JPH0387413A - Construction method for columnar consolidation body in ground improvement and its device - Google Patents

Abstract

PURPOSE:To improve a ground most excellently by discharging stabilizing agent while the ground is being excavated to form an improved columnar consolidation body, and thereby concurrently forming a reinforced columnar consolidation body around the outer circumferential section of the aforesaid body. CONSTITUTION:A ground improvement device 11 is provided, which is equipped with a rotary shaft 12 which is firmly formed with excavating blades 5 and 5 and stirring blades 6... in the vicinity of its tip end section, a feed passage for stabilizing agent and the like which is formed in the inside of the rotary shaft 12, and discharge opening 14, 14, 16 and 16 provided in the vicinity of its tip end section. By the use of the ground improvement device 11, stabilizing agent is discharged while the ground 8 is being excavated, and stabilizing agent is mixedly stirred with excavated soil so that an improved columnar consolidation body 24 is thereby formed at the center section of an excavation area. Furthermore, a reinforced columnar consolidation body 25 is concurrently formed around the circumferential section of the improved consolidation body 24 while stabilizing agent or other materials is being discharged in order to meet the purpose for ground improvement.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention discharges a stabilizing material while excavating the ground, mixes and stirs the stabilizing material and the excavated material in the ground, and forms a columnar material into the excavated area. The present invention relates to a method for constructing a columnar solid body in ground improvement by forming a solid body, and an apparatus therefor.

[Conventional technology]

Conventionally, as this type of construction method, a construction method using a ground improvement device 1 as shown in FIG. 9, for example, is known.

This device 1 is provided with a rotary shaft 3 that can rotate forward and backward at the lower part of the drive device main body 2, and a drilling bit 4 at the tip of the rotating shaft 3, and a drilling blade 5 located slightly above the drilling bit 4 for stirring. The blades 6 are attached to each of the blades 6, and a discharge hole 7 for stabilizing material is provided near the excavation blades 5 of the rotary shaft 3. When the rotary shaft 3 is operated to excavate the ground 8 with the excavation blades 5, a chemical stabilizer such as lime or cement is discharged from the discharge hole 7, and this and the excavated soil are mixed with the agitation blades 5. The soil is improved by mixing and stirring the excavated parts and forming a columnar solid body 9 at the excavated site.

(Problems to be Solved by the Invention) By the way, in the conventional ground improvement method described above, a stabilizer such as lime or cement is mixed with excavated soil and thoroughly stirred to form a uniformly homogeneous soil. Since the purpose was to form a solid body 9, there was a problem that it could not be handled appropriately depending on the conditions of the construction site, as illustrated below. In other words, if the surrounding ground contains erosive substances such as seawater or acidic water, deterioration due to erosion progresses from the surface of the solid body, so consolidation is necessary to increase the corrosion resistance of the solid body. The entire body had to be strengthened and made denser, which led to problems such as the addition of a large amount of stabilizer and the extra dimensions. In addition, in the case of ground containing underground water, there is a problem that the stabilizer gradually dissipates before the solidified body is sufficiently hardened, so that the ground improvement effect cannot be expected to be that great.

Therefore, the technical problem of the present invention is to make it possible to construct a solid body that is optimal for the ground, no matter how bad the conditions are.

(Means for Solving the Problems) In order to solve the above technical problems, the present invention firstly discharges a stabilizing material while excavating the ground, and mixes and stirs the stabilizing material and the excavated soil. A column-shaped improved solid body is formed in the center of the excavated portion, and the above-mentioned stabilizer or other material is discharged to the outer periphery of the improved solid body to form a column-shaped reinforced solid body at the outer periphery of the improved solid body. Second, a rotating shaft is provided at the lower part of the drive unit body, and excavating blades and stirring blades are installed near the tip of the rotating shaft. In the apparatus for constructing a columnar solid body, a supply passage for stabilizing material and other materials is provided in the inner shell of the rotating shaft, and the rotary shaft near the excavating blade and the tip of the excavating blade or stirring blade are provided. The present invention employs an apparatus for constructing a columnar solid body, which is characterized in that a discharge hole is provided near the supply passageway through a switching valve or connected to a plurality of supply passageways.

In the present invention, there are various methods of separately discharging the stabilizer and other materials into the center of the excavation part and the outer periphery thereof, but especially when using a construction device such as the one according to the second invention, The construction can be easily carried out by providing respective discharge holes in appropriate parts of the device and discharging the fluid.

In addition, the type of stabilizer or other material that is mixed with the excavated soil to form an improved compact at the center and the stabilizer or other material that is discharged to form a reinforced compact at the outer periphery is Of course, the material can be selected depending on the soil conditions and purpose of use, and both may be made of the same material. As the stabilizer, for example, a chemical stabilizer such as lime-based or cement-based stabilizer is used. In addition, the material to be discharged to the outer periphery is as follows:
In addition to the above-mentioned stabilizers, high-strength materials such as fiber-mixed cement mortar and polymer cement mortar, or rapid solidifying materials such as bituminous materials and water glass-based materials are used. Moreover, when these are actually used, it is preferable to use them in a liquid state.

