JP4305309B2 - Submarine tunnel construction method and submarine excavator - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is a submarine tunnel construction method in which a precast tunnel element (box) manufactured at an onshore production yard is installed on a submarine excavation ground while being joined together, and used in this construction method. This relates to a submarine drilling propulsion machine.

  A submerged tunnel construction method is known as a method of constructing a tunnel that is continuous under the water surface, such as a submarine tunnel. In this submerged tunnel construction method, tunnel elements (submerged boxes) are manufactured in a production yard such as a dry dock, and both ends are closed with temporary bulkheads (bulkheads), and then buoyant with water and towed to the construction site. Then, after sinking in a pre-drown water bottom groove (trench), the submerged boxes are joined together using water pressure, backfilled, and a tunnel continuous to the water bottom is constructed.

  In the case of such a submerged tunnel construction method, as shown in FIG. 10, it is necessary to dredge a wide trench 50 in the bottom ground B, and it is necessary to discharge the soil over a wider area than the tunnel A. There are also problems such as lowering, and there is also a problem that surrounding water pollution is unavoidable due to large-scale soil discharge. Furthermore, when a tunnel is constructed in the vicinity of a structure such as an existing tunnel, the trench 50 is wide, which may adversely affect the adjacent structure.

  In order to solve such a problem, as shown in FIG. 11, it comprises an excavation part 61 that digs the bottom ground B, and a box-shaped tail part 62 having an open upper part and a rear part capable of accommodating the box a of the tunnel element. A method has been developed for constructing a continuous tunnel A by sinking a box a in the tail portion 62 when the machine digs for one box using the submarine excavator 60. The tail portion 62 is composed of a bottom plate 63 and a pair of left and right side walls 64 rising from both left and right side portions. In order to hold the natural ground by the side walls 64, as shown in FIG. In comparison, the excavation cross section can be reduced, and the influence on the adjacent structure (shown by a dotted line in the figure) can be reduced.

Further, there are Patent Document 1 and Patent Document 2 as prior art documents related to the present invention. In the invention of Patent Document 1, in the construction method using the above-mentioned underwater excavation machine, a new box is sunk on the existing box in the shore-side water area, and the existing box is slid to the front of the first existing box. Installed so that it does not hinder the traffic of vessels in the main waterways. The invention of Patent Document 2 is a shield excavation device for constructing a submarine tunnel, a box-shaped guide that can accommodate a tunnel block, a pump that discharges soil generated during advancement, and a guide that is supplied into the guide. It is composed of a shield jack or the like for pressing the tunnel block against the existing tunnel block.
Japanese Patent No. 3487201 Japanese Utility Model Publication No. 5-96198

  When the tunnel to be constructed has a longitudinal gradient as shown in the side view of FIG. 3 and there is a longitudinal gradient changing portion in the middle, if the above-described conventional water bottom excavator 60 is applied, the tail portion 62 has Since there is the bottom plate 63, there is a problem that the bottom plate 63 and the box a in the tail part interfere with each other when passing through the longitudinal gradient changing portion, and the water bottom excavator 60 cannot pass through the vertical gradient changing portion.

  Further, when the water bottom excavator 60 moves forward, it is necessary to install a large number of rollers or the like between the box a in the tail portion 62 and the bottom plate 63 to reduce the frictional resistance so that the water bottom excavator 60 can easily move. There is. In addition, since a foundation work (foundation chestnut stone work / temporary support base work) cannot be pre-constructed in the trench as in a general submerged tunnel construction method that does not use a water bottom digging machine, After the box a is pushed out from the tail portion 62 onto the excavated ground, the back mortar and sand 65 are filled between the box a and the excavated ground behind the underwater excavator 60, and the complete foundation Difficult to build.

  The present invention has been made to solve the above-described problems. Even when a tunnel to be constructed has a longitudinal gradient, and there is a longitudinal gradient changing portion in the middle, the submarine tunnel construction method using a submarine excavator is also provided. An object of the present invention is to provide a submarine tunnel construction method and a submarine excavation propulsion device that can be constructed with a relatively simple structure and can construct a submarine tunnel and can also construct a complete foundation.

