JP2011169057A - Method of constructing vertical shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of constructing a vertical shaft, which surely steps water and can shorten the work period. <P>SOLUTION: In the method of constructing the vertical shaft, a shaft bottom part D in a vertical-shaft wall body 1 is cooled with ground water B accumulated in the vertical-shaft wall body 1 after the earth and sand is discharged from the vertical-shaft wall body 1, thereby freezing the entire range of the shaft bottom part D with a predetermined thickness. Subsequently, the ground water B is discharged from the vertical-shaft wall body 1, and bottom plate concrete 6 with a frozen part 4 as a base is placed above the frozen part 4 of the shaft bottom part D within the vertical-shaft wall body 1, while the shaft bottom part D is in the frozen state. A series of these operations eliminates the need for placing the bottom plate concrete 6 underwater, and further a gap is hardly generated between the vertical-shaft wall body 1 and the shaft bottom part D by freezing the entire range of the shaft bottom part D with the predetermined thickness. Accordingly, the ground water is hard to infiltrate into the vertical-shaft wall body 1, thereby quickly and surely pumping up the ground water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a shaft construction method used for tunnel construction and the like.

  When constructing a shaft deeper than the groundwater level, the ground may be excavated with the spring water (groundwater) left in the shaft wall, and then bottom concrete may be placed in the bottom of the shaft wall in water. In that case, the spring water invading into the shaft wall is discharged from the shaft wall by the pump after the bottom concrete is hardened. At this time, if there is a gap between the bottom base concrete and the shaft wall body, water will continue to enter from the gap, so it is necessary to stop the water. Japanese Patent Application Laid-Open No. 2005-282199 discloses a water stop method that freezes a gap and prevents intrusion of spring water.

JP 2005-282199 A

  However, in the conventional shaft construction method described above, since the bottom base concrete is driven in a state where there is spring water in the shaft wall body, a gap is easily formed between the bottom base concrete and the shaft wall body, and there is a gap, It is necessary to take measures against water stoppage as disclosed in Japanese Patent Application Laid-Open No. 2005-282199 and work such as placing bottom base concrete again. Such a series of work has a problem that the construction period becomes long and at the same time, it is difficult to reliably stop water.

  An object of this invention is to provide the construction method of the shaft which made it possible to shorten the construction period while performing water stop reliably.

The construction method of the shaft according to the present invention includes a step of constructing a shaft wall body in the ground,
A step of cooling the bottom of the shaft wall in a state where groundwater has accumulated in the shaft wall after the sediment discharge, and freezing the entire range of the bottom of the shaft at a predetermined thickness;
A process of discharging groundwater in the shaft wall with the bottom of the shaft frozen,
And a step of discharging groundwater when the bottom of the well is frozen.

  In this shaft construction method, after discharging the sediment in the shaft wall, with the groundwater accumulated in the shaft wall, the bottom of the shaft wall is cooled, and the entire range of the bottom of the shaft is covered with a predetermined thickness. Freeze. Thereafter, the groundwater in the shaft wall is discharged. And by discharging groundwater, it is possible to safely and easily carry out post-processes such as placing bottom concrete in the shaft wall with the frozen portion at the bottom of the shaft as a base. The shaft wall includes concrete underground continuous wall, soil cement underground continuous wall, caisson and the like. By such a series of operations, it is not necessary to place the bottom base concrete in water, and the bottom of the well is frozen over the entire range, so that there is a gap between the shaft wall and the bottom of the shaft. It is hard to generate | occur | produce, and it becomes difficult for groundwater to penetrate | invade into a shaft wall by this, and the drawing-out operation | work of groundwater can be performed rapidly and reliably. Therefore, if this construction method is used, a reliable water stop effect can be obtained and the construction period can be shortened.

The freezing pipe used in the bottom bottom freezing process includes a cooling pipe extending in a substantially horizontal direction and a refrigerant transport pipe extending in a substantially vertical direction from both ends of the cooling pipe and communicating with the cooling pipe. Thus, it is preferable that the cooling pipe is submerged until it hits the bottom of the shaft wall in a state where groundwater is accumulated in the shaft wall.
When the freezing pipe having such a structure is used, it is only necessary to sink the freezing pipe from the upper opening of the shaft wall body after discharging the earth and sand, so that workability is good and the length of the pipe can be easily adjusted by adding the pipe. Therefore, workability on site is very good.

