KR101152265B1 - Prestressed bored pile construction method and structures - Google Patents

Abstract

The present invention relates to a method for constructing a cast-in-place concrete pile with prestress and its structure, and more particularly, to a tension member and a protective tube and a pile tip in the longitudinal direction of a pile when inserting a concrete reinforcing steel beam for a cast-in-place concrete pile construction. After inserting the fixing part in advance, and after the concrete placing and curing process, the tensile material is tensioned at the top of the pile to increase the tensile and flexural strength of the concrete pile structure by causing compressive stress over the entire length of the concrete pile. .

Description

Prestressed bored pile construction method and structures}

The present invention relates to a method for constructing a cast-in-place concrete pile and a structure thereof, in which prestress is introduced, and more specifically, in the longitudinal direction of the pile when the concrete reinforcement mesh is inserted for the construction of the cast-in-place concrete pile, After inserting the fixing unit in advance, and after the concrete placing and curing process, by tensioning the tension at the top of the pile to increase the tensile strength and flexural strength of the concrete pile structure by causing a compressive stress over the entire length of the concrete pile.

In addition, when the reinforcing bar is used, the perforated diameter of the cast-in-place concrete pile is increased due to the increase of the reinforcing bar, but when the high-strength strand is used, the increase of the additional perforation diameter is minimized and significant construction savings are achieved.

  In general, the pile foundation is used to transfer the load of the upper structure to the lower rigid layer when the upper layer is weak, in which case the compressive stress acts on the pile structure.

In addition, pile foundations are generally installed to resist lateral loads due to the bending stiffness of pile materials when lateral loads are applied to the structure. It will work at the same time.

Apart from the above cases, under special circumstances, i.e., when the ground is unstable, for example, when the expansion and contraction are repeated by changing the water content such as an expandable ground, or when swelling or hibbing occurs in the ground by excavation, When the structure is subjected to positive pressure due to the rise of the groundwater level, piles are sometimes installed to prevent the expected damage of the superstructure. In this case, the pile structure resists the swelling phenomenon of the ground or the upward force such as water pressure, and the tensile stress is increased. Will work.

On the other hand, the piles are divided into steel piles and concrete piles according to the material formed, and divided into ready-made piles and cast-in-place concrete piles according to the pile production method.

The disadvantage of steel piles in concrete piles is that they are relatively resistant to compression due to the characteristics of concrete, but they are only one tenth of their compressive strength.

Therefore, in the case of cast-in-place concrete piles, reinforcing reinforcing bars are generally installed before concrete in order to resist tensile stress or flexural stress in the structure.

On the other hand, in the case of ready-made concrete piles, a large amount of pile bodies are produced at the production site, not in the field, so when tensile stress or bending stress is expected to be applied to the structure, a prestressing is applied to the concrete piles to induce compressive stress. Thus, it is possible to use a method to increase the resistance to the bending stress expected to occur in the pile structure in the future (PC, PHC pile).

An example of a situation in which an existing cast-in-place concrete pile is subjected to tensile stress during the excavation of a temporary facility for constructing a superstructure foundation will be described with reference to FIG. 1.

As shown in FIG. 1, in the ground of the soft clay 1, a ground 2 is generated at the excavation bottom surface. In general, cast-in-place piles are pre-installed before excavation of temporary facilities to ensure the stability of excavation equipment and excavation walls. After excavation wall construction (excavation wall construction and pile construction is irrelevant, even if the construction order is changed) excavation of the inner ground of the temporary wall, the swelling phenomenon occurs in the lower ground of the excavation surface due to the release of stress, in severe cases excavation A moving phenomenon may occur due to the rotational activity moving inside the excavation.

As the above-mentioned soft ground in the lower excavated surface is displaced upward, frictional resistance is expressed in the direction to resist upward displacement in the contact surface between the pile and the ground, and the lower end of the pile is fixed to the rigid support layer. This is caused.

This upward force acts even more when the ground just below the excavation surface is a solid layer, when grouting is performed and when it is an existing structural slab.

