JP7085505B2 - Shield excavator and shield method - Google Patents

Description

The present invention relates to a shield excavator and a shield method using the shield excavator.

In tunnel construction by the shield method, the muddy water type shield method or the muddy soil pressure type shield method is generally adopted.
The muddy water type shield method is a method adopted in the ground below the groundwater level and the ground with low permeability, and the pressure of the muddy water supplied into the chamber via the mud transmission pipe is used to reduce the soil water pressure in the surrounding ground. By countering, excavation is performed while ensuring the stability of the face. In the muddy water type shield method, the pressure in the chamber is controlled by the relationship between the pressure of the muddy water supplied through the mud feed pipe and the muddy water pressure (mud drainage amount) discharged through the mud drain pipe.
In addition, the mud pressure type shield method is a method adopted in the ground where the groundwater pressure is low, and the stability of the face is ensured by countering the soil pressure of the surrounding ground by the pressure of the excavated earth and sand taken into the chamber. Excavate in the same state. In the mud pressure type shield method, the excavated earth and sand in the chamber are generally discharged by a screw conveyor, and the pressure in the chamber is controlled by the relationship between the excavated soil amount and the excavated soil amount of the screw conveyor.

When excavating a ground with abundant changes in the ground to be excavated, either the muddy water shield method or the muddy pressure shield method cannot respond to the changes in the ground, making construction difficult. May be. Therefore, as a construction method that can be applied to various soil layers, for example, as shown in Patent Document 1, a shield excavator having the mechanisms of both the muddy water type shield method and the muddy soil pressure type shield method is used. In the shield method using such a shield excavator, when switching from the muddy pressure type to the muddy water type, the earth and sand in the chamber are removed, the muddy water is supplied to the chamber, and the chamber is filled with muddy water. Do digging at. On the other hand, when switching from the muddy water type to the muddy soil pressure type, the chamber is filled with excavated soil by digging while injecting an additive into the chamber while the supply of muddy water to the chamber is stopped.
However, in the ground that is the target of the mud pressure shield method, there is a risk that muddy water will infiltrate the ground (mud). Therefore, when switching from the muddy water type to the muddy soil pressure type, there is a risk that it will not be possible to secure an even pressure on the face due to the mud spillage. Further, when excavation is carried out with the chamber filled with muddy water, the excavated soil is mixed with the muddy water and is difficult to be plastically fluidized, which makes it difficult to control the face pressure.

Japanese Unexamined Patent Publication No. 2007-09265

The present invention aims to solve the above-mentioned problems, and appropriately manages the face pressure when constructing a shield tunnel while switching between the muddy water type shield method and the muddy soil pressure type shield method. The challenge is to propose a shield excavator that enables stable construction and a shield method using this shield excavator.

The shield excavator of the present invention for solving the above-mentioned problems has a tubular outer shell, a cutter head provided at the front portion of the outer shell, a partition wall formed inside the outer shell, and the cutter. A screw conveyor connected to a chamber formed between the head and the partition wall, a mixing tank connected to the screw conveyor, a mud drain pipe connected to the mixing tank, and a feeder connected to the chamber. It is provided with a mud pipe and a merging pipe that branches from the mud feeding pipe to the mixing tank. A muddy water discharge port is provided at the upper part of the partition wall of the shield excavator and at the wellhead side end of the screw conveyor.

Further, in the shield method of the present invention, the shield excavator is used to excavate by changing the excavation method to muddy water type or muddy soil pressure type according to the ground conditions, and the excavation method is changed from muddy water type to muddy soil pressure type. At the time of switching, with the excavation of the shield excavator stopped, the plastic material is supplied to the chamber and the muddy water is discharged from the muddy water discharge port to discharge the muddy water in the chamber and the screw conveyor. After replacing with a plastic material, excavation is carried out by a mud pressure method. Further, when the excavation method is switched from the muddy soil pressure type to the muddy water type, the excavated earth and sand in the chamber are discharged into the chamber by using the screw conveyor with the excavation of the shield excavator stopped. After supplying muddy water and replacing the plastically fluidized earth and sand in the chamber with muddy water, excavation by the muddy water method is performed.

