JPH09250935A - Method for investigating sea bottom ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an investigation method which is superior in investigation precision and occupies a smaller sea area at low cost and in simple constitution in the case where sea bottom investigation is carried out at spots of large depth and strong tidal current while moving from one spot to another in a short period. SOLUTION: A plurality of omnidirectional turning propulsion machines 42 are equipped with the head and stern of a self navigation barge 30, and a position controller composed of a position measuring device, a gyro compass, a wind direction and anemometer and a control operation device controls the motors of these propulsion machines 42 to automatically hold the barge 30 at a determined spot. Since pipe casing 12 is set on the barge 30 by a pipe supporter and substantially erected at an investigation spot, a boring machine 13 is driven as the barge 30 is held at the determined spot with an automatic determined spot holding system, and a sea bottom 10 is drilled with a boring pipe 14 to perform boring investigation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to deep water (10
(0-200 m), with a fast tidal current (about 5 knots), relating to a submarine ground survey method for carrying out a seabed drilling survey of the seabed while moving the survey site every few weeks to months. Is.

[0002]

2. Description of the Related Art Marine drilling for submarine ground surveys has restrictions on the natural environment such as water depth, tidal currents, waves, and seafloor topography, as well as the social environment such as the usage of the sea for fishing and navigation of ships. . Among these restrictions, the method of offshore drilling is mainly classified into work scaffolds which are greatly influenced by natural conditions such as water depth and tidal current.

There are various types of work scaffolds,
As typical methods, there are (a) a sea-mounted type, (b) a seabed sitting type, and (c) a ship type as shown in FIG. (A) Sea-based installation type: The fixed or installation type scaffold 11 is formed by using a shape steel or a steel pipe, connected by welding, bolts, etc., assembled in a tower type and directly installed on the seabed 10, and the upper part of the fixed or installation type scaffolding 11. Boring machine 13 on base 16
Is mounted, a boring pipe 14 is provided at the center, and the seabed 10 is dug through the casing pipe 12 therein. At present, this method is the mainstream for offshore scaffolding. There are usage examples from shallow water to about 30 to 40 m.

(B) Seabed sitting type: In the survey from the sea,
Since water depth and seawater sway are major obstacles to research,
In order to eliminate this obstacle, this method is to sunk the boring machine 13 on the seabed and to excavate by remote control from the research boat 18. More specifically, the base 16 on which the boring machine 13 is mounted is fixed to the seabed 10 by the leg device 15, and the research ship 18 equipped with the control device 19 is floated on the sea surface 17, and the research ship 18 is attached to the base 16 on the seabed.
It is connected by a non-rotating wire 20. Then, power and control signals are sent from the survey ship 18 via the cable 21,
It is intended to control the submarine boring machine 13.

(C) On-board type: When the water depth becomes deep, the above-mentioned sea-mounted type and sea-bed sitting type are too expensive, and therefore boring from the boat or from the float is advantageous. In this method, an anchor block 22 and an anchor are sunk on the seabed 10 in order to prevent sway of the ship or float, and the research ship 18 (or float) is fixed by the detent wire 20 and the boring machine 13 mounted on the research ship 18 is fixed. It is operated by.

[0006]

When carrying out a seafloor boring survey while moving to a survey site every short period at a deep water or strong current point, each of the above methods has the following problems. . The sea-mounted type shown in FIG. 10 (a) is suitable for long-term drilling because it requires a large amount of cost for assembly and installation, but is not suitable for drilling surveys while moving the survey point every short period. . In addition, if the water depth is 100 m or more and there is a strong tidal current, it will be too expensive.

The seabed sitting type of FIG. 10 (b) has a water depth of 10
It is used even when it exceeds 0 m, but since the boring machine 13 is installed on the seabed, it requires diving work, and since it is fully automatic or semi-automatic control,
Not only is it troublesome to control, but the mechanism is complicated and expensive, so it is suitable for long-term boring, but it is not suitable for boring investigations while moving the investigation point every short period.

The on-board type of FIG. 10 (c) has a simple device,
It is easy to move the survey points, but there is a great deal of shaking and there is a problem in the survey accuracy. Depending on the hardness of the seabed 10, there is a risk that the boring pipe 14 may be damaged if it is tilted by 3 degrees or more with respect to the vertical direction, so the range of use is limited. Further, since the whirl-stop wire 20 generally requires a length about three times the water depth, if the water depth is 100 m, for example, the length x width will be 6 mm.
It will occupy a sea area of 00m x 600m, which may be a hindrance to the navigation of ships and the problem of infringement of fishing rights.

