JP6807285B2 - Construction method of ground improvement body and casing pipe - Google Patents

Description

The present invention relates to a method for creating a ground improvement body by a high-pressure injection stirring method and a casing pipe used therefor.

Conventionally, when drilling a hole in the ground, it is necessary to stabilize the hole wall and prevent deformation of the surrounding ground in the ground including a soil layer in which the hole wall may collapse. As a typical hole wall stabilization measure, there is a method of using a casing. For example, the all-casing method is a method of preventing the collapse of the hole wall over the entire length of the hole. In the all-casing method, a cylindrical casing tube is press-fitted into the ground by a casing press-fitting device, and the inside of the casing is excavated by a hammer grab.

Further, in the TBH method, a drill pipe having a drilling bit at the tip is rotated to drill a hole while adding a drill pipe. Then, the pores are filled with a stabilizing liquid having a density higher than that of water to stabilize the pore walls.
In the deep foundation method, the ground inside is excavated manually or mechanically while retaining the hole wall with a liner plate or the like.

Further, a method of preventing the hole wall from collapsing by using a ground improvement body without using a casing has also been proposed. FIG. 13 is a diagram showing a method of preventing the hole wall from collapsing by using the ground improvement body 103. In the method shown in FIG. 13, as shown in FIG. 13A, a solid ground improvement body 103 is formed on the ground 101. Then, as shown in FIG. 13B, the inside of the solid ground improvement body 103 is excavated to form the drilled portion 105. Then, as shown in FIG. 13C, a pile 107 is constructed in the drilled portion 105 (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-217119

However, when constructing piles in the hole while stabilizing the hole wall by using a casing in the ground including a soil layer where the hole wall of the excavation hole may collapse, the number of piles is adjusted to the number of piles to be constructed. A casing is required. In addition, construction is complicated because work processes such as casing installation, excavation inside the casing, and removal of the casing are required.

Since the TBH method relies on a stabilizer to maintain the hole wall, it is important to manage the stabilizer, and it cannot be said that there is no risk of hole wall collapse. In addition, if there are underground obstacles such as existing piles in the ground, it is necessary to remove them in advance.
The deep foundation method is difficult to construct in places where the groundwater level is high or where toxic gas is generated from the ground. Moreover, in a narrow space, it is necessary to perform excavation work manually, which is dangerous.

In the method of stabilizing the hole wall by using the solid ground improvement body, it is necessary to drill the inside of the ground improvement body after forming the ground improvement body. In addition, since the earth and sand generated by the drilling of the ground improvement body generally contains cement, the pH is high and it is classified as construction sludge, so that the cost required for disposal increases.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a ground improvement body capable of safe and efficient construction and surely stabilizing the hole wall. It is to provide a construction method and a casing pipe.

In order to achieve the above-mentioned object, the first invention is a method for creating a ground improvement body by a high-pressure injection stirring method, which is a steel casing pipe having a double-pipe structure having an outer casing and an inner casing in the ground. In the step a of rotary press-fitting or rotary drilling press-fitting to a predetermined depth, high-pressure cement milk and compressed air are injected from a nozzle provided near the tip of the steel casing pipe, and the steel casing pipe is rotated. This is a method for creating a ground improvement body, which comprises a step b of pulling up from the ground while making the ground improve.

In the first invention, a steel casing pipe having a double pipe structure having an outer casing and an inner casing is press-fitted into the ground, and then high-pressure cement milk and compressed air are injected from a nozzle provided near the tip of the pipe. Pull up from the ground. As a result, a tubular ground improvement body capable of reliably stabilizing the hole wall can be safely and efficiently constructed without generating excavated soil containing cement.

In the step b, for example, the high-pressure cement milk and compressed air are injected in the circumferential direction of the steel casing pipe.
As a result, a tubular ground improvement body can be formed in the excavation range formed by press-fitting the steel casing pipe.

In the step b, the high-pressure cement milk and compressed air may be injected vertically downward.
As a result, a tubular ground improvement body can be formed in the excavation range formed by press-fitting the steel casing pipe.

In the step b, the high-pressure cement milk and compressed air may be injected in the radial direction of the steel casing pipe so that the two jets intersect.
By injecting high-pressure cement milk and compressed air in the radial direction of the steel casing pipe so that the two jets intersect, the drilling range formed by press-fitting the steel casing pipe is widened and widened. A tubular ground improvement body can be formed in the area.

In the step b, the high-pressure cement milk and compressed air may be injected in a direction forming a predetermined angle with the circumferential direction of the steel casing pipe in a plan view.
By injecting high-pressure cement milk and compressed air in a direction forming a predetermined angle with the circumferential direction, the excavation range formed by press-fitting the steel casing pipe is widened, and the widened excavation range is expanded into a tubular ground. An improved body can be formed.

It is desirable that the tip of the outer casing is located below the tip of the inner casing.
If a steel casing pipe is used in which the tip of the outer casing is located below the tip of the inner casing and a nozzle is placed between the tip of the outer casing and the tip of the inner casing, high-pressure cement milk and compressed air can be injected. The range can be limited to the inside of the outer casing.

In the step a, high-pressure water may be sprayed in the circumferential direction and / or downward of the steel casing pipe near the tip of the steel casing pipe.
As a result, the ground is excavated with high-pressure water, and the steel casing pipe can be easily press-fitted.

The second invention is a casing pipe used for constructing a ground improvement body by a high-pressure injection stirring method, wherein a double pipe having an outer casing and an inner casing and the vicinity of the tip of the outer casing are viewed in a plan view. The casing pipe includes a nozzle arranged so as not to protrude from the heavy pipe, and high-pressure cement milk and compressed air are injected from the nozzle.

In the second invention, high-pressure cement milk and compressed air are injected from a nozzle arranged so as not to protrude from the double pipe in a plan view near the tip of the outer casing of the double pipe. By using the casing pipe of the second invention, a tubular ground improvement body capable of reliably stabilizing the hole wall can be safely and efficiently constructed without generating excavated soil containing cement. Can be done.

In the second invention, the tip of the outer casing may be longer than the tip of the inner casing, and the nozzle may be arranged between the outer casing and the inner casing in a plan view.
This allows the injection range of high pressure cement milk and compressed air to be limited to the inside of the outer casing.

According to the present invention, it is possible to provide a method for creating a ground improvement body and a casing pipe that can be safely and efficiently constructed and can surely stabilize the hole wall.