Further, it is preferable that a freezing backfill material is introduced into the shaft wall so that the cooling tube is buried after the cooling tube hits the bottom of the shaft wall.
In this way, the bottom of the well is frozen in the state where the cooling pipe is filled with the backfill material, so that the cooling pipe is not exposed in the water, so that the cooling efficiency is improved and the bottom of the well is strengthened. Can be frozen. As the backfill material, sandy soil or fluidized soil is suitable.

Further, it is preferable that the cooling pipe has an arch shape that bulges downward.
By using such a cooling pipe, an arch-shaped frozen part that bulges downward can be formed, which is effective when the water pressure is high to push up the frozen part from below.

The cooling pipes are preferably arranged in a plurality of stages in the vertical direction.
When such a cooling pipe is used, a thick frozen portion can be reliably formed. In addition, the construction period can be shortened by shortening the freezing time.

In addition, since mud adheres to the inner wall surface of the shaft wall body, it is preferable to remove mud in a portion that comes into contact with the frozen portion before the backfill material is charged.
In this case, by increasing the adhesion of the frozen portion to the inner wall surface of the shaft wall body, it is possible to increase the frosting shear strength between the shaft wall body and the frozen portion, thereby improving the water stop effect.

In addition, it is preferable that reinforcing fibers are mixed in the shaft wall body in a portion where mud is removed.
If such a structure is employ | adopted, adhesion with an inner wall surface and a frozen part will become strong with the reinforcement fiber which appeared on the inner wall surface, and the further water stop effect can be acquired.

  Further, it is preferable that another refrigeration pipe is embedded in the shaft wall to the bottom, and the lower part is frozen from the lower end of the shaft wall.

  By adopting such a configuration, the bottom edge depth of the shaft wall body is shallower than the cutting depth of the internal ground, or approximately the same, within the range where there is no problem in safety of construction, so that the periphery of the frozen part The part can be formed so as to cover a part or the whole of the lower end surface of the shaft wall. In this way, the frozen part that is about to be pushed upward by the water pressure from below can be received by the lower end surface of the shaft wall body, which is reasonable.

  According to the present invention, it is possible to reliably stop the water and at the same time shorten the construction period.

It is sectional drawing which shows the 1st-3rd process in 1st Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows the 4th-6th process in 1st Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows the 7th and 8th process in 1st Embodiment of the construction method of the shaft which concerns on this invention. It is a top view of piping for freezing in a shaft wall. It is sectional drawing which shows the 1st-3rd process in 2nd Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows the 4th-6th process in 2nd Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows the 7th-9th process in 2nd Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 3rd Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 4th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 5th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 6th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 7th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 8th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 9th Embodiment of the construction method of the shaft which concerns on this invention. It is sectional drawing which shows 10th Embodiment of the construction method of the shaft which concerns on this invention.

  Hereinafter, a preferred embodiment of a shaft construction method according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIG. 1 (a), the shaft wall 1 constructed until reaching a predetermined depth from the ground plane A is filled with groundwater B even after the earth and sand are discharged. In this case, the bottom C of the shaft wall body 1 is sand ground, and groundwater easily enters the shaft wall body 1 from the bottom C.

  As shown in FIG. 1 (b), the freezing pipe 2 is submerged in the groundwater B from the upper opening 1 b of the shaft wall 1. The freezing pipe 2 includes a cooling pipe 2a extending in the horizontal direction and a refrigerant transport pipe 2b extending in the vertical direction from both ends of the cooling pipe 2a and communicating with the cooling pipe 2a. And this cooling pipe 2a is sunk until it hits the bottom C of the shaft wall 1. The cooling pipe 2a is easily exposed to water in an exposed state, the refrigerant transport pipe 2b is covered with a heat insulating material, and the refrigerant transport pipe 2b is connected to a refrigerant supply source (not shown).

  As shown in FIG. 4, in this shaft wall body 1, a plurality of (for example, nine) freezing pipes 2 </ b> A to 2 </ b> I are used. The cooling pipes 2 a of the freezing pipes 2 </ b> A to 2 </ b> I extend in the chord direction of the inner wall surface 1 a having a circular cross section of the shaft wall body 1 and are disposed substantially parallel on the bottom C of the shaft wall body 1. . In addition, each refrigerant transport pipe 2 b of the freezing pipes 2 </ b> A to 2 </ b> I extends in the vertical direction along the inner wall surface 1 a of the shaft wall 1.

