JP5069817B2 - Ground improvement method and ground improvement device - Google Patents

Description

  The present invention relates to a ground improvement method. Specifically, the present invention relates to a method of improving the ground by providing a columnar body on the ground.

  When building houses on soft ground, one way to strengthen the ground is to drill the ground to form vertical holes, and mix the excavated soil and ground solidification material (cement milk). There is a ground improvement method that creates columnar bodies in the vertical holes to increase the support capacity of the ground. This construction method is performed by, for example, the ground improvement device 100 shown in FIG. First, the rotating shaft 101 provided so as to be able to rotate up and down penetrates the ground while rotating, and the ground is excavated by the excavating member 102 at the tip thereof (see FIGS. 5B and 5C). After excavation to a predetermined depth, the ground solidified material is discharged from a discharge port 105 provided at the tip of the rotating shaft 101 and the rotating shaft 101 is pulled up while rotating. As a result, the excavating member 102 and the stirring blades 103 and 104 projecting laterally on the rotating shaft 101 rotate to mix and stir the excavated soil and the ground solidification material. At this time, the co-rotation preventing member 106 prevents the excavated soil and the ground solidification material from co-rotating with the excavating member 102 and the stirring blades 103 and 104, thereby increasing the mixing and stirring action. In this way, columnar bodies are created in the ground to improve the ground.

JP-A-8-13473

In the ground improvement device 100, the tip of the excavation member 102 (tip of the rotating shaft) protrudes in a conical shape, for example. When the concrete body 90 such as the bottom plate of the retaining wall or the underground garage exists under the soft ground that forms the columnar body, the excavation member 102 may contact the concrete body and damage the concrete body 90. If it is going to prevent this, the soft ground near the concrete body 90 cannot fully be excavated. Therefore, residual soil (a part of the soft ground that has not been excavated) 91 remains between the lower surface of the vertical hole and the concrete body 90, and the tip of the vertical hole has a shape protruding in a substantially conical shape. As a result, the lower end of the columnar body formed in the vertical hole has a shape protruding in a substantially conical shape. It demonstrates in detail using the schematic diagram of the lower end vicinity of the columnar body 900 shown in FIG. As shown in FIG. 6, the lower end of the columnar body 900 to be formed has a shape in which a tip portion 901 protrudes in a substantially conical shape. As a result, the load on the columnar body 900 is concentrated on the tip 901 at the lower end. If the load is excessively concentrated on the tip portion 901, the tip portion 901 is damaged, and the supporting force of the columnar body 900 is significantly reduced. In addition, the soft ground in the vicinity of the concrete body 90 cannot be excavated sufficiently, and if the lower end of the columnar body 900 does not reach the concrete body 90, it may sink due to a load.
On the other hand, when there is a ground that is so hard that excavation is difficult under the soft ground, when the tip of the excavating member 102 reaches the ground that is so hard that excavation is difficult (hard ground), the excavating member 102 excavates the hard ground. Since it is pushed back by receiving a strong repulsive force, the soft ground near the hard ground cannot be excavated sufficiently, and a residual soil remains between the lower surface of the vertical hole and the hard ground. Further, the excavated soil and the ground solidification material cannot be sufficiently stirred in the vicinity of the hard ground, and the vicinity of the discharge port is positively solidified. As a result, even in such a case, the tip of the columnar body to be formed tends to have a substantially conical protruding shape, resulting in the same result as in the above case.
Then, this invention makes it one subject to provide the ground improvement method which produces the columnar body by which the fall of a supporting force is prevented. Another object of the present invention is to provide a ground improvement method for preventing damage to concrete bodies such as bottom plates of retaining walls and underground garages.

The present invention has been made to solve at least one of the above problems, and has the following configuration. That is,
A ground improvement method for forming a columnar body in the ground,
Excavating the ground to form a vertical hole of a predetermined depth;
Agitating and mixing the ground excavation soil and solidified material in the vertical hole to form a mixture;
Inserting a flattening member into the vertical hole before the mixture solidifies to mix the residual soil at the bottom of the vertical hole, and flattening the bottom of the vertical hole;
Solidifying the mixture in the vertical hole to form a columnar body;
It is a ground improvement method including

  According to such a ground improvement method, since the tip (lower end) of the vertical hole is flattened, the lower surface of the columnar body formed here is a flat surface. Thereby, the load concerning a columnar body does not concentrate on a part of lower end, but the damage of a columnar body and the fall of the supporting force accompanying this are prevented.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a flowchart representing the outline of the ground improvement method 1 of the present invention. As shown in FIG. 1, the ground improvement method 1 generally includes first excavating the ground to form a vertical hole having a predetermined depth (first step a). Thereafter, the ground excavated soil and the solidified material are stirred and mixed in the vertical hole to form a mixture (second step b). Next, before the mixture is solidified, a flattening member is inserted into the vertical hole to mix the remaining soil at the bottom of the vertical hole, and the bottom of the vertical hole is flattened (third step c). Then, the mixture is solidified in the vertical hole to form a columnar body (fourth step d).

