JP2019148105A - Gap obturator used in micropile construction method and micropile construction method using the same - Google Patents

Abstract

To provide a gap obturator used in a micropile construction method capable of efficiently performing pressure injection of a grout material in the final process of the micropile construction method, and the micropile construction method using the gap obturator.SOLUTION: A grout material G is supplied into a bag body 26 as a filler from a tube body 28, the bag body 26 is changed from a contracted state to an expanded state, an inner peripheral portion 2604 of the bag body 26 is brought into close contact with the entire circumference of an outer peripheral surface of a casing C, and an outer peripheral portion 2606 of the bag body 26 is brought into close contact with the entire circumference of an inner peripheral surface of a hole 16 that has been drilled. Since a soft layer 30 is a clay soil system, the outer peripheral portion 2606 of the bag body 26 bites into the inner peripheral surface of the drilled hole 16 in the expanded state of the bag body 26, and an annular gap S formed in the soft layer 30 and a load support layer 32 is completely closed and is surely cut off from the atmosphere.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a gap obturator used in a micropile construction method and a micropile construction method using the gap obturator.

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 end of the casing segment via a joint member and added, and the next rod is detachably connected to the end of the rod. The process of adding holes, rotating the casing segment and the rod, and drilling while injecting water is performed.
The outer diameter of the outer drilling cutter is larger than the outer diameter of the casing segment in consideration of the outer diameter of the joint member. After drilling, there is an annular gap between the drilling wall surface and the outer peripheral surface of the casing segment. It is formed.
When a plurality of casing segments are connected to form a casing, and the drilled hole passes through the soft layer and reaches a predetermined depth of the load support layer, the drill with the rod is removed from the inside of the casing. A drawing process is performed.
Then, if necessary, a reinforcing material such as a reinforcing bar is disposed inside the casing over the entire length of the casing.

Next, the grout material is filled into the casing using a grout hose.
As the grout material, cement milk, mortar material, or a concrete material mixed with a small diameter aggregate can be used.
Next, a step of pulling out the casing while pressure-injecting the grout material into the casing, that is, a step of pulling out the casing segment is performed.
It is desirable that the grouting material be pressed under such a pressure that the grouting material is in close contact with the wall surface of the drilled hole and the bonding state between the grouting material and the ground becomes strong.
When the plurality of upper casing segments are removed together with the joint member and the lower end of the first casing segment located at the lowest position approaches the uppermost portion of the load support layer, the drawing of the casing is completed.

Next, the step of pushing back the grout material by a predetermined amount into the grout material pressure-filled with the grout material is performed, and the part surrounded by the casing and the part not surrounded by the casing are In between, create a part with an intermediate structure.
And the pile body by which the ground junction part by the grout material was formed in the load support layer is obtained by hardening a grout material.
Next, a steel bearing plate is joined to the upper end of the casing by welding to form a connection structure for connecting the pile head of the pile body to the structure.

  By the way, when the ground is soft ground, the hole drilled by the outer drilling cutter on the outer periphery of the tip of the first casing segment and the drilling drill is broken and the wall surface of the hole collapses during drilling. Since the annular gap between the inner peripheral surface of the hole and the outer peripheral surface of the casing is closed, pressure can be applied to the grout material inside the casing in the final step.

Patent No. 4010383

However, when the location to be drilled is clayey ground or rock, the inner peripheral surface of the drilled hole is less likely to collapse, and after drilling, the inner peripheral surface of the drilled hole and the casing segment An annular gap is always ensured between the outer peripheral surface of each other.
Therefore, in the final process, pressure cannot be applied to the grout material, and a joint portion in which the grout material and the ground are firmly joined cannot be formed immediately below the casing including the periphery of the lower end of the casing.
In order to eliminate such a situation, conventionally, the grout material is injected once, and when the hardening of the grout material is about to start, the grout material is injected again and pressure is applied to the grout material. There was a problem that the time could not be shortened and the micropile method could not be performed efficiently.
In order to eliminate such a situation, it is conceivable to use a highly viscous grout material. In this case, however, the conventional pump cannot be used, and a large pump must be introduced, which increases costs. Trouble occurs.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a simple structure for a hole to be drilled when the portion to be drilled is a clay soil or rock. Gap obturator used in the micropile method that can reliably close the annular gap between the peripheral surface and the outer peripheral surface of the casing, and can efficiently pressurize the grout material in the final step of the micropile method, and the gap The object is to provide a micropile construction method using an obturator.