According to the present invention, when conducting a seafloor boring survey while moving a point of deep water and strong current every short period, the cost is low, the mechanism is simple, the survey accuracy is excellent, and The purpose is to obtain as little occupation as possible.

[0010]

SUMMARY OF THE INVENTION The present invention is a self-propelled ship 30.
Equipped with multiple omnidirectional turning propulsors 42 on the bow and stern of
The plurality of omnidirectional turning propulsion machines 42 are respectively connected to motors 43, and these motors 43 are automatically operated by a position control device 49 including a position measuring device 45, a gyro compass 46, an anemometer 47, and a control arithmetic device 48. The self-propelled carrier 30 is configured to be held at a fixed point.
It is a method of surveying the seabed, which is characterized in that 2 is installed to survey the seabed 10.

With the above-mentioned structure, when the casing pipe 12 is built substantially vertically at the survey point, the self-propelled carrier 3
The 0 is held at a fixed point by the automatic fixed point holding system, the boring machine 13 is driven, the seabed 10 is excavated by the boring pipe 14, and a boring survey is performed. In order to keep the casing pipe 12 substantially vertical during the boring survey, the thrust of each omnidirectional turning propeller 42 is adjusted to keep the position and orientation of the self-propelled ship 30 at a fixed point.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4, 30 is
It is a self-propelled ship equipped with an automatic fixed point holding system for ships. The self-propelled ship 30 is, for example, a half catamaran type,
A total of four omnidirectional swivel propulsion units 42 are installed, one at each of the four corners of the bow and stern of each catamaran. Each of these omnidirectional turning propulsion machines 42 is connected to a motor 43, and these motors 43 are automatically fixed by a position control device 49 including a position measuring device 45, a gyro compass 46, an anemometer 47, and a control arithmetic device 48. It is supposed to be retained.

A boring machine 13 and a hoist 28 are provided at the center of the upper deck of the self-propelled ship 30, and a drive device 44 is provided at the stern. The omnidirectional turning propulsion units 42 and the motors 43 installed at the four corners can be configured as four electric propulsion units driven by one main engine and a generator as a whole. Directional turning propulsion machine 4
It is also possible to equip each two independent main engines. The omnidirectional turning propulsion device 42 adopts a variable pitch propeller, so that the fixed point holding accuracy can be improved by saving the power and shortening the response time.

In the hull structure of the self-propelled pontoon 30, it is considered that the fixed point holding accuracy differs depending on the supporting position (center, front, side, etc.) of the casing pipe 12. It has the largest work space, good workability, and is the best. For this reason, the hull structure of the self-propelled ship 30 is a half catamaran type in which the introduction groove 33 is formed from the bow side to the center of the hull. In addition, the hull size is 50 to 6 when the water depth is 100 to 200 m.
The width is about 0 m and the width is about 15 to 20 m.

The casing pipe 12 is vertically mounted by the pipe support device 29 of the self-propelled ship 30,
The lower end of the casing pipe 12 is connected to a sinker 34 fixed to the seabed 10. Since the tidal current force received by the casing pipe 12 is a dominant factor in determining the scale of the self-propelled ship 30, the tidal force can be reduced by making the casing pipe 12 have a streamline shape as shown in FIG. It can be reduced to one-third of the case of a circular cross section.
In this case, the casing pipe 12 automatically faces the sinker 34 of the seabed 10 so as to face the direction with the lowest tidal force.
And the connecting portion of the pipe supporting device 29 of the self-propelled ship 30 have a rotatable structure.

Specifically, as shown in FIGS. 3 and 4, a streamlined wing portion 38 is integrally provided on one side in the length direction of the casing pipe 12, and the inner pipe 27 is housed inside. The structure has buoyancy so that it has almost the same specific gravity as seawater. As a structure for rotatably connecting the casing pipes 12, as shown in FIG. 4, a ball joint including a ball portion 40 integrally provided at a lower end portion of the casing pipe 12 and a ball receiving portion 41 provided in the sinker 34. Three
It is rotatably supported at 9 in all directions. Self-propelled barge 3
The same structure is also supported on the No. 0 pipe support device 29 side. Further, a buoy 35 for vertically standing the casing pipe 12 in the sea is attached to an upper portion of the casing pipe 12. However, this buoy 35
Is not particularly essential in the present invention.