According to this shield method, when the excavation method is changed from the muddy water type to the muddy soil pressure type, the muddy water in the chamber is replaced with a plastic material before excavation, so that the face pressure can be appropriately controlled. Therefore, stable construction is possible and unexpected troubles are unlikely to occur.

At the time of excavation by the mud pressure type, it is desirable to adjust the amount of mud discharged from the mixing tank so that the pressure in the mixing tank becomes smaller than the pressure in the chamber. If the pressure in the mixing tank is high, the excavated earth and sand discharged from the chamber via the screw conveyor may be clogged in the screw conveyor. On the other hand, if the pressure in the mixing tank is made smaller than the pressure in the chamber, the excavated earth and sand can be efficiently discharged.
Further, the timing of switching the excavation method from the muddy water type to the muddy soil pressure type may be determined according to the deviation flow rate (the amount of mud loss) to the ground at the time of excavation by the muddy water type.
Further, the timing of switching the excavation method from the muddy soil pressure type to the muddy water type may be the stage when the entire length of the shield excavator excavating by the muddy soil pressure type has entered the stratum having low permeability.

According to the shield excavator and the shield method of the present invention, when the excavation method is changed from the muddy water type to the muddy soil pressure type, the muddy water in the chamber can be replaced with a plastic material before the excavation can be started, so that the face pressure is appropriately managed. You can dig in the state that you have done. Therefore, when the shield tunnel is constructed while switching between the muddy water type shield method and the muddy soil pressure type shield method, stable construction can be performed.

It is a plan sectional view of the shield excavator which concerns on embodiment of this invention. It is a vertical sectional view of a shield excavator. It is a front view of a shield excavator. It is a front view which looks at the partition wall from the wellhead side. It is a top view which shows the mixing tank.

In this embodiment, when excavating a ground where the ground to be excavated is rich in change, a shield method for excavating while switching the excavation method to a muddy water type or a muddy soil pressure type according to the ground condition will be described. As the shield excavator 1 used in such a shield method, a shield excavator 1 having a function capable of switching between a muddy water type and a muddy soil pressure type is used. As shown in FIGS. 1 and 2, the shield excavator 1 includes a tubular outer shell 2, a cutter head 3 provided at the front portion of the outer shell 2, and a partition wall 4 formed inside the outer shell 2. A screw conveyor 5 connected to a chamber 21 formed between the cutter head 3 and the partition wall 4, a mixing tank 6 connected to the screw conveyor 5, and a mud drain pipe 7 connected to the mixing tank 6. A mud pipe 8 connected to the chamber 21 and a merging pipe 9 branching from the mud pipe 8 to the mixing tank 6 are provided.

The cutter head 3 cuts the ground by rotating in front of the outer shell 2. As shown in FIG. 3, a plurality of cutter bits 31 and a disc cutter 32 are arranged on the front surface of the cutter head 3. The number and arrangement of the cutter bit 31 and the disc cutter 32 are not limited, and may be appropriately determined. The cutter head 3 is formed with an opening 33 for taking in the excavated earth and sand generated by cutting the ground into the chamber 21. The size and shape of the opening 33 are not limited, and may be appropriately determined. Further, the cutter head 3 is formed with a mud material discharge port 34 for supplying the mud material to the face. The number and arrangement of the mud material discharge ports 34 are not limited, and may be appropriately determined. As shown in FIG. 2, the cutter head 3 is rotated by the power of a cutter head motor 35 arranged inside the outer shell 2. In the present embodiment, the power of the cutter head motor 35 is applied to the cutter shaft 36 extending from the rear surface of the cutter head 3 and penetrating the partition wall 4. The configuration of the cutter head 3 is not limited.

The outer shell 2 is a tubular body arranged behind the cutter head 3 and protects various equipment inside the shield excavator 1 (for example, a motor 35 for a cutter head, a screw conveyor 5, a mud feeding pipe 8, etc.). do. The outer shell 2 according to the present embodiment is formed of a steel plate having a circular cross section. The cross-sectional shape of the outer shell 2 is not limited, and may be, for example, a rectangular shape. A shield jack 22 is arranged inside the outer shell 2, and the shield excavator 1 moves forward by the thrust of the shield jack 22 that receives the reaction force of the segment 10 arranged on the wellhead side of the outer shell 2. It is configured in.