The tensile stress during the excavation is a force acting on the pile temporarily, and the value of extinction due to the installation of the structure after completion of excavation and backfilling is prevented, or the unfavorable phenomenon of the pile such as excessive tensile stress during construction and the resulting concrete crack If additional rebar is used, the construction and material costs can increase significantly due to the use of materials that are not needed during public use.

The present invention has been made in consideration of the various problems as described above, and its purpose is to improve the tensile fracture and crack prevention and durability of the cast-in-place concrete piles, and to apply the pre-stressing to the cast-in-place concrete piles by using high-strength strands. The present invention provides a method and a structure for the construction of cast-in-place concrete piles using prestressing, which reduces material costs.

In order to achieve the above object, the present invention provides a temporary wall installation step of installing the temporary wall with the soft clay of the ground on which the structure is to be constructed; A drilling hole forming step of inserting a casing at the ground surface to drill the ground to form a drilling hole to the inside of the rock; Installing a plurality of reinforcing bar nets on the outer circumferential surface of the fixing plate formed in the upper side of the perforating hole, and inserting the reinforcing bar net and the tension member into the fixing plate through the fixing unit and inserting the reinforcing bar to the tip of the punching hole; A cast-in-place concrete pile forming step of pouring concrete into the perforated hole after inserting the reinforcing bar and the tension member to form a cast-in-place pile; A tension member tension step of installing a reaction force support on the ground surface after fixing the tension member, tensioning the hydraulic jet by the rear end of the tension member, and applying prestress to the cast-in-place concrete pile; After digging the tension member after the excavation of the ground to the top of the cast-in-place concrete pile after the excavation tensile force expression step to express the tensile force; consists of.

The present invention has various effects as follows.

First, it increases the tensile strength of cast-in-place concrete piles, and compressive stress is pre-applied to the concrete structure, thereby improving the tensile fracture and cracking of the concrete and improving durability.

Second, in the special case, that is, when the cast-in-place concrete pile receives both the pulling force and the bending stress at the same time, the concrete member can also resist the bending stress by prestressing, so that the resistance to the tensile stress of the cast-in-place concrete pile can be effectively increased. .

Thirdly, when a large tensile force is generated, the amount of reinforcing bars entering a large amount is increased to prevent tensile failure of the cast-in-place concrete pile and cracking of concrete materials. In this case, prestressing is performed using high-strength stranded wire, thereby reducing the construction cost and material cost.

1 is a cross-sectional view showing a state of use of the conventional cast-in-place pile
Figure 2 is a process chart showing the construction sequence of the cast-in-place concrete piles introduced the prestress of the present invention
3 is a cross-sectional view showing the overall configuration of the present invention.
4 is a cross-sectional view showing an installation state of the temporary wall of the present invention.
Figure 5 is a cross-sectional view showing the ground perforation state of the present invention
6a to 6b are sectional views showing the installation state of the reinforcing bar and the tension member of the present invention
7A to 7C are cross-sectional views illustrating a state where the stranded wire is coupled to the tip pressure plate of the present invention;
Figure 8 is a cross-sectional view showing a coupling state of the stranded wire connected to the loading body of the present invention
9 is a cross-sectional view showing that the inventor's body is formed in multiple stages
10 is a cross-sectional view showing the configuration of the fixing unit of the present invention.
11 to 12 are sectional views showing another configuration of the fixing unit of the present invention.
Figure 13 is a cross-sectional view showing the forming step of the cast-in-place concrete pile of the present invention
14a to 16b are sectional views showing the operating state of the present invention anchorage
17A to 17B are cross-sectional views showing a state in which the stranded wire of the present invention is removed.

Hereinafter, described in detail by the accompanying drawings for carrying out the present invention in detail.

2 is a flowchart illustrating a method of constructing a cast-in-place concrete pile incorporating the prestress of the present invention, and FIG. 3 is a cross-sectional view showing the overall configuration of the present invention.

The present invention comprises a temporary wall installation step, a hole forming step, the reinforcing bar and the tension member insertion step, the cast-in-place concrete pile forming step, the tension member tension step, the excavation of the tension material after the excavation step.