  When the freezing pipe 2 having such a configuration is used, it is only necessary to sink the freezing pipe 2 from the upper opening 1b of the shaft wall body 1 after discharging the sediment. Since the thickness can be adjusted easily, the workability on site is very good.

  Next, as shown in FIG.1 (c), the refillable earth | ground 3 which can be frozen is thrown in into the shaft wall body 1, and each cooling pipe 2a of the piping 2A-2I for freezing is buried. As the backfill soil 3, sandy soil or fluidized soil is used. In this way, the bottom portion D is frozen in a state where the cooling pipe 2a is filled with the backfill soil 3, so that the cooling pipe 2a is not exposed, so that the cooling efficiency is improved and the bottom portion D is obtained. Can be frozen firmly.

  Then, as shown in FIG.2 (d), the refrigerant | coolant flow is started in each freezing piping 2A-2I. And the bottom part D in the shaft wall 1 is cooled, and the bottom part D is frozen by the predetermined thickness over the whole range. At this time, the upper and lower sides of the cooling pipe 2a are frozen in the bottom portion D, and are also frozen below the backfill soil 3 and the bottom C after excavation. This portion becomes a disk-shaped frozen portion 4.

  Then, as shown in FIG.2 (e), the groundwater B in the shaft wall 1 is discharged | emitted. At this time, if the backfill soil 3 </ b> A is sandy soil, the unfrozen surplus backfill soil 3 </ b> A accumulated on the freezing portion 4 is also pumped out together with the groundwater B.

  Thereafter, as shown in FIG. 2 (f), the base plate concrete 6 is formed by laying the heat insulating sheet 5 on the surface of the frozen portion 4 using the frozen portion 4 as a base and placing concrete on the heat insulating sheet 5. To do. Since the concrete of the bottom base concrete 6 is hard to be solidified at a low temperature, the heat insulating sheet 5 prevents the low temperature during the solidification of the bottom base concrete 6.

  After the bottom concrete 6 is solidified, as shown in FIG. 3 (g), the freezing part 4 is thawed by flowing a heating medium in each of the freezing pipes 2A to 2I. Then, as shown in FIG.3 (h), the part exposed from the bottom base concrete 6 among the refrigerant | coolant conveyance pipes 2b is cut | disconnected in the position of the upper surface of the bottom base concrete 6. FIG. In the freezing pipe 2, the remaining part after cutting is filled with the grout 7 through the cutting opening 2c of the refrigerant transport pipe 2b and sealed, and the construction work of the shaft is completed.

[Second Embodiment]
As shown in FIG. 5 (a), the shaft wall 1 constructed until reaching a predetermined depth from the ground plane A is filled with the groundwater B even after the earth and sand are discharged. In this case, although the bottom C of the shaft wall body 1 is ground mixed with clay, there is a possibility that groundwater may enter the shaft wall body 1 from the bottom C or the boundary between the shaft wall body 1 and the bottom C. . Furthermore, there exists a possibility that the bottom C may rise and be destroyed by the action of water pressure from below.

  When the soil mixed with clay is frozen, the volume expands and the freezing pipe 2 is pushed up. As a result, as shown in FIG. Inside, a backfilling soil 13 such as sandy soil or fluidized soil is put. The surface 13a of the backfill soil 13 is leveled flat.

  As shown in FIG. 5 (c), the freezing pipe 2 is submerged in the groundwater B from the upper opening 1 b of the shaft wall 1. The freezing pipe 2 includes a cooling pipe 2a extending in the horizontal direction and a refrigerant transport pipe 2b extending in the vertical direction from both ends of the cooling pipe 2a and communicating with the cooling pipe 2a. And this cooling pipe 2a is sunk until it hits the bottom E of the shaft wall 1. The cooling pipe 2a is easily exposed to water in an exposed state, the refrigerant transport pipe 2b is covered with a heat insulating material, and the refrigerant transport pipe 2b is connected to a refrigerant supply source (not shown). In this case, a plurality of (for example, nine) freezing pipes 2A to 2I as shown in FIG. 4 are used.

  Next, as shown in FIG. 6 (d), another backfilling soil 23 that can be frozen is put into the shaft wall body 1 to fill the cooling pipes 2 a of the freezing pipes 2 </ b> A to 2 </ b> I. As the backfill soil 23, sandy soil or fluidized soil is used. Thus, since the bottom hole D is frozen in the state where the cooling pipe 2a is filled with the backfill soil 23, the cooling pipe 2a is not exposed, so that the cooling efficiency is improved, and the bottom bottom D Can be frozen firmly.

