JP4886894B1 - Method for extracting buried pile and foaming water generator - Google Patents

Abstract

[PROBLEMS] To promote drilling with minimal equipment and cost in pulling out buried piles, and to restore the ground of moderate strength.
A method for pulling a buried pile includes a step of foaming a foaming agent solution to generate foamed water, and a drilling casing when drilling a ground around the buried pile with a drilling casing. The step of spraying the foamed water onto the ground, and the step of holding and burying the buried pile by a holding means. Since the foamed water is sprayed onto the ground to form mud, the amount of water used can be reduced and the fluidized soil can be prevented from being diluted. Therefore, drilling can be promoted with a minimum amount of equipment and cost, and a ground with moderate strength can be restored.
[Selection] Figure 1

Description

  The present invention relates to a method for extracting a buried pile.

  When rebuilding a building, the existing building is dismantled and the foundation pile (buried pile) buried in the ground is pulled out. Patent Document 1 has a description related to a drawing work for buried piles.

  In the buried pile drawing work, ground drilling around the buried pile, removal of the buried pile, and refilling of a hole (hereinafter referred to as a buried hole) remaining after the buried pile is pulled out are performed. Drilling of the ground around the buried pile is performed by, for example, a drilling casing. The drilling casing is a steel tube having an inner diameter larger than the diameter of the buried pile, and a diamond bit and a liquid injection hole are provided at the tip. The drilling casing is installed so that the outer periphery of the tip portion surrounds the buried pile, and is driven to rotate. At the same time, water (hereinafter referred to as drilling water) is ejected from the spray hole at the tip. When the ground around the buried pile is melted by the drilling water and becomes muddy water, the drilling casing enters the muddy water ground by rotational force and its own weight, and drills while maintaining the hole wall. Thus, drilling of the ground around the buried pile is performed. At this time, if the ground has a lot of sand and gravel, it may be difficult to make the ground into muddy water while maintaining the hole wall only with drilling water. In such a case, the ground is made muddy with a suspension of clay mineral such as bentonite instead of drilling water, and drilling is performed.

  Next, after the hole-drilling casing has drilled to the bottom of the pile, the hole-drilling casing is pulled up, and then a wire is wound around the upper part of the buried pile, and the buried pile is pulled out by pulling up the wire. At this time, the fluidized soil is poured into the buried hole (poured) while pulling out the buried pile. In this way, the buried hole is backfilled while preventing the hole wall of the buried hole from collapsing and the ground around the construction site from sinking. And when a buried pile is pulled out, earth and sand will be further covered on fluidization processing soil. And the ground is restored when the fluidized soil is solidified.

JP-A-7-82744

  By the way, there are the following problems in the conventional method as described above in the work of pulling out the buried pile. First, a large amount of drilling water is required to make the ground muddy. Therefore, costs are required for equipment such as water and a large-capacity water tank. In particular, when a bentonite suspension is used instead of drilling water, a large amount of water and a large-capacity water tank are required to suspend the bentonite and a facility such as a stirrer (mixing plant or the like). Therefore, the cost further increases. Also, depending on the construction site, it may be difficult to provide such equipment due to space limitations.

  Next, when the fluidized soil is backfilled by using a large amount of drilling water, the fluidized soil is diluted with the drilling water. Then, solidification of a solidifying agent such as cement contained in the fluidized soil may be inhibited, and the strength of the restored ground may be reduced. When constructing a new building on the restored ground, it is necessary to drill the ground after the restoration again in order to provide buried objects such as foundation piles. However, in the ground where the strength has decreased, there is a risk that construction will be hindered, for example, the hole wall of the drilled buried hole collapses. In particular, it is known that bentonite, a clay mineral, acts to inhibit the solidification of cement in the fluidized soil. For these reasons, the strength of the ground may be further reduced. However, if the amount of solidifying agent such as cement is increased to maintain the strength of the ground, the cost will increase accordingly. Also, if the degree of solidification is too large, drilling becomes difficult when constructing a new pile, which may hinder construction.

  As a result of intensive studies, the inventor of the present invention has come up with a method for solving the above-described problems in the construction work for burying piles. That is, an object of the present invention is to provide a method for extracting a buried pile that can promote drilling with a minimum amount of equipment and cost, and can restore a ground having an appropriate strength.

