JP7621142B2 - Construction method of columnar improvement body with core material - Google Patents

Description

The present invention relates to a method for constructing a columnar improved structure with a core material.

A retaining wall in which a core material is embedded in a columnar improvement body (soil cement column) is known (see, for example, Patent Documents 1 and 2). Also, in reinforced concrete members, shear reinforcement bars arranged diagonally to the main bars are known (see, for example, Patent Documents 3 and 4).

In the technology disclosed in Patent Document 2, an H-shaped steel beam with a reinforcing bar cage attached as a core material is vibrated while being dropped into an unhardened columnar improvement body, and then the H-shaped steel beam alone is pulled up, embedding the reinforcing bar cage inside the columnar improvement body.

JP 2001-182055 A Japanese Patent Application Publication No. 3-191113 JP 2002-115369 A JP 2002-266473 A

In the technology disclosed in Patent Document 2, if the bar-shaped steel material such as reinforcing bars that make up the reinforcing bar cage becomes misaligned with respect to the column-shaped improvement body, the shear strength of the column-shaped improvement body may decrease.

Taking the above facts into consideration, the present invention aims to reduce the positional deviation of bar-shaped steel material relative to the columnar improvement body.

The construction method for a column-shaped improvement body with core material in the first embodiment includes a dropping process in which wall-shaped reinforcements, each made of a plurality of bar-shaped steel materials connected by shear reinforcement bars, are arranged on both sides of a web, and an H-shaped steel beam with the upper part of the bar-shaped steel material attached is dropped into the pre-hardened columnar improvement body while being vibrated, and a lifting process in which, with the upper part of the bar-shaped steel material removed from the H-shaped steel beam, the H-shaped steel beam is lifted up from the pre-hardened columnar improvement body.

According to the construction method for a column-shaped improvement body with core material of the first embodiment , in the dropping process, wall-shaped reinforcements made of multiple bar-shaped steel materials connected by shear reinforcement are arranged on both sides of the web, and the H-shaped steel with the upper part of the bar-shaped steel material attached is dropped into the pre-hardened columnar improvement body while being vibrated.

Next, in the lifting process, the upper part of the bar-shaped steel material is removed from the H-shaped steel, and the H-shaped steel is lifted up from the unhardened column-shaped improvement body. This leaves the wall-shaped reinforcement embedded (left behind) inside the column-shaped improvement body.

Here, in the present invention, by connecting multiple steel bars with shear reinforcement to form wall-shaped reinforcement, the shear strength of the column-shaped improved body can be ensured. In addition, by attaching the upper part of the steel bars to the H-shaped steel, the positional deviation of the multiple steel bars relative to the column-shaped improved body can be reduced.

In this way, the present invention can suppress the displacement of the bar-shaped steel material relative to the columnar improvement body while ensuring the shear strength of the columnar improvement body.

The construction method for a columnar improvement body with a core material of the second aspect is the construction method for a columnar improvement body with a core material of the first aspect , in which a pair of positioning portions facing each other are provided at the lower end of the H-shaped steel, and in the dropping process, the H-shaped steel is dropped into the columnar improvement body before hardening while being vibrated, with the bar-shaped steel materials of the wall-shaped reinforcement bars arranged on both sides of the web connected to each other by connecting bars inserted between the pair of positioning portions, and in the pulling process, the H-shaped steel is pulled up from the columnar improvement body before hardening, and the connecting bars are removed from between the pair of positioning portions.

According to the construction method of the columnar improved body with core material according to the second aspect , a pair of positioning parts facing each other is provided at the lower end of the H-shaped steel. Then, in the dropping step, the H-shaped steel is dropped into the pre-hardened columnar improved body while being vibrated, with the bar-shaped steel materials of the wall-shaped reinforcement bars arranged on both sides of the web of the H-shaped steel connected to each other by the connecting rebar inserted between the pair of positioning parts.

Next, in the lifting process, the H-shaped steel is lifted from the columnar improvement body before hardening, and the connecting rebar is removed from between the pair of positioning parts. This leaves a pair of bar-shaped steel materials embedded (left behind) inside the columnar improvement body.

