JP2005344460A - Tunnel receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tunnel prelining method which enables construction, to be performed even in the natural ground including the spring ground, and also serves as measures against spring water. <P>SOLUTION: In the tunnel prelining method for excavating a tunnel 5 on the natural ground divided into the non-spring ground 1 and the spring ground 2, a perforated steel pipe 4A and a freezing pipe 4B are driven in the ground 1 and the ground 2 from the leading end 3 of an existing tunnel to be disposed as prelining above an excavation area. An improving body 6 is created by injecting a grout into the natural ground from the perforated steel pipe 4A, and the ground is frozen to form frozen soil 7 by introducing a refrigerating means into the freezing pipe 4B. These are formed above the tunnel 5 in an arch shape so that the construction doubling as the measures against the spring water can be performed in the ground 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tunnel tip receiving method.

Conventionally, in the mountain tunnel construction method, a tunnel tip receiving method that can be constructed from the inside of the tunnel has been widely used as an auxiliary construction method for stabilizing the top of a natural mountain having poor geology. For example, a long steel pipe fore-piling method (hereinafter abbreviated as AGF method) is widely used.
The AGF method is drilled with a drill jumbo, which is a general-purpose machine, and a plurality of AGF steel pipes with injection holes on the side are inserted to form an arch in front of the face, and injection material is injected from the AGF steel pipes into the ground. Thus, an improved body is formed with respect to the natural ground around the AGF steel pipe.
Although the AGF method can be constructed at a relatively low cost, it may not be possible to form a homogeneous improvement body for soft ground, which may cause a small-scale collapse between adjacent steel pipes. there were.
In order to improve such a problem, for example, Patent Document 1 injects a shield grout from a steel pipe into a natural ground to form an improved body, and then injects a grout for osmotic injection while breaking the shield grout, An AGF method for creating a homogeneous improvement is described.
JP 2000-337078 A (page 4-5, FIG. 6-8)

However, the conventional tunnel tip receiving method as described above has the following problems.
In the technique described in Patent Document 1, a homogeneous improvement body can be formed by injecting the injection material a plurality of times. However, since the improvement body is limited to the periphery of the AGF steel pipe, large-scale ground improvement cannot be performed. However, there is a problem that it is difficult to stop the water when the natural ground includes springy ground. Therefore, there is a problem that it is necessary to take another spring countermeasure.
In recent years, in order to make effective use of the underground, there is an increasing demand for building a mountain tunnel underground in an urban area where alluvium and divergent formations are intricately complicated. More and more are encountered. For this reason, there are many main roads and dense buildings on the ground to take measures against spring water, so it is often difficult to implement countermeasures from the ground.
Therefore, there is a strong demand for a tunnel tip receiving method that can take effective spring countermeasures even when encountering spring ground.

  The present invention has been made in view of the above problems, and provides a tunnel tip receiving method capable of performing construction that also serves as a spring water countermeasure even in a natural ground including a spring ground. For the purpose.

In order to solve the above problems, in the invention described in claim 1, a pipe member is inserted in the vicinity of the tunnel excavation region, and an injection material for ground improvement is injected into the ground from the side of the pipe member. In the tunnel receiving method for stabilizing the top end, the ground where the pipe member is inserted is a spring ground, and instead of injecting the injection material, the ground is frozen on the pipe member. A method of freezing the ground by inserting a freezing means is provided.
According to this invention, the freezing means is inserted and the ground is frozen in the region that is the spring ground in the pipe member that injects the injection material into the natural ground for ground improvement. Therefore, in the natural ground area of the non-spring ground, the ground improvement with the injection material will be performed to take measures for stability at the top, and in the natural ground area of the spring ground, spring measures will be taken to prevent the spring water by the freezing method. Can do. At that time, since the freezing means is inserted into the pipe member to perform freezing, each construction can be continuously performed from the inside of the tunnel.

According to a second aspect of the present invention, in the tunnel tip receiving method according to the first aspect, when the pipe member is inserted into the ground, depending on the spring water of the ground at the installation position of the pipe member, The injection tube provided with the injection hole for the injection material and the freezing tube not having the injection hole on the side portion are selectively replaced and inserted into the region where the injection tube is arranged in order from the tip side. In this case, the injection material is injected into a natural ground, and the region where the freezing pipe is disposed is frozen by the freezing means.
According to the present invention, the pipe member to be inserted into the ground is inserted by selectively replacing the injection pipe having the injection hole and the freezing pipe not having the injection hole according to the spring water of the ground. However, an inexpensive freezing tube can be used within the required range.