  In order to achieve the above object, the buried pile drawing method according to the present invention includes a step of foaming a foaming agent solution to generate foamed water, and drilling a ground around the buried pile with a drilling casing. When doing, it has the process of spraying the said foaming water from the said hole-drilling casing to the said ground, and the process of hold | maintaining and pulling out the said buried pile by a holding means.

  According to the present invention, it is possible to promote drilling with a minimum amount of equipment and cost, and to restore a ground having an appropriate strength by injecting foamed water from the drilled casing onto the ground.

It is a structural example of the drilling apparatus which implements the drawing method of a buried pile in this embodiment. It is a figure explaining a drilling process. It is a figure which shows the transition of the state of the buried pile 30 and the buried hole 36 in which this is buried. It is a figure explaining the first half of the extraction process of a buried pile. It is a figure explaining the second half of the extraction process of a buried pile. It is a figure explaining the backfilling process of a buried hole. It is a figure explaining the ground restored in this embodiment. It is the table | surface which compared the construction results with the conventional construction method and this embodiment. The Example of the foaming apparatus 126 in the foaming water production | generation apparatus 12 is shown. It is a figure which shows the result of having implemented the standard penetration test with respect to the restored ground.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 is a configuration example of a drilling device for carrying out a method for pulling a buried pile in the present embodiment. FIG. 1A shows the overall configuration of the hole drilling device. Here, a configuration for drilling the ground around the buried pile is shown as an example of a concrete buried pile having a diameter of 1.2 m, a total length of 15 m, and a weight of 39 t.

  This drilling device 20 foams a foaming agent solution to generate foamed water, and when drilling the ground around the buried pile with the drilling casing, the foaming water from the drilling casing to the ground. And the step of injecting. For example, the hole drilling device 20 includes a hole casing 2, a leader 4 that guides the hole casing 2, and a motor 6 that is provided at the upper end of the reader 4 and that drives the hole casing 2 to rotate. Further, the hole drilling device 20 includes a foamed water generator 12 that generates foamed water, and a water conduit 14 for sending the foamed water generated by the foamed water generator 12 to the hole casing 2.

  The drilling device 20 is supported by the arm 8 of the mobile crane 10 in a state where the drilling casing 2 and the leader 4 are upright with respect to the ground. The drill casing 2 is suspended by the mobile crane 10 and is configured to be movable up and down along the leader 4. The drilling casing 2 is constituted by a steel tube having a diameter of 1.4 m, a total length of 20 m, and a weight of 7 t, for example. The drilled casing 2 has a foamed water injection hole 2a and a diamond bit (not shown) at its tip, and further has a conduit 2b for sending the foamed water from the end on the motor 6 side to the spray hole 2a. The conduit 2b is connected to the water conduit 14 at the end of the drilling casing 2 on the motor 6 side. Foamed water generated by the foamed water generating device 12 is pumped to the conduit 2b of the drilled casing through the water conduit 14. In this embodiment, the hole-drilling casing 2 injects foaming water from the injection hole 2a instead of the hole-drilling water, and drills the ground around the buried pile.

  FIG. 1B is a configuration example of the foaming water generator 12. The foaming water generating device 12 includes a water tank 122 that stores a foaming agent solution in which water and a foaming agent are mixed, a water sprayer (pump) 124 that takes out the foaming agent solution from the water tank 122 by a predetermined amount and sends the foaming agent solution to the foaming device 126. A compressor 128 that generates compressed air and sends it to the foaming device 126, a foaming device 126 that mixes the foaming agent solution and the compressed air to foam the foaming agent solution to generate foaming water, a sprinkler 124, and the compressor 128 And a generator 130 for supplying power.

  The water guide pipe 14 is connected to the tip of the foaming device 126. The water guide pipe 14 extends along the arm 8 of the crane 10, and is connected to the conduit 2 b of the drilling casing 2 through the motor 6. Foamed water is pumped by compressed air generated by the compressor 128 from the foaming device 126 to the injection hole 2a at the tip of the holed casing 2 through the water conduit 14 and the conduit 2b. And when drilling is performed, foaming water is injected from the injection nozzle 2a to the ground around the buried pile. With such a configuration, the foamed water foamed in the form of foam is sprayed on the ground. Then, the foamed water turns the ground into bubbles, for example, a mousse mud having a certain degree of viscosity (hereinafter, such mud is referred to as a bubble mud), and drilling with the drill casing 2 is performed.

