JP5350116B2 - Method and apparatus for creating ground improvement pile - Google Patents

Description

  The present invention relates to a method of creating a ground improvement pile using sand and crushed stone or recycled material (recycled crushed stone, converter slag), etc. in the ground using a casing pipe and a ground improvement pile creation device, For sandy ground, which is mainly loosely saturated, as countermeasures for the purpose of preventing liquefaction, increasing shear resistance, increasing horizontal resistance, preventing compression settlement, etc. It is used as a countermeasure method for the purpose of increasing bearing capacity, increasing shear resistance, and preventing slip failure.

  As a countermeasure method for loosely saturated sandy ground, a method of increasing the density of the ground by creating a plurality of well-compacted sand piles at appropriate intervals in the ground is known.

  In addition, as a conventional countermeasure method for soft and viscous ground, multiple sand compaction piles (sand piles) are created in the ground at appropriate intervals to increase bearing capacity and reduce settlement, etc., and increase the strength of the ground. There are known methods for achieving this.

  In any method, a casing pipe with an outer diameter of about 300 to 500 mm into which a certain amount of filling material such as sand or crushed stone is put is rotated in the ground (static or auger method) or vibrated (dynamic or vibratory). System), the casing pipe is pulled out for a predetermined length, the filling material in the casing pipe is discharged into the ground, and the discharged filling material and surrounding ground are driven back (re-penetration method). This is a method of creating a ground improvement pile that has been expanded to a diameter of about 700 mm by compacting with a low vibration / low noise type and a vibration / noise type method for repeated withdrawal and retraction of the casing pipe. Any of them can create ground improvement piles.

  In addition to the above, other methods for creating ground improvement piles include a method of expanding the diameter with a double pipe inner pipe, a screw or rod (projection rod) installed inside the casing pipe, and discharging the filling material to expand the diameter. There are ways to do it.

JP-A-10-280382 Japanese Patent Laid-Open No. 10-18280 JP 09-125366 A JP 11-323909 A Japanese Patent Laid-Open No. 2002-275484

  However, since the above-mentioned method for creating a ground improvement pile is required to compact the filling material discharged into the ground by back-up with a casing pipe (re-penetration method) and further expand the diameter to a large diameter of about 700 mm. There was a big problem that it took time to create per pile.

  In addition, for example, in order to prevent sandy ground from becoming liquefied due to extremely large earthquake motion, there is a case where further increase in the density of the ground is required. Even if the (N value) is high, in order to satisfy the design specifications, it is necessary to further compact by reworking and increase the density of the ground.

  Even if such ground is to be improved by a conventional construction method, it has been difficult to reliably expand the diameter of the discharged sand with a casing pipe.

  Furthermore, even when trying to penetrate a large-diameter casing pipe into the ground in order to create a ground improvement pile with a large diameter of about 700 mm, the resistance of the peripheral friction of the casing pipe increases, so large heavy machinery and high torque drive There was a big problem that an apparatus was required and cost increased significantly.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a method and an apparatus for creating a ground improvement pile that can efficiently create a ground improvement pile having a large diameter in a short time.

  The ground improvement pile according to claim 1 includes a ground improvement pile made of medium filling material in the ground by inserting the casing pipe into the ground and discharging the filling material from the tip of the casing pipe while pulling up the casing pipe. In the construction method, in the diametrical direction, at the end of the casing pipe formed to be approximately the same diameter as the finished diameter equivalent of the ground improved pile to be created, with an interval equivalent to the finished diameter equivalent of the ground improved pile to be created. A large-diameter casing pipe that has at least one pair of leading portions that are vertically opposed to each other and a mountain-shaped portion that has a convex shape with its lower end projecting upward when viewed from the side, and drills the ground. And inserting the filling material into the pipe while penetrating the casing pipe into the ground, and discharging the filling material in the pipe into the ground while pulling out the casing pipe. And it is characterized in Rukoto.

  The construction cycle consists of a step of inserting the filling material into the pipe while penetrating the casing pipe into the ground, and a step of discharging the filling material in the pipe into the ground while pulling out the casing pipe. It is characterized by.

