RING-SHAPED COFFERDAM AND TEMPORARY PIT EXCAVATION STRUCTURE USING TAPERED SQUARE PIPE, AND CONSTRUCTION METHOD THEREOF

Abstract

A ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes includes a plurality of tapered square pipes a trapezoidal cross-section, in which the plurality of tapered square pipes each have a coupling protrusion or a coupling groove formed in a longitudinal direction on a first side, the plurality of tapered square pipes each have a coupling protrusion or a coupling groove formed in the longitudinal direction on a second side, the plurality of tapered square pipes are assembled by coupling the coupling protrusions and the coupling grooves, a long side of two parallel sides of the trapezoid is disposed outside, and a short side is disposed inside.

Claims

1. A ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes, the structure comprising a plurality of tapered square pipes a trapezoidal cross-section, wherein the plurality of tapered square pipes each have a coupling protrusion or a coupling groove formed in a longitudinal direction on a first side, the plurality of tapered square pipes each have a coupling protrusion or a coupling groove formed in the longitudinal direction on a second side, the plurality of tapered square pipes are assembled by coupling the coupling protrusions and the coupling grooves, a long side of two parallel sides of the trapezoid is disposed outside, and a short side is disposed inside.

2. The structure of claim 1, wherein the coupling protrusion of the first tapered square pipe has a rectangular cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

3. The structure of claim 1, wherein the coupling protrusion of the first tapered square pipe has a T-shaped cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

4. The structure of claim 1, wherein the coupling protrusion of the first tapered square pipe has a trapezoidal cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

5. The structure of claim 1, wherein the first tapered square pipe and the second tapered square pipe are combined by welding four flat plates.

6. The structure of claim 1, further comprising a guide member that is fitted in an upper end of one of the plurality of tapered square pipes, wherein the guide member has: a fitting portion that is fitted in an upper end of one of the plurality of tapered square pipes; and a guide portion that horizontally extends from the fitting portion.

7. The structure of claim 1, wherein tapered cross-sections of some of the plurality of tapered square pipes are inclined at different angles.

8. The structure of claim 1, further comprising an anchor an anchor member that is fitted in a lower end of one of the plurality of tapered square pipes, wherein the anchor member has: a fitting portion formed at an upper end of the anchor member to be fitted in a lower end of one of the plurality of tapered square pipes; and an anchor portion extending a predetermined length from the fitting portion and decreasing in cross-sectional area toward a lower end, and an upper end of the anchor portion is larger in cross-sectional area than the fitting portion.

9. A method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes, the method comprising: driving a first tapered square pipe having a coupling groove formed in a longitudinal direction on a side; putting a second tapered square pipe having a coupling protrusion formed in a longitudinal direction on a side close to an upper end of the first tapered square pipe; fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe; and driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe.

10. The method of claim 9, further comprising welding respectively the first tapered square pipe and the second tapered square pipe before the driving of the first tapered square pipe, wherein, in the welding, the first tapered square pipe and the second tapered square pipe are respectively welded using four flat plates.

11. The method of claim 10, further comprising: measuring side pressure of an area where the first tapered square pipe and the second tapered square pipe are installed; determining thickness of the plates in accordance with the result of measuring the side pressure.

12. The method of claim 11, wherein the determining of thickness of the plates in accordance with the result of measuring the side pressure determines the thickness of the plates as 10% or less of entire width of the first tapered square pipe or the second tapered square pipe when the measured side pressure is less than a predetermined value, as the result of measurement.

13. The method of claim 11, wherein the determining of thickness of the plates in accordance with the result of measuring the side pressure determines the thickness of the plates as 11% or more of entire width of the first tapered square pipe or the second tapered square pipe when the measured side pressure is a predetermined value or more, as the result of measurement.

14. The method of claim 9, wherein the coupling protrusion of the first tapered square pipe has a rectangular cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

15. The method of claim 9, wherein the coupling protrusion of the first tapered square pipe has a T-shaped cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

16. The method of claim 9, wherein the coupling protrusion of the first tapered square pipe has a trapezoidal cross-section, and the coupling groove of the second tapered square pipe is formed to correspond to the coupling protrusion.