  Here, each process of the extraction | drawer construction of the buried pile in this embodiment is demonstrated. 2-6, it divides into a drilling process, the extraction process of a buried pile, and a backfill process, and demonstrates.

  FIG. 2 is a diagram for explaining the hole drilling process. FIG. 2 (A) shows the cueing process of the buried pile. The excavator machine 10 a such as a backhoe drills the periphery of the buried pile 30 and cuees the upper portion of the buried pile 30. A cylindrical stand pipe 32 is installed around the upper portion of the buried pile 30 by a moving crane or the like.

  Next, as shown in FIG. 2B, the drilling device 20 is positioned and installed with respect to the stand pipe 32 by the mobile crane 10. The tip of the drilling casing 2 is inserted into the stand pipe 32 and installed such that the outer periphery of the tip covers the upper portion of the buried pile 30.

  Next, in FIG. 2 (C), the holed casing 2 rotates and the foamed water 2c is injected from the tip thereof. The foamed water 2c is sprayed on the ground around the buried pile 30. As a result, the ground around the buried pile 30 is softened and turned into mud. Then, the hole-drilling casing 2 enters the ground by the rotational force and its own weight (arrow 22).

  At this time, due to the action of the foaming agent contained in the foaming water, it is possible to reduce friction between the outer wall of the drilled casing 2 and the hole wall of the buried hole that has been drilled. Bubbles of foaming water enter between the soil grains and function as a water-impermeable water-stopping layer having a certain thickness, and have a so-called bearing effect. At this time, the bubble particle size is desirably 500 μm or less. This water stop layer opposes the groundwater pressure, thereby preventing the groundwater pressure from acting on the outer wall of the drilled casing 2. Further, the pressure of the cellular mud can counteract the earth pressure of the hole wall to be drilled and prevent the hole wall from collapsing. In this way, friction between the drilling casing 2 and the hole wall, or pressure due to groundwater pressure or earth pressure can be reduced, and drilling can be promoted.

  Further, the foaming water expands to a volume six times that of the foaming agent solution by foaming. Therefore, the ground can be made into a mud of mud without making the ground muddy like the case where a large amount of drilling water is used in the conventional construction method.

  As shown in FIG. 2D, the hole casing 2 enters the ground while rotating. The direction of rotation may be any direction, and the direction may be changed as appropriate. And when the front-end | tip of the drilling casing 2 reaches the position of the bottom part of the buried pile 30, drilling is completed. When the bottom of the buried pile 30 is widened to form an expanded bottom or a pile thickened part is partially formed, these are scraped off by a diamond bit provided at the tip of the drilled casing 2. Thereby, the buried pile 30 is cut off from the ground.

  Next, as shown in FIG. 2E, the hole casing 2 is pulled up to the original position (arrow 23). In this way, the drilling process is completed.

  Here, the state of the buried pile 30 will be described with reference to FIG. FIG. 3 shows the state transition between the buried pile 30 and the buried hole 36. FIG. 3A is a cross-sectional view showing the state of the buried pile 30 and the drilled buried hole 36 when the drilled casing 2 is pulled out in the step of FIG.

  Next, according to FIGS. 4 and 5, the buried pile drawing process will be described with reference to FIG. 3 as appropriate.

  Drawing 4 is a figure explaining the first half of the drawing process of an embedded pile. First, as shown in FIGS. 4A and 4B, a metal wire 34 is attached to the drilling casing 2, and the drilling casing 2 is inserted into the ground around the buried pile 30 again in this state. As shown in FIG. 4B, the wire 34 is provided with an annular portion 34 a, and the annular portion 34 a is attached to the distal end portion of the drilling casing 2. For example, the annular portion 34a is wound around the outside of the diamond bit 2d.

