KR20210047280A - Steel pipe pile section extension method using multi points extension apparatus for underground steel pipe - Google Patents

Abstract

The present invention relates to a multi-shape changing apparatus for an underground steel pipe, wherein a plurality of diameter expansion bodies (20) stretched in a direction perpendicular to a steel pipe (10) inserted into the ground and a plurality of compression bodies (30) installed on ends of the diameter expansion bodies (20) to be moved in a direction perpendicular to the steel pipe (10) as the diameter expansion bodies (20) are stretched are mounted on a rod (15) supplied to the steel pipe (10) in an axial direction of the rod (15), and a steel pipe pile cross section expansion method using the same. The multi-shape changing apparatus for an underground steel pipe is supplied into a steel pipe (10) inserted into the ground and is then operated to have a multi-shape changing unit (11) on the steel pipe (10), and concrete is deposited in the steel pipe (10) to form a synthetic steel pipe pile. The present invention can expand the cross section of the steel pipe (10) while the steel pipe (10) is inserted into the ground to drastically increase the support power of the synthetic steel pipe pile, and obtain a particularly excellent effect in construction requiring high-level support power realization for the steel pipe pile while having limitations on large hole ground excavation such as a floating structure top-down method, expansion of an underground space under a facility, and reinforcement of an existing decrepit structure.

Description

Steel pipe pile section extension method using underground steel pipe multi-deformation device {STEEL PIPE PILE SECTION EXTENSION METHOD USING MULTI POINTS EXTENSION APPARATUS FOR UNDERGROUND STEEL PIPE}

In the present invention, the rod 15 inserted into the steel pipe 10 penetrated into the ground, the expansion and contraction body 20 extending in a direction orthogonal to the steel pipe 10, and the expansion body 20 Underground steel pipe multi-deformation device configured by mounting a plurality of compression bodies 30 that are installed at the ends and moved in a direction orthogonal to the steel pipe 10 as the expansion and contraction body 20 is expanded and contracted in the axial direction of the rod 15, and As a method of expanding the cross section of a steel pipe pile used, an underground steel pipe multi-deformation device is put into the inside of the steel pipe 10 penetrated into the ground, and then operated, a multi-deformation part 11 is performed in the steel pipe 10, and the concrete is placed inside the steel pipe 10. It is to form a synthetic steel pipe pile by pouring.

The cast-in-place pile is a kind of pile foundation in contrast to the ready-made pile, and as shown in FIG. 1, it is constructed by pouring concrete into the pre-drilled excavation hole or the previously penetrated casing 19 and then curing. , Unlike the ready-made piles, since the process of type (打入) the completed pile structure on the ground is unnecessary, there is an advantage of preventing noise or vibration caused in the driving process.

In general, the pile foundation resists the load of the upper structure of the pile or the negative pressure of the underground structure due to the groundwater due to the tip bearing capacity and the main surface friction force, so that the desired bearing capacity is expressed. An excavation depth greater than or equal to the desired rock layer must be secured, or if the rock layer is too deep, a root length of a predetermined length or more must be secured.

In addition, the pile behaves not only as a structure that simply transmits the upper load to the ground, but is itself a kind of long column structure that must resist axial compression, transverse bending, and buckling stress, as shown in FIG. 1. Likewise, a reinforcing bar 99 or a steel frame is usually embedded in the concrete body as a reinforcing material.

On the other hand, as a kind of cast-in-place pile consisting of such a reinforcing material, a composite concrete pile for cast-in-place steel pipes that pours and cures concrete in a state in which the steel pipes remain after having penetrated the steel pipes 10 into the ground has been developed. No. 2018-9196, etc. may be mentioned.

Conventional cast-in-place composite steel pipe piles, including Korean Patent Publication No. 2018-9196, have a structure in which the steel pipe 10, which is a reinforcing material, covers the pile, unlike the traditional cast-in-place pile, in which the main reinforcement is embedded in the pile. It is known that the steel pipe 10 serves as a formwork and a reinforcing material of the concrete to be poured, and is known to be advantageous in securing the structural rigidity of the pile structure itself compared to the embedded reinforcement material.