In this way, in the present invention, by inserting the connecting rebar between a pair of positioning parts during the dropping process, the movement of the connecting rebar and the multiple steel bars connected by the connecting rebars is restricted. Therefore, the positional deviation of the steel bars relative to the columnar improvement body is further suppressed.

In addition, in the lifting process, the connecting rebars come out of the pair of positioning parts by lifting the H-shaped steel. Therefore, the H-shaped steel can be easily lifted from the columnar improvement body before it hardens.

The construction method for a column-shaped improvement body with a core material of the third aspect is the construction method for a column-shaped improvement body with a core material of the first or second aspect , in which, in the dropping step, the upper part of the bar-shaped steel material is attached to a bracket protruding from the H-shaped steel material, and the H-shaped steel is dropped into the column-shaped improvement body before hardening while being vibrated, and in the pulling step, the upper part of the bar-shaped steel material is detached from the bracket, and the H-shaped steel is pulled up from the column-shaped improvement body before hardening.

According to the construction method for a columnar improvement body with core material relating to the third aspect , in the dropping process, with the upper part of the bar-shaped steel material attached to a bracket protruding from the H-shaped steel, the H-shaped steel is dropped into the unhardened columnar improvement body while being vibrated.

Next, in the lifting process, the upper part of the bar-shaped steel material is removed from the bracket and the H-shaped steel is lifted up from the unhardened column-shaped improvement body.

By attaching the upper part of the bar-shaped steel material to the bracket protruding from the H-shaped steel in this way, the upper part of the bar-shaped steel material can be more firmly fixed to the H-shaped steel. Therefore, when the H-shaped steel material is vibrated during the dropping process, the vibration of the wall reinforcement is reduced, further reducing the positional deviation of the bar-shaped steel material relative to the column improvement body.

The columnar improvement body with core material of the fourth aspect comprises a columnar improvement body and a core material embedded in the columnar improvement body, and the core material has a first wall-shaped reinforcement having a plurality of steel bars and shear reinforcement connecting the plurality of steel bars, a second wall-shaped reinforcement having a plurality of steel bars and shear reinforcement connecting the plurality of steel bars, and facing the first wall-shaped reinforcement, and a connecting bar connecting a lower portion of the steel bars of the first wall-shaped reinforcement and a lower portion of the steel bars of the second wall-shaped reinforcement.

According to the fourth aspect , the columnar improvement body with a core material includes a columnar improvement body provided in the ground and a core material embedded in the columnar improvement body. The core material has a first wall-shaped reinforcement, a second wall-shaped reinforcement, and a connecting reinforcing bar.

The first wall-shaped reinforcement has multiple steel bars and shear reinforcement bars connecting the multiple steel bars. Similarly, the second wall-shaped reinforcement has multiple steel bars and shear reinforcement bars connecting the multiple steel bars, and faces the first wall-shaped reinforcement. The lower parts of the steel bars of the first wall-shaped reinforcement and the lower parts of the steel bars of the second wall-shaped reinforcement are connected by connecting bars.

Here, in the first wall reinforcement, multiple steel bars are connected by shear reinforcement. In the second wall reinforcement, multiple steel bars are connected by shear reinforcement. By embedding these first and second wall reinforcements in the columnar improvement body, the shear strength of the columnar improvement body can be ensured.

In addition, by connecting the lower part of the bar-shaped steel material of the first wall-shaped reinforcement and the lower part of the bar-shaped steel material of the second wall-shaped reinforcement with a connecting bar, it is possible to reduce the positional deviation of the bar-shaped steel material relative to the columnar improvement body when embedding the core material in the columnar improvement body.

In this way, the present invention can suppress the displacement of the bar-shaped steel material relative to the columnar improvement body while ensuring the shear strength of the columnar improvement body.

As described above, the present invention can reduce the positional deviation of the bar-shaped steel material relative to the columnar improvement body.