  Next, as shown in FIG. 4C, when the tip of the drilling casing 2 reaches the middle of the buried pile 30 or closer to the upper part than the middle, the mobile crane 8 is driven to move the drilling casing 2 in the horizontal direction. Vibrate. Thereby, the annular portion 34 a of the wire 34 is detached from the drilling casing 2 and is hung on the outer periphery of the buried pile 30. Next, as shown in FIG. 4 (D), the annular portion 34a of the wire 34 is left in the ground, and the holed casing 2 is pulled up from the ground.

  FIG. 5 is a diagram for explaining the latter half of the buried pile drawing process. First, as shown in FIG. 5 (A), the wire 34 is lifted together by the mobile cranes 10 and 10b. Here, as shown in FIG. 5B, the annular portion 34a of the wire 34 is doubled in advance and formed in a hollow shape. Thereby, when pulling up the wire 34, the inner diameter of the annular portion 34 a is narrowed and is surely wound around the buried pile 30. Here, the wire 34 and the mobile cranes 10 and 10 b correspond to “holding means”.

  And as shown in FIG.5 (C), the edge part of the wire 34 is pulled up with the mobile cranes 10 and 10b, and the buried pile 30 around which the wire 34 was wound is pulled out. At this time, the ground around the buried pile 30 is made of cellular mud by foaming water, and friction with the buried pile 30 is reduced. Moreover, since the ground water pressure and the earth pressure of the hole wall of the buried hole 36 are suppressed and the collapse of the hole wall is prevented, the drawing is facilitated.

  Further, at the same time as or before the lifting of the buried pile 30, fluidized soil 38 is placed in the buried hole 36 in the stand pipe 32. The fluidized soil is a stable soil having fluidity and self-hardness, and is for restoring the ground after the completion of drawing the pile. As the fluidized soil 38, a publicly known material is used which is produced by adding soil and a cement-based solidifying agent to water and mixing them. The fluidized soil is, for example, pumped by a pump (not shown) and placed in the buried hole 36.

  FIG. 3B shows a state in which the fluidized soil 38 is placed in the stand pipe 32 before lifting. When the buried pile 30 is pulled out by the wire 34, the fluidized soil 38 flows into the drilled buried hole 36 as shown in FIG. Thereby, since the negative pressure in the buried hole 36 is canceled, the buried pile 30 can be pulled out more easily. At the same time, the fluidized soil 38 is filled to prevent the hole wall of the buried hole 36 from collapsing.

  Returning to FIG. 5C, when the buried pile 30 has a length of a certain length and cannot be lifted at once by the mobile cranes 10, 10 b, it is cut by the wire saw 40 in the middle of the buried pile 30. Only the cut upper part may be pulled out. The portion left in the ground can be extracted by performing the steps of FIGS. 5A to 5C again.

  FIG. 6 is a diagram for explaining a process of backfilling a buried hole. After the buried pile 30 is pulled out, as shown in FIG. 6 (A), the excavator 10a puts earth and sand 39 for backfilling into the stand pipe 32 and refills the drilled buried hole 36. When the introduction of the earth and sand 39 is completed, the stand pipe 32 is removed by the mobile crane 10 as shown in FIG. Thus, the backfilling is completed.

  The state at this time is shown in FIG. In the buried hole 36 that has been backfilled, the fluidized soil 38 solidifies over time. At this time, in this embodiment, the amount of water used for drilling can be reduced to a small amount by drilling using foaming water instead of drilling water. Therefore, the amount of water remaining in the buried hole 36 is much smaller than when a suspension such as drilled water or bentonite is used. For this reason, the degree to which the fluidized soil 38 is diluted is smaller than in the conventional method. Therefore, solidification of the cement-based solidifying agent contained in the fluidized soil 38 is promoted, and the strength of the ground restored after backfilling can be improved. On the other hand, since the strength of the ground can be improved without increasing the amount of solidifying agent, it is possible to restore the ground with a strength (N value 5-30) that is not soft (N value 0-1) and can be drilled later.

