JP6661456B2 - Drilling agitation head for steel pipe soil cement pile construction - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a drilling and stirring head for construction of a steel pipe soil cement pile used when constructing a steel pipe soil cement pile composed of a soil cement column and a steel pipe.

  Steel pipe soil cement piles have excellent earthquake resistance and are mainly used as pile foundations for bridge piers and abutments of road and railway viaducts. A steel pipe soil cement pile has a structure in which steel pipes are concentrically arranged in a soil cement column.

  The vertical bearing capacity of a steel pipe soil cement pile is composed of the peripheral frictional resistance at the boundary between soil cement and the ground and the tip resistance of the tip of the soil cement. Therefore, in order to exhibit good bearing capacity, construction of high quality soil cement is indispensable.

  In order to build a high quality soil cement, it is necessary to stir and mix the excavated earth and sand and the cement milk uniformly, and a drilling and stirring device using co-rotating wings is used (for example, Patent Documents 1 and 2). reference).

In recent years, there has been a tendency for road bridge plans to shift from plains to mountainous areas. The supporting ground in the plain area has a lot of sand and gravel, but the supporting ground in the mountainous area has a lot of hard ground such as a large gravel layer and rock. Furthermore, the support layers in the mountainous areas are in most cases inclined.
In the case where the support layer is inclined, it is necessary to insert the pile into the hard ground for a long time in the design in order to ensure that all the tips of the piles reach the support layer.

  In a conventional excavation and stirring device with anti-corotating wings used for steel pipe soil cement piles, it is difficult to excavate hard ground due to the resistance of a protruding portion inserted into the outer ground.

  For this reason, when it is necessary to insert the steel into the hard support layer, the steel pipe soil cement pile is constructed separately after the hard ground has been subjected to primary treatment in advance to a hardness that allows excavation by the following method. Was.

(1) Rock auger method Using a base machine such as a three-point pile driver or a hydraulic crane, excavation is performed using a two-axis coaxial earth auger while reversing the screw and casing, and the hard ground is loosened.

(2) Casing rotary excavation method The hard ground in the casing tube is removed with a hammer rub while rotating and press-fitting the casing tube with a full-rotating excavator, and replaced with sand or the like.

  Further, Patent Document 3 discloses an anti-corotating wing used at the time of building a soil cement column. An overhang formed at the end of the anti-corotating wing body at a tip end of the anti-corotating wing body and made of a material having high strength. An anti-corotating wing composed of an anti-rotating wing is disclosed.

Japanese Patent No. 3621971 Japanese Patent No. 3904373 JP 2014-122495 A

  In the conventional construction of steel pipe soil cement piles, when it is necessary to burrow into hard ground, as described above, separate heavy equipment is required, and the construction period and cost associated with import / export / assembly disassembly and construction were large. . In addition, there are also problems of vibration noise, environmental problems such as the necessity of replacement sand and generation of residual soil.

  The present invention, in the construction of steel pipe soil cement piles for hard ground, separately, without the need for heavy equipment, it is possible to shorten the construction period, reduce cost due to the reduction of heavy equipment, reduce residual soil, reduce vibration and noise, high quality It is an object of the present invention to provide a drilling / mixing head capable of constructing soil cement.

  The present invention relates to a steel pipe soil which is connected to a drilling rod, discharges cement milk from a tip portion, mixes and mixes with the ground to build a soil cement column, and is used for embedding a steel pipe in the soil cement column to be built. The present invention relates to improvement of a drilling and stirring head for cement pile construction, and is particularly applicable to hard ground.

  As the configuration of the excavation stirring head, a shaft portion connected to the excavation rod, a lower excavation wing provided at the tip of the shaft portion and having a smaller diameter at the time of rotation, and a diameter at the time of rotation provided above the lower excavation wing are provided. It comprises a pair of upper excavating wings corresponding to the excavating diameter, a plurality of co-rotation preventing wings which are loosely fitted to the shaft portion and are longer than the upper excavating wings, and a plurality of stirring blades.

  In the present invention, by providing three or more lower excavating wings around the axis of the shaft portion, the excavation performance on hard ground is improved, and the displacement from the excavation axis during excavation is smaller than that of the conventional two-bladed wing. Is obtained.