The automatic fixed point holding system for ships will be described in more detail. 1 and 2, the self-propelled ship 30 is equipped with four omnidirectional swing propulsion units 42, one at each of the four corners of the bow and stern of each catamaran. The propulsion units 42 generate the same hydraulic power in the reference state in which thrust is generated toward the center O of the self-propelled ship 30, so that the self-propelled ship 3 can operate as long as there is no disturbance of tidal current or wind.
The position and orientation of 0 are retained. In addition, in FIG. 2, a symbol a indicates each omnidirectional turning propulsion unit 42.
Indicates the direction of thrust of the omnidirectional turning propulsion unit 4
The direction of the water flow generated from 2 is shown. Further, each omnidirectional turning propulsion unit 42 is provided with a thrust adjusting unit capable of adjusting the magnitude of the thrust and a propulsion unit turning unit capable of adjusting the direction of the thrust.

In this automatic fixed point holding system, the directions and magnitudes of the thrusts of the four omnidirectional turning propulsion units 42 can be adjusted according to the disturbance so that the position and direction of the self-propelled ship 30 can be held. The control arithmetic unit 48 includes the first arithmetic unit 5
The first, second arithmetic means 52, third arithmetic means 53, and fourth arithmetic means 54 are incorporated. The first computing means 5
1 has a function of calculating the direction and magnitude of the thrust required to maintain the fixed point of the self-propelled ship 30 and the turning moment based on the detection signals from the position measuring device 45 of the self-propelled ship 30 and the gyro compass 46. are doing.

The second calculating means 52 has a function of calculating each thrust force at each current turning angle of each omnidirectional turning propulsion machine 42 for obtaining the turning moment obtained by the first calculating means 51. are doing. Then, if the second computing means 52 cannot obtain the turning moment at the current turning angle of each omnidirectional turning propulsion device 42, the current turning angle of each omnidirectional turning propulsion device 42 is set to this omnidirectional turning propulsion. It is adapted to be slightly adjusted by the propulsion device turning means attached to the machine 42.

The third computing means 53 is provided in all directions for performing the required horizontal movement of the self-propelled ship 30 when the turning moment is obtained by the second computing means 52. It has a function of calculating the thrust of the turning propulsion unit 42.

The fourth computing means 54 has a function of adding the thrusts of the omnidirectional turning propulsion machines 42 respectively obtained by the second computing means 52 and the third computing means 53, In order to realize the thrust of each omnidirectional turning propulsion machine 42 obtained by the fourth calculating means 54, a command in the control calculating device 48 is issued to the thrust adjusting means attached to each omnidirectional turning propulsion machine 42. Instructions are sent from the means.

Next, referring to FIG. 5, the casing pipe 1
The work order of moving 2 to the survey point and installing it will be explained. In FIG. 5A, the sinker 34 side connected to the lower end of the casing pipe 12 is suspended by the lifting wire 36 of the crane 32 of the anchorage 31 and the upper end is floated by the buoy 35. The anchorage ship 31 tow the ship so that it is almost horizontal on the sea surface. At this time, the upper end of the casing pipe 12 is
The connection wire 37 is connected to the self-propelled ship 30. (B) Upon arrival at the survey point, the lifting wire 36 of the crane 32 is unreeled, and the sinker 34 sinks into the sea under its own weight, and the upper end of the casing pipe 12 is buoy 35.
And the casing pipe 12 gradually becomes vertical. (C) The sinker 34 falls on the survey point and the casing pipe 12 is built substantially vertically. When the casing pipe 12 becomes vertical, the self-propelled ship 30 is entered so that the upper end portion of the casing pipe 12 enters the call-in groove 33 of the self-propelled ship 30. (D) The self-propelled carrier 30 is entered and the casing pipes 12 are connected until the casing pipe 12 is positioned on the pipe support device 29 of the self-propelled carrier 30. When the casing pipe 12 is connected to the pipe support device 29, the self-propelled ship 30 is allowed to slide up and down to allow the sea surface 17 to move up and down due to tides and waves.