According to a third aspect of the present invention, in the tunnel tip receiving method according to the second aspect, the refrigeration unit circulates a coolant flow path in the freezing pipe, and the cooling medium flow path is connected to the freezing pipe. It is set as a construction method provided with the heat insulation member which insulates with respect to the pipe members other than.
According to the present invention, it is possible to cool and freeze the surrounding ground through the freezing pipe by sending the coolant from the coolant flow path and circulating it in the freezing pipe disposed on the spring ground.
Moreover, since the coolant channel is insulated by the heat insulating member for the pipe members other than the frozen pipe, the cooling efficiency can be increased, and the construction is easy even if the pipe member is long. Moreover, since the inside of the pipe member behind it is not cooled after completion of freezing, the ground can be improved continuously and efficient construction can be performed.

According to a fourth aspect of the present invention, in the tunnel tip receiving method according to the first or second aspect, the refrigeration means includes an endothermic unit in which a coolant circulates inside and is movable within the pipe member, A construction method includes a coolant channel for circulating the coolant in the heat absorption unit and a heat insulating member for insulating the coolant channel from the pipe member.
According to the present invention, since the refrigeration means is provided with the heat absorption unit that circulates the coolant inside the pipe member so as to be movable, the pipe member is cooled by arranging the heat absorption unit at an appropriate position in the pipe member. The surrounding spring ground can be cooled and frozen.
Further, since the coolant circulates inside the heat absorption unit, the recovery becomes easy and the post-treatment of the remaining coolant becomes unnecessary, so that the switching to the next process can be performed quickly.
Moreover, since the coolant channel is insulated by the heat insulating member for the pipe members other than the frozen pipe, the cooling efficiency can be increased, and the construction is easy even if the pipe member is long. Moreover, since the inside of the pipe member behind it is not cooled after completion of freezing, the ground can be improved continuously and efficient construction can be performed.

According to a fifth aspect of the present invention, in the tunnel tip receiving method according to any one of the first to third aspects, at least the rear end side of the pipe member into which the injection material is injected is filled prior to the insertion of the refrigeration means. The construction method is to close with material.
According to this invention, since at least the rear end side of the pipe member into which the injection material is injected is closed with the filler, the front end side of the pipe member into which the refrigeration means is inserted can be closed, and the ground in the necessary range can be efficiently obtained. Can be frozen.

  According to the tunnel tip receiving method of the present invention, the ground can be frozen by inserting freezing means into the pipe member so that the ground can be frozen. Measures for stability at the top and springs in the ground area of spring ground can be blocked by freezing method, so even if it is a ground including spring ground, it should also be used as a spring countermeasure. There is an effect that can be.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.
A tunnel tip receiving method according to an embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view along a tunnel extending direction schematically showing a state in front of a tunnel face under construction by a tunnel tip receiving method according to an embodiment of the present invention. 2A and 2B are cross-sectional views taken along lines AA and BB in FIG. 1, respectively.

The tunnel tip receiving method of this embodiment is a method of injecting an injection material into a natural ground and freezing a springy ground through a pipe member inserted into the natural ground by a so-called long steel pipe fore-pyring (AGF) method. This is a construction method that can easily take measures against the spring from the inside of the tunnel even when there is spring ground in the natural area, and make it possible to achieve both top stability and spring measures.
An example of the leading construction formed by this construction method will be described.
As shown in FIG. 1, the natural ground to which the present construction method can be applied is, for example, in front of the face 3 a of the existing tunnel tip 3 (on the left side in the drawing), a non-spring ground 1 made of the Kazusa Group and having a stable soil quality, The spring ground 2 composed of soft ground such as the alluvium and hong stack located below the groundwater level is intricately distributed.
Therefore, when the tunnel 5 (shown broken line) is extended from the existing tunnel tip 3, a part of the tunnel excavation region crosses the spring ground 2. Such a situation is likely to be encountered when, for example, a tunnel or an underground structure is provided underground in an urban area. Although the location of the spring ground 2 can be accurately grasped by drilling surveys, etc., there are many roads and buildings already on the ground, and it may be difficult to implement spring countermeasures from the ground. Many.

