JP6775414B2 - Ground excavation method - Google Patents

Description

The present invention relates to a ground excavation method for excavating the ground with an excavation machine such as a shield excavator.

When excavating aquifer containing groundwater or ground containing a soft layer with an excavation machine such as a shield excavator, a freezing method may be used to freeze a part of the ground to stop water or strengthen the ground.

As a ground excavation method using the freezing method, the ground excavation method (tunnel excavation method) described in Patent Document 1 is known. In this ground excavation method, a freezing medium is injected into the ground through a freezing pipe inserted into the gravel ground of the ground to freeze the ground, and then the freezing pipe is pulled out from the ground, and in this state, the frozen ground is frozen. Is being excavated by a shield excavator. This prevents or suppresses the collapse of the face surface during excavation and the inflow of groundwater into the shield excavator.

JP-A-2009-293205

However, in the ground excavation method described in Patent Document 1, the frozen pipe must be pulled out before the frozen ground is excavated by the shield excavator, and the pulling out work is troublesome. In addition, when it is difficult to pull out the frozen pipe when the ground is frozen, it is thawed to pull out the frozen pipe, so when actually excavating the ground, a part of the frozen ground is thawed. There is a possibility that the frozen ground cannot be constructed in an appropriate range.

The present invention has been made by paying attention to such a problem, and provides a ground excavation method capable of reducing work man-hours and excavating with frozen ground constructed in an appropriate range. The purpose is to do.

In response to the above problems, the tunnel excavation method according to the present invention is one aspect of the ground excavation method of excavating the ground with an excavation machine, in which the excavation machine cuts into a predetermined area of the planned excavation area of the ground. A pipe arranging step of arranging possible pipes for excavation, a freezing step of flowing a refrigerant through the pipes to freeze the ground in the predetermined region, and freezing the predetermined region of the planned excavation region. The configuration includes an excavation step of excavating with the excavation machine in a state where the pipe for the refrigerant flow is left in the predetermined region after the step.

According to the above aspect of the ground excavation method according to the present invention, prior to excavation by the excavation machine, an excavation machine is used in a predetermined area (for example, an aquifer layer containing groundwater or a soft layer) in the planned excavation area. A cuttable pipe for flowing a refrigerant is arranged, and a refrigerant is circulated through the pipe to freeze the ground in the predetermined region, and then the predetermined region is excavated with the pipe for flowing the refrigerant left.
In this way, by making the pipe for the refrigerant flow cuttable by the excavation machine, the pipe for the refrigerant flow can be cut together with the ground in the predetermined area. Therefore, before excavation by the excavation machine, Compared with the conventional excavation method that requires the extraction work of the freezing pipe (piping for the flow of refrigerant), the work manpower can be reduced. Further, since the drawing work is not required, for example, it is not necessary to pour hot water or the like through the refrigerant flow pipe for drawing to thaw. As a result, frozen ground can be constructed in an appropriate range.

In this way, it is possible to provide a ground excavation method capable of reducing the work man-hours and excavating with the frozen ground constructed in an appropriate range.

It is sectional drawing of the ground of the tunnel construction area to which the ground excavation method of 1st Embodiment which concerns on this invention is applied. It is a drawing for demonstrating the pipe arrangement process in the said ground excavation method. It is sectional drawing of the freezing pipe arranged in the said pipe arrangement process. It is a drawing for demonstrating the freezing process of a predetermined area in the said ground excavation method. It is a drawing for demonstrating the process of forming the wellhead for starting a shield excavator in the said ground excavation method. It is a partially enlarged view of the entrance packing provided in the wellhead. It is a partially enlarged view which showed the state which the front part of the shield excavator entered into the well mouth. It is a drawing for demonstrating the excavation process in the said ground excavation method. It is a figure which showed the excavation state of the predetermined area in the excavation process. It is a figure which showed the filling state of the backfill material in the excavation process. It is a figure which showed the state which performed the remaining excavation while constructing a segment ring through the predetermined area. It is a figure for demonstrating the ground excavation method of the 2nd Embodiment which concerns on this invention. It is a figure for demonstrating the ground excavation method of the 3rd Embodiment which concerns on this invention.

