JP2020016062A - Excavation head - Google Patents

Abstract

To provide an excavation head capable of easily crushing a columnar improved pile buried in the ground without misalignment.SOLUTION: An excavation head 1 mounted on an auger rod and crushing a columnar improved pile buried underground comprises a rotating shaft 10 attached to the auger rod, at least three spiral excavation wings 20 provided around the rotating shaft 10, a small bit 30 attached to an end 20a of the excavation wing 20 in the excavation direction, and a leading claw 40 attached to an outer peripheral portion 20b of the excavation wing 20 and having a tip projecting in the excavation direction from a tip of the small bit 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drilling head mounted on an auger rod and crushing a column-shaped improved pile buried underground.

  When a building such as a house is constructed, if the strength of the ground is found to be insufficient, ground improvement work for stabilizing the ground may be performed. For example, a ground improvement work called a “columnar improvement method” is known. The pillar improvement method involves excavating the ground, injecting cement slurry, mixing the cement slurry and the soil contained in the ground in that state, and solidifying the mixture to form a columnar pile in the ground. It is a construction method. These piles are called pillar-type improved piles and function to stabilize buildings built on soft ground. The column improvement method is an effective method when the soft layer continues from the ground surface, and can be constructed using relatively small machines. It has increased.

  When the deep part of the ground is soft, ground improvement work called “slurry mechanical stirring type deep mixing method” is performed. The slurry-based mechanical stirring type deep mixing method is based on excavating the ground while injecting cement slurry and stirring with a stirrer.When the excavation reaches a predetermined depth, the stirrer is repeatedly moved up and down, so that This is an improvement in the mixing property between the cement slurry and the soil, and this is also a type of columnar improvement method. In the slurry mechanical stirring type deep mixing method, a high quality columnar improved pile can be formed by controlling the stirring speed of the stirrer and the vertical movement speed (excavation speed and lifting speed).

  As described above, the columnar improvement pile formed in the ground by the columnar improvement method is basically a solid columnar body composed of a mixture of cement slurry and soil. It is a simple structure mainly composed of concrete that does not contain such wires.

  By the way, when selling land, it is sometimes necessary to dismantle and level the buildings built on the land. However, on the land where the above-mentioned ground improvement work was performed, the columnar improvement pile remains in the ground, so it is not enough to simply clear the ground surface, and the columnar improvement pile must be removed. The valuation of the land may be low. Therefore, when piles and the like are buried in the ground, it is desired to completely remove the piles and restore the land to almost the original state.

  As a technology for removing columnar improved piles, for example, focusing on the property that columnar improved piles are brittle and easier to break compared to existing piles that are often used for relatively large buildings such as factories and buildings, There is a method of crushing and removing the improved pile with a drilling head mounted on an auger rod (for example, see Patent Document 1). According to Patent Literature 1, as a first step, a cylindrical casing is inserted into the ground to surround a part of the columnar improvement pile with the casing, and as a second step, an auger rod with a drilling head is mounted. The drilling head is guided to the columnar improvement pile by rotating and lowering so as to penetrate the inside of the casing, and the columnar improvement pile can be reliably crushed.

JP 2017-25534 A

  Since the columnar improvement pile is used in ground improvement work for general houses, it is desired that the columnar improvement pile be removed with as simple a device configuration as possible. For example, in order to implement the technology described in Patent Literature 1 with a simpler device configuration, a method of crushing a columnar improved pile with an excavating head without using a casing is assumed.

  However, since the excavation head has a conical shape with a sharp tip as a whole, if the casing is not used, there is a risk of misalignment. In particular, since the columnar improvement pile is formed in soft ground, the excavation direction tends to deviate from the columnar improvement pile to the surrounding soft soil. Therefore, in order to implement the technique described in Patent Document 1 without using a casing, a drilling head suitable for crushing the columnar improved pile is required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a drilling head capable of easily crushing a columnar improved pile buried underground without misalignment.

The feature configuration of the excavating head according to the present invention for solving the above-mentioned problems is as follows:
A drilling head that is attached to an auger rod and crushes a columnar improved pile buried underground,
A rotating shaft attached to the auger rod,
At least three spiral excavation wings provided around the rotation axis;
A small bit attached to the end of the excavation wing in the excavation direction,
A leading claw attached to an outer peripheral portion of the excavation wing, the tip of which protrudes in the excavation direction from the tip of the small bit.

