Casing for inserting freezing pipe, casing with built-in freezing pipe, and installation method thereof

Abstract

To provide a casing for inserting a freezing pipe, a casing with a built-in freezing pipe, and an installation method thereof, which can create frozen soil including the ground in an area in contact with an underground structure while installing a freezing pipe close to the underground structure without damaging the underground structure in the ground.SOLUTION: A casing 50 for inserting a freezing pipe comprises a first casing 10 having an open tip 11, a first bit 20 provided at the tip 11, a first hollow 15 provided inside, and a base end 13 adapted to be pushed in, and a check valve 30 provided on the tip 11 side of the first hollow 15. A freezing pipe 60 can be freely inserted into the first hollow 15 from the base end 13 side, and the check valve 30 can freely discharge drilling water supplied from the base end 13 side of the first hollow 15 forward in the drilling direction of the first casing 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a casing for inserting a freezing tube, a casing with a built-in freezing tube, and a method for installing the same. [Background technology]

[0002] When excavating between two existing underground structures that are vertically or horizontally related to each other to connect them, protective work is sometimes carried out around the area by ground improvement using methods such as freezing, chemical injection, and high-pressure spraying, and then an unimproved area inside the improved ground area is excavated, and the two existing underground structures are then joined after excavation. Examples of existing underground structures that are installed side by side or above or below in this way include underground tunnels and basements that serve as underground passages, etc., and when excavating from one underground tunnel to the other to connect two adjacent underground tunnels with a connecting tunnel, the various protective works described above are carried out.

[0003] Among the various protective works mentioned above, the freezing method includes, for example, a method of applying a double-pipe freezing pipe and a method of applying a drilled freezing pipe. The method of applying a double-pipe freezing pipe involves first drilling the casing, inserting a double-pipe freezing pipe with an inner pipe and an outer pipe into the casing, supplying cooling liquid (brine) to one of the inner pipe and the outer pipe, and circulating the cooling liquid to the other. On the other hand, the method of applying the drilling-type freezing pipe involves placing an inner pipe inside the drilling casing (outer pipe), supplying a cooling liquid (brine) to the inner pipe, and circulating the cooling liquid between the inner and outer pipes. In either method, a check valve is attached to the inside of the drilling casing, ahead of the drilling direction, to prevent groundwater from flowing into the casing when the casing is drilled, and the resulting inflow of ground along with the inflow of groundwater, which would hinder the insertion of the freezing pipe into the casing or the circulation of the cooling liquid.

[0004] Here, problems with conventional freezing methods will be explained using a method of applying a double-pipe freezing pipe as an example, with reference to Figures 10 to 12. Figures 10 to 12 are all schematic diagrams illustrating conventional freezing methods. 10A and 10B are process diagrams illustrating an example of a conventional freezing method. First, as shown in FIG. 10A, a drilling casing K equipped with a drilling bit B at its tip Ka and a check valve V in its hollow H is rotated and pressed into the ground G in the X1 direction from an underground structure (not shown), and a hole is drilled to a position just before the separation distance t1 from the other existing structure S. The drilling bit B is a steel bit, and since contact of the steel bit B with the underground structure S would damage the existing structure S, the drilling casing K being rotated and pressed into the underground structure S is stopped at a position about several tens of centimeters to 1-2 meters just before the underground structure S.

[0005] As shown in Figure 10A, a check valve V is installed at a position t2 inward from the tip Ka of the drilling casing K, and the check valve V with a length t3 is installed in a manner that protrudes toward the base end side (opposite the tip side) of the drilling casing K. After drilling using the drilling casing K, as shown in Figure 10B, a double-pipe freezing pipe T is inserted into the hollow H of the drilling casing K, and its tip Ta is inserted until it abuts the check valve V. Coolant C is circulated inside the double-pipe freezing pipe T, thereby creating frozen soil I in the ground G around the double-pipe freezing pipe T.

[0006] As is clear from Figure 10B, the insertion position of the drilling casing K is set so that its tip Ka is at a distance t1 from the underground structure S, and a check valve V is installed at a distance t2 inward from the tip Ka of the drilling casing K, and the check valve V of length t3 protrudes toward the base end of the drilling casing K, and the tip Ta of the double-pipe freezing pipe T abuts the end of this check valve V.Therefore, even if coolant C is circulated inside the double-pipe freezing pipe T, the coolant C will only be supplied to a position t1 + t2 + t3 away from the underground structure S, and therefore, as shown in Figure 10B, there is a risk that an area where frozen soil I will not be created will occur near the existing structure S.

[0007] To solve this problem, as shown in Figure 11, if the check valve V is moved to a position in the hollow H of the drilling casing K, closer to the tip Ka of the drilling casing K at a distance t4, the area where frozen soil I is created will expand to a position closer to the existing structure S, but the cooling liquid C will only be supplied to a position at a distance t1 + t4 from the existing structure S, and there is still a risk that an area where frozen soil I is not created will exist near the existing structure S.

[0008] 12, after drilling to a position t1 away from the underground structure S using a drilling casing K with a check valve V installed inside, the drilling casing K is pulled back to the insertion start point of the underground structure (not shown), the check valve V is removed from the drilling casing K, and the drilling casing K is reinserted to a position t1 away from the underground structure S. After that, a double-pipe freezing pipe T is inserted inside the drilling casing K, so that the tip Ta of the double-pipe freezing pipe T is set to a position t1 away from the underground structure S, and cooling liquid C is supplied to the position t1 away. This method makes it possible to create frozen soil I, including the ground in contact with the underground structure S.

[0009] However, this method of drilling the hole with the drilling casing K, then pulling the drilling casing K back to the insertion point of the underground structure, removing the check valve V from the drilling casing K, reinserting the drilling casing K, and then inserting the double-pipe freezing pipe T inside the drilling casing K inevitably lengthens the construction period, and furthermore, is undesirable because there is a risk that groundwater will flow into the drilled hole when the drilling casing K is pulled back, or that the ground will flow into the drilled hole in response to the inflow of groundwater. For these reasons, there is a need for a casing for inserting a freezing pipe, a casing with a built-in freezing pipe, or a method for installing a casing with a built-in freezing pipe that can install a freezing pipe close to an underground structure without damaging the underground structure within the ground, and create frozen soil including the ground in the area adjacent to the underground structure.