As shown in FIGS. 1 and 2, a chamber 21 is formed in the front portion of the outer shell 2. The chamber 21 is a space in which excavated earth and sand excavated by the cutter head 3 is temporarily deposited, and is separated from the inside of the outer shell 2 by a partition wall 4 formed in the front portion of the outer shell 2.
The partition wall 4 shields the front portion of the outer shell 2. As shown in FIG. 4, a muddy water discharge port 41 is provided on the upper portion of the partition wall 4. The muddy water discharge port 41 functions as a muddy water discharge port from the chamber 21 when the excavation method is switched from the muddy water type to the muddy soil pressure type. The muddy water discharge port 41 may be used as an exhaust port for discharging the air in the chamber 21 when the inside of the chamber 21 is filled with muddy water. As shown in FIGS. 1 and 2, a hose 42 is connected to the muddy water discharge port 41. The hose 42 of the present embodiment extends to the tunnel invert portion behind the shield excavator 1. The muddy water discharged from the chamber 21 is once discharged to the invert portion. The drained mud is sucked and transported to the mud plant outside the tunnel. The discharge destination of the muddy water by the hose 42 is not limited, and may be extended to a muddy water plant outside the tunnel, or may be discharged to a water tank mounted on a trolley or the like.
As shown in FIG. 4, the partition wall 4 is provided with a soil pressure gauge 43 and a water pressure gauge 44 for measuring the pressure (face pressure) in the chamber 21. Further, the partition wall 4 is formed with an opening for connecting the screw conveyor 5 and the mud feeding pipe 8 to the chamber 21.

The screw conveyor 5 is provided with spiral blades rotatably supported inside the cylinder, and by rotating the blades, excavated earth and sand in the chamber 21 are transported to the outside of the chamber 21. The excavated earth and sand collected by the screw conveyor 5 are transported to the mud drain pipe 7 via the mixing tank 6. As shown in FIG. 2, the tip of the screw conveyor 5 penetrates into the chamber 21 through an opening formed in the lower part of the partition wall 4. The screw conveyor 5 is arranged in an inclined state so that the chamber 21 side is low and the wellhead side is high. Further, a muddy water discharge port 51 is provided on the wellhead side (upper part) of the screw conveyor 5. The muddy water discharge port 51 functions as a discharge port for discharging muddy water from the screw conveyor 5 when the excavation method is switched from the muddy water type to the muddy soil pressure type. The muddy water discharge port 51 may be used as an exhaust port for discharging the air in the screw conveyor 5 when the chamber 21 is filled with muddy water. A hose 52 is connected to the muddy water discharge port 51. The hose 52 of the present embodiment extends to the tunnel invert portion behind the shield excavator 1. The muddy water discharged from the chamber 21 is discharged to the invert portion. The drained mud is sucked and transported to the mud plant outside the tunnel. The pipe destination of the hose 52 is not limited, and may be extended to a muddy water plant outside the tunnel, or may be discharged to a water tank mounted on a trolley or the like. A mixing tank 6 is connected to the rear end (end on the wellhead side) of the screw conveyor 5 via a mud drain valve 53.

As shown in FIG. 5, the mixing tank 6 is interposed between the screw conveyor 5 and the mud drain pipe 7. Further, a merging pipe 9 extending from the mud feeding pipe 8 is connected to the mixing tank 6. The mixing tank 6 mixes the excavated earth and sand discharged from the screw conveyor 5 with the mud water discharged from the mud feeding pipe 8 via the confluence pipe 9 and discharges the mud to the mud draining pipe 7. The mixing tank 6 of the present embodiment is composed of a pipe material (so-called branch pipe) to which the merge pipe 9 can be connected. The material constituting the mixing tank 6 is not limited. Further, a member (stirring blade or the like) for promoting mixing of excavated earth and sand and muddy water may be arranged inside the mixing tank 6. Further, the mixing tank 6 is provided with a mixing tank pressure gauge 61 for measuring the pressure in the mixing tank 6.
When excavating by the muddy water type, the muddy water is not supplied from the confluence pipe 9 to the mixing tank 6, and the muddy water discharged from the chamber 21 via the screw conveyor 5 passes through the mixing tank 6 as it is. It is supplied to the mud drain pipe 7.