  The ground improvement method 1 uses a ground improvement device including an excavating and stirring device 200 and a flattening device 300. FIG. 2 shows a side view of the excavating and stirring device 200. As shown in FIG. 2, the excavation and agitation device 200 includes an operation unit 2, a guide 3 connected to the operation unit 2, and a rotating shaft 4 standing along the guide 3. An excavating member 5 is attached to the lower end of the rotating shaft 4. Further, stirring members 6 and 7 and a co-rotation preventing member 8 are provided below the rotating shaft 4. A discharge port 9 is formed near the tip of the rotating shaft 4. The discharge port 31 discharges the cement milk supplied from the mixer 10. Further, the excavating and agitating device 200 is connected to the mixer 10 via the pipe 11, and a ground solidifying material (cement milk) is supplied from the mixer 10.

Next, the schematic diagram which shows the ground improvement method 1 is shown to Fig.3 (a)-(f), and each step is demonstrated in detail, referring these. As shown in FIG. 3A, a heel plate (bottom plate) 13 having an L-shaped retaining wall exists under the soft ground 12. First, the excavating and stirring device 200 is installed at a predetermined position, and the rotating shaft 4 is rotated and lowered (see FIG. 3A). Along with this, the excavating member 5 rotates and is pressed against the ground and penetrates into the ground while excavating the ground, and excavates just before the heel plate 13 to form a vertical hole 15 (see FIG. 3B). ). Then, after the cement shaft is discharged from the discharge port 9, the rotating shaft 4 is repeatedly rotated up and down a few times and then pulled up from the soft ground 12 (see FIG. 3C). As a result, a mixture of cement milk and excavated soil is formed in the vertical hole 15. In this state, residual soil 17 remaining without being excavated exists between the lower surface 16 of the vertical hole 15 and the upper surface of the heel plate 13 below the vertical hole 15.
Then, the planarization apparatus 300 is prepared (refer FIG.3 (d)). The flattening device 300 includes a rotating shaft 301 and a flattening member 303 pivotally supported by a fixed shaft 304 at the lower end thereof. The flattening member 303 includes a rod-like base portion 305 that is pivotally supported by the fixed shaft 304 and a flat plate portion 306 that protrudes from the lower edge of the base portion 305 in the excavation direction. The base portion 305 is made of metal, and the flat plate portion 306 is made of elastomer. The flat plate portion 306 includes two flat plates, and has the same width as that of the excavating member 5 of the excavating and agitating device 200 in a state where the two flat plates are arranged side by side.
Next, the rotation shaft 301 is rotated and lowered to insert the flattening member 303 into the vertical hole 15, and the rotation shaft 301 is rotated and lowered until the flat plate portion 306 of the flattening member 303 contacts the lower surface 16. The rotating shaft 301 is further rotated while the flat plate portion 306 of the flattening member 303 is in contact with the lower surface 16. As a result, the flat plate portion 306 is rubbed against the lower surface 16 to excavate the remaining soil 17 and is mixed and stirred with the mixture in the vertical hole 15. As a result, the remaining soil 17 becomes a part of the mixture (that is, mixed), and the lower surface 16 is flattened as indicated by reference numeral 18 (see FIG. 3E). Here, since the flat plate portion 306 is made of an elastomer, the heel plate 13 of the L-shaped retaining wall located directly below the lower surface 16 is not damaged. Thereafter, the rotating shaft 301 is slowly raised to pull up the flattening device 300 from the ground (see FIG. 3 (f)). Then, the mixture in the vertical hole 15 is allowed to stand for a predetermined time to solidify the columnar body 19 in the soft ground 12.

  As described above, according to the ground improvement method 1 using the ground improvement device composed of the excavating and agitating device 200 and the flattening device 300, the flat soil slab 17 is mixed by rubbing the flat plate portion 306 of the flattening member 303 against the lower surface 16. By flattening the lower surface 16, the lower surface 20 of the columnar body 19 is made substantially planar. Since the lower surface 20 of the columnar body 19 is substantially planar in this way, when a structure is placed on the upper portion of the columnar body 19, the load is not concentrated on a part of the lower surface 20 of the columnar body 19. As a result, the columnar body 19 is prevented from being broken and the supporting force is lowered. Further, since the columnar body 19 is formed immediately above the heel plate 13 of the L-shaped retaining wall, settlement due to a load is also prevented. The flattening member 303 is supported by a fixed shaft 304. As a result, when the lower surface 16 is flattened, the flattening member 303 rotates around the fixed shaft 304 in accordance with the reaction force from the lower surface 16. Therefore, the flat plate 306 and the lower surface 16 are not concentrated on a part of the lower surface 16, and the lower surface 16 is flattened satisfactorily. .