In a traditional cast-in-place pile, as shown in FIG. 1, the ground is excavated and drilled using an excavating body 91 such as an auger mounted on the excavation equipment 90, but with the excavation of the excavating body 91, When the casing 19 holding the hollow wall is penetrated, and the bottom of the casing 19 reaches the target depth, the excavator 91 is withdrawn and a reinforcing material such as reinforcing bar 99 is introduced into the casing 19, and the drawing Although not shown above, concrete is poured into the excavation hole.At this time, the casing 19 is drawn immediately before the concrete is placed, at the same time as the concrete is placed, or immediately after the concrete is placed.

That is, in the construction of traditional cast-in-place piles, the casing 19 is a temporary structure used for the purpose of maintaining empty walls and is recovered and reused in the final stage, whereas in the cast-in-place composite steel pipe pile, the steel pipe 10 is permanently retained as a reinforcing material. There is a difference.

These traditional casing (19) recovery type cast-in-place piles and cast-in-place composite steel pipe piles cannot be called an absolutely advantageous construction method, and can be said to be a construction method applied according to various conditions in consideration of the advantages and disadvantages of each.

First of all, the traditional casing (19) recovery type cast-in-place pile is a structure in which the concrete to be poured and the ground are directly in contact with each other, making it easy to secure the main surface friction in the completed pile, as well as the recovery and reuse of the casing 19, which is an expensive material. While it is possible to reduce the construction cost, there is a problem in that the stiffness of the pile structure itself is relatively weak, and the construction speed is lowered during the process of drawing and reusing the casing 19.

On the other hand, synthetic steel pipe piles cast in place are advantageous in securing the structural rigidity of the pile structure itself as described above.In the ground where the tip bearing capacity is sufficiently secured, the cross-sectional area of the pile can be reduced or the number of constructions can be reduced, but the contact surface between the pile and the ground As it is formed on the surface of the steel pipe 10, it is disadvantageous in securing the main surface friction.

In particular, in the construction of synthetic steel pipe piles cast in place, the casing 19 and the steel pipe 10 for reinforcing the pile may be separately configured, and in this case, the casing 19 and the steel pipe 10 for reinforcing the pile may be separately configured with the excavating body 91 when drilling the first drilling hole. ) After inserting the reinforcing steel pipe 10 into the interior, the casing 19 is pulled out and withdrawn.If the excavation casing 19 and the reinforcing steel pipe 10 are configured separately, the steel pipe 10 and the drilling hole A cavity is formed between the hollow walls, or a considerable disturbance is inevitable in the ground around the piles, so the actual main surface friction cannot be expected.

The present invention is invented in view of the above-described problems, and is mounted on a rod 15 that is inserted into the steel pipe 10 penetrated into the ground and expands and contracts in a direction orthogonal to the steel pipe 10, and It is installed at the end of the expansion body 20 and consists of a pressing body 30 that moves in a direction orthogonal to the steel pipe 10 as the expansion and contraction body 20 expands and contracts, and the expansion body 20 is a steel pipe in a contracted state. (10) After being introduced into the interior, as the expansion body 20 is elongated, the compression body 30 presses the steel pipe 10 to the outside, so that the steel pipe 10 at the compression portion expands to the outside, and the deformation portion 11 protrudes. In the underground steel pipe deformation device in which) is formed, a plurality of diameter expansion bodies 20 and compression bodies 30 are mounted at equal intervals in the axial direction of the rod 15, and the rod 15 in the axial direction of the rod 15 The activator 45, which is freely activating (sliding), is coupled, one end is hinged to the rod 15, the other end is hinged to the lower slewing plate 72, the upper rotating plate 71, and one end is the activating body The expansion body 20 is composed of a lower rotating plate 72 hinged to the upper rotating plate 71 and the other end is hinged to 45, and the upper rotating plate 71 and the lower rotating body of the expanding body 20 A compression body 30 is installed at the connection portion between the copper plates 72, and the lowermost expansion body 20 among the plurality of expansion bodies 20 has an upper drive body that is close to and spaced apart from each other in a direction parallel to the rod 15. 61) and the lower driving body 62 are installed, one end of the upper rotating plate 71 of the lowermost expanding body 20 is hinged to the upper driving body 61 and the other end is hinged to the lower rotating plate 72 And, one end of the lower rotating plate 72 of the lowermost expansion body 20 is hinged to the lower driving body 62, and the other end is hinged to the upper rotating plate 71, and the active body 45 and the lower drive The sieve 62 is connected by a connecting rod 55, and as the upper driving body 61 and the lower driving body 62 are close and spaced apart from each other, the entire dilating body 20 expands and contracts while the compression body 30 It is an underground steel pipe multi-deformation device characterized by moving in a direction orthogonal to the steel pipe (10).