  A larger number of lower excavation wings is more effective in suppressing run-out from the excavation axis, but if it is too large, it hinders the upward movement of the earth and sand shaved by the lower excavation wings, resulting in poor excavation Therefore, the number of lower excavation wings is preferably about 3 to 4.

  In order to improve the excavation performance, it is necessary to further increase the shaft diameter of the excavating rod and the excavating and stirring head and use a high-power auger motor, in which case the number of lower excavating blades is three or more. This enables stable construction.

  Further, with respect to the excavation bits attached to the lower excavation wing and the upper excavation wing, the use of a high-strength excavating bit makes it possible to smoothly excavate on hard ground such as soft rock. In addition, the tip of the shaft portion of the excavating and stirring head has a downward conical shape, and the excavating bit is attached to that portion, so that the excavation becomes smoother.

  Further, in the present invention, in addition to the above-described configuration, the co-rotation prevention wing is configured by a co-rotation prevention wing main body and an overhang portion attached to an end thereof. The overhang portion has a length such that a part or the whole thereof is inserted into the ground outside the hole wall surface of the excavation hole to be excavated by the upper excavation blade, is formed thinner than the anti-corotation wing body, and It is formed of a material having a higher strength than the material of the main body.

By increasing the strength of the overhanging portion of the co-rotation prevention wing and making it thinner, it is possible to reduce ground excavation resistance generated at the overhanging portion, and the effect is particularly large in hard ground.
The hard ground targeted in the present invention is assumed to be about soft rock, which was difficult to excavate with a conventional excavation and stirring head for steel pipe soil cement pile construction.

  In the steel pipe soil cement pile construction, a drilling and stirring head is attached to the tip of the drilling rod, drilling, discharge of cement milk from the drilling and stirring head tip, stirring and mixing with drilling earth and sand, and after raising the drilling rod, Simultaneous burial method in which a steel pipe is buried after the steel pipe is laid, and in which the drilling rod is passed through the steel pipe, excavation, discharge of cement milk from the tip of the drilling / mixing head, and mixing with the excavated earth and sand are performed. There is.

  In the case of the simultaneous burial method, a drilling / mixing head with a structure in which the upper drilling wing, anti-corotating wing, and stirring blade are foldable is conventionally used. After the installation and the installation of the steel pipe are completed, these wings are folded and the drilling rod is raised.

  Regarding the length of the lower excavation wing, it is desirable that the diameter during rotation is 0.4 to 0.7 times the excavation diameter of the upper excavation wing. Depending on the distance from the tip of the excavation and stirring head and the distance from the upper excavation wing, when excavating hard ground, first excavate by cutting the tip of the excavation and stirring head and the lower excavation wing into the ground. By excavating to the required excavation diameter, stable excavation becomes possible.

  If the diameter of the lower excavator blade during rotation exceeds 0.7 times the excavation diameter of the upper excavator blade, the load applied to the lower excavator blade becomes excessively large, and the excavation performance decreases. When the ratio is less than 0.4 times, the effect of suppressing the shaft runout increases, but the load on the upper excavation wing becomes too large, and the excavation performance decreases.

  As the material of the overhang portion of the co-rotation prevention blade, an ultra-high strength steel such as a spring steel material (SUP material), a hardox (abrasion resistant steel plate), and a weldox (a high tensile steel plate) can be selected.

Yield point of these steel materials, while the typical rolled steel for general structure (SS400) is 245 N / mm ^2, a spring steels (SUP material) 1080N / mm ^2, Hadokkusu (abrasion steel) is 1000~1300N / mm ^2, well-Dox (high tensile steel) is 700 N / mm ^2. Hardox and Weldox are collectively referred to as Swedish steel, and both are products of Swedish Steel.

  When the strength of rolled steel for general structures is used as a standard, considering the workability of cutting, grinding, polishing, etc., the availability of delivery dates, and the costs of material and processing, etc. Those having a yield point of about 2.5 to 4.0 times the steel material are desirable.

  In addition, the thickness of the overhang is desirably as thin as possible from the viewpoint of reducing the excavation resistance of the ground. For a spring steel material or a Swedish steel material, the thickness should be at least 4.5 mm. In consideration of the above, it is desirable to be about 10 to 15 mm.