  In the drilling head of this configuration, a leading claw projecting in the drilling direction from the small bit is attached to the outer peripheral portion of at least three excavating wings. The pawls excavate the soil around the columnar improvement pile, and are fitted so as to suppress the columnar improvement pile from at least three directions. As a result, the excavating head of the present invention can reliably catch the columnar improved pile and crush it effectively without misalignment. In addition, since the leading claws are separately mounted on the respective excavating wings, the excavated material excavated by the leading claws is discharged from between the leading claws, and is less likely to accumulate in the ring-shaped groove formed by excavating the leading claws. . As a result, the excavating head of the present invention can prevent the excavated material excavated by the preceding claw from hindering subsequent excavation, and can crush the columnar improved pile with high excavation efficiency.

In the drilling head of the present invention,
It is preferable that the tip of the leading claw protrudes from the tip of the small bit by 10 to 30 cm in the excavation direction.

  According to the excavating head of this configuration, since the tip of the leading claw protrudes from the tip of the small bit by 10 to 30 cm in the drilling direction, the leading claw is sufficiently fitted to the columnar improvement pile before crushing, and the misalignment is ensured. Can be prevented.

In the drilling head of the present invention,
It is preferable that the leading claw has a tip turning radius larger than the radius of the columnar improvement pile.

  According to the excavating head of this configuration, since the turning radius of the tip of the leading claw is larger than the radius of the columnar improvement pile, when the tip of the leading claw reaches the upper end of the columnar improvement pile by excavation, the leading claw is moved to the columnar improvement pile. It is easy to hit outside. Therefore, the positioning of the excavation head at the start of excavation becomes easy.

In the drilling head of the present invention,
The rotation radius R of the leading claw on the inner surface closest to the rotation axis and the radius r of the columnar improvement pile are represented by the following relational expression (1):
1 ≦ R / r ≦ 1.1 (1)
It is preferable to satisfy the following.

  According to the excavating head of this configuration, the rotation radius R of the inner surface closest to the rotation axis of the preceding claw and the radius r of the columnar improvement pile satisfy the above relational expression (1). Even in the case where the inner surface of at least one of the leading claws attached to at least three excavation wings comes into contact with the columnar improvement pile, the deviation width is suppressed to less than 10% of the radius of the columnar improvement pile. In addition, it is possible to maintain a positional relationship in which the entire columnar improvement pile overlaps the excavation wing in a vertical view. As a result, the columnar improved pile can be reliably crushed.

In the drilling head of the present invention,
It is preferable that the preceding claw has an inclined surface inclined from a tip end toward the excavation wing.

  According to the excavating head of this configuration, the leading claw has an inclined surface inclined from the tip toward the excavating wing side, so that when the leading end of the leading claw reaches the upper end of the columnar improved pile, a slight misalignment has occurred. Also in this case, when the inclined surface comes into contact with the edge of the upper end of the columnar improvement pile, the leading claw escapes to the soil side around the columnar improvement pile, and the misalignment is corrected.

In the drilling head of the present invention,
Preferably, the small bit is a conical bit having a rotatably mounted bit body.

  The small bit is more likely to wear than the preceding claw that excavates the soft soil around the columnar improved pile because it cuts the hard columnar improved pile, but according to the drilling head of this configuration, the small bit is a conical bit. Therefore, even if the small bit is worn, the sharp shape is maintained for a long time, so that the life can be extended. As a result, the balance between the small bit and the wear of the leading claw is improved.

FIG. 1 is an explanatory view of the excavating head of the present invention. FIG. 2 is a front view of a small bit constituted by a conical bit. FIG. 3 is an explanatory diagram of the preceding claw. FIG. 4 is a diagram illustrating a use form of the excavating head of the present invention. FIG. 5 is an explanatory diagram of a digging head according to another embodiment.

  Hereinafter, the excavating head according to the present invention will be described. However, the present invention is not intended to be limited to the embodiments described below and the configurations described in the drawings.

