JP4596930B2 - Pile for medium digging - Google Patents

Description

  The present invention relates to a pile body for an underground digging consolidation method having a recessed groove portion on a lower outer peripheral surface.

  The conventional digging root-setting method uses a screw auger inserted into the hollow part of the pile body and installed at the tip of the screw auger when a ready-made concrete pile (hereinafter simply referred to as “pile body”) is submerged on the ground. The bit with a special structure that can be expanded and contracted is projected from the tip of the pile body, and the excavated soil is removed from the pile body by a screw auger while excavating the direct foundation board at the tip of the pile with the bit that is halfway open to the intermediate diameter. It is transferred to the upper part of the pile through the hollow part, and the pile body is sunk while removing the soil from the upper end opening of the pile.

  Then, after digging to the vicinity of the support layer, the bit is opened to an enlarged diameter, and excavating while injecting root hardening liquid such as mortar discharged from the discharge port at the tip through the passage in the shaft of the screw auger into the drilling soil Then, the lower part of the pile body is inserted into the support layer, and only the bit in the open state is dug to provide a bulb forming hole.

  After that, when the bit and screw auger with the blade closed to the minimum diameter are taken out from the hollow part of the pile body and the root-solidifying liquid in the bulb formation hole is solidified, the bulb-shaped root-solidified part extends from the vicinity of the support layer to the tip of the pile. It can be built (see, for example, Patent Documents 1 and 2).

Here, a structure capable of withstanding the axial shear force is required between the lower part of the pile body and the root-solidified part.For this purpose, a protrusion is provided on the lower outer peripheral surface of the pile body, and a vertical load is applied to the pile body. Concrete piles are embedded so that the shearing force propagates from the lower surface of the projection to the support layer in a conical shape within the root consolidation part, and forms a support surface on the support layer at the conical bottom surface of the root consolidation part. There is a method (for example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 11-2085 (page 7-8, FIG. 7-11) JP-A-11-280066 (second page, FIG. 6) Japanese Patent No. 3531099 (page 3-4, Fig. 1-2)

  Although the pile body which has a protrusion in the lower outer peripheral surface described in Patent Document 3 has the advantage of greatly increasing the vertical load that can be borne by a single pile body, the digging root described in Patent Documents 1 and 2 There is a problem that cannot be applied to the hardening method.

  The present invention has been made in view of such a point, and when a vertical load is applied, the structure is capable of effectively transmitting a shearing force to a support layer through a rooting portion. The purpose is to provide a pile.

The invention according to claim 1 is a pile main body made of cylindrical concrete, and a plurality of concave groove portions having a groove bottom portion having a diameter smaller than the outer diameter of the pile main body provided on the outer peripheral surface of the support layer insertion portion of the pile main body. These concave groove portions have tapered portions at the corners, and all the number according to the pile diameter is within the range of the length equal to the pile diameter from the tip of the pile rooted in the support layer. It is a pile body for the underground digging consolidation method in which all the recessed groove portions are provided in the same shape and size, and the number is increased or decreased according to the pile diameter , and when the vertical load is applied to the pile body In addition, it is possible to effectively transmit the shearing force to the support layer through the root consolidation portion integrated through the recessed groove portion provided on the outer peripheral surface of the support layer rooting portion of the pile body. In addition, the concave groove portion has a tapered portion at the corner portion, so that when the pile is inserted, earth and sand adhering to the corner portion of the concave groove portion is reduced, and resistance acting on the corner portion of the concave groove portion from the underground obstacle is small. It becomes difficult to break the concave groove part, and furthermore, by providing a taper part, the bearing area during pile installation can be increased, so it is possible to reduce the bearing pressure accordingly, and at the time of pile manufacturing While preventing the ditch | groove part from being damaged by demolding, demolding becomes easy. In particular, by changing the number of grooves without changing the shape and dimensions of the groove even if the pile diameter changes, it becomes possible to use a common mold for forming the groove, reducing pile manufacturing costs. Can be planned.

請 Motomeko 2 the described invention, the pile body for root compaction method digging in of claim 1, the outer peripheral area of the pile body sandwiched between a plurality of recessed groove portion is formed to be larger than the outer peripheral area of the groove section Since the outer peripheral area of the pile body between the concave groove portions is larger than the outer peripheral area of the concave groove portion, the shear resistance area between the concave groove portions of the pile main body is formed in the concave groove portion. It becomes larger than the shear resistance area of the part and prevents the shear failure between the recessed grooves of the pile body.

