JP2018062806A - Method for forming soil cement pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a soil cement pile without detaching a rotary drive device temporarily installed on an upper end of a hollow rotary shaft, from the hollow rotary shaft until core material such as a steel pipe is inserted in the final process.SOLUTION: A hollow rotary shaft 1 is provided with a cement milk radial discharge hole 5 and a cement milk axial discharge hole 6. When the hollow rotary shaft 1 is rotated to penetrate and drill into the ground G, cement milk 8A is discharged into the ground from the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 to form soil cement layer 7 in which excavated soil and the cement milk 8A are agitated around the hollow rotation shaft 1. When pulling up the hollow rotary shaft 1, the cement milk 8A is discharged axially downward from a lower end portion of the hollow rotary shaft 1 from the cement milk axial discharge hole 6 provided at the lower end portion of the hollow rotary shaft 1, whereby the cement milk layer 8 is formed at the center portion of the soil cement layer 7. Thereafter, core material 9 is inserted into the cement milk layer 8.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a method for forming a soil cement pile employed for ground improvement of a small-scale building.

  As shown in FIG. 12, for example, a soil cement pile S formed in the ground G as a cast-in-place pile is used as a foundation for a small-scale building P such as a house on the third floor or below. Since it is made by mixing the excavated earth and sand and cement milk at the site, there is a problem that the bearing capacity is slightly inferior.

  Patent Documents 1 and 2 listed below can be cited as patent documents related to a method for forming a typical soil cement pile that reinforces the supporting force.

  Each of the soil cement piles described in the patent literature is formed with a cement milk layer in the center of the soil cement layer and a core material such as a steel pipe inserted in the center. The support capacity of the soil cement pile can be increased by the cement milk layer with high compressive strength built into the soil cement layer and the steel pipe core material, but the difficulty is that the formation method is quite cumbersome and expensive to form. There is.

  The method for forming a soil cement pile described in both patent documents goes through the following steps. First, as a first step, a rotary drive device such as an earth auger is connected to the upper end portion of the hollow rotary shaft (stirring rod), and the hollow rotary shaft is driven into the ground by rotationally driving the hollow rotary shaft by the rotary drive device. Cement milk that has been intruded and injected into the hollow rotary shaft is discharged into the excavated sediment, and stirred by the rotation of the hollow rotary shaft (stirring rod). A mixed soil cement layer is formed.

  Next, as a second step, the rotary drive device that rotationally drives the hollow rotary shaft (stirring rod) is removed from the upper end of the hollow rotary shaft, and a core material such as a steel pipe is removed from the upper end opening of the hollow rotary shaft. Insert to the lower end of.

  After that, as a third step, a rotation driving device is connected to the upper end of the hollow rotating shaft (stirring rod) again, and the hollow rotating shaft (stirring rod) is moved upward from the ground while rotating the hollow rotating shaft. Pull up.

  By going through the above first to third steps, the soil cement has a three-layer structure comprising a soil cement layer in the ground, a cement milk layer at the center, and a steel pipe core material inserted at the center. A pile is formed.

  According to this method for forming a soil cement soil pile, first, in the first step, a heavy earthing auger or other rotary drive device connected to the upper end of the hollow rotary shaft (stirring rod) is temporarily attached in the second step. It must be removed from the upper end of the hollow rotating shaft, and in the third step, the heavy rotary drive once removed must be connected to the upper end of the hollow rotating shaft again. While repeating the first to third steps one by one, to form a large number of soil cement piles, it is very expensive to form, and the heavy rotary drive device is removed from the upper end of the hollow rotary shaft, The work efficiency was extremely poor because the work of re-installation had to be repeated.

JP, 2014-31634, A JP 2012-21310 A

  In view of the above circumstances, the present invention provides a rotary drive device once attached to the upper end portion of a hollow rotary shaft without removing it from the hollow rotary shaft halfway until a core material such as a steel pipe in the final stroke is inserted. By forming the soil cement pile, it is possible to greatly reduce the process of forming the soil cement pile, and this allows the soil cement pile to be formed efficiently and in a short time and at low cost. It aims at providing the formation method of this.

  If the means for achieving the above object is shown with reference numerals in the drawings, the method for forming a soil cement pile according to the invention described in claim 1 projects from the hollow rotary shaft 1 in a radial direction perpendicular thereto. A stirring blade 2 provided below, a drilling blade 3 provided below the stirring blade 2 and protruding in the radial direction, and a drilling head 4 provided protruding in the axial direction at the lower end of the hollow rotary shaft 1. While discharging the cement milk injected into the hollow rotary shaft 1, the hollow rotary shaft 1 is rotated to penetrate into the ground, and the soil cement pile in which the excavated sediment and cement milk are stirred around the hollow rotary shaft 1 A method for forming a soil cement pile in which the cement milk radial discharge hole 5 for discharging the cement milk 8A (FIG. 10) in the radial direction perpendicular to the hollow rotating shaft 1 is formed. Cement milk diameter A cement milk axial discharge hole 6 for discharging cement milk 8A (FIG. 11) downward from the lower end of the hollow rotary shaft 1 in the axial direction is provided below the direction discharge hole 5, and the hollow rotary shaft 1 is rotated. Then, while the hollow rotary shaft 1 is penetrated into the ground G and excavated, the cement milk 8A is discharged into the ground from the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and excavated sediment around the hollow rotary shaft 1 And the cement milk 8A are stirred (FIGS. 9A, 9B, and 10). When the hollow rotary shaft 1 reaches a predetermined depth, the hollow rotary shaft 1 is moved upward. The cement milk 8A is discharged axially downward from the lower end portion of the hollow rotary shaft 1 through the cement milk axial discharge hole 6 provided at the lower end portion of the hollow rotary shaft 1 while being pulled up. Forming a reinforcement milk layer 8 (FIG. 9 (c), the FIG. 9 (d), the FIG. 11), and the subsequent formed by inserting the core 9 (FIG. 9 (e)) in cement milk layer 8 in the configuration.

  The invention according to claim 2 is a method for forming a soil cement pile according to claim 1, wherein the hollow rotary shaft 1 is pulled up without rotating when the hollow rotary shaft 1 is pulled up. Yes.

  According to a third aspect of the present invention, in the method for forming a soil cement pile according to the first aspect, when the hollow rotary shaft is pulled upward, the hollow rotary shaft 1 is pulled up while rotating forward or reverse. It is said.