As shown in FIG. 1 or 2, the mud drain pipe 7 is a pipe connected to the mixing tank 6. The excavated earth and sand discharged from the chamber 21 via the screw conveyor 5 is transported to the outside of the tunnel through the mud drain pipe 7. The mud drain pipe 7 is connected to a muddy water plant outside the tunnel. The mud drain pipe 7 is provided with a mud drain pump (not shown) at a predetermined position, and the mud water discharged from the mixing tank 6 is transported at a predetermined pressure. Further, in the present embodiment, the crusher 71 is arranged at the end of the mud drain pipe 7 on the mixing tank 6 side. The crusher 71 is a device for crushing large gravel, rock mass, etc. (hereinafter, simply referred to as “gravel, etc.”) contained in excavated earth and sand. The gravel and the like crushed by the crusher 71 are transported to the muddy water plant together with the muddy water via the mud drain pipe 7. The gravel and the like may be discharged from the mud drain line and separately transported in the tunnel mine.

The mud feed pipe 8 is a pipe for supplying mud water to the chamber 21 when excavating by a muddy water type. The mud feed pipe 8 reaches the chamber 21 from a muddy water layer (not shown) provided outside the tunnel. A mud feeding pump (not shown) is provided at a predetermined position in the mud feeding pipe 8, and mud is fed by a predetermined pressure. A mud feed valve 81 is provided at a connection portion of the mud feed pipe 8 with the partition wall 4. Further, the merging pipe 9 branches from the mud feeding pipe 8.

As shown in FIGS. 1 and 2, the combined pipe 9 connects the mud feeding pipe 8 and the mixing tank 6. A merging line valve 91 that opens and closes the merging pipe 9 is provided at a base end portion (a connecting portion with the mud feeding pipe 8) of the merging pipe 9. The merging pipe 9 is branched from the mud pipe 8 and extended in parallel with the mud pipe 8 for a certain section, then bent in a U shape and then connected to the mixing tank 6. That is, the merge pipe 9 is connected to the mixing tank 6 so as to supply mud water to the mixing tank 6 in the direction along the flow of the mud drain line including the screw conveyor 5, the mixing tank 6, and the mud drain pipe 7.

The shield excavator 1 excavates by changing the excavation method to a muddy water type or a muddy soil pressure type depending on the ground conditions. That is, depending on the condition of the ground, the excavation method is switched from the muddy water type to the muddy soil pressure type or from the muddy soil pressure type to the muddy water type while excavating the ground. In addition, it is advisable to excavate by the muddy water method in the geology other than the geology with a large amount of mud (for example, the ground with high permeability). Since the muddy water shield method cuts while supplying muddy water to the face, the frictional force between the cutter head 3 and the ground can be reduced, and the burden on the shield excavator 1 (peripheral frictional force, etc.) can be reduced. It can be mitigated. Therefore, the life of the cutter bit 31 and the disc cutter 32 can be extended, the frequency of replacement can be reduced, and as a result, the labor during construction can be reduced.

When excavating by the muddy water method, if it reaches a rock with many cracks or a geological layer with high permeability of muddy water, and it is judged that the excavation by the muddy water method is inefficient due to the increase in the amount of mud, the excavation method is used. Switch from muddy water type to muddy soil pressure type. The timing (judgment standard) for switching from the muddy water type to the muddy soil pressure type is not limited, but in this embodiment, when the amount of mud loss (deviation flow rate) to the ground exceeds 50 L / min, the excavation method is muddy water. Switch from the formula to the mud pressure type. The index for switching the excavation method from the muddy water type to the muddy soil pressure type is not limited, and it is not always necessary to determine the excavation method based on the amount of mud loss.

