall overview)
The concrete partial cooling method of the present invention is a method of cooling only the cooling range of the concrete to be cooled (hereinafter, referred to as “target concrete”). FIG. 2 is a model diagram schematically showing a cooling range 110 and a non-cooling range 120 of the target concrete 100. As shown in this figure, the target concrete 100 is constructed in contact with a restraint body 200 such as existing concrete or foundation rock, that is, is constructed in an environment where temperature cracks are likely to occur due to external restraint. Then, the predetermined range set from the position of the target concrete 100 in contact with the restraint body 200 is defined as the “cooling range 110”, and the range excluding the cooling range 110 is defined as the “non-cooling range 120”.

The reason why the target concrete 100 is partially cooled instead of totally cooled is that, as described above, the maximum temperature of the restrained portion is reduced to equalize the tensile stress, thereby suppressing the decrease in the crack index. This is because cracks are effectively suppressed by receiving the tightening effect.

FIG. 3 is a graph showing the relationship between the elapsed time after concrete pouring and the concrete stress, and is a graph comparing the case without cooling (no countermeasure), the case of total cooling, and the case of partial cooling. In FIG. 3, the concrete stress is shown by a solid line, and the tensile strength of the concrete that develops is shown by a broken line. As can be seen from this figure, the concrete stress growth slows down once after the cooling is stopped in both the total cooling and the partial cooling, but the subsequent growth clearly shows that the concrete stress in the partial cooling is higher than that in the total cooling. The degree of rise is small. From this result, it is recognized that partial cooling is a more effective measure than total cooling for temperature cracks due to external restraint.

Further, in the concrete partial cooling method of the present invention, a time (cooling end stage) at which the cooling of the target concrete 100 is stopped is set in advance before actually cooling at the site (site). As mentioned above, even if partial cooling is performed as a countermeasure against temperature cracks due to external restraint, it is important to stop cooling at an early stage in order to prevent an increase in heat shrinkage and a delay in strength development, that is, appropriate cooling. By setting the final stage, effective crack countermeasures can be realized.

FIG. 4 is a graph comparing a case without cooling (no countermeasures), a case with partial cooling for only one day after loading, a case with partial cooling for two days after driving, and a case with partial cooling for five days after driving (a). ) Is a diagram showing the relationship between the elapsed time after the concrete is poured and the concrete temperature, and (b) is a diagram showing the relationship between the elapsed time after the concrete is poured and the concrete stress. Also in FIG. 4B, the concrete stress is shown by a solid line, and the tensile strength of the concrete that develops is shown by a broken line.

As can be seen from FIG. 4 (a), the degree of the subsequent temperature drop is naturally smaller when the cooling is stopped earlier, but if the cooling is stopped too early, the temperature rebounds after the stop as in the case of one-day cooling. ) Will occur. As a result, the peak temperature was higher than in the other cases (2-day cooling and 5-day cooling), and as shown in FIG. 4 (b), the concrete stress was higher in the 1-day cooling case than in the 2-day cooling case. growing. In the case of 5-day cooling, the concrete temperature drops the fastest as shown in FIG. 4 (a), but the tensile strength and stress of the concrete are closest to each other as shown in FIG. 4 (b). Therefore, the "crack index" obtained by dividing the tensile strength of concrete by the concrete stress shows the smallest value, that is, the case of cooling for 5 days is the case where temperature cracks are most likely to occur.

Even if partial cooling is performed in this way, the effect of suppressing temperature cracks differs greatly depending on the time when cooling is stopped. Therefore, in the present invention, it is decided to reasonably set an appropriate cooling end period. Hereinafter, the main elements constituting the concrete partial cooling method of the present invention will be described in detail with reference to FIG.

(Preliminary analysis process)
FIG. 5 is a flow chart showing a flow of a main process of the concrete partial cooling method of the present invention. As shown in this figure, in the concrete partial cooling method of the present invention, a pre-analysis step is first performed (Step 100). Then, in the pre-analysis step, the cooling range 110 is mainly set (Step 110), and the cooling end stage is set (Step 120).

