Columnar soil improvement method

Abstract

To provide a columnar soil improvement method capable of simultaneously achieving the reduction of the amount of industrial waste and the construction of a columnar improvement body excellent in bearing capacity.SOLUTION: The columnar soil improvement method includes a drilling process S1 in which a stirring device 30 is rotated and pressed in to penetrate into the soil together with a spiral lid 40, a soil discharge process A1 in which the stirring device 30 is pulled up and excavated soil B is pushed up and discharged by the spiral lid 40 to form an enlarged excavation part S2, and a step of discharging a solidifying material C from the stirring device 30 while rotating and pressing the stirring device 30 downward from the enlarged excavation part A1 while leaving the spiral lid 40. And an improvement process S3 for agitating and mixing the solidifying material C with the excavated D1 B to form improved soil, and in the improvement process S3, a head-enlarged columnar improvement body D having a larger outside diameter of a head part than that of a body part is constructed in the ground by storing a volume increase of the improved soil D1 in the diameter-enlarged excavation part A1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a columnar ground improvement method, and more particularly to a columnar ground improvement method that can simultaneously reduce the amount of industrial waste generated and construct columnar improved bodies with excellent bearing capacity. [Background technology]

[0002] When the ground on which a house, commercial building, or other property lies is weak, ground improvement work is carried out to improve the ground and increase its strength by applying artificial treatment to the ground. One of the methods used in ground improvement work is the columnar ground improvement method, in which a rod with an agitator attached to the bottom end is rotated and pressed into the ground while a solidifying material (cement slurry) is discharged from the agitator, and the excavated soil and solidifying material are mixed and stirred to create a cylindrical improvement body, thereby increasing the allowable bearing capacity of soft ground. The columnar ground improvement method has several advantages over the pile method, including lower cost, lower vibration and noise, and ease of construction on small plots of land. Therefore, it is widely used as a ground improvement method for the sites of small and medium-sized structures. In the columnar ground improvement method, the volume of the improved soil increases by the amount of solidification material injected and the amount of soil loosened by mixing, due to the mixing of the excavated soil and solidification material. For this reason, the excavation is performed without mixing the solidification material, with the depth of the excavated soil being determined to be the depth of the foundation bottom level plus the increase in the volume of the solidification material and excavated soil. Patent documents 1 and 2 disclose a technique in which, after excavating an excavation section, a columnar improvement body is constructed below the excavation section without removing the excavated soil from the excavation section, and the excavated soil is then removed after construction. Patent Document 3 discloses a technique in which soil discharge blades are attached below the mixing blades of a columnar ground improvement device to discharge soil, and after the soil is discharged, the soil discharge blades are removed and a columnar improved body is constructed with the mixing device. Patent document 4 discloses a technology in which a spiral soil discharge cover is attached to the top of the excavation blade in a removable manner, and the cover is used to suppress the buildup of improved soil and to discharge the excavated soil and improved soil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-8454 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-28854 [Patent Document 3] Japanese Patent Application Publication No. 08-158357 [Patent Document 4] Patent No. 7442241 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional technology has the following problems. <1> In the technology of Patent Documents 1 and 2, which constructs columnar improved bodies without removing soil from the dry excavation, the increase in volume of the improved soil is calculated based on an estimate, and if the increase in volume is greater than expected, improved soil mixed with solidification material will be mixed in with the excavated soil in the dry excavation. In this case, it becomes necessary to treat the entire amount of soil removed from the dry excavation as industrial waste, which increases disposal costs. <2> The technology of Patent Document 3, in which soil discharge blades are attached below the mixing blades, requires the rod to be pulled up and the soil discharge blades to be removed for each process, making the work complicated and difficult to install. In addition, because the excavated soil in the excavation area is discharged in advance, the improved soil expands during mixing and piles up inside the excavation area, and the improved soil is not sufficiently consolidated, which may result in the columnar improved body not achieving the designed strength. <3> The technology of Patent Document 4, in which a spiral soil discharge cover is installed on top of the excavation wing, can reduce the mounding of improved soil with the soil discharge cover, but the improved soil above the pile head surface still needs to be disposed of as industrial waste, which incurs disposal costs. <4> Although both technologies can exert vertical bearing capacity through columnar improvement bodies, it is difficult to expect resistance to horizontal forces caused by earthquakes.

