JP6997614B2 - How to maintain frozen soil and how to create frozen soil - Google Patents

Description

The present invention relates to a method for maintaining frozen soil and a method for creating frozen soil.

Conventionally, in order to stop water in the ground, a frozen soil type impermeable wall created by circulating a frozen refrigerant through a freezing pipe buried in the ground to freeze the ground around the freezing pipe has been used.

When constructing a frozen soil type impermeable wall, the underground temperature is measured with a temperature measuring pipe buried around the frozen pipe to determine the condition of frozen soil formation. When creating frozen soil, a thermometer is embedded around the freezing pipe, and the optimum refrigerant temperature is calculated using the ground temperature data measured by the thermometer and the frozen refrigerant temperature data to control the frozen refrigerant temperature. There is also a method (see, for example, Patent Document 1).

Japanese Patent No. 5042786

However, if the temperature of the frozen refrigerant is controlled collectively, the formation rate of frozen soil will be faster than other parts depending on the conditions of the construction site, and the frozen soil will grow more than necessary. In some cases, the building was damaged or deformed, the underground design equipment froze, causing malfunctions or failures, and the well for water level observation froze. On the contrary, the frozen soil was easily thawed by the groundwater flow and the sunlight, and the formation rate of the frozen soil was slower in some places than in other parts.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to create frozen soil in a short period of time and to prevent thawing and overproduction of frozen soil to maintain an appropriate thickness of frozen soil. It is to provide a method for maintaining frozen soil and a method for creating frozen soil.

In order to achieve the above-mentioned object, the first invention was created by arranging a plurality of freezing pipes on the freezing pipe arrangement line of the ground and circulating frozen refrigerant in the freezing pipes to form frozen soil. In the frozen soil type impermeable wall, it is determined that the thickness of the frozen soil is smaller than the predetermined thickness by using the freezing suppressing means for suppressing the formation of the frozen soil in the section where the thickness of the frozen soil is determined to be larger than the predetermined thickness. A method for maintaining frozen soil, characterized in that a freezing propulsion means for promoting the formation of frozen soil is used in the section, and a horizontal freezing pipe is installed on the ground surface near the freezing pipe arrangement line as the freezing propulsion means . be.
The second invention is the frozen soil type impermeable wall created by arranging a plurality of freezing pipes on the freezing pipe arrangement line of the ground and circulating the frozen refrigerant through the freezing pipes to form frozen soil. In the section where the thickness of the frozen soil is determined to be larger than the predetermined thickness, the freezing suppression means for suppressing the formation of the frozen soil is used, and in the section where the thickness of the frozen soil is determined to be smaller than the predetermined thickness, the formation of the frozen soil is generated. It is a method for maintaining frozen soil, which comprises using a freezing propulsion means for promoting and installing a horizontal freezing pipe in a groove-shaped excavated portion formed on the ground surface near the freezing pipe arrangement line as the freezing propulsion means. ..

In the section where the thickness of the frozen soil is judged to be larger than the predetermined thickness, the freeze suppression means for suppressing the formation of the frozen soil is used to prevent the excessive formation of the frozen soil, and in the section where the thickness of the frozen soil is judged to be smaller than the predetermined thickness. If the frozen soil is prevented from melting by using a freezing propulsion means that promotes the formation of frozen soil, the thickness of the frozen soil can be appropriately maintained.

In the first and second inventions, for example, it is desirable to lay a heat insulating material on the ground surface near the freezing pipe arrangement line as the freezing propulsion means .
Further , the horizontal freezing pipe may be covered with a soil material or a cement-based material .
As the freezing propulsion means, a sunshade member may be installed above the above-ground portion of the freezing pipe.

When these freeze propulsion means are used alone or in combination, it is possible to prevent the temperature rise of the ground surface part that is easily warmed by outside air temperature, solar radiation, groundwater flow, etc., and prevent the freezing soil from thawing and promote the formation. can.

In the first and second inventions, for example, as the freeze suppressing means, the freezing pipe valve provided in the freezing pipe or the header pipe valve provided in the header pipe which is the main pipe of the freezing pipe is opened and closed. Perform intermittent operation of the freezing pipe.
As the freezing suppressing means, a part of the freezing tube valve provided in the freezing tube may be opened and closed to perform a thinning operation of the freezing tube.
As the freeze suppressing means, the temperature of the frozen refrigerant may be raised.

By using these freeze suppression means, it is possible to raise the underground temperature in or near the frozen soil to prevent or mitigate the overproduction of the frozen soil. If the header tube valve is opened and closed and intermittent operation is performed, the opening and closing of a plurality of freezing tube valves can be switched at one time, so that the work is efficient. By opening and closing the freezing tube valve to perform intermittent operation or thinning operation, it is possible to finely switch each freezing tube according to the situation at the site. Since the temperature of the frozen refrigerant is raised by changing the temperature setting of the refrigerant machine, valve operation is not required and the work is easy.