  The present invention uses a casing pipe to return a pile (re-penetration method) when creating a pile containing sand, crushed stone, or recycled material (recycled crushed stone, converter slag), etc., in the ground. ), It is possible to create a ground improvement pile having a large diameter of about 700 mm very efficiently.

  According to the present invention, by inserting a large-diameter casing pipe into the ground, stress in the surrounding ground is generated laterally to forcibly increase the density, and then the inside of the ground is filled from the tip of the casing pipe. By simply pulling up the casing pipe while discharging the material, it is possible to create a large-diameter ground improved pile without performing back-up (re-penetration method) with the casing pipe.

  As a method of penetrating the casing pipe into the ground, either a method of static penetration while rotating the casing pipe into the ground or a method of dynamically penetrating while vibrating the casing pipe into the ground is used. Since the leading part for drilling the ground is projected at the tip of the casing pipe, a large-diameter casing pipe can be inserted into the ground efficiently and in a short time by either method. can do.

  The ground improvement pile creation method according to claim 2 is the ground improvement pile creation method according to claim 1, wherein the casing pipe includes an upper casing pipe formed to have a smaller diameter than the finished diameter of the ground improvement pile to be created. It is characterized by comprising a lower casing pipe having a large diameter substantially the same diameter as the finished diameter equivalent of the ground improvement pile to be created.

  ADVANTAGE OF THE INVENTION According to this invention, the resistance of the surrounding surface friction of a casing pipe can be reduced, and a large-diameter casing pipe can be penetrated in the ground in a short time.

  If the upper casing pipe is a casing pipe having a smaller diameter than the lower casing pipe, circumferential friction can be reduced. However, a casing pipe having a diameter of about 300 to 500 mm, which has been widely used as a casing pipe for pile construction, has been used. This makes it easy to obtain pipes and is economical.

  The ground improvement pile creation method according to claim 3 is the ground improvement pile creation method according to claim 2, wherein the diameter is gradually reduced from the lower casing pipe side to the upper casing pipe side between the upper casing pipe and the lower casing pipe. The taper part formed so that it may become is provided.

  According to the present invention, by providing a taper portion between the lower casing pipe and the upper casing pipe to eliminate a large step, the pulling resistance force of the casing pipe can be reduced and the casing pipe can be pulled out smoothly. .

In addition, by loosening the ground directly under the casing pipe with the leading part and the mountain-shaped part attached to the lower end of the casing pipe to reduce the penetration resistance of the casing pipe, the large-diameter casing pipe can be put into the ground in a short time. Can penetrate.

  In particular, when the casing pipe is statically penetrated while rotating into the ground, the leading part and the mountain-shaped part rotate together with the casing pipe, and penetrate into the ground immediately before the penetration of the casing pipe. You can loosen the ground.

  In this case, the leading portion may be provided below the casing pipe so as to be opposed to the diameter direction of the casing pipe with an interval corresponding to the finished diameter of the ground improvement pile to be created.

  Further, the chevron portion can be formed from, for example, two drilling portions. Two holes are vertically symmetrically hanged downward from the center of the bottom of the casing pipe, and the tip of each is joined to the inner side of the opposite leading part, so that the lower end is convex upward when viewed from the side. It can be formed in an equilateral mountain shape.

  Then, the chevron portion formed by the two drilling portions penetrates into the ground while rotating together with the leading portion, thereby drilling the ground directly under the casing pipe cut into the annular groove shape by the leading portion. Can be loosened.

  In this case, in particular, the lower end portion of the mountain-shaped portion is formed in a mountain shape having a convex shape upward, and the leading portion is protruded to face the diameter direction of the casing pipe, so that the drilling soil is mountain-shaped. It flows out to the outside of the part and the leading part, and can be prevented from being discharged to the ground surface.

  When the diameter of the casing pipe is particularly large, a plurality of sets of the leading portion and the mountain-shaped portion may be attached in two directions orthogonal to the casing pipe, for example.

