JP2876353B2 - Construction method of reinforced sand pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a reinforced sand pile.

[0002]

2. Description of the Related Art The soft ground which has been treated as a conventional construction object is the sediment transported by rivers to old valleys and coastal areas.
There were many so-called alluvial deposits formed by the accumulation of silt. Since such soft ground was generated over a long period of time by natural action, the state of the stratum was relatively uniform, and in most cases, the strength increased as going deeper into the ground.

As a method of improving a soft ground having such a characteristic, a method of placing a sand pile or the like in the ground, performing embankment embankment, promoting consolidation settlement, and achieving a predetermined strength has long been performed. Was. Such a method is still used for considerable ground.

[0004] In recent years, however, there has been an increasing number of opportunities to carry out construction work in coastal areas and at artificially reclaimed sites.
Such artificially created ground is softer than natural ground, and easily deforms fluidly even with a slight load. In addition, the state is often non-uniform as compared to naturally occurring soft ground.

[0005]

2. Description of the Related Art Even if a conventional method for promoting drainage of sand drains, paper drains, etc. is applied to the improvement of artificially constructed soft ground, there are the following problems. <A> During construction of a sand drain or the like, sand piles that have been cast earlier are dispersed due to deformation of the ground. <B> Since extremely fine soil particles are suspended in the unstable ground, a phenomenon in which the formed sand pile is clogged (pile resistance) in a short time is caused. <C> Due to these reasons, there has been a major problem that predetermined consolidation does not proceed and improvement does not proceed. <D> In artificial landfill ground, the local hardness of the ground differs depending on the used embankment material. This has made it difficult to penetrate the sand pile at the time of placing the sand pile, and also impaired the continuity of the formed sand pile. <E> As described above, as shown in the pack drain and the like, a method for securing the continuity of the sand pile by using a covering material such as a net tube on the outer periphery of the sand pile (Patent No. 1524)
628) has also been proposed. However, these have a problem that clogging is more likely to occur due to the provision of a reinforcing material such as a cloth or a filter material on the outer periphery, and that the outer peripheral tubular member is raised together with the casing during construction.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for reinforcing a sand pile which can solve the above-mentioned drawbacks and problems of the conventional method. Further, the present invention can ensure the continuity of the sand pile as a conventional drainage member, deformation of the poured sand pile,
An object of the present invention is to provide a method for constructing a sand pile capable of significantly improving compression characteristics. A further object of the present invention is to provide a method for constructing a sand pile in which clogging by soil particles is less likely to occur. A further object of the present invention is to provide a method for constructing a sand pile which also has an effect of reinforcing the ground.

[0007]

That is, according to the present invention, an axially reinforced sand column is formed in the center of a drain hole formed in the ground, and the outer periphery of the reinforced sand column is
This is a method of constructing a reinforced sand pile by forming an unreinforced outer sand column. The present invention also provides a method for constructing a reinforced sand pile, comprising forming a reinforced sand column by pouring sand into a reinforced filter having a longitudinal reinforcing material at the center and covering the outer periphery with a filter. It is. Also, the present invention inserts a casing into a drain hole opened in the ground, locates a reinforcing sand column reinforced in the axial direction at the center of the casing, pulls out the casing while putting sand from the upper part on the outer periphery thereof. This is a method of constructing a reinforced sand pile by forming an outer sand column.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. <Overall Configuration> FIG. 1 shows a reinforcing filter 1 used in the construction method of the present invention. The reinforcing filter 1 is a filter member reinforced in the axial direction, which is constituted by a reinforcing member 11 housed therein and an outer peripheral filter 12 covering the outer periphery thereof.

<Internal Reinforcing Material> The internal reinforcing material 11 is, for example, a long member having a cross-shaped cross section. This reinforcing material 11
For example, a long plate made of a synthetic resin formed in a cross shape can be used, but a similar reinforcing material 11 can be formed using a perforated member instead of a plate. The reinforcing material 11 has a function as a vertical drain material in addition to restraining and reinforcing the sand, thereby making it possible to eliminate pile resistance which is a problem in the conventional sand drain.

<Outer Perimeter Filter> The outer periphery of the reinforcing member 11 is covered with an outer peripheral filter 12. This outer filter 1
Reference numeral 2 denotes a long sock-like bag made of a cylindrical cloth, synthetic resin, synthetic fiber, or the like. One reinforcing filter 1 is configured by coating the outer periphery of the reinforcing material 11 with the sock-shaped outer peripheral filter 12. The outer peripheral filter 12 itself may have water permeability. However, the outer peripheral filter 12 has a function as a filter for fine particles and a function to increase the restraint of sand filled in the inside. An effect of improving the deformation performance as a whole can also be expected.

<Outer Diameter of Reinforcing Filter> The reinforcing filter 1 is formed to have a diameter smaller than an outer diameter of a drain hole to be cast. For this reason, a space is generated between the inner surface of the drain hole and the outer surface of the reinforcing filter 1.
The space is filled with sand as described later to form the outer peripheral sand column 2. The outer peripheral sand column 2 naturally serves as a drainage layer, but also acts as a cushion for the reinforcing filter 1 of the present invention. The cushioning action is not only a cushioning action against the ground displacement, but also to prevent the outer peripheral filter 12 from being damaged and broken even when the concrete or the concrete piece always included in the landfill ground comes into contact.

