JPH108451A - Soil improving work method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil improvement work method, by which the soil under the existing structure is improved to prevent liquefaction. SOLUTION: A soil improvement work method comprises the steps of advancing in soil subjected to soil improvement by an auger while a designated casing is pressed in for earth-moving (step 103), throwing in fluid drain material such as sand or the like in the casing after the completion of advancing (step 104), subsequently reversing the auger to feed the drain material forward (step 105) and further performing soil compaction for the fed sand by air compression (step 106). Subsequently, the casing and the auger are pulled by a designated distance (step 107), again feeding of fluid drain material and compaction work are performed, and these steps (step 104-step 107) are repeatedly conducted until the drain material is filled up to the whole of the drilled hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement method particularly suitable for liquefaction countermeasures.

[0002]

2. Description of the Related Art When seismic force acts on a sandy ground where the groundwater level is shallow and loose, a so-called liquefaction phenomenon occurs in which the pore water pressure between particles rises and the shearing resistance decreases significantly.
As measures to prevent such liquefaction, there are sand compaction method and crushed stone drain method, but the latter method is
It is a useful construction method in urban areas because liquefaction of sandy ground can be prevented without performing compaction work that causes noise and vibration.

[0003]

However, since these construction methods have been developed on the premise that they are constructed in a vertical direction from the ground surface, for example, the seismic standards are reviewed and the lower ground of existing buildings is reviewed. In the case where it is necessary to reinforce such a method, there has been a problem that these methods cannot be adopted.

[0004] In addition, in the high-pressure injection system construction method, it is conceivable that the excavation axis is installed obliquely to perform injection stirring.
There is a problem in terms of restrictions on the installation angle and the like, and there has been a problem that it is difficult to reliably perform ground improvement.

The present invention has been made in view of the above circumstances, and has as its object to provide a ground improvement method capable of preventing liquefaction by improving the ground below an existing structure.

[0006]

According to a first aspect of the present invention, there is provided a ground improvement method for excavating a ground to be ground improved with an auger while press-fitting a predetermined casing into the ground. After discharging and excavating, a fluid drain material such as sand is charged into the casing, the auger is inverted, and the fluid drain material is sent forward,
The fluid drain material fed is compacted by air compression, and the charging step to the compacting step are performed in parallel or alternately with the step of pulling out the casing and the auger. The filling is performed sequentially from the tip.

In the ground improvement method according to the present invention, the ground to be ground-improved is excavated and discharged by an auger while a predetermined casing is pressed into the ground, and after the excavation is completed, the ground inside the casing is removed. A fluid drain material such as sand into the auger, inverting the auger and feeding the fluid drain material forward, compacting the fed fluid drain material by the forward and backward movement of the auger, The compacting step is performed in parallel or alternately with the step of extracting the casing and the auger, thereby sequentially filling the fluid drain material from the tip of the drilling hole.

In the ground improvement method of the present invention, a fluid drain material such as sand is charged into the casing after the excavation hole is formed, and then the auger is inverted and the drain material is fed forward. Then, the fed fluid drain material is compacted by air compression or forward and backward movement of the auger. In this way, even if the drilling hole is in the horizontal direction, for example, the fluid drain material can be sequentially filled from the tip of the drilling hole.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ground improvement method of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a flowchart showing the overall flow of the ground improvement method according to this embodiment, and FIGS.
It is a figure showing a construction procedure along such a flow.

In the ground improvement method according to the present embodiment, first, as shown in FIG. 2A, a region below the existing structure 1 is set as a ground to be ground-improved. Excavating the working shaft 2 (FIG. 1, step 101);
A small-diameter thruster 3 including a propulsion jack, a pressure receiver, a guide rail and the like is installed in the working shaft 2 (step 102).

Next, a casing 4 is mounted on the small-diameter thruster 3, and an auger 5 is disposed inside the casing 4.
As shown in (b), while the casing 4 is being press-fitted by the small-diameter thruster 3, the horizontal hole 7 is excavated by the bit 6 attached to the tip of the auger 5, and the shear generated by the excavation is worked by the auger screw 8. The soil is discharged to the side of the shaft 2 (step 103).

The casing 4 and the auger 5 are divided into units each having a predetermined length as shown in FIG. It is good to connect at the feed side of the, and press-fit it into the ground. In addition, if air is blown out from the discharge port 9 provided at the tip of the auger 5, the excavated soil can be efficiently discharged to the shaft in combination with the transport action of the auger screw 8.

After completion of the excavation, as shown in FIG. 3 (a), sand 12 as a fluid drain material is put into the casing 4 via the hopper 11 (step 104), and then, as shown in FIG. 3 (b). As shown, the auger 5 is turned over and the sand 12 is fed forward (step 105).

Next, as shown in FIG. 3C, air is blown from the discharge port 9 to compress and compact the sand 12 (step 106).

Next, as shown in FIG. 3 (d), the casing 4 and the auger 5 are pulled out by a predetermined distance (step 107), and the sand 12 is again charged, fed and compacted. Then, the procedure (steps 104 to 10)
By repeating step 7), the entire excavation hole 7 is filled with sand 12 as shown in FIG.

After the filling operation of the sand 12 is completed,
The working shaft 2 may be used as a pit for collecting water,
After a predetermined drain layer and pumping equipment are installed at the bottom of the shaft 2, the shaft 2 may be backfilled.

In the work of feeding the sand 12,
Withdrawal speed of casing 4 and auger 5, hopper 1
By continuously monitoring the supply speed of the sand 12 to 1 and the rotational load of the auger, the degree of the filling of the sand 12 is constantly grasped.

