Freezing system and method for suppressing ground subsidence

Abstract

To provide a freezing system and a ground settlement suppression method capable of actively controlling a frozen range and facilitating ground restoration.SOLUTION: A freezing pipe 3 having a heat insulating material 7 formed therearound is placed underground at least in a predetermined range from the ground surface, and steel sheet piles 10 as a ground expansion regulating member are arranged so as to surround a periphery of at least a part of the heat insulating material 7 at a predetermined depth from the ground surface, to construct a freezing system 12. Then, after flowing a cooling medium 15 through the freezing pipe 3 to freeze a predetermined part underground, circulation of the cooling medium 15 to the freezing pipe 3 is stopped to thaw the frozen soil, and a settlement portion 16 inside the steel sheet piles 10 is back-filled.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a freezing system and a method for suppressing ground settlement.

Background Art

[0002] As shown in Fig. 5(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. In the shallow layer of the ground 101 with low earth pressure, the amount of freezing expansion and the amount of consolidation are larger than those in the deep layer. However, since consolidation is an irreversible change, even if the freezing is terminated and the frozen soil 103 melts, the consolidated part around it will not return to its original position. Therefore, as shown in Fig. 5(b), the 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 (for example, see 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 if limited freezing pipes are used, it is impossible to completely insulate between the ground and the freezing pipes. Therefore, if the freezing period becomes long, unplanned frozen soil is formed and the surrounding ground is consolidated. In addition, it is difficult to restore the ground if ground improvement is carried out.

[0006] This invention has been made in view of the aforementioned problems, and its objective is to provide a freezing system and a ground subsidence suppression method that can actively control the freezing range and facilitate ground restoration. [Means for solving the problem]

[0007] To achieve the aforementioned objectives, the first invention comprises: a freezing pipe placed underground through which a cooling medium flows; an insulating means disposed on the outer circumference of the freezing pipe within a predetermined range from the ground surface; and a ground expansion regulating member disposed to surround at least a portion of the insulating means to a predetermined depth from the ground surface. Furthermore, at least the upper part of the ground expansion restricting member is provided with a connecting member that connects opposing ground expansion restricting members. This freezing system is characterized by the following features.

[0008] In the first invention, the freezing range of the ground can be actively controlled by arranging an insulating means on the outer circumference of the freezing pipe. Furthermore, by arranging a ground expansion restricting member from the ground surface to a predetermined depth, consolidation due to freezing expansion of the ground outside the ground expansion restricting member in the shallow part of the ground can be prevented, thereby suppressing ground settlement. Moreover, since the range of ground settlement can be limited to the inside of the ground expansion restricting member, recovery after the thawing of the frozen soil is easier. Furthermore, deformation of the ground expansion regulating member can be prevented near the ground surface where horizontal forces are easily applied due to freezing expansion.

[0009] The second invention is a freezing system comprising: a freezing pipe placed underground through which a cooling medium flows; an insulating means placed on the outer circumference of the freezing pipe within a predetermined range from the ground surface; and a ground expansion restricting member placed to surround at least a portion of the insulating means to a predetermined depth from the ground surface, wherein a heating device is placed on the ground expansion restricting member. In the second invention, by arranging an insulating means on the outer circumference of the freezing pipe, the freezing range of the ground can be actively controlled. Furthermore, by arranging a ground expansion restricting member from the ground surface to a predetermined depth, consolidation due to freezing expansion of the ground outside the ground expansion restricting member in the shallow layer of the ground can be prevented, thereby suppressing ground settlement. Moreover, since the range of ground settlement can be limited to the inside of the ground expansion restricting member, recovery after the thawing of the frozen soil is easier. In addition, the ground around the ground expansion restricting member can be heated to prevent freezing. It is desirable that the ground expansion regulating member be positioned outside the portion of the heat insulation means that is intended to freeze. As a result, even if the ground surrounding the insulating means freezes while the freezing system is in operation, the frozen soil is restrained by the ground expansion restricting member, thus preventing consolidation of the ground outside the ground expansion restricting member.