In order to achieve the object, the invention according to claim 1 is a gap blockage used in a micropile method for closing an annular gap between an inner circumferential surface of a hole drilled by rotation of a casing and an outer circumferential surface of the casing. A reduced state of a contour in which a cross-sectional shape cut by a plane orthogonal to the extending direction of the drilled hole is larger than the cross-sectional shape of the casing and smaller than the cross-sectional shape of the drilled hole From the reduced state to the expanded state, and the gap closing member that is variable to an expanded state that is in close contact with the entire circumference of the outer peripheral surface of the casing and the entire circumference of the inner peripheral surface of the drilled hole. And expansion means.
The invention according to claim 2 is characterized in that the gap closing member is formed of a foldable material and is formed into an annular bag shape through which the casing is inserted, and the expansion means is formed of the bag body. It is comprised including the filler which expands the said bag body by being supplied inside, and the pipe body which supplies the said filler to the said bag body.
According to a third aspect of the present invention, the bag body has an elongated shape along the longitudinal direction of the casing in the expanded state, and a large-diameter portion and a small-diameter portion are spaced apart in the longitudinal direction on the outer peripheral portion. It is characterized by being arranged alternately.
According to a fourth aspect of the present invention, there is provided a drilling step of passing through the soft layer and drilling to a predetermined depth of the load supporting layer while adding the casing segment, and a grout inside the casing formed by adding the casing segment. A filling step of filling the material, a drawing step of pulling out the casing until the lower end of the casing approaches the uppermost portion of the load supporting layer, and a pushing back step of pushing back the casing by a predetermined amount. In the micropile method for forming a joint in which the grout material and the load support layer are firmly joined at the position of the load support layer, the cross-sectional shape cut by a plane perpendicular to the extending direction of the drilled hole is the casing. From the reduced state of the contour that is larger than the cross-sectional shape and smaller than the cross-sectional shape of the drilled hole, A gap closing member that is variable to an expanded state that is in close contact with the entire circumference of the peripheral surface and the entire inner peripheral surface of the drilled hole, and an expansion means that changes the gap closing member from the reduced state to the expanded state. The gap closing member is provided, and the gap closing member is attached to the position of the casing located on the ground surface by the pulling process to bring the gap closing member into the reduced state, and the gap closing member is removed in the pushing back process. After being positioned in the hole, the gap closing member is in an expanded state by the expansion means, and the annular gap between the inner peripheral surface of the drilled hole and the outer peripheral surface of the casing is closed, The grout material is pressurized and injected into the casing segment.
According to a fifth aspect of the present invention, the gap closing member is made of a foldable material and is formed of a bag body formed in an annular bag shape through which the casing is inserted, and is located on the ground surface by the pulling process. A member that allows the bag body to change from the contracted state to the expanded state when the bag body is attached to the casing and the bag body is in the contracted state on the bag body in the contracted state. And the reduced state of the bag body is maintained on the casing.
According to a sixth aspect of the present invention, the expansion means includes a filler that expands the bag body by being supplied into the bag body, and a pipe body that supplies the filler to the bag body. It is comprised, The said filler is the same grout material as the said grout material with which the inside of the said casing is filled in the said filling process, It is characterized by the above-mentioned.