  In the flattening device 300 used in the ground improvement method 1, the flattening member 303 is attached to the base 305 to form the flattening member 303. However, the configuration of the flattening member is not limited to this. As a material of the flattening member, a known material having flexibility can be adopted, and examples thereof include a flexible elastomer and plastic. Moreover, what shape | molded the metal material in the shape of a leaf | plate spring and a coil spring can also be utilized. Even if it is a metal material, if it is such a shape, since it exhibits high flexibility (elasticity), damage to concrete bodies, such as a bottom slab of a retaining wall and an underground garage, can be prevented. In addition, by making the shape of the flattening member into a chain shape or a wire shape, various metal materials, fiber materials, and the like can be employed as the material of the flattening member without being limited to the above materials. The planarizing member may be formed by combining the above materials. For example, the planarizing member may be formed from a composite in which a metal wire is included in the elastomer. If it does in this way, it can be set as the planarization member which has the flexibility by an elastomer, and the rigidity by metal wires.

  Other forms of the flattening member 303 are shown in FIGS. Note that members that are substantially the same as the configuration of the planarization apparatus 300 are denoted by the same reference numerals, and description thereof is omitted. 4A, the flattening member 303a includes a base 305, an elastomeric intermediate portion 306a, and a steel plate 307a attached to the lower end of the intermediate portion 306a. In another form shown in FIG. 4B, the flattening member 303b has a pair of left and right base parts 305 and three metal parts provided on each base part 205 so as to project in the excavation direction at a predetermined interval. Wire 306b. In the other form shown in FIG. 4C, the flattening member 303c has a pair of left and right bases 305 and three metal parts provided on each base 305 so as to protrude in the excavation direction at a predetermined interval. Wire 306c and a square steel plate 307c provided on the lower end of each wire 306c in plan view. In another form shown in FIG. 4D, the flattening member 303d has a pair of left and right base parts 305 and three metal parts provided on each base part 305 so as to protrude in the excavation direction at a predetermined interval. Wire 306d and a single steel lower end 307d attached to the lower ends of three metal wires 306d. The flattening members 303a to 303d described above also have the same effect as the flattening device 300.

  The present invention is not limited to the description of the embodiments of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

FIG. 1 is a flowchart of a ground improvement method 1 according to an embodiment of the present invention. FIG. 2 is a side view of the ground improvement device 100. 3A to 3F are schematic views of the ground improvement method 1. FIG. 4A to 4D are diagrams showing examples of other forms of the flattening apparatus. FIG. 5 is a schematic diagram showing how the conventional ground improvement device 100 is used. FIG. 6 is a schematic view of the vicinity of the lower end of the columnar body 900 created by the conventional ground improvement device 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground improvement method 100 Ground improvement apparatus 4 Rotating shaft 5 Excavation member 6, 7 Stirring member 8 Co-rotation prevention member 9 Discharge port 90 Concrete body 13 Heel plate 15 Vertical hole 17 Residual soil 19 Columnar body 200 Excavation stirring apparatus 300 Flattening apparatus 301 Rotation Shaft 303 Flattening member 304 Fixed shaft 305 Base 306 Flat plate

Claims (5)

A ground improvement method for forming a columnar body in the ground,
Excavating the ground to form a vertical hole of a predetermined depth;
Agitating and mixing the ground excavation soil and solidified material in the vertical hole to form a mixture;
Inserting a flattening member into the vertical hole before the mixture solidifies to mix the residual soil at the bottom of the vertical hole, and flattening the bottom of the vertical hole;
Solidifying the mixture in the vertical hole to form a columnar body;
Including ground improvement methods.   The ground improvement method according to claim 1, wherein the vertical hole is formed on a retaining wall embedded in the ground or on a hard ground.   A ground improvement device comprising a rotating shaft and a flattening member made of a flexible member provided at the tip of the rotating shaft is inserted into the vertical hole, and the flattening member is in contact with the lower surface of the vertical hole 3. The ground improvement according to claim 1, wherein the flattening member rotates together with the rotating shaft to mix the remaining soil at the bottom of the vertical hole and flatten the bottom of the vertical hole. Method. A rotation axis;
A flattening member made of a flexible material provided at the tip of the rotating shaft,
Inserted into a vertical hole formed in the ground, the flattening member is in contact with the bottom surface of the vertical hole, the flattening member rotates with the rotating shaft to mix the residual soil at the bottom of the vertical hole, A ground improvement device for flattening the lower surface of the vertical hole.   The ground improvement device according to claim 4, wherein the flexible material is made of an elastomer, a plastic, or a metal wire.

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