JP2012219533A - Test pile construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test pile construction method capable of reliably providing a test pile with friction cutting.SOLUTION: A test pile construction method constructs a test pile 1 which comprises: an outer pipe 10; an inner pipe 20 installed inside the outer pipe 10; and a test pile main body 30 which is a cast-in-place reinforced concrete pile constructed inside the inner pipe 20. A borehole 40 is constructed by excavating the ground. An integral unit 50 is assembled by integrating the outer pipe 10, the inner pipe 20, and a reinforcement cage 31 to be embedded in the test pile main body 30. The integral unit 50 is inserted into the borehole 40 to a depth deeper than a predetermined depth. Then, the test pile main body 30 is constructed by placing concrete inside the borehole 40 up to the depth deeper than the predetermined depth.

Description

  The present invention relates to a test pile construction method.

Conventionally, when a pile is constructed as a foundation of a structure, a test pile is constructed in order to confirm the allowable bearing capacity of the pile (see Patent Document 1).
That is, a test pile is constructed from the ground surface to the supporting ground, and a reaction force pile is constructed around the test pile. And using a reaction force apparatus, it applies force to a test pile, taking reaction force to a reaction force pile. At this time, depending on the purpose of the test, a friction cut is performed to remove the peripheral frictional resistance of the outer peripheral portion of the pile from the ground surface to a predetermined depth (for example, to the depth of the planned underground skeleton).

Specifically, the test pile is constructed by the following procedure.
First, a hole is formed by drilling while injecting a stabilizing liquid for protecting the hole wall on the ground surface. Next, the outer tube, the inner tube, and the reinforcing bar cage are inserted in this hole in this order, and concrete is placed inside the inner tube while collecting the stabilizing liquid. As a result, a reinforced concrete test pile is constructed inside the inner pipe. At this time, by preventing the concrete from entering the gap between the outer tube and the inner tube, friction does not act on the outer peripheral surface of the inner tube, so that friction cutting is performed.

JP 2011-17227 A

  By the way, when constructing the underground structure of the structure, it is necessary to remove the part of the test pile and the reaction force pile that interferes with the underground structure during excavation after applying the test to the test pile and testing. Therefore, there is a problem that the construction cost becomes high and noise and vibration accompanying dismantling are generated, so that a load is applied to the surrounding environment.

  Therefore, it is conceivable to construct test piles and reaction force piles only on the ground surface deeper than the floor surface level. If it does in this way, since it is not necessary to dismantle a test pile and a reaction force pile at the time of excavation to a floor surface, not only construction cost can be reduced but also noise and vibration can be reduced.

  However, in this case, since the upper ends of the outer tube and the inner tube are not exposed to the ground surface, the relative position of the inner tube with respect to the outer tube cannot be visually confirmed, and it is difficult to ensure accuracy. Moreover, there is a possibility that concrete enters the gap between the outer pipe and the inner pipe, and the test pile cannot be friction-cut.

  An object of this invention is to provide the test pile construction method which can perform a friction cut reliably to a test pile.

  The test pile construction method according to claim 1 includes an outer pipe, an inner pipe provided inside the outer pipe, a test pile main body that is a cast-in-place pile made of reinforced concrete built inside the inner pipe, A test pile construction method for constructing a test pile comprising: forming a hole by drilling a hole in the ground, and integrating and integrating the outer tube, the inner tube, and the reinforcing bar cage embedded in the test pile body An integrated unit is assembled, the integrated unit is inserted into the hole up to a predetermined depth, and concrete is placed inside the inner pipe to construct the test pile main body.

  According to this invention, the outer tube and the inner tube are integrated to fix the relative position of the inner tube with respect to the outer tube, and further, the upper end and the lower end of the gap between the outer tube and the inner tube are closed, and in this state the predetermined hole is defined. Since it is inserted deeper than the depth, it is possible to prevent the concrete from entering the gap between the outer pipe and the inner pipe, so that the test pile can be reliably subjected to friction cut.