In this construction method, the perforated steel pipe 4A (injection pipe), the freezing pipe 4B, and the perforated steel pipe 4A are inserted above the extension area of the tunnel 5, and the section in the tunnel extension direction is provided around each of them. An improved body 6, a frozen soil 7, and an improved body 6 are continuously formed over L ₁ , L ₂ , and L ₃ (hereinafter, the lengths are also expressed as L ₁ , L ₂ , and L ₃ ), respectively.
Further, in the cross section orthogonal to the direction in which the tunnel extends, the perforated steel pipe 4A and the freezing pipe 4B have an appropriate pitch in an arch shape at the top of the tunnel 5, as shown in FIGS. 2 (a) and 2 (b). The improved body 6 and the frozen soil 7 are formed without any gap between them.
Here, the sections L ₁ and L ₃ are provided within the range of the non-springy ground 1. On the other hand, the interval L ₂ where permafrost 7 cryotubes 4B is inserted is formed, across the seep ground 2, at both ends is set to span slightly HiYu aqueous ground 1. As a result, the spring water generated from the spring ground 2 is frozen by the frozen soil 7 so that it does not penetrate downward, and spring water during construction of the tunnel 5 is prevented.

Next, the tunnel tip receiving method according to the embodiment of the present invention will be described for each step.
The outline process of this construction method consists of a pipe member placing process, an improved body creation process, a pre-freezing treatment process, and a freezing process.
3A, 3B, and 3C are cross-sectional explanatory views along the tunnel extending direction for sequentially explaining each step of the tunnel tip receiving method according to the embodiment of the present invention. FIGS. 4D and 4E are cross-sectional explanatory views for explaining the process following FIG. FIG. 4F is a cross-sectional view taken along the line CC in FIG.
In FIGS. 3A, 3B, 3C, 4D, and 4E, the horizontal direction shown in FIG. 3 is the same as the horizontal direction in FIG. That is, although not shown in the figure, the existing tunnel tip 3 of FIG. 1 is provided on the right side of the figure.

The pipe member placing step is a step of placing (inserting) a pipe member serving as a receiving work in a natural ground.
First from working face 3a, only pouring the length L ₁ of the perforated steel tube 4A above the excavation area of the tunnel 5, and pouring the length L ₂ of the cryotubes 4B instead splicing thereto, perforated instead splicing thereto by pouring the steel pipe 4A by the length L _3, to insert the one previously received Engineering in the natural ground. Then, the cutting edge 3a is appropriately spaced from the first placement position, and another leading support is similarly placed, and an arch is formed on the top end side of the tunnel 5 as shown in FIG. 2 (a). Will be placed sequentially.

First, at least as in the conventional AGF construction method, the placement interval between the non-spring ground 1 is an arch-shaped improvement body 6 formed around each soil in consideration of the earth pressure to be supported and the soil texture. It is set as the space | interval which can connect in the circumferential direction of this and can stabilize a top | upper end. Further, in consideration of the refrigeration capacity of the refrigeration means, construction time, and the like, the interval is such that the frozen soil 7 having sufficient strength is continuously formed in the circumferential direction in the springy ground 2.
The casting length is usually equal to or longer than the length used in the conventional AGF method. For example, it can be set to about 50 to 100 m. However, when crossing the springy ground 2, it is preferable that at least the tip reaches a region of the non-springy ground 1 as shown in FIG. 1.
Further, in FIG. 1, the casting angle is a shallow angle slightly upward in the tunnel extending direction, but as in the conventional AGF method, it is larger in order to secure a working space for the next pipe member placing process. It may be an inclination angle.
Such placement can be performed from the existing tunnel tip 3 by arranging, for example, a drill jumbo or the like. That is, for example, while drilling with a PCD (Pipe Casting Drill) bit or the like, the pipe member is inserted into the drilled portion, and after the placement, the PCD bit is closed and the bit is collected through the pipe member. However, it goes without saying that a dedicated placement machine may be used as necessary, for example, in the case of a very long length.

As shown in FIGS. 2 and 3 (a), the perforated steel pipe 4A is a circular cross-section steel pipe having a smooth inner surface, and a plurality of injection holes 4a are provided with appropriate intervals in the longitudinal direction and the circumferential direction at the side thereof. Are arranged. And the connection part 4b is formed in the end part by the suitable joint shape in order to connect with another pipe member, and it can add and replace. Therefore, depending on the length of a section L _1, a perforated steel tube 4A and a plurality of replenishing forming an elongated steel pipe.
The injection hole 4a may be a through-hole, but a backflow prevention valve or the like may be provided so as to prevent backflow of fluid from the natural mountain side on the outer periphery of the perforated steel pipe 4A.