(Column improved pile)
First, a method of removing an underground pile and a method of removing an underground pile according to the present invention will be described. As described above, column improvement piles can be used as solid materials that do not contain any bars or wires that are formed in the ground when performing ground improvement works such as column improvement methods or slurry-based mechanical stirring type deep mixing methods. It is a columnar body. The component of the columnar improvement pile is mainly a mixture of cement and soil. When performing ground improvement work, first, a cement slurry is prepared. The mixing ratio of the cement slurry is adjusted to a water / cement ratio (weight ratio) of 50/50 to 90/10, preferably 60/40 to 80/20, and more preferably 70/30. The soil mixed with the cement slurry is usually the soil (ie, excavated soil) existing on the ground where the ground improvement work is performed. The mixing ratio between the cement slurry and the soil takes into account the condition of the ground to be constructed (type of excavated soil, grain size, hardness, viscosity, water content, etc.). It is adjusted to satisfy the vertical support force.

  The column-shaped improved pile is usually formed in a cylindrical shape because it is formed inside an excavation hole in the ground. The size of the columnar improvement pile is determined by the size of the excavation hole, that is, the excavation conditions. The size of the columnar improvement pile is usually set to a diameter of 400 to 1000 mm, preferably 500 to 800 mm, more preferably 500 to 600 mm, and a height of 1 to 10 m. In addition, in the case of ground improvement work in a general residential area, about 10 to 80 columnar improvement piles are formed in the ground below the foundation of the house in one construction.

Column-shaped improved piles are required to satisfy certain standards from the viewpoint of safety and the like. For example, an allowable vertical bearing capacity is defined as an index of the improved ground on which the columnar improved piles are constructed. The allowable vertical bearing strength is a numerical value obtained by dividing a vertical ultimate bearing capacity at the time of ground shear failure by a predetermined safety factor. In the long term, it is considered that it is desirable that the allowable vertical bearing capacity of the improved ground achieves 20 kN / m ² or more. Further, it is considered that it is desirable that the columnar improved pile itself achieves a strength of 600 kN / m ² or more in a uniaxial compression test.

[Drilling head]
The excavating head of the present invention is mounted on an auger rod and used for crushing a column-shaped improved pile buried underground. FIG. 1 is an explanatory diagram of a drilling head 1 according to the present invention. FIG. 1A is a perspective view of the excavating head 1, FIG. 1B is a front view of the excavating head 1, and FIG. 1C is a bottom view of the excavating head 1. The drilling head 1 includes a rotating shaft 10, a drilling wing 20, a small bit 30, and a leading claw 40.

  The rotating shaft 10 rotates with the rotation of the auger rod when the rear end 10a is attached to the auger rod.

  A spiral excavation wing 20 is provided around the rotary shaft 10 so that the tip 10b is in the excavation direction. In the example shown in FIG. 1, three excavation wings 20 are provided. However, if the excavation head 1 of the present invention has at least three excavation wings 20, each excavation wing 20 has a leading claw 40. By attaching the ridges, misalignment can be effectively prevented, and the number of the excavating wings 20 may be four or more. Each of the excavating wings 20 is welded and fixed to the outer peripheral portion of the rotating shaft 10 in parallel at equal intervals, and has substantially the same outer diameter.

  A plurality of small bits 30 are attached to the excavation end 20a of each excavation wing 20 so as to protrude from the end 20a. By arranging the small bits 30 in this manner, when the outer diameter of the excavation wing 20 is equal to or larger than the diameter of the columnar improvement pile to be crushed, the small bits 30 cut the columnar improvement pile. The small bit 30 is preferably constituted by a conical bit. FIG. 2 is a front view of the small bit 30 constituted by a conical bit. In the example shown in FIG. 2, the small bit 30 has a holder 31 that is fixedly welded to the end 20 a, and a bit main body 32 whose tip 32 a is formed in a conical shape and is rotatably mounted on the holder 31. By configuring with such a conical bit, the small bit 30 can maintain the sharpened state of the tip 32a for a long period of time even when wear is advanced by cutting a hard columnar improved pile.