After the casing pipe 12 is built substantially vertically at the survey point in this way, the self-propelled ship 30 is driven by the automatic fixed point holding system while driving the boring machine 13 while holding it at a fixed point, and the boring pipe 14 is used to drive the seabed. Drill 10 to conduct a boring survey. In order to keep the casing pipe 12 substantially vertical during the boring survey, it is necessary to adjust the thrust of each omnidirectional turning propulsion unit 42 to keep the position and direction of the self-propelled ship 30 at a fixed point.
The operation therefor will be described below with reference to the flowchart of FIG.

When the self-propelled ship 30 is subjected to disturbances of tidal currents and winds,
When the position and orientation of the self-propelled ship 30 change, the first
The calculation means 51 of the position controller 4 detects the position of the self-propelled ship 30 in order to return the self-propelled ship 30 to the original state.
Gyro compass 4 that detects the direction of 9 and self-propelled ship 30
Based on the detection signal from 6, the operation of calculating the direction and magnitude of the thrust required for the self-propelled ship 30 and the turning moment of the self-propelled ship 30 is performed.

Next, the second computing means 52 operates to compute the magnitude of each thrust at the present turning angle of the plurality of omnidirectional turning propulsion machines 42. Each omnidirectional turning propulsion machine 42
At the present turning angle, the turning moment cannot be obtained even if each thrust is changed, that is, the turning moment is obtained? In the case of NO, the propulsion device turning means performs the action of slightly adjusting the turning angle of each omnidirectional turning propulsion device 42.

In this way, when the second computing means 52 can obtain the turning moment, that is, has the turning moment been obtained? If YES, the omnidirectional turning propulsion unit 4 for the horizontal movement necessary for returning the self-propelled ship 30 to the present position is calculated in the third calculating means 53.
A calculation for obtaining a thrust of 2 is performed.

The fourth calculating means 54 adds the thrusts of the omnidirectional turning propulsion machines 42 obtained by the second calculating means 52 and the third calculating means 53. In order to realize the thrust of each omnidirectional turning propulsion machine 42 obtained in this way, the commanding means in the control arithmetic unit 48 commands the thrust adjusting means of each omnidirectional turning propulsion machine 42.

By the above operation, each omnidirectional turning propulsion unit 4
The reference numeral 2 designates that the thrust direction is directed to the center O of the hull, and each omnidirectional turning propulsion machine 4 from this reference state
The turning angle of 2 is suppressed to be as small as possible. Therefore, the water flow containing bubbles generated from each omnidirectional turning propulsion unit 42 is not sucked into another omnidirectional turning propulsion unit 42.

The thrust of each omnidirectional swivel propulsion machine 42 is greatly influenced by the speed of the water flow flowing into the same omnidirectional swirl propulsion machine 42, and the thrust tends to be smaller as the inflow speed is higher. Even if the gas flows into the omnidirectional turning propulsion device 42, a sufficient thrust cannot be obtained. However, since the water flow containing bubbles generated by each omnidirectional swirl propulsion machine 42 is prevented from flowing into another omnidirectional swirl propulsion machine 42 by adopting the system as described above, each omnidirectional swirl propulsion machine 42 is prevented. Is
The required thrust can be secured in accordance with the command from the thrust adjusting means, whereby the position and azimuth of the self-propelled ship 30 can be held appropriately.

In this way, each omnidirectional turning propulsion unit 42
While the adjustment of the turning angle is minimized, the fixed point of the self-propelled ship 30 is held by adjusting the hydraulic power of each omnidirectional turning propulsion unit 42, and the response to the disturbance is promptly performed. Self-propelled barge 3
The boring machine 13 is operated while controlling the fixed point maintenance of 0, and the ground of the seabed 10 is investigated. When the survey at that point is completed, the survey is repeated while moving to another survey point in the same manner as shown in FIG.

Next, when the accuracy of the fixed point holding control was confirmed, the following results were obtained, which will be explained. As a condition for confirming the accuracy of the fixed point holding control, the boring pipe 14 was attached to the center of the self-propelled ship 30, the casing pipe 12 had a circular cross section with a diameter of 1.2 m, and the external force was 5 kn of tidal current and 15 m of wind speed. Second, wave height 1
m, 3m (x = -3m) in front and back, 5m in left and right direction
The behavior from the position (y = 5 m) to the convergence was determined.
Since the control of the self-propelled ship 30 detects the flow direction and always directs the direction of the self-propelled ship 30 to the flow direction, all the acting directions of the external force are in the front direction. As a result, FIG.
As shown in (a), it converged in less than 40 seconds.