The figure which shows each process for constructing a tubular ground improvement body 21 The figure which shows the structure and operation of the casing pipe 3. The figure which shows the example which forms the cylindrical ground improvement body using another casing pipe. The figure which shows the structure and operation of the casing pipe 3d. The figure which shows each process for constructing a tubular ground improvement body 45 The figure which shows the structure and operation of the casing pipe 3e The figure which shows the structure and operation of the casing pipe 3f The figure which shows the structure and operation of the casing pipe 3g The figure which shows the example of the casing pipe used for rotary drilling press-fitting. The figure which shows each process for constructing the ground improvement body 82 using the self-propelled construction machine 80 and the casing pipe 87. The figure which shows the structure and operation of a casing pipe 87 The figure which shows the example which made the ground improvement body 21 as a measure against liquefaction. The figure which shows the method of preventing the collapse of a hole wall by using a ground improvement body 103

Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing each process for constructing the tubular ground improvement body 21. FIG. 1A is a diagram showing a state in which the casing pipe 3 is press-fitted, FIG. 1B is a diagram showing a state in which the casing pipe 3 is press-fitted, and FIG. 1C is a casing pipe 3 FIG. 1D is a diagram showing a state in which the casing pipe 3 is being pulled up.

FIG. 2 is a diagram showing the configuration and operation of the casing pipe 3. FIG. 2A is a cross-sectional perspective view showing the vicinity of the tip 13 of the casing pipe 3. FIG. 2B is a vertical cross-sectional view of the casing pipe 3 at the position of the improved rod 31, and is a view showing a cross section taken along the line EE of FIG. 2A. FIG. 2 (c) is a horizontal cross-sectional view in a state where the casing pipe 3 is press-fitted into the ground 1, and is a view showing a cross section by arrows C1-C1 of FIG. 1 (a). FIG. 2D is a horizontal cross-sectional view in a state where the casing pipe 3 is pulled up from the ground 1, and is a view showing a cross section by arrows C2-C2 in FIG. 1C.

As shown in FIG. 1A, the casing pipe 3 has a double pipe structure having an outer casing 5 and an inner casing 7. The casing pipe 3 has a shape in which the tip 15 of the outer casing 5 is located below the tip 17 of the inner casing 7, and the bottom plate 9 is provided at the position of the tip 17 of the inner casing 7. The casing pipe 3 is made of steel.

Further, as shown in FIGS. 2A and 2B, an improved rod 31 is provided between the outer casing 5 and the inner casing 7. A nozzle 33 is provided at the tip of the improved rod 31. The tip of the improved rod 31 penetrates the bottom plate 9, and the nozzle 33 is arranged near the tip 13 of the casing pipe 3 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7. As shown in FIG. 2C, the nozzles 33 are arranged at two locations between the outer casing 5 and the inner casing 7 in a plan view.

The direction of the arrow A shown in FIGS. 1 and 2 is the rotation direction of the casing pipe 3. The nozzle 33 is provided on the rear side of the improved rod 31 in the rotational direction of the casing pipe 3. From the nozzle 33, a jet 35 composed of high-pressure cement milk and compressed air is injected in the circumferential direction of the casing pipe 3 and rearward in the rotational direction of the casing pipe 3.

In order to form the ground improvement body 21 using the casing pipe 3, first, as shown in FIG. 1A, the casing pipe 3 is rotated in the direction indicated by the arrow A by using the all-turning construction machine 11. It is lowered in the direction indicated by the arrow B and press-fitted into the ground 1. At this time, as shown in FIG. 2C, the jet 35 is not injected from the nozzle 33.

By press-fitting the casing pipe 3, the tubular excavation range 25 shown in FIG. 2C is formed in the ground 1. In addition, in FIG. 2C, the illustration of the extra digging portion is omitted, and the actual excavation range 25 is from a little outside of the outer peripheral surface 27 of the outer casing 5 to a little inside of the inner peripheral surface 29 of the inner casing 7. Formed between. As shown in FIG. 1B, the press-fitting of the tubular casing pipe 3 is completed when the tip 13 of the casing pipe 3 reaches a predetermined depth 19.

Next, as shown in FIG. 1 (c), the casing pipe 3 is rotated in the direction indicated by the arrow A and raised in the direction indicated by the arrow D to be pulled up from the ground 1. At this time, as shown in FIG. 2D, the jet 35 is injected from the nozzle 33 in the circumferential direction of the casing pipe 3 and rearward in the rotation direction of the casing pipe 3.

When the jet 35 is injected while pulling up the casing pipe 3, the high-pressure cement milk and compressed air and the earth and sand of the ground 1 are agitated by the jet 35 inside the tubular excavation range 25 formed when the casing pipe 3 is press-fitted. (High-pressure injection stirring method). Then, as shown in FIGS. 1 (c) and 2 (d), a tubular ground improvement body 21 having a thickness of 23 is formed. The ground inside the ground improvement body 21 remains as unimproved ground 37. As shown in FIG. 1D, the pulling up of the casing pipe 3 is completed when the ground improvement body 21 is formed over the entire length from the ground surface to a predetermined depth 19.

As described above, according to the method for creating the ground improvement body of the first embodiment, the casing pipe 3 having a double pipe structure in which the tip 15 of the outer casing 5 is longer than the tip 17 of the inner casing 7 is used. While pulling up the pipe 3 from the ground 1, high-pressure casing milk and compressed air are injected from the nozzle 33. As a result, the tubular ground improvement body 21 can be safely and efficiently constructed without generating excavated soil containing cement.

Further, by arranging the nozzle 33 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7, the injection range of the jet 35 can be limited to the inside of the outer casing 5. Further, by injecting the jet 35 rearward in the rotation direction of the casing pipe 3, the rotational force of the total turning construction machine 11 can be reduced.

In the first embodiment, the jet 35 is injected backward in the rotation direction of the casing pipe 3, but the jet may be injected forward in the rotation direction of the casing pipe 3. If the jet is injected forward in the direction of rotation of the casing pipe, the frictional force with the ground 1 can be reduced. Further, the number of nozzles 33 installed is not limited to two, and may be one or more.

FIG. 3 is a diagram showing an example of forming a tubular ground improvement body using another casing pipe. Each figure shown in FIG. 3 is in the process of pulling up the casing pipe shown in FIG. 1 (c), and is a view showing a cross section by arrows C2-C2. The direction of the arrow A shown in FIG. 3 is the rotation direction of the casing pipe 3.