  According to the first aspect of the present invention, a plurality of boxes (tunnel elements) are joined to each other on the excavated ground after excavation using the submarine excavator and the bottom of the water bottom is installed. A submarine tunneling propulsion device comprising a front excavation part and a tail part formed by opposingly arranging side walls parallel to the direction of excavation, and the pair of side walls. After sinking the box on the ground excavated in the middle, the water bottom excavation propulsion machine is moved forward by one box, and the installation of the box between the side walls and the forward movement for one box are sequentially repeated to construct the bottom tunnel. It is the construction method of the underwater tunnel characterized by doing.

  In other words, it is a type of submerged tunnel construction method such as a submarine tunnel, using a submarine advancing machine consisting of an excavation part and a tail part. In the tunnel construction method, the tail plate is made up of a pair of left and right side walls without the tail plate of the tail, and the tunnel to be constructed has a longitudinal gradient, and this longitudinal gradient is also present when there is a longitudinal gradient change part in the middle. The bottom part excavator can pass through the change part.

  The invention according to claim 2 of the present invention is the construction method according to claim 1, wherein after a foundation (foundation chestnut and temporary support, etc.) is constructed on the excavation ground between the pair of side walls, the box is placed on the foundation. It is a construction method of a submarine tunnel characterized by being submerged.

  In other words, the foundation is provided under the box, and since there is no bottom plate at the tail, the foundation before the box is set after excavation of the bottom of the ground, as in the general submerged tunnel construction method that does not use the underwater excavation machine. Kuriishi and temporary support can be established. After constructing the foundation chestnut work and temporary support work and setting the box on top of this, mortar is poured from the box into the bottom of the box and the gap between the foundation chestnut stone to construct a complete mortar foundation.

  According to a third aspect of the present invention, in the construction method according to the first or second aspect, the longitudinal gradient changing portion of the tunnel having the vertical gradient is bent in a vertical direction with respect to the excavation portion. It is the construction method of the underwater tunnel characterized by passing through.

  That is, in the present invention, since there is no bottom plate in the tail portion, it can pass through the longitudinal gradient changing portion, but according to the shape of the longitudinal gradient changing portion, the excavation portion and the tail portion are in a folded state, and in the longitudinal gradient changing portion It is possible to dig in the excavation part and to take a reaction force on the existing box and to propel the pair of side walls.

  The invention of claim 4 of the present invention constructs a submarine tunnel (such as a submarine tunnel) by excavating the ground of the bottom and installing a plurality of boxes (tunnel elements) on the excavated ground after excavation. This is a water bottom excavation propulsion machine used when carrying out the operation, and is a tail formed by disposing a front excavation part equipped with excavation means for excavating the ground of the bottom and a side wall parallel to the excavation direction so as to accommodate the box A water bottom excavation propulsion device comprising: a section, a middle folding mechanism that foldably connects the tail section to the excavation section, and a propulsion jack for advancing the excavation section and the tail section.

  That is, a pair of side walls of the tail portion are connected to the excavation portion via a middle folding mechanism so that the longitudinal gradient change portion of the tunnel can be easily passed. The middle folding mechanism may be a joining structure that connects the tail part to the excavation part so that the tail part can be bent up and down and right and left and swings the excavation part up and down and right and left. The propulsion jack is disposed, for example, so as to connect the inner surface of the side wall of the tail portion and the existing box in the tail portion, and the excavating portion and the tail portion are advanced by taking a reaction force on the existing box. In addition, since a pair of side wall is not connected with the baseplate, in order to oppose natural ground pressure, it is preferable to connect the rear-end parts of a side wall with a joining material. Moreover, you may make it take reaction force with respect to a natural ground pressure by the box accommodated in the inside, without providing a connecting material.

  According to a fifth aspect of the present invention, in the submarine excavator according to the fourth aspect, the intermediate folding mechanism is composed of a plurality of excavation cylinders connecting the excavation part and the tail part. It is a submarine drilling propulsion machine.

  In other words, a plurality of excavation cylinders that excavate the excavation part relative to the tail part are used for the folding mechanism, and the excavation part is swung up and down and left and right by adjusting the amount of expansion and contraction of the plural excavation cylinders. It is possible to cope with the longitudinal gradient change part of the tunnel or the curve and direction correction. In this case, the water bottom excavation propulsion unit is advanced in a measuring manner using the excavation cylinder and the propulsion jack. The excavation part takes a reaction force on the side wall and the existing box and digs up with the cylinder for excavation, and then the pair of side walls takes a reaction force on the existing box and is propelled by the propulsion jack. Advance the excavator by one box.