[0010] Here, Patent Document 1 proposes a buried object exploration method for exploring buried objects buried underground by boring. This buried object exploration method consists of the following steps: a first step in which a casing rod with a metal bit attached to its tip and an exploration rod that can be inserted into the interior of the casing rod, has a buried object-compatible bit made of a plastic or round bit attached to its tip, and can protrude from the tip surface of the casing rod, and installs the casing rod from the ground in a state where it penetrates to a depth near the buried object but shallower than the buried object; a second step in which the exploration rod is inserted from the base end of the casing rod on the ground, protrudes from the tip surface of the casing rod, and penetrates deeper than this to explore underground buried objects; and a third step in which steps 1 and 2 are repeated a predetermined number of times by changing the planar position. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2020-190104 Summary of the Invention [Problem to be solved by the invention]

[0012] The buried object exploration method described in Patent Document 1 involves inserting a casing rod up to the vicinity of the buried object and detecting whether or not the exploration rod protruding from the tip of the casing rod comes into contact with the buried object. This makes it possible to explore buried objects, but it does not disclose a solution to the above-mentioned problem, namely, a means of installing a freezing pipe up to the vicinity of an underground structure without damaging the underground structure within the ground, and creating frozen soil including the ground in the area adjacent to the underground structure.

[0013] The present invention aims to provide a casing for inserting a freezing pipe, a casing with a built-in freezing pipe, and an installation method thereof, which can install a freezing pipe close to an underground structure without damaging the underground structure within the ground, and create frozen soil including the ground in the area adjacent to the underground structure. [Means for solving the problem]

[0014] In order to achieve the above object, one aspect of the casing for inserting a freezing tube according to the present invention is as follows: a first casing having an open tip, a first bit provided at the tip, a first hollow inside, and adapted to have a base end inserted therein; a check valve provided at a tip end side of the first hollow, A freezing tube can be inserted into the first hollow from the base end side, The check valve is characterized in that it is capable of freely discharging drilling water supplied from the base end side of the first hollow forward in the drilling direction of the first casing.

[0015] According to this aspect, a check valve is provided at the tip side of the first hollow of the first casing, which has a first bit at its tip and a base end that is pushed in, and the check valve is capable of freely discharging drilling water supplied from the base end side of the first hollow forward in the drilling direction of the first casing.This allows freezing pipes to be installed up to the vicinity of the underground structure without damaging the underground structure in the first casing that drills the ground, and allows frozen soil to be created, including the ground in the area adjacent to the underground structure.

[0016] Another aspect of the casing for inserting a freezing tube according to the present invention is as follows: a second casing having a second hollow that contains the first casing; The tip of the second casing is open, a second bit is provided at the tip, and the tip of the first casing inserted into the second hollow can freely extend forward in the drilling direction from the tip of the second casing.

[0017] According to this aspect, by further having a second casing that contains the first casing, after drilling a hole to the vicinity of the underground structure using the second casing, the first casing, which has a check valve at its tip, is protruded through the second hollow of the second casing and drills further, positioning its tip near the underground structure, and installing a freezing pipe as close to the underground structure as possible, the tip of the first casing can be positioned with high precision close to the underground structure while efficiently drilling the ground, and frozen soil can be created, including the ground in the area adjacent to the underground structure.

[0018] Another aspect of the casing for inserting a freezing tube according to the present invention is as follows: The first bit is a resin bit.

[0019] According to this aspect, in a configuration in which only the first casing is provided (no second casing is provided), the first bit provided at the tip of the first casing is a resin bit, so that even if the first bit comes into contact with the underground structure when drilling a hole close to the underground structure with the first bit, damage to the underground structure can be prevented. For example, this is suitable when the distance between two underground structures is relatively short and drilling is possible using a resin bit, which is less durable than a steel bit.

[0020] Another aspect of the casing for inserting a freezing tube according to the present invention is as follows: The first bit is a resin bit, The second bit is a steel bit.

[0021] According to this aspect, in a configuration having a first casing and a second casing surrounding it, of the areas drilled by all the casings, most of the areas are drilled by the second casing, and the last few areas are drilled by the first casing.Since the second bit of the second casing, which drills most of the areas, is a steel bit, wear on the bit can be minimized. Furthermore, since the first bit of the first casing, which drills the final small area, is a plastic bit, damage to the underground structure can be prevented even if the first bit comes into contact with the underground structure when drilling close to the underground structure. In this way, by drilling a long distance with a steel bit and a short distance with a plastic bit, when this type of casing for inserting a freezing pipe is applied, for example, when connecting two underground tunnels with a connecting road, even if the distance between the two underground tunnels is long, it is possible to achieve both efficient drilling with reduced wear on the bit and prevention of damage to the underground tunnel on the arrival side by the bit, which is preferable.

[0022] In another aspect of the casing for inserting a freezing pipe according to the present invention, The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, The drilling water supplied to the first hollow can be freely discharged forward in the drilling direction through the first water passage hole and the second water passage hole.

[0023] According to this aspect, the check valve has a base and a resin gasket, the base is plate-shaped and has a fixed portion with a first water passage hole and a convex portion protruding forward in the hole-drilling direction, and the resin gasket is attached to the fixed portion from the forward side in the hole-drilling direction and has a second water passage hole at a position corresponding to the convex portion, the second water passage hole having dimensions smaller than the planar dimensions of the convex portion.Since the check valve is flat overall and the convex portion protrudes forward in the hole-drilling direction, the freezing pipe can be inserted up to the tip of the first casing. Furthermore, a first water passage hole is provided around the convex portion of the fixed portion, and a second water passage hole having dimensions smaller than the planar dimensions of the convex portion of the resin gasket is fitted into the convex portion from the front in the drilling direction and attached to the fixed portion, making it possible to discharge drilling water forward in the drilling direction through the first water passage hole and the second water passage hole, and the inflow of groundwater from the drilling direction can be prevented by the convex portion and the resin gasket.