FIG. 3A is a diagram showing an example in which the casing pipe 3a is used. The casing pipe 3a has almost the same structure as the casing pipe 3, but the improved rod 31a is provided instead of the improved rod 31. The improved rod 31a has a nozzle 33a on the front side in the rotation direction of the casing pipe 3a. In the example shown in FIG. 3A, when the casing pipe 3a is rotated and pulled up from the ground 1, a jet 35a of high-pressure cement milk and compressed air is ejected from the nozzle 33a in the circumferential direction of the casing pipe 3a. Moreover, the tubular ground improvement body 21a is formed by injecting the casing pipe 3a forward in the rotation direction.

FIG. 3B is a diagram showing an example in which the casing pipe 3b is used. The casing pipe 3b has almost the same structure as the casing pipe 3, but the improved rod 31b is provided instead of the improved rod 31. The improved rod 31b has nozzles 33b at two locations on the front side and the rear side in the rotation direction of the casing pipe 3b. In the example shown in FIG. 3B, when the casing pipe 3b is rotated and pulled up from the ground 1, a jet 35b of high-pressure cement milk and compressed air is ejected from the nozzle 33b in the circumferential direction of the casing pipe 3b. Further, the tubular ground improvement body 21b is formed by injecting the casing pipe 3b forward and backward in the rotation direction.

FIG. 3C is a diagram showing an example in which the casing pipe 3c is used. The casing pipe 3c has almost the same configuration as the casing pipe 3, but the improved rods 31 are provided at three places. In the example shown in FIG. 3C, when the casing pipe 3c is rotated and pulled up from the ground 1, jets 35 are injected from three nozzles 33 to form a tubular ground improvement body 21c. ..

In this way, even if the casing pipe 3 and the jet injection direction and the number of nozzles installed are different, the tubular ground improvement body can be safely and efficiently constructed without generating excavated soil containing cement. Can be done.

Next, the second embodiment will be described. FIG. 4 is a diagram showing the configuration and operation of the casing pipe 3d. FIG. 4A is a cross-sectional perspective view showing the vicinity of the tip 13 of the casing pipe 3d. FIG. 4B is a horizontal cross-sectional view in a state where the casing pipe 3d is press-fitted into the ground 1, and is a view showing a cross section by arrows C1-C1 of FIG. 1A. FIG. 4C is a horizontal cross-sectional view in a state where the casing pipe 3d is pulled up from the ground 1, and is a view showing a cross section by arrows C2-C2 in FIG. 1C.

As shown in FIG. 4A, the casing pipe 3d has a configuration in which an improved rod 39 is added to the casing pipe 3 of the first embodiment. In the casing pipe 3d, an improved rod 31 and an improved rod 39 are provided between the outer casing 5 and the inner casing 7. A nozzle 41 is provided at the tip of the improved rod 39. The tip of the improved rod 39 penetrates the bottom plate 9, and the nozzle 41 is arranged at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7 in the vicinity of the tip 13 of the casing pipe 3d. The nozzles 41 are arranged at two locations between the outer casing 5 and the inner casing 7 in a plan view. From the nozzle 41, a jet 43 composed of high-pressure cement milk and compressed air is ejected vertically downward.

In order to form the ground improvement body 21d using the casing pipe 3d, first, as shown in FIG. 1A, the casing pipe 3d is rotated in the direction indicated by the arrow A by using the all-turning construction machine 11. It is lowered in the direction indicated by the arrow B and press-fitted into the ground 1. At this time, as shown in FIG. 4B, the jet 35 is not injected from the nozzle 33. Further, the jet 43 is not injected from the nozzle 41.

By press-fitting the casing pipe 3d, the tubular excavation range 25 shown in FIG. 4B is formed in the ground 1. As shown in FIG. 1B, the press-fitting of the casing pipe 3d is completed when the tip 13 of the casing pipe 3d reaches a predetermined depth 19.

Next, as shown in FIG. 1C, the casing pipe 3d is rotated in the direction indicated by the arrow A and raised in the direction indicated by the arrow D to be pulled up from the ground 1. At this time, as shown in FIGS. 4A and 4C, the jet 35 is injected from the nozzle 33 in the circumferential direction of the casing pipe 3 and rearward in the rotation direction of the casing pipe 3d. At the same time, the jet 43 is ejected vertically downward from the nozzle 41.

When the jet 35 and the jet 43 are injected while pulling up the casing pipe 3d, the jet 35 and the jet 43 provide high-pressure cement milk and compressed air and the ground inside the tubular excavation range 25 formed when the casing pipe 3d is press-fitted. The earth and sand of 1 are stirred. Then, as shown in FIGS. 1 (c) and 4 (c), a tubular ground improvement body 21d having a thickness of 23 is formed. The ground inside the ground improvement body 21d remains as unimproved ground 37. As shown in FIG. 1D, the pulling up of the casing pipe 3d is completed when the ground improvement body 21d is formed over the entire length from the ground surface to a predetermined depth 19.

As described above, in the second embodiment, the casing pipe 3d having a double pipe structure in which the tip 15 of the outer casing 5 is longer than the tip 17 of the inner casing 7 is used, and the casing pipe 3d is pulled up from the ground 1 while being pulled up. High-pressure casing milk and compressed air are injected from the nozzles 33 and 41. As a result, the tubular ground improvement body 21d can be safely and efficiently constructed without generating excavated soil containing cement.

Further, by arranging the nozzle 33 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7, the injection range of the jet 35 can be limited to the inside of the outer casing 5. Further, by injecting the jet 35 rearward in the rotation direction of the casing pipe 3d, the rotational force of the total turning construction machine 11 can be reduced.

In the second embodiment, the improved rod 31 and the improved rod 39 are used in combination, but a nozzle for injecting a jet in the circumferential direction and a nozzle for injecting a jet downward are provided on one improved rod. It may be provided. Further, the number of nozzles 33 and 41 installed is not limited to two, but may be one or more. Further, instead of the improved rod 31, another improved rod shown in FIG. 3 may be used.

Next, a third embodiment will be described. FIG. 5 is a diagram showing each process for constructing the tubular ground improvement body 45. 5 (a) is a diagram showing a state in which the casing pipe 3e is press-fitted, FIG. 5 (b) is a diagram showing a state in which the casing pipe 3e is press-fitted, and FIG. 5 (c) is a diagram showing a state in which the casing pipe 3e is press-fitted. FIG. 5D is a diagram showing a state in which the casing pipe 3e is being pulled up.