According to the first aspect of the present invention, when the portion to be drilled is a clay-based ground or rock, a desired pressure can be applied to the grout material in the final step of the micropile construction method. It is possible to reliably obtain a pile body having a strong ground joint part.
According to the second aspect of the present invention, when the gap closing device is composed of a bag body and a tube body having a simple structure, it can be easily manufactured at low cost, and can be easily mounted in the casing in a short time. This is advantageous in increasing the work efficiency of the pile method.
According to the third aspect of the invention, it is advantageous for reliably closing the annular gap between the inner peripheral surface of the drilled hole and the outer peripheral surface of the casing segment.
According to the invention described in claim 4, when the portion to be drilled is a clay-based ground or rock, a desired pressure can be applied to the grout material in the final step of the micropile construction method. It is possible to reliably obtain a pile body having a strong ground joint part.
According to the invention described in claim 5, it is advantageous to reliably arrange the gap closing member inside the drilled hole.
According to the invention described in claim 6, the grout material injected into the casing, the pump for injecting the grout material, etc. can be used as they are, and the expanded state of the bag can be formed at a low cost in a short time. Become

(A) is the front view which made the cross section the half part of the bag body which became the expanded state, (B) is BB sectional drawing of (A). It is the front view which made the bag body a contracted state and was mounted | worn with the casing. It is a partial cross section front view of the bag body which was in the expanded state in the drilled hole. (A)-(I) is explanatory drawing of the micropile construction method using a gap obturator.

Hereinafter, an embodiment of a gap obturator used in a micropile construction method according to the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 4F, the casing C is configured by connecting a plurality of casing segments 12 by joints 14, and the gap closing tool 20 of the present invention is used for the casing C.
As shown in FIGS. 1A and 1B, the gap closing tool 20 includes a gap closing member 22 and an expansion means 24.

In this embodiment, the gap closing member 22 is configured by a bag body 26 formed in a bag shape with a foldable material, and FIG. 1 shows the bag body 26 in an expanded state.
Any foldable material may be used as long as it is sufficient to prevent leakage of the filling material filled in the bag body 26, and various conventionally known materials can be used. Is used.
The bag body 26 has an annular shape surrounding the casing C and includes a center hole 2602 at the center thereof.
In the present embodiment, the bag body 26 includes an inner peripheral portion 2604 positioned around the center hole 2602 and an outer peripheral portion 2606 positioned outside the inner peripheral portion 2604.
A plurality of large-diameter portions 2606A and small-diameter portions 2606B are alternately provided on the outer peripheral portion 2606 of the bag body 26 at intervals in the axial direction of the center hole 2602 with the bag body 26 expanded. .
By configuring in this way, as shown in FIG. 3, the bag body 26 is in an expanded state and is effectively in close contact with the inner peripheral surface of the hole 16 drilled by the casing C. In some cases, the outer peripheral portion 2606 bites into the inner peripheral surface of the drilled hole 16, and the annular gap S between the inner peripheral surface of the drilled hole 16 and the outer peripheral surface of the casing C is more reliably blocked. It is planned to be able to.

As shown in FIG. 2, the bag body 26 has a cross-sectional shape cut by a plane perpendicular to the extending direction of the drilled hole 16 folded on the outer peripheral surface of the casing C and the cross-sectional shape of the hole 16 drilled. 3 and the expanded state in which the outer periphery of the casing C is in close contact with the entire periphery of the casing C and in close contact with the entire periphery of the inner peripheral surface of the drilled hole 16, as shown in FIG. Is formed.
Therefore, the bag body 26 is in a contracted state, the cross-sectional shape cut by a plane perpendicular to the extending direction of the drilled hole 16 is larger than the cross-sectional shape of the casing C and the cross-sectional shape of the drilled hole 16. Small outline.

As shown in FIG. 1A, the expansion means 24 includes a filler that expands the bag body 26 by being supplied into the bag body 26, and a tube body 28 that supplies the filler to the bag body 26. It is configured to include.
As the filler, any material such as water or air may be used as long as the bag body 26 is expanded from the contracted state. In the present embodiment, a grout material G that fills the inside of a casing 16 and a hole 16 drilled in a load support layer, which will be described later, is used as a filler.
The tube body 28 penetrates the upper end of the bag body 26, and the lower end opening of the tube body 28 is located inside the bag body 26.
In the place where the tube body 28 penetrates the upper end of the bag body 26, the tube body 28 and the bag body 26 are connected via a seal member 2802 so that the filler does not leak to the bag body 26. As the casing C moves downward, the tube body 28 and the bag body 26 are connected so as to move together.

