JP2022017027A - Vibro unit, ground improvement device, and ground improvement method - Google Patents

Abstract

To provide a vibro unit, a ground improvement device, and a ground improvement method suitable for improving a construction efficiency in ground improvement since improved piles of a predetermined diameter can be created accurately.SOLUTION: A vibro unit 80 has a silo tube 10 to which materials for improved pile building are supplied, and a vibro tool 20 attached to one end of the silo tube 10. The vibro tool 20 comprises a vibroflot 30 that generates horizontal vibration and a feeder 40 that is attached to the vibroflot 30 and connected to the silo tube 10. At the tip of the vibro tool 20 in the direction of ground penetration, there is a tip guide tube 50 having a hollow with a cross-sectional area larger than that of the hollow at the tip of the feeder 40.SELECTED DRAWING: Figure 4

Description

The present invention relates to a vibro unit, a ground improvement device, and a ground improvement method.

In the vibro flotation method, which is one of the ground improvement methods, the ground is a vibro unit having a silo tube that allows the input material for making improved piles to flow downward and a vibro tool attached to the lower end of the silo tube. The method of penetrating inside is applied. More specifically, the Vibro tool is equipped with a Vibro Flot that generates horizontal vibration, and the Vibro unit is penetrated into the ground while generating horizontal vibration in the Vibro Flot, which is an improvement from the feeder that constitutes the Vibro unit. Improved piles are constructed by supplying materials for pile construction into the ground.
In the vibro flotation method, a so-called top feed method is adopted in which materials for improving pile construction are replenished from the ground surface, and for that purpose, whether or not the pile diameter at each depth satisfies the predetermined pile diameter, in other words. , It is difficult to specify whether or not the material for improving pile construction supplied in the ground is sufficiently distributed at each depth.
Further, in the vibro flotation method, a method is also performed in which the vibro unit is penetrated to a predetermined depth and then the vibro unit is pulled out to the ground to form a cavity, and the cavity is filled with a material for making improved piles. However, when the ground to be improved is, for example, soft sandy ground, the earth and sand may fall into the cavity due to the collapse of the hole wall in response to the withdrawal of the vibro unit, and the created diameter at the time of penetrating the vibro unit may not be secured. .. In addition, in this method, since the vibro unit is pulled out to the ground every time the improved pile is constructed at each depth, it is necessary to re-penetrate the vibro unit from the ground at each depth of construction, which has a problem in terms of construction efficiency. ing. Issues related to construction efficiency lead to extension of construction period and increase in construction cost, and this issue becomes more prominent as the length of piles increases and the number of piles increases.
As described above, the vibro flotation method includes problems related to the construction accuracy and construction efficiency of the improved pile having a predetermined diameter.

Here, Patent Document 1 discloses a vibration compaction device including a vibration portion and a rod portion. More specifically, an air jet as compressed air for excavation is ejected from the tip air outlet of the vibrating part, and in order to assist the penetration of the vibrating device by this air jet, the outer peripheral surfaces of the tip air outlet face each other. It is a device that injects a separate air jet, which is compressed air for diffusion, by providing an air blowout tube around the tip at the position. In the vibration compaction method using this device, the vibrating part is vibrated, an air jet for excavation is ejected from the tip air outlet, and intrusion is performed from the air outlet pipe around the tip and the outer air outlet pipe. An air jet for auxiliary promotion and an air jet for holding the hole wall are ejected and penetrated, then the injection amount of the air jet for excavation is reduced, and the filling material is put into the gap while pulling out the vibration compaction device. I'm supposed to do it.

Japanese Unexamined Patent Publication No. 5-339933

According to the vibration compaction device described in Patent Document 1, it is said that the penetration efficiency of the vibro flot can be improved, but the penetration of the vibration device and the holding of the hole wall are performed by a plurality of types of air injected into the ground. And, when the vibrating device is pulled out, the injection amount of a plurality of types of air is reduced, so that it is difficult to control the injection of air. In addition, since the hole wall is held only by the air jet, there is a limit to the hole wall holding, and it is uncertain whether or not an improved pile having a predetermined diameter can be created accurately.

The present invention has been made in view of the above problems, and is a vibro unit suitable for creating an improved pile having a predetermined diameter with high accuracy and improving construction efficiency at the time of ground improvement, a ground improving device, and a ground improving device. The purpose is to provide a method for improving the ground.

In order to achieve the above object, one aspect of the vibro unit according to the present invention is
Silo tubes to which materials for improving pile construction are supplied, and
A vibro unit having a vibro tool attached to one end of the silo tube.
The vibro tool is
It is equipped with a vibro flot that generates horizontal vibration and a feeder that is attached to the vibro flot and communicates with the silo tube.
At the tip of the vibro tool in the ground penetration direction, a tip guide tube having a hollow cross section larger than the hollow cross section of the tip of the feeder is provided.

According to this aspect, for example, a steel having a hollow having a larger cross-sectional area than the hollow cross-sectional area of the tip of the feeder at the tip of the vibro tool formed by the vibro flots and the feeder adjacent to each other in the ground penetration direction. By providing the tip guide tube, it is possible to secure a cavity having a hollow cross-sectional area of the tip guide tube in the ground and fill the cavity with the material for making improved piles. That is, instead of the configuration in which the cavity is held only by air as described above, the cavity created by preventing the hole wall from collapsing with the tip guide tube having a predetermined shape and size can be secured, so that the predetermined diameter can be secured. It will be possible to create improved piles. Further, since the injection control of a plurality of types of air jets is not required, efficient ground improvement can be realized.

Here, the tip guide tube provided at the tip of the vibro tool may be a tube that surrounds the entire tip of the vibro tool, for example, does not surround only a part of the vibro flot, and the vibro tool. It may be a tube that surrounds other parts. Further, as the shape, various shapes such as a cylinder shape, a figure eight shape in which two arcs having the same diameter or different diameters are continuous, or a shape having a substantially eight shape can be applied. In the form in which the tip guide tube does not surround a part of the vibroflot, the tip guide tube does not surround the entire vibroflot, so that the vibration of the vibroflot is directly transmitted to the ground and the material for improving pile construction is used. It becomes possible to secure a cavity having a predetermined diameter to be filled.
Further, the "hollow cross-sectional area at the tip of the feeder" is the "hollow cross-sectional area when the feeder is viewed from below (ground penetration direction)", and in this embodiment, the hollow cross-sectional area of the feeder is used. The hollow cross-sectional area of the tip guide tube is set to a large cross section.
The feeder communicates with the silo tube, for example, the improved pile building material supplied from the hopper provided at the head of the silo tube flows down the silo tube, flows down the lower feeder, and then the tip guide tube. It is supplied into the ground via.

In the present specification, the "predetermined diameter" of the improved pile means the diameter or radius of the improved pile set in the design, and is, for example, a diameter for satisfying the predetermined improvement rate. Further, the "diameter expansion" in the ground improvement method of the present invention described below means that the diameter of a pile having a circular cross section is expanded to increase the area, or the cross section is rectangular or the corners of the rectangle are curved. The cross-sectional area of the filler and the enlarged diameter body created in the ground is expanded, such as the area of the cross-section of the shape is expanded and the area is increased, and the cross-section of the figure eight is expanded and the area is increased. It means to include all things to do.

Further, another aspect of the vibro unit according to the present invention is characterized in that the tip guide tube is provided with a tip fin protruding from the tip of the tip guide tube in the ground penetration direction.