Hereinafter, an embodiment of the ground excavation method according to the present invention will be described with reference to the accompanying drawings, taking as an example a case where the ground excavation method is applied to a tunnel construction area.

FIG. 1 is a cross-sectional view of the ground in a tunnel construction area to which the ground excavation method of the first embodiment according to the present invention is applied, and is a columnar excavation planned area A0 of a shield excavator 1 as an excavation machine and each layer of the ground. It is a figure which showed the positional relationship with.

As shown in FIG. 1, the ground of the tunnel construction area on the starting side of the shield excavator 1 in the present embodiment is an aquifer (for example, a sand layer or a gravel layer) G1 containing groundwater and a lower part of the aquifer G1. It is assumed that the mudstone layer G2 adjacent to the above is included. The shield excavator 1 is arranged on the bottom surface side in the starting shaft 2 for starting, and is excavated in the horizontal direction toward, for example, the reaching shaft or the slope of the ground, which is not shown. The starting shaft 2 is made of, for example, reinforced concrete, has a cylindrical peripheral wall 2a and a bottom wall 2b that closes the lower end of the peripheral wall 2a, and is formed in a bottomed tubular shape with an open upper end, and is formed on the ground surface side. It is arranged so as to extend in the vertical direction from. In FIG. 1, the alternate long and short dash line indicates the outer trajectory of the shield excavator 1 during excavation. The planned excavation area A0 of the shield excavator 1 refers to a columnar area surrounded by this outer trajectory (dashed line) and the peripheral wall 2a of the shaft 2 for starting. In the present embodiment, the area of the planned excavation area A0 near the starting shaft 2 is located in the aquifer G1, and the area of the planned excavation area A0 such as the reaching shaft is not shown. For example, it is assumed that it is located in the mudstone layer.

Here, if the aquifer G1 exists in the region near the starting shaft 2 of the shield excavator 1, groundwater and earth and sand form on the peripheral wall 2a of the starting shaft 2 for starting wellhead 2c (see FIG. 5 described later). There is a possibility that it will flow into the starting shaft 2 via. On the other hand, in the present embodiment, on the reaching side, for example, it is located in a mudstone layer that is neither an aquifer nor a soft layer, and it is considered that there is little need to take measures against water stoppage and sediment inflow, and only on the starting side. The above measures shall be taken.

The ground excavation method in the present embodiment is a method of excavating the ground with a shield excavator 1, and includes a pipe arrangement process, a freezing process, a wellhead formation process, and an excavation process, and includes a water stoppage and a start shaft 2 for earth and sand. It is configured to prevent inflow to the inside.

In the following, each step will be described with reference to FIGS. 2 to 11. 2, FIG. 4, FIG. 5, and FIGS. 8 to 11 are diagrams for explaining the procedure of the ground excavation method of the present embodiment. FIG. 3 is a cross-sectional view of the freezing pipe 3 in the arrow view of BB shown in FIG. 2, and FIG. 6 is a partially enlarged view of the entrance packing 4 provided at the starting wellhead 2c (see FIG. 5). Is a partially enlarged view showing a state in which the shield excavator 1 has entered from the wellhead 2c. Specifically, FIG. 2 shows the pipe arrangement process, FIG. 4 shows the freezing process, FIG. 5 shows the wellhead forming process, and FIGS. 8 to 11 show the excavation process.

In the pipe arranging step, as shown in FIG. 2, the freezing pipe 3 is arranged in a predetermined area A1 of the planned excavation area A0 of the ground. In the present embodiment, the predetermined region A1 is a region in the vicinity of the starting shaft 2. The predetermined region A1 is specifically a region set so as to cover the starting wellhead 2c (see FIG. 5) of the shield excavator 1 formed on the peripheral wall 2a of the starting shaft 2 from the outside of the peripheral wall 2a. In other words, this predetermined region A1 is a region generally set as a region to be frozen in the freezing step, and does not indicate a region in which the range is strictly set. In the freezing step, the ground inside the predetermined region A1 is surely frozen, and even if the region is outside the predetermined region A1, the ground near the predetermined region A1 can be partially frozen.

