Construction method of columnar improvement body with core material

Abstract

To reduce positional deviation of rod-like steel materials against a columnar improvement body.SOLUTION: A construction method of a columnar improvement body with core material includes a drop-in process in which wall-shaped bars 20 each having multiple bar-shaped steel members 22 connected by wavy shear reinforcing bars 24 are arranged on both sides of a web 34, and H-shaped steel 30 to which the upper parts of the bar-shaped steel members 22 are attached is dropped into a columnar improvement body 10 before hardening while being vibrated, and a lifting process of lifting the H-shaped steel 30 from the unhardened columnar improvement body 10 in a state in which the upper parts of the bar-shaped steel members 22 are removed from the H-shaped steel 30.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for constructing a columnar improvement structure with a core material. By law Regarding. [Background technology]

[0002] 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).

[0003] 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 and dropped into an unhardened columnar improvement body, and then the H-shaped steel beam alone is pulled up, thereby embedding the reinforcing bar cage inside the columnar improvement body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-182055 A [Patent Document 2] Japanese Patent Application Publication No. 3-191113 [Patent Document 3] JP 2002-115369 A [Patent Document 4] JP 2002-266473 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology disclosed in Patent Document 2, if the bar-shaped steel material such as the reinforcing bars that make up the reinforcing bar cage becomes misaligned with respect to the column-shaped improved body, the shear strength of the column-shaped improved body may decrease.

[0006] In consideration of the above, an object of the present invention is to reduce the positional deviation of a bar-shaped steel material relative to a columnar improvement body. [Means for solving the problem]

[0007] According to the first aspect The construction method of a column-shaped improvement body with a core material 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 column-shaped improvement body before hardening while being vibrated, and a lifting process in which the H-shaped steel beam is lifted from the column-shaped improvement body before hardening with the upper part of the bar-shaped steel material removed from the H-shaped steel beam.

[0008] First aspect According to the construction method of the column-shaped improvement body with core material described above, in the dropping process, wall-shaped reinforcements made of multiple bar-shaped steel materials connected by shear reinforcement are placed on both sides of the web, and the H-shaped steel material with the upper part of the bar-shaped steel material attached is dropped into the unhardened column-shaped improvement body while being vibrated.

[0009] 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 improved body. This leaves the wall-shaped reinforcement embedded (left) inside the column-shaped improved body.

[0010] In the present invention, multiple steel bars are connected with shear reinforcement bars to form wall-shaped reinforcements, thereby ensuring the shear strength of the column-shaped improved body. In addition, by attaching the upper part of the steel bar to an H-shaped steel, it is possible to reduce the positional deviation of multiple steel bars relative to the column-shaped improved body.

[0011] In this way, in the present invention, it is possible to suppress the positional deviation of the bar-shaped steel material relative to the column improved body while ensuring the shear strength of the column improved body.

[0012] According to the second aspect The construction method for the columnar improvement body with core material is as follows: According to the first aspectIn 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, 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.

[0013] Second aspect According to the construction method of the columnar improved body with core material, 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.

[0014] Next, in the pulling-up process, the H-shaped steel is pulled up from the column improvement body before hardening, and the connecting rebar is pulled out from between the pair of positioning parts, so that the pair of bar-shaped steel materials are embedded (left) inside the column improvement body.

[0015] In this way, in the present invention, by inserting the connecting rebar between the pair of positioning parts in the dropping process, the movement of the connecting rebar and the multiple steel bars connected by the connecting rebar is restricted, and therefore the positional deviation of the steel bars relative to the columnar improvement body is further suppressed.

[0016] In addition, in the pulling-up process, the connecting rebars come out of the pair of positioning parts by pulling up the H-shaped steel, so that the H-shaped steel can be easily pulled up from the columnar improvement body before hardening.

[0017] According to the third aspect The construction method for the columnar improvement body with core material is as follows: First aspect or According to the second aspectIn the method for constructing a columnar improvement body with a core material, 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 columnar improvement body before hardening while being vibrated, and in the pulling up process, with the upper part of the bar-shaped steel material detached from the bracket, the H-shaped steel is pulled up from the columnar improvement body before hardening.

[0018] Third aspect According to the construction method of the columnar improvement body with core material described above, in the dropping process, 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 unhardened columnar improvement body while being vibrated.