Next, a micropile construction method using the gap obturator 20 will be described with reference to FIG.
As shown in FIG. 4 (A), when the micropile method is applied, the distal end outer peripheral portion is formed in the first elongated hollow cylindrical steel casing segment 12 having the outer hole drilling cutter 1202. The first rod 18 to which the drilling hole 1802 is attached is inserted into the outer drilling cutter 1202 and the outer drilling cutter 1202 and the drilling drill 1802 while rotating the casing segment 12 and the rod 18 and injecting water. The process of drilling the holes 16 in the soft layer 30 is performed.
In the present embodiment, the soft layer 30 is a viscous earth system, and when drilled, the inner peripheral surface of the drilled hole 16 does not collapse and the contour of the hole 16 is maintained.

  As shown in FIGS. 4B and 4C, every time the hole 16 reaches a predetermined depth, the following elongated hollow cylindrical steel casing segment 12 is inserted into the end of the casing segment 12 via a joint 14. The next rod 18 is detachably connected to the end of the rod 18 and added, the casing segment 12 and the rod 18 are rotated, and the outer cutting is performed while injecting water. A step of drilling the hole 16 with the hole cutter 1202 and the hole drill 1802 is performed.

Casing C is constituted by connecting a plurality of casing segments 12.
As shown in FIG. 4C, when the drilled hole 16 passes through the soft layer 30 and reaches a predetermined depth of the load support layer 32, the drill 1880 together with the rod 18 is inserted into the casing C. The process of drawing from is performed.
Next, a reinforcing material such as a reinforcing bar is disposed inside the casing C over the entire length of the casing C as necessary.

Next, as shown in FIG. 4D, the grout material G is filled into the casing C using a grout hose (not shown).
As the grout material G, cement milk, mortar material, or a concrete material mixed with a small diameter aggregate can be used.
Next, as shown in FIG. 4E, a step of pulling out the casing segment 12 while injecting the grout material G into the casing C, that is, a step of pulling out the casing C is performed.

The casing C is pulled out by holding the lower casing segment 12 in a non-rotatable manner when the upper end of the lower casing segment 12 is positioned in the vicinity of the ground among the upper and lower adjacent casing segments 12. The operation is performed by rotating the segment 12 and removing the upper casing segment 12 together with the joint 14 with respect to the lower casing segment 12.
The plurality of upper casing segments 12 are removed together with the joints 14, and the lower end of the first casing segment 12 located at the lowest position is placed on the uppermost portion of the load support layer 32 as shown in FIG. When approaching, the extraction of the casing C is completed.

Here, as shown in FIG. 2 and FIG. 4 (F), the bag body 26 of the gap obturator 20 is attached to the location of the casing segment 12 located on the ground.
That is, the casing segment 12 is inserted into the center hole 1602 of the annular bag body 26, and the lower end of the bag body 26 is fastened to the outer peripheral surface of the casing C by the fastener 34 so that the tube body 28 protrudes upward. Various conventionally known members such as a belt can be used as the fastener 34.

Then, as shown in FIG. 2, the bag body 26 is set in a contracted state, and a member 36 that allows the bag body 26 to change from the contracted state to the expanded state is wound around the bag body 26 in the contracted state. Is attached to the casing C while maintaining the reduced state.
Thus, when the casing C moves downward, the contracted state of the bag body 26 is maintained even if it comes into contact with the inner peripheral surface of the hole 16 that has been drilled, and the inside of the hole 16 in which the bag body 26 has been drilled. It is designed so that the movement at the can be made smoothly.
The member 36 that allows the bag body 26 to change from the contracted state to the expanded state is, for example, a string-like member made of paper that can be broken or stretchable rubber, or the bag body 26 in the contracted state. Various known materials and forms can be used, such as a bag-shaped member that covers the cover.
Note that the gap closing tool 20 may be attached to the casing segment 12 in advance when drilling, but the bag body 26 is reduced when the casing C is attached when the casing C is pulled out as in the present embodiment. This is advantageous in maintaining the state.

