JP3584201B2 - Sand pile forming equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for forming a sand pile for improving a ground in soft ground.
[0002]
[Prior art]
Conventionally, as an apparatus for forming this kind of sand pile, there has been one disclosed in Japanese Patent No. 2791914.
[0003]
As shown in FIG. 15, the sand pile forming apparatus disclosed in this patent is provided with a vibro hammer 46 at its head, and a sand pile forming hollow having a sand input hopper 42 and a compressed air supply pipe 43 mounted above. A downward cylinder 44 driven by the supply of pressurized water and a plurality of sand compaction and discharge blades 45 driven vertically by the downward cylinder 44 are provided below the pipe 41 in a radial manner. Reference numeral 47 denotes a pressurized water supply pipe for supplying pressurized water to the downward cylinder 44.
[0004]
A method for forming a sand pile using this apparatus is as follows.
[0005]
First, the hollow pipe 41 is driven to a predetermined depth with a vibro hammer 46, sand is charged from the hopper 42, and compressed air is blown from the compressed air supply pipe 43. At this time, the air pressure in the hollow tube 41, the extent to which the surrounding soil does not flow into the tube, never put sand in the tube should not as a large air pressure, such as is discharged to outside the tube.
[0006]
In this state, the pressurized water is injected into the cylinder 44 to move the discharge blade 45 up and down a plurality of times at a constant speed, so that the contact resistance between the discharge blade 45 and almost all of the sand left in the hollow tube 41 remains. As a result, the material is forcibly extruded and discharged below the hollow tube 41. At this time, the hollow tube 41 is also pulled out of the ground by a predetermined length. As a result, the discharged sand is compacted by the discharge blade 45.
[0007]
When the sand is discharged into the soft ground in this manner, the pressure in the pipe 41 is released, a predetermined amount of sand is supplied again from the hopper 42, and the balance is maintained with the earth pressure according to the displacement of the lower end of the hollow pipe 41. The sand is discharged and compacted by the pressurization in the pipe and the operation of the cylinder 44, and the hollow pipe 41 is pulled out to a predetermined length. Thereafter, this operation is repeated to form a sand pile.
[0008]
The degree of the above-mentioned pressurization is determined based on the earth pressure by previously calculating the earth pressure corresponding to the depth of the lower end of the hollow tube 41.
[0009]
As another sand pile forming apparatus, there is a sand pile forming apparatus disclosed in Japanese Patent Publication No. Hei 8-1060, filed by the present applicant.
[0010]
As shown in FIG. 16, a cylindrical valve in which a ball valve 16 having a predetermined specific gravity is vertically movably held at the tip of a casing pipe 11 provided with a nozzle 21 for introducing compressed air therein. An end cover case 13 'is attached, and a valve seat portion 14 which is closed by the ball valve 16 is provided at an opening portion at the tip of the casing pipe 11 (the lower end in FIG. 16). At the time of driving, the ball valve 16 closes the tip of the casing pipe 11 so as to prevent intrusion of earth and sand. When discharging sand for forming a sand pile, the ball valve 16 is operated by the pressure of sand and compressed air. A gap for sand discharge is formed between the seat portion 14 and the tip cover case 13 '.
[0011]
[Problems to be solved by the invention]
The conventional sand pile forming apparatus shown in FIG. 15 is provided with a sand compaction / discharge wing movably up and down at the tip end inside the hollow tube, and does not require a downward cylinder for driving this discharge wing. However, there is a problem that they may be damaged by sand injected into the hollow tube or pressure at the time of fitting the hollow tube, and they may also become obstacles in discharging the sand. In addition, this device requires additional equipment such as a pressurized water supply device for operating the downward cylinder and its control device, so that the equipment becomes large-scale, and the preparation and work also require extra labor. was there.