According to the first aspect of the present invention, when a vertical load is applied to the pile main body, the shearing force is integrated through the concave groove portion provided on the outer peripheral surface of the support layer rooting portion of the pile main body. It can be effectively transmitted to the support layer through the part. In addition, the concave groove portion has a tapered portion at the corner portion, so that it is possible to reduce earth and sand adhering to the corner portion of the concave groove portion at the time of pile insertion and to act on the corner portion of the concave groove portion from an underground obstacle. The resistance can be reduced, the destruction of the concave groove portion can be prevented, and furthermore, by providing the taper portion, the bearing pressure area during pile installation can be increased, so that the bearing pressure can be reduced accordingly, It is possible to prevent breakage of the concave groove due to demolding at the time of pile manufacturing and to facilitate demolding. In particular, by changing the number of the grooves without changing the shape and dimensions of the groove even when the pile diameter changes, a common mold for forming the groove can be used, and the manufacturing cost of the pile can be reduced. .

According to the invention 請 Motomeko 2, forming the outer peripheral area of the pile body between the groove portion, so are larger than the outer peripheral area of the groove section, the shear resistance area within the groove portion between the groove portion of the pile body It becomes larger than the shear resistance area of the root-solidified portion, and shear failure between the concave groove portions of the pile body can be prevented.

  Hereinafter, the present invention will be described with reference to an embodiment shown in the drawings.

  FIG. 1 shows a cross section in which a pile body 10 according to the present invention is constructed by a kind of embedded pile method of a medium digging system expansion rooting method, and the medium digging root consolidation method is a bit inserted into the pile body 10. Since the excavation of the ground and the settling of the pile body 10 are performed simultaneously, the frictional force of the outer peripheral surface of the pile is temporarily applied to the tip of the reinforced concrete pile body 11 formed into a cylindrical shape. Steel pipe rod 12 is attached to reduce piles and facilitate pile insertion work.

  Since the friction strength of the root consolidation part 14 embedded in the underground support layer 13 is high in ground strength, a large frictional force level can be obtained, so by increasing the friction force degree between the root consolidation part 14 and the pile body 10 In addition, the frictional force between the support layer 13 and the root consolidation part 14 can be effectively used for the support force of the pile body 10.

The outer diameter DK of the root consolidation part 14 is about 1.36 times the pile diameter D due to the structure and shape of the hydraulic expansion bit used in this construction method, and the strength σc of the root consolidation part 14 is about W / C = 60% By using mortar, it is 23 (N / mm ² ) or more.

  In addition, the pile body 11 is not affected by the pile body 10 without adversely affecting the pile, and the frictional force of the support layer 13 against the pile tip embedded in the support layer 13 is effectively applied to the support force of the pile. A plurality of concave groove portions 15 having a groove bottom portion having a diameter smaller than the outer diameter of the pile main body 11 are provided on the outer peripheral surface of the part to be embedded in the support layer 13.

  The mounting position of these concave groove portions 15 is the portion where the pile tip is embedded in the support layer 13, and from the experimental results, the degree of shear force of the concave groove portion 15 is determined, and the quantity of the concave groove portions 15 is determined from the value. is doing.

  The shape of the recessed groove portion 15 is such that the groove depth is 5 to 20 mm, and the groove width is 8 to 10 times the groove depth. Furthermore, with respect to the shear force generated by the vertical load acting on the pile body 10, a sufficient shear resistance area can be secured for the root hardening material (mortar) formed in each concave groove portion 15, and the pile body 11 The shape and interval of the concave groove portions 15 are set so that a sufficient shear resistance area can be secured between the upper and lower concave groove portions 15 and 15.

  As shown in FIG. 2, these concave groove portions 15 have tapered portions 16 at the upper corner portion and the lower corner portion as corner portions.

  Then, as shown in FIG. 3 (a), when the pile is inserted, the taper portion 16 is provided at the corner of the concave groove portion 15, thereby reducing the adhesion of earth and sand 18 to the right-angled portion 17 shown in (b). The effect can be expected, and by providing the tapered portion 16, it is possible to reduce the catch of the underground obstacle to the concave groove portion 15 when the pile is inserted, and to prevent the concave groove portion 15 from being destroyed.