The ground improvement pile creation method according to claim 4 is characterized in that in the ground improvement pile creation method according to any one of claims 1 to 3 , a cutting projection is provided on a side portion of the preceding portion. Therefore, even if the casing pipe has a large diameter, it is possible to prevent the penetration resistance from increasing. The protrusion length of the cutting projection in this case may be about ¼ of the diameter of the large-diameter casing pipe. Furthermore, the penetration of the casing pipe can be accelerated by providing a bit at the lower end of the chevron.

The ground improvement pile building apparatus according to claim 5 is the method of generating stress in the surrounding ground sideways by forcibly increasing the density by penetrating the casing pipe into the ground, and then from the tip of the casing pipe. In the ground improvement pile construction device that raises the casing pipe while discharging the filling material into the ground and creates a ground improvement pile made of filling material in the ground, it is almost equivalent to the finished diameter equivalent of the ground improvement pile to be created A large-diameter casing pipe, and at least one pair of preceding portions that are suspended in the diametrical direction at an interval substantially equivalent to the finished diameter of the pile formed at the tip of the casing pipe. It is characterized by comprising.

  According to the present invention, by inserting a large-diameter casing pipe into the ground, the stress of the surrounding ground is generated laterally to forcibly increase the density, and then the inside of the casing pipe enters the ground from the tip. By simply pulling up the casing pipe while discharging the filling material, the ground improvement pile with a large diameter of about 700 mm made of sand, crushed stone, or recycled material (recycled crushed stone, converter slag), etc. will not be driven back by the casing pipe. It is possible to create a reliable ground improvement pile very efficiently.

  In particular, by placing a large-diameter casing pipe corresponding to the finished diameter of the ground improvement pile to be created at the bottom and a casing pipe with a smaller diameter at the top, respectively, the friction resistance with the surrounding ground that occurs when the casing pipe penetrates is reduced. Can be reduced. Moreover, the frictional resistance with the surrounding ground which generate | occur | produces at the time of extraction of a casing pipe can also be reduced.

  In addition, by loosening the ground directly under the casing pipe by the leading part and the mountain-shaped part attached to the lower end of the lower casing pipe, the penetration resistance of the casing pipe is reduced, so that the large-diameter casing pipe can be put into the ground for a short time. Can penetrate.

One embodiment of the pile creation apparatus of the present invention is shown, (a) is the side view, and (b) is a top view showing the bottom. It is a side view which shows the pile production apparatus of FIG. 1 installed in the construction machine. The penetration speed characteristics of the casing pipe when it penetrates into the ground while rotating the casing pipe of the pile forming apparatus shown in FIG. 1, and the casing when it penetrates into the ground while rotating the casing pipe of the conventional pile forming apparatus It is the graph which compared the penetration speed characteristic of the pipe. The rotational torque characteristics of the casing pipe when it penetrates into the ground while rotating the casing pipe of the pile forming device shown in FIG. 1, and the rotation when it penetrates into the ground while rotating the casing pipe of the conventional pile forming device 6 is a graph comparing torque characteristics. It is a side view which shows the pile creation apparatus of other embodiment installed in the construction machine. The pile creation apparatus of other embodiment installed in the construction machine is shown, (a) is a side view thereof, (b) is an enlarged side view showing a leading portion attached to the lower end portion of the casing pipe, and (c) is a side view. It is the enlarged bottom view.

  1 and 2 show an embodiment of a ground improvement pile forming apparatus according to the present invention. In the figure, the pile forming apparatus is a lower casing projecting from the upper casing pipe 1 and the tip of the upper casing pipe 1. The pipe 2 and the lower casing pipe 2 are provided with a pair of leading portions 3 and 3, a chevron portion 4, and cutting projections 5 and 5 attached to the tip portions of the lower casing pipe 2.

  The upper casing pipe 1 is formed to have a smaller diameter than the finished diameter of the pile to be formed, and generally has an outer diameter of about 300 to 500 mm.

  The lower casing pipe 2 is formed to have an outer diameter larger than the outer diameter of the upper casing pipe 1 and substantially equal to the finished diameter of the ground improvement pile to be formed, and generally has a large diameter of about 700 mm.

  The lower casing pipe 2 projects from the tip of the upper casing pipe 1 so as to be continuous on the same axis as the upper casing pipe 1, and the lower casing pipe 2 is interposed between the upper casing pipe 1 and the lower casing pipe 2. A tapered portion 6 is formed so that the diameter gradually decreases from the second side to the upper casing pipe 1 side.