  Thereafter, as shown in FIG. 6 (e), the refrigerant starts to flow in each of the freezing pipes 2A to 2I. And the bottom part D in the shaft wall 1 is cooled, and the bottom part D is frozen by the predetermined thickness over the whole range. At this time, the upper and lower portions of the cooling pipe 2a are frozen at the bottom portion D, and the backfill soils 13 and 23 are frozen. This portion becomes a disk-shaped frozen portion 4.

  Then, as shown in FIG.6 (f), the groundwater B in the shaft wall 1 is discharged | emitted. When the backfill material is sandy soil, the unfrozen surplus backfill soil 23 </ b> A accumulated on the freezing portion 4 is also pumped out together with the groundwater B.

  Thereafter, as shown in FIG. 7 (g), with the frozen portion 4 as a base, a heat insulating sheet 5 is laid on the surface of the frozen portion 4, and concrete is placed on the heat insulating sheet 5 to form the bottom concrete 6 To do. Since the concrete of the bottom base concrete 6 is difficult to solidify at a low temperature, the heat insulating sheet 5 prevents the low temperature during the solidification of the bottom base concrete 6.

  After the bottom base concrete 6 is solidified, as shown in FIG. 7 (h), the freezing part 4 is thawed by flowing a heating medium in each of the freezing pipes 2 </ b> A to 2 </ b> I. Thereafter, as shown in FIG. 7 (I), the portion of the refrigerant transport pipe 2 b exposed from the bottom concrete 6 is cut at the position of the top surface of the bottom concrete 6. Of the freezing pipe 2, the remaining part after cutting is filled with the grout 7 from the cutting opening 2c of the refrigerant transfer pipe 2b and sealed, and the construction work of the shaft is completed.

  In the shaft construction method according to the first and second embodiments described above, the groundwater B is accumulated in the shaft wall body 1 after the earth and sand is discharged in the shaft wall body 1, The bottom portion D is cooled, and the entire range of the bottom portion D is frozen at a predetermined thickness. Thereafter, the groundwater B in the shaft wall 1 is discharged. By discharging the groundwater, subsequent processes such as placing the bottom base concrete 6 in the shaft wall 1 based on the frozen part 4 of the bottom part D can be performed safely and easily. With the bottom portion D frozen, a bottom concrete 6 is placed in the vertical wall body 1 above the freezing portion 4 of the bottom portion D with the frozen portion 4 as a base. By discharging the groundwater, subsequent processes such as placing the bottom base concrete 6 in the shaft wall 1 based on the frozen part 4 of the bottom part D can be performed safely and easily.

  And after putting the bottom base concrete 6 and solidifying to sufficient intensity | strength, the frozen part 4 is thawed. By such a series of operations, it is not necessary to place the bottom base concrete 6 in the water, and the bottom wall D is frozen over the entire range with a predetermined thickness, so that the shaft wall 1 and the bottom wall It is difficult for a gap to be formed between the groundwater D and the groundwater, thereby making it difficult for groundwater to enter the shaft wall body 1 so that the groundwater can be pumped out quickly and reliably. Therefore, if this construction method is used, a reliable water stop effect can be obtained and the construction period can be shortened.

  It goes without saying that the present invention is not limited to the embodiment described above.

  As shown in FIG. 8, the other freezing pipes 20 have a cooling pipe 20a extending in a substantially horizontal direction with an arch shape bulging downward, and extending in the vertical direction from both ends of the cooling pipe 20a. The refrigerant transport pipe 2b communicates with the cooling pipe 20a. Then, the cooling pipes 20a of the plural (for example, nine) freezing pipes 20A to 20I are submerged until they hit the bottom C of the shaft wall body 1.

  By using such a cooling pipe 20a, it is possible to form an arch-shaped frozen portion 4A that bulges downward, which is effective when the water pressure that pushes up the frozen portion 4 from the bottom is high. is there.

  As shown in FIG. 9, in the shaft wall 1, the cooling pipe 30a of the outer freezing pipes 30A to 30I and the cooling pipe 40a of the inner freezing pipes 40A to 40E are arranged in two stages in the vertical direction. . The cooling pipe 40a is arranged in parallel to the lower cooling pipe 30a without crossing when viewed from above. In this way, by forming the frozen portion 4 with a pair of cooling pipes 30a and 40a, a thick frozen portion 4 can be reliably formed. In addition, the construction period can be shortened by shortening the freezing time. Note that the thicker the frozen portion 4 can be easily formed as the number of cooling pipes increases.