Further, as shown in FIG. 4 (a), by providing the tapered portion 16 in the recessed groove portion 15, ensure a large bearing capacity area A ₂ than Bearing area A ₁ in the right-angled portions 17 shown in (b) Accordingly, in the taper portion 16, the support pressure σ ₂ is smaller than the support pressure σ ₁ shown in (b), and the effect of reducing the burden stress can be expected. Furthermore, when removing the pile body 10 from mold crushing at the time of manufacturing the pile, if there is a right-angled portion 17 as shown in (b) at the corner of the recessed groove portion 15, there is a possibility that the portion may be damaged, By providing the tapered portion 16, it becomes easy to remove the mold.

  FIG. 5 shows a case where there are two concave grooves 15 like a pile body 10 having a pile diameter of φ500 mm and φ600 mm, and FIG. 6 shows three concave grooves 15 like a pile body 10 having a pile diameter of φ700 mm, φ800 mm and φ900 mm. 7 shows a case where there are four concave grooves 15 like a pile body 10 having a pile diameter of φ1000 mm, φ1100 mm and φ1200 mm.

  As shown in FIGS. 5, 6, and 7, the concave groove portion 15 having the tapered portion 16 is provided with a plurality of the same shape and size, and the number is increased or decreased according to the pile diameter. The groove width of the concave groove portion 15 is set to be constant in consideration of the shear strength of the root hardening material (mortar) in the concave groove portion 15, and the groove depth of the concave groove portion 15 is the cover to the reinforcing bar of the pile body 11. Set to be constant considering the amount. In this way, by making the shape (dimensions) of the recessed groove portion 15 the same shape, the pile manufacturing (formwork) cost can be reduced.

  As shown in FIGS. 8 and 9, the outer peripheral area As2 of the pile body 11 sandwiched between the upper and lower concave groove portions 15 and 15 is formed larger than the outer peripheral area As1 of the concave groove portion 15. In other words, considering the shear strength of pile concrete on the safe side and making it the same as the shear strength of the mortar, the pile body 11 is safe against the axial load on the groove 15 If the outer peripheral area As2 of the pile body 11 is larger than the outer peripheral area Asl of the recessed groove portion 15, the shear resistance area of the pile body 11 is larger than the shear resistance area of the rooting material in the recessed groove portion 15, The pile body 11 is not damaged by the shear stress τ.

  Next, the function and effect of this embodiment will be described.

  As shown in FIG. 1, when the axial force acting on the pile body 10 is transmitted from the tip of the pile to the support layer 13 via the root consolidation part 14, the friction between the surface of the pile body 10 and the root consolidation part 14 If the force is ignored, the shear force based on the axial force at the tip of the pile is propagated to the tip ground with a certain dispersion angle θ. The distance to the bottom surface of the consolidated portion 14 needs to be equal to or greater than the height L1 of the shear force propagation cone 19 having a dispersion angle θ in the root consolidated portion 14. Further, the pile body length embedded in the support layer 13 is the same as the pile diameter D, and the pile main body 11 and the root-solidified portion 14 are integrated by the concave groove portion 15 provided on the outer periphery of the pile tip portion. Sex is secured.

  Then, when a vertical load is applied to the pile body 11, the shear force is applied through the root consolidation part 14 integrated with the recessed groove part 15 provided on the outer peripheral surface of the support layer rooting part of the pile body 11. It can be effectively transmitted to the support layer 13.

  By providing the tapered portion 16 at the corner of the groove 15, it is possible to reduce the earth and sand adhering to the corner of the groove 15 during pile insertion, and to act on the corner of the groove 15 from underground obstacles. Resistance can be reduced, destruction of the concave groove portion 15 can be prevented, and furthermore, by providing the tapered portion 16, the bearing area during pile installation can be increased. In addition to being able to reduce the size, it is possible to prevent breakage of the concave groove portion 15 due to the demolding at the time of manufacturing the pile, and the demolding can be facilitated.

  By changing the number of the grooves without changing the shape and dimensions of the groove 15 even if the pile diameter changes, a common mold for forming the groove can be used, and the manufacturing cost of the pile can be reduced.