FIG. 6 is a diagram showing the configuration and operation of the casing pipe 3e. FIG. 6A is a cross-sectional perspective view showing the vicinity of the tip 13 of the casing pipe 3e. FIG. 6B is a horizontal cross-sectional view in a state where the casing pipe 3e is press-fitted into the ground 1, and is a view showing a cross section by arrows H1-H1 of FIG. 5A. FIG. 6 (c) is a horizontal cross-sectional view in a state where the casing pipe 3e is pulled up from the ground 1, and is a view showing a cross section by arrows H2-H2 in FIG. 5 (c).

As shown in FIG. 6A, the casing pipe 3e has a configuration in which an improved rod 49 is added to the casing pipe 3 of the first embodiment. As shown in FIG. 6, in the casing pipe 3e, an improved rod 31 and an improved rod 49 are provided between the outer casing 5 and the inner casing 7. A pair of nozzles 51 are provided at the tip of the improved rod 49. The tip of the improved rod 49 penetrates the bottom plate 9, and the pair of nozzles 51 are arranged at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7 in the vicinity of the tip 13 of the casing pipe 3e. .. As shown in FIG. 6B, the nozzles 51 are arranged at two locations between the outer casing 5 and the inner casing 7 so as not to protrude from the double pipe in a plan view.

As shown in FIG. 6A, the pair of nozzles 51 includes an upper nozzle 51a and a lower nozzle 51b. The nozzles 51a and 51b are arranged on the same line in the vertical direction at predetermined intervals. From the upper nozzle 51a, a jet 53a composed of high-pressure cement milk and compressed air is jetted inward in the radial direction of the casing pipe 3e and diagonally downward. From the lower nozzle 51b, a jet 53b composed of high-pressure cement milk and compressed air is jetted inward in the radial direction of the casing pipe 3e and diagonally upward. The jets 53a and 53b are cross jets that intersect inside the inner casing 7.

In order to form the ground improvement body 45 using the casing pipe 3e, first, as shown in FIG. 5A, the casing pipe 3e is rotated in the direction indicated by the arrow F by using the all-turning construction machine 11. It is lowered in the direction indicated by the arrow G and press-fitted into the ground 1. At this time, as shown in FIG. 6B, the jet 35 is not injected from the nozzle 33. Further, the jet 53 is not injected from the nozzle 51.

By press-fitting the casing pipe 3e, the tubular excavation range 25 shown in FIG. 6B is formed in the ground 1. As shown in FIG. 5B, the press-fitting of the casing pipe 3e is completed when the tip 13 of the casing pipe 3e reaches a predetermined depth 19.

Next, as shown in FIG. 5C, the casing pipe 3e is rotated in the direction indicated by the arrow F and raised in the direction indicated by the arrow I to be pulled up from the ground 1. At this time, as shown in FIGS. 6A and 6C, the jet 35 is injected from the nozzle 33 in the circumferential direction of the casing pipe 3e and rearward in the rotation direction of the casing pipe 3e. At the same time, the jet 53 is ejected from the pair of nozzles 51 inward in the radial direction of the casing pipe 3e.

When the jet 35 and the jet 53 are injected while pulling up the casing pipe 3e, the inside of the excavation range 25 formed at the time of press-fitting the casing pipe 3e by the two jets 53, which are cross jets, as shown in FIG. However, the widening portion 55 is formed by cutting to a position where the jet 53a and the jet 53b intersect. Then, inside the new excavation range 25a formed by the excavation range 25 and the widening portion 55, the high-pressure cement milk and compressed air and the earth and sand of the ground 1 are agitated by the jets 35 and 53, and FIG. As shown in c) and FIG. 6 (c), a tubular ground improvement body 45 having a thickness of 47 is formed. The ground inside the ground improvement body 45 remains as unimproved ground 37. As shown in FIG. 5D, the pulling up of the casing pipe 3e is completed when the ground improvement body 45 is formed over the entire length from the ground surface to a predetermined depth 19.

As described above, in the third embodiment, the casing pipe 3e having a double pipe structure in which the tip 15 of the outer casing 5 is longer than the tip 17 of the inner casing 7 is used, and the casing pipe 3e is pulled up from the ground 1 while being pulled up. High-pressure casing milk and compressed air are injected from the nozzles 33 and 51. As a result, the tubular ground improvement body 45 can be safely and efficiently constructed without generating excavated soil containing cement.

Further, by arranging the nozzle 33 and the nozzle 51 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7, the injection range of the jet 35 and the jet 53 is limited to the inside of the outer casing 5. be able to. Further, by injecting two jets 53, which are cross jets, inward in the radial direction of the casing pipe 3e, the inside of the excavation range 25 formed at the time of press-fitting the casing pipe 3e is cut and widened. A tubular ground improvement body 45 can be formed on 25a. Further, by injecting the jet 35 rearward in the rotational direction of the casing pipe 3e, the rotational force of the all-turning construction machine 11 can be reduced.

In the third embodiment, the improved rod 31 and the improved rod 49 are used in combination, but instead of the improved rod 31, another improved rod shown in FIG. 3 may be used. Further, the installation of the improved rod 31 is not essential. A casing pipe having only an improved rod 49 having a pair of nozzles 51 may be used to inject a jet 53 of high pressure cement milk and compressed air only radially inward. Further, the number of nozzles 33 and the pair of nozzles 51 installed is not limited to two, but may be one or more.

In the third embodiment, the two jets 53, which are cross jets, are injected inside the casing pipe in the radial direction, but the cross jets may be jetted outside in the radial direction of the casing pipe. If a cross jet is injected outward in the radial direction of the casing pipe, the outside of the excavation range 25 formed at the time of press fitting of the casing pipe is cut, and a tubular ground improvement body can be constructed in the new widened excavation range. it can.

Next, a fourth embodiment will be described. FIG. 7 is a diagram showing the configuration and operation of the casing pipe 3f. FIG. 7A is a cross-sectional perspective view showing the vicinity of the tip 13 of the casing pipe 3f. FIG. 7B is a vertical cross-sectional view of the casing pipe 3f at the positions of the improved rod 57 and the improved rod 63, and is a view showing a cross section taken along the arrow JJ of FIG. 7A. FIG. 7 (c) is a horizontal cross-sectional view in a state where the casing pipe 3f is press-fitted into the ground 1, and is a view showing a cross section by arrows H1-H1 of FIG. 5 (a). FIG. 7D is a horizontal cross-sectional view in a state where the casing pipe 3f is pulled up from the ground 1, and is a view showing a cross section by arrows H2-H2 in FIG. 5C.