In setting the cooling range 110, it can be set based on the temperature stress analysis using a three-dimensional FEM (Finite Element Method). For example, the temperature stress history of the target concrete 100 is calculated under the condition that cooling is not performed, the crack index is obtained for each node, and the range in which the crack index is lower than a predetermined threshold value is set as the cooling range. Alternatively, a plurality of patterns of cooling ranges (hereinafter referred to as "analytical cooling ranges") that are analysis conditions can be defined, and the pattern that maximizes the "minimum crack index" can be set as the cooling range. For this "minimum crack index", the history of the crack index for each node is obtained by temperature stress analysis, the minimum value for each node is extracted, and the crack index showing the minimum value from the minimum values of all nodes is obtained. Obtained by extracting.

FIG. 6 is a flow chart showing an example of a procedure for setting a cooling range by performing a temperature stress analysis while changing the cooling range in the analysis. Further, FIG. 7A is a model diagram in which the temperature stress analysis is performed while changing the cooling range H in the analysis, and FIG. 7B is a graph showing the result. Note that FIG. 7A is a so-called 1/4 model in which the inverted T retaining wall is divided into four (divided into two in the extension direction and the front / back direction, respectively). Since the cooling period (that is, the final stage of cooling) has not yet been determined at the stage of setting the cooling range, a temporary cooling period (for example, 2 days after the concrete is poured) is first set (Step111).

When a temporary cooling period is set, an analytical cooling range is defined as an initial value (Step 112). For example, in the case of FIG. 7A, since the target concrete 100 is the vertical wall portion of the inverted T-shaped retaining wall and the restraint body 200 is the footing portion, the region extended upward from the upper end of the footing is analyzed. The cooling range is H. When the cooling range H in the analysis is determined, the temperature stress analysis is performed (Step 113). Further, while changing the cooling range H in the analysis (for example, expanding by 50 cm), repeated temperature stress analysis is performed to create a "cooling range-crack index graph" shown in FIG. 7 (b) (Step 114). In FIG. 7B, the horizontal axis is the analytical cooling range H (width from the upper end of the footing), and the vertical axis is the crack index, showing the change in the crack index at each node.

When the "cooling range-crack index graph" can be created, the cooling range 110 to be actually cooled is determined (Step 115). Specifically, the analytical cooling range H when the minimum crack index exceeds the preset threshold value (hereinafter, referred to as “range threshold value” in the sense of the range setting threshold value) is determined as the cooling range 110. .. For example, the range threshold is shown in the "cooling range-crack index graph" shown in FIG. 7 (b), and the horizontal axis value (analysis) in which the minimum crack index (the lowest point of a plurality of line graphs) exceeds this range threshold line. The above cooling range H), that is, an appropriate analytical cooling range H is selected from the appropriate ranges shown in the figure, and this is determined as the cooling range 110.

The cooling range may be set only in the vertical range (that is, the range in which the height is specified) as described above, or in addition to (or instead of this) the horizontal range (that is, the width). The specified range) may be set. When setting a horizontal range as the cooling range, as shown in FIG. 7A, a range widened by a predetermined width from the center of the member is defined as "analytical cooling range B", and the above procedure (vertical range) is set. The cooling range 110 is set by performing the same procedure as the setting procedure of). When the target concrete 100 is driven into a plurality of lifts, the cooling range 110 may be set for each lift.