In addition, in the steel pipe pile section expansion method using the underground steel pipe multi-deformation device, the step of intruding the steel pipe 10 into the ground, and when the steel pipe 10 reaches a target depth, the entire expansion body ( The step of inserting the underground steel pipe multi-deformation device in the contracted state 20), and the expansion body 20 of the underground steel pipe multi-deformation device is extended so that the compression body 30 expands and deforms the steel pipe 10, thereby making the steel pipe 10 Forming the deformation part 11 in the, and the step of withdrawing the underground steel pipe multi-deformation device to the outside of the steel pipe 10 after contracting the expansion body 20, and pouring and curing concrete in the steel pipe 10 It is a steel pipe pile cross-section expansion method using an underground steel pipe multi-deformation device characterized by consisting of.

Through the present invention, it is possible not only to expand the cross section of the cast-in-place synthetic steel pipe pile in the ground, but also to build a solid coupling structure between the pile and the ground by forming repetitive irregularities on the outer circumferential surface, thereby dramatically increasing the bearing capacity of the steel pipe pile. Can be increased by

In particular, since the cross section of the steel pipe 10 can be expanded while the steel pipe 10 constituting the steel pipe pile is penetrated into the ground, large diameters such as reinforcement of existing old structures, expansion of the underground space under existing facilities, and the floating structure reverse punching method. It is advantageous in construction that requires a high level of support for steel pipe piles while there are restrictions on excavation on the ground.

In addition, as the protruding portion of the steel pipe 10 compresses the surrounding ground, the ground structure may be densified, and by combining the protruding portion of the steel pipe 10 to the densified ground, a further reinforced binding force may be expressed, and the rod ( Through the expansion body 20 and the pressing body 30 mounted on a plurality of 15) and driven at a time, a plurality of protruding portions arranged in the axial direction of the steel pipe 10 can be formed at a time, so that rapid construction is possible.

As a result, it is possible to remarkably improve the main surface friction or binding force while maintaining the unique structural rigidity of the cast-in-place synthetic steel pipe pile, thereby improving the performance of the steel pipe pile foundation and securing the stability of the upper structure.

1 is an explanatory view of a conventional cast-in-place pile construction process
Figure 2 is an explanatory diagram of the construction process of the present invention
3 is an explanatory diagram of an underground steel pipe deformation method according to the present invention
Figure 4 is a perspective view of a contraction state of the present invention expansion device
Figure 5 is a perspective view of an expanded state of the present invention expansion device
6 is an explanatory diagram of an operation method of the present invention
7 is a perspective view of a modified embodiment of the device of the present invention

The detailed configuration and execution process of the present invention will be described with reference to the accompanying drawings.