[0005] An object of the present invention is to provide a columnar ground improvement method that solves the problems of the prior art as described above. [Means for solving the problem]

[0006] The columnar ground improvement method of the present invention uses a columnar ground improvement device equipped with a guide erected in the ground, a drilling rod that moves up and down along the guide, a mixer attached to the lower end of the drilling rod, and a spiral lid attached to the drilling rod above the mixer, and comprises: a drilling process in which the mixer is rotated and pressed in to penetrate the ground together with the spiral lid; a soil removal process in which the mixer is pulled upward and the spiral lid is used to push up and discharge the excavated soil, thereby forming an enlarged-diameter excavation section with a larger diameter than the improved diameter of the mixer; and an improvement process in which the mixer is rotated and pressed in below the enlarged-diameter excavation section, leaving the spiral lid, while discharging the solidification material from the mixer, and mixing and stirring the solidification material with the excavated soil to form improved soil.The improvement process is characterized in that by accommodating the increased volume of improved soil within the enlarged-diameter excavation section, an enlarged-head-shaped columnar improved body is constructed in the ground.

[0007] The columnar ground improvement method of the present invention may include an improvement process that includes an upper kneading process in which the stirring device is repeatedly rotated up and down near the head of the columnar improvement body, and a lower kneading process in which the stirring device is repeatedly rotated up and down near the tip of the columnar improvement body.

[0008] The columnar ground improvement method of the present invention may include a scraping step in which the improvement process involves placing a spiral lid on the bottom of the enlarged excavation section and rotating the spiral lid in conjunction with a stirring device to scrape off the excavated soil from the bottom of the enlarged excavation section.

[0009] In the columnar ground improvement method of the present invention, the guide may be provided with a vibration stopper into which a drilling rod is inserted in the vertical direction, and the spiral lid may be fixed to the vibration stopper during the improvement process. [Effects of the Invention]

[0010] The columnar ground improvement method of the present invention has at least one of the following effects. <1> By storing the increased volume of improved soil due to the injection of solidification material within the expanded excavation section, the improved soil can be prevented from overflowing onto the ground surface, reducing the amount of industrial waste generated. <2> By storing the improved soil in the enlarged excavation section, it is possible to construct an enlarged-head columnar improved body that combines high vertical and horizontal bearing capacity, thereby achieving a high ground improvement effect relative to the improvement diameter. [Brief explanation of the drawings]

[0011] [Figure 1] Illustration of columnar ground improvement equipment [Figure 2] Spiral lid illustration [Figure 3] Flow diagram of columnar ground improvement method [Figure 4] Illustration of columnar ground improvement method [Figure 5] Illustration of columnar ground improvement method [Figure 6] Illustration of columnar ground improvement method [Figure 7] Flow diagram of Example 2 [Figure 8] Flow diagram of Example 3 DETAILED DESCRIPTION OF THE INVENTION

[0012] The columnar ground improvement method of the present invention will be described in detail below with reference to the drawings. For convenience of explanation, the structure of the columnar ground improvement device 1 will be described first, and then the columnar ground improvement method will be described. [Example]

[0013] <1> Pillar-shaped ground improvement device (Figure 1) The columnar ground improvement device 1 comprises a body, a long guide 10 that can be erected in front of the body, an auger motor 50 that can move up and down along the guide 10, a drilling rod 20 connected to the auger motor 50 at its upper end, a stirring device 30 attached to the lower end of the drilling rod 20, a spiral lid 40 attached to the drilling rod 20 above the stirring device 30, and a vibration stopper 60 provided at the bottom of the guide 10. The drilling rod 20 moves up and down in conjunction with the movement of the auger motor 50, and is rotated about its axis by the drive of the auger motor 50. The anti-vibration device 60 holds the drilling rod 20 therein and regulates the rocking motion of the drilling rod 20 as it moves up and down.

[0014] <1.1> Stirring device (Fig. 1) The mixing device 30 is a device that has both an excavation function and a mixing function for mixing the excavated soil B. In this example, the stirring device 30 comprises a pair of drilling blades 31 at the lower end, two pairs of stirring blades 32 in the middle, a discharge outlet 33 between the pair of drilling blades 31, and a co-rotation prevention blade 34 between the two pairs of stirring blades 32, and the drilling blades 31 and stirring blades 32 rotate coaxially with the drilling rod 20. However, the structure of the agitator 30 is not limited to the above, and for example, the agitator blades 32 may be a pair. Also, the anti-co-rotation blades 34 may not be provided. Other structures of the agitator 30 are well known and will not be described in detail here.

