JP2000274175A - Gravel corresponding type excavating head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously conduct excavation even when there are slight gravel by preventing closing in the inflow port of a reverse pipe and the inside of the reverse pipe by gravel in pile execution by a reverse circulation drilling method. SOLUTION: In the excavating head 1 being connected at the front end of a reverse pipe R while having excavating blades 3 at the front end section of a casing pipe 2, the casing pipe 2 is brought to a freely open-close state between the casing pipe, and a plurality of PC steel wires 13, 13..., in which base end sections are supported on the interior wall side of the casing pipe and which are projected towards the inside of the easing pipe, are installed into a lower easing pipe 2B from the open-close section while a screen 11 is mounted into an upper casing pipe 2A from the open-close section so that gravel having a fixed diameter or more does not flow into the reverse pipe R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a pile hole by a reverse construction method, by preventing clogging of a reverse pipe inflow port and a reverse pipe with gravel, boulders, etc., so that even if a pebble layer is encountered, The present invention relates to a gravel-compatible drilling head that can be drilled.

[0002]

2. Description of the Related Art Conventionally, when casting a cast-in-place pile,
In addition to the Benoto method and the earth drill method, the reverse method is often used. In this reverse construction method, the ground is excavated by the excavation head provided at the tip of the reverse pipe, and excavated earth and sand is discharged to the ground through the reverse pipe by reverse circulation flow. In this method, a mud film is formed by the screening action of muddy water by using a water level difference from the groundwater level to excavate up to the supporting ground while stabilizing the hole wall. Although it is superior to the above-mentioned Venoto method and earth drill method in terms of drilling efficiency, excavation becomes impossible when there is gravel or cobblestone (hereinafter collectively referred to as gravel) larger than the reverse pipe diameter. In addition, there is a problem that the type of ground to be excavated is limited due to, for example, blocking of the inside of the reverse pipe when a large amount of gravel having a predetermined diameter or more exists.

[0003]

As a result of a detailed examination of boring data and the like, if there is gravel that cannot be dealt with by the reverse method, naturally another method is used or used in combination with another method. In the construction planning stage, even if the reverse construction method is adopted based on the result of the examination based on boring data, etc., there is a lot of gravel more than expected diameter when actually excavating. In some cases, they encountered gravels larger than the reverse pipe diameter, and were often struggling to deal with them.

[0004] On the other hand, the reverse method can be easily performed even in a narrow place close to another structure.
Development of a drilling head that can be constructed even with some gravel has long been desired.

[0005] Accordingly, a main object of the present invention is to prevent clogging of the reverse pipe inlet and the reverse pipe by the gravel, so that even if some gravel is present, the gravel for the reverse method can be continuously excavated. A compliant drilling head is provided.

[0006]

According to the present invention, there is provided a drilling head for a reverse construction method, comprising a drilling wing provided at a tip end of a casing pipe and connected to a tip end of a reverse pipe. A plurality of elastic linear members that are openable and closable at the middle of the casing pipe, and whose base end is supported on the inner wall side of the casing pipe from the opening / closing part and that is protruded inward of the casing pipe. In addition to the above, a screen is provided from the opening / closing portion to the inside of the upper casing tube so that gravel having a predetermined diameter or more does not flow into the reverse tube.

According to the excavating head of the present invention, even if gravel is present during excavation, the gravel is introduced into the casing so as to push away while deforming the elastic linear member.
Gravel having a diameter equal to or larger than a predetermined diameter remains inside the casing without passing through a screen provided in the upper casing. Therefore, blockage at the reverse pipe inlet and inside the pipe is prevented, and excavation can be continued even if some gravel is present during excavation.
At any time during the excavation (when it is full), the excavation head is raised to the ground, the upper casing is opened and removed, and excavation is resumed.