  The invention according to claim 4 is the method for forming a soil cement pile according to any one of claims 1 to 3, wherein the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and the hollow rotary shaft are provided. The agitating blade 2 provided in the radial direction 1 is configured to be adjacent to the circumferential direction of the hollow rotary shaft 1 and provided at the same axial height level.

  The invention according to claim 5 is the method for forming a soil cement pile according to any one of claims 1 to 4, wherein the excavation head 4 provided at the lower end portion of the hollow rotary shaft 1 has a lower end portion of the hollow rotary shaft 1. The cement milk axial discharge hole 6 provided at the lower end portion of the hollow rotary shaft 1 is closed when the excavation head 4 moves upward and is supported by the excavation head support shaft 10 that penetrates in the radial direction. The cement milk axial discharge hole 6 is opened when the excavation head 4 is moved downward.

  The invention according to claim 6 is the method of forming the soil cement pile according to any one of claims 1 to 5, wherein the vertical guide frame guides the vertical movement of the excavation head 4 to the lower end portion of the hollow rotary shaft 1. 11 is provided.

  According to a seventh aspect of the present invention, in the method for forming a soil cement pile according to any one of the first to sixth aspects, when the hollow rotary shaft 1 is penetrated into the ground and excavated in the ground, excavation is performed. The excavation head 4 is moved up by the earth pressure of the soil, and the cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is closed.

  The invention according to claim 8 is the method for forming a soil cement pile according to any one of claims 1 to 7, wherein the hollow rotary shaft 1 is pulled upward after the hollow rotary shaft 1 reaches a predetermined depth. Is configured to be released from the earth pressure of the excavated soil, the excavation head 4 is moved downward, and the cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is opened.

  The invention according to claim 9 is the method for forming a soil cement pile according to any one of claims 1 to 8, wherein the stirring blade 2 attached to the hollow rotary shaft 1 so as to protrude in the radial direction is provided below the stirring blade 2. The stirring auxiliary blade 12 that protrudes in the radial direction longer than the radial protruding length of the agitating blade 2 and the excavating blade 3 is located between the upper and lower faces of the excavating blade 3 that is also provided protruding in the radial direction. 1 is configured such that the rotational force of the hollow rotary shaft 1 is not transmitted.

  Next, the effects of the present invention will be specifically described with reference to the drawings. First, according to the method for forming a soil cement pile according to the first aspect of the present invention, the cement milk radial discharge hole 5 for discharging the cement milk 8A to the hollow rotating shaft 1 in the radial direction perpendicular thereto, and the cement A cement milk axial discharge hole 6 is provided below the milk radial discharge hole 5 to discharge cement milk 8A axially downward from the lower end of the hollow rotary shaft 1, and the hollow rotary shaft 1 is rotated. Cement milk 8A is discharged into the ground through a cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 while the hollow rotary shaft 1 is penetrating into the ground G, and excavated sediment and cement around the hollow rotary shaft 1 are discharged. A soil cement layer 7 in which milk 8A is agitated is formed, and when the hollow rotary shaft 1 reaches a predetermined depth, the center provided at the lower end of the hollow rotary shaft 1 is lifted upward. A cement milk layer 8 is formed in the center of the soil cement layer 7 by discharging cement milk 8A from the lower end portion of the hollow rotary shaft 1 through the axial discharge hole 6 in the axial direction, and thereafter the cement milk layer 8 is formed. Since the core material 9 is inserted, the heavy rotational drive device 13 is connected to the upper end portion of the hollow rotary shaft 1 in all steps until the core material 9 is inserted into the cement milk layer 8 in the final process. The soil cement pile can be formed by this, and this can greatly reduce the process of forming the soil cement pile, thereby forming the soil cement pile efficiently and in a short time. Can do.

  According to the second aspect of the present invention, the cement milk 8A is discharged from the lower end portion of the hollow rotary shaft 1 downward in the axial direction through the cement milk axial discharge hole 6 provided at the lower end portion of the hollow rotary shaft 1. When the shaft 1 is pulled upward, the hollow rotary shaft 1 is lifted without rotating. Therefore, the stirring blade 2 and the excavating blade 3 protruding from the outer periphery of the hollow rotary shaft 1 are used as the soil cement layer 7. The cement milk layer 8 formed at the center of the soil cement layer 7 is pulled up while receiving resistance, and the cement milk axial discharge hole 6 in the vicinity of the excavation head 4. Since the cement milk 8A in the hollow portion 14 of the hollow rotary shaft 1 is discharged from a static pressure state, the surrounding soil cement 7A is hardly mixed into the cement milk 8A. Is, it is possible to form high-quality cement milk layer 8.

  According to the invention of claim 3, when the hollow rotary shaft is pulled upward, the hollow rotary shaft is pulled up while rotating forward or reversely. 2 and the excavating blade 3 can be pulled up smoothly without receiving much resistance of the soil cement layer 7.

  According to the invention of claim 4, the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and the stirring blade 2 provided radially in the hollow rotary shaft 1 are Since they are provided adjacent to each other in the circumferential direction at the same axial height level, the cement milk 8A discharged from the cement milk radial discharge hole 5 is immediately stirred by the stirring blade 2, and the cement milk 8A and the excavated earth and sand are separated. It will be efficiently stirred and mixed.

  According to the invention which concerns on Claim 5, the excavation head 4 provided in the lower end part of the hollow rotating shaft 1 can be moved up and down by the excavation head support shaft 10 provided through the lower end part of the hollow rotating shaft 1 in the radial direction. The cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is closed when the excavation head 4 moves upward, and the cement milk axial discharge hole 6 opens when the excavation head 4 moves downward. Therefore, as the excavation head 4 moves up and down, the cement milk axial discharge hole 6 can be opened and closed smoothly, and its configuration is also simple.

  According to the sixth aspect of the present invention, since the upper and lower guide frames 11 for guiding the vertical movement of the excavation head 4 are provided at the lower end portion of the hollow rotary shaft 1, the excavation head is rotated during the rotation of the hollow rotary shaft 1. Even if 4 receives a large load such as cutting earth and sand and the load is applied to the excavation head support shaft 10, the load is received by the upper and lower guide frames 11, and the excavation head support shaft 10 is destroyed. Absent.