The freezing pipe 4B is a cylindrical steel pipe having a smooth inner surface and the same inner diameter as the perforated steel pipe 4A. In this embodiment, an opening such as an injection hole is not provided on the side portion. Therefore, since it can be set as a simple structure, it can manufacture at low cost from a general purpose steel material.
On the other hand, a connecting portion 4b that can be connected to the perforated steel pipe 4A and another frozen pipe 4B is provided at the end, and can be added and replaced in the same manner as the perforated steel pipe 4A.

Next, as shown in FIGS. 3 (b) and 3 (c), the improved body creation process is performed by injecting the injection material 9 into the ground of the non-spring ground 1 from the perforated steel pipe 4 </ b> A on the leading end side. In this process, the improved body 6 is formed around the perforated steel pipe 4A.
First, the improved material 6 is formed by injecting the injection material 9 into the natural ground ahead from the tip opening of the perforated steel pipe 4A (see FIG. 3A). This creation can be performed by injection means as appropriate. For example, an injection hole may be provided at the tip of a drill jumbo or the like used in the pipe member placing step, and the injection material 9 may be injected without exchanging the machine after completion of the drilling. An injection hole with a controllable valve may be provided at the tip.

Next, if necessary, the insides of the perforated steel pipe 4 </ b> A and the freezing pipe 4 </ b> B are cleaned, and the injection means 8 is inserted from the existing tunnel tip 3. And the injection | pouring means 8 is moved to the vicinity of the injection hole 4a of the front end side, the injection material 9 is inject | poured toward the non-springy ground 1 from the injection hole 4a, and the improved body 6 is created (FIG.3 (c)). reference). Then, the injection means 8 is implanted in the same manner at the position of the injection hole 4a which is adjacent to move the existing tunnel tip 3 side, to construct a modified body 6 along the longitudinal direction of the section L _1.
This process is sequentially or simultaneously performed with respect to the perforated steel tube 4A of all the sections L ₁ which is Da設arched.

In the present embodiment, the injection means 8 used in this step constitutes a double-pipe double packer in a state of being inserted into the perforated steel pipe 4A. The schematic configuration inside the perforated steel pipe 4A is the packers 8a and 8b. And the inner tube 8c. In addition, although not shown, a moving mechanism for moving them in the pipe member, an injection material feeding device, and the like are provided on the tip side of the existing tunnel.
The packers 8a and 8b are provided in parallel at a predetermined distance so that the injection hole 4a can be sandwiched therebetween, and are in fluid-tight sliding contact with the inner diameter portion of the perforated steel pipe 4A. It is a member that forms an inner chamber 20 that is a space surrounded by the perforated steel pipe 4A.
The inner pipe 8c forms a pipe line for feeding the injection material 9 supplied from the injection material pumping device. The inner pipe 8c is connected to the packer 8a and closed, and the packer 8b passes through the intermediate portion of the packer 8b. And extend to the existing tunnel tip 3 through the perforated steel pipe 4A and the freezing pipe 4B.
A discharge port 8d for discharging the injection material 9 is provided in the inner chamber 20 of the inner tube 8c.
An appropriate ground improvement material can be used for the injection material 9 in accordance with the soil quality of the non-springy ground 1 and the required strength. For example, cement-based or urethane-based injection materials can be used.

With such a configuration, the injection means 8 can be freely installed while the packers 8a and 8b and the inner pipe 8c are integrated, and the inner diameter portions of the perforated steel pipe 4A and the freezing pipe 4B are slidably brought into contact with each other by the moving mechanism to maintain liquid tightness. Can move.
For this reason, at the position where the injection means 8 is fixed, the injection material 9 pumped through the inner tube 8c is discharged from the discharge port 8d into the inner chamber 20, and is injected into the non-spring ground 1 through the injection hole 4a. The injection material 9 injected into the non-spring ground 1 penetrates into the non-spring base 1 according to the injection pressure, and the improved body 6 is created.
Since this injection means 8 performs partial injection because of a double pipe double packer system, there is an advantage that the injection pressure can be easily controlled even if the perforated steel pipe 4A is long.
Further, the injection amount, the type of the injection material 9 and the like can be varied along the longitudinal direction of the perforated steel pipe 4A. If it does so, there exists an advantage that it becomes possible to produce the quality improvement body 6 according to the change, for example, when soil quality etc. change along the longitudinal direction of the perforated steel pipe 4A.

