KR20020033727A - Method and device for forming sand pile - Google Patents

Abstract

According to the present invention, the tip cover case (13) provided at the tip of the casing pipe (11) has a conical trapezoidal tip cover case (13), and a ball valve (16) housed in the tip cover case (13) so as to be movable. ) And a valve seat portion 14 in contact with the ball valve 16 to keep the inside of the tip of the casing pipe 11 closed. And the tip cover case 13 is provided with the earth pressure sensor S1 which measures the surrounding earth pressure on the outer side, and the pressure sensor S2 which measures the air pressure in the casing pipe 11 inside, Inside it was installed an air supply port for sending compressed air.

Description

Sand pile formation method and its device {METHOD AND DEVICE FOR FORMING SAND PILE}

Conventionally, as a method and an apparatus for forming such a sand pile, there existed what was shown by Japanese Patent No. 2791914.

The sand pile forming apparatus shown in this patent has a sand pile having a vibro hammer 46 at its head and a sand hopper 42 and a compressed air supply pipe 43 disposed thereon. On the lower part of the composition hollow tube 41, the downward cylinder 44 driven by the supply of pressurized water, and the plurality of sand compactor and discharge wings 45 driven in the vertical direction by the downward cylinder 44 are radially disposed. It is installed. 47 denotes a pressurized water supply pipe for supplying pressurized water to the downward cylinder 44.

And sand pile formation method using this apparatus is as follows.

First, the hollow tube 41 is driven to the predetermined depth with the vibro hammer 46, sand is injected from the hopper 42, and compressed air is blown into the compressed air supply pipe 43. At this time, the air pressure in the hollow tube 41 is such that the surrounding soil does not flow into the pipe, and the air pressure in the pipe should never be a large air pressure from which the sand injected into the pipe is discharged out of the pipe.

In this state, pressurized water is injected into the cylinder 44 to move the discharge blade 45 up and down at a plurality of times at a constant speed, thereby leaving a part of the injection sand in the hollow tube 41 and in most cases contact resistance with the discharge blade 45. By force is extruded to the bottom of the hollow tube 41 and discharged. At this time, the hollow tube 41 is also taken out from the ground by a predetermined length. The sand discharged thereby is firmly compacted by the discharge blade (45).

When sand is discharged into the soft ground in this way, the pressure in the pipe 41 is released, and a predetermined amount of sand is introduced again from the hopper 42 to balance with earth pressure according to the displacement of the lower end of the hollow pipe 41. After the discharge and compaction of the sand and the extraction of the predetermined length of the hollow tube 41 by the internal pressure of the tube and the operation of the cylinder 44 to maintain the pressure, the operation is repeated to form the sand pile.

The degree of pressurization described above is determined based on the earth pressure by calculating the earth pressure corresponding to the depth of the bottom of the hollow tube 41 in advance.

As another sand pile forming apparatus, there is one shown in Japanese Patent Application Laid-Open No. 8-1060 filed by the present applicant.

As shown in FIG. 16, this is a cylindrical shape in which the ball valve 16 having a predetermined specific gravity can be moved up and down at the distal end of the casing pipe 11 in which the nozzle 21 for introducing compressed air is provided therein. The tip cover case 13 'is provided, and the valve seat portion 14 which is closed by the ball valve 16 is provided at the opening of the tip of the casing pipe 11 (lower in Fig. 16). When the casing pipe 11 is driven in, the ball valve 16 closes the tip of the casing pipe 11 so as to prevent infiltration of soil. When the sand for sand pile formation is discharged, the ball is operated under pressure of sand and compressed air. The valve 16 is separated from the valve seat portion 14 so that a gap for sand discharge is formed between the tip cover case 13 '.

In the conventional sand pile forming apparatus shown in FIG. 15, a sand compactor and a discharging wing can be installed on the front end side of the hollow tube so as to be movable upward and downward, and a downward cylinder for driving the discharging wing must be provided. In addition, they may be damaged by the sand introduced into the hollow tube or the pressure when the hollow tube is inserted, and at the same time, there is a problem that it may be an obstacle during sand discharge. In addition, this apparatus requires a supply device for pressurized water to operate a downward cylinder, and an auxiliary device such as a control device, which causes a problem that the facility becomes large and requires extra time for its preparation and work.