[Effect]

According to the above-mentioned method, an improved solidified body is formed in the center of the excavated part by stirring the chemical stabilizer and the excavated soil to improve and solidify the soil. By discharging the material, a columnar reinforced solid body can be formed.

(Example) Examples of the present invention will be described in detail below based on the accompanying drawings.

FIG. 1 shows a rotating shaft 12 portion of a columnar solid body construction apparatus 11 according to the present invention. This rotary shaft 12 is attached to the lower part of the drive device main body 2 so as to be able to rotate forward and backward, and a drilling bit 4 is attached to the lower end thereof, and a drilling blade 5 and a stirring blade 6 are installed near the upper part of the drilling bit 4. It is permanently installed. The drilling bit 4 is formed of a tapered plate-shaped body, and rotates all at once when the rotating shaft 12 is driven to drill a hole in the ground. Further, both the excavating blade 5 and the stirring blade 6 are formed of rectangular plate-shaped bodies extending in the horizontal direction, and in particular, an uneven excavating blade 13 is formed at the lower end portion of the excavating blade 5.

The excavating blades 5 and stirring blades 6 are fixed to the rotating shaft 12 at the same angle of elevation in accordance with the rotation of the rotating shaft 12 in the forward direction. In addition, the stirring blade 6
are provided in multiple stages in the vertical direction of the rotating shaft 12, and are arranged at angles shifted by 90 degrees from each other.

On the other hand, in this embodiment, the first discharge hole 14 is provided in the rotary shaft 12 near the excavation blade 5, and the tip of the excavation R5 is led to a conduit 15 provided on the back side of the excavation blade 5. Second discharge holes 16 are provided, respectively, and these discharge holes 14 , 16 are connected to supply passages for stabilizing material or the like formed inside the rotary shaft 12 . This supply passage is connected to the rotating shaft 1 as shown in FIGS. 2 and 3.
There are two types: one in which only one is formed within the supply passage 17, and the other in which two are formed in the form of two trees. switching valve 18a, 1 for switching the discharge hole 14.16 of the
8b and 18c are provided. Further, as shown in FIG. 3, there are two supply passages 20a partitioned by a partition wall 19 provided at the center of the interior of the rotating shaft 12;
20b is used when discharging different types of stabilizer or stabilizer and other materials, and the lower part of one supply passage 20a is a first opening in the rotating shaft 12.
The lower part of the other supply passage 20b is connected to the conduit 15 leading to the second discharge hole 16.

Next, a construction method for improving the ground using the apparatus having the above configuration will be explained based on FIGS. 4 and 5.

First, as shown in FIG. 4, the rotary shaft 12 is rotated in the forward direction to drill a hole in the ground with the drilling bit 4, and the drilling blade 5 gradually excavates the hole. At the same time as this excavation, a chemical stabilizer such as lime or cement is discharged from the first discharge hole 14 provided in the rotating shaft 12, and the excavated soil and the stabilizer are sufficiently mixed by the stirring blade 6. By stirring, an improved solidified body 24 is formed at the excavated site. Next, after confirming that the excavation has been made to a predetermined depth, the excavator is pulled up at a constant speed while rotating the rotary shaft 12 in the opposite direction, as shown in FIG. At the same time, the first discharge hole 1
4 is stopped, and the stabilizer or other material is supplied from the second discharge hole 16 opened at the tip of the excavation blade 5.

In this case, if the rotary shaft 12 has one supply passage 17 as shown in FIG. 2, the switching valve 18a.

By switching all the supply passages 18b and 18c, the supply passage 17 and the second discharge hole 16 are connected, and as shown in FIG.
By stopping the supply of the stabilizer to the supply passage 20a connected to the first discharge hole 14 and feeding the stabilizer or other material into the other supply passage 20b, the stabilizer can be discharged from the second discharge hole 16. . In particular, the former is advantageous when dispensing the same stabilizer, and the latter is advantageous when dispensing different types of materials. In addition, since the material is discharged to the outer circumference from the second discharge hole 16 provided at the tip of the excavation blade 5 while pulling up the rotating shaft 12, the material discharged to the outer circumference and the soil are mechanically mixed. is not performed, and a cylindrical reinforced solid body 25 is formed in which the performance of the material is fully utilized.

Therefore, by means of the same stabilizer both the solid bodies 24.25
When forming solids, for example, by changing the concentration of both stabilizers and making the concentration higher in the outer periphery than in the center, a stronger solid can be formed in the outer periphery. It can provide resistance when improving sandy ground where groundwater is seawater.