  Since the outer peripheral area of the pile main body 11 between the concave groove portions 15 and 15 is formed larger than the outer peripheral area of the concave groove portion 15, a shear resistance area between the concave groove portions 15 and 15 of the pile main body 11 is formed in the concave groove portion 15. It becomes larger than the shear resistance area of the root hardening material, and shear failure between the recessed groove portions 15 and 15 of the pile body 11 can be prevented.

  Next, a shear test of the concave groove 15 at the tip of the pile will be described with reference to FIGS.

(1) Test purpose Load transmission at the tip of the pile is transmitted to the consolidation portion 14 through the pile body 10 by the adhesion force from the inner surface of the pile and the outer surface of the pile and the support pressure of the lower end surface of the pile. Here, for the purpose of increasing the adhesion strength between the root consolidation portion 14 and the outer peripheral surface of the pile, the concave groove portion 15 is disposed on the outer peripheral surface of the pile tip, and the adhesion strength between the pile body 10 and the root consolidation portion 14 is investigated.

(2) Test outline
(a) Content of Implementation The test body was based on the outer diameter of the pile body 11 of 200 mm and the length of 300 mm, and formed a rooted portion 14 on the outer surface and subjected to a punching test. The test body set the shape (depth 7mm, width 60mm) of the ditch | groove part 15, and performed the number of the ditch | groove parts 15 with the concrete test body of 0, 1 place, and 2 places. These concave grooves 15 are all formed in a = 50 mm, b = 5 mm, and c = 7 mm in FIG.

(b) Types of test specimens Table 1 shows test specimens A, B, and C for the investigation of the adhesion strength between the concave groove portion 15 and the root consolidation portion 14.

(3) Production of test specimen
(a) Specimen for Adhesive Strength Investigation The cross-sectional shape of the specimen is the specimens A-1 and A-2 that do not have the concave groove shown in FIG. 10 and one concave groove 15 shown in FIG. And test specimens C-1 and C-2 having two concave grooves 15 shown in FIG.

(b) Manufacture of test body Form of pile body 10; For centrifugal specimen (φ200-300mm)
Forming of root consolidation part 14; Steel plate (t = 2.3mm) in cylindrical shape with inner diameter φ272-250mm and welding Concrete composition of pile body 10; Composition of compressive strength σu = 85 N / mm ² of root consolidation part 14 Mortar formulation; Table 2

  The curing method was air curing. Three specimens (φ100-200mm) for strength investigation were collected at the time of production.

(4) Test Method As shown in FIG. 13, the test method employed a punching test method in which the specimens A, B, and C were sandwiched between the pressure receiving jig 21 and the pressure jig 22 and pressed. In this test, the mortar strength of the root consolidation part 14 was confirmed, and then loaded.

Testing machine: 500t Amsura (Tokyo Henki Manufacturing Co., Ltd.)
Displacement measuring instrument: High sensitivity displacement meter (stroke 50mm), CDP-100 (1 / 100mm)
Loaded load and holding time: Loaded load is set every 30KN in principle, and holding measurement is also performed for 1 minute every 30KN.
Measurement item: Load, pile head displacement, root-set head displacement Destructive load: Maximum load that cannot be held

(5) Summary of test results of adhesion test Table 3 shows the test results. Further, the relationship between the adhesion strength and the displacement is shown in FIGS.

  Furthermore, Table 4 shows the results of the mortar compressive strength of the root consolidation part 14.

(a) Kuigaishu surface adhesion strength when mortar compressive strength of the root hardened portion 14 is 31.2 (N / mm ^2), with no concave groove portion 15 Specimen A-1, A-2, the average adhesion strength It is 2.01 (N / mm ² ), and the groove 15 is one specimen B-1 and B-2, the average adhesion strength is 2.81 (N / mm ² ), and the groove 15 is a test in two places. In the bodies C-1 and C-2, the average adhesion strength is 4.65 (N / mm ² ).

  (b) Specimens A-1 and A-2 without grooves are destroyed by linear displacement (0.2 mm).

  (c) The load on the grooved specimens B-1, B-2, C-1, and C-2 temporarily decreases after linear displacement, but then deforms again and the load increases. The maximum value is shown.

