JP2000345546A - Improvement method for soft ground containing hard stratum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the collapse of the wall of a bore hole made in advance by forming a pile for holding a loose bore hole wall to a depth at the lower end in a hard stratum in advance and then forming a pile-shaped or wall-shaped thing such as a sand pile or a hardened pile in the pile portion. SOLUTION: A casing pipe 12 is rotated by a motor 14 and inserted to a bottom portion 16 in a hard stratum 1. Next, sand is placed from a sand inlet 11 and inserted to the casing pipe 12, then the casing pipe 12 is pulled out, sand is left in the bore hole portion, and a sand pile 15 is formed in the ground. Then, an insertion pipe 23 is rotated in alignment with the center of a column body working the tip of a mechanical type agitator equipment 30. Then, agitating vanes are rotated while discharging a low strength hardener from the tip of the insertion pipe 23, and is driven while mixing together with the excavated earth, and the discharging is stopped at design depth of 29. In succession, the insertion pipe 23 is rotated reversely and pulled up while mixing and agitating thereby forming a columnar body 25 including both the soft ground 2 and the hard stratum 1. In this way, the penetration of the insertion pipe can be made easier, thereby permitting the high efficiency work for piles or wall-shaped things such as sand piles, crushed stone piles or the like required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compacting sand piles or crushed stones after preliminarily drilling a hard layer existing in the surface portion of the ground or an intermediate layer relatively close to the surface portion with an auger drill. The present invention relates to a method for improving soft ground having a hard layer capable of highly efficient construction for preventing collapse of a drilled wall before forming compacted sand piles or crushed stone piles when forming a pile or the like.

[0002]

2. Description of the Related Art Conventionally, as a method of improving a soft ground having a hard layer existing in a surface layer portion of the ground or an intermediate layer relatively close to the surface layer, for example, a method of penetrating a hard layer into a soft ground and forming a large amount of sand in the soft ground. There is a compacted sand pile construction method and a consolidated pile construction method for creating piles and consolidated piles. In the method of improving the soft ground having this hard layer, first, in order to facilitate the formation of sand piles and the like in the subsequent process, the hard layer is pre-drilled by an auger drill, and then the pre-drilling is performed. In some cases, a method of creating a large number of compacted sand piles and consolidated piles may be adopted.

[0003]

In this case, first, a large number of pre-drilled holes are formed in the hard layer.
When creating sand piles and consolidated piles in the post-process, which will be performed a few days later, the drilling wall collapses due to the vibration generated during drilling of the adjacent preceding drilling or other vibrations, and the preceding drilling Holes may be blocked. In this case, there is no point in providing the pre-drilling, and there is a problem that the re-drilling significantly reduces the construction efficiency.

[0004] Accordingly, an object of the present invention is to provide an improved method of soft ground having a hard layer capable of performing construction with high efficiency while avoiding collapse of the drilling wall of the preceding drilling.

[0005]

Under such circumstances, the present inventors have conducted intensive studies, and as a result, previously prepared a large number of loose drilling wall holding material piles at the lower end depth in the hard layer, When pile-like or wall-like materials such as sand piles and consolidated piles are constructed on such piles, the problem of collapse of the drilling wall of the pre-drilling can be avoided and high-efficiency construction is possible. The invention has been completed.

That is, the present invention provides a first step in which a number of drilled wall holding material piles are formed in a hard layer and a part of the hard layer is replaced with the drilled wall holding material. And a second step of constructing a pile or wall from a design depth. By adopting such a configuration, the first step is, instead of simply drilling the ground with an auger drilling machine, for example, drilling by a known sand pile formation method and drilling of a drilled wall holding material pile such as a loose sand pile. Since the formation is performed at the same time, it is possible to prevent the drilling wall from collapsing and to easily insert an insertion pipe or the like into the drilling portion in a later step. In the second step, an insertion pipe, a ready-made pile, a sheet-like wall, or the like can easily penetrate into the drilled wall holding material pile formed in the first step, so that a desired sand pile, crushed stone pile, ready-made pile or solid pile can be obtained. High-efficiency construction of piles or wall-like objects such as knots is possible.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The first step of the method for improving soft ground having a hard layer according to the present invention is to form a large number of drilling wall holding material piles in the hard layer and to make a part of the hard layer into the drilling wall. This is a step of replacing with a holding material. The drilled wall holding material pile is formed such that an insertion tube, a ready-made pile, a sheet-like wall, or the like, which penetrates into the drilled wall holding material pile performed in the second step, is easily performed. Therefore, as a drilled wall holding material pile, for example,
Sand pile, crushed stone pile, etc. filled with sand, crushed stone, on-site remaining soil, and the like. Of these, a loose sand pile having a low density is preferable in that it prevents collapse of the drilled wall and facilitates penetration of an insertion tube or the like into the drilled portion in a later step. The drilled wall holding material pile may be formed over the entire depth of the hard layer, or may be formed halfway (partly).

As a method for forming a sand pile and a crushed stone pile, as disclosed in Japanese Patent Publication No. 25808/1987, the hollow pipe is penetrated to the lower end depth of the hard layer and then pulled out to the surface of the ground. A method of discharging sand, crushed stones, and the like that have been introduced into the hollow pipe having a constant depth is drawn.
A conventional so-called compaction sand pile forming method is a method of repeatedly performing a re-penetration step of re-penetrating the hollow pipe and compacting discharged sand, etc., following the step of pulling out the hollow pipe, thereby performing a predetermined process. A method for forming a sand pile compacted to a high strength. In the method for forming a sand pile and a crushed stone pile in the first step of the present invention, the re-penetration step is omitted or the penetration width of the re-penetration is reduced. This is preferable because a loose sand pile or the like can be formed. Also, as a construction machine that penetrates the hollow pipe to the lower end depth of the hard layer, it has a hard layer, and also includes a rotary penetration device in that it easily maintains a holding state replaced with a drilled wall holding material. Construction machines are preferred.