  According to the invention of claim 7, when the hollow rotary shaft 1 is penetrated into the ground to excavate the ground, the excavation head 4 moves upward by the earth pressure of the excavated soil and rotates hollow. Since the cement milk axial discharge hole 6 provided at the lower end portion of the shaft 1 is closed, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 is separated from the cement milk axial discharge hole 6. Since it cannot be discharged, it will be discharged from the cement milk radial discharge hole 5 which is a horizontal hole formed in the hollow rotary shaft 1 into the excavated earth and sand excavated by the excavating blade 3. The cement milk 8A and the excavated earth and sand are agitated by the agitating blade 2, and the soil cement layer 7 can be formed.

  According to the eighth aspect of the present invention, when the hollow rotary shaft 1 is pulled upward after the hollow rotary shaft 1 reaches a predetermined depth, the excavation head 4 moves downward by being released from the earth pressure of the excavated soil. Then, a cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is opened, and a soil cement layer formed by discharging cement milk 8A from the cement milk radial discharge hole 5 of the hollow rotary shaft 1 7, the discharge resistance with respect to the cement milk radial discharge hole 5 is increased, and therefore, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 has a low discharge resistance in the cement milk axial discharge hole. 6 is discharged downward in the axial direction, and as the hollow rotary shaft 1 is pulled upward, the cement milk layer 8 is directed upward at the center of the soil cement layer 7. It can be formed.

  According to the ninth aspect of the present invention, the agitating blade 2 attached to the hollow rotary shaft 1 so as to protrude in the radial direction and the excavation blade 3 provided below and in the same manner in the radial direction are vertically opposed to each other. Thus, the auxiliary stirring blade 12 that protrudes in the radial direction longer than the protruding length in the radial direction of the stirring blade 2 and the excavating blade 3 is attached to the hollow rotary shaft 1 so that the rotational force of the hollow rotary shaft 1 is not transmitted. Therefore, the stirring auxiliary blade 12 does not transmit the rotational force of the hollow rotating shaft 1 to the stirring blade 2 that rotates integrally with the hollow rotating shaft 1 and exerts a stirring action, so that it is in an idle state. In addition, since the protruding amount in the radial direction of the auxiliary stirring blade 12 is larger than that of the stirring blade 2 and the excavating blade 3, the tip of the auxiliary stirring blade 12 is the hole of the excavation hole excavated by the excavating blade 3. I got into the wall a little bit, The stirring auxiliary blade 12 is in a fixed state, and the cement milk 8A between the stirring blade 2 and the stirring auxiliary blade 12 is caused by the synergistic action of the rotating stirring blade 2 and the stirring auxiliary blade 12 in the fixed state. The excavated earth and sand will be efficiently stirred and mixed. In other words, the auxiliary stirring blade 12 will assist the stirring action of the stirring blade 2, and a high-quality soil cement layer 7 can be formed.

It is the whole soil cement pile formation apparatus front view. It is a principal part enlarged front view of the part enclosed by A of FIG. 1, and is a figure which shows the use condition by which the cement milk axial direction discharge hole was closed. It is the principal part expanded side view. It is an expansion perspective view of the principal part. (A) is a vertical side view of the main part. (B) is the BB sectional drawing of (a), and is a vertical front view of the principal part. It is a figure similar to FIG. 2, and is a figure which shows the use condition by which the cement milk axial direction discharge hole was opened. It is an expansion perspective view of the principal part. (A) is a vertical side view of the main part. (B) is CC sectional view taken on the line of (a), and is the longitudinal front view of the principal part. It is process explanatory drawing which shows the formation process of the soil cement pile which concerns on this invention which consists of (a)-(e). It is action | operation description of the part enclosed with X of the process drawing of (a) of FIG. It is action | operation description of the part enclosed with XI of the process drawing of FIG.9 (c). It is explanatory drawing which shows the building in which a soil cement pile is generally formed.

  Below, the formation method of the soil cement pile concerning this invention is demonstrated concretely with reference to drawings.

  FIG. 1 is a front view showing the whole of a soil cement pile forming apparatus, and a ground auger having a known structure along a leader 17 supported by a backstay 16 by a construction heavy machine 15 such as a crawler crane installed on the ground G. The hollow rotary shaft 1 is driven to move up and down in the ground G in a state where the rotary drive device 13 is connected to the upper end of the hollow rotary shaft 1 by a connecting jig 18 such as Monken. A cement milk pouring bowl 19 is connected to the upper end of the hollow rotary shaft 1. In addition, a roll prevention arm 20 that prevents the hollow rotary shaft 1 from rolling is attached to the lower end portion of the leader 17.

  FIGS. 2 and 3 show that the bottom part of the hollow rotary shaft 1 surrounded by A in FIG. 1 is provided with a soil cement pile forming member, which is the main part of the present invention, and the cement milk axial discharge is described later. The use state in which the hole 6 is closed is shown.

  That is, the stirring blades 2 and 2 projecting radially from the hollow rotating shaft 1 are provided at the lower end of the hollow rotating shaft 1, and the arm 3a projecting from the hollow rotating shaft 1 in the radial direction is attached to the lower side. An excavation blade 3 including an excavation bit 3 b is provided, and an excavation head 4 is attached to the lower end portion of the hollow rotary shaft 1. When the excavation head 4 penetrates into the ground G to form the excavation hole H, the excavation head 4 receives the earth pressure as will be described later and is in a position where it has slightly moved upward, thereby closing the cement milk axial discharge hole 6. It is in the state. At the lower end of the hollow rotary shaft 1, a cement milk radial discharge hole 5 which is a horizontal hole is provided adjacent to the circumferential direction of the stirring blade 2 and the hollow rotary shaft 1 at the same axial height level. Thus, the cement milk 8A discharged from the cement milk radial direction discharge hole 5 is immediately stirred by the stirring blade 2, and the cement milk 8A and the excavated earth and sand are efficiently stirred and mixed. (See Figure 10)

