JP2007247189A - Method of forming improved body, and screw shaft for use in the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an improved body which can directly bear an aboveground structure, based on settling reaction generated at a formed object, by earth pressure, in soft ground, and to provide a screw shaft for use in the method. <P>SOLUTION: According to the method of forming the improved body which is rigidly fixed in the soft ground, a hole 11 is excavated in the soft ground by the screw shaft 1 having a spiral blade 7 mounted on a peripheral surface thereof, and thereafter, the screw shaft 1 is rotated backward, followed by charging an improving agent into the hole 11. Then the improving agent is compressed downward by rotary blades 13 attached to a distal end of the screw shaft 1, by rotating the screw shaft 1 backward, and the improving agent and the ground around the hole are radially compressed by the rotating blade 13. Further the improving agent itself is rigidly hardened to a strength sufficient for directly supporting the structure, and formed into a solid body having projections formed on a peripheral surface thereof, that are projected into soft stratums of the ground, in the construction field, based on a dry method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming an improved body that is provided in an underground state and is capable of resisting subsidence with frictional force and support force generated by pressure in the soil, and a screw shaft used in the method, and more particularly. Relates to a method of forming an improved body capable of directly supporting a structure on the ground and a screw shaft used in the method.

  Conventionally, as a structure for supporting a structure on the ground, a structure is known in which a plurality of piles are driven into the ground such that the lower end reaches a support ground such as a rock and the structure is supported by the piles. In this configuration, there is a problem that it is necessary to drive the pile deeply into the supporting ground, and the construction cost becomes expensive.

Therefore, in the hole excavated in the soft ground by the screw shaft, the improved material mixed with cement and aggregates such as pile sand is introduced, and the improved material is compressed downward by rotating the screw shaft reversely, A method has been proposed in which the ground around the improvement material and the hole is compressed in the radial direction so that the entire ground is consolidated and the supporting force of the entire ground is increased (see, for example, Patent Document 1).
Japanese Patent No. 3469217

  As shown in FIG. 5, the configuration of the screw shaft 1 described in Patent Document 1 includes a spiral blade 7 on the outer peripheral surface of the rotating shaft 5 having a tapered portion 3 at the lower end portion, and the tapered portion 3. It is the structure provided with the rotary blade 9 for compressing the improved material thrown into the hole excavated at the time of reverse rotation of the screw shaft 1 in the radial direction on the outer peripheral surface.

  After excavating a hole in the soft ground with the screw shaft 1, when the screw shaft 1 is rotated in the reverse direction and the improvement material is introduced into the hole, the improvement material is compressed downward by the spiral blade 7. Further, the improvement material is compressed in the radial direction by the action of the rotary blade 9, and the soft ground around the hole is compressed, so that the soft ground is consolidated and improved.

  By the way, when the space (gap) between the rotor blades 9 enters the state in which the improving material is filled, the improving material in the space is attached to the rotating shaft 5 and integrated with the rotating shaft 5. The soft ground around the improvement material and the hole may not be sufficiently compressed in the radial direction, and further improvement is required.

  Moreover, although the said improvement material contains cement and mountain sand, the said cement is a grade which absorbs the surrounding water | moisture content and hardens | cures, and there is little content of cement. Therefore, since the improvement material (block member) compressed and solidified in the hole has a small amount of cement and is not solidified firmly, only the block member itself supports the structure on the ground directly. It does not have strength. Therefore, in order to improve the entire ground supporting the structure, it is necessary to sufficiently compress the ground around the block member, and there are relatively many holes to be excavated to improve the entire ground. There is a problem of becoming.

  The present invention has been made in view of the problems as described above, and is a method of forming an improved body that can resist subsidence with frictional force and supporting force generated by pressure in the soil in soft ground, After excavating a hole in the soft ground with a screw shaft provided with a spiral blade on the surface, the screw shaft is reversely rotated, and an improvement material is introduced into the hole, and the tip of the screw shaft is rotated by reverse rotation of the screw shaft The improvement material can be compressed downward by the rotary blade provided in the case, the ground around the improvement material and the hole can be compressed radially by the rotary blade, and the improvement material itself can directly support the structure. It is characterized in that it is solidified with a sufficient strength and is formed into a solid having a convex portion in a state where it enters the soft layer of the ground.