Next, in the pre-freezing treatment step, first, in order to prevent the injection material 9 or the like from being mixed into the coolant 15 to deteriorate the cooling efficiency or obstruct the coolant circulation, the freezing tube is used in the previous step as necessary. 4B, the injection material 9 remaining in the perforated steel pipe 4A is washed and removed.
Then, in order to make the inside of the freezing tube 4B a closed space in the next step, as shown in FIG. 10 is filled to close the rear end portion of the perforated steel pipe 4A or the front end portion of the freezing tube 4B.
Here, the filling material 10 may be filled by introducing the filling device after removing the injection means 8 once, or provided with a controllable discharge port in front of the injection means 8. Can be filled by the injection means 8.
Alternatively, the injection means 8 may be closed by leaving it in the steel pipe, and only the inner pipe 8c behind the packer 8b may be removed.

Next, in the freezing step, as shown in FIG. 4 (e), the freezing device 11 (freezing means) is introduced from the tip side of the existing tunnel, the range of the freezing tube 4B is cooled, and the spring around the freezing tube 4B is The aqueous ground 2 is frozen to form a layer of frozen soil 7.
Since the roof is formed by the plurality of frozen tubes 4B covered with the frozen soil 7 by this process, the frozen tube 4B and the frozen ground are integrated with each other to exert strength and stabilize the top, and the frozen soil. Since the groundwater above 7 cannot permeate below the frozen soil 7, spring water below the freezing pipe 4 </ b> B can be prevented.
It is preferable that the springy ground 2 has a high freezing strength if it is sandy soil. However, even if it is a viscous soil, it is sufficient to appropriately set the arrangement pitch of the freezing pipe 4B, the freezing range, etc. Freezing strength can be expected.

  The schematic configuration of the in-pipe introduction portion of the refrigeration apparatus 11 used in this step includes a packer 12, an inner pipe 13A (coolant flow path), an inner pipe 13B (coolant flow path), and a heat insulating material 14 (heat insulating member). In addition, although not shown, a moving mechanism and a coolant circulation mechanism for moving them as necessary are provided on the tip side of the existing tunnel.

  The packer 12 forms a closed space between the filler 10 and the inner surface of the freezing tube 4B by liquid-tight sliding contact with the inner diameter portion of the freezing tube 4B, and a holding member that forms a space in which the coolant 15 circulates. It is. A pressure type packer or a mechanical type packer may be used as long as it is made of a cold-resistant material having a sufficient sealing property even below freezing point.

The inner pipes 13A and 13B are metal pipes that pass through and are fixed to the middle part of the packer 12 and can be inserted into the perforated steel pipe 4A and the frozen pipe 4B. For example, an SGP steel pipe having an appropriate diameter can be employed. In either case, one of the open ends extends into the inside of the freezing pipe 4B, and the other open end is connected to a coolant circulation mechanism (not shown) to form a circulation channel of the coolant 15.
The tip of the inner pipe 13A on the side of sending the coolant 15 into the freezing pipe 4B is arranged in the vicinity of the filler 10, and the tip of the return side inner pipe 13B for collecting the coolant 15 inside the freezing pipe 4B is , Provided near the packer 12.
By arranging in this way, the coolant 15 is sent out toward the wall formed by the filler 10 as shown by the arrows in the figure, and radially extends along the wall to the inner peripheral surface of the freezing tube 4B. On the other hand, an efficient steady flow that flows in the longitudinal direction of the freezing tube 4B along the inner peripheral surface of the freezing tube 4B and is sucked into the tip opening of the inner tube 13B can be formed.

As shown in FIGS. 4E and 4F, the heat insulating material 14 covers the entire outer circumference of the inner pipes 13A and 13B extending from the packer 12 toward the tip of the existing tunnel in the longitudinal direction, and has a perforated steel pipe 4A and the like. It is a member for heat insulation. Any material can be used as the heat insulating material 14 as long as it can be used at a low temperature below freezing point. For example, a heat insulating material made of polyurethane foam can be used.
As the coolant 15, for example, an antifreeze (brine) or the like can be suitably employed.

  By introducing this refrigeration apparatus 11 into the freezing pipe 4B and carrying out this process, it can be constructed through the perforated steel pipe 4A from the existing tunnel tip 3 in the same manner as the improved body formation process. As a countermeasure, it is possible to perform continuous and efficient construction in the tunnel without newly drilling holes or performing construction from the ground.