As shown in FIGS. 7 (a) and 7 (b), the casing pipe 3f is provided with an improved rod 57 and an improved rod 63 in place of the improved rod 31 of the casing pipe 3 of the first embodiment. Is. In the casing pipe 3f, an improved rod 57 and an improved rod 63 are provided between the outer casing 5 and the inner casing 7. The improved rod 57 and the improved rod 63 are arranged side by side in the radial direction of the casing pipe 3f. A nozzle 59 is provided at the tip of the improved rod 57. A nozzle 65 is provided at the tip of the improved rod 63. The tips of the improved rod 57 and the improved rod 63 penetrate the bottom plate 9, and the nozzle 59 and the nozzle 65 have a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7 in the vicinity of the tip 13 of the casing pipe 3f. It is placed in the casing. The nozzle 59 and the nozzle 65 are arranged at two locations between the outer casing 5 and the inner casing 7, respectively, in a plan view.

The direction of the arrow F shown in FIGS. 5 and 7 is the rotation direction of the casing pipe 3f. The nozzle 59 is provided on the rear side of the improved rod 57 in the rotational direction of the casing pipe 3f. From the nozzle 59, a jet 61 composed of high-pressure cement milk and compressed air is injected in the circumferential direction of the casing pipe 3f and rearward in the rotational direction of the casing pipe 3f. The nozzle 65 is provided on the rear side of the improved rod 63 in the rotational direction of the casing pipe 3f. From the nozzle 65, a jet 67 composed of high-pressure cement milk and compressed air is injected in a direction forming a predetermined angle with the circumferential direction of the casing pipe 3f and rearward in the rotation direction of the casing pipe 3f.

In order to form the ground improvement body 45f using the casing pipe 3f, first, as shown in FIG. 5A, the casing pipe 3f is rotated in the direction indicated by the arrow F by using the all-turning construction machine 11. It is lowered in the direction indicated by the arrow G and press-fitted into the ground 1. At this time, as shown in FIG. 7C, the jet 61 is not injected from the nozzle 59. Further, the jet 67 is not injected from the nozzle 65.

By press-fitting the casing pipe 3f, the tubular excavation range 25 shown in FIG. 7C is formed in the ground 1. As shown in FIG. 5B, the press-fitting of the casing pipe 3f is completed when the tip 13 of the casing pipe 3f reaches a predetermined depth 19.

Next, as shown in FIG. 5C, the casing pipe 3f is rotated in the direction indicated by the arrow F and raised in the direction indicated by the arrow I to be pulled up from the ground 1. At this time, as shown in FIGS. 7 (a) and 7 (d), the jet 61 is injected from the nozzle 59 in the circumferential direction of the casing pipe 3f and rearward in the rotation direction of the casing pipe 3f. At the same time, the jet 67 is injected from the nozzle 65 in a direction forming a predetermined angle with the circumferential direction of the casing pipe 3f and backward in the rotation direction of the casing pipe 3f.

When the jet 61 and the jet 67 are injected while pulling up the casing pipe 3f, the jet 67 in the direction forming a predetermined angle with the circumferential direction of the casing pipe 3f, as shown in FIG. 7D, at the time of press-fitting the casing pipe 3f. The inside of the formed excavation range 25 is cut to form the widening portion 55. Then, inside the new excavation range 25a formed by the excavation range 25 and the widening portion 55, the high-pressure cement milk and compressed air and the earth and sand of the ground 1 are agitated by the jet 61 and the jet 67, and FIG. As shown in c) and FIG. 7 (d), a tubular ground improvement body 45f having a thickness of 47 is formed. The ground inside the ground improvement body 45f remains as unimproved ground 37. As shown in FIG. 5D, the pulling up of the casing pipe 3f is completed when the ground improvement body 45f is formed over the entire length from the ground surface to a predetermined depth 19.

As described above, in the fourth embodiment, the casing pipe 3f having a double pipe structure in which the tip 15 of the outer casing 5 is longer than the tip 17 of the inner casing 7 is used, and the casing pipe 3f is pulled up from the ground 1 while being pulled up. High-pressure casing milk and compressed air are injected from the nozzles 59 and 65. As a result, the tubular ground improvement body 45f can be safely and efficiently constructed without generating excavated soil containing cement.

Further, by arranging the nozzle 59 and the nozzle 65 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7, the injection range of the jet 61 and the jet 67 is limited to the inside of the outer casing 5. be able to. Further, by injecting the jet 67 in a direction forming a predetermined angle with the circumferential direction of the casing pipe 3f, the inside of the excavation range 25 formed at the time of press-fitting the casing pipe 3f is cut and the new excavation range is widened. A tubular ground improvement body 45f can be formed on 25a. Further, by injecting the jet 61 rearward in the rotational direction of the casing pipe 3f, the rotational force of the total turning construction machine 11 can be reduced.

In the fourth embodiment, the improved rod 57 having the nozzle 59 and the improved rod 63 having the nozzle 65 are used in combination, but two nozzles are provided on one improved rod and jets are made in two directions. May be injected. Further, the number of nozzles 59 and 65 installed is not limited to two, but may be one or more. Further, a jet in the circumferential direction and a jet in a direction forming a predetermined angle with the circumferential direction may be injected forward in the rotational direction of the casing pipe.

Next, a fifth embodiment will be described. FIG. 8 is a diagram showing the configuration and operation of the casing pipe 3g. FIG. 8A is a cross-sectional perspective view showing the vicinity of the tip 13 of the casing pipe 3g. FIG. 8B is a horizontal cross-sectional view in a state where the casing pipe 3g is press-fitted into the ground 1, and is a view showing a cross section by arrows C1-C1 of FIG. 1A. FIG. 8 (c) is a horizontal cross-sectional view in a state where the casing pipe 3 g is pulled up from the ground 1, and is a view showing a cross section by arrows C2-C2 shown in FIG. 1 (c).

The casing pipe 3g has a configuration in which a high-pressure water rod 69 is added to the casing pipe 3 of the first embodiment. As shown in FIG. 8, in the casing pipe 3g, an improved rod 31 and a high-pressure water rod 69 are provided between the outer casing 5 and the inner casing 7. A nozzle 71 is provided at the tip of the high-pressure water rod 69. The tip of the high-pressure water rod 69 penetrates the bottom plate 9, and the nozzle 71 is arranged at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7 in the vicinity of the tip 13 of the casing pipe 3g. The nozzles 71 are arranged at two locations between the outer casing 5 and the inner casing 7.

