JP2001020275A - Foundation ground improving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the ground such as sand ground which is in danger of liquefaction, and soft ground which is in danger of consolidation settlement, prior to utilization of the ground as foundation ground of a structure, and to provide stable ground as the foundation ground of the structure. SOLUTION: In the ground A supporting a structure and containing stratums B, C in which liquefaction or consolidation settlement can be expected in the event of an earthquake, vertical consolidating piles 1 each reaching a predetermined depth from the surface of the ground are arranged at predetermined intervals in a plurality of rows, to thereby construct a vertical column consolidating pile group 2. Then, a horizontal consolidating board 3 is constructed on the upper edge of the vertical column consolidating pile group 2 so as to be combined therewith in one body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In the case where sandy ground that may be liquefied or softly viscous ground that causes consolidation settlement is used as the foundation ground for a structure, the ground is improved to a stable foundation ground in advance. Need to do. The present invention relates to a method for improving a foundation ground which can improve the soft ground to a stabilized ground and can be used as a ground suitable for a construction.

[0002]

2. Description of the Related Art An unstable ground, such as a sandy ground that may liquefy during an earthquake or a soft viscous ground that causes long-term consolidation settlement, is used as a foundation ground for a structure. It is necessary to improve the unstable ground to a stable ground in advance. In addition, most of the soft ground inland and inland areas of Japan are composed of a layer of soft cohesive soil deposited in the lower part and loose sand and volcanic ash deposited in the upper part. It is necessary to take measures against liquefaction for the upper sedimentary layer and measures against consolidation settlement for the lower sedimentary layer.

[0003] As a method of improving the ground as a measure against liquefaction or consolidation settlement, for example, as a measure against liquefaction, a solidified material milk such as cement is injected into the ground that may be liquefied, and the injected solidified material milk is added. It is generally known to stir and mix excavated soil and soil to solidify the ground that may be liquefied to obtain a stable ground.

Further, by forming a continuous wall formed by constructing vertical walls in a plane lattice shape in the ground which may be liquefied, the movement of groundwater and soil during an earthquake is blocked by the continuous wall. 2. Description of the Related Art A method of stabilizing a ground that may be liquefied is known.

[0005]

However, the method of solidifying the entire ground which may be liquefied by stirring and mixing the solidified milk and excavated soil consumes a large amount of solidified milk such as cement. However, there is a problem that the cost is extremely increased due to the overall improvement.

Further, the method of constructing a continuous lattice-shaped continuous wall composed of vertical walls in a soft ground requires a considerable number of improvements in order to prevent liquefaction, and furthermore, the sandy ground in the upper part and When the lower soft ground is improved at the same time, a single continuous wall is constructed, which is uneconomical and has a problem that the cost is considerably increased.

Further, in the method of constructing a continuous columnar solidified wall in the ground, the next solidified pile is constructed while shaving the side face of the previously constructed solidified pile because it is necessary to functionally construct the impermeable wall. Therefore, the stirring rod tends to move in the direction of low resistance, and the solidified pile is bent and constructed in the depth direction, and even the side of the solidified pile constructed earlier due to delays in construction is cut off. There is a case where it is impossible, and there is a problem that it is difficult to construct an impermeable wall composed of a continuous columnar solidified wall.

[0008] In the method of solidifying the entire ground and the method of constructing the continuous columnar solidification wall as described above, the flow of groundwater is interrupted, which may have a great adverse effect on the surrounding environment.

[0009] In the method of constructing a continuous grid-like continuous wall in the ground to be improved, since the unimproved portion is left in the flat grid, the upper structure may collapse during an earthquake.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method for improving the foundation ground according to the present invention includes a method for obtaining a predetermined amount of ground from the ground surface of a ground where liquefaction is expected to occur during an earthquake. A vertical solidification pile group is formed by placing a plurality of vertical solidification piles reaching the depth with a predetermined gap, and a vertical solidification pile group is formed at the upper end of the vertical columnar solidification material group. The construction method was to improve the foundation ground.

[0011] Another object of the present invention is to provide a method of improving a foundation ground in which one or more vertical solidified pile groups and a horizontal solidified board integrated with the vertical solidified pile groups are provided at one or more stages at predetermined intervals as necessary.

According to the method of improving the foundation ground according to the present invention, a vertically solidified pile is provided in a ground which may be liquefied, and a gap capable of suppressing water and soil rocking to some extent at the time of an earthquake, that is, a vertical gap is provided at a predetermined interval. A plurality of solidification piles are constructed to form a vertical column solidification pile group, and an upper horizontal solidification board integrated with the vertical column solidification pile group is provided. If necessary, an intermediate horizontal solidification board is integrally constructed. Therefore, it is possible to increase the supporting capacity of the vertical and horizontal loads and to prevent the collapse of the upper structure during an earthquake. Further, vibration and shaking of the foundation ground can be reduced, liquefaction can be reduced, and liquefaction ground can be stabilized. At the same time, by constructing vertical column-solidified pile groups on soft clay ground, it is possible to construct a stabilized ground that prevents consolidation settlement.

Further, the present invention is an improvement of the foundation ground based on a combination of the horizontal solidification board as described above and a vertical column solidification pile group which is cast with a predetermined gap provided between the solidification piles. Therefore, since the groundwater is not blocked, a foundation ground that is friendly to the surrounding environment can be obtained.