[0019] Next, in the lifting process, with the upper part of the bar-shaped steel material removed from the bracket, the H-shaped steel is lifted up from the unhardened column-shaped improvement body.

[0020] By attaching the upper part of the steel bar to the bracket protruding from the H-shaped steel in this way, the upper part of the steel bar can be more firmly fixed to the H-shaped steel. Therefore, when the H-shaped steel is vibrated in the dropping process, the vibration of the wall reinforcement is reduced, further reducing the positional deviation of the steel bar relative to the column improvement body.

[0021] According to the fourth aspect A columnar improvement body with a core material 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 bars connecting the plurality of steel bars, a second wall-shaped reinforcement having a plurality of steel bars and shear reinforcement bars 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.

[0022] Fourth aspect According to the columnar improvement body with core material, the columnar improvement body is provided in the ground, and a core material is 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.

[0023] The first wall-shaped reinforcement has a plurality of steel bars and shear reinforcement bars connecting the plurality of steel bars. Similarly, the second wall-shaped reinforcement has a plurality of steel bars and shear reinforcement bars connecting the plurality of 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 a connecting bar.

[0024] Here, in the first wall-shaped reinforcement, multiple steel bars are connected by shear reinforcement. In the second wall-shaped reinforcement, multiple steel bars are connected by shear reinforcement. By embedding these first wall-shaped reinforcement and second wall-shaped reinforcement in the column-shaped improved body, the shear strength of the column-shaped improved body can be ensured.

[0025] 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, the positional deviation of the bar-shaped steel material relative to the columnar improvement body can be reduced when embedding a core material in the columnar improvement body.

[0026] In this way, in the present invention, it is possible to suppress the positional deviation of the bar-shaped steel material relative to the column improved body while ensuring the shear strength of the column improved body. Effect of the Invention

[0027] As described above, according to the present invention, it is possible to reduce the positional deviation of the bar-shaped steel material relative to the columnar improvement body. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a vertical cross-sectional view showing a columnar improved body and a core material according to one embodiment. [Diagram 2] 2 is a cross-sectional view taken along line 2-2 of FIG. 1. [Diagram 3] FIG. 2 is a perspective view of the core shown in FIG. [Figure 4] FIG. 1 is an elevational cross-sectional view showing the construction process of a columnar improvement body according to one embodiment. [Diagram 5] 5 is a cross-sectional view taken along line 5-5 of FIG. 4. [Figure 6]5 is a perspective view showing a lower portion of the H-shaped steel and the core material shown in FIG. 4. FIG. [Figure 7] 5 is a perspective view showing an upper portion of the H-shaped steel and the core material shown in FIG. 4. FIG. [Figure 8] FIG. 1 is an elevational cross-sectional view showing the construction process of a columnar improvement body according to one embodiment. [Figure 9] 6(A) and 6(B) are cross-sectional views corresponding to FIG. 5, illustrating a modified example of the core material according to one embodiment. [Figure 10] FIG. 13 is an elevation view illustrating the loading method in the loading experiment. [Figure 11] 1(A) to 1(C) are an elevation view and a cross-sectional view showing the experimental model used in the loading experiment. [Figure 12] 13 is a graph showing the experimental results of a loading experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, one embodiment will be described with reference to the drawings.

[0030] (Columnar improvement body with core material) The improved columnar body with a core material according to this 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.

[0031] (Columnar improved 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 an earth retaining wall (not shown). The columnar improvement body 10 is formed, for example, from hardened soil cement.

[0032] 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 hardening the soil cement formed by stirring and mixing the excavated soil and the cement-based hardening material underground.

[0033] 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. Arrow P, shown appropriately 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). 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.

[0034] (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.

[0035] 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 acting direction of earth pressure (the direction of arrow P) in a plan view. The pair of wall-like reinforcements 20 are arranged opposite each other in the width direction of the columnar improved body 10 (see FIG. 2). The pair of wall-like reinforcements 20 are an example of a first wall-like reinforcement and a second wall-like reinforcement.

[0036] As shown in Fig. 3, each wall reinforcement 20 has a pair of steel bars 22 and a corrugated shear reinforcement bar 24 connecting 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 in the vertical direction along the column improvement body 10 and are arranged with a gap in between in the direction in which earth pressure acts. The pair of steel bars 22 are connected by the corrugated shear reinforcement bar 24.