First, Figure 2 shows the construction process of the present invention, as shown, into the inside of the steel pipe 10 penetrated into the ground, a plurality of expansion bodies 20 mounted at equal intervals on the rod 15 ), and a plurality of deformation parts 11 in the steel pipe 10 by inputting the underground steel pipe multi-deformation device of the present invention consisting of the pressure body 30, and then pouring and curing concrete inside the steel pipe 10. The cast-in-place pile to which the invention was applied is completed.

That is, the present invention does not form unevenness in the cast-in-place pile by partially expanding or deformed steel pipe 10 in the ground or partially additionally excavating an excavation hole, but the steel pipe 10 In the state of being penetrated into the ground, an underground steel pipe multi-deformation device is inserted into the steel pipe 10 to press the steel pipe 10 from the inside to the outside, thereby forming the deformation part 11 in the corresponding part.

Therefore, in the case of intruding the steel pipe 10 processed in advance into the ground, inevitable extreme penetration resistance, disturbance of the surrounding ground, and loss of principal frictional force due to this are not accompanied in the present invention at all, and the site in the state of existence of the steel pipe 10 It is possible to form a partial enlargement or unevenness in the cast pile, and in the prior art, it is possible to apply even in adverse conditions such as soft ground, where partial expansion of the cast-in-place pile was impossible.

In addition, after the small-diameter excavation and the input of the small-sized steel pipe 10, a large-diameter cast-in-place composite steel pipe pile can be constructed by expanding the steel pipe 10 in the ground, so that the formation of a large-diameter drilling hole is fundamentally impossible to reinforce the lower part of the existing structure. It is particularly advantageous in performing construction, development of an underground space under an existing facility, or performing a floating structure reverse punching method.

The conventional partial expansion type cast-in-place pile can be applied only to the ground where the hollow wall of the drilling hole is maintained by magnetic force without the casing (19), and a special excavator is inserted into the drilling hole in the state where the hollow wall ground is exposed. It was carried out in a way that additional excavation was carried out on the side walls, and in fact, it was only applicable to extremely stable rocky ground.

In particular, it was difficult to cover the soil and slime generated in the lateral additional excavation process on the excavation hole, so these soils and slime were forced to remain at the bottom of the excavation hole. Not only did it act as a factor that seriously damages the tip bearing capacity as well as the strength of the ball, and there was a serious problem of frequent collapse of the upper ground as a bar inevitably accompanied by considerable vibration and shock during lateral excavation of the empty wall.

On the other hand, in the present invention, as shown in Figs. 2 and 3, the steel pipe 10 and the excavation hole are partially enlarged while the steel pipe 10 is penetrated into the ground. Not only can it be applied irrespective of the problem, and problems related to soiling and collapse do not occur at all, and a plurality of deformable portions 11 can be formed freely as shown in the drawing.

In particular, since a plurality of deformation portions 11 arranged at equal intervals in the axial direction of the steel pipe 10 can be formed at one time, rapid construction is possible, thereby reducing construction time and construction cost.

As such, the present invention is a multi-underground steel pipe composed of a plurality of expansion bodies 20 and compression bodies 30 arranged and mounted on the rod 15 into the steel pipe 10 in a state penetrated into the ground, as shown in FIG. By inserting a deformation device, the compression body 30 presses the steel pipe 10 from the inside to the outside to forcibly deform the steel pipe 10 to form the deformed part 11 with an enlarged cross section, and the basic configuration of the underground steel pipe multi-deformation device of the present invention This is shown in FIGS. 4 and 5.

4 and 5 are respectively showing the contracted state and the expanded state of the present invention expansion device, as shown in these drawings, the underground steel pipe multi-deformation device of the present invention is a rod that is inserted into the steel pipe 10 penetrated into the ground The expansion body 20 that is mounted on the steel pipe 10 and expands and contracts in a direction orthogonal to the steel pipe 10, and is installed at the end of the expansion body 20 so as to be orthogonal to the steel pipe 10 as the expansion body 20 expands and contracts. It consists of a pressing body 30 that moves in the direction.