FIG. 2 is a vertical cross-sectional view showing a columnar improved body and a core material according to one embodiment. This is a cross-sectional view taken along line 2-2 of Figure 1. FIG. 2 is a perspective view of the core shown in FIG. 1 . FIG. 1 is an elevational cross-sectional view showing the construction process of a columnar improvement body according to one embodiment. This is a cross-sectional view taken along line 5-5 in Figure 4. FIG. 5 is a perspective view showing a lower portion of the H-shaped steel and the core material shown in FIG. 4 . FIG. 5 is a perspective view showing the H-shaped steel and the upper part of the core material shown in FIG. 4 . FIG. 1 is an elevational cross-sectional view showing the construction process of a columnar improvement body according to one embodiment. 6A and 6B are cross-sectional views corresponding to FIG. 5 and illustrating a modified example of a core material according to an embodiment. FIG. 13 is an elevation view illustrating the loading method in the loading experiment. 13A to 13C are an elevation view and a cross-sectional view showing the experimental model used in the loading experiment. 13 is a graph showing the experimental results of a loading experiment.

Below, one embodiment will be described with reference to the drawings.

(Columnar improvement body with core material)
The improved columnar body with a core material according to the present embodiment is shown in Fig. 1. The improved columnar body with a core material has a columnar improved body 10 and a core material 12 embedded in the columnar improved body 10.

(Columnar improvement body)
The columnar improvement body (columnar soil improvement body) 10 is connected, for example, in a wall-like manner in the ground G to form a retaining wall (not shown). The columnar improvement body 10 is formed, for example, from hardened soil cement.

Specifically, the columnar improvement body 10 is constructed by excavating the ground G with an excavation auger, injecting a cement-based hardening material such as cement milk into the ground G from the tip of the excavation auger, and then hardening the soil cement formed by stirring and mixing the excavated soil and the cement-based hardening material underground.

In addition, an underground space or underground structure (not shown) is formed on the side opposite to the side on which earth pressure acts on the columnar improvement body 10. Also, arrow P, appropriately shown in each figure, indicates the direction in which earth pressure acts on the columnar improvement body 10 (the thickness direction of the columnar improvement body 10 (retaining wall)), and arrow W indicates the width direction of the columnar improvement body 10 (retaining wall). Also, the direction in which earth pressure acts intersects (approximately perpendicular in this embodiment) with the width direction of the columnar improvement body 10 in a plan view.

(Core material)
A core material (core material for columnar improvement body) 12 is embedded inside the columnar improvement body 10. The core material 12 is dropped into the columnar improvement body 10 (soil cement) before hardening together with an H-shaped steel 30 (see FIG. 4 ) described later.

As shown in Figures 2 and 3, the core material 12 has a pair of wall-like reinforcements 20. The pair of wall-like reinforcements 20 are arranged along the direction of earth pressure (arrow P direction) in a plan view. The pair of wall-like reinforcements 20 are arranged opposite each other in the width direction of the columnar improvement body 10 (see Figure 2). The pair of wall-like reinforcements 20 are an example of a first wall-like reinforcement and a second wall-like reinforcement.

As shown in FIG. 3, each wall reinforcement 20 has a pair of steel bars 22 and a corrugated shear reinforcement 24 that connects the pair of steel bars 22. Each of the pair of steel bars 22 is formed of a straight reinforcing bar. The pair of steel bars 22 extend vertically along the columnar improvement body 10 and are spaced apart in the direction in which earth pressure acts. The pair of steel bars 22 are connected by the corrugated shear reinforcement 24.

The wavy shear reinforcement 24 is formed by bending a straight reinforcing bar into a wave shape with alternating peaks facing in opposite directions. This wavy shear reinforcement 24 is arranged along the columnar improvement body 10 and across a pair of steel bars 22. The peaks 24T of the peaks of the wavy shear reinforcement 24 are joined to the pair of steel bars 22 by welding or the like. The pair of steel bars 22 are connected by this wavy shear reinforcement 24.

In this embodiment, the phases of the wavy shear reinforcement 24 are opposite between one wall reinforcement 20 and the other wall reinforcement 20, but the phases of the wavy shear reinforcement 24 may be the same, for example. Also, the wavy shear reinforcement 24 is an example of a shear reinforcement.