After completion of the freezing process, the coolant 15 in the freezing pipe 4B is collected, and the freezing device 11 is removed to the existing tunnel tip 3 side. And the injection | pouring means 8 is introduce | transduced into the perforated steel pipe 4A connected to the freezing pipe 4B, and an improved body formation process is performed from the front end side of this perforated steel pipe 4A. At this time, since the freezing tube 4B has sufficient strength due to the freezing strength with the frozen soil 7 covering the periphery, it is not necessary to fill the inside of the freezing tube 4B with a filler for reinforcement or water stop.
Therefore, the injection to the front of the perforated steel pipe 4A is omitted, and the injection starts from the injection hole 4a.
Thus, the tunnel tip receiving construction method according to the present embodiment is completed by performing the improved body creation process up to the existing tunnel tip 3.
Then, the improved body 6 and the frozen soil 7 provided as described above are excavated in the tunnel 5 at a timing at which sufficient strength is developed, so that the top stability measures and the spring measures are taken and the safety is taken. The tunnel excavation can proceed.

  In addition, in this embodiment, as shown in FIG. 1, although demonstrated in the example which encounters the springy ground 2 only at one place, when encountering the springy ground 2 and multiple places, according to the area | region, It goes without saying that the above-described improved body creation step, pre-freezing treatment step, and freezing step are repeated.

Next, a modification of this embodiment will be described.
FIG. 5 is a cross-sectional explanatory diagram for explaining a freezing step of the tunnel tip receiving method according to a modification of the embodiment of the present invention.
In this modification, a refrigeration apparatus 16 (refrigeration means) is used in place of the refrigeration apparatus 11 in the freezing step of the above embodiment.
The refrigeration device 16 is a cylindrical shape that can be inserted close to the inner surface of the freezing tube 4B instead of the packer 12 of the refrigeration device 11, and includes a heat absorption unit 17 that holds the coolant 15 in a liquid-tight state. The inner tubes 13A and 13B are inserted and fixed to the bottom of the 17 cylinders. The inner pipes 13 </ b> A and 13 </ b> B extending from the heat absorption unit 17 to the existing tunnel tip end side are covered with the heat insulating material 14 in the same manner as the refrigeration apparatus 11.
The endothermic unit 17 is made of a metal having good thermal conductivity.
With such a configuration, the coolant 15 can be circulated inside the heat absorption unit 17 to absorb heat from the surface of the heat absorption unit 17. Therefore, by disposing the heat absorption unit 17 at an appropriate position of the freezing tube 4B and continuing the heat absorption, the freezing tube 4B and its surroundings can be frozen. And if the heat absorption unit 17 is moved, the freezing range can be moved. Moreover, since the coolant 15 is sealed in the heat absorption unit 17, the trouble of removing the coolant 15 after removing the refrigeration apparatus 16 can be saved.

Each step according to this modification will be described focusing on differences from the above embodiment.
First, the pipe member placing step and the improved body forming step are performed in the same manner as described above.
In the pre-freezing treatment step, the freezing tube 4B and the injection material 9 remaining in the perforated steel tube 4A in the previous step are only washed and removed in the previous step, and the clogging with the filler 10 is not performed.
Since there is no fear that the remaining injection material 9 is mixed into the coolant 15 by the heat absorption unit 17, it is sufficient to clean and remove the injection material 9 to such an extent that the heat absorption unit 17 can be moved and installed.
The periphery of the heat absorption unit 17 may be covered with air or water. However, if the freezing tube 4B and the heat absorption unit 17 are integrated, it is advantageous in terms of thermal conductivity and strength. In this case, it is preferable to provide a grout tube so that grout can be injected from the outer peripheral surface of the heat absorption unit 17.

In the freezing step, the endothermic unit 17 is installed at a predetermined position, and the coolant 15 is circulated to perform freezing. By providing the endothermic unit 17 over the entire length of the freezing tube 4B, the range can be frozen simultaneously.
After the completion of freezing, the coolant 15 is collected and the refrigeration apparatus 16 is removed, or only the endothermic unit 17 is left, and the next improved body formation process is performed.

  According to this modification, installation of the refrigeration apparatus 16 becomes easy. In addition, since the coolant 15 is circulated in the heat absorption unit 17, stable circulation can be performed at all times, so that efficient cooling can be performed. Further, since the coolant 15 can be easily collected and no cleaning process is required, it is possible to quickly switch to the next process.