The freezing pipe 3 is a pipe for refrigerant flow that can be cut by the shield excavator 1, and is formed to have an appropriate cross-sectional shape. In the present embodiment, as shown in FIG. 3, the freezing tube 3 is formed so as to have a flat cross-sectional shape and extend in one direction (vertical direction), for example. The freezing pipe 3 is formed by, for example, extrusion molding of a mild steel material such as aluminum or copper, and passages (supply passage 3a and return passage 3b described later) are formed inside a flat prism. Further, the freezing pipe 3 is arranged in the ground so that, for example, the long side L1 of its cross section extends in the digging direction of the shield digging machine 1. As will be described later, when liquefied carbon dioxide is used as the refrigerant, the viscosity of the liquefied carbon dioxide is significantly lower than that of brine such as sodium chloride, so that the resistance when flowing through the freezing tube 3 is extremely small as compared with brine. Therefore, the cross-sectional area of the passage in the freezing tube 3 can be made much smaller than that in the case of using brine, so that the freezing tube 3 can be formed by a flat member as shown in FIG. For example, the length of the long side L1 of the freezing tube 3 can be about 50 mm, and the length of the short side L2 of the freezing tube 3 can be about 5 mm. In each figure, the freezing tube 3 is exaggerated and shown larger than the actual size for the sake of clarity of the figure.

Further, in the present embodiment, the freezing pipe 3 recirculates the refrigerant supplied from the refrigerant supply device 10 arranged on the ground side to the refrigerant supply device 10 and the supply passage 3a flowing through the supply passage 3a. It has a return passage 3b. Specifically, an appropriate number of supply passages 3a and return passages 3b (five in the figure) are formed inside the freezing pipe 3, and each passage (supply passage 3a) is formed inside the freezing pipe 3. , The return passage 3b) is partitioned so as to extend in parallel with a distance from each other. Further, as shown in FIG. 2, an upper end lid 3c is attached to the upper end side (ground surface side end portion) of the freezing pipe 3, and a refrigerant supply pipe from the refrigerant supply device 10 is attached to the upper end lid 3c. 10a is connected, and the refrigerant return pipe 10b to the refrigerant supply device 10 is connected. The inside of the upper end lid 3c is divided into a region communicating with the plurality of supply passages 3a and a region communicating with the plurality of return passages 3b. A lower end lid 3d is attached to the lower end side (underground side end portion) of the freezing pipe 3, and the inside of the lower end lid 3d is a region communicating with a plurality of supply passages 3a like the upper end lid 3c. And a region communicating with the plurality of return passages 3b.

The refrigerant supply device 10 includes, for example, a pump for pumping the refrigerant (not shown) and a cooling device for cooling the refrigerant (not shown). The refrigerant supply device 10 pumps the refrigerant cooled by the cooling device by the pump and supplies it to the freezing pipe 3 via the refrigerant supply pipe 10a, and the temperature-raised refrigerant is supplied from the freezing pipe 3 through the refrigerant return pipe 10b. It is a cooling circulation device for a refrigerant, which is configured to return the refrigerant to the cooling device for cooling, and then pump it again by the pump. As the refrigerant to be circulated, for example, an appropriate refrigerant such as liquefied carbon dioxide or brine such as sodium chloride can be used, and in this embodiment, liquefied carbon dioxide is used.

Further, in the present embodiment, in the pipe arranging step, the guide pipe 5 having an inner diameter larger than the outer diameter of the freezing pipe 3 is arranged in the predetermined region A1, and the freezing pipe 3 is arranged in the guide pipe 5. The guide pipe 5 prevents the hole wall of the hole BH for inserting the freezing pipe 3 into the ground from collapsing, and is arranged so that the lower end thereof is located at the lower end of the predetermined region A1. Then, the space S between the inner wall of the guide tube 5 and the outer wall of the freezing tube 3 is filled with an appropriate heat conductive medium 6 having a relatively high thermal conductivity. Specifically, as the heat conductive medium 6, for example, cement bentonite appropriately blended is used. The heat conductive medium 6 made of cement bentonite is poured into the space S so that the liquid level when the filling is completed coincides with the height position of the upper end of the predetermined region A1. Therefore, the region from the ground surface to the upper end of the predetermined region A1 (the upper end of the heat conductive medium 6) is not filled with the heat conductive medium 6, and only the atmosphere (air) is present. A simple heat insulating layer is formed on the outer periphery of the freezing tube 3 above the predetermined region A1.