[0024] In another aspect of the casing for inserting a freezing pipe according to the present invention, The first bit has a third water passage hole, The check valve is attached inside the first bit, The drilling water supplied to the first hollow can be freely discharged forward in the drilling direction through the first water passage hole, the second water passage hole, and the third water passage hole.

[0025] According to this aspect, by attaching a check valve to the back surface (first hollow side) of the first bit, when the first bit is attached to the front of the first hollow of the first casing in the drilling direction, the check valve is also attached at the same time, allowing the casing for inserting the freezing pipe to be manufactured efficiently. Furthermore, because the check valve is attached to the back surface of the first bit, the check valve is attached in a position close to the tip of the first casing, allowing the freezing pipe to be inserted up to the tip side of the first casing.

[0026] Furthermore, one aspect of the freezing pipe built-in casing according to the present invention is as follows: The freezing tube insertion casing; a freezing tube inserted into the first hollow; The freezing pipe has a tip that abuts against the check valve or is located in the vicinity of the check valve.

[0027] According to this aspect, the freezing pipe abuts against the check valve attached to the front of the first hollow of the casing for inserting the freezing pipe of the present invention in the drilling direction, or is inserted up to the vicinity of the check valve, so that the freezing pipe can be installed up to the vicinity of the underground structure without damaging the underground structure with the first casing that drills the ground, and frozen soil can be created including the ground in the area adjacent to the underground structure.

[0028] Furthermore, one aspect of the method for installing a casing with a built-in freezing pipe according to the present invention is to a step A of installing a mouth pipe at an insertion starting point where a first casing, which has an open tip, a first bit at the tip, a first hollow inside, and a check valve at the tip side of the first hollow, is inserted into the ground, pushing in the base end of the first casing inserted into the mouth pipe, and drilling the ground with the first bit while supplying drilling water into the first hollow, thereby inserting a part of the first casing into the ground and waterproofing and sealing the gap between the mouth pipe and the first casing; and a step B of inserting a freezing tube into the first hollow, The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, In the step A, the drilling water supplied to the first hollow is discharged forward in the drilling direction through the first water passage hole and the second water passage hole, In the step B, the tip of the freezing pipe is brought into contact with the check valve or positioned in the vicinity of the check valve.

[0029] According to this aspect, a casing for inserting a freezing pipe, which has only a first casing (and does not have a second casing), is inserted into the inside of the mouth pipe and inserted into the ground while drilling the ground, and a freezing pipe is inserted into the first hollow of the first casing so that the tip of the freezing pipe abuts against the check valve or is positioned near the check valve.This allows the freezing pipe to be installed up to the vicinity of the underground structure without damaging the underground structure with the first casing that drills the ground, and frozen soil can be created, including the ground in the area adjacent to the underground structure.

[0030] Another aspect of the method for installing a casing with a built-in freezing pipe according to the present invention is as follows: a step C of installing a mouth pipe at an insertion starting point where a second casing having an open tip, a second bit at the tip, and a second hollow inside is inserted into the ground, pushing in the base end of the second casing inserted into the mouth pipe, and drilling the ground with the second bit while supplying drilling water to the second hollow, thereby inserting a part of the second casing into the ground and waterproofing the gap between the mouth pipe and the second casing; a step D of inserting a first casing, the first casing having an open tip, a first bit at the tip, a first hollow inside, and a check valve at the tip side of the first hollow, into the second casing and pushing in the base end of the first casing, causing the tip of the first casing to protrude forward in the drilling direction from the tip of the second casing, and drilling water is supplied to the first hollow while drilling the ground with the first bit, thereby inserting a part of the first casing into the ground and waterproofing the gap between the second casing and the first casing; and an E step of inserting a freezing tube into the first hollow, The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, In the step D, the drilling water supplied to the first hollow is discharged forward in the drilling direction through the first water passage hole and the second water passage hole, In the step E, the tip of the freezing pipe is brought into contact with the check valve or positioned in the vicinity of the check valve.

[0031] According to this embodiment, the second casing is inserted into the inside of the mouth pipe and inserted into the ground while drilling a hole in the ground, the first casing is protruded from the tip of the second casing and further drilling is performed, and a freezing pipe is inserted into the first hollow and the tip of the freezing pipe is abutted against the check valve or positioned near the check valve, thereby drilling the hole as close as possible to the underground structure with the second casing, and then the freezing pipe can be installed near the underground structure with the first casing without damaging the underground structure, and frozen soil can be created including the ground in the area adjacent to the underground structure. [Effects of the Invention]

[0032] According to the casing for inserting a freezing pipe, the casing with a built-in freezing pipe, and the installation method thereof of the present invention, it is possible to install a freezing pipe close to an underground structure without damaging the underground structure within the ground, and to create frozen soil including the ground in the area adjacent to the underground structure. [Brief explanation of the drawings]