  In addition, the length of the overhang portion inserted into the ground outside the hole wall of the excavation hole is such that the resistance moment obtained from the passive resistance of the overhang portion exceeds the rotational moment of the corotation prevention wing determined by the rotation of the excavation rod. To decide. Empirically, it may be about 10 cm, but in general, the rotational moment of the co-rotating wing due to the rotational force of the drill rod increases in proportion to the drilling diameter. It is necessary to change the lateral length and height of the overhang.

For example, it is possible to change to an optimum size according to the target ground by making it replaceable by bolting or the like, and by making the overhang portion detachable from the co-rotation prevention wing body.
Also, as for the attachment of the overhang to the anti-corotating wing body, for example, if the connection side end of the overhanging portion is overlapped with the anti-corotating wing body and attached by high-strength bolt friction welding, it is easy to join and detach. And a strong joint is formed.

  Alternatively, if the overhang is attached to the tip of the co-rotation prevention wing body so that it can be bent, it can be bent at an arbitrary angle and fixed to adjust the length of the part inserted into the outer ground. it can.

  For this reason, the entire length of the overhang portion is usually 10 cm in length of the portion inserted into the ground outside the hole wall of the excavation hole, and the length of the portion to be bolted by being overlapped with the end of the co-rotation prevention wing main body. It is sufficient if the length is about 10 cm and the total is about 20 cm. In addition, by making the length longer than this, the length of a portion to be inserted into the ground outside the hole wall can be freely set.

  For example, when the rotational moment of the co-rotation prevention blade due to the rotational force of the excavation rod becomes larger than expected, the length of a portion inserted into the ground outside the hole wall surface can be freely set and changed.

  Further, the anti-corotating blade can be further enhanced by attaching one to each of the upper and lower sides of the stirring blade with the stirring blade interposed therebetween.

  Furthermore, by attaching the overhanging part between the tip of the anti-corotating wing body and connecting the upper and lower anti-corotating wings to form a box when viewed from the side, it not only enhances the anti-corotating effect, but also excavates The construction accuracy can be improved by preventing the displacement of the excavating rod inside.

  In addition, by forming the blade shape (shape of the knife of the kitchen knife) at the lower end or the upper and lower ends of the overhang, it is possible to further reduce the resistance of the ground generated at the overhang when excavating and lifting.

  In addition, as described above, there are two types of post-burial method and simultaneous burial method in the construction of steel pipe soil cement piles. The anti-corotating blade and the stirring blade may be bent so that the diameter at the time of bending is equal to or smaller than the inner diameter of the steel pipe embedded in the soil cement column.

ADVANTAGE OF THE INVENTION According to the excavation stirring head of this invention, a heavy machine is not separately needed in construction of a steel pipe soil cement pile, and thereby, a construction period can be shortened, cost reduction by reduction of heavy machines, reduction of residual soil, and reduction of vibration and noise are possible. .
Further, since the surrounding ground and the supporting ground are not disturbed by the auxiliary construction method, there is no possibility that the supporting force is reduced, and it is possible to build a high quality soil cement.

FIG. 3 shows an embodiment of a digging and stirring head according to the present invention, in which (a) is a front view, (b) is a side view, (c) is a view from arrow A of (a), and (d) is (a). FIG. FIG. 3 shows an example of a conventional excavating and stirring head as a comparative example, in which (a) is a front view and (b) is a bottom view. It is the figure which showed the boring column diagram and conversion N value in the construction test of the excavation stirring head which concerns on this invention, and the relationship of the time and depth of the construction process of the Example of this invention and a comparative example. It is a front view showing other embodiments of the excavation stirring head concerning the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of the excavation and stirring head 1 for a hard ground according to the present invention. In this example, the shaft 2 (outer diameter 318.5 mm) of the excavation stirring head 1 (excavation diameter 1400 mm) is connected to the tip of the excavation rod (not shown).

  A plurality of excavating bits 2a are attached to the conical portion at the lower end of the shaft portion 2, and three lower excavating wings 3 (outer diameter 750 mm) are provided around the axis immediately above the excavating bit 2a. The lower excavation wing 3 is attached so that the wing surface is obliquely downward with respect to the excavation direction, and a plurality of excavation bits 3a are attached to the lower part of each wing.