In the freezing step, as shown in FIG. 4, a refrigerant is circulated through the freezing pipe 3 to freeze the ground in the predetermined region A1 (in the figure, the shaded portion indicates the frozen region). That is, when the liquefied carbon dioxide sent from the refrigerant supply device 10 flows through the plurality of supply passages 3a in the freezing pipe 3, the latent heat of vaporization when the liquefied carbon dioxide absorbs the heat in the ground and vaporizes is used. By doing so, the ground is frozen. In the present embodiment, cement bentonite is filled between the freezing tube 3 and the guide tube 5 as the heat conductive medium 6 corresponding to the height position of the predetermined region A1, and the heat conductive medium 6 is used to connect to the ground. Heat exchange with the refrigerant in the freezing pipe 3 is efficiently performed, and the ground in the predetermined region A1 is frozen. On the other hand, above the predetermined region A1, since the heat insulating layer exists between the freezing pipe 3 and the guide pipe 5 (between the refrigerant and the ground), heat exchange between the ground and the refrigerant in the freezing pipe 3 Is rarely performed, and the ground above the predetermined area A1 is hardly frozen.

Here, the height h in the vertical direction of the predetermined area A1 is set to be at least larger than the opening diameter of the wellhead 2c, and the thickness t in the horizontal direction of the portion to be dug by the shield excavator 1 in the predetermined area A1 is , The length of the excavator main body 1b including the cutter head 1a of the shield excavator 1 is set to be approximately ½ of the total length L (that is, t> about 0.5 L). In the present embodiment, the thickness t of the predetermined region A1 is set to be the same as the total length L of the main body, for example. The height h and thickness t of the predetermined region A1 are the circulation time and the circulation amount of the refrigerant in the freezing step, depending on the outer diameter of the shield excavator 1, the total length L of the main body, the groundwater pressure and the earth pressure of the aquifer G1 and the like. It can be set appropriately by adjusting the above. Further, in the present embodiment, it is shown that one freezing tube 3 is arranged, but when the volume of the region to be frozen becomes relatively large and the predetermined region A1 becomes a wide area, a plurality of freezing tubes 3 are frozen. The tube 3 may be arranged.

In the wellhead forming step, as shown in FIG. 5, a wellhead 2c for starting the shield excavator 1 is formed on the peripheral wall 2a of the starting shaft 2. The wellhead 2c is formed after the completion of the freezing step and has an opening larger than the outer diameter of the shield excavator 1. As shown in FIGS. 5 and 6, an entrance packing 4 is attached to the peripheral edge of the wellhead 2c on the inner peripheral surface side of the peripheral wall 2a. The entrance packing 4 is provided between the wellhead 2c of the starting shaft 2 and the outer circumference of the shield excavator 1 (see FIGS. 7 and 8) and between the wellhead 2c of the starting shaft 2 and the segment ring 7 described later. It is a packing device installed for the purpose of preventing or suppressing the infiltration of groundwater and earth and sand into the inside of the starting shaft 2 through the gap (see FIG. 9). Note that FIG. 7 shows a state in which the shield excavator 1 is in contact with the entrance packing 4, and at this time, the entrance packing 4 bends while being in contact with the shield excavator 1. In this way, the shield excavator 1 is arranged at the wellhead 2c of the starting shaft 2 and proceeds to the excavation process.

In the excavation process, as shown in FIGS. 8 to 11, for the predetermined area A1 of the planned excavation area A0, the shield excavator 1 is left in the predetermined area A1 after the freezing process. The area other than the predetermined area A1 in the planned excavation area A0 is excavated as it is by the shield excavator 1 without freezing.