From the nozzle 71 of the high-pressure water rod 69, the high-pressure water 73 is injected in the circumferential direction of the casing pipe 3g and forward in the rotation direction of the casing pipe 3g.

In order to form the ground improvement body 21g using the casing pipe 3g, first, as shown in FIG. 1A, the casing pipe 3g is rotated in the direction indicated by the arrow A by using the all-turning construction machine 11. It is lowered in the direction indicated by the arrow B and press-fitted into the ground 1. At this time, as shown in FIG. 8B, the high-pressure water 73 is injected from the nozzle 71 of the high-pressure water rod 69 in the circumferential direction of the casing pipe 3g and forward in the rotation direction of the casing pipe 3g. The jet 35 is not injected from the nozzle 33 of the improved rod 31.

By press-fitting 3 g of the casing pipe, the excavation range 25 shown in FIG. 8B is excavated in a tubular shape in the ground 1. As shown in FIG. 1B, the press-fitting of the casing pipe 3g is completed when the tip 13 of the casing pipe 3g reaches a predetermined depth 19.

Next, as shown in FIG. 1C, the casing pipe 3g is rotated in the direction indicated by the arrow A and raised in the direction indicated by the arrow D to be pulled up from the ground 1. At this time, as shown in FIGS. 8A and 8C, a jet 35 of high-pressure cement milk and compressed air is transferred from a nozzle 33 provided near the tip 13 of the casing pipe 3g into a circle of the casing pipe 3g. It is injected in the circumferential direction and backward in the rotation direction of the casing pipe 3 g.

When the jet 35 is injected while pulling up the casing pipe 3 g, the high-pressure cement milk and compressed air and the earth and sand of the ground 1 are agitated by the jet 35 inside the tubular excavation range 25 formed when the casing pipe 3 g is press-fitted. Ru. Then, as shown in FIGS. 1 (c) and 8 (c), 21 g of a tubular ground improvement body having a thickness of 23 is formed. The ground inside the ground improved body 21 g remains as unimproved ground 37. As shown in FIG. 1D, the pulling up of the casing pipe 3g is completed when the ground improvement body 21g is formed over the entire length from the ground surface to a predetermined depth 19.

As described above, in the fifth embodiment, the casing pipe 3g having a double pipe structure in which the tip 15 of the outer casing 5 is longer than the tip 17 of the inner casing 7 is used, and the casing pipe 3g is press-fitted into the ground 1. , High-pressure water 73 is injected from the nozzle 71 in the circumferential direction of the casing pipe 3g and forward in the rotation direction of the casing pipe 3g. Then, while pulling up 3 g of the casing pipe from the ground 1, high-pressure cement milk and compressed air are injected from the nozzle 33. By injecting the high-pressure water 73 at the time of press-fitting, the ground 1 around the casing pipe 3 g is cut, so that the cement milk and the earth and sand of the ground 1 can be easily agitated by injecting high-pressure cement milk and compressed air at the time of pulling up. The injection pressure of compressed air can be reduced. Further, by injecting the high-pressure water 73 forward in the rotation direction, the frictional force with the ground 1 can be reduced, and the casing pipe 3g can be easily press-fitted into the ground 1. By injecting high-pressure cement milk and compressed air from the nozzle 33 while pulling up the casing pipe 3 g from the ground 1, the tubular ground improvement body 21 g can be safely and efficiently produced without generating excavated soil containing cement. Can be constructed in.

In the fifth embodiment, the injection range of the jet 35 is limited to the inside of the outer casing 5 by arranging the nozzle 33 at a height between the tip 15 of the outer casing 5 and the tip 17 of the inner casing 7. be able to. Further, by injecting the jet 35 rearward in the rotation direction of the casing pipe 3g, the rotational force of the total turning construction machine 11 can be reduced when the casing pipe 3g is pulled up.

In the fifth embodiment, the high-pressure water 73 was sprayed from the high-pressure water rod 69 in the circumferential direction of the casing pipe 3g and forward in the rotation direction of the casing pipe 3g, but the high-pressure water was sprayed downward. May be good. Further, the injection in the circumferential direction and the injection in the downward direction may be used in combination. The number of nozzles for injecting high-pressure water is not limited to two, and may be one or more.

Similar to the fifth embodiment, in the second to fourth embodiments, the high-pressure water rod 69 is added to the casing pipe, and the high-pressure water 73 is injected from the high-pressure water rod 69 when the casing pipe is rotationally press-fitted. You may.

In the fifth embodiment, the case where the injection direction of the high-pressure water 73 and the injection direction of the jet 35 of the high-pressure cement milk and the compressed air are different has been described, but the injection direction of the high-pressure water and the high-pressure cement milk and If the jet directions of the compressed air jets are the same, the high-pressure water rod 69 may not be provided. In this case, the high-pressure water rod and the improved rod are used in combination, and high-pressure water is injected from the improved rod when the casing pipe is press-fitted, and high-pressure cement milk and compressed air are injected when the casing pipe is pulled up.

Further, in the first to fifth embodiments, the casing pipe is rotationally press-fitted into the ground, but rotary drilling may be press-fitted. FIG. 9 is a diagram showing an example of a casing pipe used for press-fitting rotary drilling. 9 (a) is a vertical cross-sectional view of the vicinity of the tip of the casing pipe 3h, and FIG. 9 (b) is a horizontal cross-sectional view of the casing pipe 3h. 9 (c) is a vertical sectional view near the tip of the casing pipe 3i, and FIG. 9 (d) is a horizontal sectional view of the casing pipe 3h.

The casing pipe 3h shown in FIGS. 9 (a) and 9 (b) is a casing pipe 3 used in the first embodiment to which a bit 75 and a stabilizer 79 are added. The bits 75 are provided on the inner peripheral surface 77 side of the tip 15 of the outer casing 5 at predetermined intervals in the circumferential direction. The stabilizer 79 is provided on the inner peripheral surface 29 side of the tip 17 of the inner casing 7 at a predetermined interval in the circumferential direction.

The casing pipes 3i shown in FIGS. 9 (c) and 9 (d) also have the bit 75 and the stabilizer 79 added to the casing pipe 3 used in the first embodiment. The bits 75 are provided on the outer peripheral surface 27 side of the tip 15 of the outer casing 5 at predetermined intervals in the circumferential direction. The stabilizer 79 is provided on the inner peripheral surface 29 side of the tip 17 of the inner casing 7 at a predetermined interval in the circumferential direction.