  Further, as shown in FIGS. 2 and 3, the upper and lower sides of the agitating blade 2 that protrudes in the radial direction from the hollow rotary shaft 1 and the excavation blade 3 that is provided below the stirring blade 2 and protrudes in the radial direction. Auxiliary stirring blades 12 that are in the opposite direction and project in the radial direction longer than the radial protruding lengths of the stirring blade 2 and the excavating blade 3 are prevented from transmitting the rotational force of the hollow rotating shaft 1 to the hollow rotating shaft 1 by the mounting portion. To be attached. That is, a pair of annular locking projections 12a are fixed to the hollow rotary shaft 1 with a space therebetween, and the mounting ring 12b is rotatably attached to the hollow rotary shaft 1 between the two annular locking projections 12a and 12a. A pair of arms 12c projecting in the radial direction is fixed to the mounting wheel 12b, and a contact plate that contacts the wall surface of the excavation hole 21 is fixed to the distal ends of both arms 12c and 12c. Since the auxiliary stirring blade 12 has the above structure, the hollow rotary shaft 1 rotates. However, the auxiliary stirring blade 12 has its mounting portion 12b prevented from moving up and down by the upper and lower locking projections 12a, and the mounting portion 12b. Is fitted into the outer peripheral surface of the hollow rotary shaft 1 so as to be able to rotate freely, and the amount of radial protrusion of the stirring auxiliary blade 12 is larger than that of the stirring blade 2 and the excavating blade 3, and the tip of the stirring auxiliary blade 12 Since the abutting plate 12d is in a slight pressure contact with the hole wall of the excavation hole H, the auxiliary stirring blade 12 does not rotate following the rotation of the hollow rotary shaft 1, but substantially does not rotate. It is designed to remain stationary.

  That is, in the case of only the stirring blade 2, as it rotates, cement milk or cutting earth and sand in contact with the stirring blade 2 is pushed and moved in the rotation direction of the stirring blade 2, and does not exhibit sufficient stirring action, but rotates. By providing the stirring blade 2 and the stationary auxiliary stirring blade 12, the cement milk and the cutting earth and sand are pushed by the stirring blade 2 in the rotating direction to move, whereas the cement milk and the cutting earth and sand are in a stationary state. The stirrer blades 12 are prevented from moving in the rotation direction, and the stirrer blades 12 assist the stir operation of the stirrer blades 2. The stirring ability can be improved by the synergistic action.

  4 to 5 show enlarged views around the excavation head 4 attached to the lower end portion of the hollow rotary shaft 1, and the tubular valve body 21 in which the lower excavation head 4 is provided with respect to the hollow rotary shaft 1. FIG. Are manufactured separately and are formed integrally by welding w.

  A cylindrical valve body 22 that can move up and down is fitted inside the hollow rotary shaft 1 and the cylindrical valve main body 21, and the cylindrical valve body 22 has a pair of vertically elongated slots 23 and orthogonal to this. A pair of valve holes 24 are provided in the circumferential direction, and the excavation head support shaft 10 penetrates the cylindrical valve body 21 in the radial direction through the pair of long holes 23 and is fixed by a lock nut 25. The excavation head 4 moves up and down by the vertical length of the long hole 23 via the excavation head support shaft 10 inserted into the long hole 23, and the cylindrical valve body 21 is provided at the lower end portion of the cylindrical valve body 22. A valve lid 26 for opening and closing the lower end opening 21a is fixed. In addition, the said long hole 23 and the valve hole 24 comprise the cement milk axial direction discharge hole 6 which is the principal part of this invention as mentioned later.

  As shown in the drawing, the excavation head 4 is formed in a horizontal edge 4a having an upper edge that is horizontal, and a lower edge is formed in a mountain-shaped inclined edge 4b that is inclined as seen by the pointed head at the center. It is formed in the front triangular plate-shaped excavation head 4. The excavation head 4 is fixed to the valve lid 26 by the horizontal edge 4a. A hard super hard material 27 is fixed to the tip of the angled inclined edge 4b.

  A pair of downward U-shaped upper and lower guide frames 11 are fixed to the outer peripheral surface of the cylindrical valve body 21, and both end portions 4 c of the triangular plate-shaped excavation head 4 are fitted to the upper and lower guide frames 11 so as to be movable up and down. Even if the excavation reaction force is received during excavation work of the excavation head 4, the cutting reaction force is received by the upper and lower guide frames 11, and the excavation head is not affected by the excavation head support shaft 10 that supports the excavation head 4. 4 is smoothly guided up and down.

  4 and 5 are positions where the excavation head 4 is moved upward as will be described later, whereby the valve lid 26 abuts against the lower end opening 21a of the tubular valve body 21 and closes the opening 21a. The cement milk axial discharge hole 6 including the long hole 23 and the valve hole 24 provided in the circumferential direction is closed.

  6 includes the same configuration diagram as FIG. 2, and therefore, the same components shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted, but the difference is that in FIG. As shown in FIG. 6, the excavation head 4 is moved upward and the cement milk axial discharge hole 6 is closed. In FIG. It is in an open state.

  7 and 8 also have the same configuration diagram as FIGS. 4 and 5, and therefore, the same components shown in FIGS. 4 and 5 are denoted by the same reference numerals and the description thereof will be omitted. 4 and 5, the excavation head 4 is moved upward as described above and the cement milk axial discharge hole 6 is closed. However, in FIG. 7 and FIG. 4 moves downward and the valve lid 26 moves downward from the lower end opening 21a of the cylindrical valve body 21 so that the lower end opening 21a of the cylindrical valve body 21 is opened and provided in the cylindrical valve body 22. The long hole 23 and the valve hole 24 opened from the cylindrical valve body 21 are opened, the cement milk axial discharge hole 6 including the long hole 23 and the valve hole 24 is opened, and the hollow portion 14 of the hollow rotary shaft 1 is opened. And the inside of the excavation hole are in communication.

  FIG. 9 is a process explanatory view showing a process for forming a soil cement pile according to the present invention. First, as shown in the process diagram of (a), excavation hole H is excavated through underground G with excavation blade 3, agitation blade 2 and agitation auxiliary blade 12 attached to the lower end of hollow rotary shaft 1. The action of the portion surrounded by X at the lower end of the hollow rotary shaft 1 at this time will be described. As shown in FIG. 10, the excavation head 4 receives the earth pressure in the excavation hole H. The valve lid 26 that moves upward and is integrated with the valve lid 26 closes the lower end opening 21 a of the cylindrical valve body 21, and the long hole 23 and the valve hole 24 provided in the cylindrical valve body 22 inside the cylindrical valve body 21. Since the cement milk axial discharge hole 6 is closed, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 is discharged from the cement milk radial discharge hole 5 provided on the side wall of the hollow rotary shaft 1. As shown by the arrow, excavated earth and sand inside the excavation hole H excavated by the excavation blade 3 The cement milk 8A and the cut earth and sand are stirred and mixed by the stirring blade 2 and the stirring auxiliary blade 12 to form a soil cement layer 7 having a diameter of, for example, 30 to 40 cm around the hollow rotary shaft 1. .