The lower portion of a pair of steel bars 22 in one wall reinforcement 20 and the lower portion of a pair of steel bars 22 in the other wall reinforcement 20 are connected by a pair of connecting bars 26. Specifically, the pair of steel bars 22 in one wall reinforcement 20 and the pair of steel bars 22 in the other wall reinforcement 20 face each other in the width direction (arrow W direction) of the columnar improvement body 10.

Each of the pair of connecting rebars 26 is formed by a U-shaped rebar with an open upper side. The pair of connecting rebars 26 are arranged facing each other in the direction in which earth pressure acts. Each connecting rebar 26 is arranged across the lower part of the bar-shaped steel materials 22 that face each other in the width direction of the columnar improvement body 10, and is joined to the lower part of these bar-shaped steel materials 22 by welding or the like. The connecting rebars 26 connect the lower part of the pair of bar-shaped steel materials 22 in one wall-shaped reinforcement 20 to the lower part of the pair of bar-shaped steel materials 22 in the other wall-shaped reinforcement 20.

(Construction method of columnar improvement body with core material)
Next, an example of a method for constructing a columnar improvement body with a core material will be described.

As shown in FIG. 4, in this embodiment, the core material 12 is attached to the H-shaped steel 30, and while vibrating the upper end of the H-shaped steel 30 with a vibrator 80 such as a vibrator hammer, the H-shaped steel 30 and the core material 12 are dropped into the interior of the columnar improvement body 10 (soil cement) before hardening. Therefore, the mounting structure of the core material 12 to the H-shaped steel 30 will first be described.

(Attachment structure of core material to H-shaped steel)
5, the H-shaped steel 30 has a pair of flanges 32 facing each other in the direction in which earth pressure acts, and a web 34 connecting the pair of flanges 32. This H-shaped steel 30 is dropped into the interior of the unhardened columnar improvement body 10 with its longitudinal direction set to the up-down direction and with the opposing direction of the flanges 32 set to the direction in which earth pressure acts.

A pair of wall-shaped reinforcements 20 are arranged on both sides of the web 34 of the H-shaped steel (temporary H-shaped steel) 30. As shown in FIG. 6, the pair of wall-shaped reinforcements 20 are arranged to fit between the flanges 32 of the H-shaped steel 30. A pair of slits 40 into which a pair of connecting rebars 26 are respectively inserted are formed at the lower end of the web 34 of this H-shaped steel 30. The pair of slits 40 are arranged with a gap between them in the opposing direction of the flanges 32 (the direction of the arrow P).

Each slit 40 extends upward from the lower end of the web 34 and penetrates the web 34 in the thickness direction (arrow W direction). Each slit 40 has a pair of inner wall surfaces 40A that face each other in the opposing direction of the flanges 32. The connecting rebar 26 is inserted into this slit 40. This restricts the movement of the connecting rebar 26 in the opposing direction of the flanges 32 by the pair of inner wall surfaces 40A of the slit 40. The pair of inner wall surfaces 40A is an example of a pair of positioning portions.

As shown in FIG. 7, a pair of brackets 50 are provided on both sides of the web 34 of the H-shaped steel 30, to which the upper parts of the pair of bar-shaped steel materials 22 are attached. The pair of brackets 50 are formed by L-shaped angles in a plan view. The pair of brackets 50 are spaced apart in the opposing direction of the flanges 32.

Each of the pair of brackets 50 has a base portion 52 that is joined by welding or the like while overlapping the surface of the web 34, and a protrusion portion 54 that protrudes from one end of the base portion 52 in a direction outside the surface of the web 34. The protrusion portion 54 is formed in a wall shape that faces the flange 32. A mounting reinforcing bar 60 is joined to the surface of the protrusion portion 54 by welding or the like.