  Further, the screw shaft for excavating a hole in the soft ground, provided with a spiral blade on the outer peripheral surface of the rotary shaft, and the reverse rotation of the rotary shaft on the outer peripheral surface of the tapered portion provided at the tip of the rotary shaft It is characterized in that it is equipped with a rotary blade for compressing the improved material sometimes introduced into the hole in the downward direction and the radial direction.

  In the screw shaft, a plurality of the rotor blades are provided, and each rotor blade is provided at a position where the phase of the screw shaft in the rotational direction is different and a position where the screw shaft is different in the axial direction. It is a feature.

  Further, in the screw shaft, the rotary blade includes a radial component force imparting portion for imparting radial compression to the improvement material in the hole when the screw shaft rotates in the reverse direction. It is characterized by having a lower component applying portion for applying downward compression to the improved material in the hole during reverse rotation.

  According to the present invention, the improved body is formed in a pile shape having uneven portions protruding in the radial direction due to the softness (strength) of the ground layer around the hole excavated in the soft ground, and having different protrusions in the periphery, and Even when the structure is directly supported, it is formed into a solid solidified with strength that does not collapse. Therefore, the reaction force when the ground on the peripheral surface of the hole is compressed in the radial direction acts on the peripheral surface of the improved body, for example, the frictional force that acts on the peripheral surface of the improved body to be submerged increases. . Moreover, since the outer peripheral surface of an improved body becomes a structure provided with the uneven | corrugated | grooved part, the said convex part and a lower surface become a mode supported from the bottom by the ground.

  Therefore, the improved body is difficult to sink against the ground, and the structure can be directly supported by the improved body itself.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components that have the same functions as those of the conventional configuration described above are denoted by the same reference numerals, and redundant description is omitted.

  1 to 3, a screw shaft 1 according to this embodiment is formed on the outer peripheral surface of a rotating shaft 5 having a tapered portion 3 at a lower end portion (tip portion), similarly to the conventional screw shaft described above. A spiral blade 7 is provided. The spiral blade 7 is provided on the rotary shaft 5 above the tapered portion 3. In other words, the spiral blade 7 is not provided in the tapered portion 3.

  Then, as in the conventional case, after excavating the hole 11 in the soft ground with the screw shaft 1, when the screw shaft 1 is reversely rotated and the improvement material is introduced into the hole 11, the improvement material in the hole 11 is lowered. The taper portion 3 is provided with a plurality of rotor blades 13 for compressing the improvement material in the radial direction (radial direction) and compressing the periphery of the hole 11 in the radial direction. The plurality of rotary blades 13 are at positions where the phase in the rotational direction of the rotary shaft 5 is greatly different (position where the interval between the rotary blades 13 is large) and at different positions in the axial direction (longitudinal and vertical directions) of the rotary shaft 5. Is provided.

  The rotary blade 13 functions (acts) as a drilling blade when the screw shaft 1 is rotated forward to excavate the hole 11. When the screw shaft 1 rotates in the reverse direction, the improvement material in the hole 11 is compressed downward, and the periphery of the improvement material and the hole 11 is compressed in the radial direction.

  That is, a radial component force (pressure) for applying a radial pressure (component force) in order to compress the improvement material (not shown) in the hole 11 in the radial direction during the reverse rotation of the rotary shaft 5. ) Providing unit 15 (see FIG. 3). In other words, the component force (pressure) applying portion 15 is inclined with respect to the radial direction (radial direction) of the rotary shaft 5 in order to press the improving material in the hole 11 in the radial direction when the screw shaft 1 rotates backward. It is.