  Then, as shown in the process diagram of FIG. 9B, the hollow rotary shaft 1 advances to a predetermined depth while forming a soil cement layer 7 at the lower end thereof.

  Then, as shown in FIG. 9C, when the hollow rotary shaft 1 is cut to a predetermined depth, as shown in FIG. 1, the rotary drive device 13 connected to the upper end portion of the hollow rotary shaft 1 and the like. As a result, the hollow rotary shaft 1 is pulled upward, but the excavation head 4 at the lower end of the hollow rotary shaft 1 moves from the earth pressure in the drill hole H as the hollow rotary shaft 1 is pulled upward. The operation of the portion surrounded by XI at the lower end of the hollow rotary shaft 1 at that time will be described. As shown in FIG. 11, the excavation head 4 is released from the earth pressure in the excavation hole H. The valve lid 26 integrated therewith moves downward from the lower end opening 21 a of the cylindrical valve body 21 to open the lower end opening 21 a, and the cylindrical valve body inside the cylindrical valve body 21. The cement milk axial discharge hole 6 comprising a long hole 23 and a valve hole 24 provided in 22 is opened. It is.

  From this point, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 is a soil cement layer 7 formed by discharging the cement milk 8A from the cement milk radial discharge hole 5 of the hollow rotary shaft 1. The cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 with respect to the high discharge resistance with respect to the cement milk radial direction discharge hole 5 is discharged in the cement milk axial direction with a low discharge resistance as indicated by an arrow. As the hollow rotary shaft 1 is pulled upward from the holes 6 and 6a, the cement milk layer 8 is formed upward in the center of the soil cement layer 7. .

  When the hollow rotary shaft 1 is pulled upward, the hollow rotary shaft 1 may be lifted while rotating or may be lifted as it is without being rotated. However, the hollow rotary shaft 1 may be pulled like a rod without rotating. If lifted, the stirring blade 2, the stirring auxiliary blade 12 and the excavation blade 3 protruding from the outer periphery of the hollow rotary shaft 1 are lifted while receiving the resistance of the soil cement layer 7, and a considerable weight resistance. The cement milk layer 8 formed in the central portion of the soil cement layer 7 is hollowly rotated in a static pressure state from the cement milk axial discharge holes 6 (23) and (24) in the vicinity of the excavation head 4. Since the cement milk 8A in the hollow portion 14 of the shaft 1 is discharged, the surrounding soil cement 7A is hardly mixed into the cement milk 8A, and a good quality cement milk is formed. It is possible to form the 8.

  On the other hand, if the hollow rotary shaft 1 is pulled up while being rotated forward or reverse, the stirring blade 2, the auxiliary stirring blade 12 and the excavating blade 3 protruding from the outer periphery of the hollow rotary shaft 1 are resistant to the soil cement layer 7. Can be lifted smoothly without receiving much.

  Then, by pulling the hollow rotary shaft 1 completely upward from the ground G, as shown in the process diagram of FIG. 9 (d), the soil cement layer 7 is formed in the excavation hole, and the cement milk layer 8 is formed at the center thereof. Will be formed.

  Then, as a final step, the core material 9 such as a steel pipe having a diameter of about 5 to 6 cm is inserted into the cement milk layer 8 by manual work or appropriate known insertion means in a state where the cement milk layer 8 is not yet cured. Thus, the soil cement pile of the present invention is formed.

  Thus, in all the processes until the core material 9 is inserted into the cement milk layer 8 in the final process, the formation work of the soil cement pile is performed with the heavy rotational drive device 13 connected to the upper end of the hollow rotary shaft 1. Therefore, the process of forming the soil cement pile can be greatly reduced, whereby the soil cement pile can be formed efficiently in a short time and at low cost.

DESCRIPTION OF SYMBOLS 1 Hollow rotary shaft 2 Agitation blade 3 Excavation blade 4 Excavation head 5 Cement milk radial direction discharge hole 6 Cement milk axial direction discharge hole 7 Soil cement layer 8 Cement milk layer 9 Core material 10 Excavation head support shaft 11 Vertical guide frame 12 Stirring assistance Wing 13 Rotation drive device

The invention according to claim 4 is the method for forming a soil cement pile according to any one of claims 1 to 3, wherein the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and the hollow rotary shaft are provided. The excavating blade 3 provided in the radial direction 1 is configured to be adjacent to the circumferential direction of the hollow rotary shaft 1 and provided at the same axial height level.

According to the invention according to claim 4, the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and the excavating blade 3 provided radially in the hollow rotary shaft 1 are Since the cement milk 8A is provided adjacent to the circumferential direction at the same axial height level, the cement milk 8A is immediately discharged into the excavated sediment that is excavated by the excavating blade 3, and the cement milk radial discharge hole 5 is provided. cement milk 8A ejected during excavation soil from will be the cement milk 8A and drilling soil is stirred 攪拌翼2 is efficiently stirred mixture.

According to the invention of claim 7, when the front SL in by penetrating the idling shaft 1 in the ground excavating underground, the hollow rotary shaft drilling head 4 is moved upward by earth pressure drilling soil Since the cement milk axial discharge hole 6 provided at the lower end of 1 is closed, the cement milk 8A pumped and injected into the hollow part 14 of the hollow rotary shaft 1 is discharged from the cement milk axial discharge hole 6. Therefore, the discharged cement is discharged from the cement milk radial discharge hole 5 which is a horizontal hole formed in the hollow rotary shaft 1 into the excavated earth and sand excavated by the excavating blade 3. The milk 8 </ b> A and the excavated earth and sand are stirred by the stirring blade 2, and the soil cement layer 7 can be formed.