The mounting rebars 60 are formed of straight rebars and are arranged in the vertical direction. The lower ends of the mounting rebars 60 extend downward from the protruding parts 54 of the pair of brackets 50. The upper ends of a pair of bar-shaped steel materials 22 in the wall reinforcement 20 are detachably connected to the lower ends of the mounting rebars 60 via screw-type mechanical joints 62. As a result, the upper parts of the bar-shaped steel materials 22 are fixed to the upper part of the H-shaped steel 30 via the mounting rebars 60 and the brackets 50.

(Positioning Method)
Next, a method for positioning the core material 12 with respect to the columnar improved body 10 will be described.

Figure 4 shows the columnar improvement body 10 (soil cement) formed in the ground G before hardening. A stand 70 is provided around the columnar improvement body 10 in the ground G. The stand 70 has a pair of guide beams 72 that position the H-shaped steel 30 in the width direction of the columnar improvement body 10 relative to the columnar improvement body 10, and a pair of guide pieces 74 that position the H-shaped steel 30 in the direction of earth pressure relative to the columnar improvement body 10.

The pair of guide beams 72 are formed, for example, from H-shaped steel. The pair of guide beams 72 are spaced apart in the width direction of the columnar improvement body 10 and are arranged parallel to each other. By inserting the H-shaped steel 30 with the core material 12 attached between the pair of guide beams 72, the H-shaped steel 30 is positioned relative to the columnar improvement body 10 in the width direction of the columnar improvement body 10.

The pair of guide pieces 74 are formed, for example, from angles, and are installed on the upper surfaces of the pair of guide beams 72. The pair of guide pieces 74 are spaced apart in the direction in which earth pressure acts (the direction of arrow P) and are arranged parallel to each other. By inserting the H-shaped steel 30 with the core material 12 attached between the pair of guide pieces 74, the H-shaped steel 30 is positioned relative to the columnar improvement body 10 in the direction in which earth pressure acts.

(Dropping process)
Next, the dropping process will be described. In the dropping process, as described above, in a state where the H-shaped steel 30 is positioned relative to the columnar improvement body 10, a vibrator 80 such as a vibrator hammer attached to the upper end of the H-shaped steel 30 is operated, and the H-shaped steel 30 is vibrated in the vertical direction by the vibrator 80. As a result, the H-shaped steel 30 and the core material 12 are dropped (driven) into the interior of the columnar improvement body 10 before hardening while being guided by a pair of guide beams 72 and a pair of guide pieces 74.

Next, when the lower ends of the H-shaped steel 30 and the core material 12 reach a predetermined depth, the vibrator 80 is stopped. Note that each of the bar-shaped steel materials 22 of the pair of wall-shaped reinforcements 20 is not buried inside the columnar improvement body 10, but is left exposed above ground.

(Pulling up process)
Next, the pulling-up process will be described. As shown in Fig. 8, in the pulling-up process, first, the screw-type mechanical joint 62 is operated to release the connection between the mounting reinforcing bars 60 and the steel bars 22, and the upper portions of the steel bars 22 are removed from the H-shaped steel 30. This releases the pair of wall-shaped reinforcements 20 from the H-shaped steel 30.

Next, the vibrator 80 is operated to vibrate the upper end of the H-shaped steel 30 while lifting it up. At this time, the connecting rebars 26 come out of a pair of slits 40 formed at the lower end of the web 34 of the H-shaped steel 30. As a result, only the H-shaped steel 30 is removed from the column improvement body 10, and the core material 12 is embedded inside the column improvement body 10.

(effect)
Next, the effects of this embodiment will be described.

According to the construction method of the columnar improvement body with core material according to this embodiment, as shown in FIG. 4, in the dropping process, the wall-shaped reinforcement bars 20 are arranged on both sides of the web 34, and the H-shaped steel 30 to which the upper part of each bar-shaped steel material 22 of the wall-shaped reinforcement bars 20 is attached is dropped into the columnar improvement body 10 before hardening while being vibrated.

Next, as shown in FIG. 8, in the lifting process, the upper parts of each bar-shaped steel material 22 of the wall-shaped reinforcement 20 are removed from the H-shaped steel 30, and the H-shaped steel 30 is lifted from the columnar improvement body 10 before hardening. This leaves a pair of wall-shaped reinforcement bars 20 embedded (left behind) inside the columnar improvement body 10. By reinforcing the columnar improvement body 10 with this pair of wall-shaped reinforcement bars 20, damage to the columnar improvement body 10 due to earth pressure is suppressed.