In the first and second inventions, the underground temperature in or near the frozen soil is continuously measured, the thickness of the frozen soil is estimated based on the underground temperature, and the section using the freeze suppressing means is used. And it is desirable to set a section in which the freezing propulsion means is used.
Thereby, the section using the freezing suppressing means and the section using the freezing propulsion means can be appropriately set to maintain and manage the frozen soil thickness.

The third invention is a method for creating frozen soil in a frozen soil type impermeable wall, in which a step a of installing a plurality of freezing pipes on a freezing pipe arrangement line in the ground and freezing to prevent a temperature rise near the ground surface are provided. A step b of creating frozen soil by circulating a frozen refrigerant inside the plurality of freezing pipes while using the propulsion means is provided , and the freezing propulsion means is horizontal on the ground surface near the freezing pipe arrangement line. It is a method for creating frozen soil, which is characterized by installing a freezing pipe .
The fourth invention is a method for creating frozen soil in a frozen soil type impermeable wall, in which a step a of installing a plurality of freezing pipes on a freezing pipe arrangement line in the ground and freezing to prevent a temperature rise near the ground surface are provided. It is provided with a step b of creating frozen soil by circulating a frozen refrigerant inside the plurality of freezing pipes while using the propulsion means, and is formed on the ground surface near the freezing pipe arrangement line as the freezing propulsion means. It is a method for creating frozen soil, which is characterized by installing a horizontal freezing pipe in a groove-shaped excavated part.

By using freezing propulsion means to prevent the temperature rise near the ground surface, it is possible to prevent the temperature rise of the ground surface part that is easily warmed by outside air temperature, solar radiation, groundwater flow, etc., and to create frozen soil of appropriate thickness in a short period of time. can.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for maintaining frozen soil and a method for creating frozen soil, which can produce frozen soil in a short period of time, prevent thawing and overproduction of the frozen soil, and maintain an appropriate thickness of the frozen soil.

The figure which shows the section 20 which has the thickness defect part 19 in the frozen soil type impermeable wall 9. The figure which shows the state which the freezing propulsion means was installed The figure which shows the section 47 which has a frozen upper part 77 in the frozen soil type impermeable wall 9. Diagram showing changes in underground temperature when intermittent operation is performed The figure which shows the example which combined the horizontal freezing pipe 15 installed on the ground surface 1a and other configurations. The figure which shows the example which combined the horizontal freezing pipe 15 installed in the groove-shaped excavation part 23, and other configurations. The figure which shows the example which combined the horizontal freezing pipe 15 installed in the groove-shaped excavation part 23, and other configurations. The figure which shows the example which used the freezing propulsion means other than the horizontal freezing tube 15. Diagram showing the operation method of thinning operation The figure which shows the area around the obstacle 69 The figure which shows the joint part of the underground impermeable wall of a sheet pile type, and the impermeable wall 9 of a frozen soil type.

Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, a method of constructing the frozen soil type impermeable wall 9 will be described.

FIG. 1 is a diagram showing a section 20 having a thickness defect portion 19 in the frozen soil type impermeable wall 9. FIG. 1A is a horizontal cross-sectional view of the ground 1 at a predetermined depth, and FIG. 1B is a horizontal cross-sectional view of the ground surface 1a. FIG. 1 (c) is a cross-sectional view taken along the line AA shown in FIG. 1 (a). FIG. 2 is a diagram showing a state in which the freezing propulsion means is installed.

In order to construct the frozen soil type impermeable wall 9, as shown in FIG. 1, a plurality of freezing pipes 5 are installed in the vertical direction on the freezing pipe arrangement line 3 of the ground 1. The plurality of freezing tubes 5 are installed at predetermined intervals. The above-ground portion 13 of the freezing pipe 5 is connected to a feed header pipe and a return header pipe (not shown) for supplying and recovering the frozen refrigerant.

Further, a plurality of temperature measuring tubes 7 are installed in the vertical direction on a line substantially parallel to the freezing tube arrangement line 3 at a position separated from the freezing tube arrangement line 3 by a predetermined distance. A temperature measuring meter such as an optical fiber sensor is arranged in the temperature measuring tube 7, and the temperature is measured at a temperature measuring point set every 1 m, for example.

After installing the freezing tube 5 and the temperature measuring tube 7, the frozen refrigerant 11 is created by supplying and circulating the frozen refrigerant inside the freezing tube 5 while continuously measuring the temperature using the temperature measuring tube 7. At this time, as shown in FIG. 1 (c), even if the frozen soil 11 having a predetermined thickness 18 is satisfactorily formed in the deep part of the ground 1, the ground surface 1a which is easily warmed by the outside air temperature, solar radiation, groundwater flow, etc. , The frozen soil 11 may be thawed to form a thickness defect portion 19.

