Freezing system and freezing structure construction method
The freezing system with clustered and spaced freezing pipes, along with heat transfer materials, addresses the issue of unplanned soil formation during prolonged freezing by controlling the freezing range, ensuring efficient and stable ground freezing.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- KAJIMA CORP
- Filing Date
- 2022-08-24
- Publication Date
- 2026-05-12
AI Technical Summary
Existing freezing methods form unplanned frozen soil over a wide area due to prolonged freezing periods, leading to irreversible ground consolidation and settlement, which conventional measures like limited freezing pipes and ground improvement fail to adequately address.
A freezing system with clustered freezing pipes inside a casing and spaced freezing pipes below the casing, combined with heat transfer materials in boreholes, allows controlled formation of planned frozen soil while suppressing unplanned soil formation.
Enables precise control over the freezing range, forming planned frozen soil efficiently while minimizing unplanned soil formation, even with extended freezing periods, reducing labor and ensuring ground stability.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a freezing system and a method for constructing a freezing structure.
Background Art
[0002] As shown in FIG. 8(a), the freezing method is a method of forming frozen soil 103 by installing freezing pipes 102 in the ground 101 and circulating a cooling medium to freeze the moisture in the ground. The frozen soil 103 is used as a water barrier or a bearing wall. At this time, if the temperature of the cooling medium is too low or the freezing period is too long, the ground 101 around the frozen soil 103 is consolidated in the direction indicated by the arrow due to freezing expansion. Since the earth pressure is small in the shallow part of the ground 101, the freezing expansion amount and the consolidation amount are larger than those in the deep part. However, since consolidation is an irreversible change, even if the freezing is terminated and the frozen soil 103 melts, the consolidated part around does not return to its original position. Therefore, as shown in FIG. 8(b), a melting part 105 containing a large amount of moisture undergoes self-weight consolidation to generate a settlement part 104.
[0003] In order to suppress the settlement after the melting of the frozen soil, there are measures such as limiting the freezing range using limited freezing pipes (see, for example, Patent Document 1) and increasing the rigidity of the ground by ground improvement such as jet grouting.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, even when using limited freezing pipes, it is impossible to completely insulate between the ground and the freezing pipes. Therefore, when the freezing period becomes long, unplanned frozen soil is formed in a wide range of the ground, and the surrounding ground is consolidated. In addition, it is difficult to restore the ground after ground improvement.
[0006] This invention has been made in view of the aforementioned problems, and its objective is to provide a freezing system and a freezing structure construction method that can control the freezing range even when the freezing period is prolonged. [Means for solving the problem]
[0007] To achieve the aforementioned objective, the first invention comprises a plurality of freezing pipes arranged underground, through which a cooling medium flows, and a casing into which the plurality of freezing pipes are inserted within a predetermined range from the ground surface, wherein the plurality of freezing pipes are clustered together inside the casing, and below the casing, the plurality of freezing pipes are arranged so as to increase the spacing between them. Below the casing, boreholes are formed into which each of the freezing pipes is inserted, and the inside of the boreholes is filled with heat transfer material. This freezing system is characterized by the following features.
[0008] In the first invention, in the range from the ground surface to a predetermined depth, multiple freezing pipes are arranged together inside the casing, and in a plan view, the cold from the freezing pipes is transmitted only to the ground surrounding the casing, suppressing the formation of frozen soil. In the range below the casing, multiple freezing pipes are arranged with wider spacing between them, and in a plan view, the cold from the freezing pipes is transmitted to a wide area of the ground, promoting the formation of frozen soil. This ensures the formation of planned frozen soil, while at the same time actively controlling the range of ground freezing so that the formation of unplanned frozen soil is suppressed to a small extent even if the freezing period is prolonged.
[0009] Also Below the casing, boreholes are formed into which each of the freezing pipes is inserted, and the inside of the boreholes is filled with heat transfer material. toni This allows cold air to be more easily transferred from the freezing pipes located below the casing to the ground, enabling more efficient formation of frozen soil in the ground below the casing.
[0010] It is desirable that insulating means be arranged inside the casing and on the outer periphery of the plurality of freezing tubes. This makes it more difficult for cold air to be transferred from the freezing pipes placed inside the casing to the ground, allowing for a more reliable reduction of the frozen soil that forms in the ground around the casing.
[0011] It is preferable that the freezing tube be an aluminum microchannel. This allows the freezing pipe to be easily inserted into the curved borehole formed below the casing, matching its shape.
[0012] The second invention comprises the steps of: installing a casing in the ground to a predetermined depth; forming a plurality of excavation holes below the casing so as to spread outward from the center; inserting a freezing pipe into each of the excavation holes through the casing; and flowing a cooling medium through the freezing pipe to freeze a predetermined part in the ground. Furthermore, in the process of forming the borehole, drilling is performed while filling the borehole with a filling liquid that functions as a heat transfer member. This is a construction method for frozen structures characterized by the following features.