  According to a sixth aspect of the present invention, in the submarine excavation propulsion device according to the fourth or fifth aspect, a retaining blade parallel to the direction of excavation is opposed to the front surface of the excavation part, and a space between the pair of retaining blades It is a submarine drilling propulsion machine characterized in that an excavator (such as an underwater excavator or dredger) that can be excavated is equipped in the excavation part.

  That is, as the excavating means, face plates, excavating blades, earth drills and the like can be used, but this is the case where excavation equipment in which earth retaining blades and several types of excavating machines according to the soil quality of the submarine ground are combined is used. The earth retaining blade is preferably divided into a plurality of upper and lower parts, and each blade can be easily penetrated into a natural ground by a moving cylinder. As the excavator, for example, a sandstone excavator, a sandstone grab bucket, and a rotating clay dredger for clay soil can be used.

  Since the present invention is configured as described above, the following effects can be obtained.

  (1) Since the bottom plate of the tail part of the bottom drilling propulsion machine consisting of the excavation part and tail part is eliminated and the tail part is composed of a pair of left and right side walls, the tunnel to be constructed has a longitudinal gradient, and the longitudinal section is in the middle Even if there is a slope change section, it can easily pass through this longitudinal gradient change section, and a box can be continuously deposited and joined to the longitudinal gradient change section. Can be constructed.

  (2) Since there is no bottom plate, there is no need for a roller to reduce friction with the conventional box, and it is possible to reduce the cross-section of the excavation with a relatively simple device and reduce the influence on adjacent structures. Tunnel construction method becomes possible.

  (3) Since there is no bottom plate, foundation chestnuts and temporary bearings can be constructed after excavation and before sinking the box, and the box load can be evenly transmitted to the ground, and the box and foundation are integrated. A complete mortar foundation can be constructed.

  Hereinafter, the present invention will be described based on the illustrated embodiments. This embodiment is an example applied to a submarine tunnel. 1 and 2 are a perspective view, a cross-sectional view, and a side view showing a basic structure of a submarine excavator according to the present invention. 3 and 4 are side views showing an example of the longitudinal gradient of the tunnel to which the present invention is applied and the operation of the submarine excavator of the present invention in this tunnel. 5 and 6 are side views showing an example of a submarine tunnel construction method using the submarine excavator according to the present invention in the order of steps. 7 to 9 are a side view and a plan view showing a specific example of the water bottom excavation propulsion device of the present invention.

  As shown in FIG. 1 and FIG. 2, the water bottom excavator 1 of the present invention mainly includes a front excavation part 2 having excavation means, a tail part 3 having a pair of side walls 4 and 4 and having no bottom plate, It is comprised from the middle bending mechanism 5 which connects the excavation part 2 and the tail part 3. FIG.

  The pair of side walls 4, 4 are opposed to each other in parallel with the excavation direction (tunnel axis direction) with a gap larger than the width of the box a serving as a tunnel element. The pair of side walls 4 and 4 are connected to the rear surface of the excavation part 2 via the middle folding mechanism 5 and have a length sufficiently longer than the length of the box a. Further, since the side wall 4 is cantilevered without a bottom plate, the rear ends of the pair of side walls 4 and 4 are connected by a connecting material 6. The connecting member 6 is provided at a position where the box a can be inserted from the upper opening and can be fed out from the rear opening. In addition, without providing this connecting material 6, it can also be made to take reaction force with respect to a natural ground pressure with the box a accommodated in the inside.

  The excavation means of the excavation part 2 includes a face plate (excavating the excavated soil backward with a screw conveyor), an excavating blade (disintegrating the excavated soil and seawater of the sand silt layer and discharging the fluid backward with a mud pump), grounding It is possible to use a drill (pipe excavating the excavated soil backward with a concrete pump) or a drilling facility in which a retaining blade described later and several types of excavators are combined.

  The middle folding mechanism 5 is a swing mechanism that connects the tail part 3 to the excavation part 2 so that the tail part 3 can be bent vertically and horizontally, and allows the excavation part 2 to swing up, down, left and right. This makes it possible to cope with the gradient change part and the curve and direction correction of the tunnel. A so-called universal joint joining structure or the like can be adopted as the center folding mechanism (swing mechanism), but a plurality of digging cylinders that connect the excavating part 2 and the tail part 3 as described later are used. Is preferred.

