JP2816267B2 - Ground fluidization prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new construction method for preventing ground fluidization due to an earthquake.

[0002]

2. Description of the Related Art Soft ground with a high groundwater level is subject to liquefaction when the whole ground is subjected to strong vibration due to an earthquake or impact, and the ground is loosened and loses its bearing capacity. As a result, it has been recorded in Japan that a great deal of damage has been caused to various structures. The phenomenon in which sand or water flows out at this time is called fluidization of the ground. In order to prevent liquefaction, there are roughly a method of compacting the ground and a method of making underground water easily drained, and the following construction methods are also known.

(1) Sand compaction pile method As shown in FIG. 3, this method employs a sand compaction pile method around a structure 2 supported by a foundation pile 1 reaching a non-liquefied ground 11 located below a liquefied ground 10. Then, sand is pressed into the liquefied ground 10 by applying an impact load or a vibration load to form a sand pile 3 around the structure 2. In this method, the ground around the sand pile 3 is compacted to make the liquefied ground 10 non-liquefied, and that portion receives the flowing earth pressure of the ground during an earthquake.

However, if the earthquake continues for a long time, or if a history of a medium-scale earthquake is received before a large earthquake occurs, the ground is loosened and the ground in the improved portion is eroded. There is a problem that an effect cannot be expected.

(2) Method for Preventing Fluidization Using Geotextile In this method, as shown in FIG. 4, a plastic net having support piles 5 at appropriate intervals in liquefied ground 10 around structure 2 is used. By arranging the geotextile 6 such as a nonwoven fabric, lateral flow of the direct foundation plate of the structure 2 due to liquefaction is prevented. This method requires considerable strength for the geotextile 6 and also involves difficulty in inserting the geotextile 6 into the liquefied ground 10.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a construction method which is easy to carry out and can surely prevent fluidization of the ground.

[0007]

The method for preventing fluidization of the ground according to the present invention comprises:
In the liquefied ground around the structure, while installing a water shield having an upper surface inclined toward the structure, improving the ground of the liquefied ground located inside the water shield. Things.

[0008]

The earth pressure flowing on the structure foundation during the earthquake is avoided on the ground surface along the slope of the impermeable body, so that the flow and deformation of the structure foundation are reduced. Further, infiltration of interstitial water is prevented by the impermeable body in the non-liquefied or hardly liquefied improved ground, so that the liquefaction resistance of the improved ground is maintained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a part of a liquefied ground 10 in a longitudinal section, and a structure 2 is supported by a foundation pile 1 reaching a non-liquefied ground 11 located in a lower layer. In the liquefied ground 10 around the structure 2, a water shield 8 having an inclined surface from the lower part to the upper part toward the structure 2 is installed.

The water shield 8 has a structure capable of blocking water permeation in the liquefied ground 10, and prevents intrusion of pore water from the outside to the inside (around the structure 2) of the water shield 8.
The liquefaction resistance of the ground 12 located inside the water shield 8 is maintained. As a specific material, a steel material, a concrete material, a plastic material, or the like having good water barrier performance can be used. Further, the rigidity of the water shield 8 is sufficient if the rigidity does not cause large deformation with respect to the flowing earth pressure. Impermeable body 8
As shown by reference numeral 8a, the upper surface may have a shape in which the upper surface is inclined toward the inside of the structure 2 and the lower surface is a vertical surface. By using a vertical surface, the construction becomes easier and the cost is reduced.

[0011] By adopting the above configuration, the flowing earth pressure of the ground applied to the structural foundation such as the foundation pile 1 during the earthquake is released to the upper ground surface along the inclined surface of the impermeable body 8,
The flow and deformation amount of the structure foundation can be reduced.

Further, the ground 12 located inside the impermeable body 8
It is necessary to improve the ground and make the ground 12 non-liquefied or hardly liquefied. The ground improvement may be performed by an appropriate method such as compaction, injection and solidification, which is generally performed. Ground 1 with the above ground improvement
2 is surrounded by the impermeable body 8, and the improvement effect more than the non-liquefied or hardly liquefied ground by simple ground improvement can be expected.

FIG. 2 is a plan view showing an example of the arrangement of the water shield 8, and the arrows in FIG. 2 indicate the direction in which the flowing earth pressure acts. 2 (a) and 2 (b) show a structure in which the water shield 8 is linearly arranged to flow the fluid earth pressure over a large area of the water shield 8, and is suitable for construction on a relatively large-scale structure 2. ing.

FIGS. 2 (c) and 2 (d) show that, depending on the conditions at the site, the impermeable body 8 is provided with an angle with respect to the flowing earth pressure direction, or is arranged in a curved line to reduce the flowing earth pressure by a small amount of the impermeable body 8. We receive in area. Although the construction of the water shield 8 is somewhat complicated, the resistance to fluidization increases because the fluid earth pressure can be received in the horizontal direction. Further, the area of the ground 12 where the ground improvement is to be performed can be reduced.

[0015]

According to the present invention, by adopting the above configuration, the flowing earth pressure of the ground on the structure foundation can be released to the ground surface, and the flow and deformation of the structure foundation can be reduced.

Further, if the present method is applied in a stitch shape to an area where danger of lateral ground flow due to liquefaction occurs, a wide area and large-scale lateral flow can be achieved without implementing liquefaction countermeasures in the entire area. Disasters can be prevented. Further, by performing the stitching, the liquefied layer is surrounded, and there is an excellent effect that the liquefaction strength in the outer region of the improved ground can be increased.

The present construction method can be applied not only to the construction ground, but also to new constructions and existing structures.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a state in which a water shield 8 is installed in a liquefied ground 10. FIG.

FIG. 2 is a plan view showing an arrangement example of a water shield 8;

FIG. 3 is a sectional view (a) and a plan view (b) showing an outline of a conventional sand compaction pile method.

FIG. 4 is a cross-sectional view (a) and a plan view (b) showing an outline of a fluidization prevention method using a geotextile as a conventional example.

[Description of Signs] 2 Structure 8 Water impervious body 10 Liquefied ground 11 Non-liquefied ground 12 Liquefied improved ground

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-132923 (JP, A) JP-A-60-37324 (JP, A) JP-A-51-128110 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) E02D 27/34 E02D 3/12 E02D 31/08

Claims (1)

(57) [Claims] 1. In a liquefied ground around a structure, a water shield having an upper surface inclined toward the structure is installed, and the liquefied ground located inside the water shield is ground-improved. A method for preventing ground fluidization, characterized in that: