JP2016135969A - Casing segment used in micro pile method and micro pile method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a depth of a hole bored in a boring process to be accurately measured when a pressured water bearing stratum in a weak stratum is bored.SOLUTION: A casing segment 10 comprises a boring cutter 12, a water stop member 14 and a connection part 16. The boring cutter 12 is disposed on a tip outer peripheral part of the casing segment 10. The water stop member 14 blocks a space inside the boring cutter 12 in a radial direction. The water stop member 14 has a large diameter cylindrical part 20 and a small diameter cylindrical part 22. One end face of the large diameter cylindrical part 20 in an axial direction is an apical surface 1402 positioned inside a tip of the boring cutter 12. One end face of the small diameter cylindrical part 22 distant from the large diameter cylindrical part 20 is an inner face 1404 positioned inside the casing segment 10. A tooth part 24 for boring is formed on the apical surface 1402.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a casing segment used in a micropile method and a micropile method.

The micropile construction method is a generic name for small-sized cast-in-place piles with a diameter of 300 mm or less, for reasons such as being sufficient with compact construction equipment, being able to be constructed in a narrow space, and being able to be constructed without stopping the functions of existing structures. It is used for various purposes including seismic reinforcement of existing structures, ground reinforcement, and stabilization of slopes.
In the micropile method, first, the first rod having a drilling drill attached to the tip is inserted into the first casing segment whose outer periphery is the outer drilling cutter. A step of drilling while rotating the casing segment and the rod and injecting water is performed.
Then, at each predetermined depth, the next casing segment is detachably connected to the base end of the casing segment, and the next rod is detachably connected to the base end of the rod. A process of drilling while rotating the rod and injecting water is performed.
Also, once the drilling hole is pulled out from the inside of the casing segment together with the rod at a predetermined depth, the measuring tape with a weight attached to the tip is suspended in the water inside the casing segment, and the weight reaches the bottom of the hole. At that time, the measuring tape is read and the depth of the drilled hole is measured.
Since the length of the casing segment is known in advance, the depth of the hole can be estimated from the sum of the lengths of the joined casing segments. In order to confirm whether or not, it is necessary to actually measure the depth of the drilled hole.
After actually measuring the depth of the hole, the drilling process is performed again by inserting the drilling drill together with the rod into the casing segment.

Next, when the drilled hole reaches a predetermined depth, a step of pulling out the drill drill together with the rod from the inside of the casing is performed.
Next, if necessary, a reinforcing material is disposed inside the casing over the entire length of the casing.
Next, a step of filling the inside of the casing with the grout material and pulling out the casing by a predetermined length while increasing the pressure of the grout material is performed.

Patent No. 4010383

However, if the stratum where the tip of the first casing segment is located is a soft layer and is a confined aquifer, the excavated soil is the first along with the confined groundwater contained in the confined aquifer. It flows into the casing cement from the opening at the tip of the casing segment.
In this case, in order to actually measure the depth of the drilled hole, even if a measuring tape with a weight attached to the tip is suspended inside the casing segment, the excavated soil flows into the casing cement. Since it stays on the soil and cannot reach the bottom of the hole, there is a disadvantage in accurately measuring the depth of the hole.
The present invention has been devised in view of the above circumstances, and an object of the present invention is to measure the depth of a hole drilled in a drilling step when drilling a pressurized aquifer with a soft layer. It is an object of the present invention to provide a casing segment and a micropile method that are used in a micropile method that is advantageous in accurately performing the above.

In order to achieve the above object, the invention according to claim 1 is a casing segment used in a micropile construction method in which a tip outer peripheral portion is a drilling cutter, and the casing segment has a radius of the drilling cutter. A water stop member that closes a space on the inner side in the direction, and the water stop member allows water to pass from the inside of the casing segment to the outside, and prevents water from passing from the outside to the inside; A drilling tooth portion provided on a front end surface of the water stop member positioned opposite to the inside of the casing segment, and the water stop member is detachably coupled to the casing segment, The water stop member is rotated integrally with the casing segment in a state where the water stop member is coupled to the casing segment, and in the axial direction of the casing segment. Wherein the coupling portion is moved in the body is provided.
The invention according to claim 2 is characterized in that the water flow portion extends between the tip end surface and an inner surface of the water stop member located inside the casing segment, and the casing is interposed in the water flow passage. And a check valve that allows water to flow from the inside of the segment to the outside and disables water from the outside to the inside.
According to a third aspect of the present invention, a plurality of the tooth portions extend radially outward from the tip surface at intervals in a circumferential direction of the tip surface from a location located at the center of the tip surface. Between these tooth parts, it is a recessed part extended in the radial direction outward of the said front end surface from the location located in the center of the said front end surface, and the said water passage is opened at the bottom part of the said recessed part. Features.
According to a fourth aspect of the present invention, the connecting portion is driven into the water stop member from an outer peripheral surface of the hole cutter, and the water stop member is hit from the inside toward the outside from the inside of the casing segment. It is configured to include a pin that is damaged by being broken.
According to a fifth aspect of the present invention, the connecting portion is provided on the casing segment and abuts against the water stop member to prevent the water stop member from moving in a direction from the front end to the base end of the casing segment. It is characterized by including a contact part.
According to a sixth aspect of the present invention, the first casing segment whose tip outer peripheral portion is a drilling cutter closes a space radially inward of the drilling cutter and allows passage from the inside of the casing segment to the outside. A water stop that has a water flow portion that allows water to pass from the outside to the inside, and is coupled to rotate integrally with the casing segment and to move integrally in the axial direction of the casing segment. The water-stopping member that is disposed opposite to the inside of the casing segment by providing a member, rotating the first casing segment while passing water from the inside of the first casing segment to the outside via the water-passing portion A tooth portion provided on the front end surface of the first casing segment is drilled by the drilling cutter, and a second case is formed at the base end of the first casing segment along with the drilling. When the singing segments are detachably connected, the casing segments are rotated while drilling holes, and the casing segments are successively added along with the drilling holes, and the drilled holes are drilled to a predetermined depth. Is filled with a grout material, and then the connection between the tip of the first casing segment and the water stop member is released, and the water stop member is left at the bottom of the drilled hole. The added casing segment is pulled out by a predetermined length while increasing the pressure.
According to a seventh aspect of the present invention, the coupling of the water stop member and the first casing segment is made by a pin driven into the water stop member from an outer peripheral surface of the hole cutter, and the added casing segment. When the grout material is filled in the interior of the casing, a reinforcing bar is inserted into the added casing segment, and the release of the connection between the tip of the first casing segment and the water stop member is stopped by the reinforcing bar. This is performed by hitting the water member downward to break the pin.

According to the first aspect of the present invention, since the groundwater and the excavated soil are prevented from entering the inside of the casing segment by the water stop member, the depth of the drilled hole is accurately measured. Is advantageous.
Moreover, since the coupling | bond part which couple | bonds a water stop member with a casing segment so that engagement / disengagement was possible was provided, a water stop member can be cut off from a casing segment in the stage where the function of a water stop member became unnecessary.
According to the second aspect of the present invention, it is advantageous to simply construct a water stop member that allows water to flow from the inside to the outside of the casing segment and disables water from the outside to the inside.
According to the third aspect of the present invention, it is advantageous to efficiently drill holes corresponding to the properties of the ground to be drilled.
According to the fourth aspect of the present invention, it is possible to leave the water stop member at the bottom of the drilled hole by a simple operation, which is advantageous in improving workability.
According to the fifth aspect of the present invention, in the drilling step, even if a force in the direction from the front end to the base end of the casing segment is applied to the water stop member, it is advantageous for firmly supporting the water stop member on the casing segment. It becomes.
According to the sixth aspect of the present invention, since the groundwater and the excavated soil are prevented from entering the casing segment by the water-stopping member, the depth of the drilled hole can be accurately measured. Is advantageous.
Further, since the water-stopping member can be separated from the casing segment by operating the coupling portion when the function of the water-stopping member becomes unnecessary, the step of pulling out the casing segment by a predetermined length, and the casing of the grout material This is advantageous in smoothly performing the step of pushing back by a predetermined amount.
According to the seventh aspect of the invention, it is possible to leave the water stop member at the bottom of the drilled hole by a simple operation, which is advantageous in improving workability.

It is sectional drawing of the front part of a casing segment. It is a perspective view of a water stop member. (A)-(G) are explanatory drawings of a micropile construction method.

Embodiments of a micropile construction method according to the present invention will be described below together with embodiments of casing segments with reference to the accompanying drawings.
First, the casing segment of the present embodiment will be described.
As shown in FIG. 1, an elongated hollow cylindrical steel casing segment 10 includes a hole cutter 12, a water stop member 14, and a coupling portion 16.
The hole-cutting cutter 12 is located at the outer periphery of the tip of the casing segment 10.
The hole-cutting cutter 12 has a cylindrical shape, a tip portion is a tooth portion, and a base inner peripheral surface is attached (fixed) to the tip of the casing segment 10.
A contact portion 18 is fixed to the inner peripheral portion of the hole cutter 12 or the inner peripheral portion of the tip of the casing segment 10.
In the present embodiment, the abutting portion 18 is annularly projected radially inward from the cylindrical portion 1802 attached (adhered) to the inner peripheral portion of the hole cutter 12 and the base end of the cylindrical portion 1802. An annular wall 1804.

The water blocking member 14 closes the space inside the hole cutter 12 in the radial direction. In the micropile method of the present invention, the drilling drill provided at the tip of the rod inside the casing segment 10 is omitted, and the water stop member 14 is provided instead of the drilling drill.
The water stop member 14 has a large diameter cylindrical portion 20 and a small diameter cylindrical portion 22.
One end surface in the axial direction of the large-diameter cylindrical portion 20 is a distal end surface 1402 positioned inside the distal end of the drilling cutter 12, and the end surface on the side away from the large-diameter cylindrical portion 20 of the small-diameter cylindrical portion 22. Is an inner surface 1404 located inside the casing segment 10.

As shown in FIG. 2, a tooth portion 24 for drilling is provided on the distal end surface 1402.
In the present embodiment, a plurality of tooth portions 24 extend in the radial direction from the center of the distal end surface 1402 at intervals in the circumferential direction of the distal end surface 1402, and four in the present embodiment. As shown in FIGS. 1 and 2, the center portion of the tip surface 1402 protrudes most and the height of the four tooth portions 24 decreases as the tip portion 1402 reaches the outer peripheral portion.
A space 2404 between the adjacent tooth portions 24 is a concave portion 2404 composed of two inclined surfaces 2402.
The tooth portion 24 functions mainly to scrape the soil when drilling the soft layer, and drills while crushing the ground by rotating the four tooth portions 24 when drilling the load support layer. To work. In addition, the shape of the tooth | gear part 24 can be considered variously, and conventionally well-known various structures are applicable.

As shown in FIG. 1, a recess 26 is formed from the end surface of the small-diameter cylindrical portion 22 on the side away from the large-diameter cylindrical portion 20 to the large-diameter cylindrical portion 20, and the hole 28 that connects the bottom of the concave portion 26 and the inclined surface 2402. Are provided at intervals in the circumferential direction of the recess 26. The hole 28 is opened at the boundary between the two inclined surfaces 2402 that is the bottom of the concave portion 2404 so that water is smoothly supplied to the hole. In the present embodiment, the hole 28 and the recess 26 constitute a water passage 30 that communicates the inside and the outside of the casing segment 10.
A valve seat 32 having an opening 3202 is provided at an intermediate portion in the depth direction of the recessed portion 26, and the opening 3202 is constantly biased by the spring 34 between the valve seat 32 and the bottom of the recessed portion 26. A sphere 36 is arranged. A non-return check that allows water to flow from the inside of the casing segment 10 to the outside by the valve seat 32, the spring 34, and the sphere 36 provided in the water passage 30, and prevents water from being passed from the outside to the inside of the casing segment 10. A valve 38 is configured.
In the present embodiment, a water passage portion 40 that allows water to flow from the inside of the casing segment 10 to the outside and disables water from the outside to the inside is constituted by the water passage 30 and the check valve 38. .

The coupling portion 16 removably couples the water stop member 14 to the casing segment 10 and rotates the water stop member 14 integrally with the casing segment 10 in a state where the water stop member 14 is coupled to the casing segment 10. The casing segment 10 is moved integrally in the axial direction.
The coupling portion 16 includes a pin 1602 and an annular wall 1804 of the contact portion 18.
The pins 1602 are driven into the water stop member 14 from a plurality of locations spaced in the circumferential direction of the outer peripheral surface of the hole cutter 12.
That is, the small-diameter cylindrical portion 22 is inserted into the center hole of the annular wall 1804, and the pin 1602 is in a state where the pin 1602 is in the state of contacting the annular wall 1804 with the end face 23 between the small-diameter cylindrical portion 22 and the large-diameter cylindrical portion 20. 12 is driven into the water stop member 14 from the outer peripheral surface.
The pin 1602 rotates the water stop member 14 integrally with the casing segment 10.
The pin 1602 is formed by the reinforcing member 42 (see FIGS. 3D and 3E) from the inside of the casing segment 10 in the axial direction of the casing segment 10 so that the large-diameter cylindrical portion 20 is separated from the annular wall 1804. It is damaged by hitting.
Further, the annular wall 1804 functions so as to contact the water stop member 14 and prevent the water stop member 14 from moving in the direction from the front end to the base end of the casing segment 10. The water stop member 14 is advanced into the ground integrally with the casing segment 10. The pin 1602 also functions to prevent the water stop member 14 from moving in the direction from the front end to the base end of the casing segment 10 in the same manner as the annular wall 1804. The member 14 is advanced into the ground integrally with the casing segment 10.

Next, a micropile method using the casing segment 10 of the present embodiment will be described with reference to FIG.
As shown in FIG. 3 (A), a first casing segment 10 is prepared in which the outer periphery of the tip is a hole cutter 12 and a water stop member 14 is provided.
Then, the first casing segment 10 is rotated while passing water from the inside of the first casing segment 10 to the outside via the water passing portion 40, and the soil is separated in the circumferential direction of the water stop member 14 by the tooth portion 24. A step of drilling with the hole cutter 12 is performed.
That is, the water injected into the first casing segment 10 is ejected from the front end surface 1402 (the hole 28 of the tooth portion 24) of the water stop member 14 to the excavated soil in front of the casing segment 10.
In this state, drilling is performed by the drilling cutter 12 while excavating soil is being scraped by the tooth portion 24.

Then, as shown in FIGS. 3B and 3C, every time the drilled hole 44 has a predetermined depth, the following elongated hollow cylindrical steel casing segment is formed at the base end of the casing segment 10. Steps of drilling the hole 44 with the hole cutter 12 and the tooth portion 24 while injecting water into the casing segment 10. Is done.
Further, the casing segments 10 are connected to each other using a casing joint (not shown). For example, a hollow cylindrical cylindrical joint (not shown) having an outer diameter larger than the outer diameter of the casing segment 10 is prepared, and the female thread on the inner peripheral surface of the casing joint is screwed to the male thread on the outer peripheral surface of the adjacent casing segment 10. By doing so, the casing segments 10 are connected.
The configuration of the casing joint is not limited to the above, and various conventionally known configurations can be used as the casing joint.

Each time the hole 44 reaches a predetermined depth, the water injection into the casing segment 10 is temporarily interrupted, and a measuring tape with a weight attached to the tip is suspended in the water inside the casing segment 10. When the inner surface 1404 is reached, the measuring tape is read and the depth of the drilled hole 44 is measured.
At this time, if the formation where the tip of the first casing segment 10 is located is the soft layer 46 and is a confined aquifer, the confined groundwater contained in the confined aquifer is the excavated soil. An attempt is made to enter the inside of the first casing segment 10 through the water passage portion 40 of the water stop member 14.
However, since the check valve 38 reliably prevents entry of the pressurized groundwater and the excavated soil, the excavated soil that has flowed into the casing cement causes the weight to remain on the excavated soil and reach the inner surface 1404 of the water stop member 14. It is possible to avoid such a situation that it cannot reach and the depth of the hole 44 cannot be measured accurately.
After measuring the depth of the hole 44, if the measuring tape is recovered, the casing segment 10 is rotated again while water is poured into the casing segment 10 to perform a drilling process.

Casing C is constituted by connecting a plurality of casing segments 10.
As shown in FIG. 3C, if the drilled hole 44 passes through the soft layer 46 and reaches a predetermined depth of the load support layer 48, a reinforcing material such as a reinforcing bar 42 is added as necessary. The casing C is disposed over the entire length of the casing C.
Next, as shown in FIG. 3D, the grout material G is filled into the casing C using a tremy tube (not shown).
As the grout material G, cement milk, mortar material, or a concrete material mixed with a small diameter aggregate can be used.
When the grout material G is filled in the casing C, the intrusion of groundwater into the casing C is prevented by the grout material G even if the water blocking member 14 is removed.