  Further, at the upper and lower portions of the rotary blade 13, when the rotary shaft 5 rotates in the reverse direction, a downward component force applying portion 17 (for applying a downward pressure to the improving material in the hole 11 and compressing it downward) 2). More specifically, the lower component force applying portion 17 is inclined such that the upper end side precedes the lower end side of the rotary blade 13 in the reverse rotation direction when the rotating shaft 5 rotates in the reverse direction. And the height position (position of the axial direction of the screw shaft 5) of the said downward component force provision part 17 of each rotary blade 13 is different, respectively.

  In the above configuration, as in the prior art, after the hole 11 is excavated in the soft ground by the screw shaft 1, the screw shaft 1 is rotated in the reverse direction, and the improvement material is introduced into the hole 11. At this time, as an improvement material, the improvement material itself is more solid than the cement as an example of the solidifying agent in the improvement material that has been generally used so that the improvement material itself is solidified to a strength that can directly support the structure. An improvement material containing a large amount (for example, twice or more) of a solidifying agent is used.

  As described above, when the improvement material containing a large amount of a solidifying agent such as cement is thrown into the hole 11 while rotating the rotary shaft 5 in the reverse direction, the improvement material in the hole 11 corresponds to the rotational direction of each rotary blade 13. While being compressed in the radial direction by the force applying unit 15, it is compressed downward by the downward component applying unit 17. At this time, since the height positions of the respective lower component applying portions 17 provided in the respective rotary blades 13 are different, the improvement material in the hole 11 is compressed downward stepwise over a plurality of times. .

  That is, the improvement material in the hole 11 is sequentially compressed downward by the lower component applying portion 17 of each rotary blade 13 having a different height position. The upper layer portion immediately after the lower component applying force 17 on the lower side of the lowermost rotor blade 13 compresses the improved material is the lower part of the upper rotor blade 13 due to the reverse rotation of the screw shaft 1. Immediate compression by the side lower component applying portion 17 is repeated.

  When the upward reaction force acting on the lower component applying portion 17 becomes larger than the weight of the screw shaft 1, the screw shaft 1 gradually rises. That is, the improved material is compressed due to the large weight of the screw shaft 1. At this time, since the weight of the screw shaft 1 is greatly applied to the lower component applying portion 17 in the lowermost rotor blade 13, the improving material in the hole 11 is strongly compressed.

  As described above, when the screw shaft 1 is rotated in the reverse direction to compress the improvement material in the hole 11 in the downward direction and in the radially outward direction, the interval between the rotation directions of the rotary blades 13 is large and the position in the vertical direction. Therefore, the improvement material is not filled between the rotary blades 13 and does not rotate integrally. The ground around the hole 11 is also compressed simultaneously with the radial compression of the improved material, and the improved material is compressed until the reaction force from the ground becomes substantially constant. Therefore, when there is a soft formation on the ground, the improving material enters the soft formation.

  Therefore, although the improvement body 19 formed by compressing into the hole 11 is formed in a columnar shape along the hole 11, the outer peripheral surface of the improvement body 19 enters a soft formation and protrudes in an appropriate shape. A portion (convex portion) 21 is provided. That is, the peripheral surface of the improved body 19 has a form with large uneven portions. The improved body 19 is solidified with high strength and solidity, such as concrete which does not collapse even when the improved body 19 itself supports a structure such as a foundation directly. is there. That is, the improved body 19 is a columnar shape having large uneven portions on the peripheral surface, and is formed as an integrated fixed body (solidified body) having a large overall strength.

  As described above, in the hole 11 excavated in the soft ground, in a state where an improved material containing a large amount of a solidifying agent is introduced and compressed, the strength of the concrete does not collapse even if the structure is directly supported. In a state where the improvement material is solidified in a large and extremely strong manner, when the improvement material is compressed, the ground around the hole 11 is also compressed, so that the ground is also improved. Then, when the improved body 19 is formed by solidifying the improved material to a strength capable of directly supporting the structure, a reaction force when the ground is compressed acts on the peripheral surface of the improved body 19. Therefore, when the improved body 19 tries to sink, a large frictional resistance is generated. Further, since the protruding portion 21 that has entered the soft layer of the ground is integrally formed on the peripheral surface of the improved body 19, the supporting force of the ground acts on the lower surface of the improved body 19 and the protruding portion 21. Is. That is, a large supporting force acts on the improved body 19.