[0037] The wavy shear reinforcement 24 is formed by bending a straight reinforcing bar into a wave shape in which peaks facing opposite directions alternately repeat. This wavy shear reinforcement 24 is arranged along the columnar improvement body 10 and is arranged across a pair of steel bars 22. In addition, 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.

[0038] In this embodiment, the phases of the wavy shear reinforcement 24 are opposite between the wall reinforcement 20 on one side and the wall reinforcement 20 on the other side, but the phases of the wavy shear reinforcement 24 may be the same, for example. The wavy shear reinforcement 24 is an example of a shear reinforcement.

[0039] The lower portion of a pair of steel bars 22 in one wall-like reinforcement 20 and the lower portion of a pair of steel bars 22 in the other wall-like reinforcement 20 are connected by a pair of connecting bars 26. Specifically, the pair of steel bars 22 in one wall-like reinforcement 20 and the pair of steel bars 22 in the other wall-like reinforcement 20 face each other in the width direction of the columnar improvement body 10 (direction of arrow W).

[0040] Each of the pair of connecting rebars 26 is formed of 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 parts of the bar-shaped steel materials 22 facing each other in the width direction of the columnar improvement body 10, and is joined to the lower parts of these bar-shaped steel materials 22 by welding or the like. The connecting rebars 26 connect the lower parts of the pair of bar-shaped steel materials 22 in one wall-shaped reinforcement bar 20 to the lower parts of the pair of bar-shaped steel materials 22 in the other wall-shaped reinforcement bar 20.

[0041] (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.

[0042] 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 columnar improved body 10 (soil cement) before hardening. Therefore, first, the mounting structure of the core material 12 to the H-shaped steel 30 will be described.

[0043] (Attachment structure of core material to H-beam) 5, the H-shaped steel 30 has a pair of flanges 32 facing each other in the acting direction of earth pressure, and a web 34 connecting the pair of flanges 32. This H-shaped steel 30 is dropped into the inside of the unhardened columnar improvement body 10 with its longitudinal direction aligned in the up-down direction and with the opposing direction of the flanges 32 aligned in the acting direction of earth pressure.

[0044] 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 so as 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 arrow P).

[0045] 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 facing each other in the facing 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 facing direction of the flanges 32 by the pair of inner wall surfaces 40A of the slit 40. The pair of inner wall surfaces 40A are an example of a pair of positioning portions.

[0046] As shown in Fig. 7, a pair of brackets 50 to which the upper parts of the pair of bar-shaped steel materials 22 are attached are provided on both sides of the web 34 of the H-shaped steel 30. The pair of brackets 50 are formed by L-shaped angles in a plan view. The pair of brackets 50 are disposed with a gap between them in the opposing direction of the flanges 32.

[0047] Each of the pair of brackets 50 has a base portion 52 which is joined by welding or the like while being overlapped on the surface of the web 34, and a protruding portion 54 which protrudes from one end of the base portion 52 in a direction outward from the surface of the web 34. The protruding portion 54 is formed in a wall shape facing the flange 32. A mounting reinforcing bar 60 is joined to the surface of the protruding portion 54 by welding or the like.

[0048] 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 the 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.

[0049] (Positioning method) Next, a method for positioning the core material 12 relative to the columnar improved body 10 will be described.

[0050] 4 shows the columnar improvement body 10 (soil cement) formed in the ground G before hardening. A mounting base 70 is provided around the columnar improvement body 10 in the ground G. The mounting base 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 acting direction of earth pressure relative to the columnar improvement body 10.

[0051] The pair of guide beams 72 are formed, for example, from H-shaped steel or the like. The pair of guide beams 72 are arranged parallel to each other with a gap between them in the width direction of the columnar improvement body 10. By inserting the H-shaped steel 30 to which the core material 12 is 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.

[0052] The pair of guide pieces 74 are formed, for example, by 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 to which the core material 12 is 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.

[0053] (Dropping process) Next, the dropping process will be described. In the dropping process, as described above, with the H-shaped steel 30 positioned relative to the columnar improvement body 10, a vibrator 80 such as a vibrating 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.

[0054] Next, when the lower ends of the H-shaped steel 30 and the core material 12 reach a predetermined depth, the vibration exciter 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 column improvement body 10, but is left exposed above ground.

[0055] (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 part of each steel bar 22 is removed from the H-shaped steel 30. This releases the pair of wall-shaped reinforcements 20 from the H-shaped steel 30.