[0033] [Figure 1] This figure shows a state in which frozen soil is created in the ground between two underground structures using an example of a casing with a built-in freezing pipe according to an embodiment, which is equipped with an example of a casing for inserting a freezing pipe according to an embodiment. [Figure 2A] 10 is a longitudinal cross-sectional view taken along the axial direction of a first casing, showing a state before the check valve is assembled, in a mode in which the check valve is attached to the back surface of the first bit. FIG. [Figure 2B] 10 is a longitudinal cross-sectional view taken along the axial direction of a first casing, showing a check valve attached to the back surface of a first bit, with the check valve assembled. FIG. [Figure 2C]2C is a view taken along the arrow CC in FIG. 2B, and is a vertical cross-sectional view taken at a midpoint of the base of the check valve. [Figure 2D] 2C is a view taken along the arrow DD in FIG. 2B, and is a front view of the first bit. [Figure 2E] FIG. 2 is a perspective view of the first bit as seen obliquely from the front. [Figure 2F] FIG. 10 is a vertical cross-sectional view illustrating the state in which drilling water supplied to the first hollow of the first casing is discharged forward in the drilling direction through the check valve and the first bit. [Figure 3A] 10 is a longitudinal cross-sectional view taken along the axial direction of a first casing, showing a state before the check valve is assembled, in a mode in which the check valve is attached to the wall surface of a first hollow. FIG. [Figure 3B] This is a longitudinal cross-sectional view taken along the axial direction of the first casing, showing the check valve assembled in a form in which a check valve is attached to the wall surface of the first hollow, and also shows the state in which drilling water supplied to the first hollow of the first casing is discharged forward in the drilling direction through the check valve. [Figure 3C] 10A and 10B are front views showing components in a configuration in which a check valve is attached to the wall surface of the first hollow, where (a) is a front view of the base, (b) is a front view of the resin gasket, and (c) is a front view of the retaining ring. [Figure 4A] FIG. 10 is a diagram illustrating preliminary drilling using the second casing. [Figure 4B] This is a diagram illustrating the backward drilling using the first casing, with the first casing protruding from the opening at the tip of the second casing. [Figure 4C] FIG. 10 is a diagram illustrating the circulation of coolant in a freezing pipe inserted into the first hollow of the first casing. [Figure 5A] 1 is a process diagram of an example of a method for installing a casing with a built-in freezing pipe according to an embodiment. [Figure 5B] 5B is a process diagram of an example of a method for installing a casing with a built-in freezing pipe according to an embodiment, following FIG. 5A. [Figure 6A]5B, and FIG. 5C is a process diagram of an example of a method for installing a casing with a built-in freezing pipe according to an embodiment. [Figure 6B] 6B is a process diagram of an example of a method for installing a casing with a built-in freezing pipe according to an embodiment, following FIG. 6A. [Figure 7] 6B, followed by a process diagram of an example of a method for installing a casing with a built-in freezing pipe according to an embodiment. [Figure 8] This is a diagram explaining the state in which coolant is circulated through the freezing pipes of the installed freezing pipe-integrated casing, creating frozen soil in the surrounding ground. [Figure 9] 10 is a diagram illustrating the state in which a freezing pipe is pulled out of a casing for inserting a freezing pipe, and a filler material is filled into the hole while the casing for inserting a freezing pipe is pulled out of the frozen soil. FIG. [Figure 10A] FIG. 1 is a process diagram illustrating an example of a conventional freezing method. [Figure 10B] 10A, followed by a process diagram illustrating an example of a conventional freezing method. [Figure 11] FIG. 10 is a diagram illustrating another example of a conventional freezing method. [Figure 12] FIG. 10 is a diagram illustrating yet another example of a conventional freezing method. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, a casing for inserting a freezing tube, a casing with a built-in freezing tube, and an installation method thereof according to embodiments will be described with reference to the accompanying drawings. Note that in this specification and the drawings, substantially identical components will be designated by the same reference numerals, and redundant explanations may be omitted.

[0035] [Casing for inserting a freezing pipe according to an embodiment, a casing with a built-in freezing pipe, and an installation method thereof] An example of a casing for inserting a freezing pipe according to an embodiment, a casing with a built-in freezing pipe, and an installation method thereof will be described with reference to Figures 1 to 9. Here, Figure 1 is a diagram showing a state in which frozen soil is created in the ground between two underground structures by an example of a casing with a built-in freezing pipe according to an embodiment, which is equipped with an example of a casing for inserting a freezing pipe according to an embodiment.

[0036] In the following explanation, we will explain an example in which a freezing method is applied as a protective work when constructing a connecting road connecting two underground tunnels (an example of an underground structure), and a casing for inserting a freezing pipe is drilled and inserted into the ground from one of the underground tunnels, but the casing for inserting a freezing pipe and a casing with a built-in freezing pipe of the present invention can also be applied to freezing methods that involve drilling a hole in the ground from above ground, and can be applied to various types of freezing methods. Furthermore, the casing for inserting a freezing pipe and the casing with a built-in freezing pipe in the illustrated example are configured to include a first casing and a second casing that contains the first casing, but they may also be configured to include only the first casing.

[0037] Furthermore, although the casing for inserting a freezing pipe of the present invention is a casing that is applied to the freezing method, it may also be used for other purposes, for example, by installing a magnetic exploration sensor or the like at the tip of the first casing and applying it to the exploration of buried pipes, etc. buried in the ground.

[0038] As shown in Figure 1, when creating frozen soil I in the area of ​​the ground G between the first underground tunnel S1 and the second underground tunnel S2, which are composed of segment rings, where a connecting road will be constructed, the second casing 40 inserted into the ground G from the first underground tunnel S1 is pre-drilled and inserted up to the vicinity of the second underground tunnel S2, and the first casing 10 is inserted into the second hollow 45 of the second casing 40, and the tip 11 of the first casing 10 protrudes forward in the excavation direction from the tip opening 42 at the tip 41 of the second casing 40.

[0039] A second bit 47 (see FIG. 4A), which is a steel bit, is attached to the tip 41 of the second casing 40 that drills most of the distance between the first underground tunnel S1 and the second underground tunnel S2.

[0040] A first bit 20, which is a resin bit, is attached to the tip opening 12 of the first casing 10, and a check valve 30 is attached to the back surface of the first bit 20 (rear in the drilling direction).

[0041] A casing 50 for inserting a freezing pipe is formed by a first casing 10 having a first bit 20 at its tip and a check valve 30 on the back of the first bit 20, and a second casing 40 containing the first casing 10.

[0042] A mouth pipe 80 is attached to the insertion starting point Sa of the first underground tunnel S1 where the second casing 40 is inserted, and the second casing 40 is rotated and pressed into the ground G via the mouth pipe 80.

[0043] After the tip 41 of the second casing 40 is installed near the second underground tunnel S2 (for example, at a position about 50 cm to 1.2 m), the first casing 10 is inserted into the second hollow 45 of the second casing 40 inside the first underground tunnel S1. The first bit 20 attached to the tip 41 of the first casing protrudes from the tip opening 42 of the second casing 40, drills a small amount of ground out of the remaining ground G up to the second underground tunnel S2, and is installed in a position as close as possible to the second underground tunnel S2.

[0044] Here, since the first bit 20 attached to the tip 11 of the first casing 10 is a resin bit, even if the first bit 20 comes into contact with the second underground tunnel S2, there is no risk that the first bit 20 will damage the second underground tunnel S2.