If the grout material G is filled in the casing C, the reinforcing bar 42 is inserted into the casing C, and the water stop member 14 is hit downward by the reinforcing bar 42 to break the pin 1602. The first casing segment 10 Release of the connection between the tip of the water stop member 14 and the water stop member 14 is released.
Thereafter, the water stop member 14 remains at the bottom of the hole 44 that has been drilled.

Next, as shown in FIG. 3E, a step of pulling out the casing C, that is, a step of pulling out the casing segment 10 is performed while the grout material G is injected under pressure into the casing C.
It is desirable that the grouting material G be pressed at such a pressure that the grouting material G comes into close contact with the wall surface of the hole 44 that has been drilled, and the joining state between the grouting material G and the ground becomes strong.
When the upper end of the lower casing segment 10 is positioned on the ground, the lower casing segment 10 is non-rotatably gripped and the upper casing segment 10 is pulled out. And the upper casing segment 10 is removed from the lower casing segment 10 together with the joint member.
A plurality of casing segments 10 positioned above are removed together with the joint member, and the lower end of the first casing segment 10 positioned at the lowest position is positioned at the bottom of the load support layer 48 as shown in FIG. When approaching the upper part, the extraction of the casing C is completed.

Next, as shown in FIG. 3 (F), a step of pushing the casing C back into the grout material G filled with the grout material G by a predetermined amount is performed, and the portion surrounded by the casing C, the casing A portion having an intermediate structure is created between the portion not surrounded by C.
And the pile body 50 which has 50 A of ground junction parts by the grout material G is obtained because the grout material G is hardened | cured.
Next, as shown in FIG. 3 (G), a steel bearing plate 52 is joined to the upper end of the casing C by welding to form a connection structure for connecting the pile head of the pile body 50 to the structure. Is done.

As described above, according to the present embodiment, the space on the radially inner side of the hole cutter 12 is closed in the casing segment 10 to allow water to flow from the inside of the casing segment 10 to the outside. A water-stop member having a water-passing portion 40 that cannot pass water into the interior, and a tooth portion 24 for drilling provided on the distal end surface 1402 of the water-stop member 14 positioned opposite to the inside of the casing segment 10. 14 was provided.
Therefore, when drilling the pressurized aquifer with the soft layer 46, when measuring the depth of the drilled hole 44 by dropping a measuring tape with a weight at the tip into the interior of the casing segment 10 In addition, since the water-stopping member 14 prevents the pressurized groundwater and excavated soil from entering the casing segment 10, it is advantageous in accurately measuring the depth of the drilled hole 44.
In addition, since the coupling portion 16 for detachably coupling the water stop member 14 to the casing segment 10 is provided, the water stop member 14 can be separated from the casing segment 10 when the function of the water stop member 14 becomes unnecessary. it can.
Therefore, a step of pulling out a predetermined length of the casing segment 10 while increasing the pressure of the grout material G filled in the drilled hole 44 and a grout material in which the grout material G is pressurized and filled are extracted. This is advantageous in smoothly performing the step of pushing back a predetermined amount into G.

Further, according to the present embodiment, the water flow portion 40 is interposed between the water passage 30 extending between the tip end surface 1402 and the inner surface 1404 of the water stop member 14 located inside the casing segment 10, and the water flow passage 30. And a check valve 38 that allows water to flow from the inside of the casing segment 10 to the outside and disables water from the outside to the inside.
Therefore, it is advantageous in simply configuring the water stop member 14 that allows water to flow from the inside of the casing segment 10 to the outside and disables water from the outside to the inside.

Further, according to the present embodiment, a plurality of tooth portions 24 extend radially outward of tip surface 1402 from the position located at the center of tip surface 1402 at intervals in the circumferential direction of tip surface 1402. Between these tooth portions 24, there is a recess 2404 extending radially outward from the tip surface 1402 from a position located at the center of the tip surface 1402, and the water passage 30 opens at the bottom of the recess 2404. ing.
Therefore, the tooth portion 24 mainly functions to scrape the soil when the soft layer 46 is drilled, and when the load supporting layer 48 is drilled, the plurality of tooth portions 24 rotate to break the ground. Therefore, it is advantageous in efficiently drilling according to the properties of the ground to be drilled.