  Above the lower excavation wing 3, a pair of upper excavation wings 4 (outer diameter 1400 mm) are provided around the axis. The upper excavation wing 4 is attached so that the wing surface is inclined downward with respect to the excavation direction, and a plurality of excavation bits 4a are attached to the lower part of each wing. In the drawing, the state in which the upper excavation wing 4 is rotated by 90 ° is indicated by a two-dot chain line.

  Above the upper excavation wing 4, a pair of co-rotation prevention wings 5 (outer diameter 1600 mm) is loosely fitted to the shaft portion 2 via the boss 5 c. (The two-dot chain line is rotated 90 °).

  The anti-corotating wing 5 used in this embodiment includes a wing body 5a and an overhang portion 5b. The wing body 5a is formed by inserting a base end of a rolled steel plate for general structure (SS400) having a thickness of 25 mm, a length of 450 mm, and a height of 220 mm between a pair of end fixing plates 5d welded to the outer surface of the boss 5c. , Bolts 5e.

  The overhang portion 5b is formed by welding a base end of a wear-resistant steel plate (HARDOX 400) having a thickness of 12 mm, a length of 150 mm, and a height of 220 mm to the tip of the wing body 5a.

  FIG. 2 shows a conventional excavation stirring head 11 as a comparative example. In this example, the shaft 12 (outer diameter 216.3 mm) of the excavation stirring head 11 (excavation diameter 1400 mm) is connected to the tip of the excavation rod (not shown).

  A plurality of excavating bits 12a are attached to the lower end of the shaft portion 12, and a pair of lower excavating wings 13 (outer diameter 700 mm, two-dot chain line rotated 90 °) are provided around the axis immediately above the excavating bit 12a. The lower excavation wing 13 is attached so that the wing surface is inclined downward with respect to the excavation direction, and a plurality of excavation bits 13a are attached to the lower part of each wing.

  Above the lower excavation wing 13, a pair of upper excavation wings 14 (1400 mm in outer diameter) are provided around the axis. The upper excavation wing 14 is attached so that the wing surface faces obliquely downward with respect to the excavation direction, and a plurality of excavation bits 14a are attached to the lower part of each wing.

Above the upper excavation wing 14, a pair of co-rotation prevention wings 15 (outer diameter 1600 mm) is loosely fitted to the shaft portion 12 via a boss 15c, and a pair of stirring wings 16 (two-dot chain line) is provided above the boss 15c. Is rotated 90 °).
The anti-corotating blade 15 is made of a conventional rolled steel sheet for general structure (SS400).

  In order to compare the excavation performance of these excavating and stirring heads, a construction test was performed on actual hard ground. In addition, soil cement that had not yet solidified was collected from the built soil cement column and packed in a mold to prepare a test specimen. A uniaxial compression test was performed at a material age of 7 days and 28 days to confirm the strength.

  The left side of FIG. 3 is a boring column diagram showing the outline of the test ground. On this ground, a soft layer with an N value of 2 to 7 is deposited from the surface layer to 10.9 m, and a gravel soil with an N value of about 40 from 10.9 m to 12.3 m. There are strong weathered granites and weathered granites.

The right side of FIG. 3 shows the relationship between the time and the depth of the construction process of the present invention and the comparative example.
In both Examples and Comparative Examples, from the ground surface to a depth of 15.9 m, while discharging cement milk of W / C = 120%, the amount of cement added from the discharge port was 300 kg / m ³ per excavation volume. With the upper limit speed set at 30 cm per minute, the digging was performed at a speed that allows digging, and with a forward rotation.

When the depth is 15.9 m or less, the upper limit speed is set to 20 cm / min while discharging cement milk of W / C = 60% so that the amount of cement added from the discharge port becomes 1000 kg / m ³ per excavation volume. I dug in a positive rotation at a speed that allowed me to dig.

  The speed of the conventional excavation and stirring head, which is a comparative example, gradually decreases from a depth of about 11 m (the gravel layer according to the column diagram), and at 18.0 m (equivalent N value of about 200), the velocity of the excavation and stirring head is reduced by the deviation from the excavation axis. The presumed vibration increased, making it impossible to excavate.

  Similarly, in the example, the speed is slightly decreased from the vicinity of the depth of 11 m (the gravel layer according to the column diagram), but the excavation property is better than the comparative example. When the N value exceeded 250, although the speed was reduced, there was no deviation from the excavation axis, and it was possible to excavate up to 19.5 m (estimated converted N value exceeds 300).