The underground steel pipe multi-deformation device of the present invention is inserted into the steel pipe 10 in a contracted state as shown in FIG. 4, and then as the expanding body 20 is elongated as in FIG. 5, FIG. As in 3, the pressing body 30 presses the steel pipe 10 outward, so that the steel pipe 10 at the pressing portion expands to the outside, thereby forming a protruding deformation portion 11.

In particular, as shown in Figs. 2 to 6, a plurality of diameter expansion bodies 20 and compression bodies 30 are mounted at equal intervals in the axial direction of the rod 15 to form a plurality of deformable parts 11 at once. have.

4 and 5, the rod 15 is coupled to an active body 45 that slides freely in the axial direction of the rod 15, one end is hinged to the rod 15 and the other end is lower An enlarged body with an upper rotating plate 71 hinged to the rotating plate 72, one end hinged to the active body 45 and the other end hingedly connected to the upper rotating plate 71. 20) is configured, and the compression body 30 is installed at the connection between the upper and lower rotating plates 71 and 72 of the expanding body 20.

In addition, the lowermost expansion body 20 among the plurality of expansion bodies 20 is provided with an upper driving body 61 and a lower driving body 62 that are adjacent and spaced apart from each other in a direction parallel to the rod 15. One end of the upper rotating plate 71 of the lower expanding body 20 is hinged to the upper driving body 61, and the other end is hinged to the lower rotating plate 72, and the lower rotating plate ( 72) One end is hingedly connected to the lower driving body 62, and the other end is hingedly connected to the upper rotating plate 71.

As such, the underground steel pipe multi-deformation device of the present invention is composed of a plurality of expansion bodies 20 and compression bodies 30 arranged at equal intervals in the axial direction of the rod 15, and in these multiple expansion bodies 20 , The active body 45 and the lower driving body 62 are connected by a connecting rod 55, and as the upper driving body 61 and the lower driving body 62 are close and spaced apart from each other, the entire expansion body 20 is The compression body 30 is moved in a direction orthogonal to the steel pipe 10 while being stretched and contracted.

That is, not each of the plurality of expansion body 20 is provided with a separate driving means, but the lower driving body 62 for driving the lowermost expansion body 20 is the active body 45 of the entire expansion body 20 By being connected with the connecting rod 55, the driving force of the single upper driving body 61 and the lower driving body 62 is configured to be propagated to the entire expansion body 20, as shown in FIG. 6, the lowermost expansion body As the lower driving body 62 configured in (20) rises, the active body 45 connected to the connecting rod 55 is raised together, so that the entire expansion body 20 is driven at a time.

In the present invention underground steel pipe multi-deformation device shown in Figures 4 and 5, the expansion body 20 is composed of a pair of left and right, and the compression body 30 is hingedly connected to each end, the pressing body 30 Is a plate body that is gently curved in a plane, and as shown in the drawing, when attaching the pressing body 30 to the connecting portion of the upper rotating plate 71 and the lower rotating plate 72, the upper rotating plate 71 and the lower rotating plate are By mounting through the hinge connecting the copper plate 72 and the shaft bridge 73 connected coaxially, the pressing body 30 and the diaphragm 20 can be connected by a hinge of a rotating shaft parallel to the steel pipe 10. I can.

Here, the meaning of being parallel to the steel pipe 10 means being parallel to the central axis of the steel pipe 10, and in the case of the steel pipe 10 vertically penetrating the ground, the diameter expansion body 20 and the pressure body 30 The hinge that connects is also has a vertical axis of rotation.

In this way, by connecting the compression body 30 and the diameter expansion body 20 with a hinge of a rotation shaft parallel to the steel pipe 10, the formation of stresses other than the axial stress on the diameter expansion body 20, that is, bending or torsional stress, is minimized. This can be, as the compression body 30 freely rotates or slides along the curved surface of the inner circumferential surface of the steel pipe 10, the center line of the action of the pressing force by the compression body 30, the central axis of the expansion body 20, and the steel pipe. This is because the center of the plane of (10) naturally coincides.