The temporary wall installation step,

As shown in FIG. 4, the temporary wall 10 is installed using a slurry wall, SCW, H pile pile or steel pipe sheet pile as soft clay ground of the site where the structure is to be constructed.

The drilling hole forming step,

After grouting the soft clay ground to improve the ground, as shown in FIG. 5, the casing 9 is mounted on the perforator, and the perforated ground is formed by rotating the casing 9 to form the perforation hole 30.

At this time, the tip of the drilling hole 30 is drilled to be formed to the rock 40 formed in the ground.

The temporary wall installation step and the drilling hole forming step may be executed in a different order depending on the work site and environment.

Inserting the reinforcing bar and the tension member,

As shown in FIG. 6A attached to the inside of the drilling hole 30, the circular fixing plate 70 to which a plurality of rebar meshes 50 are connected is fastened to the upper side of the reinforcing steel mesh 50, and the fixing plate ( Inside the 70, a plurality of tension members 60 are combined.

At this time, the lower side of the tension member 60 is removed by the protective tube 62 is inserted into the drilling hole 30 in a state that the strand wire 61 is exposed to the outside.

This is a way to ensure that the concrete is directly attached to the steel wire (61) when the concrete is poured into the drilling hole (30).

 And the end of the reinforcing reinforcing bar 50 is inserted to the front end of the drilling hole 30, the rear end of the tension member 60 to be discharged to the ground surface.

The tension member 60 is used by fastening the protective tube 62 made of a synthetic resin material to the outer surface of the stranded wire 61 and the stranded wire 61 formed by twisting the strands of one strand and the strands of 6 strands on the outer surface at the center thereof.

In addition, the attached strand as shown in Figure 6b is installed in one or more bundles, it can be used to install a variety of places, such as three to eight places.

In addition, as shown in Figure 6c of the accompanying drawings, the tip of the reinforcing bar 50 and the tension member 60 may be provided with a tip acupressure plate 85 formed of a plurality of insertion holes (85a) consisting of a circular plate and a square plate .

At this time, the strand wire 61 discharged to the outside of the tip acupressure plate 85 is fastened by fastening with a crimping grip 90 having a screw thread 91 formed therein as shown in FIG. 7A, or attached to FIG. 7B. As shown in the fastening the wedge 92 by the strand 61 is fixed.

In addition, as shown in FIG. 7C of the accompanying drawings, the strand 61 may be fastened by being fastened to the U shape 93.

This method can be used not only in the excavation work of the ground but also in the existing slab floor.

As described above, another method of fixing the tip of the tension member is as shown in FIG. 8, instead of using a single large circular pressure plate as shown in FIG. 8. The stranded wire 61 discharged to the tip may be fastened using a crimping grip 101 having a thread formed on the inner surface thereof, or the wedge 102 may be fastened, and the stranded wire 61 may be fastened in a U-shape 103. Can also be used.

The location of the load bearing body 100 may be installed and used at the tip, middle, or any other position of the strand 61.

And attached to the drawing as shown in Figure 9 is used to fasten the lower body 100 in multiple stages, the method of fixing the lower body 100 and the tension member 60 as described above in the crimping grip 101 In or wedge 102 and U-shaped (103) is used to fasten.

As described above, the lower ends of the reinforcing steel mesh 50 and the tension member 60 are fixed using the tip pressure plate 85 or the lower body 100.

And when fixing the strand wire 61 with the upper fixing plate 70 is fastened to the reinforcing reinforcing bar 50 and the tension member 60 is fixed using a separate anchorage (120).

The fixing unit 120 is formed to pass through the wedge insertion hole 132 having an inclined surface so that a plurality of wedges 131 is mounted, as shown in Figure 10 of the accompanying drawings, the bottom of the wedge insertion hole 132 of the tension member The protective tube fixing wedge 133 holding the protective tube is fastened to form a fixing head 130 consisting of a circular plate having a plurality of bolt holes 134.

The wedge fixing plate 135 is fixed to the lower side of the fixing head 130 by using the fixing bolt 136.