  In addition, the earth pressure resistance which generate | occur | produces at the time of extraction can be reduced by changing the ratio of the length of the upper casing pipe 1 and the lower casing 2 with soil quality.

  Furthermore, a bottom cover 10 (not shown) is attached to the lower end of the lower casing pipe 2, and the bottom cover is the weight of the filling material such as sand and crushed stone introduced into the upper casing pipe 1 and the lower casing pipe 2. However, the bottom cover 10 may not be attached depending on the soil quality of the target ground.

  In addition, the upper casing pipe 1 in this case is formed from a casing pipe or the like conventionally used as a pile forming casing pipe.

  The leading portions 3 and 3 are attached to the outer portion of the lower casing pipe 2 and face the diametrical direction of the lower casing pipe 2 at an interval substantially equal to the finished diameter equivalent of the ground improvement pile to be created. A predetermined length is vertically suspended below the casing pipe 2.

  The chevron 4 is formed of two drilling portions 4a and 4a that extend symmetrically downward from the center of the bottom of the lower casing pipe 2 toward the leading portions 3 and 3, and the lower end is the top when viewed from the side. It is formed in an equilateral mountain shape having a convex shape. The distal end sides of the hole-cutting portions 4 a and 4 a are joined to the inner portions of the preceding portions 3 and 3, and the proximal end side is joined to the bottom portion of the lower casing pipe 2.

  The cutting projections 5 and 5 are suspended from the side surface of the casing pipe in the diametrical direction, and can prevent the penetration resistance from increasing even if the casing pipe has a large diameter. The cutting projections 5 and 5 are usually attached to the installation positions of the leading parts 3 and 3, respectively. However, they may be attached to a position 90 degrees in phase with the cutting protrusions 5 and 5 (to disperse the load acting on the casing pipe). , May be attached to both.

  Moreover, the protrusion length of the cutting protrusions 5 and 5 should just be about 1/4 of the diameter of a large diameter casing pipe. Depending on the soil quality of the target ground, penetration can be promoted by changing its size and shape.

  In such a configuration, when the upper casing pipe 1 and the lower casing pipe 2 are lowered while rotating, the raw ground is cut into an annular groove shape to the finished equivalent diameter of the pile formed while the leading portions 3 and 3 are simultaneously rotating. While penetrating into the ground.

  After that, the drilling portions 4a and 4a of the mountain-shaped portion 4 together with the leading portions 3 and 3 rotate, and the ground immediately below the inner lower casing pipe 2 cut into an annular groove is drilled and loosened into the ground. Intrude.

  Furthermore, after that, the lower casing pipe 2 and the upper casing pipe 1 penetrate into the ground loosened by the leading portion 3 and the mountain-shaped portion 4 while rotating.

  Moreover, the upper casing pipe 1 penetrates without receiving excessive resistance of the peripheral surface friction because it is formed to have a diameter smaller than the equivalent diameter of the finished ground improvement pile.

  Therefore, when the lower casing pipe 2 and the upper casing pipe 1 penetrate into the ground without discharging the drilled soil to the ground surface, the surrounding ground is compacted and the stress is generated laterally. The density of the original ground can be forcibly increased.

  Further, the lower casing pipe 2 and the upper casing pipe 1 can penetrate into the ground in a shorter time than a conventional casing pipe and with a small rotational torque.

  3 shows a penetration speed characteristic of the casing pipe when the casing pipe shown in FIG. 2 is inserted while rotating into the ground, and a penetration speed of the casing pipe when the conventional casing pipe is inserted while rotating into the ground. It is a comparison of characteristics.

  Graphs (a) and (b) show the penetration speed characteristics of the casing pipe of the present invention, and (c) and (d) show the penetration speed characteristics of the conventional casing pipe.

  In graphs (a) and (b), the outer diameter and the rotational speed of the lower casing pipe are the same with 700 mm and 8 rpm, respectively, and the loads are different from 40 t and 50 t, respectively.