The second step of the method for improving soft ground having a hard layer according to the present invention is a step of constructing a pile or a wall from the drilled wall holding material pile formed in the first step from a design depth. is there. Examples of the pile or wall include sand piles, crushed stone piles, ready-made piles, and consolidated piles. Examples of the method for forming the sand pile and the crushed stone pile include a method similar to the method for forming the sand pile and the crushed stone pile performed in the first step, but in the second step,
Unlike the method of the first step, by repeatedly performing the re-penetration step, it is possible to form a sand pile compacted to a predetermined strength by compacting the soft ground existing below the hard layer or above and below the hard layer. This is preferable in that the ground can be strengthened.

[0010] The method of forming a ready-made pile is a method of driving a separately manufactured pile body such as a concrete pillar or a steel pipe, and the method of forming a consolidated pile is, for example, using a tip of a mechanical stirring device. Rotate the rod according to the core of the column, rotate the stirring blade while discharging the lightweight solidified material from the tip of the device, perform excavation while mixing and stirring with excavated soil, stop discharging when the design depth is reached, A method of reversing the rod and pulling it up on the ground while further mixing and stirring to form a columnar body may be used. In addition, as a method of forming a wall-like object, a method of forming a wall-like object by connecting a large number of columnar bodies formed by the above-described method of forming a consolidated pile is used. The creation of walls can prevent the spread of underground pollution caused by waste and containment ponds and river embankments.

An improvement method for a soft ground having a hard layer according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing the steps of an improvement method for a soft ground having a hard layer. In FIG. 1, the ground is a hard / soft laminated ground in which a soft ground 2 exists below a hard layer 1. Also,
(I), (II) and (III) show the loose sand pile forming step of the first step, and (IV) and (V) show the consolidated pile forming step of the second step.

Sand pile forming apparatus 1 used in the first step
0 is a casing tube 12 equipped with a spiral 13 on the outer periphery.
And a motor 14 for rotating the casing tube 12 and a sand inlet 11 for introducing sand into the casing tube 12. First, the casing tube 12 is rotated by the motor 14 and inserted up to the bottom 16 of the hard layer 1 ((I) and (II) in FIG. 1). After that, the casing tube 12 is rotated in the reverse direction and pulled out, sand is left in the drilled portion, and a diameter of 40 mm is placed in the ground.
A sand pile 15 of about 50 cm is formed ((III) in FIG. 1). Thereby, since the advance drilling is not formed in advance using the auger drilling machine, the problem of the collapse of the drilling wall does not occur, and the loose sand pile 15 can be formed in the hard layer 1.
The penetration of the penetration pipe 28 in the second step is facilitated.

The mechanical stirring device 30 used in the second step includes a crawler crane 21, a leader 27 that supports or guides an elevating device 22 having one end fixed to the crawler crane 21, and an insertion pipe connected to the elevating device 22. 2
3 is a single-axis machine having a lower drive motor 24 connected to a flange (not shown) fitted to a square shaft at a lower portion of the insertion tube 23 having a square outer periphery to rotate the insertion tube 23. First,
The tip of the mechanical stirring device 30 is rotated in accordance with the core of the column to be installed, and the insertion pipe 23 is rotated. The stirring blade is rotated while discharging the low-strength solidified material from the tip of the insertion pipe 23 to mix and stir the excavated soil. When the depth reaches the design depth 29, the discharge is stopped, the insertion tube 23 is reversed, and the column is pulled up onto the ground while further mixing and stirring to form the columnar body 25 extending over the soft ground 2 and the hard layer 1. ((IV) and (V) in FIG. 1). The second step is to use the sand pile 15 formed in the first step.
Is of low strength, the insertion pipe 23 into the sand pile 15
Penetration becomes easy, and construction efficiency increases.

[0014]

According to the present invention, in the first step, instead of simply drilling the ground with an auger drilling machine, for example, drilling is performed by a known sand pile forming method and a drilled wall such as a loose sand pile is formed. Since the formation of the holding material piles is performed at the same time, it is possible to prevent the drilling wall from collapsing and to easily insert an insertion tube or the like into the drilling portion in a later step. In the second step, since an insertion pipe, a ready-made pile, a sheet-like wall and the like can easily penetrate into the drilled wall holding material pile, a desired sand pile, a crushed stone pile, a ready-made pile or a consolidated pile or the like, Highly efficient construction of wall-like objects becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic view showing steps of a method for improving soft ground having a hard layer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard layer 2 Soft ground 10 Sand pile forming apparatus 11 Sand inlet 12 Casing pipe 13 Spiral 14 Motor 15 Sand pile 16 Lower end depth of hard layer 21 Crawler crane 22 Elevating device 23 Insertion pipe 24 Lower drive motor 25 Column 27 Leader 29 Design depth 30 Mechanical stirrer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D040 AB05 AB14 AC05 BA08 BD03 BD05 CA09 2D041 AA01 AA02 BA31 CA01 CB01 DA12 DB02 DB03 EA01 FA01 2D043 CA01 CA02 CA06 CA12 DB01 EA01 EA02

Claims (2)

[Claims] 1. A first step in which a plurality of drilled wall holding material piles are formed in a hard layer, and a part of the hard layer is replaced with the drilled wall holding material. Or a method of improving soft ground having a hard layer, comprising a second step of constructing a wall-shaped object from a design depth. 2. The pile-shaped material or the wall-shaped material is a sand pile, a crushed stone pile, a ready-made pile or a consolidated pile.
An improved method for soft ground having a hard layer as described above.