It is the whole soil cement pile formation apparatus front view. It is a principal part enlarged front view of the part enclosed by A of FIG. 1, and is a figure which shows the use condition by which the cement milk axial direction discharge hole was closed. It is the principal part expanded side view. It is an expansion perspective view of the principal part. (A) is a vertical side view of the main part. (B) is the BB sectional drawing of (a), and is a vertical front view of the principal part. It is a figure similar to FIG. 2, and is a figure which shows the use condition by which the cement milk axial direction discharge hole was opened. It is an expansion perspective view of the principal part. (A) is a vertical side view of the main part. (B) is CC sectional view taken on the line of (a), and is the longitudinal front view of the principal part. It is process explanatory drawing which shows the formation process of the soil cement pile which concerns on this invention which consists of (a)-(e). FIG. 10 is an operation explanatory view of a portion surrounded by X in the process diagram of FIG . FIG. 10 is an operation explanatory diagram of a portion surrounded by XI in the process diagram of FIG . It is explanatory drawing which shows the building in which a soil cement pile is generally formed.

That is, the stirring blades 2 and 2 projecting radially from the hollow rotating shaft 1 are provided at the lower end of the hollow rotating shaft 1, and the arm 3a projecting from the hollow rotating shaft 1 in the radial direction is attached to the lower side. An excavation blade 3 including an excavation bit 3 b is provided, and an excavation head 4 is attached to the lower end portion of the hollow rotary shaft 1. When the excavation head 4 penetrates into the ground G to form the excavation hole H, the excavation head 4 receives the earth pressure as will be described later and is in a position where it has slightly moved upward, thereby closing the cement milk axial discharge hole 6. It is in the state. At the lower end of the hollow rotary shaft 1, a cement milk radial discharge hole 5, which is a horizontal hole, is provided adjacent to the circumferential direction of the excavation blade 3 and the hollow rotary shaft 1 at the same axial height level. As a result, the cement milk 8A discharged from the cement milk radial discharge hole 5 is immediately discharged into the excavated soil excavated by the excavating blade 3, and is discharged from the cement milk radial discharge hole 5 into the excavated soil. is cement milk 8A is will be a cement milk 8A and drilling soil is stirred 攪拌翼2 is efficiently stirred mixture. (See Figure 10)

From this point of time, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 is a soil cement layer 7 formed by discharging the cement milk 8A from the cement milk radial discharge hole 5 of the hollow rotary shaft 1. The cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 with respect to the high discharge resistance with respect to the cement milk radial direction discharge hole 5 by means of the As the hollow rotary shaft 1 is pulled upward from the holes 6 and 6 , the cement milk layer 8 is formed upward in the center of the soil cement layer 7. .

If the means for achieving the above object is shown with reference numerals in the drawings, the method for forming a soil cement pile according to the invention described in claim 1 projects from the hollow rotary shaft 1 in a radial direction perpendicular thereto. A stirring blade 2 provided below, a drilling blade 3 provided below the stirring blade 2 and protruding in the radial direction, and a drilling head 4 provided protruding in the axial direction at the lower end of the hollow rotary shaft 1. While discharging the cement milk injected into the hollow rotary shaft 1, the hollow rotary shaft 1 is rotated to penetrate into the ground, and the soil cement pile in which the excavated sediment and cement milk are stirred around the hollow rotary shaft 1 A method for forming a soil cement pile in which the cement milk radial discharge hole 5 for discharging the cement milk 8A (FIG. 10) in the radial direction perpendicular to the hollow rotating shaft 1 is formed. Cement milk diameter A cement milk axial discharge hole 6 for discharging cement milk 8A (FIG. 11) downward from the lower end of the hollow rotary shaft 1 in the axial direction is provided below the direction discharge hole 5, and the hollow rotary shaft 1 is rotated. Then, while the hollow rotary shaft 1 is penetrated into the ground G and excavated, the cement milk 8A is discharged into the ground from the cement milk radial discharge hole 5 provided in the hollow rotary shaft 1 and excavated sediment around the hollow rotary shaft 1 And the cement milk 8A are stirred (FIGS. 9A, 9B, and 10). When the hollow rotary shaft 1 reaches a predetermined depth, the hollow rotary shaft 1 is moved upward. The cement milk 8A is discharged axially downward from the lower end portion of the hollow rotary shaft 1 through the cement milk axial discharge hole 6 provided at the lower end portion of the hollow rotary shaft 1 while being pulled up. Forming a reinforcement milk layer 8 (FIG. 9 (c), the FIG. 9 (d), the FIG. 11), then the core material 9 to cement milk layer 8 formed by inserting a (FIG. 9 (e)) of the soil cement pile In the forming method,
The excavation head 4 provided at the lower end of the hollow rotary shaft 1 is supported by an excavation head support shaft 10 provided through the lower end of the hollow rotary shaft 1 in the radial direction so as to be movable up and down. The cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is closed during movement, and the cement milk axial discharge hole 6 is opened when the excavation head 4 moves downward. .

The invention according to claim 5 is the method of forming the soil cement pile according to any one of claims 1 to 4 , wherein the vertical guide frame guides the vertical movement of the excavation head 4 to the lower end portion of the hollow rotary shaft 1. 11 is provided.

The invention according to claim 6 includes a stirring blade 2 provided projecting in a radial direction perpendicular to the hollow rotary shaft 1, a drilling blade 3 provided below the stirring blade 2 and projecting in the radial direction, The excavation head 4 is provided at the lower end of the hollow rotary shaft 1 so as to protrude in the axial direction, and the hollow rotary shaft 1 is rotated while the cement milk injected into the hollow rotary shaft 1 is discharged, thereby penetrating into the ground. A method for forming a soil cement pile in which the excavated soil and cement milk is stirred around the hollow rotary shaft 1, the cement being formed in the radial direction perpendicular to the hollow rotary shaft 1. Cement milk radial discharge hole 5 for discharging milk 8A (FIG. 10), and cement milk 8A (FIG. 10) below the cement milk radial discharge hole 5 and axially downward from the lower end of the hollow rotary shaft 1 11) A cement milk axial discharge hole 6 for discharging, and rotating the hollow rotary shaft 1 to penetrate the hollow rotary shaft 1 into the ground G and excavating the hollow rotary shaft 1, the cement milk radial discharge hole provided in the hollow rotary shaft 1 5, the cement milk 8A is discharged into the ground to form a soil cement layer 7 in which the excavated earth and sand and the cement milk 8A are agitated around the hollow rotary shaft 1 (FIG. 9 (a), FIG. 9 (b), FIG. 10) When the hollow rotary shaft 1 reaches a predetermined depth, the cement milk 8A of the hollow rotary shaft 1 is removed from the cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 while the hollow rotary shaft 1 is pulled upward. By discharging downward from the lower end in the axial direction, a cement milk layer 8 is formed at the center of the soil cement layer 7 (FIGS. 9C, 9D, and 11), and then the cement milk layer 8 Core material A method of forming a soil cement piles made by inserting (Fig. 9 (e)),
When excavating the underground with the hollow rotary shaft 1 penetrating into the ground, the excavation head 4 is moved up by the earth pressure of the excavated soil and discharged in the cement milk axial direction provided at the lower end of the hollow rotary shaft 1. The hole 6 is closed.