According to this aspect, the penetration performance of the vibro unit, which is a concern due to the provision of the tip guide tube, is due to the further provision of, for example, a steel tip fin protruding from the tip of the tip guide tube in the ground penetration direction. The decrease can be suppressed. That is, by providing, for example, a cylindrical tip guide tube at the tip of the vibro tool in the ground penetration direction, it is possible to secure a filling space (cavity) for the material for making improved piles having a desired diameter, while at the tip in the ground penetration direction. The presence of a tip guide tube rather than a vibrating vibro flot can reduce the penetration performance of the vibro unit. Therefore, for example, by providing a tip fin that protrudes in the ground penetration direction from the tip guide tube for a cylindrical tip guide tube, the tip guide tube is provided based on the ground penetration property of the tip fin. This can effectively suppress the deterioration of the penetration performance of the vibro unit.
Here, the tip fin has a form in which two tapered surfaces are provided so that the center thereof is sharpened at one end of a steel plate or the like, or the steel plate is assembled in a cross shape and the center thereof is sharpened at one end of the cross. There is a form in which a total of four tapered surfaces are provided on each end side so as to be. Then, the tip guide is formed by welding a part of the tip fin to the tip guide tube, or by welding with the tip fin fitted in the groove provided at the tip of the tip guide tube. The tip fin is fixed to the tube.

Further, in another aspect of the vibro unit according to the present invention, an opening and a measuring pulley are provided on the side surface of the silo tube, and a wire extending from the measuring pulley extends into the inside of the silo tube through the opening. A sand level gauge is attached to the tip of the wire,
The sand level gauge is dropped on the top surface of the improved pile building material inside the silo tube, and the amount of movement of the wire at that time is measured by the measuring pulley to build the improved pile. It is characterized in that the amount of materials supplied to the ground is controlled.

According to this aspect, a measuring pulley is provided on the side surface of the silo tube, and a wire extending from the measuring pulley extends from an opening on the side surface of the silo tube to the inside of the silo tube, and a sand level gauge is attached to the tip thereof. As a result, the top position of the improved pile building material can be accurately measured from the amount of movement of the wire when the sand level gauge is dropped on the top surface of the improved pile building material inside the silo tube. Then, by multiplying this measurement result (the amount of change in the height of the top of the improved pile building material) by the cross-sectional area of the silo tube, the amount of decrease in the improved pile building material in the silo tube is calculated. It will be possible to specify the supply amount of materials for improving pile construction inside with high accuracy. As will be described below, in the ground improvement method according to the present invention, after the vibro unit is penetrated to a predetermined depth of the ground, the vibro unit is pulled upward by a predetermined pulling length to form a cavity created by this pulling. The material for making improved piles is filled, and the vibro unit is repeatedly returned downward by a predetermined return length shorter than the predetermined pull-out length to form improved piles. The materials for the improved pile construction will be supplied to the ground. In this construction method, each time the material for improving pile construction is repeatedly filled, the supply amount of the material for improvement pile construction to the ground is controlled according to this embodiment, thereby realizing highly accurate control of the supply amount. can do.
In the form in which a hopper is provided on the head of the silo tube and the material for making improved piles is filled in the silo tube via the hopper, an opening is provided near the head of the silo tube and a wire is provided near the opening. By providing one or more pulleys to guide the movement of the silo tube, the sand level gauge can be reliably dropped to the top of the improved pile building material that is filled up to the vicinity of the head of the silo tube. .. Further, in the management of the supply amount, the measurement data regarding the movement amount of the wire by the measurement pulley is transmitted to the control panel of the cockpit of the heavy machine that suspends the vibro unit, and the material for improving pile construction is reduced in the control panel. The amount (supply amount to the ground) may be calculated, or the measurement data is transmitted to the management computer in the management building in the construction yard, and the reduction amount of the material for improving pile construction is transmitted by the management computer. May be determined.

Further, in another aspect of the vibro unit according to the present invention, a water jet supply pipe is attached from the outer peripheral surface of the silo tube to the outer peripheral surface of the tip guide tube via the outer peripheral surface of the vibro tool.
The water jet is supplied from the tip of the water jet supply pipe to the outer periphery of the tip guide tube.
According to this aspect, by supplying a water jet from the water jet supply pipe on the outer periphery of the tip guide tube, for example, even when a hard layer having an N value of about 20 or more exists in the ground to be improved, the vibro unit. The vibro unit can be reliably penetrated by both its own weight and the crushing force of the water jet.

In addition, another aspect of the vibro unit according to the present invention extends from the outer peripheral surface of the silo tube to the inner surface of the tip guide tube via the outer peripheral surface of the vibro tool and the outer peripheral surface of the tip guide tube. An air jet supply pipe is attached,
The air jet is supplied from the tip of the air jet supply pipe to the inside of the tip guide tube.
According to this aspect, the air jet is supplied from the air jet supply pipe to the inside of the tip guide tube, so that the material for making improved piles in the silo tube can be quickly supplied to the ground and the tip guide tube can be supplied. It is possible to prevent backflow of earth and sand from the tip to the vibro tool.

Further, one aspect of the ground improvement device according to the present invention is
Mobile heavy equipment and
It is characterized by having the vibro unit suspended from the heavy machine via a wire.
According to this aspect, the ground can be improved with the vibro unit hanging down by a mobile heavy machine such as a mobile crane without using a special machine such as a three-point pile driving base machine. Ground improvement work can be realized using heavy machinery, and construction costs can be reduced. In addition, since the improved pile is created by generating horizontal vibration with the vibrof lot, it is possible to suppress both the noise level and the vibration level to a low level unlike the sand compaction pile method (SCP method), for example, and the environment. It will be a ground improvement device with excellent adaptability.

Further, one aspect of the ground improvement method according to the present invention is
An intrusive step of intrusing the vibro unit to a predetermined depth of the ground while generating horizontal vibration using the ground improvement device.
A drawing filling step in which the vibro unit is pulled upward by a predetermined pulling length, and the cavity created by the pulling is filled with the improved pile building material via the tip guide tube to form a filler.
A return step of returning the vibro unit downward by a predetermined return length shorter than the pull-out length, and creating a diameter-expanded body in which the filler is expanded by this return.
It is characterized in that an improved pile having a predetermined diameter is created by repeating the drawing and filling step and the returning step.

According to this aspect, a filler is formed while filling a cavity formed by pulling out a vibro unit upward from a predetermined depth of the ground with a material for creating an improved pile (water permeable material, etc.), and the filler is formed. To create an expanded pile while expanding the diameter to the side, and repeat this to create an improved pile while gradually expanding the diameter of the expanded body. Therefore, create an improved pile with the desired improved diameter. be able to. In addition, since it is an improved method of the so-called bottom feed method, it is easy to control the input amount of the material for making improved piles, which makes it possible to make improved piles with high accuracy.
In addition, since the material for creating improved piles is supplied into the ground while giving horizontal vibration to the ground, and the diameter-expanded body is created while the filler is expanded in the lateral direction, the vibration direction and the diameter-expanded body are created. Since the directions (diameter expansion directions) are the same, it is an improvement method with high construction efficiency. In addition, the ground can be improved with the vibro tool hanging down by a mobile crane or the like without using a special machine such as a three-point pile driving base machine. In addition, by constructing an improved pile made of a permeable material while compacting it with the weight of a vibro tool that vibrates horizontally, it is possible to both increase the density of the ground and dissipate the pore water pressure.
In the drawing and filling step, the tip guide tube is used while adjusting the pulling speed of the vibro unit and the filling timing of the material for improving pile construction (filling timing in relation to the pulling out of the vibro unit) for each soil condition, for example. It is advisable to construct the cavity so that the material for building improved piles is sufficiently filled in the cavity formed.

Further, in the return step, by returning the vibro unit downward by a return length shorter than the pull-out length of the vibro unit in the pull-out filling step, the diameter of the filler can be expanded to create a diameter-expanded body. Then, by repeating the creation of the filler (supply of the material for creating the improved pile), the expansion of the diameter of the filler, and the expansion of the diameter of the expansion body around the filler due to this, the diameter expansion body is gradually expanded. Can be expanded to.