[0056] Next, the vibrator 80 is operated to vibrate the upper end of the H-shaped steel 30 while lifting the H-shaped steel 30. At this time, the connecting rebars 26 come out of a pair of slits 40 formed in 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.

[0057] (effect) Next, the effects of this embodiment will be described.

[0058] According to the construction method of the columnar improvement body with core material of this embodiment, as shown in Figure 4, in the dropping process, the wall-like reinforcements 20 are arranged on both sides of the web 34, and the H-shaped steel 30 to which the upper parts of each bar-shaped steel material 22 of the wall-like reinforcements 20 are attached is dropped into the columnar improvement body 10 before hardening while being vibrated.

[0059] Next, as shown in Fig. 8, in the pulling-up process, the H-shaped steel 30 is pulled up from the unhardened column improvement body 10 with the upper parts of each bar-shaped steel material 22 of the wall-shaped reinforcements 20 removed from the H-shaped steel 30. As a result, a pair of wall-shaped reinforcements 20 are embedded (left behind) inside the column improvement body 10. By reinforcing the column improvement body 10 with this pair of wall-shaped reinforcements 20, damage to the column improvement body 10 due to earth pressure, etc. is suppressed.

[0060] Moreover, by connecting a pair of bar-shaped steel materials 22 with a corrugated shear reinforcement bar 24 to form the wall-shaped reinforcement bar 20, it is possible to ensure the shear strength of the column improvement body 10. Moreover, in this embodiment, it is possible to reduce the steel material cost compared to the case where a steel member such as an H-shaped steel is used as the core material of the column improvement body 10.

[0061] Furthermore, by attaching the upper part of each bar-shaped steel material 22 of the wall-shaped reinforcement 20 to the H-shaped steel 30, when the H-shaped steel material 30 is vibrated during the dropping process, the vibration of the H-shaped steel material 30 and the pair of wall-shaped reinforcement bars 20 attached to the H-shaped steel 30 is reduced, thereby reducing the positional deviation of each bar-shaped steel material 22 relative to the column improvement body 10.

[0062] In this manner, in this embodiment, the shear strength of the column improvement body 10 can be ensured while suppressing the positional deviation of each steel bar 22 relative to the column improvement body 10.

[0063] 6, the lower part of the steel bar 22 in one wall-like reinforcement 20 and the lower part of the steel bar 22 in the other wall-like reinforcement 20 are connected by a connecting bar 26. This further reduces the positional deviation of each steel bar 22 relative to the column improvement body 10 during the dropping process.

[0064] In addition, in the dropping process, with the connecting steel bar 26 inserted into the slit 40 formed at the lower end of the web 34 of the H-shaped steel 30, the H-shaped steel 30 is dropped into the unhardened columnar improvement body 10 while being vibrated.

[0065] As a result, the pair of inner wall surfaces 40A of the slits 40 restrict the movement of the connecting reinforcing bars 26 in the opposing direction of the flanges 32. Therefore, the positional deviation of the lower part of each steel bar 22 relative to the column improvement body 10 is reduced.

[0066] Furthermore, as shown in Figure 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.

[0067] In this manner, by attaching the upper portion of the bar-shaped steel material 22 to the bracket 50 protruding from the web 34 of the H-shaped steel material 30, the upper portion of the bar-shaped steel material 22 can be more firmly fixed to the H-shaped steel material 30. Therefore, when the H-shaped steel material 30 is vibrated in the dropping process, the vibration of the wall-shaped reinforcement 20 is further reduced, and thus the positional deviation of the bar-shaped steel material 22 with respect to the column improvement body 10 is further reduced.

[0068] Moreover, 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, the upper part of the bar-shaped steel material 22 can be easily removed from the mounting rebar 60 in the pulling-up process.

[0069] 5, the pair of wall-shaped reinforcements 20 are arranged to be contained 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 the flanges 32 of the H-shaped steel 30, so that the vibration of the bar-shaped steel material 22 is limited.

[0070] 6, in the pulling-up process, the H-shaped steel 30 is pulled up from the column-shaped improvement body before hardening, so that the connecting steel bar 26 can be easily pulled out of the slit 40. Therefore, the H-shaped steel 30 can be easily pulled up from the column-shaped improvement body 10.