When switching the excavation method from the muddy water type to the muddy soil pressure type, first, the excavation of the shield excavator 1 is stopped. Next, the bentonite plastic material is supplied to the chamber 21. When supplying the bentonite plastic material, first, a bentonite solution (solution A) is prepared in the plant. Next, a bentonite plastic material composed of a bentonite solution (liquid A) and water glass (liquid B) is injected into the chamber 21 from an injection valve formed in the lower part of the partition wall 4. The bentonite solution (solution A) and the water glass (solution B) are mixed in front of the injection valve (mixed immediately before injection). The plastic material is not limited to the bentonite plastic material.

Since the bentonite plastic material has a heavier specific gravity than muddy water, the bentonite plastic material is supplied so as to gradually rise from the lower side in the chamber 21. Therefore, since the muddy water rises with the supply of the bentonite plastic material, the muddy water is discharged from the muddy water discharge port 41 formed in the partition wall 4 and the muddy water discharge port 51 formed in the upper part of the screw conveyor 5. Muddy water is discharged by the amount of discharge that can maintain the face pressure. Then, when the discharge of the bentonite plastic material is confirmed from the muddy water discharge ports 41 and 51, the muddy water discharge ports 41 and 51 are closed and the bentonite plastic material is supplied until a predetermined face pressure is reached. In this way, when the inside of the chamber 21 and the inside of the screw conveyor 5 are replaced with the bentonite plastic material, the excavation is restarted by the mud pressure method.

In the excavation by the mud pressure type, the mud material produced in the mud plant is added to the central part and the outer peripheral part of the cutter head 3 with the mud feed valve 81 closed and the merging line valve 91 open. This is done while adding to the excavated earth and sand from the mud material discharge port 34. In the present embodiment, the amount of the mud material added is 15% of the excavated soil amount, but the amount of the mud material added is not limited. The excavated earth and sand mixed with the mud material in the chamber 21 is discharged from the chamber 21 via the screw conveyor 5 in a plastically fluidized state. The excavated earth and sand discharged through the screw conveyor 5 are supplied to the mixing tank 6. In the mixing tank 6, the mud water supplied from the mud feeding pipe 8 via the merging pipe 9 and the excavated earth and sand are mixed. The mixture of muddy water and excavated earth and sand is transported to a muddy water plant outside the tunnel via a mud drain pipe 7.

The face pressure during excavation by the mud pressure type is managed by adjusting the rotation speed of the screw conveyor 5. That is, the stability of the face is ensured by adjusting the pressure in the chamber 21 according to the amount of excavated earth and sand discharged from the chamber 21. At this time, a plug zone is formed in the screw conveyor 5 by the excavated earth and sand that have been plastically fluidized. The plug zone is a property region of excavated earth and sand whose face pressure can be suppressed by the viscosity of excavated earth and sand and the frictional force on the peripheral surface of the screw conveyor 5. The mud material is tested in advance to determine the optimum formulation for forming the plug zone. By forming a plug zone in the screw conveyor 5 and adjusting the rotation speed of the screw conveyor 5, it is possible to manage the face pressure according to the excavation speed. Further, by forming the plug zone, the pressure in the screw conveyor 5 can be appropriately controlled, and the plastic fluidized excavated earth and sand can be prevented from being ejected.

Further, in the present embodiment, the pressure in the mixing tank 6 is adjusted to atmospheric pressure (0 kPa) by adjusting the amount of mud discharged from the mixing tank 6. By doing so, the pressure in the mixing tank 6 becomes smaller than the pressure in the chamber 21, so that it is possible to prevent the excavated earth and sand from being clogged in the screw conveyor 5. That is, if the pressure in the mixing tank 6 is higher than the pressure in the chamber 21, the excavated earth and sand will be consolidated in the screw conveyor 5 and will be blocked. Therefore, by adjusting the mud drainage pump to make the pressure in the mixing tank 6 smaller than the pressure in the chamber 21, it is possible to prevent the pressure from acting on the excavated earth and sand in the screw conveyor 5. Here, the amount of excavated sediment at the time of excavation by the mud pressure method is a value obtained by multiplying the value obtained by subtracting the amount of mud added and the amount of mud sent to the mixing tank 6 from the mud drainage flow rate.