  Graphs (c) and (d) have the same casing pipe load and rotational speed of 40 t and 8 rpm, respectively. The outer diameter of the casing pipe is different from 400 mm and 700 mm, respectively. It is the same form as (a) and (b).

  FIG. 4 shows the rotational torque characteristic of the casing pipe when the casing pipe shown in FIG. 2 is inserted while rotating into the ground, and the rotational torque of the casing pipe when the conventional casing pipe is inserted while rotating into the ground. It is a comparison of characteristics.

  Graphs (e) and (f) show the rotational torque characteristics of the casing pipe of the present invention, (g) shows a conventional casing pipe, and the tip portion shows the rotational torque characteristics of the same form as (e) and (f). .

  In graphs (e) and (f), the outer diameter and the rotational speed of the lower casing pipe are the same with 700 mm and 8 rpm, respectively, and the loads are different from 40 t and 50 t, respectively. Graph (g) is the same as graph (e) in that the outer diameter of the casing pipe, the load, and the rotation speed of the casing pipe are 700 mm, 40 t, and 8 rpm, respectively.

  As is apparent from the two graphs, it is faster to penetrate the ground at the tip of the casing pipe, for example, as shown in FIG. 1, than the conventional casing pipe. It is more conventional to use a casing pipe consisting of an upper casing pipe formed with a smaller diameter than the finished diameter and a lower casing pipe formed with a large diameter substantially the same diameter as the finished diameter of the ground improvement pile to be created. It turns out that rotational torque can be made smaller than a thing.

  Next, the construction method of the ground improvement pile of this invention is demonstrated.

(1) First, the construction machine 7 equipped with the pile construction device of the present invention is installed on the soft ground to be constructed, and the upper casing pipe 1 and the lower casing pipe 2 are vertically aligned with the pile core at the pile construction position. Build in. In this case, as the construction machine 7, a construction machine that is generally used in the formation of a conventional compacted pile can be used.

(2) Next, the upper casing pipe 1 and the lower casing pipe 2 are statically penetrated to the improved depth while rotating into the ground. In addition, filling material such as sand, crushed stone, or recycled material is put into the upper casing pipe 1 and the lower casing pipe 2. Note that a solidifying material or an expanding material may be added to the filling material as necessary.

  When the upper casing pipe 1 and the lower casing pipe 2 are inserted while rotating into the ground, the original ground is formed into an annular groove corresponding to the finished diameter of the ground improvement pile first formed by rotating the leading portions 3 and 3 at the tip. Penetration into the ground while cutting into a shape.

  Subsequently, the chevron 4 is rotated thereafter, and the ground immediately below the lower casing pipe 2 cut into an annular groove is drilled and loosened to penetrate into the ground, and then the lower casing pipe 2 is loosened. Penetration while rotating into the ground.

  Therefore, the lower casing pipe 2 can penetrate into the ground without receiving excessive penetration resistance. Moreover, the upper casing pipe 1 can be penetrated into the ground without receiving a large peripheral frictional resistance by being formed with a diameter smaller than the finished diameter of the ground improvement pile to be created.

  From the above, the lower casing pipe 2 forcibly penetrates into the ground, the surrounding ground is compacted, and the stress is generated laterally, thereby forcibly increasing the density of the original ground. Can increase the ground strength.

(3) Next, the upper casing pipe 1 and the lower casing pipe 2 are gradually pulled out while rotating in reverse, and the filling material in the casing pipe is discharged from the lower end of the lower casing pipe 2 into the ground.

  In this case, the bottom cover 10 (not shown) attached to the lower end of the lower casing pipe 2 is automatically opened by the weight of the filling material, so that the filling material in the lower casing pipe 2 pulls out the casing pipe. At the same time, it is discharged from the lower end of the lower casing pipe 2 into the ground. Therefore, after the casing pipe is pulled out, a ground improvement pile made of a filling material such as sand or crushed stone is created. The bottom cover 10 may not be attached depending on the soil quality of the target ground.

  Further, since the taper portion 6 is provided between the upper casing pipe 1 and the lower casing pipe 2, resistance to circumferential friction generated when the casing pipe is pulled out is extremely small, and the casing pipe can be pulled out relatively smoothly. it can.