  As shown in FIG. 2, when the seabed ground B at a relatively shallow seabed is excavated by the submarine excavator 1 and advanced by one box, the box is placed on the excavated ground C between the pair of side walls 4 and 4. As will be described later, the bottom jack excavator 1 is propelled by the reaction force applied to the box a by the propulsion jack that connects the box a and the side wall 4, and the box is moved forward and boxed. The installation of a is sequentially repeated, and the boxes are joined by a normal method to construct a continuous submarine tunnel A.

  When constructing the foundation, after excavating one box, lay the foundation chestnut 10 on the excavation ground C between the pair of side walls 4 and 4 and install the temporary support (vertical jack) 11 on this. Sink box a. The mortar foundation 13 is constructed by injecting the mortar 12 from the inside of the pair of side walls 4 and 4 into the space between the bottom of the box a and the base chestnut 10 inside and behind the pair of side walls 4 and 4. Similar to the general submerged tunnel construction method that does not use an underwater excavator, (1) crushed stone mounds can be created, (2) vertical jacks 11 can be modified, and (3) mortar after boxing 12 can be injected, and (4) the foundation chestnut 10 and the mortar 12 filled can transmit the box load evenly to the ground, and the box a and the foundation can be integrated. it can.

  The box a is manufactured in an RC structure, a PC structure, an SRC structure, a steel / concrete composite structure, etc. in a manufacturing yard. The box a may be towed to the installation location, or, as in the invention of Patent Document 1, the new box is submerged on the existing box in the shore-side water area, and the guide box and the guide are placed on the existing box. It can also be slid using a groove or the like and installed with a lifting device in front of the existing box at the top.

  As shown in FIG. 3, when the seabed tunnel A to be constructed has a vertical gradient and there is a vertical gradient change part in the middle, as shown in FIG. 4, the submarine excavator 1 of the present invention has no bottom plate. The pair of side walls 4 and 4 can pass through the longitudinal gradient changing portion, and the excavation portion 2 and the tail portion 3 are bent and advanced in accordance with the longitudinal gradient changing portion by a middle folding mechanism, thereby changing the vertical gradient. In the part, the excavation part 2 can dig, and the existing box a can be moved forward with a reaction force. After passing, if the excavation part 2 and the tail part 3 are returned to a straight line, the box a can be set and excavated as usual.

  5 and 6 show the construction status at the start of construction on the land side of the submarine tunnel A in the order of steps, and construction is performed in the following procedure. Both ends of the submarine tunnel are connected to a separately constructed land tunnel via a shaft. In addition, this submarine tunnel has a vertical gradient, but is shown horizontally in the figure.

  (1) As shown in FIG. 5 (a), a cut-off wall 20 is constructed using steel pipe piles and a shaft 21 is constructed on the land side. A connecting end 22 for connecting the No. 1 box to the submarine tunnel side of the shaft 21 is constructed, and a bulkhead 23 is provided inside the connecting end 22.

  (2) As shown in FIG. 5 (b), after removing the cutoff wall 20, the dredger 24 is used to dredge a predetermined range of the seabed ground B so that the submarine excavator can be set.

  (3) As shown in FIG. 5 (c), the submarine excavator 1 of the present invention is set on the excavated ground C using a hoist ship 25 or the like.

  (4) As shown in FIG. 5 (d), the foundation chestnut 10 is constructed on the excavation ground C from between the pair of side walls 4, 4 to the connection end 22, and the temporary support 11 is placed at a predetermined position of the foundation. Install. A box may be installed without constructing such a foundation.

  (5) As shown in FIG. 6 (a), No. 1 box a1 is set on the foundation chestnut 10 and the temporary support 11. Next, the rear end portion of No. 1 box a1 is joined to the connection end portion 22.

  (6) As shown in FIG. 6 (b), the seabed ground B is excavated by the excavation part 2 while the mortar 12 is injected and the side part backfilling 14 is performed behind the submarine excavator 1. The reaction force is applied to the No. 1 box a1 and is advanced by the propulsion jack 7.

  (7) As shown in FIG. 6 (c), when one box is dug, the foundation chestnut 10 and the temporary support 11 are constructed between the pair of side walls 4, 4, and the next No. 2 box a2 Sink. The seabed ground B is excavated by the excavating unit 2 while the mortar 12 is injected and the side portion backfilling 14 is performed behind the submarine excavator 1. Take the reaction force on box 2 a1 and move it forward with a propulsion jack.