  FIG. 7 is a diagram for explaining the ground restored in the present embodiment. In FIG. 7A, a plan view 36a and a cross-sectional view 36b of the buried hole that is backfilled are indicated by hatched areas. In the extraction work of buried piles, there are cases where buried objects such as foundation piles are provided for the new structure on the ground restored by refilling the buried holes. In addition, a buried hole may be newly drilled in a region overlapping with the buried hole that has been backfilled. Here, the plan view 37a and the cross-sectional view 37b of the new buried hole are indicated by dotted lines overlapping with the plan view 36a and the cross-sectional view 36b of the buried hole that has been refilled.

  In the conventional construction method, since the amount of water contained in the drilling water or bentonite suspension is large, the fluidized soil is diluted and the fluidized soil is not sufficiently solidified. Therefore, as shown in FIG. 7B, the ground of the buried holes 36a and 36b backfilled collapses into the new buried holes 37a and 37b (arrow 39), making it difficult to construct a new foundation pile.

  The difficulty is that when drilling, it runs in the direction of the weak (buried part) and requires technology and time to dig vertically, and even if dug, the buried part collapses, processing costs for that part, and the creation of new piles in the cavity This is because there is an additional cost for putting concrete.

  On the other hand, according to this embodiment, after the buried hole is backfilled, the ground having sufficient strength is restored. Therefore, as shown in FIG. 7C, even when the new buried holes 37a and 37b are cut, the ground of the buried buried holes 36a and 36b is maintained in a restored state. The hole wall of the buried hole 37 does not collapse. Therefore, it is possible to construct a new foundation pile like a normal ground. Further, there is no additional cost as described above.

  Hereinafter, examples of the foaming agent, the foaming agent solution, and the foaming apparatus 126 in the present embodiment will be described. Here, in the same manner as described above, an example in which the drilled casing 2 having a diameter of 1.4 m, a total length of 20 m, and a weight of 7 t is used to pull out the buried pile 30 having a diameter of 1.2 m, a total length of 15 m, and a weight of 39 t. Is shown.

[Foaming agent]
As the foaming agent, for example, one containing at least one of a surfactant system, a protein system and a resin soap system is suitably used. Here, in the case of a surfactant system, the content of the surfactant in the foaming agent is 1.0% to 2.0%, which can secure a pressure that can counter the groundwater pressure and promote drilling. This is desirable.

  Here, the specific example of the commercially available foaming agent which can acquire said effect in a present Example is shown. First, as an example of a surfactant-based foaming agent, “Geo Heart 2” manufactured by Aso Foam Cleat, “OFA-2” manufactured by Kumiko Onoda, “Sumishield A” manufactured by Sumitomo Osaka Cement, “Fine Foam 606” manufactured by Pozzolith Products, For example, “Floric FA100” manufactured by Floric is available. Examples of protein-based foaming agents include “AP foam” manufactured by Kizaitect, “Mal P” manufactured by CELLULAR concrete, and the like. Examples of the resin soap foaming agent include rosin soap. However, embodiments of the present invention are not limited to these examples.

[Foaming agent solution]
A foaming agent solution is produced | generated by mixing 1-2 L foaming agent with respect to 1000 L of water, for example. In a present Example, the foaming water by this foaming agent solution can be sprayed 5L per minute, 300L per hour, and the ground around the buried pile 30 can be drilled. In the conventional construction method, when drilling with water-only water, 30 to 60 L per minute and 1800 to 3600 L per hour are consumed. Thus, according to this embodiment, the amount of water used can be reduced to 1/6, and water and equipment costs can be reduced. And the dilution of fluidization processing soil can be prevented and the strength fall of the restored ground can be prevented.

[Comparison of construction results]
FIG. 8 shows the relationship between the soil soil in which drilling is performed, the concentration of the blowing agent solution, and the drilling speed. FIG. 8 (A) shows a comparison in cohesive soil. Here, the drilling speed in the case of using drilling water and the drilling speed in the case of using foaming water are shown as the drilling depth (unit: m) for each hour. Here, the concentration of the foaming agent solution used to generate the foaming water is 1/1000 (that is, 1 L of foaming agent mixed into 1000 L of water). As shown in the figure, for example, in the case of drilling 15m, the drilling water takes about 4 hours, but the foaming water can be drilled in 3 hours. Further, for example, in the case of drilling 30 m, the drilling water takes about 8 hours, but the foaming water can be drilled in 6 hours. Thus, according to this embodiment, for example, the drilling time per buried pile can be reduced by about 25%.

