JP2022064785A - Subgrade improving method - Google Patents

Abstract

To easily provide a novel method capable of improving a subgrade at low cost.MEANS FOR SOLVING THE PROBLEM: A method includes the step of: forming a first improved body by improving a hard layer by a double pipe, high-pressure injection agitation method encircling a solidification material slurry jet with compressed air, or improving the hard layer by a triple-pipe high-pressure injection agitation method having three flow passages which are a compressed air flow passage, a cutting fluid flow passage and a solidification material slurry flow passage, and encircling at least one of a cutting fluid jet and the solidification material slurry jet with compressed air; and forming a second improved body by improving a soft layer by a single-pipe high-pressure injection agitation method, wherein the first improved body and second improved body are arranged successively in a depth direction, the single-pipe high-pressure injection agitation method uses a double-pipe high-pressure injection agitation device or triple-pipe high-pressure injection agitation device, an injection monitor at the tip of a rod is replaced with a monitor of the single-pipe high-pressure injection agitation method to control improved diameters of the first improved body and second improved body.SELECTED DRAWING: None

Description

The present invention relates to a ground improvement method.

Conventionally, a ground improvement means capable of creating a ground improvement body having excellent uniformity in the improved diameter has been known. For example, in Patent Document 1, a ground improvement high-pressure injection stirring device having a rod provided with an upper injection nozzle and a lower injection nozzle arranged at intervals in the vertical direction at the tip portion, wherein the upper injection nozzle is used. A high-pressure injection stirring device for ground improvement is described, wherein the distance between the lower injection nozzle and the lower injection nozzle coincides with an integral multiple of one or more times the pulling step length of the rod.

Further, Patent Document 1 is a ground improvement method using the above-mentioned high-pressure injection stirring device for ground improvement, in which cutting fluid is injected from the upper injection nozzle and a solidifying material slurry is injected from the lower injection nozzle. A ground improvement method characterized by spraying is described.

In the ground improvement work, when the strength (for example, shear strength, N value, etc.) of the ground to be improved differs depending on the depth (degree of depth), the solidifying material slurry in the ground improvement means (for example, high-pressure injection stirring device). When each of the injection pressure (unit: MPa) and the injection amount per unit time (unit: liter / minute) is kept constant, for example, the ground area where the strength of the ground increases vertically upward. Then, the improved diameter of the ground becomes smaller as the injection nozzle rises, and conversely, in the ground region where the strength of the ground decreases vertically upward, the improved diameter of the ground becomes larger as the injection nozzle rises. As a result, there is a problem that the size of the improved diameter of the ground in the vertical direction (depth direction) is not constant (in other words, the improved diameter is not the design).

In view of such problems, Patent Document 2 describes in advance the product of the injection pressure of the solidifying material slurry injected from the ground improvement means and the injection amount per unit time at various strengths of the ground, and the ground improvement diameter. In the actual ground improvement work, the planned design improvement diameter will be obtained when the strength of the ground to be improved changes by using the relationship between the above product and the ground improvement diameter. If the value of the above product is changed and the solidifying material slurry is injected at the injection pressure corresponding to the changed product and the injection amount per unit time, the size of the improved diameter of the ground is adjusted to a desired value. Is disclosed.

Japanese Unexamined Patent Publication No. 2017-172279 Patent No. 6391876

However, the multiple pipe construction method has a problem that it is expensive and the mud waste treatment work is troublesome. Therefore, it has been required to improve the ground by an inexpensive and simple construction method.

The present invention is to provide a novel method capable of easily and inexpensively improving the ground.

In order to achieve the above object, the present invention
(1) A method for improving a ground having a hard layer and a soft layer having different strengths in the depth direction.
A step of improving the hard layer by a double-tube high-pressure injection stirring method in which a solidified material slurry jet is surrounded by compressed air to form a first improved body, and a step of forming the first improved body.
The soft layer is improved by a single-tube high-pressure injection stirring method to form a second improved body, and the like is included.
The first improved body and the second improved body are continuously arranged along the depth direction.
The single-tube high-pressure injection agitation method uses the double-tube high-pressure injection agitation device of the double-tube high-pressure injection agitation method, and the injection monitor at the tip of the rod is replaced with the monitor of the single-tube high-pressure injection agitation method.
The present invention relates to a ground improvement method, which comprises controlling the improved diameters of the first improved body and the second improved body.
(2) A method for improving a ground having a hard layer and a soft layer having different strengths in the depth direction.
The hard layer has three, a compressed air flow path, a cutting fluid flow path, and a solidifying material slurry flow path, and at least one of the cutting fluid jet and the solidifying material slurry jet is surrounded by compressed air for high-pressure injection of a triple tube. The step of improving by the stirring method to form the first improved body,
The soft layer is improved by a single-tube high-pressure injection stirring method to form a second improved body, and the like is included.
The first improved body and the second improved body are continuously arranged along the depth direction.
The single-tube high-pressure injection agitation method uses the triple-tube high-pressure injection agitation device of the triple-tube high-pressure injection agitation method, and the injection monitor at the tip of the rod is replaced with the monitor of the single-tube high-pressure injection agitation method.
The present invention relates to a ground improvement method, which comprises controlling the improved diameters of the first improved body and the second improved body.
(3) The ground improvement method according to (1) or (2), wherein the improved diameter of the first improved body and the improved diameter of the second improved body are substantially the same.