[0013] In the second invention, multiple freezing pipes are arranged together inside the casing from the ground surface to a predetermined depth, and the cold from the freezing pipes is transmitted only to the ground surrounding the casing in a plan view, thereby suppressing the formation of frozen soil. In the area below the casing, multiple freezing pipes are arranged with wider spacing between them, and the cold from the freezing pipes is transmitted to a wider area of the ground in a plan view, thereby promoting the formation of frozen soil. This allows for the reliable formation of planned frozen soil, while at the same time suppressing the formation of unplanned frozen soil on a small scale even if the freezing period is prolonged, by actively controlling the freezing range of the ground during construction. [Effects of the Invention]
[0014] According to the present invention, it is possible to provide a freezing system and a freezing structure construction method that can control the freezing range even if the freezing period is prolonged. [Brief explanation of the drawing]
[0015] [Figure 1] A vertical cross-sectional view of the freezing system 6. [Figure 2] A horizontal cross-sectional view of the freezing system 6. [Figure 3] Cross-sectional view of freezing pipe 3. [Figure 4] A diagram showing the drilling process for borehole 4. [Figure 5] A view showing the state where the drilling of the drilling hole 4 has been completed. [Figure 6] A vertical cross-sectional view of the freezing system 6 during operation. [Figure 7] A vertical cross-sectional view of the freezing system 6a. [Figure 8] A view showing the freezing method.
Mode for Carrying Out the Invention
[0016] Hereinafter, a first embodiment of the present invention will be described in detail based on the drawings.
[0017] FIG. 1 is a vertical cross-sectional view of the freezing system 6, and FIG. 2 is a horizontal cross-sectional view of the freezing system 6. FIG. 2(a) shows a cross-section taken along line A-A of FIG. 1, and FIG. 2(b) shows a cross-section taken along line B-B of FIG. 1. FIG. 3 is a cross-sectional view of the freezing pipe 3.
[0018] As shown in FIG. 1, the freezing system 6 includes a freezing pipe 3, a casing 2, a heat insulating member 16, a heat transfer member 12, etc. The freezing pipe 3 is a pipe for forming frozen soil in the ground 1 by flowing a cooling medium inside. The casing 2 is arranged in a range from the surface of the ground 1 to a predetermined depth, and a plurality of drilling holes 4 equal in number to the freezing pipes 3 are formed below the casing 2. Each freezing pipe 3 is inserted into the inside of the casing 2 and the inside of the drilling hole 4.
[0019] As shown in FIGS. 1 and FIG. 2(a), a plurality of freezing pipes 3 are collectively arranged inside the casing 2. Inside the casing 2, a heat insulating member 16, which is a heat insulating means, is arranged on the outer peripheral portion of each freezing pipe 3.
[0020] As shown in Figures 1 and 2(b), the boreholes 4 below the casing 2 are formed such that the spacing between the straight sections 18 is increased by curved sections 17 that extend outward from the casing 2. That is, the curved sections 17 of the multiple boreholes 4 are arranged radially with the casing 2 as the center in a plan view. The multiple freezing pipes 3 are arranged below the casing 2 so that they are spaced apart from each other by being inserted into different boreholes 4. The inside of the boreholes 4 is filled with a heat transfer material 12. The heat transfer material 12 is, for example, water or cement bentonite, and is filled to facilitate the transfer of the cold and heat of the cooling medium flowing through the freezing pipes 3 to the ground 1.
[0021] In the ground 1, the area from the surface to a predetermined depth is a freezing suppression range 5 where the formation of frozen soil is suppressed by the freezing pipe 3. In the freezing system 6, it is desirable that the curved section 17 of the excavation hole 4 is located below the freezing suppression range 5, and the straight section 18 is located below the freezing suppression range 5.
[0022] As shown in Figure 3, the freezing tube 3 is an aluminum microchannel manufactured, for example, as an aluminum extruded product. Multiple refrigerant circulation channels 7 are provided in parallel within the freezing tube 3.
[0023] Next, the method for constructing a frozen structure using the freezing system 6 will be described. Figure 4 is a vertical cross-sectional view showing the state of drilling the borehole 4, and Figure 5 is a vertical cross-sectional view showing the state after drilling the borehole 4 has been completed. To construct a frozen structure using the freezing system 6, first, as shown in Figure 4, a casing 2 is erected in the ground 1 to a predetermined depth. Then, a drilling rod 8, which has a drilling section 9 at its tip, is passed through the casing 2, and below the casing 2, a curved boring is performed so that it spreads outward from the center by the curved section 17 as shown by arrow C, thereby forming a borehole 4. The borehole 4 is drilled while filling it with a filling liquid 10 such as cement bentonite to protect the borehole wall, and the drilling rod 8 is withdrawn after the borehole 4 is formed.