  FIG. 5 shows another embodiment of the present invention. In particular, only the entire length of the casing pipe 8 is formed to have a large diameter, and the leading portion 3, the chevron portion 4 and other configurations will be described with reference to FIGS. This is almost the same as the embodiment described above.

  According to this embodiment, when penetrating the casing pipe 8 into the ground, the casing pipe 8 can be vertically penetrated into the ground by guiding the entire length of the casing pipe 8 by the surrounding ground. High quality ground improvement piles can be created. In addition, since a large amount of filling material can be put into the casing pipe 8 in a single filling material charging step, work efficiency can be improved.

  6 (a) and 6 (b) show another embodiment of the present invention, and the casing pipe 8 has a large diameter over the entire length thereof. Further, the leading portion 9 is formed in an inverted triangle shape when viewed from the side, and a plurality of the leading portions 9 are circumferentially arranged on the casing pipe 8 by pinning the bottom portion to the peripheral portion of the lower end portion of the casing pipe 8 in a rotatable manner. It is installed vertically.

  Also, each leading portion 9 is set in a conical shape with a gradually decreasing diameter in the lower end direction by drawing the lower end portion onto the central axis of the casing pipe 8 and closely contacting each other, thereby closing the lower end portion of the casing pipe 8. Has been. Each leading portion 9 drawn on the central axis of the casing pipe 8 is opened downward by the weight of the filling material such as sand and crushed stone introduced into the casing pipe 8.

  According to this embodiment, since the tip of the leading portion 9 is formed in a sharp pointed shape, the casing pipe 8 can be dynamically penetrated while giving vibration (dynamic / vibro method) into the ground. It is possible to penetrate the casing pipe 8 very efficiently.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to efficiently create a reliable ground improvement pile without returning the large-diameter ground improvement pile with a casing pipe.

DESCRIPTION OF SYMBOLS 1 Upper casing pipe 2 Lower casing pipe 3 Leading part 4 Mountain-shaped part 5 Cutting protrusion 6 Tapered part 7 Construction machine 8 Casing pipe 9 Leading part 10 Bottom cover

Claims (5)

  Finishing the ground improvement pile that is created in the method of creating a ground improvement pile made of filling material in the ground by pulling up the casing pipe while penetrating the casing pipe into the ground and discharging the filling material from the tip of the casing pipe At least one pair of leading parts that are suspended in the diametrical direction at the same distance as the finished diameter of the ground improvement pile to be created at the tip of the casing pipe that is formed to have the same diameter as the diameter. And using a large-diameter casing pipe that has a mountain-shaped part that has a convex shape with its lower end protruding upward when viewed from the side between the preceding parts, and while penetrating the casing pipe into the ground A method for creating a ground improvement pile characterized by comprising a step of introducing a filling material into the pipe and a step of discharging the filling material in the pipe into the ground while pulling out the casing pipe. .   2. The method for producing a ground improvement pile according to claim 1, wherein the casing pipe is substantially the same diameter as the upper casing pipe formed with a diameter smaller than the finished diameter equivalent of the ground improved pile to be created, and the finished diameter equivalent of the pile to be created. A method for constructing a ground improvement pile characterized by comprising a lower casing pipe having a large diameter.   3. The method for producing a ground improvement pile according to claim 2, wherein a taper having a gradually decreasing diameter is provided between the upper casing pipe and the lower casing pipe from the lower casing pipe side to the upper casing pipe side. How to create ground improvement piles. The method for creating a ground improvement pile according to any one of claims 1 to 3 , wherein a cutting projection is provided on a side portion of the preceding portion.   It is created in the ground improvement pile construction device that penetrates the casing pipe into the ground and discharges the filling material from the tip of the casing pipe and pulls up the casing pipe to create the ground improvement pile made of filling material in the ground. A casing pipe formed with a large diameter that is approximately the same diameter as the finished diameter of the ground improvement pile, and facing the diameter direction at an interval substantially equivalent to the finished diameter equivalent of the pile formed at the tip of the casing pipe A ground improvement pile building apparatus, comprising: at least one set of leading portions that are suspended.

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