[0015] <1.2> Spiral lid (Fig. 2) The spiral lid 40 is a member that has both a soil discharge function for discharging the excavated soil B and improved soil D1 from inside the borehole A and a lid function for suppressing swelling due to stirring and mixing of the improved soil D1. The spiral lid 40 includes at least a main body tube 41 and a spiral blade 42 attached to the outside of the main body tube 41, and has a structure that allows it to be attached and detached to the stirring device 30. In this example, the number of spiral blades 42 is two, but it may also be one. The spiral lid 40 has a generally circular outer shape in plan view due to the spiral blades 42, and the outer diameter of the spiral lid 40 is larger than the improved diameter due to the agitator 30. In detail, for example, the maximum width of the spiral blades 42 is 800 mm, and the maximum width of the excavation blades 31 of the agitator 30 is 500 mm, so that the excavation blades 31 are hidden under the spiral blades 42 in plan view.

[0016] <1.2.1> Main body tube The main body tube 41 is a tube that is attached to the drill rod 20 . The main body tube 41 has at least a cylindrical tubular portion 41a, and in this example, further has an upper engagement portion 41b provided on the upper edge of the tubular portion 41a, a lower engagement portion 41c provided on the lower edge of the tubular portion 41a, and an earth removal hole 41d provided in the peripheral wall of the tubular portion 41a. The inner diameter of the cylindrical portion 41 a corresponds to the outer diameter of the drill rod 20 . The upper engagement portion 41b is a structure for connecting with the vibration prevention device 60. In this example, a convex structure that engages with a key groove 61 provided at the bottom of the vibration prevention device 60 is adopted as the upper engagement portion 41b. The lower engaging portion 41c is a structure for connecting with the agitator 30. In this example, a groove-like structure that engages with a protrusion provided on the upper part of the agitator 30 is adopted as the lower engaging portion 41c. The soil discharge hole 41d connects the inside and outside of the peripheral wall of the cylindrical portion 41a, and by discharging excavated soil B that has entered the gap between the drilling rod 20 and the cylindrical portion 41a to the outside through the soil discharge hole 41d, the edges of the drilling rod 20 and the cylindrical portion 41a are cut and the spiral lid 40 is prevented from rotating together.

[0017] <1.2.2> Spiral wing The spiral blade 42 is a blade-shaped body that is provided around the main body tube 41. The spiral blade 42 is attached to the outer periphery of the cylindrical portion 41a in a spiral shape along the longitudinal direction of the cylindrical portion 41a. The spiral blade 42 has a generally circular outer shape when the spiral lid 40 is viewed from above. In this example, the helical blade 42 includes a digging edge 42a provided at the lower end edge of the helical blade 42, and a plurality of tip bits 42b provided on the digging edge 42a. The excavation edge 42a is an edge for cutting the helical blade 42 into the ground, and extends radially from the outer circumferential surface of the cylindrical portion 41a. The tip bits 42b are bits for cutting hard materials when the excavation arm 42a cuts into the ground, and are arranged in parallel along the width direction of the excavation arm 42a.

[0018] <2> Columnar ground improvement method (Figure 3) The columnar ground improvement method of the present invention is a method for constructing an expanded-head-shaped columnar improved body D with high bearing capacity in the ground using a columnar ground improvement device 1. The columnar ground improvement method includes at least a drilling step S1, an earth removal step S2, and an improvement step S3. In detail, the method is carried out, for example, as follows.

[0019] <3> Construction preparation The columnar soil improvement device 1 is moved to the construction site, and the guide 10 is set up vertically. The upper part of the drilling rod 20 is hung from the auger motor 50, and the auger motor 50 is moved above the guide 10, thereby erecting the drilling rod 20 along the guide 10. The upper part of the drilling rod 20 is connected to the auger motor 50. The lower part of the drilling rod 20 is held in the anti-vibration bracket 60. Before attaching the stirring device 30 to the drilling rod 20, the screw lid 40 is temporarily fixed to the anti-vibration stopper 60. Specifically, the upper engaging portion 41b of the screw lid 40 is passed through the key groove 61 of the anti-vibration stopper 60 and rotated around the axis to engage the upper engaging portion 41b in the key groove 61 (FIG. 4). The agitator 30 is connected to the lower end of the drilling rod 20, and the screw lid 40 is removed from the anti-vibration stopper 60 by disengaging the upper engaging portion 41b from the key groove 61, and the screw lid 40 is placed on the agitator 30. At this time, the lower engaging portion 41c of the screw lid 40 is fitted into the convex portion of the agitator 30, and the screw lid 40 is connected to the agitator 30 so as to rotate synchronously with the agitator 30.