If the distal ends of the compression body 30 and the expansion body 20 are tightened, when the central axis of the expansion body 20 is separated from the center of the steel pipe 10, the action center line and the expansion body of the compression force by the compression body 30 As the slope between the center lines of (20) is formed, bending and torsional stresses are inevitably formed in the expansion body 20, which acts as an element that erodes the performance and durability of the expansion body 20.

As described above, in the embodiment of applying the rotating plate of the underground steel pipe multi-deformation device of the present invention, the pressure body 30 is perpendicular to the steel pipe 10 as the upper driving body 61 and the lower driving body 62 are close to each other and spaced apart from each other. As it moves to, the steel pipe 10 is deformed. As shown in FIG. 7, a plurality of upper and lower rotating plates 71 and 72 are connected to a single upper and lower driving bodies 61 and 62. It may be configured radially in a plane, and in forming the deformed portion 11 in the steel pipe 10, even with a simple configuration, a more efficient operation is possible.

As described above, in the underground steel pipe multi-deformation device of the present invention, a plurality of expansion bodies 20 are mounted on the rod 15, and the rod 15 is a connecting pipe that connects the expansion body 20 with the equipment on the ground. , When a plurality of unit rods 15 are connected, the total extension can be adjusted, and a fluid pressure cylinder is applied as the upper driving body 61 and the lower driving body 62 of the lowermost expansion body 20 The working fluid piping of the hydraulic cylinder may be embedded in the rod 15.

That is, the rod 15 of the present invention plays the role of a guiding or supporting member in which the above-described active body 45 is combined and freely active (sliding), and at the same time, ground equipment such as a pile driver or a crane and a plurality of expansion bodies As a configuration connecting (20), a hydraulic fluid piping that drives the hydraulic cylinder may be embedded, and the hydraulic oil piping connected to the ground through the rod 15 is not shown in the drawing, but the hydraulic oil is pumped. It is connected to a hydraulic pump or the like to drive the upper driving body 61 and the lower driving body 62.

In this way, by using the underground steel pipe multi-deformation device of the present invention, a plurality of deformation portions 11 protruding outward can be formed in the steel pipe 10 in the state of being penetrated into the ground, whereby the steel pipe 10 is covered as a reinforcing material. In the applied cast-in-place synthetic steel pipe piles, it is possible to dramatically improve the bearing capacity including the main surface friction, and the execution process of the steel pipe pile section expansion method of the present invention will be described as follows.

First, as shown in the left end of FIG. 2, the step of penetrating the steel pipe 10 into the ground is performed.

The ground penetration of the steel pipe 10 can be performed in a variety of ways, and as shown in FIG. 1, the method of using the casing 19 to be penetrated with the excavator 91 in the ground to be utilized as the steel pipe 10 Of course, it is also possible to insert a separate steel pipe 10 into the casing 19 and then pull out the casing 19 while only the steel pipe 10 remains. In the ground that can be maintained, a method of first drawing the casing 19 and then inserting the steel pipe 10 into the excavation hole may be applied.

When the steel pipe 10 reaches the target depth, the step of introducing the underground steel pipe multi-deformation device of the present invention in a state in which the expansion body 20 is contracted into the steel pipe 10 is performed, and the expansion body 20 is contracted. In the present invention, since the maximum width in the plane of the underground steel pipe multi-deformation device is set to be less than the inner diameter of the steel pipe 10, it is possible to smoothly insert the underground steel pipe multi-deformation device into the steel pipe 10.

When the underground steel pipe multi-deformation device put into the steel pipe 10 reaches the point where the deformation part 11 is planned to be formed, the expansion body 20 of the underground steel pipe multi-deformation device is extended so that the pressure body 30 expands the steel pipe 10 By deforming, a step of forming a plurality of deformed portions 11 in the steel pipe 10 at once is performed.