When a casing pipe 3h or a casing pipe 3i provided with a bit 75 and a stabilizer 79 is used, the casing pipe is press-fitted into the ground 1 by rotary drilling in the step shown in FIG. 1 (a). As a result, the casing pipe can be press-fitted into the ground 1 in which an underground obstacle exists. Further, if the stabilizer 79 is provided on the inner peripheral surface 29 side of the inner casing 7 or the bit 75 is provided on the outer peripheral surface 27 side of the outer casing 5, an extra digging portion is formed inside or outside the casing pipe. , The width of the excavation range can be wider than that of the casing pipe 3 used in the first embodiment.

In the first to fifth embodiments, when the casing pipe is press-fitted into the ground 1 using the all-swivel construction machine 11, if the casing pipe is short, the casing is held with a pin or the like until a predetermined depth of 19 is reached. Press-fit while connecting the pipe. When a plurality of casing pipes are connected at the time of press fitting, the jet injection is temporarily suspended and the casing pipes are disassembled at the time of pulling up.

Next, the sixth embodiment will be described.
FIG. 10 is a diagram showing each process for constructing the ground improvement body 82 using the self-propelled construction machine 80 and the casing pipe 87. FIG. 10A is a diagram showing a state in which the casing pipe 87 has been transported, FIG. 10B is a diagram showing a state in which the casing pipe 87 is ready for press fitting, and FIG. 10C is a casing pipe. FIG. 10 (d) is a diagram showing a state in which the press-fitting of the casing pipe 87 is completed, FIG. 10 (d) is a diagram showing a state in which the casing pipe 87 is pulled up, and FIG. 10 (e) is a diagram showing a state in which the casing pipe 87 is pulled up. is there.

FIG. 11 is a diagram showing the configuration and operation of the casing pipe 87. FIG. 11A is a vertical cross-sectional view of the casing pipe 87 at the positions of the high-pressure pipes 90 and 91, and is an enlarged view of the range L shown in FIG. 10D. FIG. 11B is a horizontal cross-sectional view in a state where the casing pipe 87 is press-fitted into the ground 1, and is a view showing a cross section by arrows M1-M1 of FIG. 11A. 11 (c) is a horizontal cross-sectional view of the ground improvement body 82, and is a view showing a cross section by arrows M2-M2 of FIG. 11 (a).

In the first to fifth embodiments, the tubular ground improvement body was created by using the all-swivel construction machine 11 and the large-diameter casing pipe shown in FIGS. 1 and 5, but in the sixth embodiment, the tubular ground improvement body is constructed. , The ground improvement body 82 is constructed by using the self-propelled construction machine 80 shown in FIG. 10 and the casing pipe 87 having a small diameter.

The casing pipe 87 shown in FIGS. 10 and 11 has a weight and length that can be mounted on a vehicle. The casing pipe 87 has a smaller diameter than the casing pipe used in the first to fifth embodiments, and has a diameter of, for example, about 1.5 to 2 m. The length of the casing pipe 87 is, for example, five times or more the diameter. As shown in FIG. 11A, the casing pipe 87 has a double pipe structure having an outer casing 89 and an inner casing 88. The casing pipe 87 is provided with a bottom plate 96 at the positions of the tips of the outer casing 89 and the inner casing 88. The casing pipe 87 is made of steel.

As shown in FIGS. 11A and 11B, bits 75 are provided on the inner peripheral surface side of the tip of the outer casing 89 at predetermined intervals in the circumferential direction. Stabilizers 79 are provided on the inner peripheral surface side slightly above the tip of the inner casing 88 at predetermined intervals in the circumferential direction. A high-pressure pipe 90 and a high-pressure pipe 91 are provided between the outer casing 89 and the inner casing 88.

As shown in FIG. 11A, a nozzle 94 is provided at the tip of the high-pressure pipe 91. The nozzle 94 is arranged so as to penetrate the bottom plate 96. As shown in FIG. 11B, the nozzles 94 are arranged at two locations between the outer casing 89 and the inner casing 88 in a plan view.

Further, as shown in FIG. 11A, a pair of nozzles 92 are provided at the tip of the high pressure pipe 90. The pair of nozzles 92 are arranged on the same line in the vertical direction at predetermined intervals. The nozzle 92 is arranged so as to penetrate the outer casing 89 slightly above the bit 75. As shown in FIG. 11B, the nozzles 92 are arranged at two locations between the outer casing 89 and the inner casing 88 so as not to protrude from the double pipe in a plan view.

In order to form the ground improvement body 82 using the casing pipe 87, first, as shown in FIG. 10A, the casing pipe 87 is transported to a predetermined position by using the self-propelled construction machine 80. The self-propelled construction machine 80 is, for example, a rough terrain crane 81 in which a leader 83 is installed. The casing pipe 87 is gripped and transported by the guide portion 85 and the rotary drive portion 86 provided on the leader 83.

After completing the transportation of the casing pipe 87, the outriggers are projected to fix the position of the self-propelled construction machine 80. Then, as shown in FIG. 10B, the leader 83 is installed in the vertical direction by the rough terrain crane 81 to prepare for press-fitting the casing pipe 87.

Next, as shown in FIG. 10 (c), the casing pipe 87 is lowered while rotating in the direction indicated by the arrow K1 by using the rotation drive unit 86 of the leader 83, and the rotary drilling is press-fitted into the ground 1. At this time, the jets are not injected from the nozzle 92 and the nozzle 94 shown in FIG. 11A. The press-fitting is completed when the tip of the casing pipe 87 reaches a predetermined depth. As shown in FIG. 11B, when the casing pipe 87 is press-fitted, the excavated portion 98a by the casing pipe 87 main body and the surplus excavated portion 98b formed by the stabilizer 79 provided on the inner peripheral side of the inner casing 88 are formed. The excavation range 98 is formed.

Next, as shown in FIGS. 10 (d) and 11 (a), the rotary drive unit 86 of the reader 83 is used to rotate the casing pipe 87 in the direction indicated by the arrow K2 and raise it at a constant speed to raise the ground. Raise from 1. At this time, a supply pipe from a cement milk plant or a high pressure pump (not shown) is connected to the high pressure pipe 90 and the high pressure pipe 91. Then, as shown in FIG. 11A, a jet 95 composed of high-pressure cement milk and compressed air is injected downward from the nozzle 94 provided in the high-pressure pipe 91.