[0012]
In addition, in the method of forming a sand pile using this apparatus, a predetermined amount of sand is charged into a hollow tube, compressed air of a predetermined pressure is blown, and the discharge wing is moved up and down in this state to compact the sand. In addition, the operation of pulling out the hollow tube by a predetermined length had to be repeatedly performed, and the work efficiency was extremely poor. Also, according to the drawing of the hollow pipe, the air pressure in the pipe is controlled so as to maintain the balance with the earth pressure according to the displacement of the lower end, but since this earth pressure is based on the calculated value, However, depending on the actual condition of the ground, the air pressure is not always optimal, and there is a possibility that desired work may not be performed.
[0013]
In the apparatus shown in FIG. 16, when the casing pipe is driven, the tip is closed by a ball valve, so that there is no danger of seawater or clayey sand entering the inside, but the sand is discharged. In such a case, there is a problem that the ball valve becomes an obstacle, and it takes time to discharge the ball valve.
[0014]
An object of the present invention is to solve the problems of the above-mentioned conventional sand pile forming method and apparatus.
[0015]
Means for Solving the Problems To solve the above problems, the invention according to claim 1 of the present invention provides a casing pipe provided with a nozzle for introducing compressed air therein, and a tip attached to a tip of the casing pipe. In a sand pile forming apparatus comprising a lid, the above-mentioned tip lid is a substantially frusto-conical tip lid case with an expanded tip, a ball valve movably housed in the tip lid case, and the ball valve. And a valve seat part which makes the inside of the tip of the casing pipe in a sealed state by contacting the casing pipe.The tip lid case is provided with an earth pressure sensor for measuring the surrounding earth pressure on the outside thereof, and the casing pipe is provided on the inside thereof. It is characterized in that a pressure sensor for measuring the internal air pressure is provided, and an air supply port for sending compressed air is provided inside the pressure sensor.
[0016]
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, a configuration is provided in which an earth pressure gauge for measuring a penetration pressure of a casing pipe is provided at the tip of the tip cover .
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments. The same functional components as those of the related art are denoted by the same reference numerals.
[0020]
FIG. 1 is a sectional view of a tip portion of the sand pile forming device of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. FIG. 2 is a sectional view taken along line CC of FIG. 1. This sand pile forming device has a ball valve type tip cover 12 attached to the tip (lower end in FIG. 1) of a casing pipe 11, and improves soft ground such as a clayey layer deposited on the sea floor or the like. At this time, it is used to form a sand pile in this soft ground.
[0021]
The casing pipe 11 is a cylindrical one having a constant inner diameter filled with sand for being poured into soft ground in a vertical state, and a nozzle part 21 for jetting an air jet has a wall surface inside thereof. It is provided through. The nozzle 21 discharges an air jet downward. Further, a valve seat portion 14 with which a ball valve, which will be described later, is pressed is provided on the inner periphery of the distal end of the casing pipe 11.
[0022]
The valve seat portion 14 has an upper surface portion 14a inclined downward from the inner peripheral surface of the casing pipe 11 toward the axial center, and extends downward on the inner peripheral side of the upper surface portion 14a in parallel with the inner peripheral surface of the pipe. And a tapered lower surface portion 14c which is successively provided below the inner peripheral surface portion 14b and successively approaches the inner peripheral side of the pipe. That is, the lower surface portion 14c is in a state of protruding upward in an arc shape. As shown in FIG. 2, the valve seat portion 14 is reinforced by a plurality of ribs 14d provided radially around the valve seat portion 14, and is fixed by being in contact with the inner periphery of the casing pipe 11 via the ribs 14d. ing.
[0023]
The distal end lid 12 is configured such that a ball valve 16 which is in pressure contact with the valve seat portion 14 is vertically movably housed in a distal end lid case 13 having a hollow truncated cone shape. The end cover case 13 is provided with a plurality of ribs 15 (four in the illustrated example) so as to protrude inward on an inner peripheral surface thereof. It is in contact with the tip (the lower end in FIG. 1) of the casing pipe 11. The inner end of the rib 15 is a vertical portion 15a whose upper half is vertically continuous with the inner peripheral surface of the casing pipe 11, and is gradually shifted toward the axial center as the lower half becomes lower. There are two inclined sections 15b and 15c.