In this return step, by releasing the hanging state of the vibro unit, when the weight of the vibro unit is applied to the filler filled inside the already created diameter-expanding body, the filling body expands in diameter. By compaction, the vibro unit is returned downward. By horizontally vibrating the vibro unit (the vibro flot constituting the vibro unit) also during this return step, a predetermined return length can be secured and a diameter-expanded body having a predetermined diameter can be created. That is, the improved pile having a predetermined diameter finally created is created by gradually expanding the diameter of the expansion body whose diameter is controlled each time.

For example, the length of the initially constructed filler is set to 1 m (thus, the predetermined pull-out length is set to 1 m), and the vibro unit is returned, for example, 80 cm (the predetermined return length is set to 80 cm). The volume of 80 cm of the vibro unit contributes to the expansion of the diameter of the filler, and the expansion body is created. The diameter of the enlarged diameter body at this time can be accurately obtained from the calculation. After that, the diameter of the vibro unit is expanded by repeating the withdrawal of the vibro unit, for example, 1 m, the filling of the water-permeable material into the cavity formed by the withdrawal, and the return of the vibro unit, for example, 80 cm. The diameter of the body can be calculated accurately. The degree of diameter expansion of the enlarged diameter body may also change depending on the degree of hardness of the ground and the material type of the material for improving pile construction (for example, a water permeable material). That is, there may be a difference between the diameter of the enlarged diameter body obtained by calculation and the diameter of the enlarged diameter body actually created. Therefore, it is preferable to carry out a test construction using the improved pile construction material used for the construction in the construction area, and how much the diameter of the enlarged body will be expanded by one set of drawing and filling process and returning process. It is preferable to confirm.

Further, in the ground improvement method of this embodiment, the predetermined diameter of the improved pile can be changed by changing either or both of the predetermined pull-out length and the predetermined return length.
According to this construction method, by changing either or both of the pull-out length and the return length of the vibro unit, the diameter of the enlarged diameter body created each time by repeating the pull-out and return of the vibro unit is also final. The predetermined diameter of the improved pile to be constructed can also be changed as desired.

Further, in the ground improvement method of this embodiment, by repeating the extraction filling step and the returning step, a diameter-expanded body gradually expanded to the height position of the initially created filler is created, and the expansion is performed. It is also possible to create a part of the improved pile having a predetermined diameter at the height position of the diameter body, and to make a continuous improved pile having the predetermined diameter in the shallower ground.
According to this construction method, when the cumulative difference length between the pull-out length and the return length reaches the height of the initially created filler, the lower part of the improved pile with the desired predetermined diameter (improvement of the predetermined diameter). A part of the pile) is created. When the height of the initially formed filler is, for example, 1 m and the difference length between the withdrawal length and the return length is, for example, 20 cm, the desired predetermined diameter is obtained by repeating the set of the withdrawal filling step and the return step 5 times. A diameter-expanded body is created.

When the difference length between the pull-out length and the return length is, for example, 25 cm, a diameter-expanded body having a desired predetermined diameter is created by repeating the set of the pull-out filling step and the return step four times. Then, after the expanded body having a desired predetermined diameter is created, the expanded body having a predetermined diameter is formed, for example, on the ground surface by repeatedly setting the drawing and filling step and the returning step toward the upper part of the ground. Can be created up to.

Further, in the ground improvement method of this embodiment, when there is a hard layer between the ground surface and a predetermined depth, a pre-boring step of pre-boring the hard layer is further provided, and a penetration step is performed following the pre-boring step. You can also do it.
According to this construction method, if there is a hard layer up to a predetermined depth, the vibro unit is made by pre-drilling up to this hard layer with a pre-drilling machine or the like and guiding the vibro tool to a depth deeper than the hard layer. It is possible to guarantee the implementation of the ground improvement method by repeating the drawing and filling process and the returning process using the above.

Here, a permeable material can be applied as the "material for making improved piles", and any one of fly ash, incinerated ash or granulated material made of burnt ash, crushed stone, and slag can be applied to the permeable material.
By using a water-permeable material made of granulated material, crushed stone (recycled material or virgin material), or slag as a material for creating improved piles, unique effects can be expected depending on the material. First, the diameter of the granulated product can be adjusted as desired. Then, for example, by using a granulated product having a uniform diameter as the permeable material, it becomes easy for the horizontally vibrating vibro tool to smoothly enter the permeable material filled in the cavity in the returning step.
Further, for example, when a recycled material of crushed stone is used as a permeable material, the re-hardening performance of the crushed stone can be utilized, and the crushed stone absorbs water and re-hardens to create an improved pile with high hardness. be able to. It is a water-permeable material suitable for improved ground, for example, when ground bearing capacity is required in addition to liquefaction resistance.
In addition, granulation and crushed stone are used as water-permeable materials, and the improved pile is constructed as a composite structure having a load-bearing body made of crushed stone in the central region and a drainage body made of granulation in the outer peripheral region. You can also do it. According to this aspect, it is possible to create an improved pile having excellent load bearing capacity and drainage property. For the improved ground, for example, when the ground bearing capacity is required in addition to the liquefaction resistance, the improved pile has a suitable structure.

According to the vibro unit, the ground improvement device, and the ground improvement method of the present invention, it is possible to accurately create an improved pile having a predetermined diameter, and it is possible to improve the construction efficiency.

It is a device block diagram which shows an example of the ground improvement device which concerns on embodiment. It is a side view which shows an example of the vibro unit which concerns on embodiment. FIG. 2 is a view taken along the line III in FIG. 2, which is a view of an example of the vibro unit according to the embodiment as viewed from the lower ground penetration direction. It is a perspective view which saw an example of the vibro unit which concerns on embodiment from the downward oblique direction. It is a process drawing explaining an example of the ground improvement method which concerns on embodiment. (A), (b), and (c) are all vertical sectional views showing an embodiment of the improved pile to be created. It is a process diagram for explaining an example of the ground improvement method according to the embodiment in more detail. It is a diagram showing the cross-sectional area of the improved piles created in each process. It is a side view of the vibro unit of the actual machine and the model tube applied in the experiment. 8 is a cross-sectional view taken along the line AA to CC of the actual machine in FIG. 8, and a cross-sectional view taken along the line aa to a cross-sectional view taken along line cc of the model tube. It is a photograph figure which shows the experimental equipment. It is a figure which shows the experimental result which verified the effectiveness of the tip guide tube. It is a figure which shows the experimental result which verified the effectiveness of the tip fin.

Hereinafter, the vibro unit, the ground improvement device, and the ground improvement method according to the embodiment will be described with reference to the attached drawings. In the present specification and the drawings, substantially the same components may be designated by the same reference numerals to omit duplicate explanations.

[Ground improvement device and vibro unit according to the embodiment]
First, with reference to FIGS. 1 to 4, an example of the ground improvement device according to the embodiment and an example of the vibro unit according to the embodiment for forming the ground improvement device will be described. Here, FIG. 1 is an apparatus configuration diagram showing an example of the ground improvement apparatus according to the embodiment. Further, FIG. 2 is a side view showing an example of the vibro unit according to the embodiment, and FIG. 3 is a view taken in the direction III of FIG. 2, and an example of the vibro unit according to the embodiment is intruding into the ground below. It is a view from the direction, and FIG. 4 is a perspective view which is seen from the downward oblique direction as an example of the vibro unit according to the embodiment.

As shown in FIG. 1, the ground improvement device 100 includes a vibro unit 80 and a crawler crane 90 (an example of a heavy machine) in which a vibro unit 80 and a bucket 85 are hung by a wire W1. The vibro unit 80 has a silo tube 10 having a hopper 17 at the upper end and a vibro tool 20 attached to the lower end of the silo tube 10. In FIG. 1, the ground penetration direction is indicated by Z0. When the ground G to be improved has a hard layer, a pre-drilling machine 200 for pre-boring is applied. Further, although not shown, a wheel loader or the like for transporting or transporting earth and sand or crushed stone may be applied. In the ground improvement method described below, since the ground G in which a hard layer exists up to a predetermined depth which is the ground improvement depth is targeted for improvement, the preceding drilling machine 200 will be applied. When the ground without such a hard layer is targeted for improvement, the preceding drilling machine 200 becomes unnecessary.