[0012]

[Construction method] Next, the above-mentioned reinforcing filter 1 was used.
The method of constructing the sand pile will be described with reference to FIG. <Formation of Reinforced Sand Column> First, the above-described reinforcing filter 1 is located in the casing 3 whose end is closed by a lid.
Then, sand is put into the reinforcing filter 1 from the reinforcing sand column hopper 5 set on the upper part. Then, the outer peripheral filter 12 is filled with sand, and the reinforcing sand column 4 reinforced in the axial direction by the inner reinforcing material 11 is formed.

<Structure of hopper>
The inside of the reinforcing material filter 1 and the outer periphery thereof are divided into two parts so that sand can be charged and filled. Alternatively, it is also possible to use a single hopper and feed it in dividedly by a gate valve or a switching valve. The gate valve in this case has a structure in which a plurality of cylinder groups are rotatably arranged at the lower outlet of the hopper, and sand is supplied only through a predetermined cylinder by rotating the cylinder group. ...

<Formation of External Sand Column> The casing 3 containing the reinforcing sand columns 4 therein is inserted into the drain hole and penetrates to a predetermined depth of the ground. Next, sand is filled around the reinforcing sand column 4. Then, the outer peripheral sand column 2 is formed around the reinforcing sand column 4. Thus, the casing 3 is pulled out while forming the outer peripheral sand column 2. At this time, the bottom lid of the caning is opened, and only the casing is pulled out, leaving everything underground. The extraction is performed while vibrating. Thus, the reinforcing sand column 4 was provided inside, and the periphery thereof was surrounded by the outer sand column 2.
Construction of the reinforced sand drain is completed.

<Problem of Coupling of Reinforced Sand Column> Even when the casing 3 is pulled out by vibration, sand is charged into the inside of the reinforced sand column 4 prior to the drawing. Therefore, the reinforcing sand column 4 is fixed inside the casing 3 and does not rise when the casing 3 is pulled out. Furthermore, since the shape of the reinforcing sand column 4 has a certain hardness, it is also easy to adjust the position and dispose the reinforcing sand column at the central portion in the casing 3. Further, the rise does not occur.

<Experimental Example> The drain effect of the sand column of the present invention was compared with a conventional method. The results of the laboratory test are shown in FIG. The test was performed on the basis of the sample shape of φ50, l = 100, while changing the specifications of the drain material, and the side pressure σ ₃ = 1 kg /
The test was a triaxial test of cm ² . The test results show that the model of the reinforcing material of the present invention has a strength two to three times that of the case where the model is not reinforced, and furthermore, there is no sudden decrease in strength even if the strain progresses,
It is clear that a reinforcing effect is exhibited.

[0017]

According to the reinforcing method of the present invention as described above, the following effects can be achieved. <B> A sand pile having a structure in which a reinforcing sand column is provided inside and an outer sand column is provided on the outer periphery thereof can be obtained. Therefore, the deformation resistance and compression characteristics of the cast sand pile are remarkably improved, so that the continuity of the sand pile can be ensured over a long period even if the ground is deformed. <B> Further, clogging by soil particles hardly occurs. Underground water in the soft ground is discharged including fine clay particles. In this respect, in the method of the present invention, the groundwater is drained through the outer peripheral filter, so that the sand serves as a primary filter. Therefore, water containing clay particles, like a conventional paper drain, adheres to the outside of the outer filter in the form of a mud on the drain surface, and the original drain function expected of the reinforcing sand column is maintained for a long time. become. <C> Since the sand pile of the present invention has a strong reinforcing sand column inside, the reinforcing effect of the ground can be expected. Conventional various drain methods could only exert a drainage function. However, the method of the present invention can achieve a function as a ground reinforcement in addition to such a drainage function. <E> Therefore, even when preloading is performed, the height of the loaded embankment can be made higher than that of the conventional drain, so that it can be exhibited as an excellent merit in terms of shortening the construction period and economy. <F> Depending on the properties of the ground, it is possible to install reinforcing sand columns only at arbitrary locations in the ground. That is, it is possible to adopt a configuration in which a reinforcing sand column and an external sand column are not provided on the entire length of the sand pile, but the reinforcing sand column is provided only on the upper portion. <G> The reinforcing material diameter is smaller than the pile diameter.
By injecting and filling the sand inside and outside, the internal sand pile can function as a weight, and the casing can be prevented from rising together.

[0018]

[Brief description of the drawings]

FIG. 1 is an explanatory view of a reinforcing filter used in the construction method of the present invention.

FIG. 2 is an explanatory view of a construction method.

FIG. 3 is an explanatory view of a construction method.

FIG. 4 is an explanatory view of a construction method.

FIG. 5 is an explanatory view of a construction method.

Claims (3)

(57) [Claims] 1. A reinforced sand column reinforced in the axial direction is formed in the center of a drain hole formed in the ground, and an unreinforced outer sand column is formed on the outer periphery of the reinforced sand column. Sand pile construction method 2. A reinforcing sand column is formed by introducing sand into a reinforcing filter having a longitudinal reinforcing material at the center and covering the outer periphery with a filter.
The described invention 3. A casing is inserted into a drain hole formed in the ground, a reinforcing sand column reinforced in the axial direction is located at the center of the casing, and the casing is pulled out while sand is charged from above in an outer periphery thereof. 2. The invention according to claim 1, wherein the outer sand column is formed.