[0071] 3, in this embodiment, a pair of steel bars 22 are connected by one corrugated shear reinforcement 24. Here, for example, when a pair of steel bars 22 are connected in a ladder shape by a plurality of straight shear reinforcement bars, it is necessary to position the plurality of straight shear reinforcement bars with respect to the pair of steel bars 22 at predetermined intervals, and therefore the positioning work of the shear reinforcement bars is time-consuming.

[0072] In contrast, in this embodiment, one corrugated shear reinforcement bar 24 is positioned relative to a pair of steel bars 22, so that 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.

[0073] (Modification) Next, a modification of the above embodiment will be described.

[0074] In the above embodiment, two steel bars 22 are connected by the 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 the corrugated shear reinforcement 24. For example, in the modified example shown in FIG. 9(A), three steel bars 22 arranged in the acting direction of earth pressure (direction of arrow P) are connected by the corrugated shear reinforcement 24.

[0075] In the above embodiment, the pair of wall-shaped reinforcements 20 are arranged so as to be fitted 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 is caused to protrude outward beyond the flanges 32 of the H-shaped steel 30, and a mounting reinforcing bar 60 is fixed to the tip side of the protruding portion 54.

[0076] In the above embodiment, in the dropping step, the steel bar 22 is detachably connected to the mounting rebar 60 via the screw-type mechanical joint 62. However, for example, in the dropping step, the mechanical joint 62 may be filled with a filler such as grout, and the steel bar 22 may be undetachably connected to the mounting rebar 60. In this case, in the pulling step, for example, the mounting rebar 60 or the steel bar 22 is cut, thereby removing the upper part of the steel bar 22 from the H-shaped steel 30.

[0077] Also, 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.

[0078] Moreover, the bracket 50 is not limited to an angle, but may be, for example, a C-shaped steel or a T-shaped steel, etc. Moreover, the bracket 50 is not limited to being fixed to the web 34 of the H-shaped steel 30, but may be fixed to the flange 32.

[0079] In the above embodiment, the pair of steel bars 22 are connected by the corrugated shear reinforcement bars 24. However, the pair of steel bars 22 may be connected in a ladder shape by a plurality of linear shear reinforcement bars.

[0080] 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, or the like.

[0081] 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 disposed 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.

[0082] The pair of slits 40 may be provided as needed and may be omitted as appropriate. Similarly, the pair of connecting reinforcing bars 26 may be provided as needed and may be omitted as appropriate.

[0083] (Loading experiment) Next, the loading experiment of the columnar improved body will be explained.

[0084] In this loading experiment, in order to confirm the shear reinforcement effect of the corrugated shear reinforcement bars 24, a loading experiment was conducted on an experimental model of the columnar improved body 10 in which the core material 12 was embedded.

[0085] (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 at 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 experimental model M2, which will be described later.

[0086] (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 improvement body 90 made of 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 resistance of each of the experimental models M1 to M3.

[0087] In an experimental model M1 shown in Fig. 11(A), no shear reinforcement is provided. In an 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 an experimental model M3 shown in Fig. 11(C), multiple steel bars 92 are surrounded by band-shaped shear reinforcement bars (hoop reinforcement bars) 96.

[0088] (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.

[0089] As can be seen from Fig. 12, in the experimental model M1 in which no shear reinforcement was provided, early shear failure occurred. In contrast, in the experimental model M2 in which the corrugated shear reinforcement 94 was provided, and in the experimental model M3 in which the strip-shaped shear reinforcement 96 was provided, early shear failure was prevented. This confirmed the shear reinforcement effect of the corrugated shear reinforcement 94 and the strip-shaped shear reinforcement 96.

[0090] In addition, the shear strength of the experimental model M2 equipped with the wavy shear reinforcement 94 was slightly smaller than that of the experimental model M3 equipped with the strip-shaped shear reinforcement 96, but the shear strength was comparable to that of the experimental model M3. This confirmed the usefulness of the wavy shear reinforcement 94.

[0091] Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modified examples may be used in appropriate combination, and it is of course possible to implement the present invention in various forms without departing from the gist of the present invention. [Explanation of symbols]

[0092] 10 Improved columnar body 12 Core material 20 Wall muscle (first wall muscle, second wall muscle) 22 Steel bars 24 Wave-shaped shear reinforcement (shear reinforcement) 26 Connecting bars 30 H-beam 40 Slit 40A Inner wall surface (positioning part)

Claims

1. 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.

2. 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.

3. 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.

Images