Next, as shown in FIG. 4G, a step of pushing back the casing C, to which the gap obturator 20 is attached, into the grout material G that has already been injected by a predetermined amount is performed.
If the casing C is pushed back by a predetermined amount, the bag body 26 is positioned inside the drilled hole 16 below the ground surface.

Next, as shown in FIG. 3 and FIG. 4 (H), the grout material G is supplied from the tube body 28 as a filler to the inside of the bag body 26, the bag body 26 is changed from the contracted state to the expanded state, and the bag body 26. The inner peripheral portion 2604 is closely attached to the entire circumference of the outer peripheral surface of the casing C, and the outer peripheral portion 2606 of the bag body 26 is closely attached to the entire periphery of the inner peripheral surface of the drilled hole 16.
In the present embodiment, since the soft layer 30 is a clay soil system, the outer peripheral portion 2606 of the bag body 26 is the inner peripheral surface of the drilled hole 16 as shown in FIG. The annular gap S formed in the soft layer 30 and the load support layer 32 is completely closed and is surely cut off from the atmosphere.

Next, the grout material G is pressurized and injected into the casing C to create a portion having an intermediate structure between the portion surrounded by the casing C and the portion not surrounded by the casing C.
The pressure injection of the grout material G into the casing C is performed at such a pressure that the grout material G is brought into close contact with the wall surface of the drilled hole 16 and the joining state between the grout material G and the ground becomes strong. It is desirable to be done.
In the present embodiment, the annular bag S formed in the soft layer 30 and the load support layer 32 is completely and reliably cut off from the atmosphere by the expanded bag body 26, so that the grout material G is pressurized to a desired pressure. And the joining state of the grout material G and the ground can be made strong as designed.
And as shown in FIG.4 (I), the pile body 40 which has the ground junction part 38 by the grout material G is obtained because the grout material G is hardened | cured.
Next, a steel bearing plate 42 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 40 to the structure.

Therefore, according to the present embodiment, when the portion to be drilled is a clay-based ground or rock, the inner peripheral surface of the drilled hole 16 is less likely to collapse, and after drilling, the hole is drilled. Although an annular gap S is always secured between the inner peripheral surface of the hole 16 and the outer peripheral surface of the casing segment 12, a desired pressure can be applied to the grout material G in the final step of the micropile method. Thus, it is possible to reliably obtain the pile body 40 having the strong ground joint portion 38 made of the grout material G.
Moreover, since the gap closing member 22 is composed of the bag body 26 and the pipe body 28 having a simple configuration, the gap closing member 22 can be easily manufactured at low cost, and can be easily mounted in the casing C in a short time. This is extremely advantageous in increasing the work efficiency of the construction method.

In addition, since the grout material G is used as a filler for changing the bag body 26 from the contracted state to the expanded state, existing equipment such as a grout material G to be injected into the casing C and a pump for injecting the grout material G is installed. It can be used as it is, and the expanded state of the bag body 26 can be formed at a low cost in a short time compared with the case where water or air is used as the filler.
Moreover, the bag body 26 and the pipe body 28 which are filled with the grout material G and are in an expanded state are buried, which is advantageous in securing the lateral resistance of the pile body 40 as compared with the case where water or air is used as the filler. It becomes.

In the present embodiment, the case where the bag body 26 is made of cloth has been described. However, the bag body 26 is formed of an elastic rubber material and is not filled with water, air, or the grout material G. The elastic member may be deflated and reduced around the casing C, and expanded by being supplied with the filler.
In the present embodiment, the case where the bag body 26 is attached to the casing C by the fastener 34 has been described. However, the bag body 26 in a reduced state is formed, and the bag body 26 is drilled by the tube body 28. The bag body 26 may be expanded in a predetermined position by being suspended in the hole 16 formed.
Further, the location where the gap closing member 22 is disposed is only required to be able to apply pressure to the grout material G in the final step, and therefore, at a location between the ground surface and the ground joint portion 38 above the ground joint portion 38. There is no limitation to the location of the embodiment.
Further, in the present embodiment, the case where the gap closing member 22 is configured by the bag body 26 has been described. However, the gap closing tool 20 may be of any structure that can close the annular gap S. For example, the gap closing member 22 There are also various mechanical structures known in the art as the gap closing device 20, such as using an annular shutter composed of a plurality of wings and capable of opening and closing the annular gap S and using an actuator for opening and closing the shutter as the expansion means 24. It can be adopted.