17. The method of claim 9, further comprising coupling a guide member to the upper end of the first tapered square pipe after the driving of the first tapered square pipe, wherein the guide member has: a fitting portion that is fitted in an upper end of one of the plurality of tapered square pipes; and a guide portion that horizontally extends from the fitting portion.

18. The method of claim 17, comprising, after the coupling of the guide member: putting the second tapered square pipe to the upper end of the first tapered square pipe; fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe through the guide member; and driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe.

Description

DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a view showing the configuration of a temporary structure for blocking earth and sand in the related art.

[0038] FIG. 2 is a view showing a coupling structure of a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0039] FIG. 3 is a plan view of the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0040] FIGS. 4 to 6 are views showing another coupling structure of a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0041] FIG. 7 is a perspective view of a tapered square pipe included in the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0042] FIG. 8 is a plan view of a guide member according to an embodiment of the present invention.

[0043] FIG. 9 is a view showing construction state using a guide member according to an embodiment of the present invention.

[0044] FIG. 10 is a view showing construction state using an anchor member according to an embodiment of the present invention.

[0045] FIGS. 11 to 14 are flowcharts of a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

BEST MODE

[0046] When it is determined that the subject of the present invention may be unnecessarily made unclear, the detailed description will be omitted.

[0047] Embodiments described herein may be changed in various ways and various shapes, so specific embodiments are shown in the drawings and will be described in detail in this specification. However, it should be understood that the exemplary embodiments according to the concept of the present disclosure are not limited to the embodiments which will be described hereinbelow with reference to the accompanying drawings, but all of modifications, equivalents, and substitutions are included in the scope and spirit of the disclosure.

[0048] It is to be understood that when one element is referred to as being “connected to” or “coupled to” another element, it may be connected directly to or coupled directly to another element or be connected to or coupled to another element, having the other element intervening therebetween. On the other hand, it is to be understood that when one element is referred to as being “connected directly to” or “coupled directly to” another element, it may be connected to or coupled to another element without the other element intervening therebetween. Further, the terms used herein to describe a relationship between elements, that is, “between”, “directly between”, “adjacent” or “directly adjacent” should be interpreted in the same manner as those described above.

[0049] Terms used in the present invention are used only in order to describe specific exemplary embodiments rather than limiting the present invention. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” or “have” used in this specification, specify the presence of stated features, steps, operations, components, parts, or a combination thereof, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or a combination thereof.

[0050] FIG. 2 is a view showing a coupling structure of a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention and FIG. 3 is a plan view of the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0051] Referring to FIG. 2, a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes a according to an embodiment of the present invention includes a plurality of tapered square pipes having a trapezoidal cross-section. The tapered square pipes each may have a coupling protrusion or a coupling groove formed in the longitudinal direction on a first side and a coupling protrusion or a coupling groove formed in the longitudinal direction on a second side.

[0052] In detail, as shown in FIG. 2 (the right tapered square pipe is referred to as a first tapered square pipe and the left tapered square pipe is referred to as a second tapered square pipe for helping understanding), a coupling protrusion 211 may be formed on a first side (left side) of the first tapered square pipe 210 and a coupling groove 212 may be formed on a second side (right side) of the first tapered square pipe 210.

[0053] Further, a coupling protrusion 221 may be formed on a first side (left side) of the second tapered square pipe 220 and a coupling groove 222 may be formed a second side (right side) of the second tapered square pipe 220.

[0054] Further, in the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, the tapered square pipes are assembled by coupling the coupling protrusions and the coupling grooves with the long side of two parallel sides of the trapezoid disposed outside and the short side disposed inside, whereby a ring-shaped cofferdam structure can be achieved.

[0055] FIG. 3 is a plan view of the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes that has the coupling structure described above in accordance with an embodiment of the present invention.

[0056] The ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention uses tapered square pipes having a trapezoidal cross-section and uses an arch structure such that a component of force (compression force) acts between the tapered square pipes, so there is an effect that a supporting force is considerably improved.

[0057] Further, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention has various advantages in comparison to the related art, and one of the advantages is that the structure can be constructed at a place with large side pressure.

