JPS6140918A - Improver for seabed soft ground - Google Patents

Abstract

PURPOSE:To obtain well-improved ground by using a ground improver in which a grount improving agent jet nozzle and a stirring blade are provided to the lower end of a hollow stirring shaft, and a water depth sensor, a sensor for the vertically moving amount of the stirring blade, and the penetration depth arithmetic device for the stirring blade are provided to the base ship. CONSTITUTION:A ground improving agent is supplied pneumatically to a stirring blade 3 and injected from an jet nozzle 5, where the agent is mixed with soil by the stirring blade 6. Water depth D0 from a base ship 1 to the seabed face A is detected by a water depth sensor 12 during the ground improving operation and the detected value is sent to an arithmetic unit 21. The vertically moving amounts l1 and l2 of the shaft 3 and an air recovery tube 8 are detected by a vertically moving amount sensor using laser beams and sent to an arithmetic unit 21. The penetration depth D2 of the blade 6 is calculated by the unit 21 11 to adjust the depth D2 of the blade 6 by a controller 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a submarine soft ground improvement device for improving soft ground such as the seabed.

(Conventional technique vFI) Conventionally, as a construction method for improving soft ground on the seabed, a hollow stirring shaft installed on a barge that can be rotated and raised and lowered is rotated, and a stirring blade installed at the tip is inserted into the soft ground on the seabed. After penetrating to a predetermined depth, the soil improvement material is pulled out, and in either the penetration or withdrawal process, the ground improvement material is pneumatically fed to the improvement material supply passage provided in the stirring shaft, and is then pumped through the injection port at the lower end of the stirring shaft. An injection stirring method @ (DJM method) is known that improves the soft ground by injecting it into the soft ground and stirring and mixing the ground improvement material and the soft ground using stirring blades.

In this method, by sequentially displacing the penetration position of the stirring blade in the radial direction and repeating the above process, a large number of pile-shaped improved soils are placed adjacent to each other to improve the ground in a predetermined range. In order to obtain this, it is necessary to make the depth of each pile-shaped improved ground uniform and adjust it according to the degree of soft ground, and accordingly, it is necessary to adjust the penetration depth of the stirring blade from the seabed surface. There is.

For this reason, conventional methods have been to detect the amount of rotation of a winding drum of a winch that raises and lowers the stirring shaft on a barge, or to interlock a wire with the stirring shaft and detect the amount of rotation of a pulley that stretches the wire. The amount of vertical movement of the stirring shaft was calculated based on the detected value.

However, in this type of seabed ground improvement work, even a stand is required. Even if it is possible to accurately detect the amount of elevation of the stirring shaft relative to the ship, the depth of the water from the barge to the seabed changes from moment to moment, so it is difficult to accurately detect the depth at which the stirring blade enters from the seabed. Can not. For this reason, conventionally, the water depth at the time of work is found from the tide table, and the vertical direction of the stirring shaft is corrected each time in response to changes in water depth based on the tide table, and the penetration depth is adjusted. In this case, it is very troublesome to have to look at the tide table, and the water depth value from the tide table is inaccurate, making it impossible to accurately control the depth, and the depth of the ground improvement is inadequate. There were various problems such as uniformity.

(Objective of the Invention) In view of these points, the present invention is capable of always accurately detecting the depth of penetration of the stirring blade into the seabed, even if the water depth changes depending on the work date and time, so that the soil improvement depth can always be optimized. To provide a device that can obtain improved ground of good quality by easily making it uniform and in a good condition.

- (Structure of the Invention) The present invention provides an injection port for a ground improvement material that is pneumatically fed through a passage in the stirring shaft at the lower end of a hollow stirring shaft that is provided on a barge through a leader so as to be able to rotate and move up and down. and a stirring blade, and the barge is provided with a water exploration device for detecting the water depth from the barge to the seabed surface, and a lifting amount detection device for detecting the lifting amount of the stirring shaft with respect to the barge; The apparatus is characterized in that it is equipped with a calculator that calculates the depth of penetration of the stirring blade into the seabed based on the detected value of the detection device.

(Example) First, the overall configuration of the submarine soft ground improvement device will be explained with reference to FIG. 2.

In FIG. 2, a barge 1 is equipped with a leader 2, and a stirring shaft 3 is supported by the leader 2 so as to be rotatable and movable up and down. The stirring shaft 3 is hollow and has an improving material supply passage 4 inside it.
is formed, and a ground improvement material injection port 5 and stirring blades 6 are provided at the lower end.

The upper end of the stirring shaft 3 is connected to a rotary drive device 7.

An air recovery pipe 8 is fitted onto the outside of the stirring shaft 3, and an air recovery passage 9 is formed between the air recovery pipe 8 and the stirring shaft 3.
is formed. At the lower end of the air recovery pipe 8, a hood 10tfi having an inner diameter larger than the diameter of the stirring blade 6 is provided in order to guide the air that has been separated from the improving material and has risen to the air recovery passage 9, and an exhaust pipe is provided at the upper end. A port 11 is provided.