By the way, one of the reasons for partial cooling is that it receives a tag tightening effect, but by setting the non-cooling range 120 to a considerable area (height, width or area), this tag tightening effect can be achieved. The inventors have confirmed that it will be larger. For example, assuming that the ratio (Rc / Ru) of the region Rc of the cooling range 110 and the region Ru of the non-cooling range 120 is the non-cooling ratio, all the crack indexes show 1 or more when the non-cooling ratio exceeds a predetermined threshold value. .. Therefore, the cooling range may be set so that the non-cooling ratio exceeds a predetermined threshold value. When receiving the tag tightening effect, it is desirable that the non-cooling range 120 is in a state where the temperature is not deprived (thermally expanded), and the cooling range 110 is in a cooled state, that is, a compressive force is introduced. It is desirable that the condition is easy to be affected.

As shown in FIG. 5, when the cooling range 110 can be set, the cooling end is set (Step 120). In this case as well, the cooling range 110 can be set based on the temperature stress analysis using the three-dimensional FEM. FIG. 8 is a flow chart showing an example of a procedure for setting the cooling end by temperature stress analysis. In the example of this flow chart, first, the already determined cooling range 110 is set as an input value (Step 121), and further, a temporary cooling end stage (hereinafter, referred to as “analytical cooling end stage”) is set as an input value (Step 122). ). When the cooling range 110 and the final stage of cooling in the analysis can be set as the input values, the temperature stress analysis is performed (Step 123). Further, while changing the analytical cooling end (for example, extending by one day), repeated temperature stress analysis is performed to create a "cooling end-crack index graph" (Step 124).

FIG. 9 is a graph showing the change in the crack index after the concrete is poured. FIG. 9A shows a case where the analytical cooling period is 2 days, and FIG. 9B shows an analytical cooling period of 5.5 days. Is shown. The crack index shown in this figure is a plot of the crack index having the smallest value among all the nodes at that time (horizontal axis value). Then, the crack index (that is, the minimum crack index) having the smallest value in FIGS. 9 (a) and 9 (b) is extracted, and the horizontal axis is the final stage of cooling in the analysis and the vertical axis is the crack index. What is plotted in is the "end of cooling-crack index graph" shown in FIG.

Once the "cooling end-crack index graph" is created, the cooling end is determined to set the actual cooling period (Step 125). Specifically, the analytical cooling end stage when the minimum crack index exceeds the preset threshold value (hereinafter, referred to as “end-of-life threshold value” in the sense of the end-stage setting threshold value) is determined as the cooling end stage. For example, the "cooling end-crack index graph" shown in FIG. 10 shows the end threshold, and the horizontal axis value (analytical end of cooling) in which the minimum crack index exceeds this end threshold line, that is, the appropriate range shown in the figure. Of these, an appropriate analytical cooling end is selected and determined as the cooling end. The range threshold and the final threshold can be set separately as different values, or can be set as the same value and common threshold (that is, without separating the range threshold and the final threshold).

(Cooling process)
As shown in FIG. 5, when the pre-analysis step (setting of the cooling range and setting of the final cooling stage) is completed, partial cooling is actually performed on the cooling range 110 of the target concrete 100 (Step 200). As this partial cooling method, various methods conventionally used as post-cooling can be adopted, including pipe cooling in which the refrigerant flows through the pipe in the skeleton. For example, when the tunnel lining concrete constructed on the invert concrete which is the restraint body 200 is the target concrete 100, the cooling pipe is buried in the set cooling range 110 in advance in a substantially horizontal (including horizontal) posture. Partial horizontal pipe cooling can be performed by pumping the refrigerant into the cooling pipe using a pumping means such as a pump after the concrete is poured. In this case, it is more preferable to use the circulation cooling system of the present invention described later.

As described above, in order to receive a larger tag tightening effect, the non-cooling range 120 is in a state of thermal expansion (a state in which the concrete temperature is rising), and the cooling range 110 introduces a compressive force. It should be in a state where it is easy to do. Therefore, it is desirable to set the final cooling period while the concrete temperature in the non-cooling range 120 is rising. Further, even if the concrete temperature of the non-cooling range 120 is rising (or falling), the non-cooling range 120 can be heat-retained and cured in order to introduce a larger compressive force into the cooling range 110 (Step 300). By heat-retaining and curing, the non-cooling range 120 expands more thermally, and accordingly, a larger compressive force can be introduced into the cooling range 110 at the time of contraction.