The wedge 131 into which the strand 61 is inserted into the wedge insertion hole 132 of the fixing head 130 is installed. At this time, the strand 61 is only a portion inserted into the wedge 131, there is no protective tube 62, the protective tube 62 is in a state that is fastened.

Then, a plurality of protective tube fixing wedges 141 are fastened to the upper surface of the fixing head 130 and a plurality of bolt holes 142 are formed on the outer surface, and the fixing plate 140 having a predetermined space 143 on the inner surface thereof. Form.

The wedge fixing plate 144 is fastened to the upper surface of the fixing plate 140 by fixing bolts 145 to fix the wedge fixing plate 144.

And the front end of the fixing bolt 145 is inserted into the bolt hole 134 of the fixing head 130 so that the fixing plate 140 is fixed to the fixing head 130.

At this time, the watertight rubber O-ring 149 is fastened between the fixing plate 140 and the fixing head 130 to block external moisture from entering the fixing unit 120.

Another embodiment of the fixing unit 120 is elastic between the upper surface of the wedge 131 fastened to the fixing head 130 and the protective tube fixing wedge 141 of the fixing plate 140 as shown in the accompanying drawings, FIG. The spring 150 is mounted and used.

In addition, as shown in FIG. 12, the hydraulic cylinder 160 is used to be coupled between the wedge 131 and the protective tube fixing wedge 141 instead of the elastic spring 150.

A fixing hole 120 is mounted on the upper side of the reinforcing steel mesh 50 and the tension member 60, and the perforated hole 30 is installed at the distal end of the reinforcing steel mesh 50 and the tension member 60. )

The cast-in-place concrete pile forming step,

13, the anchoring rod 120 is mounted on the upper side of the reinforcing steel mesh 50 and the tension member 60, and the tip acupressure plate 85 is disposed at the front end of the reinforcing steel mesh 50 and the tension member 60. As shown in FIG. After inserting into the drilling hole 30 in the installed state, the concrete 170 is poured into the interior of the drilling hole 30 and cured for a predetermined period of time to form a cast-in-place concrete pile.

At this time, the protective tube 62 is fastened to the outer surface of the tension member 60, so that the crimping grip 101 or the wedge 102 installed on the anchorage plate 120, the reinforcing steel mesh 50, and the tip pressure plate 85 of the tension member 60 is provided. Through the U-shaped 103 and to block the concrete flowing into the tension member (60).

The tension member tension step,

After the cast-in-place concrete pile 200 is completed, the reaction force support 180 is installed on the ground surface as shown in FIG. 3 and the hydraulic line 181 is coupled to the rear end of the tension member 60, thereby adding the stranded wire 61. ) Will be tensioned.

At this time, since the entire strand (61) is covered with a protective tube 62, the tensile force applied from the ground surface is transmitted to the cast-in-place concrete pile 200, the prestress (compression force) is applied.

As a result, even in the external environment of the underground soft clay, the cast-in-place concrete pile 200 does not generate cracks or fractures, thereby maintaining a safe construction state.

In addition, the tensile wire 61 is fastened to the wedge 131 of the fixing head 130 at the time of tension as shown in Figure 14a attached to the predetermined space 143 formed inside the fixing plate 140 while moving upward To enter.

This is because the wedge 131 is up from the wedge insertion hole 132 and does not restrain the strand 61, the strand 61 continues to increase until the target load is reached.

As such, when the stranded wire 61 is tensioned to reach the target load, when the field load is removed from the ground surface, the wedge 131 of the fixing head 130 moves downward as shown in FIG. 14B. While being completely inserted into the wedge insertion hole 132 to restrain the strand 61.

Another embodiment of the anchorage 120 is shown in the accompanying drawings, Figure 15a and 15b when the tension line 61 is tensioned using a hydraulic jet installed on the rear end of the tension member 60 from the ground surface, the fixing head 130 As the strand wire 61 is fastened to the wedge 131 of the) moves upward, the elastic spring 150 is elastically retracted, and at the same time enters a predetermined space 141 formed in the fixing plate 140.

This is because the wedge 131 is up from the wedge insertion hole 132 and does not restrain the strand 61, the strand 61 continues to increase until the target load is reached.