[0045] As shown, the nozzle pipe 80 and the second casing 40 are provided with injection valves 82A and 82B, respectively, and the nozzle pipe 80, the second casing 40, and the first casing 10 are further provided with joining flanges 84A, 84B, and 84C, respectively, the functions of which will be explained below.

[0046] After the casing 50 for inserting the freezing pipe is installed in the ground G, the freezing pipe 60 is inserted into the first hollow 15 of the first casing 10 from inside the first underground tunnel S1, and the tip of the freezing pipe 60 is installed in a position abutting against the back of the check valve 30, thereby forming a casing 70 with a built-in freezing pipe.

[0047] Water W1 and W2 are respectively contained in the gap Ga2 between the second casing 40 and the first casing 10 and the gap Ga3 between the first casing 10 and the freezing pipe 60. The water W1 and W2 have the effect of efficiently transferring the cold generated when the coolant circulates inside the freezing pipe 60 inserted in the first hollow 15 to the surrounding ground G.

[0048] The freezing pipe 60 in the illustrated example is a double pipe equipped with an outer pipe 60A and an inner pipe 60B, and inside the first underground tunnel S1, a cooling liquid is supplied to the inner pipe 60B in the Y1 direction, the cooling liquid flows into the inner pipe 60B in the Y2 direction, flows through the tip opening 60Ba of the inner pipe 60B between the outer pipe 60A and the inner pipe 60B in the Y3 direction, then flows toward the first underground tunnel S1 in the Y4 direction and flows out in the Y5 direction, and the cooling liquid repeats this circulation, creating frozen soil I in the ground G around the freezing pipe built-in casing 70. Although not shown, various equipment such as a brine cooler, compressor, and brine circulation pump are installed inside the first underground tunnel S1.

[0049] By using the casing 70 with built-in freezing pipes, the check valve 30 is attached as close as possible to the tip 11 of the first casing 10, so the tip of the freezing pipe 60 can be positioned as close as possible to the second underground tunnel S2. This makes it possible to create frozen soil I, including the ground in the area adjacent to the first underground tunnel S2, while the check valve 30 prevents groundwater and ground from flowing into the casing when drilling the casing with the casing 50 for inserting freezing pipes.

[0050] Next, with reference to FIGS. 2A to 2F, an example of the first bit 20, which is a resin bit, and the check valve 30 attached to the back surface thereof will be described in detail.

[0051] Fig. 2A is a longitudinal cross-sectional view of the first casing in the axial direction, showing the check valve attached to the back of the first bit before assembly, Fig. 2B is a longitudinal cross-sectional view of the first casing in the axial direction, showing the check valve attached to the back of the first bit after assembly, Fig. 2C is a longitudinal cross-sectional view taken along the CC arrow in Fig. 2B, showing the check valve attached to the back of the first bit after assembly, Fig. 2D is a longitudinal cross-sectional view taken along the DD arrow in Fig. 2B, showing the front view of the first bit, Fig. 2E is a perspective view of the first bit from diagonally forward, and Fig. 2F is a longitudinal cross-sectional view illustrating the state in which drilling water supplied to the first hollow of the first casing is discharged forward in the drilling direction through the check valve and the first bit.

[0052] As shown in FIG. 2A, the attachment portion 22 of the first bit 20 is fitted into the tip opening 12 at the tip 11 of the first casing 10.

[0053] 2D and 2E, the first bit 20 has a plurality of bits 21 (four in the illustrated example) around a central third water passage hole 23, and as shown in Fig. 2E, has an attachment portion 22 continuous with each bit 21. Furthermore, as shown in Fig. 2A, a rear recess 24 is provided on the inside of the attachment portion 22.

[0054] As shown in FIG. 2A, the check valve 30 has a base 31 and a resin packing 35, both of which are fitted into the rear recess 24, and is attached to the first bit 20 via a fastener 38.

[0055] The base 31 has a plate-shaped fixed portion 32 and a convex portion 33 that protrudes forward in the drilling direction, and as shown in Figure 2C, multiple (six in the illustrated example) first water passage holes 34 are provided around the convex portion 33 on the fixed portion 32.

[0056] The resin gasket 35 is attached to the fixed portion 32 of the base 31 from the front side in the drilling direction, and has a second water passage hole 37 at a position corresponding to the convex portion 33, the second water passage hole 37 having dimensions smaller than the planar dimensions of the convex portion 33.As shown in Figure 2B, when the fixed portion 32 and the resin gasket 35 are brought into contact with each other while the convex portion 33 is inserted into the second water passage hole 37, a check valve 30 is formed in a position where the periphery of the second water passage hole 37 in the resin gasket 35 is in contact with the side of the convex portion 33.

[0057] As shown in Figure 2F, when drilling using the first casing 10, drilling water is supplied to the first hollow 15 of the first casing 10, and the supplied drilling water passes through the first water passage 34 of the base 31, through the second water passage 37 which is opened when the resin gasket 35 in contact with the convex portion 33 is pushed sideways, and then through the third water passage 23 of the first bit 20, and is discharged forward in the drilling direction Z13.

[0058] As shown in the illustrated example, a check valve 30 is attached to the rear recess 24 of the first bit 20, so that when the first bit 20 is attached to the tip opening 12 of the first hollow 15 of the first casing 10, the check valve 30 is also attached at the same time, allowing the casing 50 for inserting a freezing pipe to be manufactured efficiently.

[0059] Furthermore, a check valve 30 is attached to the rear recess 24 of the first bit 20 attached to the tip opening 12 of the first casing 10, and since the check valve 30 is flat overall and the convex portion 33 protrudes forward in the drilling direction, the freezing pipe 60 can be inserted up to the tip side of the first casing 10, making it possible to create frozen soil I including the ground in the area adjacent to the first underground tunnel S2.

[0060] Next, with reference to FIG. 3, a check valve 30A that is attached to the wall surface of the hollow 15 of the first casing 10 in place of the check valve 30 shown in FIG. 2 will be described.