When a stratum with low permeability (for example, permeability coefficient ^k≤10-5 m / s) is reached during excavation by the mud pressure type, or when an increase in the amount of spring water is confirmed, the excavation method is changed from the mud pressure type to muddy water. Switch to an expression. Then, after applying water pressure (mud water pressure) to the face, it is confirmed that the water pressure acts without being released (mud). The timing for switching the excavation method is after the entire length of the shield excavator 1 excavating by the mud pressure type is made to enter the stratum to be switched (the stratum having low permeability, etc.). The stratum for switching the excavation method from the mud pressure type to the muddy water type and the timing for switching are not limited.

When the shield excavator 1 enters the stratum to be switched over the entire length, first, the excavation of the shield excavator 1 is stopped. Next, with the mud feed valve 81 and the mud drain valve 53 open, the screw conveyor 5 is used to discharge the plastically fluidized excavated earth and sand in the chamber 21, and the mud water is discharged from the mud feed pipe 8 into the chamber 21. Supply. At this time, in order to confirm that the sediment deposited in the chamber 21 has been transported by the fluid, the deviation flow rate at the time of switching the excavation method is measured, and the switching operation is performed until the discharged sediment amount reaches a predetermined amount. Further, the muddy water discharge port 41 formed in the partition wall 4 and the muddy water discharge port 51 formed in the screw conveyor 5 are opened to exhaust the air inside. After the muddy water is drained from the muddy water discharge ports 41 and 51, the muddy water is supplied with the muddy water discharge ports 41 and 51 closed until a predetermined face pressure is secured. For muddy water, the one prepared in the muddy water plant is used. Further, the face pressure is controlled by the measured value of the water pressure gauge 44 installed in the partition wall 4.
After replacing the plastically fluidized earth and sand in the chamber 21 with muddy water by the above method, excavation is restarted by the muddy water method.

At the time of excavation by the muddy water type, the excavated earth and sand mixed with the muddy water in the chamber 21 is transported to the mud drain pipe 7 via the screw conveyor 5. At this time, the screw conveyor 5 is rotated at the maximum rotation speed to prevent sand and the like from settling and accumulating in the screw conveyor 5. The rotation speed of the screw conveyor 5 during muddy water excavation is not limited, and for example, the screw conveyor 5 may be stopped. The excavated earth and sand are supplied to the muddy water plant via the mud drain pipe 7 and then separated into muddy water and earth and sand. The muddy water separated by the muddy water plant is supplied to the chamber 21 via the mud feed pipe 8. The amount of excavated sediment at the time of excavation by the muddy water method shall be the value obtained by subtracting the amount of mud transfer from the discharge mud flow rate and multiplying the excavation time.

As described above, according to the shield excavator 1 and the shield method of the present embodiment, the excavation target ground is rich in variety because the excavation method can be continuously performed while switching between the muddy water type and the muddy soil pressure type. Can be excavated efficiently.
Further, when the excavation method is switched from the muddy water type to the muddy soil pressure type, the muddy water in the chamber 21 is replaced with the bentonite plastic material, so that the excavation method can be changed while the face pressure is maintained at a predetermined pressure. .. If the chamber 21 is filled with muddy water and the muddy water is added to the chamber 21 for excavation, the muddy water is mixed with the excavated earth and sand, so that the excavated earth and sand are not plastically fluidized, and the face pressure is controlled. Becomes difficult. On the other hand, if the muddy water in the chamber 21 is replaced with plastic grout before the excavation by the mud pressure method is started, the plastic fluidization of the excavated earth and sand taken into the chamber 21 at the time of excavation is not hindered by the muddy water. Therefore, it is easy to manage the face pressure.