In addition, by connecting a pair of steel bars 22 with corrugated shear reinforcement bars 24 to form wall reinforcement bars 20, the shear strength of the column improvement body 10 can be ensured. In addition, in this embodiment, the steel cost can be reduced compared to when steel members such as H-shaped steel are used as the core material of the column improvement body 10.

Furthermore, by attaching the upper part of each steel bar 22 of the wall-shaped reinforcement 20 to the H-shaped steel 30, when the H-shaped steel 30 is vibrated during the dropping process, the vibration of the H-shaped steel 30 and the pair of wall-shaped reinforcement 20 attached to the H-shaped steel 30 is reduced, thereby reducing the positional deviation of each steel bar 22 relative to the columnar improvement body 10.

In this way, in this embodiment, it is possible to suppress the positional deviation of each bar-shaped steel material 22 relative to the columnar improvement body 10 while ensuring the shear strength of the columnar improvement body 10.

Also, as shown in FIG. 6, the lower part of the steel bar 22 in one wall reinforcement 20 and the lower part of the steel bar 22 in the other wall reinforcement 20 are connected by a connecting bar 26. This further reduces the positional deviation of each steel bar 22 relative to the columnar improvement body 10 during the dropping process.

In addition, in the dropping process, the connecting rebar 26 is inserted into the slit 40 formed at the lower end of the web 34 of the H-shaped steel 30, and the H-shaped steel 30 is dropped into the unhardened columnar improvement body 10 while being vibrated.

As a result, the pair of inner wall surfaces 40A of the slit 40 restricts the movement of the connecting reinforcing bars 26 in the opposing direction of the flange 32. Therefore, the positional deviation of the lower part of each bar-shaped steel material 22 relative to the columnar improvement body 10 is reduced.

Furthermore, as shown in FIG. 7, in the dropping process, the upper part of the bar-shaped steel material 22 is attached to the mounting reinforcing bar 60 fixed to the bracket 50 protruding from the web 34 of the H-shaped steel 30, and the H-shaped steel 30 is dropped into the unhardened columnar improvement body 10 while being vibrated.

By attaching the upper part of the bar-shaped steel material 22 to the bracket 50 protruding from the web 34 of the H-shaped steel 30 in this way, the upper part of the bar-shaped steel material 22 can be more firmly fixed to the H-shaped steel 30. Therefore, when the H-shaped steel 30 is vibrated during the dropping process, the vibration of the wall reinforcement 20 is further reduced, and the positional deviation of the bar-shaped steel material 22 relative to the column improvement body 10 is further reduced.

The upper end of the bar-shaped steel material 22 is detachably connected to the lower end of the mounting rebar 60 via a screw-type mechanical joint 62. Therefore, during the lifting process, the upper part of the bar-shaped steel material 22 can be easily removed from the mounting rebar 60.

Furthermore, as shown in FIG. 5, the pair of wall-shaped reinforcements 20 are arranged to fit between the flanges 32 of the H-shaped steel 30. As a result, even if the vibration (amplitude) of the bar-shaped steel material 22 becomes large, the bar-shaped steel material 22 comes into contact with the web 34 or flange 32 of the H-shaped steel 30, limiting the vibration of the bar-shaped steel material 22.

Also, as shown in FIG. 6, in the pulling-up process, the H-shaped steel 30 can be pulled up from the columnar improvement body before hardening, so that the connecting steel bar 26 can be easily removed from the slit 40. Therefore, the H-shaped steel 30 can be easily pulled up from the columnar improvement body 10.

As shown in FIG. 3, in this embodiment, a pair of steel bars 22 are connected by a single corrugated shear reinforcement 24. Here, for example, when a pair of steel bars 22 are connected in a ladder shape by multiple linear shear reinforcement bars, it is necessary to position the multiple linear shear reinforcement bars with respect to the pair of steel bars 22 at a predetermined interval, which makes the positioning of the shear reinforcement bars time-consuming.