Specifically, the freezing step is completed before the wellhead 2c is formed on the peripheral wall 2a of the starting shaft 2, and after the wellhead 2c is formed, the shield excavator 1 is made to enter from the wellhead 2c to start the excavation process. Then, after arranging the front portion of the shield excavator 1 in the wellhead 2c, and before the cutter head 1a as the tip portion of the shield excavator 1 reaches the guide pipe 5, as shown in FIG. 8, the guide pipe 5 Is pulled up to a place where the lower end thereof is located at the upper end of the predetermined area A1. The guide tube 5 may be completely pulled out, but when the heat conductive medium 6 made of cement bentonite is filled only at the height position corresponding to the predetermined region A1 as in the present embodiment, in the freezing step. In order to surely prevent the hole wall from collapsing, the guide pipe 5 may be maintained in a state of being pulled up to a position where the lower end portion thereof is located at the upper end portion of the predetermined region A1. After the freezing step is completed, the freezing pipe 3 may be left in the ground as it is, and the guide pipe 5 may be completely pulled out, or the portion discharged from the ground surface may be cut and together with the freezing pipe 3. It may be left in the ground. When the guide pipe 5 is completely pulled out, earth and sand are backfilled between the hole wall and the freezing pipe 3, and when the guide pipe 5 is also left, the earth and sand are filled in the space S between the guide pipe 5 and the freezing pipe 3. Etc. are backfilled.

Although not shown here, for example, a reaction force pedestal is arranged between the rear end portion of the shield excavator 1 and the peripheral wall 2a facing the rear end portion, and the reaction force pedestal is interposed through the reaction force pedestal. Then, the reaction force is taken from the starting shaft 2 to start the shield excavator 1. Note that the refrigerant is supplied from the refrigerant supply device 10 until, for example, just before the shield excavator 1 reaches the freezing pipe 3, that is, when the pump of the refrigerant supply device 10 is stopped immediately before reaching the freezing pipe 3. Good. However, the present invention is not limited to this, and when liquefied carbon dioxide is used as the refrigerant as in the present embodiment, the refrigerant may be supplied until, for example, the shield excavator 1 penetrates the predetermined region A1.

FIG. 9 shows a state in which the shield excavator 1 further excavates from the state of FIG. 8, and shows a state immediately before the cutter head 1a penetrates the predetermined region A1. Therefore, in this state, the wellhead 2c is still reliably covered by the frozen ground. Then, in the present embodiment, before the shield excavator 1 penetrates the predetermined area A1, the rear portion of the excavator main body 1b of the shield excavator 1 is composed of a plurality of segments and is smaller than the outer diameter of the excavator main body 1b. Assemble a cylindrical segment ring 7 having a diameter. In the present embodiment, in the state shown in FIG. 9, the rear end (the end opposite to the excavation direction) of the first segment ring 7 is located in the wellhead 2c, and the entrance packing 4 is located on the outer periphery of the segment ring 7. Are in contact. Here, in the state of FIG. 9, when the excavation machine main body 1b begins to penetrate the predetermined region A1 by further advancing the excavation as it is, water and earth and sand in the aquifer G1 will flow from the penetrating portion of the excavator main body 1b. It can flow into the region between the segment ring 7 and the wellhead 2c via (a slight gap) between the outer circumference and the excavated inner surface S1 (see FIG. 10) of the excavated ground, but in this case. However, the start shaft 2 and the shield excavator 1 are provided by the entrance packing 4 and the tail seal 8 that seals between the rear end of the cylindrical skin plate forming the outer shell of the excavator body 1b and the segment ring 7. The inflow of water and earth and sand into the interior is prevented or suppressed.
In addition, in order to surely prevent the inflow of water or the like into the starting shaft 2 and the shield excavator 1, before the shield excavator 1 penetrates the predetermined area A1 in the excavation process, for example, as shown in FIG. In addition, the backfill material 9 may be filled in the space formed by the inner peripheral surface of the wellhead 2c, the surface of the entrance packing 4, the outer peripheral surface of the segment ring 7, and the outer peripheral surface of the excavator main body 1b. ..

Next, the shield excavator 1 penetrates the predetermined area A1, and as shown in FIG. 11, while further excavating the area other than the predetermined area A1 in the planned excavation area A0, one after another behind the shield excavator 1. By assembling the segment ring 7 and connecting it in the excavation direction, and filling the backfill material 9'between the segment ring 7 and the excavation inner surface S1, the tubular lining body is omitted from the drawing. Build toward the slope of the ground. This completes the tunnel construction.