  Therefore, even when the structure (for example, the foundation) is directly supported by the improved body 19, the improved body 19 does not sink. That is, even in the soft ground, the structure can be directly supported without performing ground improvement although the consolidation of the whole soft ground is performed. Moreover, a structure can be reliably supported, without requiring a strong support ground in the underground deep part like a pile.

  As will be understood from the above description, the rotor blade 13 functions as an excavating blade when the screw shaft 1 rotates forward, and when the screw shaft 1 rotates backward, the improvement material in the hole 11 is moved downward and radially. It has a function of compressing the image. Therefore, the configuration of the screw shaft 1 becomes simpler than the configuration in which the configuration for compressing the improving material in the downward direction and the configuration for compressing in the radial direction are performed by separate components.

  Further, the plurality of rotor blades 13 are provided such that the phase is shifted in the rotation direction of the screw shaft 1 and the positions thereof are shifted in the axial direction, so that the improvement material is not clogged between the rotor blades 13. The improved material can be compressed stepwise (for example, in two stages), and the downward compression of the improved material can be performed more firmly.

  The improved body 19 has a large strength and is solidified extremely like concrete, and acts on the bottom surface of the improved body 19 due to a large frictional force generated on the peripheral surface of the improved body 19 using the pressure in the soil. It is intended to prevent the structure of the ground from sinking due to the supporting force. Therefore, it is not necessary to dig a hole deeply as in the conventional configuration for driving a pile, and it is not necessary to consolidate the entire supporting ground, so that inexpensive construction can be performed. In addition, the structure can be reliably supported.

It is explanatory drawing which showed notionally and schematically the structure of the screw shaft which concerns on embodiment of this invention. It is side surface explanatory drawing of the screw shaft which concerns on embodiment of this invention. It is bottom face explanatory drawing of the screw shaft which concerns on embodiment of this invention. It is explanatory drawing which shows the structure of an improved body. It is explanatory drawing which shows the structure of the conventional screw shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 3 Tapered part 5 Rotating shaft 7 Spiral blade 11 Hole 13 Rotary blade 15 Rotation direction component (pressure) provision part 17 Lower component force provision part 19 Improved body (concrete)
21 Protrusion

Claims (4)

  A method of forming an improved body in soft ground that can resist subsidence with frictional force and support force caused by pressure in the soil, and drilling a hole in the soft ground with a screw shaft with spiral blades on the outer peripheral surface Then, the screw shaft is rotated in the reverse direction, the improvement material is put into the hole, and the improvement material is compressed downward by the rotating blade provided at the tip of the screw shaft by the reverse rotation of the screw shaft. The rotary blades compressed the improvement material and the ground around the hole in the radial direction, and the improvement material itself was firmly solidified to a strength capable of directly supporting the structure, and entered the soft layer of the ground. A method for forming an improved body, characterized in that a convex portion in a state is formed into a solid having a peripheral surface.   A screw shaft for excavating a hole in soft ground, provided with a spiral blade on the outer peripheral surface of the rotating shaft, and on the outer peripheral surface of the tapered portion provided at the tip of the rotating shaft, when the rotating shaft rotates in the reverse direction A screw shaft comprising a rotating blade for compressing an improved material put into a hole in a downward direction and a radial direction.   3. The screw shaft according to claim 2, wherein a plurality of the rotor blades are provided, and each rotor blade is provided at a position where a phase in a rotation direction of the screw shaft is different and a position which is different in an axial direction of the screw shaft. A screw shaft characterized by that.   4. The screw shaft according to claim 2, wherein the rotor blade includes a radial component force imparting portion for imparting radial compression to the improvement material in the hole when the screw shaft rotates in the reverse direction. 5. A screw shaft comprising a lower component applying portion for applying downward compression to the improved material in the hole during reverse rotation of the screw shaft.

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