In contrast, in this embodiment, one corrugated shear reinforcement bar 24 is positioned relative to a pair of steel bars 22, so the corrugated shear reinforcement bar 24 can be easily positioned relative to the pair of steel bars 22. In addition, by welding the tops 24T of the corrugated shear reinforcement bar 24 to the pair of steel bars 22, the corrugated shear reinforcement bar 24 can be easily attached to the pair of steel bars 22.

(Modification)
Next, a modification of the above embodiment will be described.

In the above embodiment, two steel bars 22 are connected by a corrugated shear reinforcement 24. However, the number of steel bars 22 is not limited to two, and three or more steel bars 22 may be connected by a corrugated shear reinforcement 24. For example, in the modified example shown in FIG. 9(A), three steel bars 22 arranged in the direction in which earth pressure acts (direction of arrow P) are connected by a corrugated shear reinforcement 24.

In the above embodiment, the pair of wall-shaped reinforcements 20 are arranged so as to fit between the flanges 32 of the H-shaped steel 30. However, for example, as in the modified example shown in FIG. 9(B), the pair of wall-shaped reinforcements 20 may be arranged outside the flanges 32 of the H-shaped steel 30. In this case, for example, the protruding portion 54 of the bracket 50 protrudes outward beyond the flanges 32 of the H-shaped steel 30, and the mounting reinforcing bar 60 is fixed to the tip side of the protruding portion 54.

In the above embodiment, in the dropping process, the bar-shaped steel material 22 is detachably connected to the mounting rebar 60 via a screw-type mechanical joint 62. However, for example, in the dropping process, the mechanical joint 62 may be filled with a filler such as grout, and the bar-shaped steel material 22 may be non-detachably connected to the mounting rebar 60. In this case, in the pulling process, for example, the upper part of the bar-shaped steel material 22 is removed from the H-shaped steel 30 by cutting the mounting rebar 60 or the bar-shaped steel material 22.

For example, in the dropping process, the upper part of the bar-shaped steel material 22 may be directly fixed to the protruding portion 54 of the bracket 50 by welding or the like, and in the pulling process, the upper part of the bar-shaped steel material 22 may be removed from the H-shaped steel material 30 by cutting the bar-shaped steel material 22.

The bracket 50 is not limited to an angle, but may be, for example, a C-shaped steel or a T-shaped steel. The bracket 50 is not limited to being fixed to the web 34 of the H-shaped steel 30, but may also be fixed to the flange 32.

In addition, in the above embodiment, a pair of steel bars 22 are connected by corrugated shear reinforcement bars 24. However, a pair of steel bars 22 may be connected in a ladder shape by multiple linear shear reinforcement bars.

In addition, in the above embodiment, the bar-shaped steel material 22 is a straight reinforcing bar. However, the bar-shaped steel material may be a flat bar, an angle bar, etc.

In the above embodiment, the slits 40 are formed in the lower end of the web 34 of the H-shaped steel 30 as a pair of positioning portions. However, the pair of positioning portions is not limited to the slits 40, and may be, for example, a pair of angles attached to the lower end of the H-shaped steel 30 and facing each other in the opposing direction of the flanges 32. In this case, the connecting rebar 26 is placed between the pair of angles. In addition, the connecting rebar 26 is not limited to a U-shaped rebar, and may be, for example, a C-shaped rebar or a straight rebar.

The pair of slits 40 may be provided as needed and may be omitted as appropriate. Similarly, the pair of connecting rebars 26 may be provided as needed and may be omitted as appropriate.

(Loading experiment)
Next, the loading experiment of the columnar improved body will be explained.

In this loading experiment, a loading experiment was conducted on an experimental model of a columnar improvement body 10 in which a core material 12 was embedded in order to confirm the shear reinforcement effect of the corrugated shear reinforcement bar 24.