According to the ground excavation method of the present embodiment, prior to excavation by the shield excavator 1, a freezing pipe 3 that can be cut by the shield excavator 1 is arranged in a predetermined area A1 of the planned excavation area A0, and the freezing is performed. A refrigerant is circulated through the pipe 3 to freeze the ground in the predetermined region A1, and then the predetermined region A1 is excavated with the freezing pipe 3 left behind. Since the freezing pipe 3 can be cut by the shield excavator 1 in this way, the freezing pipe 3 can be cut together with the ground in the predetermined area A1 before excavation by the shield excavator 1. Compared with the conventional excavation method that requires the work of pulling out the freezing pipe, the work man-hours can be reduced. Further, since the pulling operation is not required, it is not necessary to pour hot water or the like through the freezing tube 3 for pulling, for example, to thaw. As a result, frozen ground can be constructed in an appropriate range.
In this way, it is possible to provide a ground excavation method capable of reducing the work man-hours and excavating with the frozen ground constructed in an appropriate range.

Further, in the present embodiment, the pump of the refrigerant supply device 10 is stopped immediately before the shield excavator 1 reaches the freezing pipe 3. As a result, natural thawing of the predetermined region A1 due to the stop of the pump can be prevented until just before the cutting of the freezing pipe 3, so that the predetermined region A1 can be excavated with the frozen ground constructed in a more appropriate range.

Further, in the present embodiment, in the pipe arranging step, a guide pipe 5 having an inner diameter larger than the outer diameter of the freezing pipe 3 is arranged in a predetermined region A1, the freezing pipe 3 is arranged in the guide pipe 5, and a guide is provided. A heat conductive medium 6 made of cement bentonite was filled between the inner wall of the pipe 5 and the outer wall of the freezing pipe 3. As a result, it is possible to easily stabilize the hole wall of the hole BH (see FIG. 2) of the portion where the guide pipe 5 is pulled up while efficiently exchanging heat between the refrigerant and the ground.

Further, in the present embodiment, in the excavation process, the inner peripheral surface of the wellhead 2c, the surface of the entrance packing 4, the outer peripheral surface of the segment ring 7, and the excavator before the shield excavator 1 penetrates the predetermined area A1. The space formed by the outer peripheral surface of the main body 1b is filled with the backfill material 9, and when the shield excavator 1 penetrates the predetermined area A1 and excavates, the back surface is formed between the segment ring 7 and the excavation inner surface S1. It was configured to be filled with the filling material 9'. As a result, when the groundwater pressure and earth pressure are relatively high and the entrance packing 4 and the tail seal 8 alone cannot sufficiently suppress or prevent the water stoppage and the inflow of earth and sand, they can be reliably suppressed or prevented. it can. If the entrance packing 4 and the tail seal 8 can sufficiently suppress or prevent water stoppage and inflow of earth and sand, it is not necessary to fill the backfill material 9 at the wellhead 2c.

Further, in the present embodiment, it is assumed that the aquifer G1 exists in the region near the starting shaft 2 of the shield excavator 1, and the wellhead 2c for starting the shield excavator 1 is formed on the peripheral wall 2a of the starting shaft 2. Previously, after the freezing process was completed and the wellhead 2c was formed, the shield excavator 1 was made to enter from the wellhead 2c to start the excavation process. As a result, when the peripheral wall 2a of the starting shaft 2 is opened to form the wellhead 2c, it is possible to easily prevent groundwater and earth and sand from flowing into the starting shaft 2 through the wellhead 2c, and it is possible to prevent the groundwater and earth and sand from flowing into the starting shaft 2 on the starting side. Excavation can be done relatively easily.

Further, in the present embodiment, the freezing pipe 3 is assumed to have a flat cross-sectional shape, and the long side L1 of the cross section is arranged in the ground so as to extend in the excavation direction of the shield excavator 1. .. That is, the side surface of the freezing pipe 3 on the short side L2 side faces the cutter head 1a of the shield excavator 1. As a result, the cutting resistance of the shield excavator 1 can be made extremely low, and the freezing pipe 3 can be cut more easily.

In the present embodiment, the case where the aquifer G1 exists only in the vicinity of the starting shaft 2 has been described as an example, but the present invention is not limited to this, and the aquifer G1 exists only in the vicinity of the reaching shaft 20. In some cases.