[0058] In the related art, a two-row sheet pile wall is used at areas with large side pressure to solve this problem, such a two-row water stop cofferdam wall is embedded in the ground by driving sheet piles in two rows, and the space between the two rows of sheet piles is usually filled with good-quality soil (yellow soil) or sand as a geomembrane (filler material). Further, tie cables are bound left and right and up and down with regular intervals to prevent the walls from opening or bulging due to the weight of the soil when the good-quality soil is poured between the walls, which is a method that is generally used to prevent sheet pile walls from being deformed and opened is generally used.

[0059] However, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention is constructed by coupling a plurality of tapered square pipes and walls are formed by two-row plates. Accordingly, it is possible to achieve the same effect as the case when sheet piles are arranged in two rows.

[0060] That is, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention has the advantage that it is possible to prevent a wall from deforming and opening even without using tie cables and wales.

[0061] Further, in the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, the coupling protrusions formed on the tapered square pipes are fitted in corresponding coupling grooves, respectively, and the coupling grooves function as guides when they are coupled. Accordingly, convenience of construction is improved and the strength of the entire structure can be improved by maintaining a firm coupling structure after coupling them, so excellent supporting force can be secured.

[0062] Further, a plurality of tapered square pipes according to an embodiment of the present invention may be coupled by welding four flat plates.

[0063] There is a method of constructing a cofferdam using a plurality of cylindrical piles as one of technologies of constructing a cofferdam in the related art, but such cylindrical piles are manufactured through a process of winding plates, so there is a limit in thickness.

[0064] In detail, the since the cylindrical piles are manufactured by winding plates, the diameter of the entire cylindrical piles is unavoidably influenced by the thickness of the plates. The diameter of the cylindrical piles and the thickness of the plates are in a proportional relationship. Accordingly, the thickness of the plates is influenced by the diameter of the entire cylindrical piles.

[0065] If a cofferdam structure is constructed at a place with large side pressure using cylindrical piles, it is required to secure a large supporting force due to the large side pressure and plates have to be thick to secure a large supporting force. However, when the thickness of plates is increased, the diameter of the entire cylindrical pies is increased, so construction is difficult. Further, the wall of the cofferdam structure is excessively thick, so the space that is secured inside may be reduced.

[0066] However, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention uses a plurality of tapered square pipes and the tapered square pipes are coupled by welding four flat plates. Accordingly, it is possible to maintain the width of the entire tapered square pipes (corresponding to the diameter of cylindrical piles) and increase the thickness of plates.

[0067] Therefore, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention can be very simply constructed at a place with large side pressure, as compared with using cylindrical piles in the related art, by removing the problems described above, thereby being able to secure a sufficient space inside the cofferdam structure.

MODE FOR INVENTION

[0068] FIGS. 4 to 6 are views showing another coupling structure of a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0069] Referring to FIG. 4A, in a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, when a first tapered square pipe 410a that is one of a plurality of tapered square pipes 410a and 420a has a coupling protrusion 411a formed in the longitudinal direction and a second tapered square pipe 420a that is one of the plurality of tapered square pipes 410a and 420a has a coupling groove 422a formed in the longitudinal direction to fit the coupling protrusion 411a therein, the coupling protrusion 411a of the first tapered square pipe 410a may have a T-shaped cross-section and the coupling groove 422a of the second tapered square pipe 420a may be formed to correspond go the coupling protrusion 411a.

[0070] In the case of FIG. 4, the supporting force between the first tapered square pipe and the second tapered square pipe can be further improved than the case of FIG. 2.

[0071] Further, referring to FIG. 4B, coupling protrusions 411b may be formed on two sides of a first tapered square pipe 410b and coupling grooves 422b may be formed on two sides of a second tapered square pipe 420b. An entirely ring-shaped structure can be achieved by alternately arranging the first tapered square pipe 410b and the second tapered square pipe 420b.

[0072] Referring to FIG. 5A, in a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, when a first tapered square pipe 510a that is one of a plurality of tapered square pipes 510a and 520a has a coupling protrusion 511a formed in the longitudinal direction and a second tapered square pipe 520a that is one of the plurality of tapered square pipes 510a and 520a has a coupling groove 522a formed in the longitudinal direction to fit the coupling protrusion 511a therein, the coupling protrusion 511a of the first tapered square pipe 510a may have a trapezoidal cross-section and the coupling groove 522a of the second tapered square pipe 520a may be formed to correspond go the coupling protrusion 511a.