In the method of forming a sand pile using this apparatus, a predetermined amount of sand is introduced into a hollow tube, a compressed air of a predetermined pressure is blown, and a discharge wing is shaken in this state, so that sand is firmly fixed and predetermined The work of extracting the hollow tube by the length had to be repeated and the work efficiency was very bad. In addition, the air pressure in the pipe is controlled to maintain the balance with the earth pressure according to the displacement of the lower end as the hollow tube is pulled out, but this earth pressure is based on the calculated value, so it is always optimal according to the actual ground situation. There was a fear that the desired work could not be done because it did not become the air pressure of.

In addition, in the apparatus shown in Fig. 16, when the casing pipe is driven, the tip is closed by a ball valve, so there is no danger of seawater or clay soil invading therein. On the other hand, the ball valve is obstructed when sand is discharged. There was a problem that the discharge takes time.

The present invention solves the problems that the conventional sand pile forming method and apparatus have, and in various soft grounds having different conditions, a method for reliably and efficiently forming a sand pile having a predetermined strength and diameter; It is an object to provide an apparatus for use in the method.

The present invention relates to a method of forming a sand pile for improving the ground in a soft ground, and an apparatus for forming a sand pile by this method.

1 is a longitudinal sectional view of an essential part of an embodiment of a sand pile forming apparatus according to the present invention;

2 is a cross-sectional view taken along the line A-A of FIG. 1;

3 is a cross-sectional view taken along line B-B of FIG. 1;

4 is a cross-sectional view taken along the line C-C in FIG. 1;

Figure 5 is a schematic cross-sectional view showing one step of the use state of the sand pile forming apparatus of the present invention,

Figure 6 is a schematic cross-sectional view showing one step of the use state of the sand pile forming apparatus of the present invention,

Figure 7 is a schematic cross-sectional view showing one step of the use state of the sand pile forming apparatus of the present invention,

8 is a schematic cross-sectional view showing one step of a use state of the sand pile forming apparatus of the present invention;

9 is a cross-sectional explanatory view showing a sand pile forming method of the present invention;

10 is a cross-sectional explanatory view showing a sand pile forming method of the present invention;

11 is a schematic cross-sectional view showing a state in which a predetermined amount of sand is put into a cylindrical case;

12 is an explanatory diagram showing a stress acting on the inner wall surface of the case shown in FIG. 11;

13 is a schematic cross-sectional view showing a state in which a predetermined amount of sand is put into a hollow conical trapezoidal case;

14 is an explanatory diagram showing a stress acting on a case inner wall surface of the one shown in FIG. 13;

15 is a schematic cross-sectional view showing a conventional example of a sand pile forming apparatus;

16 is a schematic cross-sectional view showing another conventional example of the sand pile forming apparatus.

In the sand pile forming method of the present invention, a casing pipe having a ball valve type tip cover is inserted into a soft ground, and sand is introduced into the casing pipe, leaving only the sand pile formed by the injected sand in the ground. In the method of forming the sand pile to be pulled out, when the casing pipe is pulled out of the ground, the air pressure inside the tip cover is controlled to be equal to the earth pressure measured around it, thereby not breaking down the cavity formed by the casing pipe. It is to fill the sand.

In the sand pile forming method in which sand discharged from a casing pipe having a tip cover is secured by reintroduction of the casing pipe and expanded in diameter, the pressure at the time of reintroducing the casing pipe is applied to the casing pipe. By controlling based on the measured value of the earth pressure gauge installed at the tip, the sand pile having the desired strength and diameter was formed.

The sand pile forming apparatus of the present invention is a sand pile forming apparatus comprising a casing pipe provided with a nozzle for introducing compressed air therein and a tip cover provided at the tip of the casing pipe, wherein the tip cover has a wide end. A tip cover case having a substantially conical trapezoid shape, a ball valve housed in the tip cover case so as to be movable up and down, and a valve seat portion in which the ball valve is in contact with the tip of the casing pipe to be sealed. A pressure sensor for measuring the air pressure in the casing pipe was installed inside the outside, and an air supply port for sending compressed air was installed inside the inside.

Moreover, the earth pressure gauge which measures the penetration pressure of a casing pipe was installed in the front-end | tip of the front cover of the said apparatus.

In order to explain the present invention in more detail, it will be described according to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same functional part as the conventional thing here.