[0020] <4> Hole drilling process The hole drilling step S1 is a step of dry drilling the head of the borehole A. The hole drilling step S1 is performed, for example, as follows. The auger motor 50 of the columnar soil improvement device 1 is driven to rotate and press the agitator 30 at the lower end of the drilling rod 20 into the ground. As the agitator 30 is rotated and pressed in, the spiral lid 40 mounted on the agitator 30 rotates in synchronization with the agitator 30 via the lower engagement portion 41c, causing the excavation edge 42a of the spiral blade 42 to cut into the excavated soil B, and the spiral lid 40 penetrates into the excavated soil B together with the agitator 30 (Figure 5(1)). The agitator 30 and the spiral lid 40 penetrate to a depth where the spiral blades 42 of the spiral lid 40 reach the bottom of the excavation.

[0021] <5> Earth removal process The soil discharging step S2 is a step of forming an enlarged diameter excavation section A1 by discharging the excavated soil B from the borehole A. The soil discharging step S2 is performed, for example, as follows. The auger motor 50 of the columnar ground improvement device 1 is moved above the guide 10 without rotating, and the mixing device 30 is pulled up into the borehole A, thereby pulling the spiral lid 40 mounted on the mixing device 30 above the ground surface. This pushes up the excavated soil B above the spiral blade 42 at the penetration depth in the hole drilling step S1 and discharges it out of the excavated hole A, forming an enlarged excavated section A1 with a diameter larger than the improved diameter of the mixing device 30 (Figure 5(2)). Before the screw lid 40 is lifted, the screw lid 40 may be rotated together with the agitator 30 to scoop up the excavated soil B onto the screw lid 40.

[0022] <6> Improvement process The improvement step S3 is a step of constructing underground columnar improved bodies D. The improvement step S3 is carried out, for example, as follows. The screw cap 40 is pulled up to the ground, and the upper engaging portion 41b of the screw cap 40 is engaged with the key groove 61 of the anti-vibration stopper 60, thereby fixing the screw cap 40 to the anti-vibration stopper 60 (FIG. 5(3)). The agitator 30, separated from the spiral lid 40, is rotated and pressed downward from the enlarged excavation section A1, while the cement-based solidification material C is discharged from the discharge port 33 of the agitator 30 into the excavated soil B, stirring and mixing it. As a result, the excavated soil B is mixed with the solidification material C to produce improved soil D1, and the ground is improved into a cylindrical shape (Figure 6(4)). As the solidification material C is stirred and mixed, the volume of the improved soil D1 increases by the amount of solidification material C injected. In the present invention, an enlarged diameter excavation section A1 is provided at the top of the borehole A, so the improved soil D1 that rises upward from the borehole A is contained in the enlarged diameter excavation section A1 from the head of the borehole A (Figure 6 (5)). After improvement is complete, the mixing device 30 is pulled out of the borehole A, and the top of the improved soil D1 is plowed off to align it with the pile head surface of the designed columnar improved body D. Through the above steps, a columnar improved body D with an enlarged head shape, in which the outer diameter of the head is larger than the outer diameter of the body, is constructed underground using the cylindrically mixed improved soil D1 (Figure 6(6)).

[0023] <6.1> Function of the expansion drilling section The columnar ground improvement method of the present invention prevents the improved soil D1 from overflowing onto the ground surface by storing the increased volume of the improved soil D1 within the enlarged excavation section A1, thereby reducing the amount of industrial waste generated. In addition, since the diameter of the enlarged excavation section A1 is larger than the diameter of the improved soil by the mixing device 30, the rate at which the improved soil D1 rises due to the mixing and stirring of the solidification material C is significantly reduced within the enlarged excavation section A1. This makes it easier to manage the injection amount of the solidification material C, and prevents excessive injection.