As shown in FIG. 2, in the section 20 in which it is determined that the frozen soil 11 has a thickness defect 19 smaller than the predetermined thickness 18 based on the underground temperature measured by the temperature measuring tube 7 during the preparation of the frozen soil 11. A horizontal freezing pipe 15 is installed on the ground surface 1a near the freezing pipe arrangement line 3 as a freezing propulsion means for preventing a temperature rise near the ground surface.

The horizontal freezing tube 15 is preferably a flexible tube such as an industrial pressure resistant hose or a stainless steel bellows tube. If the horizontal freezing tube 15 is a flexible tube, even if the freezing tube arrangement line 3 is not linear and the freezing tubes 5 are not aligned in a straight line, the horizontal freezing tube is along the freezing tube arrangement line 3. 15 can be easily installed.

Further, as a freezing propulsion means to be combined with the horizontal freezing pipe 15, a heat insulating material 17 is laid so as to cover the ground surface 1a on both sides of the horizontal freezing pipe 15 from the upper side of the horizontal freezing pipe 15. The heat insulating material 17 is, for example, in the form of a sheet. Then, the frozen refrigerant is circulated in the horizontal freezing pipe 15, and the frozen soil 11 is formed in the ground 1 near the freezing pipe arrangement line 3 to eliminate the thickness defect portion 19.

As described above, in the first embodiment, the horizontal freezing pipe 15 is installed as the freezing propulsion means and the heat insulating material 17 is laid, so that the heat insulating material 17 is cold between the horizontal freezing pipe 15 and the ground surface 1a. Air is trapped and the ground 1 near the ground surface 1a is cooled through the cold air. Therefore, the temperature rise of the ground 1 near the ground surface 1a, which is easily warmed by the outside air temperature, solar radiation, groundwater flow, etc., is prevented, the elimination of the thickness defect portion 19 is promoted, and the frozen soil 11 having a predetermined thickness 18 is formed in a short period of time. Can be created.

In the first embodiment, it is determined that the frozen soil 11 has a thickness defect portion 19 smaller than the predetermined thickness 18 based on the groundwater temperature measured by the temperature measuring tube 7 after the start of the formation of the frozen soil 11. Although the freezing propulsion means was used for the section 20, the freezing propulsion means was installed in advance in the section where the ground surface 1a is expected to be easily warmed by the outside air temperature, solar radiation, groundwater flow, etc. before starting the construction of the frozen soil 11. You may. If the freezing propulsion means is installed in advance, it is possible to prevent the temperature of the ground 1 from rising in the vicinity of the ground surface 1a and prevent the occurrence of the thickness defect portion 19.

Next, the second embodiment will be described. In the second embodiment, a method of maintaining the frozen soil type impermeable wall 9 will be described. In the examples shown after the second embodiment, the points different from the embodiments described so far will be described, and the same points will be omitted by the same reference numerals in the drawings and the like.

In the second embodiment, for example, the maintenance of the frozen soil type impermeable wall 9 created by using the method for creating the frozen soil type impermeable wall 9 of the first embodiment is performed.

FIG. 3 is a diagram showing a section 47 having a frozen upper part 77 in the frozen soil type impermeable wall 9. FIG. 3A is a plan view showing the arrangement of various pipes connected to the freezing pipe 5, and FIG. 3B is a vertical cross-sectional view of the frozen soil type impermeable wall 9 in the section 47.

As shown in FIG. 3A, all the freezing tubes 5 are connected to the feeding header tube 37 and the returning header tube 39, which are the main tubes of the freezing tube 5. A freezing tube valve 35 is provided between the freezing tube 5, the feeding header tube 37, and the returning header tube 39, respectively. The feed header pipe 37 is connected to the feed brine pipe 43 via the header pipe valve 41. The return header pipe 39 is connected to the return brine pipe 45 via the header pipe valve 41.

At the time of maintenance of the frozen soil type impermeable wall 9, the frozen refrigerant is sent from the feeding brine pipe 43 shown in FIG. 3A to the freezing pipe 5 via the feeding header pipe 37. The frozen refrigerant circulates in the freezing pipe 5 to cool the ground 1, and then returns to the return brine pipe 45 via the return header pipe 39. Then, while circulating the frozen refrigerant in the freezing pipe 5, the underground temperature in or near the frozen soil 11 is continuously measured by the temperature measuring tube 7, and the thickness of the frozen soil 11 is estimated based on the underground temperature. ..

In the section where it was determined that the frozen soil 11 had melted and had a portion smaller than the predetermined thickness 18 as in the example shown in FIG. 1 (c) during the maintenance of the frozen soil type impermeable wall 9, the section shown in FIG. 2 was used. Similarly, as a freezing propulsion means for preventing a temperature rise near the ground surface, a horizontal freezing pipe 15 is installed on the ground surface 1a near the freezing pipe arrangement line 3 and a heat insulating material 17 is laid to regenerate the frozen soil 11. Promote growth.