At the time of excavation by the mud pressure type, the pressure in the mixing tank 6 is controlled to be smaller than the face pressure by setting the pressure in the mixing tank 6 to atmospheric pressure (0 kPa). Therefore, the screw conveyor 5 to the mixing tank 6 It makes it easier to transport excavated earth and sand. As a result, consolidation of excavated earth and sand in the screw conveyor 5 can be prevented, and by extension, blockage of the screw conveyor 5 can be prevented.
Since the excavated earth and sand generated during excavation by the mud pressure type is agitated with the muddy water in the mixing tank 6, it is transported as a fluid by the mud drain pipe 7 without being exposed to the outside air. Therefore, even if the excavated earth and sand contain flammable gas or the like, the flammable gas does not leak into the tunnel pit, and safety during construction can be ensured.

Since the screw conveyor 5 is used to discharge the excavated earth and sand from the inside of the chamber 21 even during excavation by the muddy water type, the excavated earth and sand contains gravel, rock mass, etc. (hereinafter, simply referred to as “gravel, etc.”). Even in the case, it can be discharged from the chamber 21. Therefore, gravel does not accumulate in the chamber 21 and hinder excavation and control of face pressure. Further, since the gravel or the like discharged from the chamber 21 is crushed by the crusher 71, the mud drain pipe 7 is not blocked by the gravel or the like.
Further, even if the excavation method is changed, the mud draining line from the chamber 21 uses the same mud draining line (screw conveyor 5, mixing tank 6 and mud draining pipe 7), so that the shield excavator 1 The equipment arranged inside can be minimized. As a result, a work space or the like in the shield excavator 1 can be secured, and as a result, work efficiency can be improved.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-mentioned components can be appropriately changed without departing from the spirit of the present invention.
For example, the difference between the pressure in the chamber 21 and the pressure in the mixing tank 6 at the time of tunnel excavation is not limited.
Further, the timing of switching the excavation method from the muddy water type to the muddy soil pressure type and the timing of switching from the muddy soil pressure type to the muddy water type may be appropriately determined, and is not limited to the timing shown in the above embodiment.
In the above embodiment, the crusher 71 for crushing gravel and the like is provided, but the crusher 71 may be installed as needed.

1 Shield excavator 2 Outer shell 21 Chamber 3 Cutter head 4 Partition 41 Mud water discharge port 5 Screw conveyor 51 Mud water discharge port 6 Mixing tank 7 Mud drain pipe 8 Mud pipe 9 Combined pipe

Claims (5)

With a cylindrical outer shell,
With the cutter head provided at the front of the outer shell,
The partition wall formed inside the outer shell and
A screw conveyor connected to a chamber formed between the cutter head and the partition wall,
The mixing tank connected to the screw conveyor and
The mud drain pipe connected to the mixing tank and
The mud pipe connected to the chamber and
A shield excavator comprising a confluence pipe that branches from the mud feed pipe to the mixing tank.
A shield excavator characterized in that muddy water discharge ports are provided at the upper part of the partition wall and at the wellhead side end of the screw conveyor, respectively. It is a shield method for excavating by using the shield excavator according to claim 1 and changing the excavation method to a muddy water type or a muddy soil pressure type depending on the ground conditions.
When switching the excavation method from the muddy water type to the muddy soil pressure type, the plastic material is supplied to the chamber and the muddy water is discharged from the muddy water discharge port in the state where the excavation of the shield excavator is stopped. After replacing the muddy water in the screw conveyor with the plastic material, excavation by a mud pressure method is performed.
When switching the excavation method from the muddy soil pressure type to the muddy water type, the muddy water is discharged into the chamber while the excavated earth and sand in the chamber are discharged by using the screw conveyor with the excavation of the shield excavator stopped. A shield method characterized by supplying and replacing the plastically fluidized earth and sand in the chamber with muddy water, and then excavating by a muddy water method. The second aspect of the present invention is characterized in that the amount of mud discharged from the mixing tank is adjusted so that the pressure in the mixing tank becomes smaller than the pressure in the chamber during excavation by the mud pressure type. Shield method. The shield method according to claim 2 or 3, wherein the excavation method is switched from the muddy water type to the muddy soil pressure type according to the deviation flow rate to the ground at the time of excavation by the muddy water type. The shield method according to claim 2 or 3, wherein the excavation method is switched from the muddy soil pressure type to the muddy water type after the entire length of the shield excavator to be excavated by the muddy soil pressure type is made to enter the stratum having low permeability. ..

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