Once the formation of the multi-deformation part 11 for a specific section of the steel pipe 10 is completed, the expansion body 20 is contracted and the underground steel pipe multi-deformation device is moved, and then the expansion body 20 is re-extended to a new section. In a manner in which the multi-deformation portion 11 is performed, the multi-deformation portion 11 for a wide range may be formed as in the central portion of FIG. 2.

When the formation of the entire deformation part 11 is completed, the step of withdrawing the underground steel pipe multi-deformation device to the outside of the steel pipe 10 after contracting the expansion body 20 is performed, and then a rebar 99 cage in the steel pipe 10 Alternatively, the step of reinforcing reinforcement such as steel frame, pouring concrete, and curing is performed, thereby completing the steel pipe pile section expansion method using the underground steel pipe multi-deformation device of the present invention.

10: steel pipe
11: deformation part
15: load
19: casing
20: expansion body
30: pressure body
45: active body
55: connecting rod
61: upper driving body
62: lower driving body
71: upper rotating plate
72: lower rotating plate
73: congratulatory board
90: excavation equipment
91: excavator
99: rebar

Claims (1)

It is installed on the rod 15 that is inserted into the steel pipe 10 penetrated into the ground and expands and contracts in a direction orthogonal to the steel pipe 10, and the expansion body 20 is installed at the end of the expansion body 20 to expand the diameter body ( 20) is composed of a pressing body 30 that moves in a direction orthogonal to the steel pipe 10 as it expands and contracts, and after the expansion body 20 is put into the steel pipe 10 in a contracted state, the expansion body 20 It is an underground steel pipe deformation device in which the compression body 30 presses the steel pipe 10 outward as the compression body 30 expands to the outside and the protruding deformation part 11 is formed. The rigid body 20 and the pressing body 30 are mounted at equal intervals in the axial direction of the rod 15, and the rod 15 is coupled with an active body 45 that slides freely in the axial direction of the rod 15 And, one end is hinged to the rod 15, the other end is hinged to the upper rotating plate 71 connected to the lower rotating plate 72, one end is hinged to the active body 45, and the other end is the upper rotating plate 71 ), the expansion body 20 is composed of a lower rotating plate 72 hinged to the expansion body 20, and a pressing body 30 is installed at the connection between the upper rotating plate 71 and the lower rotating plate 72 of the expanding body 20 And, the lowermost expansion body 20 among the plurality of expansion bodies 20 is provided with an upper driving body 61 and a lower driving body 62 that are close to each other and spaced apart from each other in a direction parallel to the rod 15, One end of the upper rotating plate 71 of the lower expanding body 20 is hinged to the upper driving body 61, and the other end is hinged to the lower rotating plate 72, and the lower rotating plate ( 72) One end is hinged to the lower driving body 62 and the other end is hingedly connected to the upper rotating plate 71, and the active body 45 and the lower driving body 62 are connected by a connecting rod 55, and the upper Underground steel pipe in which the compression body 30 moves in a direction orthogonal to the steel pipe 10 as the entire diameter expansion body 20 expands and contracts as the driving body 61 and the lower driving body 62 are close to each other and spaced apart from each other. In the steel pipe pile cross-section expansion method using a multi-deformation device,
Penetrating the steel pipe 10 into the ground;
When the steel pipe 10 reaches the target depth, introducing an underground steel pipe multi-deformation device in a state in which the entire expansion body 20 is contracted into the steel pipe 10;
Forming a deformation part 11 in the steel pipe 10 by extending the expansion body 20 of the underground steel pipe multi-deformation device so that the compression body 30 enlarges and deforms the steel pipe 10;
The step of withdrawing the underground steel pipe multi-deformation device to the outside of the steel pipe 10 after contracting the expansion body 20;
Steel pipe pile cross-section expansion method using an underground steel pipe multi-deformation device, characterized in that consisting of a step of pouring and curing concrete in the steel pipe (10).

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