In addition, "substantially the same" in the present invention means that an error due to an apparatus or a construction method is included with respect to the exact same.

According to the present invention, since the single pipe construction method is used in addition to the double pipe construction method or the triple pipe construction method which is a multiple pipe construction method, the ground improvement can be performed at low cost and the mud drainage treatment work is reduced. To.

It is a soil log in the depth direction of the ground in an embodiment.

Generally, the improved diameter of the multi-tube high-pressure injection stirring method (hereinafter, sometimes referred to as "multiple-tube method") is about Φ: 1.2 to 5.0 m, and the single-tube high-pressure injection stirring method (hereinafter, "single-tube method"). The improved diameter of) is about Φ: 0.5 to 2.2 m. Therefore, in order to put the multiple pipe construction method and the single pipe construction method in the same process in the ground improvement plan, the improved diameter of the multiple pipe construction method and the improved diameter of the single pipe construction method are controlled to be the same in the first place. There is a need.

On the other hand, when comparing the improved diameter of the multiple pipe method and the improved diameter of the single pipe method, the multiple pipe method surrounds the solidified material slurry jet with compressed air compared to the single pipe method (double pipe method). (Case), or by surrounding at least one of the cutting fluid jet and the solidifying material slurry jet with compressed air (in the case of the triple pipe method), the ground cutting distance in the ground can be increased, so that the improved diameter Can be increased. Therefore, in the present embodiment, in the ground improvement plan, the multiple pipe construction method is used for hard ground and the single pipe construction method is used for soft ground so that the improvement diameters of both grounds are the same. ..

FIG. 1 is a soil log showing an example of the hardness of a stratum in the depth direction from the surface of the earth to the inside of the ground. In the present embodiment, the ground is configured in the order of the soft layers N1 and N2, the hard layer H1, the soft layer N3, and the hard layer H2 from the surface. The soft layer N1 is, for example, embankment, and the soft layer N2 is, for example, cohesive soil. The hard layer H1 is, for example, a sand layer, and the soft layer N3 is, for example, cohesive soil. Further, the hard layer H2 is a mixed layer (gravel layer) of sand and stone. In the present embodiment, the N values of the soft layers N1 to N3 are about 0, the N value of the hard layer H1 is 30, and the N value of the hard layer H2 is 50.

Such ground improvement can be performed as follows. First, a double-tube high-pressure injection agitator (hereinafter, may be referred to as "double-tube device") or a triple-tube high-pressure injection agitator (hereinafter, may be referred to as "triple-tube device") is used. The rod is penetrated into the ground shown in FIG. 1 and a hole is drilled up to the hard layer H2 while ensuring the wastewater discharge clearance. Here, air and the solidifying material slurry are injected at an ultrahigh pressure to form, for example, an improved body having an improved diameter of M1 (1.6 to 2.2 m as an example).

Next, the rod of the above device is pulled up to reach the lower end of the hard layer H1 and pulled up to the upper end of the hard layer H1 while injecting air and the solidifying material slurry at an ultrahigh pressure to form an improved body having the same improved diameter M1. do.

The relationship between the injection pressure of the solidifying material slurry of the double pipe device or the triple pipe device, the injection amount per unit time, and the improvement time and the improvement diameter of the hard layers H1 and H2 was derived by conducting a test in advance. Keep it.

Next, the double tube device or triple tube device is pulled out to the ground surface, the double tube monitor or triple tube monitor at the tip of the rod is replaced with the single tube monitor, and a pseudo single tube high pressure injection stirring device (hereinafter, "single tube device"). In some cases). Then, the rod of the device is penetrated into the ground shown in FIG. 1 and a hole is drilled to the lower end of the soft layer N3. Then, an ultra-high pressure slurry is injected to form an improved body having an improved diameter M1.