(6) Examination of the degree of shear stress borne by the groove portion 15 From the test results, the burden load in the degree of shear stress between the rooted portion 14 and the groove portion 15 of the pile body 10 is calculated. The load shearing force of the concave groove portion 15 is obtained by subtracting the adhesion force in the adhesion area excluding the concave groove portion 15 from the test load (destructive load). The calculation of the adhesion force in the adhesion area excluding the concave groove portion 15 is obtained by adopting the average adhesion stress degree from the test result in the test body A without the concave groove portion 15.

  Therefore, the shear stress level in the range of the concave groove portion 15 is obtained by dividing this burden shear force by the surface area of the concave groove portion 15.

The calculation formula is as follows.

・ Shear stress degree (τs) of the groove 15
τs = Q / (π × D × L1)
・ Shearing force (Q) of the groove 15
Q = P− (L−L1) × π × D × τA
here,
P: Test load (KN)
D: Pile outer diameter (mm)
L: Length of contact with the root hardening part 14 (mm)
Ll: Length of groove 15 (mm)
τA: Adhesive stress in the range without the groove 15 (N / mm ² )
(Average adhesion stress τA = 2.0lN / mm ^{2 of} A specimen result)

  Table 5 shows the calculation results of the degree of shear stress borne by the concave groove 15.

The shear stress level borne by the concave groove 15 in the experimental results is 6.23 (N / mm ² ) and 4.46 (N / mm ² ) for the specimen B-1 and B-2 with one groove, and the specimen with two grooves. in C-1, C-2 7.42 (N / mm 2), is 7.60 (N / mm ^2).

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing at the time of the pile construction which shows one Embodiment of the pile body for the underground digging firming method which concerns on this invention. It is sectional drawing to which the principal part of the pile body same as the above was expanded. (A) is sectional drawing which shows the movement of the earth and sand in the taper part of a pile body same as the above, (b) is sectional drawing which shows the state in which earth and sand accumulate in the case where there is no taper part. (A) is sectional drawing which shows the action state of the supporting pressure in the taper part of a pile body same as the above, (b) is sectional drawing which shows the state in which the supporting pressure increases when there is no taper part. It is a half cross-sectional view in the case where there are two concave groove portions of the same pile body. It is a half sectional view in case there are three concave groove portions of the same pile body. It is a half sectional view in case there are four concave grooves of the same pile body. It is explanatory drawing which shows the relationship between the outer periphery area As1 of the ditch | groove part in a pile body same as the above, and the outer periphery area As2 of the pile main body pinched | interposed between the ditch | groove parts. It is sectional drawing which shows the relationship between the outer periphery area As1 of the ditch | groove part in a pile body same as the above, and the outer periphery area As2 of the pile main body pinched | interposed between the ditch | groove parts. It is sectional drawing of the test body A which does not have a groove part. It is sectional drawing of the test body B which has one recessed groove part. It is sectional drawing of the test body C which has two recessed groove parts. It is explanatory drawing which shows the point at the time of carrying out a loading test of a test body. It is a characteristic view of the test result which shows the relationship between the adhesion strength of test body A-1, and a pile head displacement amount. It is a characteristic view of the test result which shows the relationship between the adhesion strength of test body A-2, and a pile head displacement amount. It is a characteristic view of the test result which shows the relationship between the adhesion strength of test body B-1, and a pile head displacement amount. It is a characteristic view of the test result which shows the relationship between the adhesion strength of test body B-2, and a pile head displacement amount. It is a characteristic view of the test result which shows the relationship between the adhesion strength of the test body C-1, and a pile head displacement amount. It is a characteristic view of the test result which shows the relationship between the adhesion strength of test body C-2, and a pile head displacement amount.

10 pile
11 Pile body
15 Groove
16 Taper

Claims (2)

A pile body made of cylindrical concrete;
A plurality of concave groove portions having a groove bottom portion having a smaller diameter than the outer diameter of the pile main body provided on the outer peripheral surface of the support layer insertion portion of the pile main body,
These concave groove portions have tapered portions at the corners, and all the numbers according to the pile diameter are provided within a range of length equal to the pile diameter from the pile tip to be embedded in the support layer ,
A pile body for an underground excavation rooting method characterized in that all concave grooves are provided in the same shape and dimensions, and the number is increased or decreased according to the pile diameter . Outer peripheral area of the pile body sandwiched between a plurality of recessed grooves are pile body for root compaction method digging into according to claim 1, characterized in that it is larger than the outer peripheral area of the recessed groove portion.

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