[0024]
A reinforcing cylinder 20 is fitted on the outer peripheral surface of the lower end of the end cover case 13. Inside the reinforcing cylinder 20, a pair of inverted trapezoidal reinforcing members 18, 18 are provided in a shape combined in a substantially cross shape in a plan view, and the support base portion 17 is protruded upward from the intersection. And a valve receiving portion 19 having an upper surface curved in an arc shape on the support base portion 17.
[0025]
The ball valve 16 is hollow so as to have a specific gravity smaller than that of the clay soil (silt), and is normally mounted on the valve receiving portion 19. When it enters the case 13, it rises with the clayey sand and comes into pressure contact with the valve seat 14, thereby closing the lower end of the casing pipe 11.
[0026]
Here, in the sand pile forming device of the present invention, an earth pressure sensor S1 for measuring the surrounding earth pressure is provided outside the tip cover case 13 formed in a hollow substantially truncated cone shape. A pressure sensor S2 for measuring the pressure inside the tip cover case 13 facing the sensor S1 is provided. Further, an earth pressure gauge S3 for measuring a penetration pressure when the casing pipe 11 is driven is provided at a tip (lower end in FIG. 1) of the tip lid 12, that is, below an intersection of the reinforcing member 18.
[0028]
The sand pile forming device of the present invention has the above configuration.
[0029]
Next, a method for forming a sand pile according to the present invention using the sand pile forming apparatus will be described by taking as an example a case where a sand pile is formed on soft ground on the sea floor. First, as shown in FIG. 5, when the tip of the sand pile forming device is put into seawater, seawater enters into the tip cover case 13 from the lower end opening. At this time, if seawater enters to some extent, the air pressure inside the seawater increases, so that the seawater does not enter the casing pipe 11 above the valve seat portion 14.
[0030]
Then, when the apparatus is further lowered from this state, the tip cover 12 eventually reaches the soft clayey soil layer 31 and penetrates into it. When the tip lid 12 penetrates into the clay soil layer 31 in this manner, clay soil enters through the lower end opening of the tip lid case 13, and the ball valve 16 having a lower specific gravity than the clay soil pushes up. As shown in FIG. 6, it comes into pressure contact with the lower surface of the valve seat 14. Therefore, the lower end of the casing pipe 11 is closed, and the clay soil is prevented from entering the casing pipe 11.
[0031]
At this time, if the amount of penetration of the tip lid 12 into the clayey soil layer 31 increases, the buoyancy received by the ball valve 16 also increases.
[0032]
In this way, when the tip lid 12 passes through the clay soil layer 31 and penetrates into the hard soil layer 32 below the clay soil layer 31 as shown in FIG. The sand S is put into the casing pipe 11 in this state because it receives a greater buoyancy and presses against the valve seat portion 14. The amount of the sand S to be charged is such that the ball valve 16 does not descend due to its own weight.
[0033]
When sand S is put into the casing pipe 11 so that the ball valve 16 does not descend, the tip of the sand S penetrates further into the hard earth layer 32. As a result, since a larger buoyancy acts on the ball valve 16, sand S can be put into the casing pipe 11, and sand S is added so that the ball valve 16 does not descend. In this manner, while alternately repeating the introduction of the sand S into the casing pipe 11 and the penetration of the sand S into the hard soil layer 32, as shown in FIG. The entire device is penetrated until it reaches the ground 33 having a predetermined strength.
[0034]
At this time, in the sand pile forming device of the present invention, the measured values of the earth pressure sensor S1 and the pressure sensor S2 are adjusted so that the pressure in the tip cover case 13 corresponds to the surrounding earth pressure that changes with the penetration. In contrast, compressed air is sent into the front end lid case 13 from an air supply port (not shown).