As such, when the stranded wire 61 is tensioned to reach the target load, when the field load is removed from the ground surface, the compressed elastic spring 150 recovers elasticity and at the same time, the wedge 131 of the fixing head 130. ) Is completely inserted into the wedge insertion hole 132 while moving downward to restrain the strand 61.

In addition, another embodiment of the fixing unit 120 is when the tension line 61 is tensioned by using a hydraulic jet installed on the rear end of the tension member 60, as shown in the accompanying drawings Figures 16a and 16b, As the stranded wire 61 fastened to the wedge 131 of the fixing head 130 moves upwards, pressure is applied to the hydraulic cylinder 160 installed in a predetermined space 143 of the fixing plate 140 so that the cylinder is upward. While moving to raise the wedge 131.

At this time, the wedge 131 is in a state where it rises upward from the wedge insertion hole 132 and thus cannot restrain the strand 61, and the strand 61 continues to increase until the target load is reached.

As such, when the stranded wire 61 is tensioned to reach the target load, when the length is removed from the ground surface, the wedge 131 moves downward while the applied pressure of the hydraulic cylinder 160 is discharged to the outside. It is completely inserted into the insertion hole 132 to restrain the strand 61.

Tensile force expression step after the excavation,

After the tension is completed, the ground is excavated to the upper end of the cast-in-place concrete pile to apply the tensile force to the tensile material is expressed.

In the present invention as described above, when the load of the structure installed on the ground surface is large, a large compressive force may be applied to the pile after the completion of construction, so compressive fracture of the pile may occur, so that the strand removal step is required to remove the prestressing applied to the pile before the completion of the structure. Done.

The strand removal step is a removal hole 191 is formed on the lower side of the outer peripheral surface to the lower side of the fixing unit 120 for holding the tension member 60 as shown in the accompanying drawings 17a and 17b is inserted into the tension member 60 on the upper surface A cylindrical pedestal 190 having a hole 192 is fastened.

Then, the load introduced to the strand 61 of the tension member 60 is removed using the oxygen cutter 195 through the removal hole 191 of the pedestal 190.

  Then, after cutting the strand 61, the fixing unit 120 and the pedestal 190 are removed, and if the lower fixing method of the cast-in-place concrete pile is a U method, the heavy steel is removed using a heavy machinery such as a crane. By removing the strands 61 to remove the strands 61 that can remain in the cast-in-place concrete piles on the ground.

In addition, the present invention can be ground improvement work to increase the strength of the soft ground by applying and curing the grout liquid to the bottom of the final excavation surface after installing the temporary wall (10).

In this case, J.S.P (Jumbo Special Pattern), Jet grouting, LW (Labiles Water glass grouting), JCM (Just Selected Chemical Grouting Method), SGR (Space Grouting Rocket System), etc.

Referring to the configuration of the cast-in-place concrete pile of the present invention as follows.

As shown in FIG. 8, a plurality of rebar meshes 50 are installed on the outer circumferential surface of the upper fixing plate 70, and a bundle of tension members 60 is provided in the inner body 100 of the reinforcing steel mesh 50. And after fixed installation through the anchorage 120 will be concrete can be added to the tension member 60 after completing the cast-in-place concrete pile.

The load-bearing body 100 may be installed at either the tip or the middle portion of the strand.

In addition, the pressure bearing plate 85 may be used instead of the load bearing body 100 at the tip and other positions of the reinforcing steel mesh 50 and the tension member 60.

30: hole 40: bedrock
50: reinforcing steel bar 60: tensile material
61: strand 62: protective tube
70: fixed plate 85: tip acupressure plate
90,101: crimping grip 91,102: wet
93,103: U shape 100: Lower body
110: upper fixing plate 120: fixing hole
130: fixing head 140: fixing plate
150: elastic spring 160: hydraulic cylinder
170: concrete 180: reaction support
190: pedestal 200: cast-in-place concrete pile

Claims (13)