As shown in FIGS. 2 to 4, the vibro unit 80 has a silo tube 10 made of a casing pipe and a vibro tool 20 attached to the lower end of the silo tube 10, and the vibro tool 20 causes horizontal vibration. It has a vibrator lot 30 having a built-in eccentric motor 31 to generate the vibrator, and a feeder 40 attached to the vibrator lot 30 and communicating with the silo tube 10. Further, a tip guide tube 50 is provided at the tip of the vibro tool 20 in the ground penetration direction, and a tip fin 55 projecting from the tip of the tip guide tube 50 in the ground penetration direction is provided with respect to the tip guide tube 50. ing. Although the middle of the silo tube 10 is omitted in FIG. 2, the vibro unit 80 including the silo tube 10 has a length up to a predetermined depth which is the ground improvement depth.

The horizontal vibration generated in the vibrof lot 30 is preferably a high frequency vibration of, for example, about 30 to 100 Hz. By applying such high-frequency horizontal vibration to the ground, the vibration energy is generally increased, and the compaction efficiency of the improved pile building material filled in the ground can be improved. In addition, because of the high frequency vibration, the propagation of vibration can be suppressed, and the influence on the surrounding environment can be further reduced. Further, by utilizing the fact that the current value (the value of the load on the eccentric motor 31) of the eccentric motor 31 built in the vibrof lot 30 increases according to the strength of the ground G, the eccentric motor 31 at the time of construction is used. The current value may be read and the ground properties may be determined by the current value. By such determination based on the current value, it is possible to apply a method of changing the diameter of the improved pile according to the ground properties.

In the above embodiment, for example, when the vibro unit 80 is penetrated into the ground G and the current value is less than the predetermined value, the target ground is determined to be soft ground, and the vibro unit 80 is penetrated again at the same location. , The improved pile can be created with a diameter larger than the initially set predetermined diameter. On the other hand, if the vibro unit 80 shows a predetermined current value or more when it penetrates into the ground G, it is determined that the target ground is strong ground, and the construction is stopped at that position, so that the improved pile is initially set. It can be created to a diameter smaller than the predetermined diameter. In this way, for example, by determining the actual ground properties using the current value and appropriately changing the diameter of the improved pile according to the ground properties, it is possible to realize rational and economical ground improvement according to the target ground. ..

By applying the high frequency (and therefore high output) eccentric motor 31, the vibration energy can be increased and the filler filled in the ground can be compacted with high efficiency. In addition, compared to the conventional CP method that applies low frequency and vertical vibration to the ground, the ground is improved while applying high frequency vibration in the horizontal direction to the ground, which can affect the surrounding environment of the improved area. It can be reduced.

Further, since the ground improvement device 100 has a configuration in which the vibro unit 80 is hung down by the crawler crane 90, it is a special type such as a three-point pile driving base machine like the ground improvement device applied at the time of the SCP method or the like. The machine is not a component. Therefore, it is possible to realize ground improvement construction using a versatile heavy machine 90, and it is possible to reduce the construction cost.

As shown in FIG. 2, a hopper 17 is attached to the upper end 11 of the silo tube 10, and the improved pile building material supplied via the hopper 17 is stored inside the silo tube 10 at any time. Inside the silo tube 10, for example, an opening / closing lid (not shown) is provided below the silo tube 10, and the material for improving pile construction is stored up to the vicinity of the upper end of the inside of the silo tube 10 in a state where the opening / closing lid is closed. Then, in the ground improvement method, when the material for improving pile building is supplied from the feeder 40 into the ground, the opening / closing lid is opened and the material for improving pile building is supplied via the feeder 40 communicating with the silo tube 10. Will be.

A plurality of anti-rotation blades 25 are attached to the outer peripheral surface of the vibro tool 20 at intervals, and the anti-rotation blades 25 cause the vibro unit 80 to be underground under its own weight while the vibro flot 30 vibrates horizontally. In the process of self-sinking, the vibro unit 80 is prevented from rotating around the axis.

At the tip of the vibro tool 20 in the ground penetration direction, a tip guide tube 50 having a hollow cross section larger than the hollow cross section of the tip of the feeder 40 is provided. More specifically, as shown in FIG. 3, the planar view shape (or the cross-sectional shape perpendicular to the ground penetration direction) of the feeder 40 and the vibrof lot 30 adjacent to each other is a track shape, whereas the tip is The guide tube 50 has two arc regions 51 and 52 corresponding to the feeder 40 and the vibrof lot 30. One arc region 51 has a cross-sectional area A1 similar to that of the hollow of the feeder 40, and the other arc region 52 has a cross-sectional area A2 of a part of the vibrof lot 30 and the tip guide tube 50. Has a total cross-sectional area A3 of both.

A steel tip guide tube 50 having a substantially eight-shaped (or substantially gourd) cross section and a hollow shape is fixed to the tip of the vibro tool 20 by welding or the like. More specifically, the tip guide tube 50 is attached so as not to surround only a part of the vibro flot 30 but to surround the other part of the vibro tool 20. Due to such a mounting mode, since the tip guide tube 50 does not surround the entire vibrof lot 30, the material for improving pile construction is filled while directly transmitting the horizontal vibration from the exposed basin of the vibroflot 30 to the ground. It becomes possible to secure a cavity having a desired diameter (desired dimension). The tip guide tube 50 may be attached so as to surround the entire tip of the vibro tool. Further, as the cross-sectional shape of the tip guide tube 50, various cross-sectional shapes such as a track shape, an elliptical shape, a rectangular shape, and a glasses shape consisting of two arcs having the same diameter can be applied in addition to the substantially eight-shaped shape in the illustrated example. ..

According to the vibro unit 80, the tip of the vibro tool 20 formed by the vibro flots 30 and the feeder 40 adjacent to each other in the ground penetration direction has a larger cross section than the hollow cross-sectional area A1 of the tip of the feeder 40. Since the tip guide tube 50 having a hollow (cross-sectional area A3) is provided, the hollow cross-sectional area A3 cavity of the tip guide tube 50 is grounded while preventing the hole wall from collapsing with the tip guide tube 50. Can be secured within. Then, by filling the cavity with a material for creating an improved pile, it becomes possible to create an improved pile having a predetermined diameter.

As is clearly shown in FIG. 4, grooves 21 are provided at two opposing positions at the tip of the tip guide tube 50, and one end of the steel tip fin 55 is fitted into these grooves 21 by welding or the like. The tip fin 55 is attached so as to protrude from the tip (tip in the ground penetration direction) of the tip guide tube 50.

The tip fin 55 is formed of a thick steel plate, and two tapered surfaces 56 are provided on the tip end surface thereof so that the center thereof is sharpened. In addition to the illustrated example, the tip fin may have a cross-shaped shape formed of, for example, two steel plates. In this form, for example, each of the four end faces is sharpened so that the center of the cross is sharpened. It is preferable that a tapered surface is provided.

By further providing a steel tip fin 55 protruding from the tip of the tip guide tube 50 in the ground penetration direction, deterioration of the penetration performance of the vibro unit 80, which is a concern due to the provision of the tip guide tube 50, is suppressed. can do. That is, by providing the substantially cylindrical tip guide tube 50 shown at the tip of the vibro tool 20 in the ground penetration direction, it is possible to secure a filling space (cavity) for the improved pile building material having a desired diameter, while at the same time, ground penetration. The penetration performance of the vibro unit 80 may be reduced by the presence of the tip guide tube 50 instead of the vibrating vibro flot 30 at the tip in the direction.

Therefore, by providing the tip fin 55 that protrudes in the ground penetration direction from the tip guide tube 50 with respect to the substantially tubular tip guide tube 50, the tip guide tube 50 is based on the ground penetration property of the tip fin 55. It is possible to effectively suppress the deterioration of the penetration performance of the vibro unit due to the provision of.