12 casing segment 14 joint 20 gap closing member 22 gap closing member 24 expansion means 26 bag body 2602 center hole 2604 inner peripheral part 2606 outer peripheral part 2606A large diameter part 2606B small diameter part 28 tubular body 30 soft layer 32 load support layer 34 fastener 38 Ground joint 40 Pile body C Casing G Grout material S Annular gap

Claims (6)

A gap closing tool used in a micropile method for closing an annular gap S between an inner peripheral surface of a hole drilled by rotation of a casing and an outer peripheral surface of the casing,
From the reduced state of the contour, the cross-sectional shape cut by a plane orthogonal to the extending direction of the drilled hole is larger than the cross-sectional shape of the casing and smaller than the cross-sectional shape of the drilled hole, A gap closing member variable to an expanded state in close contact with the entire circumference of the outer peripheral surface and the inner peripheral surface of the drilled hole;
Expansion means for changing the gap closing member from the reduced state to the expanded state;
A gap obturator used in a micropile construction method characterized by comprising: The gap closing member is formed of a foldable material, and is configured by a bag body formed in an annular bag shape through which the casing is inserted,
The expansion means includes a filler that expands the bag body by being supplied into the bag body, and a tube body that supplies the filler to the bag body.
The gap obturator used in the micropile method according to claim 1. The bag body has an elongated shape along the longitudinal direction of the casing in the expanded state, and a large-diameter portion and a small-diameter portion are alternately arranged on the outer peripheral portion at intervals in the longitudinal direction.
The gap obturator used in the micropile method according to claim 2. A drilling step of drilling to a predetermined depth of the load support layer while passing through the soft layer while adding the casing segment, and a filling step of filling a grout material inside the casing formed by adding the casing segment; A pulling step of pulling out the casing until the lower end of the casing approaches the uppermost part of the load supporting layer; and a pushing back step of pushing back the casing by a predetermined amount, and a grout material at a position of the load supporting layer immediately below the casing. In the micropile method of forming a joint where the load support layer and the load support layer are firmly joined,
The outer circumference of the casing is reduced from a reduced state of a contour in which a cross-sectional shape cut along a plane orthogonal to the extending direction of the drilled hole is larger than the cross-sectional shape of the casing and smaller than the cross-sectional shape of the drilled hole. A gap closing member that can be changed to an expanded state that is in close contact with the entire circumference of the surface and the inner circumferential surface of the drilled hole, and an expansion unit that changes the gap closing member from the reduced state to the expanded state. Provided a gap closure device,
At the location of the casing located on the ground surface by the extraction step, the gap closing member is attached and the gap closing member is in the reduced state,
After the gap closing member is positioned in the drilled hole in the push-back step, the gap closing member is expanded by the expanding means, and the inner peripheral surface of the drilled hole and the outer periphery of the casing Closing the annular gap S between the surfaces,
Pressure-injecting the grout material into the casing segment;
A micropile construction method characterized by this. The gap closing member is formed of a foldable material, and is configured by a bag body formed in an annular bag shape through which the casing is inserted,
When the bag body is attached to the location of the casing located on the ground surface by the extraction step and the bag body is in the reduced state,
A member that allows the bag body to change from the reduced state to the expanded state is wound on the bag body in the reduced state, and the reduced state of the bag body is maintained on the casing.
The micropile construction method according to claim 4. The expansion means includes a filler that expands the bag body by being supplied into the bag body, and a tube body that supplies the filler to the bag body.
The filler is the same grout material as the grout material filled in the casing in the filling step.
The micropile construction method according to claim 5, wherein:

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