[0024] As shown in Figure 5, once multiple boreholes 4 have been formed, the freezing pipes 3 are inserted into each borehole 4 via the casing 2, as shown in Figure 1, to complete the installation of the freezing system 6. At this time, the packing material 10 functions as a heat transfer member 12. Alternatively, a lining material may be placed on the inner surface of each borehole 4 in advance. As a method for installing the lining material into the boreholes 4, for example, the method disclosed in Japanese Patent No. 457916 can be applied. In this case, the lining material can be used as a guide when inserting the freezing pipes 3 into the boreholes 4.
[0025] Figure 6 is a vertical cross-sectional view of the freezing system 6 in operation. Once the installation of the freezing system 6 is complete, the ground 1 is frozen by flowing the cooling medium 11 through the freezing pipes 3, as shown in Figure 6. The cooling medium 11 is a CO2 refrigerant. When the cooling medium 11 is flowed through the freezing pipes 3 using the freezing system 6, the planned frozen soil 13 is formed over a wide area below the freezing suppression area 5 of the ground 1 because multiple freezing pipes 3 are scattered. In the freezing suppression area 5, multiple freezing pipes 3 are densely packed inside the casing 2, so a smaller area of frozen soil 14 is formed than the planned frozen soil 13.
[0026] In this embodiment, in the range from the surface of the ground 1 to a predetermined depth, multiple freezing pipes 3 are arranged together inside the casing 2, and the cold from the freezing pipes 3 is transmitted only to the ground 1 surrounding the casing 2 in a plan view, thereby suppressing the formation of frozen soil 14. In the range below the casing 2, multiple freezing pipes 3 are arranged with wider spacing between them, and the cold from the freezing pipes 3 is transmitted to a wide area of the ground 1 in a plan view, thereby promoting the formation of planned frozen soil 13. This ensures the reliable formation of planned frozen soil 13, while also actively controlling the freezing range of the ground 1 so that the formation of unplanned frozen soil 14 is suppressed to a small extent even if the freezing period is prolonged.
[0027] In this embodiment, by first placing the casing 2 in the ground 1 within the freezing suppression area 5, the labor required to drill multiple boreholes 4 can be reduced. Furthermore, by inserting them into the casing 2, multiple freezing pipes 3 can be easily placed in close proximity.
[0028] The configuration of the freezing system is not limited to that shown in this embodiment. For example, the borehole 4 does not have to have a straight section 18 below the curved section 17; it may have a shape that widens outward from the center below the casing 2. The freezing tubes 3 are not limited to aluminum microchannels, and the number of freezing tubes 3 does not have to be nine.
[0029] In addition to the insulating member 16, an air layer may be secured between the casing 2 and the freezing pipe 3 as an insulating means. Figure 7 is a vertical cross-sectional view of the freezing system 6a. In the freezing system 6a, an air layer is provided between the casing 2 and the freezing pipe 3 as an insulating means. The air supply pipe 15 is also positioned so that its lower end is slightly above the lower end of the casing 2. In the freezing system 6a, the cooling medium 11 is flowed through the freezing pipe 3 to freeze the ground 1, and a fluid such as air is flowed through the air supply pipe 15. As shown by arrow D, the fluid is supplied from the lower end of the air supply pipe 15 in the space inside the casing 2 and discharged to the ground. In the freezing suppression range 5, a smaller area of frozen soil 14a is formed than the planned frozen soil 13 due to the insulating effect of the air layer and the supply of air.
[0030] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the technical idea disclosed herein, and these will naturally also fall within the technical scope of the present invention. [Explanation of Symbols]
[0031] 1, 101……ground 2…Casing 3, 102……Freezing tube 4...Drilled hole 5…Freezing suppression range 6, 6a... Freezing system 7… Refrigerant circulation path 8…Drilling Rod 9...Excavation section 10……Filling liquid 11……Cooling medium 12… Heat transfer components 13... Planned frozen soil 14, 14a……Frozen soil 15………Air supply tube 16………Insulation material 17...Bend 18...Straight section 104……Sinking part 105... Melting section
Claims
1. Multiple freezing pipes are placed underground, through which a cooling medium flows, A casing into which multiple freezing pipes are inserted within a predetermined range from the ground surface, It is equipped with, Inside the casing, a plurality of the freezing tubes are clustered together, and below the casing, they are arranged so that the spacing between the plurality of freezing tubes increases. A freezing system characterized in that a borehole is formed below the casing into which each of the freezing pipes is inserted, and the inside of the borehole is filled with a heat transfer member.
2. The freezing system according to claim 1, characterized in that insulating means are arranged inside the casing and on the outer periphery of the plurality of freezing tubes.
3. The freezing system according to claim 1, characterized in that the freezing tube is an aluminum microchannel.
4. The process involves installing the casing into the ground to a predetermined depth, The process involves forming multiple boreholes below the casing so as to spread outward from the center, The process involves inserting the freezing pipes into each of the excavated holes via the casing, The process involves flowing a cooling medium through the freezing pipe to freeze a predetermined area underground, It is equipped with, A method for constructing a frozen structure, characterized in that, in the step of forming the borehole, the borehole is drilled while filling it with a filling liquid that functions as a heat transfer member.