As shown in FIG. 3 (b) (the freezing propulsion means is not shown), in the section 47 where it is determined that the frozen soil 11 has a freezing upper portion 77 having a thickness larger than a predetermined thickness 18, the freezing tube valve is used as a freezing suppressing means. The freezing pipe 5 is intermittently operated by opening and closing the 35 or the header pipe valve 41. When the freezing pipe valve 35 is opened and closed, the frozen refrigerant is repeatedly stopped and circulated in a part of the freezing pipe 5. When the header pipe valve 41 is opened and closed, the frozen refrigerant is repeatedly stopped and circulated in all the freezing pipes 5 branching from the header pipe.

FIG. 4 is a diagram showing changes in the underground temperature when intermittent operation is performed. The vertical axis of FIG. 4 is the underground temperature at the position of the temperature measuring tube 7, and the horizontal axis is the period. The control reference value 59 is a value that serves as a reference for stopping the circulation of the frozen refrigerant, and is, for example, −10 ° C. The control reference value 61 is a value that serves as a reference for starting the recirculation of the frozen refrigerant, and is, for example, −2 ° C.
The solid line 49 is the underground temperature at the position of the temperature measuring tube 7 in the section 47, and may be the temperature at a specific measurement depth or the average temperature at all depths.

As shown in FIG. 4, in the construction operation period 51 of the frozen soil type impermeable wall 9, the underground temperature at the position of the temperature measuring tube 7 decreases with the passage of time. In the example shown in FIG. 4, it is determined that the frozen soil type impermeable wall 9 having a predetermined thickness 18 has been constructed when the underground temperature has sufficiently decreased and the temperature has been -5 ° C or less for 2 weeks or more, and the frozen soil type impermeable wall 9 has been constructed. The maintenance operation period 53 of the wall 9 is started.

In the maintenance operation period 53, for example, when the underground temperature of all the temperature measuring tubes 7 in the section 47 becomes −5 ° C. or less and the average underground temperature of all the temperature measuring tubes 7 becomes the control reference value 59 or less, it is predetermined. The freezing pipe valve 35 or the header pipe valve 41 is closed to stop the circulation of the frozen refrigerant to the freezing pipe 5. Further, when the underground temperature exceeds the control reference value 61 at any one of all the temperature measuring tubes 7 in the section 47, the predetermined freezing tube valve 35 or the header tube valve 41 is opened to freeze to the freezing tube 5. Resume the circulation of the refrigerant.

During the maintenance operation period 53, the ground temperature is kept within an appropriate range by opening and closing the predetermined freezing pipe valve 35 or the header pipe valve 41 and repeating the stop period 55 of the frozen refrigerant and the recirculation period 57. It prevents the frozen soil 11 from thawing and excessive formation, and maintains an appropriate thickness of the frozen soil 11.

As described above, in the second embodiment, the horizontal freezing pipe 15 is installed in the vicinity of the freezing pipe arrangement line 3 as the freezing propulsion means, and the heat insulating material 17 is laid. Cold air is confined between the surface 1a and the ground 1 near the ground surface 1a is cooled through the cold air. Therefore, it is possible to prevent the temperature rise of the ground 1 in the vicinity of the ground surface 1a, which is easily warmed by the outside air temperature, solar radiation, groundwater flow, etc., and prevent the frozen soil 11 from melting to promote the formation.

Further, by opening and closing the freezing pipe valve 35 or the header pipe valve 41 as a means for suppressing freezing and performing intermittent operation of the freezing pipe 5, the underground temperature is maintained in an appropriate range and excessive formation of frozen soil 11 is prevented. , The thickness of the frozen soil 11 can be maintained appropriately. By opening and closing the freezing tube valve 35, it is possible to finely switch each specific freezing tube 5 according to the situation. If the header pipe valve 41 is opened and closed, it is efficient because the circulation and stop of the frozen refrigerant in the plurality of freezing pipes 5 at one time can be switched without operating the freezing pipe valve 35.

In the first and second embodiments, as the freezing propulsion means, the horizontal freezing pipe 15 installed on the ground surface 1a near the freezing pipe arrangement line 3 and the ground surface 1a near the freezing pipe arrangement line 3 are laid. Although it is combined with the heat insulating material 17, the freezing propulsion means is not limited to this. The horizontal freezing tube 15 and the heat insulating material 17 may be used alone or in other combinations as the freezing propulsion means.

FIG. 5 is a diagram showing an example in which a horizontal freezing pipe 15 installed on the ground surface 1a and another configuration are combined. In the example shown in FIG. 5A, the horizontal freezing pipe 15 installed on the ground surface 1a is wound and covered with the winding material 21. The winding material 21 is a soil material such as soil, sand or crushed stone, or a cement-based material such as mortar or concrete.