  A leading claw 40 extending in the direction of excavation is welded and fixed to the outer peripheral portion 20b of each excavation wing 20. The tip of the leading claw 40 projects further in the excavation direction than the tip of the small bit 30. Here, in the example shown in FIG. 1, since the lower end of the excavating head 1 has a generally conical shape that is sharpened toward the excavation direction, the plurality of small bits 30 are arranged at various positions along the excavation direction. Have been. In the configuration in which the positions in the excavation direction are different among the plurality of small bits 30, the “tip of the small bit 30” in the comparison of the amount of protrusion in the excavation direction with the tip of the leading claw 40 indicates that Means the tip of the small bit 30. Since the leading end of the leading claw 40 projects in the excavation direction from the leading end of the small bit 30, the leading claw 40 excavates the soil around the columnar improved pile prior to the small bit 30 for cutting the columnar improved pile. The leading claw 40 attached to each excavation wing 20 is fitted so as to suppress the columnar improved pile from at least three directions. The amount of protrusion L from the tip of the small bit 30 to the tip of the leading claw 40 is preferably 10 to 30 cm. When the protrusion amount L is within the above range, when the columnar improvement pile is crushed by the excavating head 1, the leading claw 40 is sufficiently fitted to the columnar improvement pile before crushing, and the misalignment can be reliably suppressed. . If the protrusion amount L is smaller than 10 cm, the fitting of the leading claw 40 to the columnar improvement pile becomes insufficient, and it may be difficult to suppress the columnar improvement pile by the leading claw 40. If the protrusion amount L is larger than 30 cm, the load applied to the welding portion of the leading claw 40 during excavation becomes excessive, and the leading claw 40 may be damaged. Further, it is preferable that the leading claw 40 is attached to the outer peripheral portion 20b at a position from the tip 20a. Accordingly, in a structure in which the tip of the leading claw 40 projects in the excavation direction from the tip of the small bit 30, the length of the leading claw 40 along the excavation direction can be shortened. It is possible to reduce the load applied to the welding site.

It is preferable that the leading claw 40 be configured such that the rotation radius at the tip is larger than the radius of the columnar improvement pile. If the rotation radius of the leading end of the leading claw 40 is larger than the radius of the pillar improvement pile, when the leading end of the leading claw 40 reaches the upper end of the pillar improvement pile, the leading claw 40 is easily caught on the outer peripheral surface of the pillar improvement pile, and excavation is started. The positioning of the excavating head 1 at the time becomes easy. Further, the leading claw 40 has the following relational expression (1), where R is the radius of rotation of the inner surface of the leading claw 40 and r is the radius of the columnar improved pile.
1 ≦ R / r ≦ 1.1 (1)
It is preferable that it is comprised so that it may satisfy | fill. If R / r is within the above range, any of the inner surfaces of the leading claws 40 may contact the columnar improvement pile even when the columnar improvement pile is crushed by the excavating head 1 even if the core is misaligned. Thus, the displacement width can be suppressed to less than 10% of the radius of the columnar improvement pile, and the positional relationship in which the entire columnar improvement pile overlaps the excavation wing 20 in a vertical view from the rear end side of the excavation head 1 can be maintained. Thus, the columnar improved pile can be reliably cut by the small bit 30. If R / r is smaller than 1, the leading claw 40 does not fit into the columnar improvement pile, and there is a possibility that a part of the columnar improvement pile cannot be cut by the small bit 30. If R / r is larger than 1.1, there is a possibility that the misalignment width cannot be sufficiently suppressed when a misalignment occurs when the excavating head 1 crushes the columnar improved pile.

  FIG. 3 is an explanatory diagram of the leading claw 40. FIG. FIG. 3A is a perspective view of the preceding claw 40, and FIG. 3B is a bottom view of the preceding claw 40. The leading claw 40 has a rod-shaped claw body 41 and a reinforcing portion 42 for reinforcing the fixing strength to the outer peripheral portion 20b. It is preferable that the claw main body 41 is formed so as to have an inclined surface 41b inclined from the tip end 41a toward the excavation wing 20 side. In the case where the tip of the leading claw 40 reaches the upper end of the pillar-shaped improved pile during the crushing of the pillar-shaped improved pile by the excavation head 1, even if a slight misalignment has occurred, the inclined surface 41 b is formed on the edge of the upper end of the pillar-shaped improved pile. The contact causes the leading claw 40 to escape to the soil side around the columnar improvement pile, thereby correcting misalignment.