As a method of heat-retaining curing, various methods conventionally used can be adopted, such as heat-insulating curing in which a heat-insulating mat is installed on the concrete surface, heat-retaining curing in which the concrete is actively heated, and so on. Since the purpose of the heat-retaining curing of the non-cooling range 120 is to introduce a compressive force to the cooling range 110 after the cooling is stopped, the heat-retaining curing may be started immediately after the cooling of the cooling range 110 is stopped. In order to improve the efficiency of the above, the heat insulation curing may be started at the same time as the start of partial cooling.

Partial cooling is continuously performed, and partial cooling is stopped at the end of cooling set in the pre-analysis step (Step 600). Alternatively, the actual concrete temperature in the cooling range 110 may be measured during partial cooling (temperature measurement step: Step 400), the final cooling period may be corrected according to the measurement result (Step 500), and then the partial cooling may be stopped. In this case, in the pre-analysis step, the maximum concrete temperature (that is, peak temperature) after driving and the time when the peak temperature is reached (hereinafter referred to as “analysis temperature peak time”) are calculated, and further, this analysis temperature peak time is used. The cooling period from the final stage of cooling to the peak time of the analysis temperature (hereinafter referred to as "post-peak cooling period") is obtained. Then, the peak temperature obtained in the analysis is compared with the time measured at the site (on-site) (hereinafter referred to as "measured temperature peak time") and the analysis temperature peak time, and if they match, the cooling end stage is as it is. Wait, and if different, correct the end of cooling. When modifying the cooling end, it is advisable to set a new cooling end by adding the post-peak cooling period obtained in the analysis to the measured temperature peak time.

2. Circulation cooling system Next, the circulation cooling system 300 of the present invention will be described with reference to FIG. FIG. 11A is a model diagram showing the circulation cooling system 300 installed in the tunnel mine, and FIG. 11B is a block diagram showing the main configuration of the circulation cooling system 300. The circulation cooling system 300 of the present invention is used for the concrete partial cooling method described so far. Therefore, avoiding the explanation overlapping with the contents described in the concrete partial cooling method, the contents peculiar to the circulation cooling system 300. Only will be explained. That is, the contents not described here are the same as those described in the concrete partial cooling method.

As shown in FIG. 11A, the circulation cooling system 300 can be used more effectively when the tunnel lining concrete (target concrete 100) constructed on the invert concrete (constraint body 200) is partially cooled. Can be done. As shown in FIG. 11B, the circulation cooling system 300 includes an analysis means 301, a pressure feeding means 302, and a refrigerant cooling means 303, and also includes a return tank 304, a water pipe 305, a drain pipe 306, and a cooling pipe. It can also be configured to include 307.

The analysis means 301 performs the process performed in the "pre-analysis step" described so far, that is, the process of setting the cooling range and the setting of the final cooling period, and further calculates the peak temperature and the analysis temperature peak time, and cools after the peak. It is also possible to perform processing such as setting the period and correcting the end of cooling. The analysis means 301 can be manufactured as a dedicated one, or a general-purpose computer device can be used.

The pumping means 302, the refrigerant cooling means 303, and the return tank 304 are installed on a mobile formwork cart (centre) for tunnel lining concrete, and the cooling pipe 307 is embedded in the tunnel lining concrete in advance. Of course, the cooling pipe 307 is buried only in the cooling range 110 set by the analysis means 301 in the tunnel lining concrete, and its posture is substantially horizontal (including horizontal) along the tunnel axial direction.

The pumping means 302 and the cooling pipe 307 (inflow port) are connected by a water pipe 305, the cooling pipe 307 (exhaust port) and the return tank 304 are connected by a drain pipe 306, and the return tank 304, the refrigerant cooling means 303, and the refrigerant cooling are further connected. The means 303 and the pumping means 302 are connected by a predetermined pipe, and the refrigerant (water, air, etc.) pumped from the pumping means 302 circulates so as to return to the pumping means 302 again via each means.