  As shown in FIG. 10, in the shaft wall 1, the cooling pipes 50 a of the outer freezing pipes 50 </ b> A to 50 </ b> I and the cooling pipes 60 a of the inner freezing pipes 60 </ b> A to 60 </ b> E are vertically arranged in two stages. . The lower cooling pipes 50a are arranged at equal intervals, and the upper cooling pipe 60a is arranged so as to cross the lower cooling pipe 50a, and is arranged only in the center portion. By arranging in this way, the central portion of the frozen portion 4 can be cooled at a lower temperature than the other portions, so that the strength of the central portion of the frozen portion 4 can be increased. Note that the thicker the frozen portion 4 can be easily formed as the number of cooling pipes increases.

  As shown in FIG. 11, H or I-shaped steel 71 as a reinforcing member is disposed between the cooling pipes 70 a of the outer freezing pipes 70 </ b> A to 70 </ b> I in the shaft wall 1, and the frozen portion 4 is the shaped steel 71. It is reinforced. And the center part of the frozen part 4 can be strengthened rather than another part by arranging the shape steel 71 in the center part.

  As shown in FIG. 12, the freezing pipe 80 includes a cooling pipe 80a extending in the vertical direction and a refrigerant transport pipe 2b extending in the vertical direction from the upper end of the cooling pipe 80a and communicating with the cooling pipe 80a. . The inside of the freezing pipe 80 is composed of an outgoing pipe and a return pipe so that the refrigerant can reciprocate. Such freezing pipes 80 are submerged in the shaft wall 1 until reaching the bottom, and the number thereof is arbitrary. By using such a freezing pipe 80, it is possible to arrange the freezing pipes 80 in a dense manner, and it is possible to shorten the construction period by shortening the freezing time.

  As shown in FIG. 13, a pilot shaft 91 is formed at a position away from the shaft wall 1, and cooling pipes 90 a extend radially from the pilot shaft 91 in a substantially horizontal direction. The freezing pipe 90 includes a cooling pipe 90a extending radially, and a refrigerant transport pipe 2b extending in an L shape from the end of the cooling pipe 90a and communicating with the cooling pipe 90a. The freezing pipe 90 is composed of an outgoing pipe and a return pipe so that the refrigerant can reciprocate, and the refrigerant transport pipe 2 b is arranged in the pilot shaft 91. By using such a freezing pipe 90, the pipe is not exposed in the shaft wall body 1 after the formation of the frozen portion 4, so that the groundwater B can be easily discharged.

  As shown in FIG. 14, linear freezing pipes 100 are arranged along the inner wall surface 1 a of the shaft wall body 1, and a U-shaped freezing pipe 101 is provided in the central portion of the shaft wall body 1. It is arranged. The freezing pipe 100 includes a cooling pipe 100a extending in the vertical direction, and a refrigerant transport pipe 2b extending in the vertical direction from the upper end of the cooling pipe 100a and communicating with the cooling pipe 100a. The freezing pipe 101 includes a cooling pipe 101a extending in the horizontal direction and a refrigerant transport pipe 2b extending in the vertical direction from both ends of the cooling pipe 101a and communicating with the cooling pipe 101a. By adopting such a configuration, the joint portion between the freezing portion 4 and the inner wall surface 1a of the shaft wall body 1 can be easily and reliably cooled by the straight freezing pipe 100. The joining strength with the inner wall surface 1a of the shaft wall body 1 can be increased, and further strengthening of water stoppage measures in the vicinity of the inner wall surface 1a can be achieved.

  As shown in FIG. 15, the freezing pipe 21 embedded at equal intervals in the vertical wall 1 is a cooling pipe 21 a that extends in the horizontal direction near the lower end of the vertical wall 1 at the lower end of the freezing pipe 21. And a refrigerant transport pipe 2d that extends in the vertical direction from both ends of the cooling pipe 21a and communicates with the cooling pipe 21a. Since the cooling pipe 21 a can cool the vicinity of the lower end of the shaft wall body 1, the lower part can be frozen from the lower end of the shaft wall body 1. The freezing pipe 21 may use the freezing pipe 80 shown in FIG. Other configurations are the same as those shown in FIG. 8, and detailed description thereof is omitted.