In the example shown in FIG. 5B, the horizontal freezing pipe 15 installed on the ground surface 1a is wound and covered with the winding material 21. Then, the heat insulating material 17 is laid on the ground surface 1a on both sides of the winding material 21 from the upper side of the winding material 21.

In the example shown in FIG. 5C, the upper surface and the side surface of the horizontal freezing pipe 15 installed on the ground surface 1a are covered with the heat insulating material 17a, and the ground surfaces 1a on both sides of the heat insulating material 17a are laid with the heat insulating material 17. The heat insulating material 17a may be in the same sheet shape as the heat insulating material 17, may be in the shape of a block or shell, or may be formed by spraying.

6 and 7 are views showing an example in which a horizontal freezing pipe 15 installed in a groove-shaped excavated portion 23 formed on the ground surface 1a near the freezing pipe arrangement line 3 and another configuration are combined.

In the example shown in FIG. 6, a groove-shaped excavated portion 23 is formed on the ground surface 1a near the freezing pipe arrangement line 3, and a horizontal freezing pipe 15 is installed on the excavated portion 23. Then, the heat insulating material 17 is laid on the ground surface 1a near the freezing pipe arrangement line 3.

In the example shown in FIG. 7A, a groove-shaped excavated portion 23 is formed on the ground surface 1a near the freezing pipe arrangement line 3, and a horizontal freezing pipe 15 is installed in the excavated portion 23. Then, the excavated portion 23 is reclaimed with the backfill material 25 to cover the horizontal freezing pipe 15. The backfill material 25 is a soil material such as soil, sand or crushed stone, or a cement-based material such as mortar or concrete. As a method of constructing the backfill material 25, for example, a method of manually tamping, spraying with a spraying machine, pouring, or the like can be considered, and an appropriate material is selected depending on the properties of the material.

In the example shown in FIG. 7B, the horizontal freezing pipe 15 is installed in the groove-shaped excavated portion 23 formed on the ground surface 1a near the freezing pipe arrangement line 3, and the excavated portion 23 is filled with the backfill material 25 to be horizontal. Cover the freezing tube 15. Then, the heat insulating material 17 is laid on the ground surface 1a near the freezing pipe arrangement line 3.

In the example of covering the horizontal freezing pipe 15 with the winding material 21 and the backfilling material 25, the cooling heat from the horizontal freezing pipe 15 is transmitted to the ground 1 through the winding material 21 and the backfilling material 25, and the ground 1 is transferred to the ground 1. Be cooled. Further, in the example in which the heat insulating material is laid on the surface of the horizontal freezing pipe 15 and the ground surface 1a, the heat insulating material 17 traps cold air between the horizontal freezing pipe 15 and the ground surface 1a, and the cold air is passed through. The ground 1 is cooled. When the winding material 21, the backfill material 25, and the heat insulating material are used in combination, the cold heat of the horizontal freezing pipe 15 can be most effectively transferred to the ground 1 by a synergistic effect.

FIG. 8 is a diagram showing an example in which a freezing propulsion means other than the horizontal freezing tube 15 is used. In the example shown in FIG. 8A, the heat insulating material 17 is laid on the ground surface 1a near the freezing pipe arrangement line 3. This makes it possible to prevent the cold heat from the freezing tube 5 from escaping.

In the example shown in FIG. 8B, a container 27 for supplying the refrigerant 29 is installed in the vicinity of the ground surface 1a near the freezing pipe arrangement line 3. Further, the heat insulating material 17 is laid on the ground surface 1a near the freezing pipe arrangement line 3. Then, the refrigerant 29 such as ice or cold water is injected into the container 27 through the injection port 31. As a result, the cold heat of the refrigerant 29 is transmitted to the ground 1 via the container 27, and the ground 1 is cooled. Further, the heat insulating material 17 can prevent the cold heat from the refrigerant 29 from escaping.

In the example shown in FIG. 8C, a heat insulating material is laid on the ground surface 1a near the freezing pipe arrangement line 3. Further, the awning member 33 is installed above the above-ground portion 13 of the freezing pipe 5. As a result, the above-ground portion 13 of the freezing pipe 5 is prevented from being warmed by the outside air temperature or sunlight, and the heat is not transmitted to the ground 1 near the ground surface 1a via the freezing pipe 5.

As described above, even when various freezing propulsion means shown in FIGS. 5 to 8 are used, it is possible to prevent the temperature of the ground 1 from rising in the vicinity of the ground surface 1a, which tends to warm up. If various freezing propulsion means shown in FIGS. 5 to 8 are used at the time of creating the frozen soil 11, the frozen soil 11 having a predetermined thickness 18 can be created in a short period of time. If various freezing propulsion means shown in FIGS. 5 to 8 are used during the maintenance of the frozen soil 11, the formation of the frozen soil 11 can be promoted and the thickness defect portion 19 can be eliminated.