Subsequently, from the state of being converged at the target position, the wave direction was changed by 20 ° and the wind direction was changed by 30 ° in steps, and the detection error in the tidal current direction and the responsiveness of the sudden change in the wind direction were confirmed. As a result, as shown in FIG. 7 (b), it converged in about 50 seconds. The casing pipe 12 had a streamline cross section with a diameter of 1.2 × 2.4 m as shown in FIG.

In the above embodiment, as shown in FIG. 2, the case where the casing pipe 12 is installed in the center of the self-propelled ship 30 has been described. However, the present invention is not limited to this, and as shown in FIG. 8, the pipe support device 29 may be provided on the side surface of the self-propelled ship 30 to install the casing pipe 12. Although not shown, it may be installed on the bow of the self-propelled ship 30. However, the casing pipe 12
The installation position of the self-propelled ship 30 is large because the convergence time for maintaining the fixed point of the self-propelled ship 30 is fast, and the flexibility of the installation space for materials and equipment required for boring is large.
The center of is the best.

In the above embodiment, the case where the self-propelled ship 30 is equipped with four omnidirectional turning propulsion machines 42, one at each of the four corners of the bow and the stern, has been described. However, the present invention is not limited to this, and as shown in FIG. 9, one omnidirectional turning propulsion unit 42 having thrust in the forward direction is provided at each of the two corners of the stern of the self-propelled ship 30, and is provided at the center of the bow. You may make it equip with one omnidirectional turning propulsion machine 42 which has thrust in a horizontal direction, and may equip three omnidirectional turning propulsion machines 42 in total.

[0035]

【The invention's effect】

1) In the present invention, the casing pipe 12 is installed by the pipe support device 29 on the self-propelled ship 30 equipped with the position control device 49 for holding the fixed point on the sea surface 17 and the seabed 10 is provided.
Therefore, when conducting a seabed drilling survey at a deep water depth of 100 m or more while moving a strong current of 5 knots or more, it is necessary to assemble and install the seabed compared to the sea-based or seabed-seated type. It is inexpensive and extremely inexpensive.

2) Self-propelled ship 30 and casing pipe 12
Since it is easy to move, it is suitable for a boring survey while moving the survey point every short period.

3)) Even with the simple method of using the self-propelled ship 30, the shaking is extremely small and the survey accuracy is high.
Incidentally, according to the actual measurement, the inclination of the casing pipe 12 was about 1.7 degrees even if it was large.

4) Since the detent wire 20 for mooring the self-propelled barge 30 is not required, it occupies the sea area, and there are no problems such as hindering the navigation of the ship and infringing fishing rights. .

[Brief description of drawings]

FIG. 1 is a front view showing a state where a casing pipe 12 is installed on a self-propelled ship 30 for explaining a method for investigating a seabed according to the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a cross-sectional view of a casing pipe 12 used in the seabed ground survey method according to the present invention.

FIG. 4 is a partially cutaway sectional view showing a connected state of the casing pipe 12 and the sinker 34 used in the seabed ground survey method according to the present invention.

FIG. 5 is an explanatory diagram showing a work sequence for installing the casing pipe 12 at a survey point.

FIG. 6 is a flowchart of a fixed point holding system for the self-propelled ship 30.

7 (a) is a waveform diagram showing a behavior of the fixed point holding system of the self-propelled ship 30 until the casing pipe 12 converges to a target point. FIG. (B) is a waveform diagram showing the behavior of the self-propelled ship 30 at the fixed point position and the casing pipe 12 when an external force is applied until the fixed point holding system converges on the destination point of the casing pipe 12.

8 is a plan view showing an example in which a casing pipe 12 is installed on a side surface of a self-propelled ship 30. FIG.

FIG. 9 is a plan view showing an example in which the self-propelled ship 30 is provided with three omnidirectional turning propulsors 42.

FIG. 10 shows different examples of conventional offshore scaffolding for offshore drilling, where (a) is an offshore installation type, and (b) is
[FIG. 3] is an explanation view of a seabed sitting type, and (c) is an illustration of a ship type.