  By adopting such a configuration, the freezing portion 4A can be obtained by making the lower end depth of the shaft wall body 1 shallower than the cutting depth of the internal ground or substantially the same within a range where there is no safety problem in construction. Can be formed so as to cover a part or the whole of the lower end surface of the shaft wall 1. In this way, the frozen portion 4A that is about to be pushed upward by the water pressure from below can be received by the lower end surface of the shaft wall body 1 and is reasonable.

  As shown in FIG. 10, since mud adheres to the inner wall surface 1a of the shaft wall body 1, mud in a portion that comes into contact with the frozen portion 4 is removed before the backfilling soil is charged. In this case, the adhesion of the frozen part 4 to the inner wall surface 1a of the shaft wall 1 is enhanced, thereby increasing the frosting shear strength between the shaft wall 1 and the frozen part 4 and improving the water stop effect. Can be made. Mud removal includes high pressure water injection and brush cleaning.

  Reinforcing fibers (fibers made of steel) are mixed in the shaft wall 1 at a portion where mud is removed. If such a structure is employ | adopted, adhesion with the inner wall face 1a and the frozen part 4 will become strong with the reinforcement fiber which appeared on the inner wall face 1a, and the further water stop effect can be acquired.

  As the backfill material, sandy soil or fluidized soil is suitable.

The shaft wall 1 includes a concrete underground continuous wall, a soil cement underground continuous wall, and a caisson.

    DESCRIPTION OF SYMBOLS 1 ... Vertical wall body, 1a ... Inner wall surface, 1b ... Upper opening, 2, 2A-2I, 20A-20I, 30A-30I, 40A-40E, 50A-50I, 60A-0E, 70A-70I ... Freezing piping, 2a, 2d ... cooling pipe, 2b ... refrigerant transport pipe, 3 ... backfilling soil, 4, 4A ... freezing section, 5 ... heat insulation sheet, 6 ... bottom concrete, 13 ... backfilling soil (backfilling material), 20, 21 ... Freezing pipe, 20a, 21a ... Cooling pipe, 23 ... Backfill soil (backfilling material), 30a, 40a, 50a, 60a, 70a ... Cooling pipe, 80 ... Freezing pipe, 80a ... Cooling pipe, 90 ... Freezing Pipe for piping, 90a ... Cooling pipe, 100 ... Piping for freezing, 100a ... Cooling pipe, 101 ... Piping for freezing, 101a ... Cooling pipe, B ... Ground water, C, E ... Bottom, D ... Bottom of well.

Claims (8)

Building a shaft wall in the ground,
A step of cooling the bottom of the shaft wall in a state where groundwater has accumulated in the shaft wall after sediment discharge, and freezing the entire range of the shaft bottom with a predetermined thickness;
A step of discharging groundwater in the shaft wall in a state where the bottom of the shaft is frozen;
And a step of discharging groundwater in a frozen state of the bottom of the shaft.   The freezing pipe used in the freezing step of the bottom portion includes a cooling pipe extending in a substantially horizontal direction, a refrigerant transport pipe extending in a substantially vertical direction from both ends of the cooling pipe and communicating with the cooling pipe. 2. The shaft construction method according to claim 1, wherein the cooling pipe is submerged in a state where ground water is accumulated in the shaft wall until it hits a bottom of the shaft wall.   3. The shaft according to claim 2, wherein after the cooling pipe hits the bottom of the shaft wall body, a freezeable backfill material is introduced into the shaft wall body so that the cooling pipe is buried. Construction method.   4. The shaft construction method according to claim 2, wherein the cooling pipe has an arch shape that bulges downward.   The said cooling pipe is arranged in multiple steps in the up-down direction, The construction method of the shaft as described in any one of Claims 2-4 characterized by the above-mentioned.   6. Since mud adheres to the inner wall surface of the shaft wall body, mud in a portion that comes into contact with the frozen portion is removed before the backfilling material is charged. The construction method of the shaft described in the paragraph.   The shaft construction method according to claim 6, wherein a reinforcing fiber is mixed in a portion of the shaft wall body where the mud is removed.   The construction of the shaft according to any one of claims 1 to 7, wherein another refrigeration pipe is embedded in the shaft wall to the bottom, and the lower part is frozen from the lower end of the shaft wall. Method.

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