[0008] In the above invention, it is desirable that the elastic linear member is a PC steel wire disposed substantially obliquely upward along a radial direction. In addition, the screen has a two-stage structure of a first screen provided at the reverse pipe inlet and a second screen provided at a position slightly separated from the reverse pipe inlet, whereby the reverse pipe inlet is provided. Gravels having a predetermined diameter or more can reliably remain in the casing without closing the portion. Further, it is preferable that the excavating wing provided at the tip of the casing pipe is three or more wings, and even if there is a large gravel, it is desirably crushed to a certain diameter or less and then taken into the casing.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view of a gravel-compatible excavating head 1 according to the present invention, FIG. 2 is a plan view, FIG. 3 is a bottom view, and FIG. 4 is a longitudinal sectional view.

The excavating head 1 for gravel (hereinafter simply referred to as an excavating head) has a structure in which an excavating wing 3 is provided at the tip of a casing tube 2, and a connecting pipe 4 is provided in an upper portion thereof and reversely operated by bolts or the like. It is adapted to be connected to the tip of the tube R. As shown in FIG. 3, the illustrated excavation wing 3 has a plurality of bits 3a, 3a.
Center ring 5A with three excavating wings 3A to 3C on which are fixed
Are three-wing type excavating wings arranged in three directions at 120 ° center angle intervals from the peripheral surface of the outer ring, and the excavating wings 3A to 3C are firmly fixed by a reinforcing ring 5B disposed outside the center ring 5A. The tip of each of the excavating wings 3A to 3C is fixed to the tip of the casing tube 2 respectively.
The center ring 5A has three excavating wings 3A to 3A.
Central excavation bits 3D and 3E are provided in order to excavate the central part that cannot be compensated by C.

The casing tube 2 has a longitudinally intermediate portion,
Specifically, it can be opened and closed at a position on the upper side of the casing tube 2. The casing tube 2 is divided into an upper casing tube 2A and a lower casing tube 2B. The upper and lower casing tubes 2A, 2B are interconnected by a hinge 6, and the upper casing tube 2A and the lower casing tube 2B straddle the opening / closing portion. Are provided at the corresponding positions, and bolts 8 are inserted between the joint flanges 7 and 7 and fastened with nuts, so that the upper casing pipe 2A is closed at least at the time of excavation. The members 9, 9,... Fixed along the longitudinal direction on the peripheral surface of the casing pipe 2 are pipe- or bar-shaped reinforcing members for increasing the wall strength of the casing pipe 2.

On the other hand, inside the casing tube 2, a gravel residue holding device 10 for keeping gravel remaining in the casing tube 2B on the side of the lower casing tube 2B, and a predetermined diameter inside the upper casing tube 2A. A screen 11 for preventing the above-mentioned gravel from flowing into the reverse pipe R is provided.

First, as shown in detail in FIG. 5, the gravel residue holding device 10 has a base end fixed to the inner wall of the lower casing tube 2B and a steel wire directed obliquely upward at the center of the casing tube. Are provided at predetermined intervals in the circumferential direction, and the PC steel wires 13, 13,... Are fixed to the steel wire support members 12, 12, by wire clips 14, 14, respectively. Therefore, as shown in FIG. 6, when gravels are encountered during excavation, the gravels
While being elastically deformed, they are pushed away and flow into the casing tube 2, and as shown in FIG. 4, they remain in the lower casing tube 2B. In this example, the PC steel wire 13 was used for the inflow passage of the gravel. However, any other member may be used as long as it is a linear member having some rigidity and high elasticity. Also, at the center, as shown in the figure, the tips of the PC steel wires 13, 13...
When the 3, 13 ... crosses each other, the gravel that has once flowed in is supported by the entire PC steel wire 13, 13, ... so that it does not flow out again. Further, in the present embodiment, the PC steel wires 13, 13,... Are arranged radially in a plan view, but may be arranged along one direction.

On the other hand, the screen 11 is composed of a first screen 11A disposed at the inlet of the connecting pipe 4 (reverse pipe inlet I) and a second screen 11B disposed at a position slightly apart from the reverse pipe inlet I. And a two-stage configuration.

As shown in FIG. 7, the first screen 11A is a screen in which flat bars 15, 15 are assembled in a cross direction around the reverse pipe inlet I, and the second screen 11B is As shown in FIG. 8, the screen has flat bars 15, 15... Of course, in this example, the screen structure has a two-stage structure.
Only one may be provided alone.

