JPH0441729B2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a method for protecting an existing structure when construction such as a deep mixing method is carried out in the vicinity of the existing structure.

<<Prior art and its problems>> As is well known, when constructing a new structure near an existing structure, or when carrying out excavation or embankment work near an existing structure, it is necessary to Measures are taken to protect the property.

In this case, for example, if the existing structure is built on soft ground, the area around the existing structure is often improved and protected using a deep mixing method as a protection method.

However, this protection method has the following problems.

In other words, the deep mixing method is a method in which solidification material is injected while rotating a rod with stirring blades that penetrates into the soil, and the excavated soil and solidification material are mixed and stirred to form a compact in the soil. be.

Therefore, when creating a compact, the volume expands because the solidifying material is mixed with the excavated soil, and the soil pressure increases due to rod penetration and stirring by rotating blades.
Furthermore, since the pressing force of the solidification material is also added, the earth pressure in the excavation hole during the mixing process increases considerably.

Some of the earth pressure acts as a force to heave excavated soil above the ground, but most of it acts as lateral pressure on existing structures, and this lateral pressure can cause the existing structures to move or crack. effect.

This kind of influence on existing structures due to earth pressure is not limited to the deep mixing method, but also when constructing a new structure in close proximity to an existing structure.
It also occurs when earth retaining is formed by hammering.

This invention was made in view of the above-mentioned problems, and its purpose is to reduce soil damage when construction work that expands the ground volume, such as deep mixing treatment, is carried out near existing structures. An object of the present invention is to provide a method for protecting an existing structure that can prevent the influence of pressure from exerting on the existing structure.

≪Means for Solving the Problems≫ In order to achieve the above object, the present invention involves constructing work that expands the ground volume, such as pile driving or deep mixing method, in the vicinity of existing structures. At this time, an excavated hole or an excavated trench filled with a stabilizing liquid is formed around the existing structure.

≪Operation≫ According to the method for protecting an existing structure having the above configuration, even if the earth pressure increases due to deep mixing treatment or pile driving, for example, even if the earth pressure increases due to deep mixing treatment or pile driving, the existing structure can be protected by an excavated hole filled with stabilizing liquid or Since the excavated trench is formed, the increase in earth pressure acting on the existing structure is absorbed by raising the level of the stabilizing liquid.

<<Example>> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the method for protecting an existing structure according to the present invention.

The method shown in the figure is applied to constructing a new structure 14 almost directly above an underground tunnel 12 that has already been constructed in soft ground 10.

Prior to constructing the new structure 14, since the ground is soft, ground improvement is performed at the site where the new structure 14 is planned to be constructed, using, for example, a drain method.
Before ground improvement, column-shaped walls 16 are constructed along both sides of the underground tunnel 12 at predetermined intervals to protect the underground tunnel 12.

The column-shaped wall bodies 16 are formed by a deep mixing method, for example, according to the Japanese Utility Model Publication No.
Using an agitating mixer disclosed in Publication No. 17787 or Publication No. 169326 of 1987, a solidification material such as cement milk is pressed in, mixed with excavated soil, and a solidified body is formed by combining these materials. Forms in the soil.

In the present invention, prior to constructing the columnar wall 16,
At appropriate intervals around the underground tunnel 12,
An excavation hole 20 is formed filled with a stabilizing liquid 18 made of bentonite slurry or the like.

The excavation hole 20 is formed in the shape of a circular cross section or a narrow groove, and its position is, for example, in the underground tunnel 1.
The outside of 2 and the wall 1 created by deep mixing
6, and its depth is at least deeper than the deepest position of the underground tunnel 12;
More preferably, it is closer to the creation depth of deep mixing, and if the excavation hole 20 is formed to such a depth, the increase in earth pressure when constructing the wall 16 will cause the excavation hole 20 to By bypassing the lower end of the underground tunnel 12, it is possible to prevent the phenomenon of plate bulging that is applied to the bottom surface of the underground tunnel 12.

Further, the stabilizing liquid 18 in the excavated hole 20 is kept at a water level slightly lower than the ground surface.

Now, if the excavation hole 20 filled with the stabilizing liquid 20 is provided as described above, when constructing the wall 16, the penetration of the stirring mixer and the stirring of the rotary blades, the press-in of the cement milk, and the Even if the earth pressure increases due to factors such as volumetric expansion, the increased earth pressure is prevented from acting on the underground tunnel 12 as lateral pressure.

In other words, since the excavation hole 20 is interposed between the wall 16 and the underground tunnel 12, when the increased earth pressure reaches the wall of the excavation hole 20, it pushes one wall of the excavation hole 20 toward the other wall. The lateral pressure acts as a lateral pressure, which is released by increasing the water level of the stabilizing liquid 18 in the borehole 20, and the underground tunnel 12
It is not transmitted to the sides.

Furthermore, the excavated hole 20 may of course be in the form of a continuous groove.

FIG. 2 shows another embodiment of the protection method according to the invention.

The protection method shown in the figure is to apply a deep mixing treatment to the back of the abutment 32 in order to prevent the abutment 30 and its foundation 32 from becoming unstable when the river bed soil is excavated and removed as shown by the imaginary line. This example shows the case where it is applied during construction.

On the back side of the abutment 30 including the foundation 32, a consolidated ground 34 is formed by deep mixing treatment as in the above embodiment, but prior to this, an excavation hole 20 filled with stabilizing liquid 18 is formed around the abutment 32. do.

In this embodiment, the excavated hole 20 is excavated to approximately the same depth as the consolidated ground 34, and the lateral displacement of the foundation 32 and abutment 30 due to the expansion of the ground volume when forming the consolidated ground 34 is compensated for by the excavated hole 20. 20 and the stabilizing liquid 18 to prevent the effects thereof.

In addition, in the above embodiment, the case where the new structure 14 is constructed directly above the underground tunnel 12 and the case where the consolidated ground 34 is formed on the back of the abutment 30 are exemplified. It can also be applied when constructing a structure, for example when driving piles for earth retaining.

<<Effects of the Invention>> As described above in detail in the examples, the method for protecting an existing structure according to the present invention has a relatively simple method of forming an excavation hole by filling the surrounding area of the existing structure with a stabilizing liquid. With a simple configuration, when constructing a new structure or improving the ground, it is possible to reliably eliminate the adverse effects of earth pressure that increases as the ground expands.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the method of the present invention, and FIG. 2 is a sectional view showing another embodiment of the method. 10...Soft ground, 12...Underground tunnel, 1
4...New structure, 16...Wall body, 18...Stabilizing liquid, 20...Drilling hole.

Claims (1)

[Claims] 1 Existing construction characterized by forming an excavation hole or excavation trench filled with stabilizing liquid around the existing structure when implementing the deep mixing method or driving piles in the vicinity of the existing structure. How to protect structures.