  Next, a use form of the excavating head 1 of the present invention will be described. FIG. 4 is a diagram illustrating a use form of the excavating head of the present invention. FIG. 4A is a diagram illustrating an entire configuration of a use form of the excavation head 1, and FIG. 4B is a diagram illustrating a state in which the excavation head 1 has reached the upper end of the columnar improvement pile P. FIG. 4C is a cross-sectional view taken along a line AA in FIG. When removing the pillar improvement pile P formed by the ground improvement work, the excavation head 1 is connected to the auger 3 via the auger rod 4 as shown in FIG. It is arranged vertically above the pile P with its position aligned. In this state, by driving the auger 3 and rotating the auger rod 4, excavation by the excavation head 1 proceeds.

  When the excavation progresses and the excavation head 1 reaches the upper end of the pillar-shaped improved pile P, first, as shown in FIG. Excavated soil G is excavated, and an excavation groove X is formed around the columnar improvement pile P. Here, in the example shown in FIG. 4, the excavating head 1 in which the outer diameter of the excavating wing 20 matches the diameter of the columnar improvement pile P is used, and as shown in FIG. It contacts the side of the improved pile P. As a result, the excavating head 1 is in a state of being fitted to the pillar-shaped improved pile P by the three leading claws 40, and occurrence of misalignment is prevented. As the excavation proceeds further, the small bit 30 in contact with the hard columnar improvement pile P does not escape to the surrounding soft soil, and cuts the columnar improvement pile P from the upper end. The excavation groove X formed by the leading claw 40 has a narrow ring shape as shown in FIG. 4C, but the excavated material (soil) by the leading claw 40 is between the leading claw 40. Since the excavated material is discharged upward from the space, the excavated matter does not accumulate in the excavated groove X. As a result, the excavation head 1 can crush the columnar improved pile P with high excavation efficiency while suppressing an increase in resistance of the leading claw 40 due to the excavated object.

  As described above, in the excavating head 1 of the present invention, the leading claw 40 excavates the soft soil around the columnar improved pile P before the small bit 30 crushing the columnar improved pile P. In order to reliably capture P, the columnar improved pile P can be effectively crushed without misalignment. Further, the excavated object excavated by the leading claw 40 is discharged upward between the leading claws 40 from the ring-shaped groove formed by the excavation of the leading claw 40, so that the excavated object does not become a resistance. Therefore, the excavation head 1 of the present invention can crush the columnar improved pile P with high excavation efficiency.

[Another embodiment]
The drilling head 1 according to the present invention is a book that prevents misalignment by fitting the leading claw 40 so as to suppress the outer peripheral surface of the columnar improved pile P, prior to the small bit 30 for cutting the columnar improved pile P. The configuration described in the above embodiment can be changed as long as the effects of the invention are exerted. Some such modifications will be described as another embodiment.

<Another embodiment 1>
Drawing 5 is an explanatory view of excavation head 1A of another embodiment. FIG. 5A is a perspective view of the excavation head 1A, and FIG. 5B is a front view of the excavation head 1A. The excavating head 1 </ b> A is obtained by changing the preceding claws 40 of the excavating head 1 shown in FIG. 1 to the preceding claws 40 </ b> X to 40 </ b> Z. In the excavating head 1 of FIG. 1, as shown in FIG. 3, by providing the reinforcing portion 42, the welding area to the outer peripheral portion 20 b of the excavating wing 20 is increased, and the fixing strength of the leading claw 40 is reinforced.