[0010] The third invention is a method for suppressing ground subsidence, comprising the steps of: placing a freezing pipe in the ground having an insulating means formed around it in a predetermined range from the ground surface; placing a ground expansion restricting member at a predetermined depth from the ground surface so as to surround at least a part of the insulating means; connecting the ground expansion restricting members at least above the ground expansion restricting member with a connecting member that connects opposing ground expansion restricting members; flowing a cooling medium through the freezing pipe to freeze a predetermined part in the ground; stopping the circulation of the cooling medium to the freezing pipe to thaw the frozen soil; and backfilling the subsided area inside the ground expansion restricting member.

[0011] In the third invention, the freezing range of the ground can be actively controlled by forming an insulating means on the outer circumference of the freezing pipe. Furthermore, by arranging a ground expansion restricting member, consolidation due to freezing expansion of the ground outside the ground expansion restricting member in the shallow part of the ground can be prevented, thereby suppressing ground settlement. In particular, deformation of the ground expansion restricting member can be prevented near the ground surface where horizontal forces are easily applied due to freezing expansion. Moreover, since the range of ground settlement can be limited to the inside of the ground expansion restricting member, recovery after the thawing of the frozen soil is easier.

[0012] The 4The invention includes the steps of disposing a freezing pipe having heat insulation means formed around it in at least a predetermined range from the ground surface into the ground, and disposing a ground expansion restraint member so as to surround at least a part of the heat insulation means at a predetermined depth from the ground surface. The steps include: placing a heating device on the ground expansion regulating member; A step of flowing a cooling medium through the freezing pipe to freeze a predetermined part of the ground, and a step of stopping the circulation of the cooling medium to the freezing pipe , by the heating device A step of melting the frozen soil, and a step of backfilling the subsidence part inside the ground expansion restraint member, and is a ground subsidence suppression method characterized by comprising these steps.

[0013] No. 4 In the invention, by forming heat insulation means on the outer peripheral part of the freezing pipe, the freezing range of the ground can be actively controlled. Further, by disposing a ground expansion restraint member, it is possible to prevent consolidation due to freezing expansion of the ground outside the ground expansion restraint member in the shallow layer of the ground and suppress ground subsidence. Furthermore, the ground around the ground expansion regulating member can be heated to prevent freezing. Furthermore, since the range where the subsidence part occurs in the ground can be limited inside the ground expansion restraint member, it is easy to recover after the frozen soil melts.

Effects of the Invention

[0014] According to the present invention, it is possible to provide a freezing system and a ground subsidence suppression method capable of actively controlling the freezing range and facilitating the recovery of the ground.

Brief Description of the Drawings

[0015] [Figure 1] Vertical cross-sectional view of the freezing system 12. [Figure 2] Horizontal cross-sectional view of the freezing system 12. [Figure 3] Vertical cross-sectional view of the freezing system 12 during operation. [Figure 4] Vertical cross-sectional view of the freezing system 12 after the frozen soil 13 and the planned frozen soil 14 melt. [Figure 5] Diagram showing the freezing method.

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments 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 12, and FIG. 2 is a horizontal cross-sectional view of the freezing system 12. FIG. 1 shows a cross-section taken along arrow B-B shown in FIG. 2, and FIG. 2 shows a cross-section taken along arrow A-A shown in FIG. 1.

[0018] The freezing system 12 includes freezing pipes 3, a heat insulating material 7 as a heat insulating means, a steel sheet pile 10 as a ground expansion restricting member, a connecting member 11, etc. The freezing pipe 3 is, for example, a triple pipe type, an inner pipe 5 is arranged inside an outer pipe 4, a limiting pipe 6 from the upper end of the outer pipe 4 to a middle depth is arranged between the outer pipe 4 and the inner pipe 5, and a heat insulating material 7 is arranged between the limiting pipe 6 and the outer pipe 4. In the range where the freezing pipes 3 are arranged, a recess 2 is formed on the surface of the ground 1. One or more freezing pipes 3 are arranged in the ground 1.