The refrigerant pumped by the pumping means 302 passes through the water pipe 305, flows into the cooling pipe 307 (inflow port), and further flows through the cooling pipe 307 while cooling the cooling range 110, and the cooling pipe 307 ( It is discharged from the discharge port) to the drain pipe 306. At this time, since heat exchange is performed with the concrete in the cooling range 110, the temperature of the refrigerant is discharged in an elevated state (for example, hot water). The refrigerant that has passed through the drain pipe 306 is stored in the return tank 304, and the stored refrigerant is sequentially sent to the refrigerant cooling means 303 to be cooled again. Then, the cooled refrigerant is pumped again by the pumping means 302. In this way, the pumping means 302 continuously pumps the refrigerant, and stops the pumping of the refrigerant at the end of cooling set by the analysis means 301.

Of the cooling pipes 307, the vicinity of the inflow port and the vicinity of the discharge port near the concrete wall surface may have a structure that can be removed after the cooling is stopped, as shown in FIG. Specifically, sockets are provided at both ends (that is, the inflow port and the discharge port) of the main of the cooling pipe 307, and the nipple N is screwed into the socket S by using the internal screw of the socket S and the external screw of the nipple N. Let me wear it. The nipple N is arranged so that a part of the nipple N is buried in the concrete and the other part goes out of the concrete. Since the nipple N is screwed to the socket S, it can be removed relatively easily even after the cooling is stopped by grasping and turning the portion protruding from the concrete. It is preferable to apply a release agent such as grease to the screw portions of the socket S and the nipple N in advance so that the nipple N can be easily removed.

Further, since the cooling pipe 307 is filled with a filler such as mortar after the cooling is stopped, it is preferable to install a check valve G at the end of the main pipe of the cooling pipe 307. Further, in a place where cooling is not required and the filler flows out from the upper part to the lower part, a grout hose G having a diameter smaller than that of the cooling pipe 307 may be connected to the end of the cooling pipe 307 as shown in FIG. As a result, it is possible to prevent the filler from freely falling in the cooling pipe 307, and as a result, it is possible to eliminate the unfilled portion of the cooling pipe 307. The inlet and outlet of the cooling pipe 307 may be provided in the invert concrete portion.

The concrete partial cooling method and circulation cooling system of the present invention include tunnel lining concrete, civil engineering structures such as bridge superstructures / substructures, retaining walls, culverts, and dams, or building structures such as apartment buildings and office buildings. It can be used for various other concrete structures. Considering that the invention of the present application provides a so-called high-quality concrete structure with few temperature cracks, it can be said that the invention can be used not only industrially but also can be expected to make a great contribution to society.

100 Target concrete 110 Cooling range (of target concrete) 120 Non-cooling range (of target concrete) 200 Restraint 300 Circulation cooling system 301 (of circulation cooling system) Analytical means 302 (of circulation cooling system) of the present invention Pumping Means 303 (Circulation Cooling System) Cooling Means 304 (Circulation Cooling System) Return Tank 305 (Circulation Cooling System) Water Supply Pipe 306 (Circulation Cooling System) Drainage Pipe 307 (Circulation Cooling System) Cooling Pipe H Analysis Upper cooling range S Socket N Nipple V Check valve G Grout hose

Claims (9)