[0024] <7> Improved columnar body One of the features of the columnar ground improvement method of the present invention is that an expanded-head columnar improvement body D is constructed underground. The expanded-head columnar improved body D can exert a higher vertical bearing capacity than a normal columnar improved body because the ground supports the bottom of the head. This allows it to exert sufficient bearing capacity with a smaller diameter and shorter design than a normal columnar improved body. In addition, because the contact area between the side of the head and the ground is large, it can utilize ground springs to exert high horizontal support force during earthquakes. As described above, it is possible to simultaneously reduce the amount of industrial waste generated and construct columnar improved structures with high bearing capacity. [Example]

[0025] [Example of re-kneading] In this embodiment, the improving step S3 includes an upper re-kneading step S31 and a lower re-kneading step S32 (FIG. 7). In detail, the steps are carried out, for example, as follows. After the agitator 30 is rotated and pressed downward from the enlarged excavation section A1, the injection of the solidification material C is stopped, and the agitator 30 is inverted near the enlarged excavation section A1 and moved up and down to knead the upper part (upper part kneading process S31). When the agitator 30 reaches the tip of the columnar improved body D, the injection of the solidification material C is stopped, and the agitator 30 is inverted near the tip and moved up and down to knead the lower part (lower part kneading process S32). Through the above steps, the head and tip of the improved columnar body D are sufficiently agitated, and the quality of the improved columnar body D can be further improved. [Example]

[0026] [Example of scraping excavated soil] In this embodiment, the improving step S3 includes a scraping step S33 (FIG. 8). In detail, the process is carried out, for example, as follows. After the soil unloading step S2, the spiral lid 40 is not fixed to the anti-vibration stopper 60 but is placed on the bottom surface of the enlarged diameter excavation section A1. After the ground has been improved into a cylindrical shape by the agitator 30, the agitator 30 is re-engaged with the spiral lid 40 of the enlarged diameter excavation section A1, and the spiral lid 40 is rotated in conjunction with the agitator 30 at the height of the bottom surface of the enlarged diameter excavation section A1. This allows the excavated soil B that falls and accumulates in the enlarged excavation section A1 after the soil discharge process S2 to be scraped off by the spiral blade 42 and mixed with the improved soil D1, thereby improving the quality of the head of the columnar improved body D. [Explanation of symbols]

[0027] 1 Columnar ground improvement device 10 Guide 20 drilling rods 30 Stirring device 31 Drilling Wing 32 Stirring blade 33 Discharge port 34 Anti-corotation wing 40 spiral lid 41 Main body tube 41a Cylindrical part 41b Upper engaging part 41c Lower engagement part 41d Earth removal hole 42 Spiral wing 42a Excavation area 42b Tip Bit 50 Auger motor 60 Anti-vibration 61 Key groove Borehole A A1 Expanded excavation section B Excavated soil C Solidifying material D Improved columnar body D1 Improved soil S1 Hole drilling process S2 Earth removal process S3 improvement process S31 Upper kneading process S32 Lower kneading process S33 Scraping process

Claims

1. A columnar ground improvement method using a columnar ground improvement device comprising: a guide erected on the ground; a drilling rod that moves up and down along the guide; a stirring device provided at the lower end of the drilling rod; and a spiral lid attached to the drilling rod above the stirring device, A drilling step of rotating and pressing the stirring device into the ground together with the spiral lid; A soil discharge process in which the mixing device is raised upward and the excavated soil is pushed up and discharged with the spiral lid to form an expanded excavation section having a diameter larger than the improved diameter of the mixing device; and an improvement process in which the agitator is rotated and pressed downward from the enlarged diameter excavation section, leaving the spiral lid, and the solidification material is discharged from the agitator, and the solidification material is mixed with the excavated soil to form improved soil. In the improvement process, the increased volume of the improved soil is accommodated in the enlarged excavation section, thereby constructing an enlarged-head columnar improved body in the ground, the outer diameter of which is larger than the outer diameter of the body. Column-shaped ground improvement method.

2. The improvement step an upper kneading step in which the agitator is repeatedly rotated up and down near the head of the columnar improved body; a lower kneading step in which the rotation of the stirring device is repeated up and down near the tip of the columnar improved body, The columnar ground improvement method according to claim 1.

3. The improvement step The method includes a scraping step in which the spiral lid is placed on the bottom surface of the enlarged diameter excavation section and rotated in conjunction with the stirring device to scrape off the excavated soil on the bottom surface of the enlarged diameter excavation section. The columnar ground improvement method according to claim 1.

4. The guide includes a stopper into which the drilling rod is inserted in the vertical direction, In the improvement step, the spiral lid is fixed to the anti-vibration device. The columnar ground improvement method according to claim 1 or 2.

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