  The test pile construction method according to claim 2, wherein when assembling the integrated unit, a first closing member for closing a gap between the outer tube and the inner tube is provided on a proximal end side of the outer tube. And

When concrete is placed inside the inner pipe, the concrete may overflow from the proximal end side of the inner pipe and enter the gap between the outer pipe and the inner pipe from the upper end side.
However, according to the present invention, since the base end side of the gap between the outer pipe and the inner pipe is closed by the first closing member, even if the concrete overflows from the upper end side of the inner pipe when the concrete is placed, the concrete is not removed. It is possible to prevent the gap between the pipe and the inner pipe from entering from the upper end side.

  The test pile construction method according to claim 3, wherein when assembling the integrated unit, a second closing member that closes a gap between the outer tube and the inner tube is provided on a distal end side of the outer tube. To do.

When the integrated unit is inserted into the hole and concrete is placed inside the inner pipe using the tremy pipe, the concrete may enter the gap between the outer pipe and the inner pipe from the lower end side.
However, according to the present invention, since the leading end side of the gap between the outer tube and the inner tube is closed by the second closing member, the concrete enters the gap between the outer tube and the inner tube from the lower end side when placing concrete. Can be prevented.

  Further, since the width of the gap between the outer tube and the inner tube is kept constant by the second closing member, it is possible to prevent the relative position of the inner tube with respect to the outer tube from shifting.

  In the test pile construction method according to claim 4, when assembling the integrated unit, a strain gauge is attached to the rebar cage, a signal line of the strain gauge is taken out from the proximal end side of the inner tube, and covered with a cover. It is characterized by keeping.

Here, the cover is formed of a high-strength material such as metal.
It is necessary to take out the signal line of the strain gauge from the proximal end side of the inner pipe when performing the indentation test of the test pile, but the signal line is caught by heavy excavator when excavating to construct the underground frame. There is a risk of disconnection.
Therefore, according to the present invention, since the signal line of the strain gauge is taken out from the proximal end side of the inner tube and covered with a metal cover, it is possible to prevent the signal line from being caught by a heavy excavator and disconnected.

  According to the present invention, the outer tube and the inner tube are integrated to fix the relative position of the inner tube with respect to the outer tube, and the upper end and the lower end of the gap between the outer tube and the inner tube are closed, and in this state the hole has a predetermined depth. Since it is inserted deeper, it is possible to prevent the concrete from entering the gap between the outer pipe and the inner pipe, so that the test pile can be reliably subjected to friction cut.

It is sectional drawing of the test pile constructed | assembled by the test pile construction method which concerns on one Embodiment of this invention. It is sectional drawing of the base end side of the test pile which concerns on the said embodiment. It is sectional drawing of the front end side of the test pile which concerns on the said embodiment. It is FIG. (1) for demonstrating the procedure which builds the test pile which concerns on the said embodiment. It is FIG. (2) for demonstrating the procedure which builds the test pile which concerns on the said embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a test pile 1 constructed by a test pile construction method according to an embodiment of the present invention.
The test pile 1 is constructed deeper than a predetermined depth of the hole 40, and includes a cylindrical steel outer tube 10 and a cylindrical steel inner tube 20 provided inside the outer tube 10. And a test pile main body 30 which is a cast-in-place pile made of reinforced concrete built inside the inner pipe 20.

  The inner tube 20 extends upward and downward from the outer tube 10. In addition, spacer members 14 are provided on the outer peripheral surface of the inner tube 20 at predetermined intervals, and the width of the gap between the outer surface of the inner tube 20 and the inner surface of the outer tube 10 is substantially constant.

The test pile main body 30 extends upward and downward from the inner tube 20.
A reinforcing steel basket 31 is embedded in the test pile main body 30. The reinforcing bar 31 includes a plurality of pile main bars 311 extending in the axial direction and hoop bars 312 provided to surround the pile main bars 311.
The hoop bars 312 are annular, and the pile main bars 311 are arranged at predetermined intervals along the inner peripheral surface of the hoop bars 312.