[0019] The heat insulating material 7 is arranged in a freezing suppression range 9 from the surface of the ground 1 to the depth where freezing is to be suppressed. The steel sheet pile 10 is arranged so as to surround at least a part of the length direction of the heat insulating material 7 from the surface of the ground 1 to a predetermined depth. That is, the steel sheet pile 10 may be arranged over the entire length of the freezing suppression range 9, or may be arranged from the surface of the ground 1 to the middle of the depth of the freezing suppression range 9. The steel sheet pile 10 is arranged so as to surround the outside of the planned freezing part 8 in the freezing suppression range 9. The connecting member 11 is, for example, a tie rod, and connects the opposing parts of the steel sheet pile 10 at the upper part of the steel sheet pile 10.

[0020] Next, a method for suppressing ground settlement by the freezing system 12 will be described. To suppress the settlement of the ground 1 using the freezing system 12, first, a recess 2 is formed in the ground 1 as necessary, and the freezing pipes 3 with the heat insulating material 7 arranged on the outer periphery in the freezing suppression range 9 are arranged in the ground 1. Next, the steel sheet pile 10 is arranged from the surface of the ground 1 to a predetermined depth, and the upper part of the steel sheet pile 10 is connected by the connecting member 11 to complete the installation of the freezing system 12. The upper end of the steel sheet pile 10 and the connecting member 11 are arranged in the recess 2 so as not to protrude from the ground surface.

[0021] Figure 3 is a vertical cross-sectional view of the freezing system 12 in operation. Once the installation of the freezing system 12 is complete, the cooling medium 15 is flowed through the freezing pipe 3 to freeze the ground 1, as shown in Figure 3. When the cooling medium 15 is flowed through the freezing pipe 3, the planned frozen soil 14 is formed in the ground 1 around the part of the freezing pipe 3 where the insulation material 7 is not placed. In the part of the freezing pipe 3 where the insulation material 7 is placed, cooling is suppressed by the insulation material 7, and at the same time, the movement of groundwater to the area around the freezing pipe 3 is blocked by the steel sheet piles 10, so a smaller amount of frozen soil 13 is formed than the planned frozen soil 14. Here, when the frozen soil 13 freezes and expands near the surface of the ground 1, a horizontal force is applied to the surrounding ground 1, but because the steel sheet piles 10 restrain the ground 1, the ground 1 outside the steel sheet piles 10 is not consolidated.

[0022] Figure 4 is a vertical cross-sectional view of the freezing system 12 after the frozen soil 13 and planned frozen soil 14 have thawed. After the use of the planned frozen soil 14 is completed, as shown in Figure 4, the circulation of the cooling medium 15 to the freezing pipe 3 is stopped, and the frozen soil 13 and planned frozen soil 14 are allowed to thaw. By using the freezing system 12, the ground 1 outside the steel sheet piles 10 is not consolidated, so ground settlement due to the thawing of the frozen soil 13 is suppressed outside the steel sheet piles 10. Some settlement 16 occurs inside the steel sheet piles 10, so it is backfilled. After that, the freezing pipe 3 is pulled out of the ground 1, replacing it with grout or the like as needed, and the steel sheet piles 10 and connecting members 11 are removed to complete the restoration of the ground 1.

[0023] In this embodiment, by arranging the insulating material 7 around the outer circumference of the freezing pipe 3, the freezing range of the ground 1 can be actively controlled. Furthermore, by arranging the steel sheet piles 10, consolidation of the ground 1 outside the steel sheet piles 10 due to freezing expansion in the shallow layer of the ground 1 can be prevented, thereby suppressing ground settlement. In addition, since the range of settlement 16 in the ground 1 can be limited to the inside of the steel sheet piles 10, the ground 1 can be easily restored after the thawing of the frozen soil 13 and the planned frozen soil 14.