Although not shown, the vibro unit may have a form in which the tip fin 55 is not attached to the tip of the tip guide tube 50. In this embodiment, it is preferable to process the end surface of the tip guide tube 50 on the tip side in the ground penetration direction into a tapered surface (one end of the tapered surface becomes sharp) to improve the cutting performance of the tip guide tube 50.

Further, as shown in FIGS. 2 and 4, in the vibro unit 80, the water jet supply pipe 65 extends from the outer peripheral surface of the silo tube 10 to the outer peripheral surface of the tip guide tube 50 via the outer peripheral surface of the vibro tool 20. It is attached. As shown in FIG. 2, a water jet is supplied in the Z2 direction from a water jet supply mechanism (not shown) on the ground to the upper end 65b of the water jet supply pipe 65, via the lower end 65a of the water jet supply pipe 65. A water jet is supplied to the ground G in the Z3 direction. The illustrated vibro unit 80 includes a pair (two) of water jet supply pipes 65 at positions facing each other on the outer peripheral surface thereof.

By supplying a water jet from the water jet supply pipe 65 on the outer periphery of the tip guide tube 50, for example, even when a hard layer having an N value of about 20 or more exists in the ground G to be improved, the vibro unit 80 The vibro unit 80 can be reliably penetrated (self-sunk) into the ground by both its own weight and the crushing force of the water jet.

Further, as shown in FIGS. 2 and 4, in the vibro unit 80, the tip guide tube 50 is connected from the outer peripheral surface of the silo tube 10 through the outer peripheral surface of the vibro tool 20 and via the outer peripheral surface of the tip guide tube 50. An air jet supply pipe 67 is attached over the inner surface. As shown in FIG. 2, an air jet is supplied in the Z4 direction from an air jet supply mechanism (not shown) on the ground to the upper end 67b of the air jet supply pipe 67, via the lower end 67a of the air jet supply pipe 67. An air jet is supplied in the Z5 direction to the inner tip region of the tip guide tube 50. The illustrated vibro unit 80 includes a single air jet supply pipe 67 on its outer peripheral surface.

By supplying the air jet to the inside of the tip guide tube 50 from the lower end 67a of the air jet supply pipe 67, the material for making improved piles in the silo tube 10 can be quickly supplied to the ground and the tip guide tube 50. It is possible to prevent backflow of earth and sand from the tip of the silo to the vibro tool 20.

Further, as shown in FIG. 2, an opening 12 is provided on the side surface of the silo tube 10, and a measuring pulley 60 is attached in the vicinity of the opening 12. A wire W2 extends from the measuring pulley 60 and further extends into the silo tube 10 via a plurality of pulleys 61 around the opening 12, and a sand level gauge 62 is attached to the tip of the wire W2.

As shown through the inside in FIG. 2, the material for improving pile construction is stored in the silo tube 10 as needed up to the vicinity of the upper end thereof, and the material for improving pile construction is put into the ground from the feeder 40 in the ground improvement method. When the material for improving pile building is supplied via the feeder 40 communicating with the silo tube 10 at the time of supply, the material for improving pile building (top end surface TP) stored in the silo tube 10 is lowered. It descends in the Z1 direction. The sand level gauge 62 has fallen on the top surface TP of the improved pile building material, and the sand level meter 62 also drops in response to the descent of the top end surface of the improved pile building material, and the amount of movement of the wire W2 at that time is reduced. It is measured by the measuring pulley 60.

By multiplying this measurement result (the amount of change in the height of the top end surface TP of the improved pile building material) and the hollow cross-sectional area of the silo tube 10, the amount of decrease in the improved pile building material in the silo tube 10 is calculated. Therefore, the supply amount of materials for improving pile construction to the ground can be determined with high accuracy. In the ground improvement method according to the embodiment described below, after the vibro unit 80 is penetrated to a predetermined depth of the ground G, the vibro unit 80 is pulled upward by a predetermined pull-out length to improve the cavity created by this pull-out. Since the improved pile is created by repeatedly filling the pile building material and returning the vibro unit downward by a predetermined return length shorter than the predetermined pull-out length, a plurality of improved piles are created. The materials for the improved pile construction will be supplied to the ground. In this construction method, each time the material for improving pile construction is repeatedly filled, the supply amount of the material for improving pile construction to the ground is controlled by the measuring pulley 60, so that the supply amount can be controlled with high accuracy. Can be realized.

Although not shown, a control panel is mounted on the cockpit of the heavy machine 90, and the control panel is used to control the drive of the vibrator lot 30 and to improve the pile based on the measurement data transmitted from the measurement pulley 60. Various controls such as indexing control of the supply amount of the material for construction and drive control of the water jet mechanism and the air jet mechanism are executed. The control panel has a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disc Drive), NVRAM (Non-Volatile RAM), etc. It is connected so that data communication is possible. The ROM stores various programs and data used by the programs. The RAM is used as a storage area for loading a program stored in the ROM and as a work area of the loaded program. The CPU realizes various functions by processing the program loaded in the RAM. For example, the supply control of the water jet or the air jet is executed based on the optimum water jet supply amount or air jet supply amount for each depth specified by performing the test construction in advance. Further, the supply amount of the improved pile construction material supplied into the ground is calculated based on the movement amount of the wire W2 transmitted from the measurement pulley 60, and the calculated supply amount is supplied to the control panel at any time. Preservation guarantees highly accurate control of the supply of materials for improved pile construction.

[Ground improvement method according to the embodiment]
Next, an example of the ground improvement method according to the embodiment will be described with reference to FIGS. 5 and 6. Here, FIG. 5 is a process diagram illustrating an example of the ground improvement method according to the embodiment.

FIG. 5 is a process diagram for explaining the ground improvement method according to the embodiment, and is a series of process diagrams from the left diagram to the right diagram of FIG. That is, the steps from the left figure (step (A)) to the right figure (step (G)) are shown in order from the left figure (step (A)) to the right figure (step (G)) until the improved pile is constructed in the ground G immediately below the ground surface position. In steps (B) to (G) in FIG. 5, the crawler crane is not shown, and only the state in which the vibro unit 80 is suspended by the wire W1 is shown.

The ground G to be improved shown in FIG. 5 has a laminated structure of a plurality of layers having different ground properties of the soft layer G1, the hard layer G2, and the soft layers G3 to G5 in order from the surface layer. Then, the area from the surface layer to the intermediate level of the soft layer G5 is defined as a predetermined depth h (see step (B)), which is the ground improvement depth.

Since the ground G to be improved has a hard layer G2 below the soft layer G1 on the surface layer, first, as shown in step (A) of FIG. 5, the leading drilling machine 200 is used to reach the lower end of the hard layer G2. Pre-boring is performed while rotating the auger in the X1 direction (pre-boring step).

After pre-drilling to the lower end of the hard layer G2 in the pre-boring step, the pre-drilling machine 200 is retracted as shown in step (B), and the crawler crane 90 (see FIG. 1) passes through the wire W1. The vibro unit 80 is hung down, and the vibro tool 20 at the tip thereof is inserted into the ground G. Then, if necessary, the water jet is discharged from the tip of the water jet supply pipe 65 into the ground G, and the air jet is discharged from the air jet supply pipe 67 into the tip guide tube 50 by the weight of the vibro unit 80. The vibro unit 80 is self-sunk in the ground G in the X1 direction, and the vibro unit 80 is penetrated to a predetermined depth h (penetration step).

After the vibro unit 80 has penetrated to a predetermined depth, as shown in step (C), the water permeable material, which is a material for creating improved piles, is charged into the hopper 17 in the bucket 85, and the water permeable material is used as the silo tube 10. Store inside the. Then, as shown in the step (D), the vibro unit 80 is pulled out in the X2 direction upward by a predetermined pulling length h1, and the cavity created below the vibro tool 20 by this pulling is passed through the feeder 40. Further, the water permeable material is filled through the tip guide tube 50.