[0061] Here, Figure 3A is a longitudinal cross-sectional view taken along the axial direction of the first casing, showing the check valve in a state before assembly, in a form in which a check valve is attached to the wall surface of the first hollow; Figure 3B is a longitudinal cross-sectional view taken along the axial direction of the first casing, showing the check valve in an assembled state, in a form in which a check valve is attached to the wall surface of the first hollow, and also shows the state in which drilling water supplied to the first hollow of the first casing is discharged forward in the drilling direction through the check valve; Figure 3C is a front view showing the components in a form in which a check valve is attached to the wall surface of the first hollow, where (a) is a front view of the base, (b) is a front view of the resin gasket, and (c) is a front view of the retaining ring.

[0062] The check valve 30A shown in the figure has a base 31A, a resin packing 35A, and a retaining ring 39, and the end face of the base 31A is attached to the wall surface of the first casing 10 at the front in the drilling direction.

[0063] The base 31A has a plate-shaped fixed portion 32A and a convex portion 33A that protrudes forward in the drilling direction, and as shown in (a) of Figure 3C, multiple (six in the illustrated example) first water passage holes 34A are provided around the convex portion 33A in the fixed portion 32A.

[0064] The resin packing 35A is attached to the fixed portion 32A of the base 31A from the front side in the drilling direction, and as shown in Fig. 3C (b), has a second water passage hole 37A at a position corresponding to the convex portion 33A, the second water passage hole 37A being smaller than the planar dimension of the convex portion 33A. As shown in Fig. 3A, the fixed portion 32A and the resin packing 35A are brought into contact with each other while the convex portion 33A is inserted into the second water passage hole 37A. As shown in Fig. 3C (c), a retaining ring 39 having a central opening 39A is brought into contact with the resin packing 35A, and fasteners 38 are inserted into pin holes 34a, 34b, and 34c provided in corresponding positions on the fixed portion 31A, the resin packing 35A, and the retaining ring 39, respectively. This forms the check valve 30A with the periphery of the second water passage hole 37A in the resin packing 35A in contact with the side surface of the convex portion 33A.

[0065] As shown in Figure 3B, when drilling using the first casing 10, drilling water is supplied to the first hollow 15 of the first casing 10, and the supplied drilling water is discharged in the Z14 direction forward in the drilling direction through the first water passage 34A of the base 31A and the second water passage 37A, which is opened when the resin gasket 35A in contact with the convex portion 33A is pushed sideways.

[0066] As shown in FIG. 3B, in a configuration in which a check valve 30A is attached to the wall surface of the first hollow 15 of the first casing 10, a drill bit 20A is attached to the tip 11 (tip surface) of the first casing 10.

[0067] Like the check valve 30, the check valve 30A in the illustrated example is flat overall with a convex portion 33A protruding forward in the drilling direction, and is attached to the wall surface of the first hollow 15 of the first casing 10 on the forward side in the drilling direction, so that the freezing pipe 60 can be inserted up to the tip of the first casing 10, making it possible to create frozen soil I including the ground in the area adjacent to the first underground tunnel S2.

[0068] Next, referring to FIG. 4, an outline of forming the casing 50 for inserting the freezing pipe in the ground G, then forming the casing 70 with the built-in freezing pipe therein, and then creating frozen soil will be described.

[0069] Here, Figure 4A is a diagram explaining preliminary drilling using the second casing, Figure 4B is a diagram explaining subsequent drilling using the first casing with the first casing protruding from the opening at the tip of the second casing, and Figure 4C is a diagram explaining the circulation of coolant in the freezing pipe after inserting and installing a freezing pipe into the first hollow of the first casing.

[0070] As shown in Figure 4A, the second casing 40 is rotationally pressed into the ground G in the X1 direction from the first underground tunnel S1 (see Figure 1), and is equipped with a steel bit 47 at its tip 41. While discharging drilling water forward in the drilling direction from the second hollow 45, the steel bit 47 drills the ground G to a position that is a distance t10 away from the second underground tunnel S2. Here, the distance t10 can be set within a range of, for example, 50 cm to 1.2 m.

[0071] 4B, a first bit 20 is attached to the tip opening 12 of the second casing 40, and a check valve 30 is attached to the back of the first bit 20. The second casing 40 is then inserted into the second hollow 45, and the first bit 20, which is a plastic bit, is extended from the tip opening 42 of the second casing 40 in the direction X2, which is the forward direction of drilling. While discharging drilling water forward from the first hollow 15 of the first casing 10, the first bit 20 is used to drill further into the ground G, until the hole is drilled to a distance t11 from the second underground tunnel S2, forming a casing 50 for inserting a freezing pipe. Here, the distance t11 can be set within a range of, for example, several centimeters to 50 centimeters.

[0072] 4C, the freezing pipe 60 is inserted into the first hollow 15 in the X3 direction, and the tip of the freezing pipe 60 is brought into contact with the check valve 30 to form the casing 70 with a built-in freezing pipe. Next, a coolant is supplied to the inner pipe 60B that constitutes the freezing pipe 60 in the Y2 direction, and the coolant is circulated by flowing from the inner pipe 60B between the outer pipe 60A and the inner pipe 60B in the Y3 direction, thereby creating frozen soil from the first underground tunnel S1 to the second underground tunnel S2.

[0073] Next, an example of a method for installing the freezing pipe-incorporating casing according to the embodiment will be described with reference to FIGS.

[0074] 5A, 5B, 6A, 6B, and 7 are process diagrams showing an example of a method for installing a casing with a built-in freezing pipe according to an embodiment. Fig. 8 is a diagram showing the process of circulating a coolant through the freezing pipe of the installed casing to create frozen soil in the surrounding ground, following the installation method for the casing with a built-in freezing pipe. Fig. 9 is a diagram showing the process of pulling out the freezing pipe from the casing for inserting the freezing pipe, and filling the hole with a filler while pulling out the casing from the frozen soil.

[0075] First, as shown in Figure 5A, a mouth pipe 80 is installed at the insertion start point Sa of the first underground tunnel S1, where the second casing 40, which has a second bit 47 at its tip 41 and a second hollow 45 inside, is inserted into the ground G.