1 is a cross-sectional view of a tip portion of the sand pile forming apparatus of the present invention, and FIGS. 2, 3, and 4 are cross-sectional views taken along line A-A, line B-B, and line C-C, respectively. This sand pile forming apparatus is provided with a ball valve type tip cover 12 at the tip of the casing pipe 11 (lower in Fig. 1), and is used to improve the soft ground such as the clay layer deposited on the sea floor. Used to form sand piles in soft ground.

The casing pipe 11 is a tubular shape having a constant inner diameter filled with sand for placing in a soft ground in a vertical state, and a nozzle portion 21 for blowing an air jet penetrates a wall thereof. . The nozzle portion 21 is configured to discharge the air jet downward. Moreover, the valve seat part 14 which the ball valve described later press-contacts is provided in the inner periphery of the front-end | tip of this casing pipe 11.

The valve seat portion 14 is an axial side from the inner circumferential surface of the casing pipe 11, and an upper surface portion 14a inclined downward, and an inner circumferential surface of the pipe on the inner circumferential side of the upper surface portion 14a. An inner peripheral surface portion 14b which protrudes downward in parallel and protrudes downward, and further has a tapered lower surface portion 14c adjacent to the inner circumferential side of the pipe in sequence in succession below the inner peripheral surface portion 14b. That is, this lower surface part 14c is in the state which protruded upward in circular arc shape. As shown in Fig. 2, the valve seat portion 14 is reinforced with a plurality of ribs 14d radially installed around the valve seat portion 14, and is fixed in contact with the inner circumference of the casing pipe 11 via the ribs 14d. have.

The tip cover 12 accommodates the ball valve 16 pressed against the valve seat 14 in the hollow cone-shaped tip cover case 13 so as to be movable upward and downward. The tip cover case 13 is formed by protruding a plurality of ribs 15 (four in the illustrated example) so as to protrude inwardly on an inner circumferential surface thereof, the upper end of which is the casing pipe. It is in contact with the front end (lower part in FIG. 1) of (11). In addition, the inner end of the rib 15 becomes a vertical portion 15a that is vertically continuous with the inner circumferential surface of the casing pipe 11 in the up and down direction, and the lower half is gradually lowered toward the axial side. It consists of inclined parts 15b and 15c of two steps which inclined.

A reinforcing tube 20 is fitted to the lower outer circumferential surface of the tip cover case 13.

Inside the reinforcing tube 20, a pair of reinforcing trapezoidal members 18 and 18 of an inverted trapezoid shape are installed in a cross-sectional shape in plan view, and the support base portion 17 protrudes upward from the intersection point. And a valve receiving portion 19 whose upper surface is curved in an arc shape is provided on the support portion 17.

The ball valve 16 is hollow so as to have a specific gravity smaller than that of clay soil (silt), and is normally placed on the valve receiving portion 19, and when clay soil enters the tip cover case 13 during construction, The lower end of the casing pipe 11 is sealed by floating by the clay soil and pressure-contacting the valve seat 14.

In the sand pile forming apparatus of the present invention, the earth pressure sensor (S1) for measuring the surrounding earth pressure on the outer side of the tip cover case 13 formed in a hollow substantially conical trapezoidal shape, and at the same time, the earth pressure sensor ( Inside the tip cover case 13 facing S1), a pressure sensor S2 for measuring the pressure therein is provided. In addition, a pressure gauge S3 for measuring the penetration pressure when the casing pipe 11 is driven is provided at the front end of the tip cover 12 (the lower end in FIG. 1), that is, at the bottom of the intersection point of the reinforcing member 18. Doing.

In addition, although not shown, the front cover case 13 is provided with an air supply port for sending compressed air therein.

The sand pile forming apparatus of the present invention has the above configuration.

Next, the sand pile forming method of the present invention using the sand pile forming apparatus will be described as an example of forming sand piles on the soft ground of the sea bed.

First, as shown in FIG. 5, when the front-end | tip of a sand pile forming apparatus is put in seawater, seawater invades from the lower end opening in the front cover case 13. At this time, if the seawater intrudes to some extent, the air pressure inside thereof increases, so that the seawater does not enter the casing pipe 11 above the valve seat portion 14.