Further, in the second embodiment, as the freezing suppressing means, the freezing pipe valve 35 or the header pipe valve 41 is opened and closed to perform intermittent operation of the freezing pipe 5, but the freezing suppressing means is not limited to this. As a freeze suppressing means, a thinning operation of the freezing tube 5 may be performed.

FIG. 9 is a diagram showing an operation method of the thinning operation. FIG. 9A is a diagram showing changes in the underground temperature when the thinning operation is performed. The vertical axis of FIG. 9A is the underground temperature at the position of the temperature measuring tube 7, and the horizontal axis is the period. The control reference value 59 and the control reference value 61 are, for example, the same values as in the intermittent operation in the second embodiment. The solid line 63, the broken line 65, and the broken line 67 are examples of the underground temperature at the position of the temperature measuring tube 7 in the section 47, and may be the temperature at a specific measurement depth or the average temperature at all depths.

FIG. 9B is a diagram showing an operation switching state of the freezing pipe 5 in the section 47. In FIG. 9B, the freezing tube 5 in operation is shown with diagonal lines, and the freezing tube 5 in operation is shown without diagonal lines.

As shown in FIG. 9A, in the construction operation period 51 of the frozen soil type impermeable wall 9, the underground temperature at the position of the temperature measuring tube 7 decreases with the passage of time. During the construction operation period 51, as shown in the uppermost stage of FIG. 9B, the total freezing pipe 5 of the section 47 is operated. Then, when it is determined that the underground temperature is sufficiently lowered and the frozen soil type impermeable wall 9 having a predetermined thickness 18 is constructed, the maintenance operation period 53 of the frozen soil type impermeable wall 9 is started.

In the maintenance operation period 53, when the underground temperature of all the temperature measuring pipes 7 in the section 47 becomes the control reference value 59 or less, the freezing pipes 5 to be operated are thinned out to reduce the number of pipes. For example, as shown in the second stage of FIG. 9B, every other freezing pipe 5 in the section 47 is operated. As a result, when the underground temperature stabilizes between the control reference value 59 and the control reference value 61 as shown by the solid line 63, the thinning operation is continued as it is.

Even if every other freezing pipe 5 is operated, if the underground temperature continues to decrease as shown by the broken line 67, the freezing pipe 5 to be operated is operated as shown in the third stage of FIG. 9B. Further reduce and strengthen thinning. After that, when the underground temperature rises and stabilizes between the control reference value 59 and the control reference value 61 as shown by the broken line 67, the operation is continued with the thinning strengthened.

When the underground temperature exceeds the control reference value 61 as shown by the broken line 65 by operating every other freezing pipe 5, the freezing is operated as shown in the lowermost stage of FIG. 9 (b). Increase the number of tubes 5 to ease the thinning. After that, when the underground temperature drops and stabilizes between the control reference value 59 and the control reference value 61 as shown by the broken line 65, the operation is continued in a state where the thinning is relaxed.

In this way, even when the thinning operation of the freezing pipe 5 is performed, the underground temperature is maintained in an appropriate range and the excessive formation of the frozen soil 11 is prevented, as in the case of the intermittent operation of the freezing pipe 5. The thickness of the frozen soil 11 can be maintained at an appropriate level. The number of thinned freezing tubes 5 is adjusted by opening and closing the freezing tube valve 35 shown in FIG. 3A, but the operation of the freezing tube valve 35 accompanying the adjustment is basically once at the beginning of the maintenance operation period 53. Since it is only performed, the burden of on-site work is less than that of intermittent operation, and the exposure of workers in a radiation environment is suppressed.

As the freeze suppressing means, the temperature of the frozen refrigerant may be raised in addition to the intermittent operation and the thinning operation of the freezing pipe 5. Since the timing of changing the temperature of the frozen refrigerant is similar to the timing of changing the number of thinning operations, it will be described with reference to FIG. 9A.

In the construction operation period 51 shown in FIG. 9A, for example, the temperature of the frozen refrigerant is operated at −30 ° C. Then, when it is determined that the underground temperature has sufficiently decreased and the frozen soil type impermeable wall 9 having a predetermined thickness of 18 has been constructed, the maintenance operation period 53 is entered and the temperature of the frozen refrigerant is set to, for example, −20 ° C. Raise. When the underground temperature stabilizes between the control reference value 59 and the control reference value 61 as shown by the solid line 63, the operation is continued using the frozen refrigerant at −20 ° C.

Even if the temperature of the frozen refrigerant is −20 ° C., if the underground temperature continues to decrease as shown by the broken line 67, the temperature of the frozen refrigerant is increased to, for example, −10 ° C. Then, when the underground temperature rises and stabilizes between the control reference value 59 and the control reference value 61 as shown by the broken line 67, the operation is continued using the frozen refrigerant at −10 ° C.