[0076] The nozzle pipe 80 is fitted with an injection valve 82A, a drain valve 83A and a connecting flange 84A, and the connecting flange 86A provided on the main valve 85A is bolted to the connecting flange 84A, and a pre-bender 88 is attached to a separate connecting flange 87A provided on the main valve 85A.

[0077] A second casing 40 is inserted through the prepender 88, the main valve 85A, and the mouth pipe 80, a supply pipe 90 is installed in fluid communication with the base end 43 of the second casing 40, a hydraulic drill 91 is installed midway along the supply pipe 90, and a water swivel 89 is installed at the rear end of the supply pipe 90.

[0078] Drilling water is supplied to the water swivel 89 in the Z1 direction, circulated through the supply pipe 90 in the Z2 direction, and circulated from the supply pipe 90 to the second hollow 45 of the second casing 40 in the Z3 direction. In conjunction with this supply of drilling water, the hydraulic drill 91 is operated to rotate and press the second casing 40 into the ground G. The drilling water circulating through the second hollow 45 circulates through the tip opening 42 into the ground G in the Z4 direction, flows through the water supply on the outer periphery of the second casing 40 to the first underground tunnel S1 side in the Z5 direction, and is drained through the gap Ga1 between the mouth pipe 80 and the second casing 40 and via the drain valve 83A in the Z6 direction.

[0079] After drilling the second casing 40 to the vicinity of the second underground tunnel S2 (distance t10) while rotating and pressing it into the ground G, as shown in Figure 5B, the components behind the connecting flange 84A (prepender 88, main valve 85A, supply pipe 90, hydraulic drill 91, water swivel 89, etc.) are removed, the second casing 40 is cut at a position behind the connecting flange 84A, and the injection valve 82B, drain valve 83B, and connecting flange 84B are attached to the second casing 40.

[0080] Furthermore, filler J1 such as cement milk is filled in the Z7 direction into the gap Ga1 between the mouth pipe 80 and the second casing 40 via the injection valve 82A, thereby sealing the gap Ga1 between the mouth pipe 80 and the second casing 40 waterproofly (this is the end of process C).

[0081] Next, as shown in FIG. 6A, a connecting flange 86B provided on the main valve 85B is bolted to the connecting flange 84B at the rear end of the cut second casing 40, and a pre-bender 88 is attached to a separate connecting flange 87B provided on the main valve 85B.

[0082] The first casing 10 is inserted through the prepender 88, the main valve 85B, and the second casing 40, and a supply pipe 90 is installed in fluid communication with the base end 13 of the first casing 10. A hydraulic drill 91 is installed midway along the supply pipe 90, and a water swivel 89 is installed at the rear end of the supply pipe 90.

[0083] Drilling water is supplied to the water swivel 89 in the Z10 direction, circulated through the supply pipe 90 in the Z11 direction, and circulated from the supply pipe 90 to the first hollow 15 of the first casing 10 in the Z12 direction. In conjunction with this supply of drilling water, the hydraulic drill 91 is operated to rotate and press the first casing 10 into the ground G. The drilling water circulating through the first hollow 15 circulates through the check valve 30 and the first bit 20 into the ground G in the Z13 direction, flows through the gap Ga2 between the first casing 10 and the second casing 40 to the first underground tunnel S1 in the Z14 direction, and is drained through the gap Ga2 between the second casing 40 and the first casing 10 and via the drain valve 83B in the Z15 direction.

[0084] The first casing 10 is rotated and pressed into the ground G while drilling to a position closer to the second underground tunnel S2 (separation t11), and then, as shown in Figure 6B, the components behind the connecting flange 84B are removed, the first casing 10 is cut at a position behind the connecting flange 84B, and the injection valve 82C and the connecting flange 84C are attached to the first casing 10.

[0085] Furthermore, a filler J2 such as cement milk is filled in the Z16 direction into the gap Ga2 between the second casing 40 and the first casing 10 via the injection valve 82B, and the gap Ga2 between the second casing 40 and the first casing 10 is sealed waterproofly to form a casing 50 for inserting a freezing pipe (this is the end of process D).

[0086] 7, a prepender 88 is attached to the joint flange 84C, the freezing pipe 60 is inserted into the first hollow 15 of the first casing 10 via the prepender 88, and the tip of the freezing pipe 60 is brought into contact with the check valve 30. After that, a filler J3 such as cement milk is filled into the gap Ga3 between the first casing 10 and the freezing pipe 60 via the injection valve 82C, and the gap Ga3 is waterproofly sealed, thereby forming the casing 70 with a built-in freezing pipe and completing the installation of the casing 70 with the built-in freezing pipe. At this stage, water W1 and W2 are contained in the gaps Ga2 and Ga3 (this is step E).

[0087] According to the installation method of the casing with a built-in freezing pipe shown in the figure, the second casing 40 is inserted into the inside of the mouth pipe 80 and inserted into the ground G while drilling the ground G, the first casing 10 is protruded from the tip of the second casing 40 and further drilling is performed, the freezing pipe 60 is inserted into the first hollow 15 and the tip of the freezing pipe 60 is abutted against the check valve 30, thereby drilling the hole as close as possible to the second underground tunnel S2 with the second casing 40, and the freezing pipe 60 can be installed as close to the second underground tunnel S2 as possible with the first casing 10 without damaging the second underground tunnel S2, making it possible to create frozen soil I including the ground in the area adjacent to the second underground tunnel S2.

[0088] Here, although not shown in the figures, if the casing for inserting the freezing pipe does not have a second casing and only has a first casing, the first casing 10 is inserted into the inside of the mouth pipe 80 and its base end 13 is pushed in, and while supplying drilling water to the first hollow 15, the ground G is drilled with the first bit 20 to insert a part of the first casing 10 into the ground G, and then step A is carried out to waterproof and seal the gap between the mouth pipe 80 and the first casing 10, and then step B is carried out to insert the freezing pipe 60 into the first hollow 15, resulting in a method of installing a casing with a built-in freezing pipe.

[0089] Next, as shown in Figure 8, the coolant is supplied to the inner pipe 60B that constitutes the freezing pipe 60 in the Z20 direction, circulated through the inner pipe 60B in the Z21 direction, circulated from the inner pipe 60B between the outer pipe 60A and the inner pipe 60B in the Z22 direction, circulated further toward the first underground tunnel in the Z23 direction, and drained in the Z24 direction, thereby circulating the coolant.By repeatedly circulating this coolant, frozen soil I is created from the first underground tunnel S1 to the second underground tunnel S2.