When the device is further lowered from this state, the tip cover 12 finally reaches the soft clay soil layer 31 and is introduced into it. When the tip cover 12 is introduced into the clay soil layer 31 in this way, clay soil enters from the lower end opening of the tip cover case 13, and a ball valve 16 having a specific gravity smaller than that of the clay soil is pushed up. As shown in FIG. 3, the valve seat portion is in pressure contact with the lower surface portion of the valve seat portion 14. Therefore, the lower end of the casing pipe 11 is blocked and clay soil is prevented from invading into the casing pipe 11.

At this time, when the penetration amount of the tip cover 12 into the clay soil layer 31 increases, the buoyancy force applied to the ball valve 16 also increases.

In this way, when the tip cover 12 passes through the clay soil layer 31 and penetrates into the hard soil layer 32 below the clay soil layer 31, the ball valve 16 generates a greater buoyancy force. In this state, sand S is introduced into the casing pipe 11 because it is pressed against the valve seat 14. In addition, the amount of sand S injected at this time is such that the ball valve 16 does not fall by the weight of sand.

Then, when sand S is introduced into the casing pipe 11 so that the ball valve 16 does not descend, the tip thereof is again introduced into the hard soil layer 32. As a result, a greater buoyancy acts on the ball valve 16, so that sand S can be introduced into the casing pipe 11, so that sand S is added so that the ball valve 16 does not fall. Input. In this way, while the input of the sand S into the casing pipe 11 and the penetration into the hard soil layer 32 are alternately repeated, as shown in FIG. 8, the front cover 12 is lower than the hard soil layer 32. The entire apparatus is introduced until it reaches the ground 33 having a predetermined strength of.

At this time, in the sand pile forming apparatus of the present invention, the illustration of the earth pressure sensor S1 and the pressure sensor S2 is omitted, so that the pressure in the tip cover case 13 corresponds to the earth pressure that changes according to the penetration. Compressed air is sent from the air supply port into the tip cover case 13.

And when the front cover 12 reaches the predetermined ground 33 in this way, the whole apparatus will be pulled out upward. At this time, in the sand pile forming apparatus of the present invention, since compressed air is supplied from an air supply port (not shown) opened in the tip cover case 13 so that the pressure in the tip cover case 13 is approximately equal to the surrounding earth pressure. With this extraction, the air pressure in the cavity (see reference numeral 34 in Fig. 9) formed under the tip cover case 13 is also kept the same as the earth pressure around it. Therefore, this cavity does not collapse.

In addition, compressed air is introduced into the casing pipe 11 in conjunction with the extraction, and an air jet is injected from the nozzle portion 21, whereby sand S injected into the casing pipe 11 is pressed downward. As a result, the ball valve 16 pressed against the valve seat 14 is pushed down. Accordingly, the lower end of the casing pipe 11 is opened so that the sand in the casing pipe 11 is indicated by an arrow in FIG. 9 through the gap between the ball valve 16 and the tip cover case 13 from the valve seat portion 14. Likewise discharged into the cavity 34 below it.

At this time, in the sand pile forming apparatus of the present invention, since the tip cover case 13 is formed in a hollow conical trapezoidal shape with a wide bottom, the sand S is smoothly discharged. The reason is that when the ball valve 16 is lowered, the passage gap of sand formed between the periphery thereof and the inner surface of the tip cover case 13 is wider than that of the cylindrical tip cover case, and the sand S and This is because friction generated between the inner surfaces of the tip cover case 13 is almost eliminated.

The reason why this friction disappears is as follows.

That is, in the case of the conventional cylindrical tip cover case, as shown in FIG. 11, when the sand S is filled by the height H, the weight of the sand and the internal friction angle of the sand as shown in FIG. The horizontal direction force P is shown as follows. This P tilts upward by friction between sand and the inner wall of the case. When P is decomposed in the vertical direction and the horizontal direction with respect to the wall surface, the force P _N acting vertically on the wall surface and the force P _L acting horizontally on the wall surface, respectively. The friction force of P _NF is generated in the horizontal direction on the wall by the friction between sand and the wall due to the vertical force P _N acting on the wall. At this time, it is generally P _NF > P _L and sand cannot be moved downward or it is hindered to move.

