JPS6312962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the foundation ground under an embankment, and more specifically, the present invention relates to a method for improving the foundation ground under an embankment, and more specifically, a method that does not require injection of injection material into the upper part of the foundation ground that is to be improved by injection of injection material, or a method that does not require injection of injection material into the upper part of the foundation ground that is to be improved by injection of injection material. When there is an embankment layer that should not be used and the only way to inject into the foundation ground is through that embankment layer, this method is used to improve the foundation ground by more reliably injecting the material into the foundation ground. This article concerns a ground improvement method for foundation ground.

File-type dams and river embankments are constructed by embanking the foundation ground. When performing ground improvement by injecting grouting material into the foundation ground of such a file-type dam or river embankment, the injection pressure may not be sufficient, especially when improving soil with shallow soil cover, due to the high permeability of the embankment. This is very difficult due to the fact that the injection material cannot be added to the ground and there is a lot of leakage of the injection material to the surface. In contrast, conventional construction methods either leave the required thickness of the foundation ground near the embankment and use the remaining part as cover rock to pour into the foundation ground, or pour concrete to the required thickness and pour it on top. Boring was performed and the concrete was poured into the foundation ground as cover rock.

However, from the perspective of the injection effect, the former method requires that the ground left in the upper layer is generally more permeable than the lower layer, that is, it is a poor ground that allows the injection material to easily penetrate, and even if the lower layer is injected, it will not work. In many cases, much of the injection material flowed into the upper cover lock, resulting in insufficient ground improvement effects. In addition, when using the latter method, a nearly satisfactory effect can be obtained in terms of the injection effect, but leaving concrete solids with different physical properties in the embankment may impair the safety of the dam, etc. Therefore, this method is disadvantageous in terms of cost since the concrete solids must be removed after the pouring work is completed.

The present invention solves the above-mentioned problems of the conventional method when improving the foundation ground by injecting pouring material into the foundation ground below the embankment layer through the embankment layer built on the foundation ground, and ensures that the foundation ground The purpose of this project was to provide a ground improvement method that could be used to improve soil quality and at low cost.

Therefore, according to the construction method of the present invention, a hole with a diameter larger than the injection hole is drilled in the embankment layer at least until it reaches the boundary between the embankment layer and the foundation ground, and the inside of the large diameter hole has physical properties similar to those of the embankment layer. Fill with cement craig grout as a self-hardening filler, and after the cement craig grout has hardened, an injection hole of the required length is drilled into the foundation ground through the hardened cement craig grout. A construction method is provided for improving the foundation ground by injecting an injection material into the foundation ground through a hole.

Further, according to the present invention, a hollow tube with a bottom having an outer diameter equal to or slightly larger than the diameter of the injection hole is inserted before or after filling the cement craig grout into a hole having a larger diameter than the injection hole. After the cement craig grout has hardened, the hollow tube with a bottom is pulled out, and an injection hole of the required length is inserted into the foundation ground through the space formed in the hardened cement craig grout by pulling out the hollow tube with a bottom. A construction method is provided in which only the holes are drilled.

Furthermore, according to the present invention, a hollow tube having an inner diameter equal to or slightly larger than the diameter of the injection hole is inserted before or after filling the cement craig grout into the hole having a larger diameter than the injection hole, and the hollow tube is A construction method is provided in which an injection hole is drilled by a required length into the foundation ground through a pipe.

Although it depends on the soil quality of the embankment, cement craig grout is usually suitable as cement craig grout.

The filling material filled in the embankment in this way becomes a cover lock, and the material can be injected into the foundation ground with the necessary injection pressure.
The cement clay grout prevents the injected material from rising along the vicinity of the injection hole, preventing it from flowing into the embankment, allowing reliable ground improvement of the foundation ground. Furthermore, since cement craig grout has self-hardening properties and has physical properties similar to those of embankment, there is no need to remove the cement craig grout after the pouring work is completed, which is advantageous in terms of cost.

Embodiments of the present invention will be described below with reference to the drawings. 1a to d show a first embodiment of the present invention. In the figures, 1 is an embankment, and this embankment 1 is, for example, a river embankment material placed on a foundation ground 2, and this embankment layer Inject the injection material into the foundation ground 2 through 1.

First, as shown in FIG. 1a, a hole 3 having a larger diameter than the injection hole 5 is bored in the embankment layer 1. This large-diameter hole 3 reaches the boundary surface S between the embankment layer 1 and the foundation ground 2, or reaches the foundation ground 2 to a certain depth. To drill this hole 3, a construction method that does not deteriorate the embankment layer 1, such as an auger construction method or an anhydrous casing construction method, is preferable.

Next, as shown in FIG. 1b, the large diameter hole 3 is filled with cement clay grout 4 as a self-hardening filler. This cement craig grout 4 has physical properties after hardening that are equal to or close to those of the embankment layer 1 within a permissible range, and cement craig grout is usually preferred.

After the cement craig grout 4 has hardened, the first
As shown in Figure c, an injection hole 5 is bored through the cement craig grout 4 to a required length into the foundation ground 2 by a commonly used construction method. Next, an injection pipe 6 is inserted into the injection hole 5, a packer 7 is engaged between the outer peripheral wall of the injection pipe 6 and the inner peripheral wall of the hole 5, and the injection material is injected into the foundation ground 2 through the injection pipe 6. . At this time, the cement craig grout 4 acts as a cover lock to obtain the required injection pressure, and the cement craig grout 4 prevents the injected material from rising along the vicinity of the injection hole 5, so that the embankment layer 1 is prevented from flowing into the room.