The invention according to claim 7 includes a stirring blade 2 provided on the hollow rotary shaft 1 so as to project in a radial direction perpendicular thereto, and a drilling blade 3 provided below the stirring blade 2 and projecting in the radial direction. The excavation head 4 is provided at the lower end of the hollow rotary shaft 1 so as to protrude in the axial direction, and the hollow rotary shaft 1 is rotated while the cement milk injected into the hollow rotary shaft 1 is discharged, thereby penetrating into the ground. A method for forming a soil cement pile in which the excavated soil and cement milk is stirred around the hollow rotary shaft 1, the cement being formed in the radial direction perpendicular to the hollow rotary shaft 1. Cement milk radial discharge hole 5 for discharging milk 8A (FIG. 10), and cement milk 8A (FIG. 10) below the cement milk radial discharge hole 5 and axially downward from the lower end of the hollow rotary shaft 1 11) A cement milk axial discharge hole 6 for discharging, and rotating the hollow rotary shaft 1 to penetrate the hollow rotary shaft 1 into the ground G and excavating the hollow rotary shaft 1, the cement milk radial discharge hole provided in the hollow rotary shaft 1 5, the cement milk 8A is discharged into the ground to form a soil cement layer 7 in which the excavated earth and sand and the cement milk 8A are agitated around the hollow rotary shaft 1 (FIG. 9 (a), FIG. 9 (b), FIG. 10) When the hollow rotary shaft 1 reaches a predetermined depth, the cement milk 8A of the hollow rotary shaft 1 is removed from the cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 while the hollow rotary shaft 1 is pulled upward. By discharging downward from the lower end in the axial direction, a cement milk layer 8 is formed at the center of the soil cement layer 7 (FIGS. 9C, 9D, and 11), and then the cement milk layer 8 Core material A method of forming a soil cement piles made by inserting (Fig. 9 (e)),
After the hollow rotary shaft 1 reaches a predetermined depth, when the hollow rotary shaft 1 is lifted upward, the excavation head 4 is moved down to the lower end of the hollow rotary shaft 1 by being released from the earth pressure of the excavated soil. The provided cement milk axial discharge hole 6 is configured to be opened.

The invention according to claim 8 is the method for forming a soil cement pile according to any one of claims 1 to 7 , wherein the stirring blade 2 attached to the hollow rotary shaft 1 so as to protrude in the radial direction is provided below the stirring blade 2. The stirring auxiliary blade 12 that protrudes in the radial direction longer than the radial protruding length of the agitating blade 2 and the excavating blade 3 is located between the upper and lower faces of the excavating blade 3 that is also provided protruding in the radial direction. 1 is configured such that the rotational force of the hollow rotary shaft 1 is not transmitted.

Next, the effects of the present invention will be specifically described with reference to the drawings. First, according to the method for forming a soil cement pile according to the first aspect of the present invention, the cement milk radial discharge hole 5 for discharging the cement milk 8A in the radial direction perpendicular to the hollow rotating shaft 1 and the cement milk A cement milk axial discharge hole 6 is provided below the radial discharge hole 5 for discharging cement milk 8A downward from the lower end of the hollow rotary shaft 1 in the axial direction. Cement milk 8A is discharged into the ground through a radial discharge hole 5 provided in the hollow rotary shaft 1 while the hollow rotary shaft 1 is penetrating into the ground G, and excavated sediment and cement milk are disposed around the hollow rotary shaft 1. 8A and a cement cement layer 7 is formed. When the hollow rotary shaft 1 reaches a predetermined depth, the cement provided at the lower end of the hollow rotary shaft 1 while pulling the hollow rotary shaft 1 upward. Cement milk 8A is discharged axially downward from the lower end portion of the hollow rotary shaft 1 through the milk discharge shaft 6 in the milk direction, thereby forming a cement milk layer 8 at the center of the soil cement layer 7, and then the cement milk layer 8 Since the core material 9 is inserted, the heavy rotational drive device 13 is connected to the upper end portion of the hollow rotary shaft 1 in all steps until the core material 9 is inserted into the cement milk layer 8 in the final process. The soil cement pile can be formed by this, and this can greatly reduce the process of forming the soil cement pile, thereby forming the soil cement pile efficiently and in a short time. Can do.
Further, according to the present invention, the excavation head 4 provided at the lower end portion of the hollow rotary shaft 1 is supported by the excavation head support shaft 10 provided through the lower end portion of the hollow rotary shaft 1 in the radial direction so as to be movable up and down. In addition, when the excavation head 4 moves upward, the cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is closed, and when the excavation head 4 moves downward, the cement milk axial discharge hole 6 is opened. Therefore, as the excavation head 4 moves up and down, the cement milk axial discharge hole 6 can be opened and closed smoothly, and the configuration thereof is also simple.

According to the fifth aspect of the present invention, the upper and lower guide frames 11 that guide the vertical movement of the excavation head 4 are provided at the lower end portion of the hollow rotary shaft 1. Even if 4 receives a large load such as cutting earth and sand and the load is applied to the excavation head support shaft 10, the load is received by the upper and lower guide frames 11, and the excavation head support shaft 10 is destroyed. Absent.

According to the invention of claim 6 , when excavating the underground with the hollow rotary shaft 1 penetrating into the ground, the excavation head 4 moves upward by the earth pressure of the excavated soil, and the hollow rotary shaft 1 Since the cement milk axial discharge hole 6 provided at the lower end is closed, the cement milk 8A pumped and injected into the hollow part 14 of the hollow rotary shaft 1 is discharged from the cement milk axial discharge hole 6. Therefore, the cement milk 8A discharged from the cement milk radial discharge hole 5 which is a horizontal hole formed in the hollow rotary shaft 1 is discharged into the excavated sediment by the excavating blade 3. And the excavated earth and sand are agitated by the agitating blade 2, and the soil cement layer 7 can be formed.