[0024] Furthermore, heating devices such as electric heating wires or heaters may be placed on the steel sheet piles 10 as needed. Activating the heating devices will melt the frozen soil 13 near the steel sheet piles 10, thereby more reliably preventing the consolidation of the ground 1.

[0025] In this embodiment, a triple-pipe system is exemplified as the freezing pipe 3, but the freezing pipe is not limited to this. The freezing pipe may be a double-pipe system, or it may use aluminum microchannels. Furthermore, the insulating means placed on the outer circumference of the freezing pipe may be an air layer or the like, and the ground expansion regulating member is not limited to steel sheet piles 10, but may be any member that can increase the rigidity of the ground 1.

[0026] Furthermore, the shape of the steel sheet piles 10 surrounding the freezing pipe 3 does not have to be rectangular; it may be circular. Also, in cases where frozen soil is formed continuously over a long distance, such as in a frozen wall, arranging the ground expansion regulating member to surround at least a part of the heat insulating means includes arranging it to sandwich at least both sides of the freezing pipe 3.

[0027] 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]

[0028] 1, 101……ground 2………recess 3, 102……Freezing tube 4……Outer tube 5……Inner tube 6……Limited tube 7………Insulation 8... Sections scheduled for freezing 9. Freezing suppression range 10……Steel sheet pile 11… Connecting member 12... Freezing System 13, 103……Frozen soil 14... Planned frozen soil 15……Cooling medium 16, 104……Sinking part 105... Melting section

Claims

1. A freezing pipe is placed underground, through which a cooling medium flows, At a minimum, an insulating means is provided on the outer circumference of the freezing pipe within a predetermined range from the ground surface, A ground expansion restricting member is positioned to surround at least a portion of the thermal insulation means from the ground surface to a predetermined depth, It is equipped with, A freezing system characterized in that a connecting member is provided at least above the ground expansion restricting member for connecting opposing ground expansion restricting members.

2. A freezing pipe is placed underground, through which a cooling medium flows, At a minimum, an insulating means is provided on the outer circumference of the freezing pipe within a predetermined range from the ground surface, A ground expansion restricting member is positioned to surround at least a portion of the thermal insulation means from the ground surface to a predetermined depth, It is equipped with, A freezing system characterized in that a heating device is placed on the ground expansion regulating member.

3. The freezing system according to claim 1 or 2, characterized in that the ground expansion restricting member is arranged outside the portion of the heat insulating means that is to be frozen.

4. A step of placing a freezing pipe in the ground, which has insulating means formed around it at least within a predetermined range from the ground surface, The process involves arranging a ground expansion restricting member at a predetermined depth from the ground surface so as to surround at least a portion of the heat insulating means, The steps include connecting the ground expansion restricting members at least at their upper parts with connecting members that connect opposing ground expansion restricting members, The process involves flowing a cooling medium through the freezing pipe to freeze a predetermined area underground, A step of stopping the circulation of the cooling medium to the freezing pipe and melting the frozen soil, The process of backfilling the settlement area inside the aforementioned ground expansion restricting member, A method for suppressing ground subsidence, characterized by comprising the following:

5. A step of placing a freezing pipe in the ground, which has insulating means formed around it at least within a predetermined range from the ground surface, The process involves arranging a ground expansion restricting member at a predetermined depth from the ground surface so as to surround at least a portion of the heat insulating means, The steps include: placing a heating device on the ground expansion regulating member; The process involves flowing a cooling medium through the freezing pipe to freeze a predetermined area underground, The process involves stopping the circulation of the cooling medium to the freezing pipe and melting the frozen soil with the heating device, The process of backfilling the settlement area inside the aforementioned ground expansion restricting member, A method for suppressing ground subsidence, characterized by comprising the following:

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