A strain gauge 32 that measures the amount of compression when force is applied to the test pile 1 is attached to the reinforcing bar 31.
Specifically, here, the strain gauge 32 is fixed to the hoop muscle 312 with two cross sections on the distal end side and one cross section on the proximal end side of the test pile main body 30.

FIG. 2 is a cross-sectional view of the base end side of the test pile 1.
A first closing member 11 that closes the gap between the outer tube 10 and the inner tube 20 is provided on the proximal end side of the outer tube 10.
The first closing member 11 is an annular member attached along the outer periphery of the outer tube 10.

Further, a metal cover 21 that is a channel material is provided on the outer peripheral surface on the proximal end side of the inner tube 20, and a through hole 201 that communicates with the inside of the cover 21 is formed in the inner tube 20. ing. The cover 21 is covered with a hard sponge 22.
The signal line 321 of the strain gauge 32 extends to the proximal end side along the pile main bar 311, extends through the inner tube 20 to the inside of the cover 21, and is accommodated in the cover 21.

  A suspension piece 13 for lifting with a crane is welded to the outer peripheral surface of the outer tube 10 on the proximal end side.

FIG. 3 is a cross-sectional view of the front end side of the test pile 1.
A second closing member 12 that closes the gap between the outer tube 10 and the inner tube 20 is provided on the distal end side of the outer tube 10.
The second closing member 12 includes an annular hard sponge 121 and an annular slip prevention angle 122 that is attached along the outer periphery of the inner tube 20 and is locked by the hard sponge 121.

The hard sponge 121 is a material that allows a fluid with a small particle size of an inclusion such as a stable liquid mixed with a polymer to pass therethrough but hardly allows a liquid with a large particle size of an inclusion such as concrete to pass through.
The thickness of the hard sponge 121 is substantially constant, so that the gap between the outer tube 10 and the inner tube 20 is closed and the width of the gap is kept constant.

Hereinafter, the procedure for constructing the test pile 1 will be described with reference to FIGS. 4 and 5.
First, as shown in FIG. 4A, the surface layer casing 41 is built while drilling holes in the ground, and the holes 40 are formed by further drilling holes after the surface layer casing 41 is built. On the upper end side of the hole 40, the hole 40 is filled with a stabilizing liquid in which a polymer is blended.

  Next, the outer tube 10 and the inner tube 20 are assembled together, the relative position of the inner tube 20 with respect to the outer tube 10 is fixed, and the first blocking member 11 and the second blocking member 12 are attached. Then, as shown in FIG. 4 (b), the integrated outer tube 10 and inner tube 20 are lifted with a crane and inserted into the hole 40, and arranged on the upper end side of the hole 40.

  Next, the rebar cage 31 is assembled at the rebar cage assembly yard, and the strain gauge 32 is attached. Then, as shown in FIG. 4 (c), the reinforcing bar 31 is lifted by a crane and inserted into the hole 40 and placed inside the inner pipe 20. In this state, the signal line 321 is placed inside the cover 21. Store. Thereby, the integrated unit 50 which consists of the outer tube 10, the inner tube 20, and the reinforcing bar 31 is completed.

  Next, as shown in FIG. 5A, the integrated unit 50 is lowered to a predetermined depth or more by a crane using the suspension piece 13 of the outer tube 10. Thereby, it is possible to prevent the concrete from entering the gap between the outer tube 10 and the inner tube 20.

Next, as shown in FIG. 5 (b), the treme tube 42 is inserted into the hole 40, and the stable liquid is recovered while pouring the concrete into the inner tube 20 through the treme tube.
At this time, concrete tries to enter from the lower end side of the gap between the outer tube 10 and the inner tube 20, but the hard sponge 121 prevents the concrete from entering. Even if the hard sponge 121 is pressed by the pressure of the concrete, it is possible to prevent the hard sponge 121 from being displaced by the slip prevention angle 122.