The gravel flowing into the lower casing pipe 11B by the second screen 11B is reliably retained and retained in the lower casing pipe 2B without the gravel having a predetermined diameter or more flowing into the reverse pipe R. In addition, since a gap is formed between the reverse pipe inlet I and the small-diameter rubble that has passed through the second screen 11B together with mud water in the reverse pipe R without blocking the reverse pipe inlet I. It will flow into.

[0017] In performing drilling using such drilling head 1, as shown in FIG. 9 (A) according to conventional drilling procedures, sequentially replenishing unit reverse pipe R _i having a predetermined length with respect to the drilling head 1 Meanwhile, the excavating head 1 is rotated around the axis together with the reverse pipe R to penetrate the ground.

Gravel existing in the excavated area is sequentially taken into the casing pipe 2, gravel having a predetermined diameter or more is retained and retained in the lower casing pipe 2 B, and only the gravel having passed through the screen 11 and having a diameter smaller than the predetermined diameter is reversed. Discharged to the ground through pipe R. When it has been determined that the lower casing pipe 2B has been penetrated to a predetermined depth and that the gravel is almost completely filled in the lower casing pipe 2B, the excavating head 1 is once pulled up to the ground, as shown in FIGS. After the pipe 2A is opened to remove the gravel remaining in the lower casing pipe 2B, the upper casing pipe 2A is closed, and as shown in FIG.
Drilling down to the head 1 to sequentially replenishing with current drilling site units reverse tube R _i, so as to start drilling again.

[0019]

As described in detail above, according to the present invention, gravel encountered during excavation is taken into the casing tube, while gravel having a diameter larger than a predetermined diameter is retained inside the casing pipe, and gravel having a diameter smaller than the predetermined diameter is retained. Since only the muddy water flows into the reverse pipe, excavation can be continued even if some gravels exist in the ground.

[Brief description of the drawings]

FIG. 1 is a side view of a gravel layer-compatible excavation head 1 according to the present invention.

FIG. 2 is a plan view thereof (viewed along the line II-II in FIG. 1).

FIG. 3 is a bottom view (viewed along the line III-III in FIG. 1).

FIG. 4 is a longitudinal sectional view thereof.

FIG. 5 is a view taken along line VV of FIG. 4;

FIG. 6 is a diagram showing the state of gravel flowing into the casing tube.

FIG. 7 is a view taken along line VII-VII of FIG. 4;

FIG. 8 is a view taken along line VIII-VIII of FIG. 4;

FIG. 9 is a diagram showing a digging operation procedure performed by the digging head 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drilling head, 2 ... Casing pipe, 2A ... Upper casing pipe, 2B ... Lower casing pipe, 3 ... Drilling wing, 3a ...
Bit, 4 ... Connection pipe, 10 ... Gravel residual holding device, 11 ... Screen, 11A ... First screen, 11B ... Second screen, 12 ... Steel wire support, 13 ... PC steel wire, 14 ... Wire clip, 15 ... Flat bar, R ... reverse tube,
_Ri : unit reverse pipe, I: reverse pipe inlet

Claims (4)

[Claims] An excavating head for a reverse construction method, wherein a drilling wing is provided at a distal end of a casing pipe and used by being connected to a distal end of a reverse pipe, wherein the casing pipe is freely openable and closable in the middle of the casing pipe. A plurality of elastic linear members whose base ends are supported on the casing tube inner wall side and protrude toward the inside of the casing tube are provided inside the lower casing tube from the portion, and the inside of the reverse tube is provided inside the upper casing tube from the opening / closing portion. A gravel-compatible excavation head characterized in that a screen is provided to prevent inflow of gravel larger than a predetermined diameter. 2. The excavation head according to claim 1, wherein said elastic linear member is a PC steel wire disposed substantially obliquely upward along a radial direction. 3. The screen according to claim 1, wherein the screen has a two-stage structure including a first screen provided at a reverse pipe inlet, and a second screen provided at a position slightly separated from the reverse pipe inlet. 2. A gravel-compatible excavation head according to any one of 2. 4. The gravel-compatible excavating head according to claim 1, wherein the excavating wing provided at the tip of the casing pipe is three or more wings.