Further, according to the present embodiment, the coupling portion 16 is driven into the water stop member 14 from the outer peripheral surface of the hole cutter 12, and the water stop member 14 is beaten from the inside of the casing segment 10 toward the outside from the inside. It is configured to include a pin 1602 that is broken by being broken.
Therefore, it is possible to leave the water-stopping member 14 at the bottom of the drilled hole 44 by a simple operation, which is advantageous in improving workability.
Note that various known configurations can be employed for the coupling portion 16, but the embodiment is advantageous for simple configuration.

Further, according to the present embodiment, the coupling portion 16 is provided in the casing segment 10 and abuts against the water stop member 14 to prevent the water stop member 14 from moving in the direction from the front end to the base end of the casing segment 10. The abutting portion 18 is configured to be included.
Therefore, even if a force in the direction from the front end to the base end of the casing segment 10 is applied to the water stop member 14 in the hole drilling step, it is advantageous to firmly support the water stop member 14 on the casing segment 10.

DESCRIPTION OF SYMBOLS 10 Casing segment 12 Hole cutter 14 Water stop member 1402 Tip surface 16 Connection part 1602 Pin 18 Contact part 24 Tooth part 2404 Recess 30 Water passage 40 Water passage part 42 Reinforcement 44 Drilled hole C Casing G Grout material

Claims (7)

It is a casing segment used in the micropile method in which the outer periphery of the tip is a drilling cutter,
The casing segment includes a water stop member that closes a space on a radially inner side of the drilling cutter,
The water stop member includes a water passing portion that allows water to pass from the inside of the casing segment to the outside and disables water from the outside to the inside, and the stop that is located opposite to the inside of the casing segment. And a tooth portion for drilling provided on the tip surface of the water member,
The water stop member is detachably coupled to the casing segment, and the water stop member is rotated integrally with the casing segment in a state where the water stop member is coupled to the casing segment and the axial direction of the casing segment. Is provided with a coupling part that moves together.
A casing segment used in a micropile construction method. The water flow portion includes a water passage extending over the tip end surface and an inner surface of the water stop member located inside the casing segment, and a passage from the inside of the casing segment to the outside interposed in the water passage. And a check valve that allows water to flow from the outside to the inside.
The casing segment used in the micropile method according to claim 1. A plurality of the tooth portions extending radially outward from the tip surface at intervals in a circumferential direction of the tip surface from a location located at the center of the tip surface;
Between these teeth, it is a recess extending radially outward of the tip surface from a location located at the center of the tip surface,
The water passage opens at the bottom of the recess,
The casing segment used in the micropile method according to claim 2. The coupling portion includes a pin that is driven into the water stop member from the outer peripheral surface of the hole cutter, and is broken when the water stop member is struck from the inside toward the outside from the inside of the casing segment. Consists of
The casing segment used by the micropile method of any one of Claims 1-3 characterized by the above-mentioned. The coupling portion includes a contact portion that is provided in the casing segment and prevents the water stop member from moving in a direction from the front end to the base end of the casing segment by contacting the water stop member. Yes,
The casing segment used by the micropile method of any one of Claims 1-4 characterized by the above-mentioned. In the first casing segment whose tip outer peripheral portion is a drilling cutter, a space on the radially inner side of the drilling cutter is closed to allow water to flow from the inside of the casing segment to the outside, and from the outside A water stop portion having a water passing portion that prevents water from passing through the inside and rotating integrally with the casing segment and coupled so as to move integrally in the axial direction of the casing segment;
The first casing segment is rotated while passing water from the inside of the first casing segment to the outside via the water flow portion, and the tip end surface of the water stop member positioned opposite to the inside of the casing segment Drilling with the tooth part provided and the cutter for hole drilling,
Along with the drilling, a second casing segment is detachably connected to the base end of the first casing segment, and the casing segments are drilled while rotating. Thereafter, the casing segments are sequentially added along with the drilling. Continue
Once drilled to a predetermined depth, grout material is filled into the added casing segment,
Next, the connection between the tip of the first casing segment and the water stop member is released,
The water stop member is left at the bottom of the drilled hole, and the added casing segment is pulled out by a predetermined length while increasing the pressure of the grout material.
A micropile construction method characterized by this. The connection between the water stop member and the first casing segment is made by a pin driven into the water stop member from the outer peripheral surface of the drilling cutter,
When the grout material is filled in the added casing segment, a reinforcing bar is inserted into the added casing segment,
Release of the connection between the tip of the first casing segment and the water stop member is performed by hitting the water stop member downward with the reinforcing bar to break the pin.
The micropile construction method according to claim 6.

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