  On the other hand, in the excavating head 1A shown in FIG. 5, the leading claw 40X is welded and fixed to the outer peripheral portion 20b of the excavating wing 20X at a position from the tip 20a, and further from the welding portion 40a with the excavating wing 20X. And is welded and fixed also to the outer peripheral portion 20b of the excavation wing 20Y arranged in parallel with the excavation wing 20X. As described above, since the welding portion 40a with the outer peripheral portion 20b of the excavating wing 20X and the welding portion 40b with the outer peripheral portion 20b of the excavating wing 20Y are welded, the fixing strength of the leading claw 40X is strong. It becomes something. Therefore, the leading claw 40X can have a simple rod-like structure without a reinforcing portion. Similarly to the leading claw 40X, the leading claw 40Y is welded at two places: an outer peripheral portion 20b of the excavating wing 20Y and an outer peripheral portion 20b of the excavating wing 20Z arranged in parallel with the excavating wing 20Y. And the outer peripheral portion 20b of the excavator 20X arranged in parallel with the excavator 20Z are welded. Therefore, the leading claws 40Y and 40Z can also have a simple rod-like structure without a reinforcing portion.

<Another embodiment 2>
In the example shown in FIG. 1, three excavating wings 20 are provided, and three excavating claws 40 are provided as a whole of the excavating head 1 by attaching one leading claw 40 to each excavating wing 20. However, the excavating head 1 of the present invention may be any one that prevents misalignment by fitting the at least three leading claws 40 so as to suppress the outer peripheral surface of the columnar improvement pile P. By providing two excavating wings 20 and attaching two leading claws 40 to each of the excavating wings 20, four leading claws 40 may be provided as a whole of the excavating head 1. Even in such a configuration, misalignment can be prevented by fitting the four leading claws so as to suppress the outer peripheral surface of the columnar improved pile P.

<Another embodiment 3>
In the excavating head 1 shown in FIG. 1, when the radius of rotation of the inner surface of the leading claw 40 is R and the radius of the columnar improvement pile is r, the following relational expression (2):
1 ≦ R / r ≦ 2/3 ^1/2 (2)
You may be comprised so that may be satisfied. If R / r is within the above range, the distance between the leading claws 40 does not exceed the diameter of the pillar-shaped improved pile, so that a large misalignment is likely to occur from the state in which the leading claw 40 is fitted to the pillar-shaped improved pile P. In this case, the inner surface of any one of the three leading claws 40 always comes into contact with the pillar-shaped improved pile P, and the misalignment can be suppressed. When R / r is smaller than 1, the leading claw 40 does not fit into the column-shaped improved pile P, and there is a possibility that a part of the column-shaped improved pile P cannot be cut by the small bit 30. If R / r is greater than 2/3 ^1/2 , the distance between the leading claws 40 exceeds the diameter of the pillar-shaped improved pile P, and there is a large misalignment from the state where the leading claws 40 are fitted to the pillar-shaped improved pile P. When this is likely to occur, there is a risk that none of the preceding claws 40 will contact the columnar improvement pile P.

  The excavation head of the present invention can be used for crushing columnar improved piles constructed in ground improvement work, but it can also be used for crushing other underground buried objects if it is a columnar underground buried object. .

Reference Signs List 1 excavating head 4 auger rod 10 rotating shaft 20 excavating wing 20a end of excavating wing 20b outer peripheral portion of excavating wing 30 small bit 32a tip of small bit 40 leading claw 41a tip of leading claw 41b inclined surface of leading claw P Column-shaped improved pile

Claims (6)

A drilling head that is attached to an auger rod and crushes a columnar improved pile buried underground,
A rotating shaft attached to the auger rod,
At least three spiral excavation wings provided around the rotation axis;
A small bit attached to the end of the excavation wing in the excavation direction,
An excavating head comprising: a leading claw attached to an outer peripheral portion of the excavating wing, the tip of which protrudes in the excavating direction from the tip of the small bit.   The excavation head according to claim 1, wherein a tip of the leading claw protrudes from a tip of the small bit in an excavation direction by 10 to 30 cm.   The excavation head according to claim 1, wherein the leading claw has a tip with a turning radius larger than a radius of the columnar improvement pile. The rotation radius R of the leading claw on the inner surface closest to the rotation axis and the radius r of the columnar improvement pile are represented by the following relational expression (1):
1 ≦ R / r ≦ 1.1 (1)
The drilling head according to any one of claims 1 to 3, which satisfies the following.   The excavation head according to claim 3, wherein the leading claw has an inclined surface inclined from a tip end toward the excavation wing.   The drilling head according to any one of claims 1 to 5, wherein the small bit is a conical bit having a bit body rotatably mounted.

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