A temporary wall installation step of installing a temporary wall with soft clay of the ground on which the structure is to be constructed;
A drilling hole forming step of inserting a casing at the ground surface to drill the ground to form a drilling hole to the inside of the rock;
Installing a plurality of reinforcing bar nets on the outer circumferential surface of the fixing plate formed in the upper side of the perforating hole, and inserting the reinforcing bar net and the tension member into the fixing plate through the fixing unit and inserting the reinforcing bar to the tip of the punching hole;
A cast-in-place concrete pile forming step of pouring concrete into the perforated hole after inserting the reinforcing bar and the tension member to form a cast-in-place pile;
A tension member tension step of installing a reaction force support on the ground surface after fixing the tension member, tensioning the hydraulic jet by the rear end of the tension member, and applying prestress to the cast-in-place concrete pile;
Pre-stretching tensile strength step of excavation so that the tensile force is expressed after excavating the ground to the top of the site-cast concrete pile after tensioning the tension member;
The method of claim 1,
Pre-stressed on-site concrete pile construction method comprising the use of installing a circular tip acupressure plate to the tip of the reinforcing bar and the tension member.
The method of claim 1,
On-site casting with pre-stressing in which the protection pipe of the lower part of the tension member is inserted into the perforated hole so that the strand is inserted in the exposed state to the outside so that the concrete is directly attached to the strand when the concrete is poured into the perforated hole. Concrete pile construction method.
The method of claim 2,
Pre-stressed cast-in-place concrete pile construction method comprising the installation in the form of a pressing grip or wedge and U-shaped to hold the tension member to the front of the tip plate.
The method of claim 2,
The method of constructing concrete piles incorporating prestressing, comprising fastening a load bearing body to the tip of a tension member instead of the tip pressure plate, and fastening the load body and the tension member in a crimping grip, wedge or U-shape.
The method of claim 5,
Pre-stressed cast-in-place concrete pile construction method comprising the step of distributing the load by installing the load-bearing body in multiple stages.
The method of claim 1,
The fixing unit,
A fixing head which is formed to penetrate the wedge insertion hole in which a plurality of wedges are mounted, and a fixing tube fixing wedge is fastened to a lower side thereof, and a wedge fixing plate is fixed to a lower side by a fixing bolt;
A wedge inserted into the wedge insertion hole and having a strand connected to a protective tube on an outer circumferential surface thereof;
A fixing plate coupled to the upper surface of the fixing head and having a plurality of protection tube fixing wedges fastened thereon and fixing the wedge fixing plate to the upper surface and fixing the fixing head using the fixing bolts;
Precast stress-injected concrete pile construction method, characterized in that the fastening head and the fixing plate is in contact with the waterproof O-ring made by fastening.
The method of claim 7, wherein
Pre-stressed cast-in-place concrete pile construction method characterized in that the elastic spring is mounted between the upper surface of the wedge and the fixing tube fixed wedge of the fixing plate.
The method of claim 7, wherein
Method for constructing a site-in-place concrete pile introduced with prestress, characterized in that the use of the hydraulic cylinder is fastened instead of the elastic spring fastened between the wedge and the protective tube fixed wedge.
The method of claim 1,
The removal hole is formed on the outer circumferential surface of the lower side of the anchorage, and the cylindrical pedestal having a hole into which the tension member is inserted in the upper surface is installed, and the strand wire removing step of removing the strand wire using an oxygen cutter as the elimination hole of the pedestal includes: Construction method of cast-in-place concrete piles using prestress.
The method of claim 1,
After the installation of the temporary wall is applied to the grout liquid to the bottom of the final excavation surface curing step by introducing a pre-stress, characterized in that the ground improvement step to increase the strength of the soft ground.
A plurality of rebar networks are installed on the outer circumferential surface of the upper fixing plate, and after the bundle of tension members are fixedly installed through the undercarriage and the anchorage in the inside of the reinforcing steel mesh, the concrete is poured to complete the cast-in-place concrete pile, and then the tension is performed with the tension members. Cast-in-place concrete pile structure with prestress that can be applied.
The method of claim 12,
Pre-stressed cast-in-place concrete pile structure characterized in that it comprises the fixing of the tension member by using a single pressure plate to the tip of the tension member.

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