Next, the single tube device is pulled up to reach the lower end of the soft layer N2 and the lower end of N1 in order, and while injecting the ultra-high pressure slurry, the single tube device is pulled up to the upper end of these layers to form an improved body having an improved diameter M1. ..

The relationship between the injection pressure of the solidifying material slurry of the single tube device, the injection amount per unit time, and the improvement time and the improvement diameters of the soft layers N1, N2, and N3 is derived by conducting a test in advance.

By going through the above steps, an improved body having an improved diameter M1 can be formed on the ground shown in FIG. 1, and the ground can be improved.

When replacing the double-tube monitor or triple-tube monitor at the tip of the rod with a single-tube monitor, the air flow path at the joint between the newly installed single-tube monitor and the double-tube monitor or triple-tube monitor (of the triple-tube). In this case, the air flow path and cutting fluid flow path) are closed with a dedicated annular packing, etc., and only the solidifying material slurry flow path can be circulated, so that the double pipe monitor or triple pipe monitor can be used as a pseudo single pipe monitor. can do.

The rod of the double tube device consists of an inner tube and an outer tube, and generally, the solidifying material slurry flows through the inner tube and compressed air flows through the outer tube, but the reverse is also possible.

The rod of the triple pipe device consists of an inner pipe, a middle pipe, and an outer pipe. Generally, a solidifying material slurry flows through the inner pipe, compressed air flows through the middle pipe, and a cutting fluid flows through the outer pipe. ing. However, the solidifying material slurry may flow through the inner pipe, the cutting fluid may flow through the middle pipe, and compressed air may flow through the outer pipe. Alternatively, the cutting fluid may flow through the inner pipe, compressed air may flow through the inner pipe, and the solidifying material slurry may flow through the outer pipe.

As is clear from the above embodiment, it can be seen that the multiple pipe construction method is suitable when the N value of the hard layer is 30 or more, particularly 50 or more.

According to this embodiment, conventionally, a construction machine of two construction methods, a single pipe construction method and a multiple pipe construction method, was required, but it is possible to construct with the same device by switching the construction method from the multiple pipe construction method to the single pipe construction method. So it is economical.

Although some embodiments of the present invention have been described above, these embodiments are shown as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

For example, in the above embodiment, the improved diameters of the soft layers N1, N2, N3 and the hard layers H1 and H2 are substantially the same, but the improved diameters of the soft layer and the hard layer can be made different. Specifically, the improved diameter of the soft layer can be increased, the improved diameter of the hard layer can be reduced, and vice versa.

Further, it is also possible to increase the improved diameter of any layer of the soft layer and the hard layer, for example, the soft layers N1 and N2 and the hard layer H1, and decrease the improved diameter of the soft layer N3 and the hard layer H2.

Claims (3)

A method for improving a ground having a hard layer and a soft layer having different strengths in the depth direction.
A step of improving the hard layer by a double-tube high-pressure injection stirring method in which a solidified material slurry jet is surrounded by compressed air to form a first improved body, and a step of forming the first improved body.
The soft layer is improved by a single-tube high-pressure injection stirring method to form a second improved body, and the like is included.
The first improved body and the second improved body are continuously arranged along the depth direction.
The single-tube high-pressure injection agitation method uses the double-tube high-pressure injection agitation device of the double-tube high-pressure injection agitation method, and the injection monitor at the tip of the rod is replaced with the monitor of the single-tube high-pressure injection agitation method.
A method for improving the ground, which comprises controlling the improved diameters of the first improved body and the second improved body. A method for improving a ground having a hard layer and a soft layer having different strengths in the depth direction.
The hard layer has three, a compressed air flow path, a cutting fluid flow path, and a solidifying material slurry flow path, and at least one of the cutting fluid jet and the solidifying material slurry jet is surrounded by compressed air for high-pressure injection of a triple tube. The step of improving by the stirring method to form the first improved body,
The soft layer is improved by a single-tube high-pressure injection stirring method to form a second improved body, and the like is included.
The first improved body and the second improved body are continuously arranged along the depth direction.
The single-tube high-pressure injection agitation method uses the triple-tube high-pressure injection agitation device of the triple-tube high-pressure injection agitation method, and the injection monitor at the tip of the rod is replaced with the monitor of the single-tube high-pressure injection agitation method.
A method for improving the ground, which comprises controlling the improved diameters of the first improved body and the second improved body. The ground improvement method according to claim 1 or 2, wherein the improved diameter of the first improved body and the improved diameter of the second improved body are substantially the same.

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