It is also possible to improve the ground under the conditions described above using different types of materials; in this case, a stabilizing material such as lime or cement is discharged from the first discharge hole 14; While a normal columnar solid is formed in the center, polymer cement milk that is not degraded by seawater or the like and does not pass through is discharged from the second discharge hole 16, forming a dense columnar solid at the outer periphery. Effective ground improvement can be achieved by forming .

Furthermore, as shown in Figure 6, in ground improvement in areas sandwiched between upper and lower rivers, groundwater is in a flowing state as underground water, so forming solid bodies using conventional construction methods is not stable. Unable to prevent materials from dissipating. Therefore, in this embodiment, an improved consolidated body 24 similar to that described above is formed in the center of the excavated part, while a quick solidifying material such as a water glass material is discharged to the outer periphery to form a reinforced consolidated body in a short time. By forming the stabilizer 25a and protecting the surface of the improved solidified body 24 inside until it is sufficiently hardened, it is possible to prevent the stabilizer from dissipating due to the underground water 28.

Furthermore, as shown in Fig. 7, when improving the ground where the unconsolidated layer 29 is on the hard stratum 30, the conventional improvement method is to Since the solid body 9 and the surrounding unconsolidated layer 29 have good adhesion, friction acts on the solid body 9 as consolidation progresses,
Although there is a risk of the solid body 9 being destroyed due to excessive load, as shown on the right side of the figure, an improved solid body 24 similar to that described above is formed on the inside, and the outer periphery is reinforced with bituminous material. By forming the solid body 25b (insulating layer), it is possible to break off the adhesion with the unconsolidated layer 29, and it is possible to prevent the improved solid body 24 from being destroyed due to the above-mentioned friction.

Furthermore, as shown in FIG. 8, when improving the ground 8 by overlapping columnar solid bodies to form a self-supporting earth retaining wall 31, shear stress and bending are applied to the overlapped parts. Tensile stress will be concentrated. Therefore, in such a case, an improved solid body 24 similar to that described above is formed on the inside, while a reinforced solid body 25c using fiber-containing cement milk or cement mortar is formed on the outer periphery. By this, it is possible to form a columnar solid body that is resistant to shear stress and bending tensile stress.

〔effect〕

As explained above, according to the method for constructing a columnar solid body in ground improvement according to the present invention, a columnar improved solid body is formed in the center of an excavated part, and a columnar reinforced solid body is formed on the outer periphery of the columnar solid body. By forming a double structure, and by making it possible to select various properties of the solidified body, it is possible to carry out optimal improvements to the ground no matter how bad the ground conditions are.

Further, according to the construction device according to the present invention, two discharge holes are provided at the tip of the rotating shaft, and materials with different characteristics can be discharged from each discharge hole to the center and outer circumference of the excavated part. Therefore, a columnar solidified body having a double structure can be easily formed.

[Brief explanation of drawings]

FIG. 1 is a front perspective view showing one embodiment of the apparatus for constructing columnar solid bodies in ground improvement according to the present invention, and FIGS. 2 and 3 are cross-sectional views showing different embodiments of the internal structure of the rotating shaft. Fig. 4 is an explanatory diagram of excavation using this device, Fig. 5 is an explanatory diagram of when this device is pulled up, and Figs. 6 to 8 are examples of different construction methods according to the present invention. FIG. 9 is a front perspective view showing an example of a conventional columnar solid body construction apparatus. 1.11...Soil improvement device 2...Driving device main body 3.12...Rotating shaft 5...Drilling blade 6...Agitation blade 7.14.16...Discharge hole 8... Ground 9...Solid bodies 17.20a, 20b---Supply passages 18a, 18b, 18cm Switching valve 24...Improved solid bodies 25.25a, 25b, 25cm---Reinforced solid bodies FIG. ＋7－－－－－－－－翿Supply i11 bribe old a, 18b, 18cm-all #1 square 20a, 20b ------4P%klL outside diagram diagram ↑ Figure 7 diagram diagram

Claims (2)

[Claims] (1) While excavating the ground, a stabilizer is discharged, and the stabilizer and the excavated soil are mixed and stirred to form a columnar improved solid in the center of the excavated area, and the above-mentioned 1. A method for constructing a columnar solid body for ground improvement, characterized in that a stabilizer or other material is discharged to form a columnar reinforced solid body on the outer periphery of the improved solid body. (2) In a construction device for columnar solid bodies, which has a rotating shaft at the lower part of the driving device main body, and has excavating blades and stirring blades fixed near the tip of the rotating shaft, the inside of the rotating shaft is A rotating shaft near the excavation wing and a supply path for stabilizing and other materials are provided.
A construction apparatus for a columnar solid body, characterized in that discharge holes are provided near the tips of the excavating blades or stirring blades, each of which is connected to the supply passage by a switching valve, or which is connected to a plurality of supply passages. .