(Experiment overview)
As shown in Fig. 10, in this loading experiment, both ends of the experimental model in the longitudinal direction were pin-supported from below with support points S, and a vertical load N as earth pressure was applied to the center of the experimental model in the longitudinal direction, and the displacement (deflection) of the center of each experimental model was measured. Note that Fig. 10 shows an experimental model M2, which will be described later.

(Experimental model)
11(A) to 11(C) show experimental models M1 to M3. In each of the experimental models M1 to M3, a plurality of steel bars 92 are embedded inside a rectangular columnar improved body 90 formed from soil cement. Both ends of the plurality of steel bars 92 are tied together with positioning ties 100. These ties 100 are placed outside the support points S so as not to affect the shear strength of each of the experimental models M1 to M3.

In the experimental model M1 shown in FIG. 11(A), no shear reinforcement is provided. In the experimental model M2 shown in FIG. 11(B), a pair of steel bars 92 facing each other in the vertical direction (the direction in which earth pressure acts) are connected by corrugated shear reinforcement bars 94. In the experimental model M3 shown in FIG. 11(C), multiple steel bars 92 are surrounded by band-shaped shear reinforcement bars (hoop reinforcement bars) 96.

(Experimental Results)
The experimental results of the experimental models M1 to M3 are shown in Fig. 12. Note that the vertical axis of the graph shown in Fig. 12 indicates the vertical load N applied to the center of each of the experimental models M1 to M3, and the horizontal axis indicates the deformation amount of the center of each of the experimental models M1 to M3.

As can be seen from Figure 12, experimental model M1, which does not have shear reinforcement, suffered early shear failure. In contrast, experimental model M2, which has wavy shear reinforcement 94, and experimental model M3, which has strip-shaped shear reinforcement 96, prevented early shear failure. This confirmed the shear reinforcement effect of wavy shear reinforcement 94 and strip-shaped shear reinforcement 96.

The shear strength of the experimental model M2, which was equipped with wavy shear reinforcement 94, was slightly smaller than that of the experimental model M3, which was equipped with strip-shaped shear reinforcement 96, but was comparable to the shear strength of the experimental model M3. This confirmed the usefulness of the wavy shear reinforcement 94.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and one embodiment and various modified examples may be used in appropriate combination, and the present invention may of course be embodied in various forms without departing from the spirit of the present invention.

10 Columnar improvement body 12 Core material 20 Wall-shaped reinforcement (first wall-shaped reinforcement, second wall-shaped reinforcement)
22 Steel rod 24 Wave-shaped shear reinforcement (shear reinforcement)
26 Connection steel bar 30 H-shaped steel 40 Slit 40A Inner wall surface (positioning portion)

Claims (3)

a dropping process in which wall-shaped reinforcements each made of a plurality of steel bars connected by shear reinforcement bars are arranged on both sides of the web, and the H-shaped steel to which the upper portions of the steel bars are attached is dropped into the pre-hardened columnar improved body while being vibrated;
A lifting process of lifting the H-shaped steel from the columnar improvement body before hardening in a state where the upper part of the bar-shaped steel material is removed from the H-shaped steel;
A construction method for a columnar improvement body with a core material. A pair of positioning portions facing each other are provided at the lower end of the H-shaped steel,
In the dropping step, the bar-shaped steel materials of the wall-shaped reinforcement bars arranged on both sides of the web are connected to each other by a connecting rebar inserted between a pair of the positioning portions, and the H-shaped steel is dropped into the columnar improvement body before hardening while vibrating the H-shaped steel,
In the lifting process, the H-shaped steel is lifted up from the columnar improvement body before hardening, and the connecting reinforcing bar is removed from between the pair of positioning portions.
A method for constructing the columnar improvement body with core material as described in claim 1. In the dropping step, the upper part of the bar-shaped steel material is attached to a bracket protruding from the H-shaped steel, and the H-shaped steel is dropped into the columnar improvement body before hardening while being vibrated,
In the lifting step, the H-shaped steel is lifted up from the columnar improvement body before hardening in a state where the upper part of the bar-shaped steel material is removed from the bracket.
A method for constructing a columnar improved structure with a core material according to claim 1 or 2.