[0073] Further, referring to FIG. 5B, coupling protrusions 511b may be formed on two sides of the first tapered square pipe 510b and coupling grooves 522b may be formed on two sides of the second tapered square pipe 520b. An entirely ring-shaped structure can be achieved by alternately arranging the first tapered square pipe 510b and the second tapered square pipe 520b.

[0074] In the case of FIG. 5, the supporting force between the first tapered square pipe and the second tapered square pipe can be further improved than the case of FIG. 2.

[0075] Further, in the case of FIG. 4, since the coupling protrusion 411a is formed in a T-shape, the coupling protrusion 411a may be deformed or broken due to stress concentrating on the neck of the T-shape. On the other hand, in the case of FIG. 5, stress may concentrate on the short sides more than the long sides of the trapezoidal coupling protrusions 511a and the coupling area (jointing area) between the coupling protrusion 511a and the first tapered square pipe 510a is larger than that in the case of FIG. 4. Accordingly, the possibility of deformation or breakage of the coupling protrusion 511a is remarkably decreased, even though stress concentrates, as compared with the case of FIG. 4.

[0076] That is, there is the advantage in the case of FIG. 5 that the supporting force between the first tapered square pipe 510a and the second tapered square pipe 520a is further improved and there is little possibility of deformation or breakage of the coupling protrusions 511a.

[0077] Referring to FIG. 6, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may have another coupling structure. As shown in FIG. 6A, a coupling portion 611a of a first tapered square pipe 610a may be formed in a step-shaped cross-section and a coupling portion 621a of a second tapered square pipe 620a may be formed to correspond to the coupling portion 611a, thereby forming a coupling structure.

[0078] Further, as shown in FIG. 6B, a coupling portion 611b of a first tapered square pipe 610b may have a cross-sectional shape extending and bending once from a step shape and a coupling portion 621b of a second tapered square pipe 620b may be formed to correspond to the coupling portion 611b, thereby forming a coupling structure.

[0079] Further, as shown in FIG. 6C, a coupling portion 611c of a first tapered square pipe 610c may have a cross-sectional shape extending and bending twice from a step shape and a coupling portion 621c of a second tapered square pipe 620c may be formed to correspond to the coupling portion 611c, thereby forming a coupling structure.

[0080] FIG. 7 is a perspective view of a tapered square pipe included in the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention. FIG. 7 is a reference figure and the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes shown in FIG. 7 can be achieved by combining several tapered square pipes.

[0081] FIG. 8 is a plan view of a guide member according to an embodiment of the present invention and FIG. 9 is a view showing construction state using a guide member according to an embodiment of the present invention.

[0082] Referring to FIGS. 8 and 9, a guide member 900 according to an embodiment of the present invention may have: a fitting portion 910 that is fitted in the upper end of one of a plurality of tapered square pipes; and a guide portion 920 that horizontally extends from the fitting portion 910.

[0083] The fitting portion 910 may be formed in a rectangular pillar shape because a tapered square pipe is fitted therein.

[0084] Further, the guide portion 920 may include a tapered guide plate 921 decreasing in width toward the lower end from the upper end and a intake hole formed at the lower end of the guide plate.

[0085] In the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, it is required to continuously install a plurality of tapered square pipes (using a driving or boring method) using a crane, and particularly, coupling protrusions should be fitted in coupling grooves. However, it may not be easy for even skilled crane workers to accurately fit the coupling protrusion into the coupling grooves.

[0086] However, tapered square pipes are guided by the guide member 900 such that the lower ends of the tapered square pipes are easily coupled, so there is the advantage of easy installation.

[0087] Referring to FIG. 9, in detail, when a right tapered square pipe 720 is installed with a left tapered square pipe 710 installed, the right tapered square pipe 720 is installed with the fitting portion 910 of the guide member 900 fitted in the upper end of the left tapered square pipe 710, whereby installation becomes easy by the guide function of the guide member 720.

[0088] Further, the guide member 900 according to an embodiment of the present invention is easily detachably combined with a tapered square pipe, so even though tapered square pipes are continuously installed using a crane, one guide member 900 can be easily detachably used.