[0035]
When the end cover 12 reaches the predetermined ground 33 in this way, the entire device is pulled upward. At this time, in the sand pile forming apparatus of the present invention, compressed air is supplied from an air supply port (not shown) opened in the tip lid case 13 so that the pressure in the tip lid case 13 becomes substantially equal to the surrounding earth pressure. Is supplied, the air pressure in the cavity (see reference numeral 34 in FIG. 9) formed on the lower side of the end cover case 13 with this extraction is also kept equal to the surrounding earth pressure. Therefore, this cavity does not collapse.
[0036]
Further, in conjunction with the drawing, compressed air is introduced into the casing pipe 11 and an air jet is jetted from the nozzle portion 21, whereby the sand S put into the casing pipe 11 moves downward. The ball valve 16 that has been pressurized and pressed against the valve seat 14 is pushed down. Accordingly, the lower end of the casing pipe 11 is opened, and the sand in the casing pipe 11 passes through the gap between the ball valve 16 and the tip cover case 13 from the valve seat portion 14 and as shown by the arrow in FIG. It is discharged into the lower cavity 34.
[0037]
At this time, in the sand pile forming apparatus of the present invention, the tip lid case 13 is formed in a hollow truncated cone shape with the lower end expanded, so that the sand S is smoothly discharged. The reason is that, when the ball valve 16 is lowered, the gap through which sand is formed between the periphery of the ball valve 16 and the inner surface of the tip lid case 13 becomes wider than in the case of the cylindrical tip lid case. This is because the friction generated between S and the inner surface of the tip cover case 13 is almost eliminated.
[0038]
The reason why the friction disappears is as follows.
[0039]
That is, in the case of the conventional cylindrical tip cover case, as shown in FIG. 11, when the inside is filled with the sand S to the height H, as shown in FIG. 12, the function of the sand weight and the internal friction angle of the sand is obtained. A horizontal force P expressed as This P is inclined upward by δ due to friction between the sand and the inner wall surface of the case. When decomposed into vertical and horizontal directions of P with respect to the wall, the force P _L acting horizontally on the force P _N and the wall that acts vertically on the wall, respectively. The frictional force P _NF is upwardly occur horizontally to the wall surface by the friction sand and wall force P _N acting vertically on the wall. In general, P _NF> P _L, and the sand is an obstacle to the movement or impossible move downward.
[0040]
On the other hand, in the case of a hollow frusto-conical end cover case, as shown in FIG. 13, when sand S is packed in the inside thereof to a height H, as shown in FIG. A horizontal force, P, expressed as a function of the angle of friction occurs, which is likewise inclined upward by δ due to the friction between the sand and the inner wall of the case. However, when the wall surface is inclined by θ with respect to the vertical direction, the force PN acting on the wall surface in the vertical direction becomes smaller than that in the case of the cylindrical shape, and the force P _N acting on the wall surface in parallel becomes smaller. _L is larger than in the case of a cylindrical shape. Even smaller frictional force P _NF acting horizontally on the wall by friction sand and wall force P _N acting vertically on the wall. The inclination angle of the P _{NF <P L} there by the magnitude of the inclination angle θ of the wall surface, resulting frictional force sand and the wall apparently, because zero.
[0041]
When the sand pile forming device is pulled out from the hard earth and sand layer in this manner, the sand S charged into the casing pipe 11 is discharged downward through the tip cover 12 and formed below the sand S. Sand S is filled in the cavity 34 thus formed. When the casing pipe 11 is pulled out over a predetermined length, the casing pipe 11 is pushed down again so as to penetrate the discharged sand again. At this time, as shown in FIG. 10, the ball valve 16 is pushed up by the sand that has penetrated into the end cover case 13, presses against the valve seat portion 14, and closes the lower end of the casing pipe 11. Therefore, the sand put into the cavity formed in the earth and sand layer is pressed by the tip cover 12 and expanded in diameter as shown in FIG.