  FIG. 8B shows a comparison in the gravel layer. Here, the drilling speed when using drilling water and the drilling speed when using two concentrations of foamed water are shown. The concentration of the blowing agent solution used here is 1/1000 (1 L of blowing agent for 1000 L of water) and 2/1000 (2 L of blowing agent for 1000 L of water). As shown in FIG. 8 (B), in the case of a gravel layer, for example, in the case of drilling 15m, it takes 5 hours according to the drilling water, but 4 hours according to the foaming agent solution having a concentration of 1/1000. With 1000 blowing agent solution, drilling can be performed in 3 hours. Further, for example, in the case of drilling 30 m, it takes 12 hours with the drilling water, 9 hours with the 1/1000 foaming agent solution, and 7 hours with the 2/1000 foaming agent solution. A hole can be made. As described above, the drilling time is shortened when foaming water using a foaming agent solution having a high concentration is used.

  As described above, according to the present embodiment, the drilling time can be shortened without changing the amount of water consumed per minute by changing the concentration of the foaming agent solution depending on the ground conditions. Therefore, the amount of water used can be reduced, and water and equipment costs can be reduced. And the dilution of fluidization processing soil can be prevented and the strength fall of the restored ground can be prevented. Further, the concentration of the foaming agent solution can be adjusted by adding (or not) 1 L of the foaming agent to 1000 L of water, and it is easy to manage without much labor.

[Foaming water generator]
FIG. 9 shows an embodiment of the foaming device 126 in the foaming water generating device 12. The configuration in the case where the output of the compressor 128 is 1.00 m ³ per minute and the output of the water sprayer 124 is 5 L per minute is shown by a schematic cross-sectional view.

  The foaming device 126 is composed of a metal tube having a total length of 500 to 1500 mm, a diameter of 200 to 500 mm, and a thickness of 6 mm, and is configured to accommodate a foaming agent solution. However, the material and shape are not limited to this as long as they have the same size. And the size of the foaming apparatus 126 should just be a size for producing | generating foaming water of 5L / min, and the facilities (For example, length 4000mm, width | variety) for supplying drilling water and a bentonite suspension in a conventional construction method. Compared with a mixing plant having a height of 2000 mm and a height of 2300 mm, it can be realized at a small scale and at a low cost.

  The foaming device 126 has, on one end side, a port 126a that is connected to the compressor 128 and takes in compressed air, and a port 126b that is connected to the sprinkler 124 and takes in the blowing agent solution. The foaming device 126 has a port 126c connected to the water conduit 14 on the other end side. And in the foaming apparatus 126, the pipe body 127 which connects the port 126a and the port 126c is provided. The tube body 127 has a foaming agent solution intake 127a at a position near the port 126c, for example, within 300 mm from the port 126c.

  The foaming device 126 contains a foaming agent solution fed from the port 126b. Here, the foaming device 126 has a function of reserving a predetermined amount of the foaming agent solution to be mixed with the compressed air. The compressed air from the compressor 128 is pumped into the tube 127. And the pipe body 127 takes in a foaming agent solution from the intake 127a, and mixes this with compressed air. Then, the foaming agent solution generates bubbles in the tube 127 and foams, and foaming water is generated. Then, the foamed water is pressure-fed by the compressed air from the pipe body 127 through the port 126c to the water guide pipe 14, and is sent to the injection hole 2a through the water guide pipe 14.

  In such a configuration, the water guide pipe 14 and the pipe body 127a have substantially the same diameter, for example, 50 mm to 100 mm. Moreover, the diameter of the intake 127a which takes in a foaming agent solution is about 50 mm, for example. As described above, since the foaming agent solution is generated in the tube body 127 having the same diameter as that of the water guide pipe 14 that is a transport path of the foaming water to generate the foaming water, a fine size (preferably a diameter of 500 μm or less) is required. Foamed water is pumped through the conduit 14 with bubbles. Therefore, for example, compared with the case where foaming water is generated in advance by mixing the foaming agent and compressed air in the foaming device 126 and the foamed water is fed into the water conduit 14, the size of the bubbles can be reduced. Therefore, foam-like foaming water can be obtained. The foaming water produced by such a configuration expands to about 6 times the volume of the foaming agent solution. Therefore, the drilling water in the conventional construction method can muddy the ground around the buried pile with a small amount of water, as compared to making the ground around the buried pile 30 into a foam mud. As a result, it is possible to prevent dilution of the fluidized soil introduced in the subsequent steps.