-Next, the device for depth detection used in the apparatus of the present invention will be explained based on FIG.

In FIG. 1, a water exploration device M12 such as a sonic probe is installed at the bottom of the C1 barge 1 in order to detect the water depth Do from the barge 1 to the seabed surface A.

On the other hand, at the upper part of the barge 1, the stirring shaft 3 is connected to the barge 1.
In order to detect the vertical movement of the air recovery pipe 8, a laser oscillator 13, a half mirror 14, and a switching mirror 1 are used.
5, omnidirectional mirrors 16', 17, etc., and a geophone 18. The laser oscillator 13, the half mirror 14, and the receiver 18 are installed at predetermined height positions of the leader 2 (see FIG. 2) and other fixed frames provided on the barge 1, and are mounted on the omnidirectional mirror 1.
6 is fixed to the upper end of the stirring shaft 3, and the omnidirectional mirror 17 is fixed to the upper end of the air recovery pipe 8. Both mirrors 16 and 17 are vertically opposed to each other, and between them, a switching mirror 15 is fixed to a fixed frame such as a reader. The bottom position can be changed freely.

In addition, the detection signal from the water exploration device 12 and the vibration receiver 51
The signals from 8 to 2 are sent to the computer 19. This computer 19 is provided with a setting device 2' O-1 calculator 21, a control device 22, etc., and performs calculations such as those described later.
Control takes place.

Next, the ground improvement work will be explained.

First, to explain the outline of the work, the stirring shaft 3 and the air recovery pipe 8 are lowered into the water together by a winch (not shown) or other well-known elevating means, and the lower ends of the stirring blades 6 and the air recovery pipe 8 are lowered into the water. When it touches down on the seabed surface A, its descent is temporarily stopped, and then only the air recovery pipe 8 is lowered again by a lifting device (not shown), and the hood 10 at its lower end penetrates into the soft ground of the seabed.

Next, with the hood 10 maintained in the penetrating state, the stirring @ 3 is lowered by a lifting device (not shown) while being rotated by the rotary drive machine 7, and penetrates into the soft ground while the stirring blades 6 are rotated. After the stirring blade 6 has penetrated to a predetermined depth, the stirring blade 6 is pulled out while being rotated. Then, in one process of penetrating or pulling out the stirring blade 6, the powdery ground improvement material is supplied to the improvement material supply passage 4 in the stirring shaft 3 by air pressure, and is inserted into the soft ground from the injection port 5. At the same time, the ground improvement material and the ground soil are stirred and mixed by the rotation of the stirring blade 6,
Therefore, the soft ground will be improved.

In addition, during this ground improvement, the used air used for pneumatically feeding the ground improvement material rises along the outer circumferential surface of the stirring shaft 3 and through the ground soil stirred during penetration and extraction, and reaches the hood. The air is collected in the hood 10, passes through the air recovery passage 9, and is discharged into the atmosphere through the exhaust port 11.

In this way, when the above-mentioned ground improvement is completed, the above-mentioned stirring TA6
In the extraction process, after the stirring blade 6 is pulled out by an amount corresponding to the penetration depth, the stirring shaft 3 and the air recovery pipe 8 are raised together and extracted from the soft ground, and then they are moved to the next ground improvement position. Then, by repeating the above steps, the ground is improved in a predetermined range.

In this case, at each ground improvement position, it is necessary to adjust the improvement depth according to the degree of softness of the soft ground, and if the degree of softness is constant, it is necessary to equalize the improvement depth.

Next, the depth control will be explained. 'During the above-mentioned ground improvement work, the water depth O from the barge 1 to the seabed surface A is detected by the water exploration device 12, that is, from the water exploration device 12 to the seabed surface A, and the detected value Do is sent to the calculator 2.
It is sent to 1.

When the hood 1o penetrates, the switching mirror 1
5 is located at the broken line position in the drawing, the light emitted from the laser oscillator 13 passes through the half mirror 14, and the switching mirror 15
The light is reflected downward and reaches the omnidirectional mirror 17 provided at the upper end of the air recovery tube 8, and the light reflected by this mirror 17 is reflected by the switching mirror 15 and the half mirror.
14 and is received by the geophone 18, thereby measuring the distance +mρ1 from the optical axis of the laser oscillator 13 to the mirror 17. This distance l1IliQ1 corresponds to the amount of elevation of the air recovery pipe 8 with respect to the barge 1, and its measured value is sent from the geophone 18 to the arithmetic unit 21.