By setting the temperature of the frozen refrigerant to −20 ° C., when the underground temperature exceeds the control reference value 61 as shown by the broken line 65, the temperature of the frozen refrigerant is lowered to, for example, −25 ° C. Then, when the underground temperature drops and stabilizes between the control reference value 59 and the control reference value 61 as shown by the broken line 65, the operation is continued using the frozen refrigerant at −25 ° C.

In this way, even when the temperature of the frozen refrigerant is raised, the underground temperature is kept within an appropriate range, the excessive formation of the frozen soil 11 is prevented, and the frozen soil is prevented from being excessively formed, as in the case of performing the intermittent operation of the freezing pipe 5. The thickness of 11 can be maintained moderately. Since the temperature of the frozen refrigerant can be adjusted without opening and closing the freezing pipe valve 35 or the header pipe valve 41, it can be easily performed.

In each freeze suppressing means, the control reference values 59 and 61 are not limited to the above-mentioned values. Further, as shown by the broken line 67 in FIG. 9A, when the thinning operation or the temperature rise of the frozen refrigerant has already been carried out but the effect is insufficient, the number of operating freezing tubes 5 and the temperature of the frozen refrigerant may be increased. A reference value for making a decision on switching may be set. For example, another control standard value may be set on the lower temperature side than the control standard value 59, or the elapsed time from the thinning operation or the temperature rise of the frozen refrigerant until the temperature reaches the control standard value 59 or higher. A limit value may be set.

It is desirable not to use the freeze suppressing means in the special parts shown in FIGS. 10 and 11. FIG. 10 is a diagram showing the periphery of the obstacle 69, and FIG. 11 is a diagram showing a joint portion between the sheet pile type underground impermeable wall and the frozen soil type impermeable wall 9.

In the example shown in FIG. 10, since the obstacle 69 exists in the ground 1 and the freezing pipe 5 cannot be arranged at a predetermined pitch, both sides of the obstacle 69 are for the purpose of promoting freezing of the ground above and below the obstacle 69. A double-row freezing tube 5a is additionally provided so as to sandwich the above. Since the frozen soil 11 is not sufficiently formed in such a portion, there is a high possibility that melting will occur due to the weakening of the cooling force when the freeze suppressing means is applied. Therefore, the freezing pipes on both sides of the unfrozen portion 71 in which the frozen soil 11 is not closed (the double-row portion freezing pipe 5a, the freezing pipe 5 adjacent to the obstacle 69 and sandwiched between the double-row portion freezing pipe 5a) It is desirable to continue the same operation as during the construction operation without applying the freeze suppression means.

In the examples shown in FIGS. 11A and 11B, the steel pipe sheet pile 73 and the steel sheet pile 75 installed in the ground 1 are joined to the frozen soil type impermeable wall 9. The tops of the steel pipe sheet pile 73 and the steel sheet pile 75 project into the air or the sea, and are easily warmed by the outside air temperature, sunlight, water temperature, and the like. Moreover, since the thermal conductivity is higher than that of the surrounding ground 1, the temperature of the ground 1 rises at the joint between the steel pipe sheet pile 73 or the steel sheet pile 75 and the frozen soil type impermeable wall 9, and the frozen soil 11 tends to melt. Therefore, it is desirable that the freezing pipe 5 near the joint between the steel pipe sheet pile 73 and the steel sheet pile 75 and the frozen soil type impermeable wall 9 does not apply the freezing suppression means and continues the same operation as during the construction operation.

Here, when the freezing suppression means is an intermittent operation or a thinning operation of the freezing pipe 5, the freezing pipe 5 of the special portion shown in FIGS. 10 and 11 is not subject to the intermittent operation or the thinning operation, so that the construction operation is performed. It is possible to continue the same operation as at the time. When raising the temperature of the frozen refrigerant as a means for suppressing freezing, it is necessary to prepare equipment for cooling the special parts shown in FIGS. 10 and 11 in a system different from that for cooling the entire frozen soil type impermeable wall 9. There is.

The opening / closing operation of the freezing pipe valve 35 and the header pipe valve 41 when performing intermittent operation or thinning operation as the antifreezing means may be performed by remote control or automation for changing the temperature of the frozen refrigerant. In this case, for example, an electromagnetic valve is used for the freezing pipe valve 35 and the header pipe valve 41. By adopting remote control or automation, it is possible to save labor in the field work and improve the work environment.

Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person skilled in the art can come up with various modified examples or modified examples within the scope of the technical idea disclosed in the present application, and these also naturally belong to the technical scope of the present invention. Understood.