[Restored ground]
FIG. 10 shows the results of a standard penetration test performed on the restored ground in each of the conventional method and the present embodiment. Here, the composition of the fluidized soil placed in the buried hole is 480 kg of water, 982.8 kg of earth and sand (wet density 1.89), and 100 kg of cement.

  FIG. 10 shows the underground depth at which the penetration test was performed and the N value at each depth for each of the conventional method and the present embodiment. According to the conventional method, the N value “0” indicating a non-solidified pasty ground was obtained at depths of 7.00 m, 8.00 m, 11.00 m, 16.00 m, and 18.00 m, and monken self-settlement was observed. Further, the N value was “0” at the depths of 17.00 m, 24.00 m, 26.00 to 28.00 m, and 35.10 to 38.20 m, and rod self-sedimentation was observed. On the other hand, according to the present embodiment, N values of “5” to “30” were obtained at almost all depths except that monken self-sedimentation was observed at 24.00 m.

  Here, when newly providing a buried object in the restored ground, as described above, it is necessary that the buried hole that is backfilled does not collapse. On the other hand, for example, if the cement content in the fluidized soil is increased and the degree of solidification is increased too much, drilling becomes difficult. Therefore, it is desirable that the strength is sufficient to enable drilling. In this respect, the N value of “5” to “30” in the standard penetration test indicates the strength at which the hole wall of the newly drilled buried hole does not collapse and can be drilled again. As described above, according to the present embodiment, it is possible to restore a ground having an appropriate strength that is not too soft and is not too hard. Therefore, a new buried object can be efficiently provided on the ground restored after the buried pile is pulled out.

2: drilling casing, 2a: injection hole, 12: foaming water generator, 20: drilling device

Claims (3)

A method for extracting buried piles,
Foaming a foaming agent solution containing at least one of a surfactant system, a protein system and a resin soap system to generate foaming water;
A step of injecting the foamed water from the drilling casing onto the ground when drilling the ground around the buried pile with a drilling casing;
A process of pulling out the buried pile by holding means;
A step of pouring fluidized soil containing a cement-based solidifying agent into the buried hole when the buried pile is pulled out from the buried hole;
Refilling the buried hole with earth and sand, restoring the ground for drilling a new buried hole overlapping the buried hole, and
I have a,
The foaming water is
A foamed water generating device that generates foamed water that is supplied to the drilled casing and sprayed to the ground by the drilled casing,
An accommodating portion for accommodating a foaming agent solution;
And a pipe body connected to the water conduit connected to the drilled casing and having substantially the same cross-sectional area as the water conduit, to which compressed air is pumped,
The tube body has an intake port for taking in the solution of the foaming agent from the housing portion, and the foaming agent solution taken in from the intake port and the compressed air are mixed therein to generate bubbles, A method for pulling a buried pile, wherein the foamed water is generated by a foaming water generating device that generates the foamed water and pumps the generated foamed water to the water conduit . In claim 1,
In the step of generating the foamed water, the embedded pile is drawn out by introducing the foaming agent solution into a pipe body to which compressed air is pumped and mixing the compressed air and the foaming agent solution to generate the foamed water. Method. A foaming water generating device that generates foaming water that is supplied to a drilling casing that drills the ground around the buried pile and is injected into the ground by the drilling casing,
An accommodating portion for accommodating a foaming agent solution;
And a pipe body connected to the water conduit connected to the drilled casing and having substantially the same cross-sectional area as the water conduit, to which compressed air is pumped,
The tube body has an intake port for taking in the solution of the foaming agent from the housing portion, and the foaming agent solution taken in from the intake port and the compressed air are mixed therein to generate bubbles, A foaming water generating apparatus characterized by generating the foaming water and pumping the generated foaming water to the water conduit.

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