The withdrawal of the vibro unit 80 is performed while driving the eccentric motor 31 and vibrating the vibro tool 20 in the horizontal Y1 direction with high frequency vibration. The filling body C1 is created by filling the cavity formed by the extraction of the vibro tool 20 with a water-permeable material. The created filler C1 has a volume obtained by multiplying the cross-sectional area A3 of the tip guide tube 50 shown in FIG. 3 by the drawing length h1. For example, when the predetermined length h is about 5 m to 10 m, the drawing length h1 can be set to about 1 m (the above is the drawing filling step). When the amount of the water-permeable material in the silo tube 10 decreases by a certain amount, the water-permeable material is replenished in the silo tube 10 each time.

After the filler C1 having a volume obtained by multiplying the cross-sectional area A3 and the drawing length h1 is created, the vibro unit 80 is pulled out of the vibro unit 80 to have a predetermined return length h2 shorter than the drawing length h1 as shown in step (E). Return only to the lower X3 direction. The return of the vibro unit 80 is also performed while driving the eccentric motor 31 and vibrating the vibro tool 20 in the horizontal Y1 direction at a high frequency.

The vibro unit 80 is returned by self-sinking of the vibro unit 80 while vibrating the vibro tool 20 at a high frequency in the horizontal direction. For example, when the pull-out length h1 is set to about 1 m, the return length h2 can be set to about 50 cm to 85 cm.

By pulling out the vibro unit 80 and returning it downward by a return length h2 shorter than the pull-out length h1, the filler C1 is pushed sideways by the weight of the vibro unit 80 to expand its diameter, and the enlarged diameter body C2 is created. To. For example, when the pull-out length h1 is set to 1 m and the return length h2 is set to 80 cm, the diameter-expanding body C2 keeps the initial height of 1 m while the vibro tool 20 is pushed inward. In the height region of 80 cm, the volume of the inserted vibro tool 20 is expanded laterally by the volume integral, and a stepped diameter-expanded body C2 is created as shown in the illustrated example.

In this way, the expansion body C2 is formed by pushing the filler C1 from above by the weight of the vibro unit 80 and expanding the diameter laterally. At this time, the vibro tool 20 has a high frequency in the horizontal direction. Since the filler C1 is pushed in while vibrating, the vibration direction of the vibro tool 20 and the formation direction (diameter expansion direction) of the diameter expansion body C2 are the same, which is an improvement method with high construction efficiency (the above is a return method). Process).

The above steps (C) to (E), that is, from the preparation for filling the water-permeable material to the drawing and filling step and the returning step, are set as one set, and this set is repeated a predetermined number of times as in the step (F) of FIG. .. During the repeated construction of the drawing and filling process and the returning process, high-frequency vibration in the Y1 direction, which is the horizontal direction of the vibro tool 20, is constantly executed, and this high-frequency vibration is applied to the ground to move upward of the improved pile. Is created.

As shown in the step (G), when the improved pile C5 having a predetermined diameter φ is formed up to the ground surface, for example, the formation of the improved pile C5 in one place of the improved area is completed.

By constructing each improved pile C5 at an improved pitch according to a predetermined improvement rate in the construction area, it is possible to create an improved ground having desired liquefaction strength, bearing capacity, etc. in the construction area.

In the ground improvement method according to the embodiment, the diameter of the enlarged diameter body created by repeating the pulling out and returning of the vibro unit 80 by changing either or both of the pulling out length and the returning length of the vibro unit 80. However, the predetermined diameter of the improved pile to be finally created can also be changed as desired. For example, even if the predetermined pull-out length is set to 1 m, the diameter of the enlarged diameter formed is different between the construction in which the predetermined return length is set to 80 cm and the construction in which the predetermined return length is set to 85 cm. Further, even if the predetermined return length is set to 80 cm, the diameter of the enlarged diameter formed is different between the construction in which the predetermined pull-out length is set to 1 m and the construction in which the predetermined pull-out length is set to 1.5 m. Therefore, it is preferable to set the pull-out length and the return length of the vibro tool 20 to create an improved pile having a predetermined diameter so that the optimum compaction management can be executed according to the degree of hardness and softness of the ground.

According to the illustrated ground improvement method, it is possible to create a large-diameter improved pile having a diameter of, for example, about 800 mm to 1000 mm. Therefore, even when the improved pile is constructed at the same improvement rate as the CP method for creating the improved pile with the upper limit of the diameter of about 700 mm, the pitch of the improved pile can be increased by the ground improvement method shown in the figure. This makes it possible to shorten the construction period and reduce the construction cost. For example, when the CP method and the ground improvement method according to the embodiment are used to create improved piles with the same improvement rate, the SCP method requires the improvement piles to be created at a pitch of 1.9 m. In the ground improvement method according to the embodiment, improved piles can be constructed at a pitch of 2.8 m, and the construction length can be reduced by about 20%.

Further, by setting the pull-out length and the return length of the vibro unit 80 to, for example, 1 m and 80 cm, respectively, the diameter of the enlarged diameter body created in these steps can be accurately obtained from the calculation. After that, the diameter of the vibro unit 80 is expanded by repeating the withdrawal of 1 m of the vibro unit 80, the filling of the water-permeable material into the cavity formed by this withdrawal, and the return of the vibro unit 80 with 80 cm each time. The diameter of the body can be calculated accurately. However, as described above, in the ground improvement device 100 applied by the illustrated ground improvement method, the fluctuation height of the permeable material in the silo tube 10 is accurate due to the measuring pulley 60 provided in the vibro unit 80. It is well measured, and the amount of water-permeable material supplied to the ground is accurately determined and managed based on this measurement data.

The degree of diameter expansion of the enlarged diameter body may change depending on the degree of hardness of the ground G. That is, there may be a difference between the diameter of the enlarged diameter body obtained by calculation and the diameter of the enlarged diameter body actually created. Therefore, it is preferable to carry out a test construction in the construction area and confirm how much the diameter of the enlarged diameter body is expanded by one set of drawing and filling step and returning step. That is, it is preferable to carry out a test construction using a predetermined water-permeable material in the construction area and obtain a correction coefficient from the ratio of the measured value and the design value of the diameter of the enlarged diameter body to be created.

This correction factor can be determined by the properties of the ground in the construction area (easiness of ground tightening, degree of hardness, etc.) and the permeable material used. Further, as shown in the illustrated example, when a plurality of types of strata (G1 to G5) are laminated in the range from the ground surface to the improvement depth h in the construction area, the correction coefficient is obtained for each stratum G1 to G5. Is more preferable. At the time of implementation work, by creating an improved pile with a construction control diameter calculated by multiplying the predetermined diameter (design value) of the improved pile for each stratum G1 to G5 by the correction coefficient peculiar to the stratum, the predetermined depth It is possible to create improved piles with even higher precision.

The ground improvement method in the illustrated example is to create an improved pile C5 with the same predetermined diameter φ over the design length h3, but an improved pile with a different predetermined diameter φ is created for each layer G1 to G5. You may. In this case, the construction control diameter in each layer at the time of implementation work is set using the correction coefficient set in advance for each stratum in the test construction, and the improved piles with the construction control diameter unique to each layer are stacked. It is possible to create improved piles.

As described above, according to the illustrated ground improvement method, the cavity formed by pulling out the vibro unit 80 with the crawler crane 90 is filled with the water-permeable material to form the filler C1, and the vibro tool 20 is placed in the horizontal direction. The diameter of the filler C1 is expanded laterally by the self-sinking of the vibro unit 80 while vibrating at high frequency to create the expansion body C2, and this is repeated to gradually expand the diameter of the expansion body C1 to improve the pile. Create C4. Therefore, it is possible to construct an improved pile C4 that can both increase the density of the ground and dissipate the pore water pressure without using a special machine.