[Explanation of symbols]

10 ... sea bottom, 11 ... fixed or installed scaffolding, 12 ... casing pipe, 13 ... boring machine, 14 ... boring pipe, 15 ... leg device, 16 ... base, 17 ... sea surface, 18 ... research ship, 19 ... control device, 20 ... Detent wire, 21 ... Cable, 22 ... Anchor block, 27
... inner pipe, 28 ... hoist, 29 ... pipe support device, 30 ... self-propelled barge, 31 ... lifting anchor, 32 ... crane,
33 ... introduction groove, 34 ... sinker, 35 ... buoy, 36
... Lifting wire, 37 ... Connecting wire, 38 ... Streamline wing section, 39 ... Ball joint, 40 ... Ball section, 41 ...
Ball receiving part, 42 ... Omnidirectional turning propulsion device, 43 ... Motor, 44 ... Driving device, 45 ... Position measuring device, 46 ... Gyro compass, 47 ... Wind direction anemometer, 48 ... Control computing device, 49 ... Position control device, 51 ... First computing means, 52
... second computing means, 53 ... third computing means, 54 ... fourth
Calculation means.

Claims (6)

[Claims] 1. A seabed 10 is provided by installing a casing pipe 12 by a pipe supporting device 29 on a self-propelled ship 30 equipped with a position control device 49 for holding a fixed point on the sea surface 17.
The method for surveying the seabed is characterized in that 2. The seabed ground survey method according to claim 1, wherein the casing pipe 12 is provided with a sinker 34 at a lower end thereof and a buoy 35 at an upper portion thereof. 3. The seabed ground survey method according to claim 1 or 2, wherein the self-propelled ship 30 is equipped with a plurality of omnidirectional turning propulsion units 42 on its bow and stern. 4. A plurality of omnidirectional turning propulsion machines 42 are respectively connected to motors 43, and these motors 43 include a position measuring device 45, a gyro compass 46, and an anemometer 4.
7. The seabed ground survey method according to claim 3, wherein a position control device 49 including a control calculation device 48 is used to automatically hold a fixed point. 5. The control arithmetic unit 48 adjusts the directions and magnitudes of the thrusts of the plurality of omnidirectional turning propulsion units 42 according to the external disturbance so that the position and direction of the self-propelled ship 30 can be maintained. The control arithmetic unit 48 includes a first arithmetic unit 51 and a second arithmetic unit.
The calculation means 52, the third calculation means 53, and the fourth calculation means 54 are built in, and the first calculation means 51 is the self-propelled ship 3
Based on detection signals from the position measuring device 45 and the gyro compass 46 of 0, it has a function of calculating the direction and magnitude of the thrust necessary for holding the fixed point of the self-propelled ship 30 and the turning moment, and the second calculation The means 52 has a function of calculating each thrust at each current turning angle of each omnidirectional turning propulsion unit 42 for obtaining the turning moment obtained by the first calculating means 51, and each omnidirectional turning With the current turning angle of the propulsion unit 42, when the second turning means 52 cannot obtain the turning moment, the current turning angle of each omnidirectional turning propulsion unit 42 is attached to the omnidirectional turning propulsion unit 42. It is adapted to be slightly adjusted by the propulsion device turning means, and the third calculating means 53 is self-propelled when the second calculating means 52 can obtain the turning moment. And a function for calculating the thrust of the omnidirectional pivot propulsion devices 42 for performing the required horizontal movement of the ship 30, the fourth calculating means 54, the second arithmetic unit 5
It has a function of adding the thrusts of the omnidirectional turning propulsion units 42 respectively obtained by the second and third calculating means 53,
Each omnidirectional turning propulsion unit 4 is configured so that the thrust of each omnidirectional turning propulsion unit 42 obtained by the fourth calculating means 54 is realized.
2 to the thrust adjusting means attached to the control arithmetic unit 48.
The seabed ground survey method according to claim 3, characterized in that a command is sent from the command means inside. 6. The casing pipe 12 is hung by a crane 32 of an anchorage ship 31 in order to move and install the casing pipe 12 to a survey point, and the vessel is towed to the survey point, and when it arrives at the survey point, the crane 32 is used. The casing pipe 12 is paid out and built up substantially vertically, and the casing pipe 12 is attached to the pipe support device 2 of the self-propelled ship 30.
9. The boring machine 13 is driven while the self-propelled ship 30 is held at an automatic fixed point, and the seabed 10 is excavated by the boring pipe 14 to perform a boring survey. The seabed ground survey method described in 5.