Here, the water depth detected by the water exploration device 12 is D.
o, the amount of elevation of the air recovery pipe 8 sent from the geophone 18 is Ω
1. The height from the deck surface of the barge 1 to the optical axis of the laser oscillator 13 is t-h, the height from the deck surface to the water exploration device 12 is 82, and the total length of the air recovery @8 is Ll. Then,
The penetration depth D1 of the hood 10 installed at the lower end of the air recovery pipe 80 into the seabed surface is determined by the following equation.

Dl-(L1+l11)-(Do +81 +82>
In this case, the heights H'l and H2 are constant, and
Since the total length L1 of the air recovery pipe 8 is specified, by setting these values in the setting device 20 in advance, if the water depth Do and the amount of elevation p1 are known, the penetration depth of the hood 10 into the seabed surface A can be determined. D1 can be easily calculated by the calculator 21.

Also, when the hood 10 penetrates, the water *Do
While sequentially detecting the lifting amount Q1 of air recovery @8,
By controlling the lifting device of the air recovery pipe 8 by the control device 22, the penetration depth D1 of the hood 10 is adjusted in accordance with the softness of the soft ground on the seabed, so that the heaving phenomenon does not occur during subsequent ground improvement. It can be done.

Next, in the penetration and extraction process of the stirring blade 6, the -switching mirror 15 is switched to the solid line position in the figure, and the light emitted from the laser oscillator 13 passes through the half mirror 14 and is reflected upward by the switching mirror 15. and stirring shaft 3
The light reaches the omnidirectional mirror 16 provided at the upper end, and the light reflected by this mirror 16 is received by the receiver 18 via the switching mirror 15 and the half mirror 14, so that the light from the laser oscillator 13 is The distance ρ2 from the axis to the omnidirectional mirror 16 is measured. This distance Ω2 corresponds to the amount of elevation of the stirring shaft 3 with respect to the barge 1, and its measured value is sent from the geophone 18 to the arithmetic unit 21.

Here, the lifting amount of the stirring shaft 3 is ρ2, and the total length of the stirring shaft 3 is 1.
2, the penetration depth D2 of the stirring blade 〇 into the seabed surface A is determined by the following equation, as in the case of the penetration of the hood 10.

D2 = L2- (Do -N-11+82-) [z
) In this case, the heights Hl and H2 are constant, and the stirring shaft 3
Since the total length L2 of the stirring blade is specified, by setting these values in the setting device 20 in advance, once the water depth between the bends Do and the lifting amount ρ2 of the stirring shaft 3 are known, the calculation unit 21 determines the length of the stirring blade. The penetration depth D2 of 6 can be easily calculated.

Further, when the stirring blade 6 penetrates, the control device 22 controls the lifting device of the stirring shaft 3 while sequentially detecting the water depth Do and the lifting amount ρ2 of the stirring shaft 3, and controls the penetration depth D2 of the stirring 116. By adjusting it in accordance with the degree of softness of the soft ground, it is optimal.In the above embodiment, the elevation IJ1 of the stirring shaft 3 and the elevation Q2 of the air recovery pipe 8 are detected using a laser beam. These lifting and lowering 11. The means for detecting ρ2 is not particularly limited in the present invention, and any known detecting means may be used. However, even in this case, the water depth Do from the barge 1 to the seabed surface A is detected using the water exploration device 12, and this water depth DO and the above-mentioned lifting amount Ω1.
Penetration depth D1 of hood 10 and stirring blade 6 based on ρ2
The penetration depth D2 is controlled.

(Effects of the Invention) As explained above, the present invention detects the penetration depth of the stirring blade into the seabed based on the water depth from the barge to the seabed and the amount of elevation of the stirring shaft with respect to the barge. Even if the water depth changes depending on the work date and time, it is possible to always accurately detect the depth of penetration of the stirring blade into the seabed surface, and the soil improvement depth can always be optimal, and it can be easily uniformized, resulting in high-quality improvement. It is something that can gain ground.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the arrangement of main equipment in the apparatus of the present invention, and FIG. 2 is a side view of the main parts without showing an overview of the submarine soft ground improvement apparatus. 1... Barge, 2... Leader, 3... Stirring shaft, 6...
... Stirring blade, 8... Air recovery pipe, 10... Hood,
12... Water exploration device, 13... Laser oscillator, 1
4... Half mirror 115... Switching mirror, 16
．． 17... Omnidirectional mirror, 18... Geophone, 19.
...Computer, 21...Arithmetic unit, A...Seafloor surface.

Claims (1)

[Claims] 1. At the lower end of a hollow stirring shaft that is rotatably and movably provided on the barge via a leader, an injection port for the ground improvement material that is pneumatically fed through a passage in the stirring shaft and stirring blades are provided, and , the barge is equipped with a water exploration device that detects the water depth from the barge to the seabed, a lift amount detection device that detects the amount of elevation of the stirring shaft relative to the barge, and a seabed surface based on the detected values of both of the detection devices. A submarine soft ground improvement device characterized by being equipped with a computing unit that computes the penetration depth of a stirring blade into a soil.