JP2008045327A - Construction method for head-enlarged pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for a head-enlarged pile, which enables efficient and safe construction while preventing the mixing of excavated soil, causing a decrease in the end bearing capacity of the pile, by utilizing a preboring method. <P>SOLUTION: A casing 2, the spiral blade 2a of which is provided on its outer periphery, and a drill rod 3, which passes through the casing 2, are inserted into ground while being rotated, so that a hole 4 for pile construction can be bored. An upper portion of the hole 4 is cut by pulling out the casing 2 while rotating it, so that a diameter-enlarged portion 4a can be formed in the upper portion of the hole 4. Next, a prefabricated pile is erected in the hole 4 by using the casing 2 as a guide, so that a main body portion 1b of the head-enlarged pile 1 can be formed. Subsequently, the casing 2 is removed, and a head-enlarged portion 1a of the head-enlarged pile 1 is formed in the diameter-enlarged portion 4a after that. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for constructing a head-expansion pile made of a ready-made pile by a pre-boring method.

  In order to prepare for an excessive shearing force and bending moment acting on the pile head, a head-expanded pile having an enlarged head with a larger diameter than the main body of the pile is known. This type of expanded pile is mainly formed from pre-made piles such as RC piles, PC piles and SC piles, steel pipe piles, etc., and is often constructed by a pre-boring method.

  The pre-boring method is a method that uses a ground auger or the like to open a hole for pile construction in the ground in advance, and lays a ready-made pile in this hole for pile construction to construct a pile. ing.

  Conventionally, when a pre-boring method is used to construct a head-expanded pile made of ready-made piles, the pile is placed on the top of the pile construction hole before or after drilling the pile construction hole for constructing the pile using an earth auger or the like. An enlarged diameter portion having an inner diameter larger than that of the construction hole is formed, and then a pre-made pile is put into the pile construction hole to form a main body portion of the pile, and subsequently, an enlarged head portion is formed in the enlarged diameter portion.

  In this case, the pile support force is generally evaluated by the sum of the pile tip support force and the peripheral surface friction force of the pile, and most of the piles are constructed as piles that depend on the pile tip support force. The tip processing is important.

JP 62-253817 A JP 2006-132100 A JP 2006-118215 A

  However, the method of forming a large-diameter portion by drilling a large hole in the upper part of the pile-construction hole before drilling the pile-construction hole can be an obstacle to the subsequent work. There was a safety problem.

  On the other hand, after drilling a hole for pile construction, the method of cutting the hole wall at the top of the hole for pile construction to form an enlarged diameter part is that the excavated soil falls into the hole for pile construction, and this increases the bearing capacity of the pile. There is a risk of lowering.

  Also, as with the hole for pile construction, if you try to drill the enlarged diameter part with an earth auger, it is necessary to use a drilling rod with a large diameter. There was a risk of being forced to work efficiently.

  Furthermore, each method has a problem that, by having an enlarged diameter portion at the upper part of the hole for pile construction, when the ready-made pile is stood in the hole for pile construction, the pile setting accuracy is lowered.

  The present invention was made in order to solve the above-mentioned problems. The construction of a head-expanded pile that can be constructed efficiently and safely while using a pre-boring method and preventing mixing of excavated soil leading to a decrease in the bearing capacity of the pile. It is intended to provide a method.

  The invention according to claim 1 is a method for constructing a head-expanded pile by a pre-boring method, wherein the casing having excavation means on the outer peripheral upper part and the excavating rod penetrating the casing are inserted into the ground while being rotated. A step of drilling a hole, a step of forming an enlarged portion in the upper portion of the hole for pile construction by cutting an upper portion of the hole for pile construction by means of excavating means of the casing, and the casing as a guide Having a step of forming a main body part of the head-expanded pile by standing a ready-made pile in a hole for pile construction, a step of removing the casing, and a step of forming a head-expanded portion of the head-expanded pile in the diameter-expanded portion. It is a feature.

  The present invention provides a drilling means at the upper part of the outer periphery of the casing that protects the hole wall, and excavates the casing after drilling the hole for pile construction when constructing the expanded pile made of precast pile by the pre-boring method. The diameter-expanded portion can be easily formed in the upper part of the hole for pile construction by pulling out without rotating in the direction.

  In addition, when constructing ready-made piles during construction of expanded diameter parts and pile construction holes, the upper part of the pile construction holes is protected by a casing so that excavated soil does not fall into the pile construction holes. It is intended to prevent a decrease in the bearing capacity of the pile caused by the fall of soil.

  Furthermore, the verticality of the ready-made pile is maintained by standing the casing vertically on the upper end of the hole for pile construction and using the casing as a guide member when standing the ready-made pile in the hole for pile construction. And the construction accuracy is improved.

  In addition, it is desirable to use a muddy water method in combination with the drilling holes for pile construction in order to protect the hole wall during excavation. Further, the head extension can be formed by either cast-in-place concrete or ready-made piles. Furthermore, an enlarged diameter part can be provided in the front-end | tip of a pile main-body part, and the front-end | tip supporting force of a pile can also be improved.

  The method for constructing the expanded pile according to claim 2 is the method for constructing the expanded pile according to claim 1, wherein the excavating means is a spiral blade. The excavation means for cutting the upper part of the hole for pile construction to form the enlarged diameter part is not particularly limited. In particular, the spiral blade efficiently cuts the hole wall for pile construction and expands the diameter. can do.