According to the seventh aspect of the present invention, when the hollow rotary shaft 1 is lifted upward after the hollow rotary shaft 1 reaches a predetermined depth, the excavation head 4 is moved downward by being released from the earth pressure of the excavated soil. Then, a cement milk axial discharge hole 6 provided at the lower end of the hollow rotary shaft 1 is opened, and a soil cement layer formed by discharging cement milk 8A from the cement milk radial discharge hole 5 of the hollow rotary shaft 1 7, the discharge resistance with respect to the cement milk radial discharge hole 5 is increased, and therefore, the cement milk 8A pumped and injected into the hollow portion 14 of the hollow rotary shaft 1 has a low discharge resistance in the cement milk axial discharge hole. 6 is discharged downward in the axial direction, and as the hollow rotary shaft 1 is pulled upward, the cement milk layer 8 is directed upward at the center of the soil cement layer 7. It can be formed.

According to the eighth aspect of the present invention, the agitating blade 2 attached to the hollow rotary shaft 1 so as to protrude in the radial direction and the excavation blade 3 provided below and in the same manner protruding in the radial direction are vertically opposed to each other. Thus, the auxiliary stirring blade 12 that protrudes in the radial direction longer than the protruding length in the radial direction of the stirring blade 2 and the excavating blade 3 is attached to the hollow rotary shaft 1 so that the rotational force of the hollow rotary shaft 1 is not transmitted. Therefore, the stirring auxiliary blade 12 does not transmit the rotational force of the hollow rotating shaft 1 to the stirring blade 2 that rotates integrally with the hollow rotating shaft 1 and exerts a stirring action, so that it is in an idle state. In addition, since the protruding amount in the radial direction of the auxiliary stirring blade 12 is larger than that of the stirring blade 2 and the excavating blade 3, the tip of the auxiliary stirring blade 12 is the hole of the excavation hole excavated by the excavating blade 3. I got into the wall a little bit, The stirring auxiliary blade 12 is in a fixed state, and the cement milk 8A between the stirring blade 2 and the stirring auxiliary blade 12 is caused by the synergistic action of the rotating stirring blade 2 and the stirring auxiliary blade 12 in the fixed state. The excavated earth and sand will be efficiently stirred and mixed. In other words, the auxiliary stirring blade 12 will assist the stirring action of the stirring blade 2, and a high-quality soil cement layer 7 can be formed.

Claims (9)

A stirring blade provided on the hollow rotating shaft in a radial direction orthogonal to the hollow shaft, a drilling blade provided below the stirring blade and projecting in the radial direction, and a lower end portion of the hollow rotating shaft protruding in the axial direction. The drilling head is provided, and while discharging the cement milk injected into the hollow rotary shaft, the hollow rotary shaft is rotated to penetrate into the ground, and the excavated soil and cement milk are placed around the hollow rotary shaft. A method of forming a soil cement pile that is configured to form a stirred soil cement pile,
A cement milk radial discharge hole for discharging cement milk in a radial direction perpendicular to the hollow rotary shaft, and a lower part of the hollow rotary shaft from the lower end of the hollow rotary shaft downward in the axial direction. Cement milk axial discharge holes for discharging cement milk are provided,
While rotating the hollow rotating shaft and penetrating and excavating the hollow rotating shaft into the ground, the cement milk is discharged into the ground from the cement milk radial discharge hole provided in the hollow rotating shaft, and the excavated soil and sand around the hollow rotating shaft Form a soil cement layer that is stirred with cement milk,
When the hollow rotating shaft reaches a predetermined depth, the cement milk is discharged from the lower end portion of the hollow rotating shaft downward in the axial direction through the cement milk axial discharge hole provided at the lower end portion of the hollow rotating shaft while pulling the hollow rotating shaft upward. By forming a cement milk layer in the center of the soil cement layer,
A method for forming a soil cement pile by subsequently inserting a core material into the cement milk layer.   The method for forming a soil cement pile according to claim 1, wherein when the hollow rotary shaft is pulled upward, the hollow rotary shaft is pulled up without rotating.   The method for forming a soil cement pile according to claim 1, wherein when the hollow rotary shaft is pulled upward, the hollow rotary shaft is pulled up while rotating forward or reverse.   The cement milk radial discharge hole provided in the hollow rotary shaft and the stirring blade provided in the radial direction on the hollow rotary shaft are provided at the same axial height level adjacent to the circumferential direction of the hollow rotary shaft. The method for forming a soil cement pile according to any one of claims 1 to 3.   The excavation head provided at the lower end of the hollow rotary shaft is supported by an excavation head support shaft provided through the lower end of the hollow rotary shaft in the radial direction so that the excavation head can move up and down. 5. The soil according to claim 1, wherein a cement milk axial discharge hole provided at a lower end of the cement is closed, and the cement milk axial discharge hole is opened when the excavation head moves downward. Cement pile formation method.   The method for forming a soil cement pile according to any one of claims 1 to 5, wherein an upper and lower guide frame for guiding the vertical movement of the excavation head is provided at a lower end portion of the hollow rotary shaft.   When excavating the underground with the hollow rotary shaft penetrating into the ground, the excavation head moves up due to the earth pressure of the excavated soil, and the cement milk axial discharge hole provided at the lower end of the hollow rotary shaft is blocked. The method for forming a soil cement pile according to any one of claims 1 to 6.   When the hollow rotary shaft is lifted upward after the hollow rotary shaft reaches a predetermined depth, the excavation head moves downward and the cement milk provided at the lower end of the hollow rotary shaft is released from the earth pressure of the excavated soil. The method for forming a soil cement pile according to any one of claims 1 to 7, wherein an axial discharge hole is opened.   A radial protrusion of the agitating blade and the excavating blade between the agitating blade attached to the hollow rotating shaft and projecting in the radial direction, and the excavating blade below the agitating blade that is also provided to project in the radial direction. The formation of a soil cement pile according to any one of claims 1 to 8, wherein a stirring auxiliary blade that is longer than the length and protrudes in the radial direction is attached to the hollow rotary shaft so that the rotational force of the hollow rotary shaft is not transmitted. Method.

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