[0089] FIG. 10 is a view showing construction state using an anchor member according to an embodiment of the present invention. Referring to FIG. 10, the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may further include an anchor member 800 that is fitted in the lower end of one 730 of a plurality of tapered square pipes.

[0090] The anchor member 800 may have: a fitting portion 810 formed at the upper end of the anchor member to be fitted in the lower end of one 730 of a plurality of tapered square pipes; and an anchor portion 820 extending a predetermined length from the fitting portion 810 and decreasing in cross-sectional area toward the lower end.

[0091] Further, in the ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention, the tapered cross-sections of some of a plurality of tapered square pipes may be inclined at different angles, so the structure can be formed in an ellipse. Such an elliptical structure can be applied, if necessary, depending on the surrounding environments.

[0092] FIGS. 11 to 14 are flowcharts of a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention.

[0093] Referring to FIG. 11, a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may include: driving a first tapered square pipe having a coupling groove formed in the longitudinal direction on a side (S100); putting a second tapered square pipe having a coupling protrusion formed in the longitudinal direction on a side close to the upper end of the first tapered square pipe (S200); fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe (S300); and driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe (S400).

[0094] Referring to FIG. 12, a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may include, before the driving of the first tapered square pipe; welding respectively the first tapered square pipe and the second tapered square pipe (S50); driving a first tapered square pipe having a coupling groove formed in the longitudinal direction on a side (S100); putting a second tapered square pipe having a coupling protrusion formed in the longitudinal direction on a side close to the upper end of the first tapered square pipe (S200); fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe (S300); and driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe (S400).

[0095] In step S50, the first tapered square pipe and the second tapered square pipe may be respectively welded using four flat plates.

[0096] Referring to FIG. 13, a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may include: measuring the side pressure of the area where the first tapered square pipe and the second tapered square pipe are installed (S10); determining the thickness of the plates in accordance with the result of measuring the side pressure (S20); welding respectively the first tapered square pipe and the second tapered square pipe (S50); driving a first tapered square pipe having a coupling groove formed in the longitudinal direction on a side (S100); putting a second tapered square pipe having a coupling protrusion formed in the longitudinal direction on a side close to the upper end of the first tapered square pipe (S200); fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe (S300); and driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe (S400).

[0097] In step S20, when the measured side pressure is less than a predetermined value, as the result of measurement, the thickness of the plates can be determined as 10% or less of the entire width of the first tapered square pipe or the second tapered square pipe. However, when the measured side pressure is more than a predetermined value, as the result of measurement, the thickness of the plates can be determined as 11% or more of the entire width of the first tapered square pipe or the second tapered square pipe.

[0098] That is, since the method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention uses tapered square pipes, it is possible to adjust thickness, unlike circular steel pipes of the related art. Accordingly, it is possible to design and apply different thicknesses in accordance with surrounding side pressure.

[0099] Referring to FIG. 14, a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention may include coupling a guide member to the upper end of the first tapered square pipe (S150) after the driving of the first tapered square pipe.

[0100] When a method of constructing a ring-shaped cofferdam and temporary pit excavation structure using tapered square pipes according to an embodiment of the present invention includes step S150, the entire method may include: driving a first tapered square pipe having a coupling groove formed in the longitudinal direction on a side (S100); coupling a guide member to the upper end of the first tapered square pipe (S150); putting the second tapered square pipe to the upper end of the first tapered square pipe (S210); fitting the coupling protrusion of the second tapered square pipe into the coupling groove of the first tapered square pipe through the guide member (S310); driving the second tapered square pipe with the coupling protrusion of the second tapered square pipe fitted in the coupling groove of the first tapered square pipe (S410). This construction method guides tapered square pipes through the guide member 900 such that the lower ends of the tapered square pipes are easily coupled, so there is the advantage of easy installation.

[0101] While the technical spirit of the present invention was described in detail through embodiments, it should be noted that the embodiments is for describing, not limiting, the present invention. Further, it should be noted that the present invention may be achieved in various ways by those skilled in the art without departing from the scope of the present invention. Therefore, the technical protective region of the present invention should be determined by the scope described in claims.