And as shown in FIG.5 (c), concrete is cast to a predetermined depth level and the test pile main body 30 is constructed | assembled.
At this time, the concrete is placed to a position slightly higher than the predetermined depth as an extra portion. As a result, the concrete overflows from the inner tube 20, but the first blocking member 11 prevents the overflowed concrete from entering from the upper end side of the gap between the outer tube 10 and the inner tube 20.
Next, the surface casing 41 is pulled out and the hole 40 is backfilled with earth and sand.

In addition, a reaction force pile is constructed around the test pile 1.
After that, excavation with heavy equipment is performed to construct the underground frame. Even if the excavation heavy equipment comes into contact with the base end side of the test pile 1 or the concrete surplus is removed after excavation, the signal from the strain gauge 32 The wire 321 is protected by the hard sponge 22 and the cover 21.

According to this embodiment, there are the following effects.
(1) The outer tube 10 and the inner tube 20 are integrated, the relative position of the inner tube 20 with respect to the outer tube 10 is fixed, and in this state, the outer tube 10 and the inner tube are inserted deeper than the predetermined depth of the hole 40. Since it is possible to prevent the concrete from entering the gap between the test pile 1 and the test pile 1, the friction cut can be reliably performed.

  (2) Since the upper end side of the gap between the outer pipe 10 and the inner pipe 20 is closed by the first closing member 11, even if the concrete overflows from the proximal end side of the inner pipe 20 when placing concrete, the concrete is It is possible to prevent the gap between 10 and the inner tube 20 from entering from the upper end side.

(3) Since the lower end side of the gap between the outer tube 10 and the inner tube 20 is closed by the second closing member 12, the concrete enters the gap between the outer tube 10 and the inner tube 20 from the lower end side when placing concrete. Can be prevented.
Further, since the width of the gap between the outer tube 10 and the inner tube 20 is kept constant by the second closing member 12 and the spacer member 14, it is possible to prevent the relative position of the inner tube 20 with respect to the outer tube 10 from shifting.

  (4) Since the signal line 321 of the strain gauge 32 is taken out from the proximal end side of the inner tube 20 and covered with the metal cover 21, it is possible to prevent the signal line 321 from being caught by a heavy excavator.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Test pile 10 ... Outer pipe 11 ... 1st closing member 12 ... 2nd closing member 13 ... Hanging piece 14 ... Spacer member 20 ... Inner tube 21 ... Cover 22 ... Hard sponge 30 ... Test pile main body 31 ... Reinforcing bar 32 ... Strain meter 40 ... Hole 41 ... Surface casing 42 ... Tremy tube 50 ... Integral unit 121 ... Hard sponge 122 ... Angle 201 ... Through hole 311 ... Pile main bar 312 ... Hoop bar 321 ... Signal wire

Claims (4)

A test pile construction method for constructing a test pile comprising an outer pipe, an inner pipe provided inside the outer pipe, and a test pile body that is a cast-in-place pile made of reinforced concrete built inside the inner pipe Because
Drill holes in the ground to form holes,
Assembling an integrated unit by integrating the outer pipe, the inner pipe, and the reinforcing steel basket embedded in the test pile main body,
Insert the integrated unit into the hole up to a predetermined depth,
A test pile construction method comprising placing concrete inside the inner pipe to construct the test pile body.   2. The test pile construction method according to claim 1, wherein when the integrated unit is assembled, a first closing member that closes a gap between the outer tube and the inner tube is provided on a proximal end side of the outer tube. .   3. The test pile construction according to claim 1, wherein when the integrated unit is assembled, a second closing member that closes a gap between the outer tube and the inner tube is provided on a distal end side of the outer tube. Method.   4. When assembling the integrated unit, a strain gauge is attached to the rebar cage, a signal line of the strain gauge is taken out from a proximal end side of the inner tube, and covered with a cover. The test pile construction method in any one of.

Images