On the other hand, in the case of the hollow conical trapezoidal tip cover case, as shown in Fig. 13, when the sand S is filled by the height H, as shown in Fig. 14, the weight of the sand and the internal friction angle of the sand are shown. The horizontal force P, which is expressed as a function of P, arises, and this P is similarly tilted upward by the friction between the sand and the inner wall of the case. However, since the wall surface is inclined by θ with respect to the vertical direction, the force P _N acting in the vertical direction with respect to the wall becomes smaller than that of the cylindrical form, whereas the force P _L acting in parallel with the wall surface becomes cylindrical. Larger than the case. In addition, the friction force P _NF acting horizontally on the wall by the friction between sand and the wall is also reduced by the force P _N acting on the wall surface vertically. This is because the inclination angle at which P _NF <P _L exists due to the magnitude of the inclination angle θ of the wall surface, and as a result, the frictional force between the sand and the wall surface is apparently zero.

In this way, the sand pile forming apparatus is pulled out of the hard soil layer, and the sand S introduced into the casing pipe 11 is discharged downward through the tip cover 12, and sand (in the cavity 34 formed below) is removed. S) is charged. Then, when the casing pipe 11 is pulled out over a predetermined length, this time the casing pipe 11 is pushed down again so as to penetrate into the discharged sand. At this time, as shown in FIG. 10, the ball valve 16 is pushed up by the sand which penetrated into the tip cover case 13, is pressed against the valve seat part 14, and the lower end of the casing pipe 11 is sealed off. Therefore, the sand thrown into the cavity formed in the soil layer is pressurized by the tip cover 12, and as shown in FIG. 10, the diameter becomes wider.

At this time, in the sand pile forming method of the present invention, the penetration pressure of the casing pipe 11 is measured by the earth pressure sensor S3 provided at the tip of the tip cover 12, so that the penetration pressure is a predetermined pressure according to the soil quality. It is controlled. Therefore, the sand pressurized by the re-penetration of the casing pipe 11 becomes a sand pile having a predetermined outer diameter, a predetermined length, and a predetermined density.

The same operation is repeated below, and as shown in FIG. 10, the sand pile SP of predetermined outer diameter and density is formed in the hard soil layer 32 and the clay soil layer 31. As shown in FIG.

As described above, in the method of forming the sand pile of the present invention, the sand pile can be formed by filling sand therein without breaking down the cavity formed by the casing pipe, and the sand pile is hardened to a desired strength and diameter. It is also useful for improving fragile soft grounds such as seabeds.

In addition, the sand pile forming apparatus of the present invention, despite the simple configuration, the sand pile is surely formed, and the sand is discharged smoothly at this time, thereby improving work efficiency, thereby reducing work days, construction costs, labor costs, etc. Can be. Therefore, for these reasons, there is a possibility that the introduction into the area where the ground improvement could not be performed is promoted.

Claims (4)

Sand pile is formed by driving a casing pipe having a ball valve type end cover in the soft ground, and putting sand into the casing pipe, and leaving only the sand pile formed by the injected sand in the ground and extracting the casing pipe. In the method, When the casing pipe is removed from the ground, the air pressure inside the tip cover is controlled to be equal to the earth pressure measured around it, thereby filling sand into the cavity without breaking down the cavity formed by the casing pipe. Pile formation method. In the sand pile forming method in which the sand discharged from the casing pipe having the tip cover is firmly solidified by reintroduction of the casing pipe, and the diameter thereof is widened. A method of forming a sand pile, wherein the pressure at the time of re-injecting the casing pipe is controlled based on a measured value of a tonometer provided on the tip cover to form a sand pile having a desired strength and diameter. A casing pipe provided with a nozzle for introducing compressed air therein; Comprising a tip cover installed on the tip of the casing pipe, The tip cover includes: a tip cover case having a substantially conical trapezoidal shape with a wide open tip; A ball valve housed in the front cover case so as to be movable; And a valve seat portion in contact with the ball valve to keep the inside of the casing pipe closed. The tip cover case is provided with an earth pressure sensor for measuring the surrounding earth pressure on the outside thereof, and a pressure sensor for measuring the air pressure in the tip cover case is provided therein, and inside the air for sending compressed air. Sand pile forming apparatus characterized in that the supply port is installed. The method of claim 3, wherein A sand pile forming apparatus, characterized in that a pressure gauge for measuring the penetration pressure of the casing pipe is installed at the tip of the tip cover.