  Submarine tunnel A is constructed by sequentially repeating the installation of box a and the forward movement of one box. The tunnel is completed by backfilling the upper part of the tunnel.

  FIGS. 7 to 9 are specific examples of the submarine excavator 1 used to set up a box a having a length of about 50 m and provided with excavation equipment in which the excavation part 2 is combined with earth retaining blades and several types of excavators. It is. The side walls 4 of the tail part 3 are respectively arranged so as to be continuous with the side walls 2a on both sides of the excavation part 2, and are connected via a middle folding mechanism 5, and the pair of side walls 4, 4 are vertically and horizontally connected to the excavation part 2. The excavation part 2 can be swung up and down and left and right with respect to the pair of side walls 4 and 4.

  In this specific example, as shown in FIG. 8, a digging cylinder 8 for digging the excavation part 2 with respect to the tail part 3 by, for example, about 1 m is used for the folding mechanism 5. About four in total are arranged in a pair in the vertical and horizontal directions so that the end portions of the side wall 2a and the side wall 4 are connected to each other. 2 can be swung up and down, left and right, so that it can cope with the vertical gradient change part of the tunnel or the curve and direction correction. Note that the end portions of the side wall 2a and the side wall 4 are joined to each other by a movable engaging portion vertically and horizontally.

  A pair of upper and lower propulsion jacks 7 are provided on the inner surfaces of the pair of side walls 4, 4, and a total of about four rods are disposed, and the rod tip is detachably attached to the tip surface of the existing box a, Is also detachably attached to the inner surface of the side wall 4 so that it can be refilled. The stroke of the propulsion jack 7 is set to about 1 m as with the digging cylinder 8.

  The water bottom excavation propulsion machine 1 is advanced in a scale using the propulsion jack 7 and the excavation cylinder 8. In other words, the excavation part 2 is driven by a reaction force against the side wall 4 and the existing box a and is excavated by about 1 m by the digging cylinder 8, and then the pair of side walls 4 and 4 are driven by the reaction force against the existing box a. The jack 7 is propelled by about 1 m, and this is sequentially repeated to advance the water bottom excavation propulsion machine 1 by one box.

  As shown in FIG. 8, a pair of earth retaining blades 30, 30 parallel to the excavation direction are provided on the front surface of the excavation part 2 so that the outer surfaces thereof are flush with the outer surfaces of the side walls 2 a and 4. 9, a portion sandwiched between the pair of blades 30, 30 is excavated by a sandstone excavator 31, a sandstone grab bucket 32, and a local clay rotating drum dredger 33 as shown in FIG. ) These excavators are properly used according to the soil quality.

  As shown in FIG. 8, the earth retaining blade 30 has a substantially triangular shape in which the overall side surface shape has a protruding length that decreases downward, and is divided into three in the vertical direction, and each of the moving cylinders 34 has a stroke of about 3 m. It can be easily penetrated into natural ground.

  As shown in FIGS. 8 and 9 (a), the sandstone excavator 31 has a base attached to a rotating base 35 installed on the upper surface of the excavation part 2, and is disposed in a pair in the excavation groove width direction. The sandstone is scraped with a bucket, supplied to a crusher 37 through a hopper / stock bin 36, and pumped to a ship at sea by a pump 38. It is possible to excavate any position reliably without being affected by tidal currents. It can also be applied by modifying general-purpose machines.

  As shown in FIG. 9 (b), the sandstone slurry grab bucket 32 is attached to a portal crane 39 overhanging on the front side of the excavation section 2, grabs the sandstone slurry, and crushes 37 through the hopper / stock bin 36. To the ship at sea. Grab bucket positioning is difficult when the tide is fast. It can be applied by modifying onshore machines.

  As shown in FIG. 9 (c), the rotary drum dredge 33 is attached to the tip of the boom 40, and the earth and sand (viscous soil) excavated by the rotary drum type cutting machine is pumped by a pump 41 to a ship at sea. The boom can be operated to accurately dig at any position. It is not a general-purpose machine but has a track record.

  Needless to say, these excavators are not limited to the excavators as described above, and various excavators can be used according to the soil quality and the like.