In the above description, the pipe member is described as an example in which the injection pipe and the freezing pipe are replaced with each other. However, if the improved body formation process and the freezing process can be performed through the pipe member, one kind of pipe member is provided. May be used.
For example, a valve that opens and closes according to pressure or temperature is provided in the injection hole, and is pushed open by the injection material in the improved body formation process, and in the freezing process, it does not leak out of the pipe member due to the pressure or temperature of the coolant. If it becomes, the pipe member which provided the injection hole can be used for the area | region of the spring ground 2. FIG.
In this case, since only one type of pipe member is required, the construction is simple, and there is an advantage that the range in which the improved body creation process and the freezing process are performed can be changed after the pipe member is placed.
Further, in the case of adopting the above-described modified heat absorption unit as the cooling means, since the coolant does not leak to the outside, any pipe member having an injection hole can be used.

  In the above description, the spring ground has been described as an example in which only the freezing process is performed. However, if there is no hindrance to the freezing process, the pipe member may be used as necessary, for example, for measures to stabilize the top. Injection may be performed between the ground and the natural ground. In this case, it goes without saying that a pipe member having an injection hole is placed in the region of the spring ground.

In the above description, the example in which the freezing pipe is a steel pipe has been described. However, if there is no problem in cost and strength, another metal pipe, for example, a metal pipe having higher thermal conductivity may be adopted. .
Moreover, if it does not become a hindrance of placement, it is good also as a pipe member which has additional shapes, such as a heat radiating fin, for example in an outer peripheral part.
In any case, since it can cool effectively, construction efficiency can be improved.

It is sectional drawing along the tunnel extension direction which shows typically the mode in front of the tunnel face under construction by the tunnel tip receiving method which concerns on embodiment of this invention. It is AA and BB sectional drawing in FIG. It is sectional explanatory drawing in alignment with the tunnel extension direction for demonstrating sequentially each process of the tunnel tip receiving method which concerns on embodiment of this invention. FIG. 4 is a cross-sectional explanatory diagram for explaining a process following FIG. 3. It is sectional explanatory drawing for demonstrating the freezing process of the tunnel tip receiving method which concerns on the modification of embodiment of this invention.

Explanation of symbols

1 Non-springy ground 2 Springy ground 4A Perforated steel pipe (injection pipe)
4B Freezing pipe 4a Injection hole 4b Connection part 6 Improved body 7 Frozen earth 8 Injection means 8a, 8b, 12 Packer 8c Inner pipe 9 Injection material 10 Filling materials 11, 16 Refrigeration apparatus (freezing means)
13A, 13B Inner pipe (coolant flow path)
14 Heat insulation material (heat insulation material)
15 Coolant 17 Endothermic unit

Claims (5)

A tunnel tip receiving method in which a pipe member is inserted in the vicinity of a tunnel excavation region, an injection material for ground improvement is injected into the ground from the side of the pipe member, and the top end is stabilized.
In a natural ground region where the ground into which the pipe member is inserted is a springy ground, instead of injecting the injection material, a freezing means for freezing the ground is inserted into the pipe member to freeze the ground. A unique tunnel tip receiving method. When inserting the pipe member into the ground, an injection pipe provided with an injection hole for the injection material on the side part and the injection hole provided on the side part according to the spring water of the ground at the installation position of the pipe member. Selectively insert and replace the freezing tube,
In order from the distal end side, the injection material is injected into the ground for the area where the injection pipe is arranged, and the ground is frozen by the freezing means for the area where the freezing pipe is arranged. The tunnel tip receiving method according to claim 1, wherein:   The said freezing means is provided with the coolant flow path which circulates a coolant in the said freezing pipe, and the heat insulation member which heat-insulates this coolant flow path with respect to said pipe members other than the said freezing pipe. Item 3. Tunnel receiving method according to item 2.   The refrigeration means includes an endothermic unit in which a coolant circulates inside and is movable within the tube member, a coolant channel for circulating the coolant in the endothermic unit, and the coolant channel The tunnel tip receiving method according to claim 1, further comprising a heat insulating member that insulates the pipe member.   The tunnel tip receiving method according to any one of claims 1 to 3, wherein at least a rear end side of the pipe member into which the injection material is injected is closed with a filler prior to insertion of the refrigeration means.

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