[0090] After creating frozen soil I from the first underground tunnel S1 to the second underground tunnel S2, as shown in Figure 9, a supply pipe 90 is connected to the first casing 10, and filler material M is supplied in the Z30 direction through the supply pipe 90.While circulating filler material M through the first hollow 15, the casing 50 for inserting the freezing pipe is pulled out in the Z35 direction toward the first underground tunnel S1, and filler material M is supplied in the Z32 direction into the cavity created by this pulling out to fill the hole, thereby completing the creation of frozen soil I and the removal of the casing 70 with the built-in freezing pipe (and the casing 50 for inserting the freezing pipe).

[0091] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0092] 10: First casing 11: Tip 12: Tip opening 13: Proximal end 15: 1st hollow 20, 20A: 1st bit (resin bit) 21: Bit 22: Mounting part 23: Third water hole 24: Rear recess 30, 30A: Check valve 31, 31A: Bass 32: Fixed part 33, 33A: Convex part 34, 34A: First water hole 35, 35A: Resin packing 37,37A: 2nd water hole 38: Fastener 39: Retaining ring 40: Second casing 41: Tip 42: Tip opening 43: Proximal end 45: 2nd hollow 47: 2nd bit (steel bit) 50: Casing for inserting freezing pipe 60:Freezing tube 60A:Outer tube 60B: Inner tube 70: Casing with built-in freezing pipe 80: Mouth tube 82A, 82B, 82C: Injection valve 83A, 83B: Drain valve 84A, 84B, 84C: Joint flange 85A, 85B: Main valve 86A, 87A: Joint flange 88: Prepender 89: Water swivel 90: Supply pipe 91: Hydraulic drill G: Ground I: Frozen soil S1: First underground structure (underground tunnel) S2: Second underground structure (underground tunnel) Sa: insertion origin W1, W2: Water Ga1, Ga2, Ga3: gap J1, J2, J3: Filler M: Filling material

Claims

1. a first casing having an open tip, a first bit provided at the tip, a first hollow inside, and a base end configured to be pushed into; a check valve provided at a tip end side of the first hollow, A freezing tube is freely inserted into the first hollow from the base end side, A casing for inserting a freezing pipe, characterized in that the check valve is capable of freely discharging drilling water supplied from the base end side of the first hollow toward the front of the first casing in the drilling direction.

2. a second casing having a second hollow that contains the first casing; A casing for inserting a freezing tube as described in claim 1, characterized in that the tip of the second casing is open, a second bit is provided at the tip, and the tip of the first casing inserted into the second hollow can freely extend forward from the tip of the second casing in the drilling direction.

3. 2. The casing for inserting a freezing pipe according to claim 1, wherein the first bit is made of resin.

4. The first bit is a resin bit, 3. The casing for inserting a freezing pipe according to claim 2, wherein the second bit is a steel bit.

5. The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, A casing for inserting a freezing pipe as described in claim 1, characterized in that the drilling water supplied to the first hollow can be freely discharged forward in the drilling direction through the first water passage hole and the second water passage hole.

6. the first bit has a third water passage hole; The check valve is attached inside the first bit, A casing for inserting a freezing pipe as described in claim 5, characterized in that the drilling water supplied to the first hollow can be freely discharged forward in the drilling direction through the first water passage hole, the second water passage hole, and the third water passage hole.

7. A casing for inserting a freezing tube according to any one of claims 1 to 6; a freezing tube inserted into the first hollow; A casing with a built-in freezing pipe, characterized in that the tip of the freezing pipe abuts against the check valve or is located in the vicinity of the check valve.

8. a step A of installing a mouth pipe at an insertion starting point where a first casing, which has an open tip, a first bit at the tip, a first hollow inside, and a check valve at the tip side of the first hollow, is inserted into the ground, pushing in the base end of the first casing inserted into the mouth pipe, and drilling the ground with the first bit while supplying drilling water into the first hollow, thereby inserting a part of the first casing into the ground and waterproofing the gap between the mouth pipe and the first casing; and a step B of inserting a freezing tube into the first hollow, The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, In the step A, the drilling water supplied to the first hollow is discharged forward in the drilling direction through the first water passage hole and the second water passage hole, The method for installing a casing with a built-in freezing pipe is characterized in that in the step B, the tip of the freezing pipe is brought into contact with the check valve or is positioned in the vicinity of the check valve.

9. a step C of installing a mouth pipe at an insertion starting point where a second casing having an open tip, a second bit at the tip, and a second hollow inside is inserted into the ground, pushing in the base end of the second casing inserted into the mouth pipe, and drilling the ground with the second bit while supplying drilling water to the second hollow, thereby inserting a part of the second casing into the ground and waterproofing the gap between the mouth pipe and the second casing; a D step in which a first casing having an open tip, a first bit provided at the tip, a first hollow inside, and a check valve provided at the tip side of the first hollow is inserted into the second casing, the base end of the first casing is pushed in, the tip of the first casing protrudes forward in the drilling direction from the tip of the second casing, and drilling water is supplied to the first hollow while drilling the ground with the first bit, thereby inserting a part of the first casing into the ground and waterproofing the gap between the second casing and the first casing; and an E step of inserting a freezing tube into the first hollow, The check valve has a base and a resin packing, The base includes a plate-shaped fixing portion and a protruding portion protruding forward in the drilling direction, and a first water passage hole is provided around the protruding portion of the fixing portion; The resin packing is attached to the fixing portion from the front side in the hole drilling direction, and is provided with a second water passage hole at a position corresponding to the convex portion, the second water passage hole having a size smaller than a size of the convex portion in a plan view, In the step D, the drilling water supplied to the first hollow is discharged forward in the drilling direction through the first water passage hole and the second water passage hole, The method for installing a casing with a built-in freezing pipe is characterized in that in step E, the tip of the freezing pipe is brought into contact with the check valve or positioned in the vicinity of the check valve.

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