1 ………… Ground 1a ………… Ground surface 3 ………… Freezing pipe arrangement line 5 ………… Freezing pipe 5a ………… Double row freezing pipe 7 ………… Temperature measuring pipe 9 ………… Frozen soil type impermeable wall 11 ………… Frozen soil 13 ………… Above ground 15 ………… Horizontal freezing pipe 17, 17a ………… Insulation material 18 ………… Predetermined thickness 19 ………… Thickness defect 20, 47 ………… Section 21… …… Winding material 23 ………… Excavated part 25 ………… Backfilling material 27 ………… Container 29 ………… Refrigerator 31 ………… Injection port 33 ………… Awning member 35 ………… Freezing pipe valve 37 …… … Feeding header pipe 39 ………… Returning header pipe 41 ………… Header pipe valve 43 ………… Feeding brine pipe 45 ………… Returning brine pipe 49, 63 ………… Solid line 51 ………… Construction operation period 53 ………… Maintenance operation period 55 ………… Stop period 57 ………… Recirculation period 59, 61 ………… Management standard value 65, 67 ………… Broken line 69 ………… Obstacle 71 ………… Unfrozen part 73 ………… Steel pipe sheet pile 75 ………… Steel sheet pile 77 ………… Frozen upper part

Claims (11)

In the frozen soil type impermeable wall created by arranging a plurality of freezing pipes on the freezing pipe arrangement line of the ground and circulating the frozen refrigerant through the freezing pipes to form frozen soil.
In the section where the thickness of the frozen soil is determined to be larger than the predetermined thickness, a freezing suppressing means for suppressing the formation of the frozen soil is used.
In the section where the thickness of the frozen soil is determined to be smaller than the predetermined thickness, a freezing propulsion means for promoting the formation of the frozen soil is used .
A method for maintaining frozen soil, which comprises installing a horizontal freezing pipe on the ground surface near the freezing pipe arrangement line as the freezing propulsion means . In the frozen soil type impermeable wall created by arranging a plurality of freezing pipes on the freezing pipe arrangement line of the ground and circulating the frozen refrigerant through the freezing pipes to form frozen soil.
In the section where the thickness of the frozen soil is determined to be larger than the predetermined thickness, a freezing suppressing means for suppressing the formation of the frozen soil is used.
In the section where the thickness of the frozen soil is determined to be smaller than the predetermined thickness, a freezing propulsion means for promoting the formation of the frozen soil is used .
A method for maintaining frozen soil, which comprises installing a horizontal freezing pipe in a groove-shaped excavated portion formed on the ground surface near the freezing pipe arrangement line as the freezing propulsion means . The method for maintaining frozen soil according to claim 1 or 2 , wherein as the freezing propulsion means, a heat insulating material is laid on the ground surface near the freezing pipe arrangement line. The method for maintaining frozen soil according to any one of claims 1 to 3, wherein the horizontal freezing pipe is covered with a soil material or a cement-based material. The method for maintaining frozen soil according to any one of claims 1 to 4 , wherein as the freezing propulsion means, a sunshade member is installed above the above-ground portion of the freezing pipe. As the freeze suppressing means, the freezing pipe valve provided in the freezing pipe or the header pipe valve provided in the header pipe which is the main pipe of the freezing pipe is opened and closed to perform intermittent operation of the freezing pipe. The method for maintaining frozen soil according to any one of claims 1 to 5 . The invention according to any one of claims 1 to 5 , wherein as the freezing suppressing means, a part of the freezing tube valve provided in the freezing tube is opened and closed to perform a thinning operation of the freezing tube. How to maintain frozen soil. The method for maintaining frozen soil according to any one of claims 1 to 7 , wherein as the freeze suppressing means, the temperature of the frozen refrigerant is raised. The underground temperature in or near the frozen soil is continuously measured, the thickness of the frozen soil is estimated based on the underground temperature, and the section using the freezing suppressing means and the section using the freezing propulsion means. The method for maintaining frozen soil according to any one of claims 1 to 8 , wherein the method is set. Frozen soil method This is a method of creating frozen soil in an impermeable wall.
Step a of installing a plurality of freezing pipes on the freezing pipe arrangement line of the ground, and
A step b of creating frozen soil by circulating a frozen refrigerant inside the plurality of freezing pipes while using a freezing propulsion means for preventing a temperature rise near the ground surface.
Equipped with
A method for creating frozen soil, which comprises installing a horizontal freezing pipe on the ground surface near the freezing pipe arrangement line as the freezing propulsion means . Frozen soil method This is a method of creating frozen soil in an impermeable wall.
Step a of installing a plurality of freezing pipes on the freezing pipe arrangement line of the ground, and
A step b of creating frozen soil by circulating a frozen refrigerant inside the plurality of freezing pipes while using a freezing propulsion means for preventing a temperature rise near the ground surface.
Equipped with
As the freezing propulsion means, a method for creating frozen soil, characterized in that a horizontal freezing pipe is installed in a groove-shaped excavated portion formed on the ground surface near the freezing pipe arrangement line .

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