FIG. 12 is a diagram for explaining the ground excavation method of the second embodiment according to the present invention. In the present embodiment, it is assumed that the aquifer G1 exists only in the vicinity of the reaching shaft 20 for reaching the shield excavator 1, and a configuration different from that of the first embodiment will be described below.
In the present embodiment, the predetermined area A1 is an area in the vicinity of the reaching shaft 20 for reaching the shield excavator 1. The reaching shaft 20 is made of, for example, reinforced concrete, has a cylindrical peripheral wall 20a and a bottom wall 20b that closes the lower end of the peripheral wall 20a, and is formed in a bottomed tubular shape with an open upper end, and is formed on the ground surface side. It is arranged so as to extend in the vertical direction from. The predetermined region A1 is specifically a region set to cover the exit 20c of the shield excavator 1 formed on the peripheral wall 20a of the reaching shaft 20 from the outside of the peripheral wall 20a. For example, the shield excavator 1 is dug toward the reaching shaft 20 from a starting shaft or a slope of a ground (not shown) without freezing the ground in a region other than the predetermined region A1 in the planned excavation region A0. The excavation is carried out as it is, the segment rings 7 are assembled one after another behind the shield excavator 1, and the backfill material 9'is filled between the segment ring 7 and the excavation inner surface S1 in the same manner as in the first embodiment. Then, the freezing step is completed before the wellhead 20c is formed on the peripheral wall 20a of the reaching shaft 20. After that, while excavating the predetermined area A1, the segment ring 7 is assembled and the backfill material 9'is filled. Finally, the tunnel construction is completed by forming the wellhead 20c.

According to the ground excavation method according to the second embodiment, when the peripheral wall 20a of the reaching shaft 20 is opened to form the wellhead 20c, groundwater and earth and sand can easily flow into the reaching shaft 20 through the wellhead 20c. Can be prevented. In addition, the backfill material 9'can more reliably suppress or prevent water stoppage and inflow of earth and sand.
In the second embodiment, before the shield excavator 1 penetrates the predetermined area A1, sufficient water stoppage is provided by the backfill material 9'behind the shield excavator 1. Therefore, the thickness t in the second embodiment may be set so as to be able to withstand the groundwater pressure and the earth pressure of the aquifer G1 regardless of the total length L of the excavator main body 1b. It can be made thinner than the thickness t in the embodiment. When the aquifer G1 exists in both the vicinity of the starting shaft 2 and the vicinity of the reaching shaft 20, the freezing pipe 3 is arranged in each of the predetermined area A1 as the vicinity of the starting shaft 2 and the vicinity of the reaching shaft 20. Then, the frozen ground may be formed, and the ground may be excavated together with the freezing pipe 3 in each predetermined area A1.

Further, in each of the above embodiments, the predetermined region A1 is located in the aquifer G1, but the present invention is not limited to this, and a soft layer may be used. In this case, the guide pipe 5 is not required in the pipe arranging step, and the freezing pipe 3 may be press-fitted into the predetermined region A1 and arranged by pressing the upper end of the freezing pipe 3. Further, when it is difficult to press-fit the freezing tube 3 alone into the predetermined region A1 in the soft layer, or in the water-bearing layer G1, for example, the freezing tube 3 is processed to form a shaped steel having an appropriate cross-sectional shape (H-shaped steel, It may be temporarily fixed to angle steel, channel steel, etc.), press-fitted together with the section steel, and then only the section steel is pulled out from the ground.

Further, a shaft (2, 20) made of reinforced concrete is formed for starting and reaching the shield excavator 1, but the space for starting and reaching is not limited to this, and a space for starting and reaching is provided by a retaining wall made of steel or the like. It may be formed.

Further, in each of the above embodiments, the freezing pipe 3 is arranged so as to extend vertically from the ground surface side, but the present invention is not limited to this, and the freezing pipe 3 may be arranged at an angle.