Next, with reference to FIG. 6, the improved pile according to the permeable material used will be described. Here, FIGS. 6A, 6B, and 6C are vertical cross-sectional views showing an embodiment of the improved pile to be constructed.

FIG. 6A is a diagram showing an improved pile when a granulated product Z made of fly ash, incinerator ash or burnt shavings is used as the water permeable material. When the granulated product Z is used as the water-permeable material, the diameter of the water-permeable material can be adjusted as desired. Then, for example, by using the granulated product Z having a uniform diameter as the water permeable material, the vibro tool 20 that vibrates horizontally easily easily enters the water permeable material filled in the cavity in the returning step.

Further, since it is a granulated product, its strength can be adjusted to a desired strength. In addition, unlike the CP method, which is compacted in the vertical direction, the vibro tool 20 is vibrated in the horizontal direction to expand its diameter, so that it is possible to prevent particle crushing of the water-permeable material and ensure good water permeability. can do.

In the granulated product Z made of fly ash, for example, a strength of about 10 N / mm ² can be expected. Further, it is possible to produce a granulated product Z having a particle size of about 10 mm to 40 mm.

Furthermore, when a large amount of fly ash (incineration ash, burnt ash, etc.) generated from a coal-fired power plant is granulated and used as a ground improvement material, the generated fly ash can be effectively used. For example, by applying the ground improvement method of this embodiment to the ground improvement in the site of a coal-fired power plant, a large amount of fly ash generated in the site can be used as a ground improvement material in the site.

On the other hand, FIG. 6B is a diagram showing an improved pile when crushed stone S is used as the water permeable material. The crushed stone S may be a recycled material or a virgin material. When, for example, crushed stone S, which is a recycled material, is used as the water-permeable material, the crushed stone S absorbs moisture and re-hardens, so that the improved material is not pressed into the ground as in the CP method, and the strength is high. An improved pile C5 can be created. Therefore, when the improved ground is required to have a ground strength in addition to liquefaction resistance, it is preferable to use the crushed stone S as a water-permeable material to carry out the ground improvement method of this embodiment.

On the other hand, FIG. 6C is a diagram showing improved piles when both granulated material Z and crushed stone S are used as the water permeable material. The improved pile C5 to be constructed is a composite structure having a load-bearing body made of crushed stone S in the central region and a drainage body made of granulated material Z in the outer peripheral region. According to the illustrated improved pile C5, it is possible to provide an improved pile having excellent both load resistance and drainage resistance (liquefaction resistance). For example, it is a suitable improved pile when constructing a high-rise building or the like on liquefied ground. In addition to the illustrated examples, slag or the like may be applied as the water-permeable material.

<Example of ground improvement method>
Next, an embodiment of the ground improvement method will be described with reference to FIG. 7. Here, FIG. 7 is a process diagram for explaining an example of the ground improvement method according to the embodiment in more detail, and the upper part is a vertical sectional view of a vibro unit including a vibro tool in each process and an improved pile created. The lower part is an arrow view in the upper part and shows the cross-sectional area of the improved piles created in each process. The numerical values in the figure are in millimeters.

In this embodiment, the pull-out length of the vibro unit 80 (or vibro tool 20) in the pull-out filling step is 1 m (1000 in the figure corresponds to it), and therefore the height of the filled body to be formed is 1 m, which means that the vibro unit 80 (or the vibro tool 20) is cut off. The area is A3, which is the cross-sectional area of the tip guide tube 50 at the tip of the vibro tool 20. Further, the return length of the vibro tool 20 in the drawing and filling step is 80 cm (corresponding to 800 in the figure), and the difference value from the pulling length is 20 cm (corresponding to 200 in the figure).

The step (A) in FIG. 7 is a penetration step, in which the vibro tool 20 is penetrated from the surface layer to a predetermined depth h. Next, in step (B), a cavity having a height of 1 m is formed by pulling out the vibro tool 20 by 1 m, and the cavity is filled with a water-permeable material from the feeder 40 of the vibro tool 20 via the tip guide tube 50. , A filler P1 having a cross-sectional area A3 and a height of 1 m is created.

Next, in the step (C), the vibro tool 20 is vibrated at a high frequency in the horizontal direction and returned 80 cm downward to fill a volume of 80 cm in height due to the horizontal vibration of the vibro tool 20 and the weight of the vibro unit 80. It will be buried in P1. By this construction, while maintaining the original height of the filler P1 of 1 m, the filler P1 expands laterally by the volume equivalent to the height of 80 cm of the vibro tool 20, and the diameter-expanded body P1'with a cross-sectional area A4. Is created.

That is, in this embodiment, when the vibro tool 20 is returned to the filler P1 by a predetermined return length, the volume of the vibro tool 20 embedded in the filler P1 is on the side of the filler P1. The cross-sectional area of the diameter-expanding body P1'is calculated as being allocated to the volume increment to expand the diameter. In reality, it is assumed that the height of the enlarged diameter P1'is 1 m or more (that is, it also expands in the height direction) with respect to the height of the filler P1 (1 m in the illustrated example). However, if it is expanded in two vertical and horizontal directions, the calculation becomes complicated. Therefore, in this embodiment, it is assumed that the volume of the returned portion of the vibro tool 20 contributes only to the expansion in the horizontal direction.

In the step (C), the cross-sectional area of the enlarged diameter P1'(the cross-sectional area of the donut-shaped portion in the drawing) is preferably set in consideration of the ground properties and the correction coefficient due to the water-permeable material. For this correction coefficient, the cross-sectional area of the actual diameter-expanded body is measured by performing a test construction using the permeable material used in the construction work in the construction area, and the ratio between the design value and the measured value is obtained. It is set by things such as. Since this correction coefficient can change depending on the ground properties and the permeable material used, it is uniquely set by the combination of the ground in the construction area and the permeable material used. More specifically, in the case of a ground in which a plurality of strata are laminated as shown in FIG. 5, the cross-sectional area of the enlarged diameter body is measured for each stratum in the test construction, and the correction coefficient for each stratum is calculated. It is preferable to specify it. By calculating the construction management diameter according to the unique correction coefficient for each stratum and creating improved piles based on this construction management diameter, the improved piles with the desired diameter can be increased even in multi-layered ground with different ground properties. It can be created under the finished product. It should be noted that the cross-sectional area of the enlarged diameter body may be calculated without performing the test construction and therefore without using the correction coefficient.

Next, in the step (D), a cavity having a height of 1 m is formed by pulling out the vibro tool 20 by 1 m, and the water-permeable material is filled in the cavity via the feeder 40 of the vibro tool 20 and the tip guide tube 50. By doing so, a filler P2 having a cross-sectional area A3 and a height of 1 m is formed inside the donut-shaped portion of the enlarged diameter body P1'. Here, the height from the predetermined depth h to the upper end of the filler P2 is 1.2 m.

Next, in the step (E), the vibro tool 20 is vibrated at a high frequency in the horizontal direction and returned 80 cm downward to fill a volume of 80 cm in height due to the horizontal vibration of the vibro tool 20 and the weight of the vibro unit 80. It will be buried in P2. By this construction, while maintaining the original height of 1.2 m of the filler P2, the filler P2 is expanded laterally by the volume equivalent to the height of 80 cm of the vibro tool 20, and the enlarged diameter P2'is created. By doing so, the outer diameter expander P1'is pushed out. Then, in the step (F), a filler P3 having a cross-sectional area A3 and a height of 1 m is created in the cavity, so that the expanded body P1', the expanded body P2'and the filler P3 having the cross-sectional area A5 are united. Is created. After that, by repeating these steps, 1 m of the vibro tool 20 is pulled out, a filler is formed in the cavity, and an enlarged diameter body is formed by returning the vibro tool 20 to 80 cm, so that the diameter is desired and desired. An improved pile of length is created.