When the injection work is completed, as shown in FIG. 1d, the injection pipe 6 is removed and the holes in the cement craig grout 4 are filled with a filler made of the same material as the cement craig grout 4. Thereby, the foundation ground 2 under the embankment body can be improved with the injection material without damaging the embankment body, which is the embankment layer 1.

FIGS. 2a and 2b show a second embodiment of the present invention, in which a hole 3 having a larger diameter than the injection hole 5 is bored in the embankment layer 1 in the same manner as in the first embodiment. As shown in FIG. 2a, a hollow tube 8 with a bottom 8a is inserted into the hole 3 before or after filling the cement craig grout 4. This hollow tube 8 has an outer diameter that is equal to or slightly larger than the diameter of the injection hole 5.

Next, as shown in FIG. 2b, once the cement craig grout 4 has hardened, the bottomed hollow tube 8 is pulled out, and the bottomed hollow tube 8 is pulled out to pass through the space 8b formed in the cement craig grout 4. An injection hole 5 is drilled in the foundation ground 2 by the required length.

Thereafter, in the same manner as in the first embodiment, a grouting material is injected into the foundation ground 2 to improve the ground.

FIGS. 3a and 3b show a third embodiment of the present invention, in which a hole 3 having a larger diameter than the injection hole 5 is bored in the embankment layer 1 in the same manner as in the first and second embodiments. As shown in FIG. 3a, a hollow tube 9 is inserted into the hole 3 before or after filling the cement craig grout 4. This hollow tube 9 is the injection hole 5
It has an inner diameter that is equal to or slightly larger than the diameter of. In this case, the cement craig grout 4 is used to prevent leakage of the injection material from the lower end of the hollow tube 9 in the later injection process and to position the hollow tube 9 reliably so that the later drilling process can be performed at an appropriate position. It is for the purpose of doing.

Next, as shown in FIG. 3b, once the cement craig grout 4 has hardened, an injection hole 5 is bored through the hollow pipe 9 into the foundation ground 2 by the required length.

Thereafter, in the same manner as in the first and second embodiments, the injection material is injected into the foundation ground 2 to improve the ground. After the injection work is completed, the hollow tube 9 is pulled out and removed.

As explained above, according to the ground improvement method of the present invention, the cement clay grout filled in the embankment serves as a cover lock, making it possible to inject the grouting material into the foundation ground with the necessary injection pressure, and The cement clay grout prevents the injected material from rising along the vicinity of the embankment, preventing it from flowing into the embankment, allowing reliable ground improvement of the foundation ground. Furthermore, since cement craig grout is self-hardening and has physical properties similar to those of embankment, it is not necessary to remove the cement craig grout after the pouring work is completed, making it an advantageous construction method in terms of cost.

[Brief explanation of the drawing]

Figures 1 a to d are vertical sectional views showing the construction process of the first embodiment of the ground improvement method of the present invention, and Figure 2 a
and b are vertical sectional views showing the construction process of the second embodiment of the ground improvement method of the present invention, and Figures 3a and b are vertical sectional views showing the construction process of the third embodiment of the ground improvement method of the present invention. be. 1... Embankment, 2... Foundation ground, 3... Large diameter hole, 4... Cement craig grout, 5... Injection hole, 6... Injection pipe, 7... Packer, 8... Bottomed inside Empty tube, 9...Hollow tube.

Claims (1)

[Claims] 1. In a method of improving the foundation ground by injecting a grouting material into the foundation ground below the embankment layer through an embankment layer on the foundation ground, a hole with a diameter larger than the injection hole is formed in the embankment layer at least in the embankment layer. A hole is drilled until it reaches the boundary between the ground and the foundation ground, and the large-diameter hole is filled with cement craig grout as a filler that has physical properties similar to those of an embankment layer and has self-hardening properties, and the cement craig grout hardens. After that, an injection hole of the required length is drilled into the foundation ground through the hardened cement craig grout, and the injection material is injected into the foundation ground through the injection hole to improve the foundation ground. Ground improvement method for foundation ground. 2 In the method of improving the foundation ground by injecting grouting material into the foundation ground below the embankment layer through the embankment layer, a hole with a larger diameter than the injection hole is placed in the embankment layer at least at the boundary between the embankment layer and the foundation ground. When filling a large diameter hole with cement craig grout, which is a filling material that has physical properties similar to those of an embankment layer and is self-hardening, the injection hole is Insert a hollow tube with a bottom that has an outer diameter equal to or slightly larger than the diameter of the cement craig grout, then pull out the hollow tube with a bottom after the cement craig grout has hardened; An injection hole of the required length is drilled into the foundation ground through the space formed in the cement craig grout hardened by the method, and the injection hole is used to improve the foundation ground by injecting the injection material into the foundation ground. A ground improvement method for foundation ground under embankments. 3. In the method of improving the foundation ground by injecting grouting material into the foundation ground below the embankment layer through the embankment layer, a hole with a diameter larger than the injection hole is placed in the embankment layer at least at the boundary between the embankment layer and the foundation ground. When filling a hole with a large diameter with cement craig grout, which is a filling material that has physical properties similar to those of an embankment layer and has self-hardening properties, the injection hole should be Insert a hollow pipe with an inner diameter equal to or slightly larger than the diameter, drill an injection hole into the foundation ground by the required length through the hollow pipe, and pour the injection material into the foundation ground through the injection hole. A ground improvement method for the foundation ground under an embankment, which is characterized by improving the foundation ground by injection.