In each of the above embodiments, the case where the freezing pipe 3 is inserted into the ground from the ground surface side has been described as an example for the purpose of freezing the ground in the vicinity of the starting shaft 2 and the reaching shaft 20. Not limited to this. For example, when the operator goes out of the shield excavator 1 and maintains the front part of the shield excavator 1 such as the cutter head 1a while excavating the ground including a soft layer or the like, the present invention relates to the present invention. As shown in FIG. 13, which is a diagram for explaining the ground excavation method of the third embodiment, the freezing pipe 3 is inserted into the ground from the front part of the shield excavator 1 to the ground in front of the shield excavator 1 and excavated by the shield excavator 1. The front ground including the face surface of the slab may be frozen. Specifically, a plurality of freezing pipes 3 are directly built from the inside of the machine to the outside of the machine through the spokes of the cutter head 1a, and the propulsion center axis of the shield excavator 1 is set as the apex in front of the cutter head 1a. It is advisable to arrange a group of conical (umbrella skeleton) freezing tubes. As a result, as shown by the shaded portion in FIG. 13, the ground in the predetermined area A1 forming the conical outer shell can be frozen, so that the operator can safely set the work space inside the predetermined area A. Can be secured.

Further, although not shown, for example, in a widening work area for widening a part of an underground structure such as an existing tunnel, an aquifer or a soft layer may exist around the planned widening area. In this case, the planned widening area is set as the planned excavation area A0, the circumference of the planned widening area is set as the predetermined area A1, and a plurality of freezing pipes 3 are arranged from the existing underground structure toward the predetermined area A1. You may do so. Specifically, a plurality of freezing pipes 3 were inserted and arranged in a conical shape from the outer periphery of the existing underground structure before and after the planned widening area toward the predetermined area A1 around the planned widening area. The widening area may be surrounded by two groups of freezing tubes from both front and rear sides. As a result, an abacus ball-shaped frozen ground surrounding the planned widening area can be formed. Then, when constructing the widening structure in the planned widening region, the frozen ground can be excavated together with the freezing pipe 3, so that the widening structure can be easily constructed.

Further, the case where the freezing pipe 3 has a supply passage 3a and a return passage 3b and the refrigerant can be circulated has been described as an example, but the present invention is not limited to this, and the inside of the ground without circulating the refrigerant. May be injected directly into. Further, the freezing pipe 3 is assumed to have a passage formed inside a flat prism, but the present invention is not limited to this, and the freezing pipe 3 can be formed into an appropriate shape as long as it can be cut by the shield excavator 1.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and modifications can be made based on the technical idea of the present invention.

1 ... Shield excavator (excavation machine)
2 ... Starting shaft 2a ... Peripheral wall 2c ... Wellhead 3 ... Freezing pipe (piping)
5 ・ ・ ・ ・ ・ Guide tube 6 ・ ・ ・ ・ ・ Cement bentonite (heat conductive medium)
20 ... Reaching shaft 20a ... Peripheral wall 20c ... Wellhead A0 ... Expected excavation area A1 ... Predetermined area S1 ... Excavation inner surface

Claims (3)

In the ground excavation method of excavating the ground with an excavation machine,
A piping arrangement process for arranging a refrigerant flow pipe that can be cut by the excavation machine in a predetermined area of the planned excavation area of the ground.
A freezing step in which a refrigerant is circulated through the pipe to freeze the ground in the predetermined region,
For the predetermined region of the expected excavation area, a drilling step for drilling by the drilling machine in a state of being left behind the front Sharing, ABS pipe to said predetermined area after the freezing step,
Only including,
The pipe has a flat prismatic cross section and is formed so as to extend in one direction.
The pipe arranging step is a ground excavation method in which the pipe is arranged in the ground so that the long side in the cross section of the pipe extends in the excavation direction of the excavating machine . In the ground excavation method of excavating the ground with an excavation machine,
A piping arrangement process for arranging a refrigerant flow pipe that can be cut by the excavation machine in a predetermined area of the planned excavation area of the ground.
A freezing step in which a refrigerant is circulated through the pipe to freeze the ground in the predetermined region,
Regarding the predetermined area of the planned excavation area, an excavation step of excavating with the excavation machine in a state where the pipe is left in the predetermined area after the freezing step.
Including
The pipe has a flat prismatic cross section and is formed so as to extend in one direction.
The pipe arranging step is a ground excavation method in which the pipe is arranged in the ground so that the side surface on the short side side of the pipe faces the cutter head of the excavating machine. The pipe has a supply passage for circulating a refrigerant supplied from a refrigerant supply device arranged on the ground side, and a return passage for returning the refrigerant flowing through the supply passage to the refrigerant supply device, according to claim 1 or ground excavation method described in 2.