It is a method of suppressing cracks in concrete by dividing concrete into a cooling range and a non-cooling range and cooling only the cooling range.
Pre-analysis process to set the cooling end to stop the cooling of concrete,
A cooling step of cooling the concrete in the cooling range until the end of cooling is provided.
In the pre-analysis step, the crack index for each node of the concrete after driving is obtained for each time point by performing the temperature stress analysis while changing the cooling end period in the analysis, and the smallest crack index among all the nodes is obtained for each time point. Is extracted, and the minimum value of the smallest crack index extracted for each time point is obtained as the minimum crack index related to the final cooling end in the analysis, and the minimum crack index related to the final cooling stage in the analysis is set in advance for the final stage. Set the cooling end to exceed the threshold,
A concrete part cooling method characterized by that. Further equipped with a temperature measurement process to measure the concrete temperature after driving,
In the pre-analysis step, the time when the concrete temperature after driving is maximized is calculated as the temperature peak time, and the cooling period after the temperature peak time is obtained as the post-peak cooling period.
In the cooling step, the pre-analysis step is based on the concrete temperature at the temperature peak time obtained in the pre-analysis step, the concrete temperature obtained in the temperature measurement step, and the post-peak cooling period. Correct the set cooling end, and stop cooling when the corrected cooling end is reached.
The concrete partial cooling method according to claim 1. In the pre-analysis step, the temperature stress analysis is performed while changing the cooling range in the analysis to obtain the history of the crack index for each node of concrete, extract the minimum value for each node, and further extract for each node. The smallest value among the minimum values is obtained as the minimum crack index related to the analytical cooling range, and the analytical cooling range in which the minimum crack index related to the analytical cooling range exceeds the preset range threshold is defined as the cooling. Set as a range,
In the cooling step, the concrete in the cooling range set in the pre-analysis step is cooled.
The concrete partial cooling method according to claim 1 or 2, wherein the concrete portion is cooled. In the pre-analysis step, the cooling range in analysis is determined by setting the range in the vertical direction, and the cooling range in which the height is defined is set.
The concrete partial cooling method according to claim 3. In the pre-analysis step, the cooling range for analysis is determined by setting the horizontal range, and the cooling range for which the width is defined is set.
The concrete partial cooling method according to claim 3 or 4. The heat-retaining curing process for heat-retaining the concrete in the non-cooling range
The concrete partial cooling method according to any one of claims 1 to 5, further comprising. In the cooling step, the concrete in the cooling range is cooled by pumping the refrigerant into the cooling pipe embedded in the concrete in the cooling range in a horizontal or substantially horizontal posture by pumping means.
The concrete partial cooling method according to any one of claims 1 to 6, wherein the concrete portion is cooled. The object to be cooled is tunnel lining concrete,
In the cooling step, a circulating cooling system is used to cool the tunnel lining concrete in the cooling range.
The circulation cooling system has the pumping means and the refrigerant cooling means installed on the mobile frame trolley for tunnel lining concrete, the refrigerant is pumped by the pumping means, and the refrigerant discharged from the cooling pipe is discharged. The refrigerant is cooled by the refrigerant cooling means, and the refrigerant cooled by the pumping means is pumped.
The concrete partial cooling method according to claim 7. It is a circulation cooling system that allows the refrigerant to flow through the cooling pipes buried in the tunnel lining concrete in a horizontal or substantially horizontal posture only in the cooling range.
Analytical means to find the end of cooling to stop the cooling of concrete,
Pumping means installed on a mobile formwork trolley for tunnel lining concrete,
Provided with a refrigerant cooling means installed on the mobile formwork carriage for tunnel lining concrete.
The analysis means obtains the crack index for each node of concrete after driving by performing temperature stress analysis while changing the cooling end period in the analysis, and extracts the smallest crack index among all the nodes for each time point. Then, the minimum value of the smallest crack index extracted for each time point is obtained as the minimum crack index related to the final cooling end in the analysis, and the final threshold set by the minimum crack index related to the final cooling stage in the analysis is set in advance. Find the end of cooling so that it exceeds
The refrigerant cooling means cools the refrigerant discharged from the cooling pipe.
The pumping means pumps the refrigerant cooled by the refrigerant cooling means into the cooling pipe until the cooling end determined by the analysis means is reached.
A circulation cooling system characterized by that.

Images