Further, as shown in FIG. 11A, a jet 93 made of high-pressure cement milk and compressed air is injected from a pair of nozzles 92 provided in the high-pressure pipe 90. Of the pair of nozzles 92, the upper nozzle 92 injects the jet 93 outward in the radial direction of the casing pipe 87 and diagonally downward. From the lower nozzle 92, the jet 93 is ejected obliquely upward and outward in the radial direction of the casing pipe 87. The pair of jets 93 are cross jets that intersect on the outside of the outer casing 89.

When the casing pipe 87 is rotated while being pulled up at a predetermined speed while injecting the jet 93 and the jet 95, as shown in FIGS. 11A and 11B, the excavation range formed at the time of press-fitting the casing pipe 87 is formed. The outside of the 98 is cut by a pair of jets 93, which are cross jets, to a position where the jets 93 intersect with each other to form a widening portion 97. Then, inside the new excavation range 99 formed by the excavation range 98 and the widening portion 97, the high-pressure cement milk and compressed air and the earth and sand of the ground 1 are agitated by the jet 93 and the jet 95 (high-pressure injection). Stirring method). Then, as shown in FIGS. 11A and 11C, a tubular ground improvement body 82 having a predetermined thickness is created in the excavation range 99.

As shown in FIG. 10E, the pulling up of the casing pipe 87 is completed when the ground improvement body 82 is constructed over the entire length from the ground surface to a predetermined depth. As shown in FIGS. 10 (e) and 11 (c), the ground inside the ground improvement body 82 remains as unimproved ground 84.

As described above, according to the method for creating the ground improvement body of the sixth embodiment, the casing pipe 87 having a double pipe structure having the outer casing 89 and the inner casing 88 is used, and the casing pipe 87 is pulled up from the ground 1. While injecting high-pressure casing milk and compressed air from the nozzle 92 and the nozzle 94. As a result, the tubular ground improvement body 82 can be safely and efficiently constructed without generating excavated soil containing cement.

Further, by injecting two jets 93, which are cross jets, to the outside in the radial direction of the casing pipe 87, the outside of the excavation range 98 formed at the time of press-fitting the casing pipe 87 is cut and widened to a new excavation range. A tubular ground improvement body 82 can be formed in 99.

In the sixth embodiment, the jet injection direction when pulling up the casing pipe 87 does not have to be the direction shown in FIG. Further, the number of nozzles 94 and a pair of nozzles 92 installed is not limited to two, but may be one or more.

The ground improvement body created by the first to sixth embodiments is used not only for hole wall stabilization measures to stabilize the hole wall when drilling holes in the ground, but also for liquefaction measures. Can be done.

FIG. 12 is a diagram showing an example in which the ground improvement body 21 is constructed as a countermeasure against liquefaction. In the example shown in FIG. 12, a plurality of ground improvement bodies 21 are formed on the ground 1 at predetermined intervals by using the method for creating the ground improvement body of the first embodiment. As a result, the ground improvement body 21 surrounds the unimproved ground to prevent shear failure during an earthquake and suppress damage due to liquefaction. The arrangement of the ground improvement bodies is not limited to that shown in FIG. 12, and the ground improvement bodies may be arranged in a wall shape or a grid pattern.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified examples or modified examples within the scope of the technical idea disclosed in the present application, and these also naturally belong to the technical scope of the present invention. Understood.

1, 101 ……… Ground 3, 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 87 ……… Casing pipe 5, 89 ……… Outer casing 7, 88 ……… Inner casing 9 , 96 ……… Bottom plate 11 ……… Full swivel construction machine 13, 15, 17 ……… Tip 19 ……… Depth 21, 21a, 21b, 21c, 21d, 21g, 45, 45f, 82, 103 ……… Ground improvement 23, 47 ……… Thickness 25, 25a, 98, 99 ……… Excavation range 27 ……… Outer surface 29, 77 ……… Inner peripheral surface 31, 31a, 31b, 39, 49, 57, 63 ……… Improved rods 33, 33a, 33b, 41, 51, 51a, 51b, 59, 65, 71, 92, 94 ……… Nozzles 35, 35a, 35b, 43, 53, 53a, 53b, 61, 67 , 93, 95 ……… Jet 37, 84 ……… Unimproved ground 55, 97 ……… Widening part 69 ……… High pressure water rod 73 ……… High pressure water 75 ……… Bit 79 ……… Stabilizer 80… …… Self-propelled construction machine 81 ………… Rough terrain crane 83 ………… Leader 85 ………… Guide part 86 ………… Rotary drive part 90, 91 ………… High-pressure piping 98a ………… Excavation part 98b ………… Extra Digging part 105 ……… Drilling part 107 ………… Pile

Claims (9)

It is a method of creating a ground improvement body by the high-pressure injection stirring method.
Step a of rotary press-fitting or rotary drilling press-fitting of a steel casing pipe having a double pipe structure having an outer casing and an inner casing into the ground to a predetermined depth.
A step b in which high-pressure cement milk and compressed air are injected from a nozzle provided near the tip of the steel casing pipe, and the steel casing pipe is rotated and pulled up from the ground.
A method for creating a ground improvement body, which is characterized by being equipped with. The method for creating a ground improvement body according to claim 1, wherein in the step b, the high-pressure cement milk and compressed air are injected in the circumferential direction of the steel casing pipe. The method for creating a ground improvement body according to claim 1 or 2, wherein in the step b, the high-pressure cement milk and compressed air are jetted vertically downward. Any one of claims 1 to 3, wherein in the step b, the high-pressure cement milk and compressed air are injected in the radial direction of the steel casing pipe so that the two jets intersect. Method for creating a ground improvement body described in. The first to fourth aspects of the step b, wherein the high-pressure cement milk and compressed air are injected in a direction forming a predetermined angle with the circumferential direction of the steel casing pipe in a plan view. The method for creating a ground improvement body described in any of the above. The method for creating a ground improvement body according to any one of claims 1 to 5, wherein the tip of the outer casing is located below the tip of the inner casing. Any of claims 1 to 6, wherein in the step a, high-pressure water is sprayed in the circumferential direction and / or downward direction of the steel casing pipe in the vicinity of the tip of the steel casing pipe. Method for creating a ground improvement body described in. A casing pipe used to create a ground improvement body by the high-pressure injection stirring method.
A double pipe having an outer casing and an inner casing,
A nozzle arranged so as not to protrude from the double pipe in a plan view near the tip of the outer casing,
Equipped with
A casing pipe characterized in that high-pressure cement milk and compressed air are injected from the nozzle. The casing pipe according to claim 8, wherein the tip of the outer casing has a shape longer than the tip of the inner casing, and the nozzle is arranged between the outer casing and the inner casing in a plan view.

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