  In addition, although the above demonstrated the case where it applied to a submarine tunnel, it is applicable also to another submarine tunnel. Moreover, although the tunnel with a longitudinal gradient change part was demonstrated, it is applicable also to a tunnel without a longitudinal gradient change part.

It is a perspective view which shows the basic structure of the water bottom excavation propulsion machine of this invention. FIG. 2 shows a construction state of the submarine excavator in FIG. 1, (a) is a cross-sectional view, and (b) is a side view. It is a side view which shows an example of the longitudinal gradient of the tunnel to which this invention is applied. It is a side view which shows operation | movement of the water bottom excavation propulsion machine of this invention in order in a vertical gradient change part. It is a side view (first half part) which shows an example of a water bottom tunnel construction method by a water bottom excavation propulsion machine of the present invention in order of a process. It is a side view (latter half part) which shows an example of the water bottom tunnel construction method by the water bottom excavation propulsion machine of this invention in order of a process. FIG. 1 shows a specific example of a submarine excavator according to the present invention, where (a) is a side view and (b) is a plan view. FIG. 8 shows the vicinity of the excavation part in the front part of FIG. 7, where (a) is a side view and (b) is a plan view. It is a side view which shows the various excavation means of the excavation part used by this invention, (a) is a sandstone slurry excavator system, (b) is a sandstone slurry grab bucket system, (c) is a rotating clay dredger for clay soil It is a method. It is a cross-sectional view which shows the conventional submerged tunnel construction method. This is a tunnel method using a conventional submerged excavator. (A) is a cross-sectional view and (b) is a side view.

Explanation of symbols

A ... Submarine tunnel (underwater tunnel)
a …… Box (tunnel element)
B ...... Submarine ground (water bottom ground)
C ... excavation ground 1 ... submerged excavator 2 ... excavation part 2a ... side wall 3 ... tail part 4 ... side wall 5 ... center bending mechanism 6 ... tether 7 ... propulsion jack 8 ... for excavation Cylinder 10 ... foundation Kuriishi 11 ... temporary support (vertical jack)
12 …… Mortar 13 …… Mortar foundation 14 …… Side backfill 20 …… Cut wall 21 …… Vertical shaft 22 …… Connection end 23 …… Bulkhead 24 …… Drawer 25 …… Hoisting ship 30 …… Soil retaining Blade 31 ... Sandstone sand shovel 32 ... Sandstone sand grab bucket 33 ... Cohesive soil rotary drum dredge 34 ... Moving cylinder 35 ... Rotary base 36 ... Hopper / stock bin 37 ... Crusher 38 ... ... pump 39 ... portal crane 40 ... boom 41 ... pump

Claims (6)

It is a construction method of a submarine tunnel that constructs a submarine tunnel by excavating the submarine ground with a submarine excavator and installing multiple boxes on the excavated ground after excavation.
The submarine excavator is composed of a front excavation part and a tail part formed by opposingly arranging side walls parallel to the excavation direction, and after sinking a box on the excavation ground between the pair of side walls, A method of constructing a bottom tunnel, wherein the bottom excavation propulsion unit is advanced by one box, and the bottom tunnel is constructed by sequentially repeating the installation of the box between the side walls and the advance of one box.   The construction method according to claim 1, wherein a foundation is constructed on the excavation ground between a pair of side walls, and then a box is sunk on the foundation.   The construction method according to claim 1 or 2, wherein the longitudinal gradient changing portion of the tunnel having the longitudinal gradient is passed by bending a pair of side walls in the vertical direction with respect to the excavation portion. Tunnel construction method. It is a submarine excavator used when constructing a submarine tunnel by excavating the submarine ground and installing a plurality of boxes on the excavated ground after excavation.
The front excavation part equipped with excavation means for excavating the bottom of the water bottom, the tail part with the side wall parallel to the excavation direction facing the box so that the box can be accommodated, and the tail part bent to the excavation part A submarine excavation propulsion device comprising: a folding mechanism that can be connected, and a propulsion jack for advancing the excavation part and the tail part.   5. The water bottom excavation propulsion device according to claim 4, wherein the center folding mechanism includes a plurality of excavation cylinders connecting the excavation part and the tail part. 6. The submarine excavator according to claim 4 or 5, wherein earth retaining blades parallel to the excavation direction are opposed to each other in front of the excavation part, and an excavator capable of excavating between the pair of earth retaining blades is provided in the excavation part. Underwater drilling propulsion machine, characterized by

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