  The construction method of the head-expansion pile according to claim 3 is the construction method of the head-expansion pile according to claim 1 or 2, wherein the head extension portion is formed by a ready-made pile. The head-expanded part can be formed by either cast-in-place concrete or ready-made piles, but construction with ready-made piles can save labor in field construction.

  When cutting the upper part of a hole for pile construction to form an enlarged diameter part and when putting a ready-made pile into the hole for pile construction, the present invention installs a casing on the upper end part of the hole for pile construction, By making it not fall into the hole for pile construction, the excavated soil falls into the borehole, and this does not cause the tip support force of the pile to decrease.

  In addition, when a ready-made pile is stood in the pile construction hole, a casing is installed at the upper end of the pile construction hole, and this casing is used as a guide member for vertically placing the ready-made pile in the pile construction hole. Therefore, since the verticality of the ready-made piles can be maintained by preventing the ready-made piles from wobbling, the ready-made piles can be put into the hole for pile construction efficiently and accurately.

  FIG. 1 shows an example of a head-expanded pile, and the total length of the main-body portion 1b of the head-expanded pile and the head-expanded portion 1a having a diameter larger than that of the main-body portion 1b is integrated with a ready-made pile such as RC pile, PC pile, SC pile, and steel pipe pile. Is formed.

  The main body portion 1b of the pile is integrally formed by adding a necessary number of ready-made piles formed to have a certain length and joined to each other, and the enlarged head portion 1a is integrally formed at the upper end portion of the main body portion 1b.

  Fig.2 (a)-(g) shows the construction method of the expansion pile by the pre-boring method, and demonstrates a construction procedure below.

  First, while rotating the casing 2 and the excavating rod 3 penetrating the casing 2, the pile construction hole 4 is drilled by being pushed vertically into the ground. The casing 2 used here is formed of a steel pipe, and has a spiral blade 2a that is continuous from the upper end to the middle of the steel pipe on the outer periphery. The excavation rod 3 is configured such that the rods can be successively extended and extended in accordance with the depth of the pile construction hole 4. In addition, a muddy water method is also used for drilling the pile construction hole 4 to protect the hole wall.

  In this way, if the pile construction hole 4 is drilled to a predetermined depth, the casing 2 is left in the ground, and the excavating rod 3 is pulled up and removed while rotating. Moreover, a pile circumference fixing liquid (not shown) is injected into the pile construction hole 4. In addition, a pile periphery fixing liquid is a solidification liquid for fixing the main-body part 1b of the head-expansion pile 1 formed in the hole 4 for pile construction integrally.

  Next, the casing 2 is pulled out while rotating, and an enlarged diameter portion 4 a having a diameter larger than the diameter of the pile construction hole 4 is formed in the upper part of the pile construction hole 4.

  In this case, by pulling out the casing 2 while rotating in the propulsion direction, the hole wall at the top of the hole 4 for pile construction is cut by the spiral blade 2a of the casing 2, and the excavated soil is discharged to the ground by the spiral blade 2a. Thus, the enlarged diameter portion 4a is formed in the upper part of the hole 4 for pile construction.

  The casing 2 stands vertically on the ground in a state in which only a portion above the middle portion of the casing 2 having the spiral blade 2a is pulled out from the ground and a portion below the middle portion is inserted into the upper end portion of the hole 4 for pile construction. wear. By carrying out like this, it can prevent that excavated soil falls in the hole 4 for pile construction.

  Next, the ready-made pile used as the main-body part 1b of a pile is stood up in the hole 4 for pile construction. In this case, the ready-made pile passes through the casing 2 and stands in the pile construction hole 4 to maintain the verticality of the ready-made pile. Moreover, the ready-made pile formed in fixed length according to the length of the main-body part 1b of a pile is added one by one, and it stands in in the hole 4 for pile construction, connecting with each other, and forms the full length of the main-body part 1b. And if construction of the main-body part 1b is completed, the casing 2 will be removed.

  Next, the ready-made pile used as the head-expansion part 1a is stood up in the diameter expansion part 4a, and the full length of the head-expansion pile 1 is formed by joining integrally with the main-body part 1b.

  The present invention makes it possible to construct a head-expanded pile efficiently and safely using a pre-boring method and preventing mixing of excavated soil that causes a decrease in the tip support force of the pile.

It is a front view which shows an example of an expansion head pile. (A)-(g) is process drawing which shows the construction procedure of the expansion pile by the pre-boring method. (A) is a front view of the casing used by this construction method, (b) is a longitudinal cross-sectional view which shows the use condition of a casing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head-expanded pile 1a Head-expanded part 1b of head-expanded pile Main part of head-expanded pile 2 Casing 2a Spiral wing (excavation means)
3 Drilling rod 4 Pile construction hole 4a Expanded part

Claims (3)

  It is a construction method of a head-expanded pile by a pre-boring method, and a step of drilling a hole for pile construction by inserting it into the ground while rotating a casing having a drilling means on the outer periphery and a drilling rod passing through the casing, Cutting the upper part of the hole for pile construction by means of excavating means of the casing, and forming an enlarged diameter part on the upper part of the hole for pile construction; A method for constructing a head-expansion pile, comprising: a step of forming a main body portion of the head-expansion pile by standing; a step of removing the casing; and a step of forming a head-expansion portion of the head-expansion pile in the diameter-expanded portion. .   2. The method for constructing a head pile according to claim 1, wherein the excavating means is a spiral wing. The method for constructing a head-expansion pile according to claim 1 or 2, wherein the head-expansion portion is formed by a ready-made pile.

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