[0042]
At this time, in the sand pile forming apparatus of the present invention, the penetration pressure of the casing pipe 11 is measured by the earth pressure gauge S3 attached to the tip of the tip cover 12, and the penetration pressure becomes a predetermined pressure according to the soil quality. It is controlled to. Therefore, the sand pressed by the re-penetration of the casing pipe 11 is a sand pile having a predetermined outer diameter and a predetermined length, and further having a predetermined pressure density.
[0043]
Thereafter, by repeating the same operation, a sand pile SP having a predetermined outer diameter and a predetermined density is formed in the hard earth layer 32 and the clay earth layer 31 as shown in FIG.
[0044]
As described above, in the sand pile forming device according to the first aspect of the present invention, the tip cover case constituting the outside of the ball valve type tip cover has a substantially frusto-conical shape with a widened tip. In addition to providing an earth pressure sensor on the outside, a pressure sensor on the inside, and an air supply port for sending compressed air to the inside, so that when removing the casing pipe from the ground, sand is discharged. In addition to smoothing, the air pressure inside the sand can be controlled so as not to collapse the cavity filled with sand, and there is an effect that a desired sand pile is reliably formed.
[0045]
According to the second aspect of the present invention, the earth pressure gauge for measuring the penetration pressure of the casing pipe is provided at the tip of the tip cover. There is an effect that the diameter expansion and compaction work can be easily and accurately performed based on the measured value of the earth pressure gauge.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a main part of an embodiment of a sand pile forming device according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA of FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 1;
FIG. 4 is a sectional view taken along line CC of FIG. 1;
FIG. 5 is a schematic cross-sectional view showing one step of a use state of the sand pile forming device of the present invention.
FIG. 6 is a schematic cross-sectional view showing one process of a use state of the sand pile forming device of the present invention.
FIG. 7 is a schematic cross-sectional view showing one process of a use state of the sand pile forming device of the present invention.
FIG. 8 is a schematic cross-sectional view showing one step of a use state of the sand pile forming device of the present invention.
FIG. 9 is an explanatory sectional view showing a sand pile forming process .
FIG. 10 is a cross-sectional view showing a state where a sand pile is formed .
FIG. 11 is a simplified cross-sectional view showing a state where a predetermined amount of sand is put in a cylindrical case.
FIG. 12 is an explanatory diagram showing stress acting on the inner wall surface of the case shown in FIG. 11;
FIG. 13 is a simplified sectional view showing a state where a predetermined amount of sand is put in a hollow truncated cone-shaped case.
FIG. 14 is an explanatory diagram showing stress acting on the inner wall surface of the case shown in FIG.
FIG. 15 is a simplified sectional view showing a conventional example of a sand pile forming device.
FIG. 16 is a simplified sectional view showing another conventional example of a sand pile forming device.
[Explanation of symbols]
Reference Signs List 11 casing pipe 12 tip lid 13 tip lid case 14 valve seat 15 rib 16 ball valve 17 support base 18 reinforcing member 19 valve receiving part 20 reinforcing cylinder 21 nozzle part 34 cavity S1 earth pressure sensor S2 pressure sensor S3 earth pressure gauge SP sand Pile

Claims (2)

A casing pipe provided with a nozzle for introducing compressed air therein, and a tip lid attached to the tip of the casing pipe, wherein the tip lid has a generally frustoconical shape with a widened tip. A case, a ball valve housed in the tip cover case so as to be vertically movable, and a valve seat that contacts the ball valve and seals the inside of the tip of the casing pipe. An earth pressure sensor for measuring the surrounding earth pressure is provided on the outside, and a pressure sensor for measuring the air pressure in the tip cover case is provided on the inside thereof, and air for sending compressed air therein is provided. A sand pile forming device provided with a supply port. The sand pile forming device according to claim 1, wherein an earth pressure gauge for measuring a penetration pressure of the casing pipe is provided at a tip of the tip cover.

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