[Effectiveness verification experiment of tip guide tube]
The present inventors conducted a soil tank compaction experiment to verify the effectiveness of the tip guide tube. FIG. 8 shows a side view of the vibro unit of the actual machine and the model tube applied in the experiment, and FIG. 9 shows the AA to CC cross-sectional views of the actual machine and the model tube in FIG. The aa cross-sectional view to the cc cross-sectional view of the above is shown. Further, FIG. 10 shows the experimental equipment as a photographic diagram.

In this experiment, a model tube shown in the right figure of FIG. 8 was created in order to simulate the actual machine shown in the left figure of FIG. The shape of the model tube is a half-split cross-sectional shape in order to observe the state of the filling material falling. In addition, since the internal structure of the actual machine has changed at the upper part of the motor in the center, the model tube also reproduced the structure of the actual machine as much as possible. The total length of the model tube was set to 4 m as the upper limit in consideration of the ceiling height and workability of the experimental building. In addition, the scale of the model tube was set to 1/2 scale in consideration of the particle size of the filling material that can be procured. In the model tube, the one provided with the tip guide tube is used as an example, and the one without the tip guide tube is used as a comparative example.

The experimental equipment shown in FIG. 10 was created, and in this experiment, a wooden clay tank was installed in the clay tank pit, water was filled with the model pipes of the examples and comparative examples installed, and the mountain sand was quietly filled. It was thrown in to produce saturated ground. The front of the clay tank is made of acrylic, and the mechanism is such that the state of the ground and the inside of the half-split model tube can be observed. In this experiment, the vertical movement of the model tube was performed by using a boring machine. The experimental results are shown in FIG.

In FIG. 11, the unit of each numerical value is cm. In the left figure showing the spread of the XZ plane of FIG. 11, the VP200 tube at the lower end of the embodiment simulating the tip guide tube is shown, and the width of 15.8 cm is shown on the graph.

For the convenience of the experiment, the pull-out length and the return length of the model tube shown in the right figure of FIG. 11 are different between the example and the comparative example, and the construction depths in the experimental results in the left figure and the center figure of FIG. 11 are also different. However, the target values for the pull-out lengths of the examples and the comparative examples are both 50 cm at the initial stage and 20 cm thereafter.

In the comparison between the example and the comparative example in the experimental results, for example, by comparing the width of the finished product in the depth direction of both the comparative example and the example in the left figure, the difference between the two can be easily understood. That is, in the left figure of FIG. 11, it can be seen that in the finished form of the comparative example, the width of the lower part is narrower than that of the upper part, and the created pile having a sufficient diameter cannot be created in the lower part. For example, the width of the comparative example at the lowermost depth of -120 cm is about 10 cm, while the width of the comparative example at the uppermost depth of about -14 cm is about 35 cm, and the distribution is distributed in the width of the finished product. be.

On the other hand, the finished shape of the embodiment has an almost uniform width of about 20 cm from the lower end (depth of about -160 cm) to the upper end (depth of about -40 cm), and is sufficient even below. It has been proved that a pile with a diameter has been created.

From this experiment, it is possible to secure a cavity with a hollow cross-sectional area of the tip guide tube in the ground by attaching a tip guide tube having a hollow with a larger cross section than the hollow of the feeder to the tip of the vibro tool. It has been demonstrated that a pile with a desired diameter can be created by filling the secured cavity with a material for creating improved piles.

[Effectiveness verification experiment of tip fin]
Next, the present inventors conducted a compaction experiment for verifying the effectiveness of the tip fin. In this experiment, the ground improvement device shown in FIG. 1 (a device in which the tip fin 55 is attached to the tip of the tip guide tube 50, hereinafter referred to as an embodiment) and the ground shown in FIG. 1 are used for the original ground. Using a device (reference example) in which the tip fins were removed from the improved device, each pile was created, and the time required to create 1 m in the depth direction was measured and compared.

In this experiment, in creating the improved body, one step is to create 0.25 m by pulling up 1 m and returning 0.75 m, and this is performed in a plurality of steps. The experimental results are shown in FIG.

In FIG. 12, a 1 m section of GL-14 m to GL-13 m is extracted, and the time required to create 1 m in the depth direction of Examples and Reference Examples is measured. From FIG. 12, the required time of the reference example was 1 minute and 21 seconds, whereas the required time of the embodiment was 1 minute and 10 seconds. By providing the tip fin at the tip of the tip guide tube, 15%. It has been demonstrated that the construction time can be shortened to some extent. Therefore, it can be seen that an improved pile having a desired diameter can be efficiently created by attaching the tip guide tube 50 to the tip of the vibro tool 20 and attaching the tip fin 55 to the tip of the tip guide tube 50.

It should be noted that the configuration or the like described in the above embodiment may be another embodiment in which other components are combined, and the present invention is not limited to the configuration shown here. .. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form thereof.

10: Silot tube 11: Upper end 12: Opening 17: Hopper 20: Vibro tool 21: Groove 25: Anti-rotation wing 30: Vibro crane 31: Eccentric motor 40: Feeder 41: Filling port 50: Tip guide tube 55: Tip fin 56: Tapered surface 60: Measuring pulley 61: Pulley 62: Sand level gauge 65: Water jet supply pipe 67: Air jet supply pipe 80: Vibrator unit 85: Bucket 90: Crawler crane (heavy equipment)
100: Ground improvement device 200: Preceding drilling machine G: Ground C1: Filler C2, C4: Diameter expander C5: Improved pile Z: Granulation S: Crushed stone W1, W2: Wire

Claims (7)

Silo tubes to which materials for improving pile construction are supplied, and
A vibro unit having a vibro tool attached to one end of the silo tube.
The vibro tool is
It is equipped with a vibro flot that generates horizontal vibration and a feeder that is attached to the vibro flot and communicates with the silo tube.
A vibro unit, characterized in that a tip guide tube having a hollow cross section larger than the hollow cross section of the tip of the feeder is provided at the tip of the vibro tool in the ground penetration direction. The vibro unit according to claim 1, wherein the tip guide tube is provided with a tip fin protruding from the tip of the tip guide tube in the ground penetration direction. An opening and a measuring pulley are provided on the side surface of the silo tube, a wire extending from the measuring pulley extends into the inside of the silo tube through the opening, and a sand level gauge is attached to the tip of the wire.
The sand level gauge is dropped on the top surface of the improved pile building material inside the silo tube, and the amount of movement of the wire at that time is measured by the measuring pulley to build the improved pile. The vibro unit according to claim 1 or 2, wherein the supply amount of the material to the ground is controlled. A water jet supply pipe is attached from the outer peripheral surface of the silo tube to the outer peripheral surface of the tip guide tube via the outer peripheral surface of the vibro tool.
The vibro unit according to any one of claims 1 to 3, wherein the water jet is supplied from the tip of the water jet supply pipe to the outer periphery of the tip guide tube. An air jet supply pipe is attached from the outer peripheral surface of the silo tube to the inner surface of the tip guide tube via the outer peripheral surface of the vibro tool and the outer peripheral surface of the tip guide tube.
The vibro unit according to any one of claims 1 to 4, wherein an air jet is supplied from the tip of the air jet supply pipe to the inside of the tip guide tube. Mobile heavy equipment and
The ground improvement device comprising the vibro unit according to any one of claims 1 to 5, which is suspended from the heavy machine via a wire. A penetration step of penetrating the vibro unit to a predetermined depth of the ground while generating horizontal vibration by using the ground improvement device according to claim 6.
A drawing filling step in which the vibro unit is pulled upward by a predetermined pulling length, and the cavity created by the pulling is filled with the improved pile building material via the tip guide tube to form a filler.
A return step of returning the vibro unit downward by a predetermined return length shorter than the pull-out length, and creating a diameter-expanded body in which the filler is expanded by this return.
A ground improvement method, characterized in that an improved pile having a predetermined diameter is created by repeating the drawing and filling step and the returning step.

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