Further, the present invention efficiently reduces the liquefaction by constructing the horizontal solidified ground and the vertical column solidified pile group efficiently, as compared with the method of solidifying the whole and the method of constructing the plane grid. Prevention of consolidation settlement of soft viscous ground can be efficiently and inexpensively constructed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method of improving the foundation ground according to the present invention will be described with reference to the drawings. As shown in FIG. 1, a liquefied layer close to the ground surface above the ground A which may be liquefied. The vertical solidified pile 1 reaching the hard supporting ground G below the ground B and the soft viscous ground C which is likely to settle is inserted into the predetermined gap S.
Then, a plurality of rows are cast in the vertical direction to form a vertical column row solidified pile group 2. A horizontal solidification board 3 integrated with the vertical column row solidification pile group 2 is cast on the upper surface of each vertical column row solidification pile group 2, and the vertical column row solidification pile group 2 and the horizontal solidification board 3 are constructed to form a liquefied ground layer B and softness. Improvement of the cohesive ground layer C is also performed.

An improvement comprising the vertical column-solidified pile group 2 constructed in the ground B where there is a possibility of liquefaction, and the horizontal solidified material disk 3 integrally provided at the upper end of the vertical column-solidified material group 2 Construction of the foundation ground shall be one or more steps.

The construction procedure of the method for improving the foundation ground according to the present invention will be described with reference to FIG.
After setting the stirring rod 4 having the stirring blade 6 and the high-pressure jet nozzle at the tip at the construction position of the ground A to be improved, the lower end of the planned improvement depth, that is, the support base G is rotated while the stirring rod 4 is rotated forward. Until the soil amount corresponding to the mixed amount of the solidified material is discharged, the low displacement construction is carried out to penetrate the soil 7. Alternatively, construction without earth removal is performed.

After the stirring rod 4 has penetrated to a predetermined depth, the solidification material milk 8 is injected at a high pressure from the stirring rod 4 provided with a high-pressure injection nozzle, and the stirring blade 6 of the stirring rod 4 is rotated. The stirring rod 4 is gradually pulled out while agitating and mixing the solidified milk and the raw soil with a high-pressure jet, and the solidified milk and the raw soil are mixed into the liquefied layer B of the ground A where there is a possibility of liquefaction. After the vertical solidification pile 1 is formed and is improved to the planned improvement top end, the top end treatment is performed and the empty hitting portion is pulled out. This operation is sequentially repeated to construct a vertical column-solidified pile group 2 composed of a plurality of vertical solidified piles 1 in the liquefied ground layer B and the soft viscous ground layer C. The vertically solidified pile 1 is cast with a predetermined gap S therebetween.

This method prevents the vertical solidification pile 1 from being bent, which cannot be avoided by the conventional method, thereby enabling the vertical construction of the vertical columnar solidification pile, and further includes a stirring blade 6 with an injection nozzle as necessary. And the injection rod 4 is repeatedly penetrated and pulled out to integrally form the vertical column row solidification pile group 2 composed of many vertical column row solidification piles, the upper horizontal solidification board 3 and the intermediate horizontal solidification board 3a. Therefore, the soft ground ground layer C is improved together with the improvement of the liquefied ground layer B, so that a favorable foundation ground can be formed.

It should be noted that the embodiments of the invention of this application are not limited to the above-described embodiments.
Various modes can be adopted for the stirrer, such as using air in combination.

[0021]

As described above, the present invention has an efficient combination of a horizontal solidification plate and a vertical column-solidification pile group, so that liquefaction is reduced and consolidation settlement of soft viscous ground is prevented. For the purpose of improving the solidification of the sand ground, and the effect of improving the solidification of the sand ground, there is no inferiority to the conventional overall improvement method, and therefore, not only measures against liquefaction of the sand ground, but also measures against consolidation settlement of soft viscous ground Can also be implemented at lower cost.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing an arrangement of a vertically solidified pile and an upper middle horizontal solidified board in a foundation ground improvement method of the present invention.

FIG. 2 is a longitudinal sectional view showing a construction procedure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical solidification pile 2 Vertical column solidification pile group 3 Upper horizontal plate 3a Intermediate horizontal plate 4 Stirrer rod 5 Auger screw 6 Stirrer blade 7 Discharge 8 Solidification material milk A Ground to be improved B Liquefied ground layer C Soft viscous ground layer G Support ground S Gap

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Asami Matsuda 2-17-4 Yanagibashi, Taito-ku, Tokyo Onoda Chemico Co., Ltd. F-term (reference) 2D040 AA00 AB03 AC02 AC05 BA06 BA08 BB03 BC01 BD03 BD05 CB03 DB07

Claims (2)

[Claims] 1. A plurality of rows of vertically solidified piles having a predetermined gap provided between a ground supporting a building and a ground where a liquefaction is predicted to occur during an earthquake and reaching a predetermined depth from the ground surface of the ground. A method of improving a foundation ground, comprising forming a group of solidified vertical column piles formed by casting, and constructing a horizontal solidified plate integrated with an upper end of the group of solidified vertical column materials. 2. The foundation according to claim 1, wherein one or more vertical solidification pile groups and a horizontal solidification board integrated with the vertical solidification pile group are provided at predetermined intervals as needed. Ground improvement method.