When the sand 12 is filled in the excavation hole 7 in this way, a sand pile made of the sand 12 is formed in the horizontal direction. Such a sandpile acts as a drain to prevent liquefaction, preventing pore water pressure from rising in the surrounding ground during an earthquake, and increasing excess pore water pressure early after the earthquake. Dissipate.

As described above, according to the ground improvement method of the present embodiment, after the excavation hole is formed, sand is put into the casing to invert the auger, and the sand is fed forward by the screw of the auger. Therefore, even if the drilling hole is horizontal, for example, it is possible to sequentially fill the sand from the tip of the drilling hole.

Therefore, even when an existing structure exists on the ground surface, a liquefaction can be prevented by constructing a sand pile in the ground below the ground in a horizontal direction.

Further, since the fed sand is compressed by air and compacted, the portion replaced as a sand pile has an effect of being a high-density high-quality soil.

In the present embodiment, a series of operations from the introduction of sand to the compaction are performed alternately with the operation of pulling out the casing and the auger, but it goes without saying that these operations may be performed in parallel. Also, in a series of steps of charging, feeding, and compaction of sand, sand may be continuously charged while inverting the auger, and air may be continuously blown from the tip of the auger.

In this embodiment, the case where the excavation hole is horizontal is described. However, any direction can be selected as the direction, and the direction is obliquely downward or obliquely upward according to the situation at the site. An excavation hole may be formed in the hole to be filled with sand.

In this embodiment, it is assumed that a work shaft is provided. However, for example, when the work is performed horizontally from a slope of a slope, such a work shaft is not necessary.

In this embodiment, horizontal excavation is performed by the small-diameter propulsion method. However, horizontal excavation may be performed by, for example, a horizontal boring method.

In the present embodiment, the purpose of ground improvement is prevention of liquefaction, but the present invention is not limited to this purpose. For example, the ground improvement method of this embodiment is employed for the purpose of improving the strength of viscous ground. May be.

When the present method is applied to the viscous ground, the sand pile formed in the target ground below the existing structure 1 efficiently drains pore water contained in the surrounding viscous ground to promote consolidation. I do. In addition, the compaction force due to the air compression extends to the surrounding ground to further enhance the compaction.

Further, in this embodiment, the fed fluid drain material is compacted by air compression, but the auger may be moved back and forth to compact the fluid drain material at its tip or auger screw. Good.

[0030]

As described above, in the ground improvement method of the present invention, as described in claim 1, the ground to be ground improved is excavated and discharged by an auger while press-fitting a predetermined casing. After the completion, a fluid drain material such as sand is charged into the casing, the auger is inverted, and the fluid drain material is fed forward, and the fed fluid drain material is compacted by air compression. The step or the compacting step is performed in parallel or alternately with the step of extracting the casing and the auger, so that the fluid drain material is sequentially filled from the tip of the drilling hole. Even with this, ground improvement for the purpose of preventing liquefaction can be performed.

Further, according to the ground improvement method of the present invention, the ground to be ground improved is excavated and discharged by an auger while a predetermined casing is pressed into the ground, and after excavation is completed, the ground in the casing is removed. A fluid drain material such as sand into the auger, inverting the auger and feeding the fluid drain material forward, compacting the fed fluid drain material by the forward and backward movement of the auger, Since the compacting step is performed in parallel with or alternately with the step of extracting the casing and the auger, the fluid drain material is sequentially filled from the tip of the excavation hole, so that even under the existing structure, Ground improvement for the purpose of preventing liquefaction can be performed.

[0032]

[Brief description of the drawings]

FIG. 1 is a flowchart showing a flow of a ground improvement method according to an embodiment.

FIG. 2 is an explanatory view showing a construction procedure of a ground improvement method according to the present embodiment, where (a) is an overall view showing a state where horizontal excavation is performed by an auger while propelling and press-fitting a casing;
(b) is an enlarged detailed view of the auger tip.

FIG. 3 is an explanatory view showing a construction procedure of a ground improvement method according to the embodiment, where (a) is a view showing a state where sand is charged into a casing via a hopper, and (b) is a view showing Is a diagram showing the sand being fed forward by inverting the auger, (c) is a diagram showing the sand compacted by air compression, and (d) is a diagram showing the casing and the auger. The figure which showed a mode that it was pulled out.

FIG. 4 is an explanatory view showing a construction procedure of the ground improvement method according to the embodiment, showing a state in which sand is completely filled in the entire excavation hole.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Existing structure 2 Working shaft 4 Casing 5 Auger 7 Drilling hole 12 Sand (drain material)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuyoshi Nishio 2-17-4 Yanagibashi, Taito-ku, Tokyo Inside of Onoda Chemiko Co., Ltd. (72) Inventor Masanori Iwaki 2-17-4, Yanagibashi, Taito-ku, Tokyo Chemiko Onoda Inside the corporation

Claims (2)

[Claims] 1. Excavating and excavating the ground to be ground-improved with an auger while press-fitting a predetermined casing, and after completing the excavation, introducing a fluid drain material such as sand into the casing and inverting the auger. Then, the fluid drain material is fed forward, the fed fluid drain material is compacted by air compression, and the charging step or the compacting step is performed in parallel or alternately with the step of extracting the casing and the auger. A ground improvement method characterized by sequentially filling the fluid drain material from the tip of a drill hole by performing the method. 2. Excavating and excavating the ground to be ground-improved with an auger while press-fitting a predetermined casing, and after completion of the excavation, introducing a fluid drain material such as sand into the casing and inverting the auger. Then, the fluid drain material is fed forward, and the fed fluid drain material is compacted by the forward and backward movement of the auger, and the charging step or the compacting step is performed in parallel with the step of extracting the casing and the auger. Alternatively, the ground improvement method is characterized in that the fluid drain material is sequentially filled from the tip of a drill hole by alternately performing the same.