Table 1 shows the results of the strength tests of the test specimens obtained from the soil cement columns constructed in the present invention and the comparative examples. In both the present invention and the comparative example, it was confirmed that the required strength was 15 N / mm ² and the strength was sufficient.

  According to the test results, the maximum value of the converted N value that can be excavated was 200 in the conventional excavation and stirring head as a comparative example, whereas in the example, excavation was possible up to about 300. It was confirmed that the required strength was satisfied with respect to the strength of the soil cement column.

  FIG. 4 shows an example of a digging and stirring head 1 for a simultaneous burial method as another embodiment of the digging and stirring head 1 corresponding to hard ground according to the present invention.

  Although the basic configuration is the same as that of the embodiment of FIG. 1, the upper excavation blade 4, the co-rotation prevention blade 5, and the stirring blade 6 are rotated around the rotation shafts 4r, 5r, and 6r, respectively, for use in the simultaneous burial method. The diameter at the time of bending is set to be smaller than the inner diameter of the steel pipe buried in the soil cement column.

  A plurality of excavation bits 2a are attached to a conical portion at the lower end of the shaft portion 2, and three lower excavation wings 3 are provided around the axis immediately above the excavation bit 2a. The lower excavation wing 3 is attached so that the wing surface is obliquely downward with respect to the excavation direction, and a plurality of excavation bits 3a are attached to the lower part of each wing.

  Above the lower excavation wing 3, a pair of upper excavation wings 4 is provided around the axis. The upper excavation wing 4 is attached so that the wing surface is inclined downward with respect to the excavation direction, and a plurality of excavation bits 4a are attached to the lower part of each wing. In the figure, a state where the upper excavation wing 4 is bent around the rotation axis 4r is indicated by a two-dot chain line.

  Above the upper excavation wing 4, a pair of co-rotation prevention wings 5 is loosely fitted to the shaft portion 2 via the boss 5 c, and in this embodiment, a pair of agitating wings 6 is provided thereabove. In the drawing, the bent state is indicated by a two-dot chain line.

  The co-rotation prevention wing 5 includes a wing main body 5a and an overhang portion 5b as in the embodiment of FIG. 1, and can be bent at the mounting position of the wing main body 5a. A rolled steel plate for general structure (SS400) having a thickness of 25 mm is used for the wing body 5a, and a wear-resistant steel plate (HARDOX 400) having a thickness of 12 mm is used for the overhang portion 5b.

  As described above, the preferred embodiments of the present invention have been described together with the comparative examples. However, it is needless to say that the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the object and spirit of the present invention. It is.

1: Excavation stirring head,
2. Shaft,
2a ... drill bit,
3: Lower excavation wing,
3a: drill bit 4: upper drill wing,
4a: drill bit,
4r: rotating shaft,
5 ... anti-rotation wing,
5a ... wing body,
5b ... overhang,
5c ... boss,
5d: end fixing plate,
5e ... bolt,
5r ... rotating shaft,
6 ... stirring blades,
6r ... Rotary axis

Claims (8)

Connected to a drilling rod, discharges cement milk from the tip and mixes and stirs it with the ground to build a soil cement column, and drilling and stirring for steel pipe soil cement pile construction used to bury a steel pipe in the soil cement column A head connected to the excavation rod, a lower excavation wing provided at the tip of the shaft and having a smaller diameter during rotation than the excavation diameter; An excavating and stirring head comprising : a pair of upper excavating wings corresponding to a diameter; a plurality of co-rotation preventing wings loosely fitted to the shaft portion and longer than the upper excavating wing; and a plurality of stirring blades. The tip of the shaft has a downward conical shape, and the lower excavation wing is provided three or more around the axis of the tip of the shaft portion, and the anti-corotation wing body and the anti-corotation wing body Attached to the end of A part or the whole thereof is formed with an overhang portion inserted into the ground outside the hole wall surface of the excavation hole excavated by the upper excavation wing, and the overhang portion is formed thinner than the co-rotation prevention wing body, and A drilling and stirring head for construction of a steel pipe soil cement pile, wherein the drilling and stirring head is formed of a material having a higher strength than a material of a rotation preventing wing body.   2. The excavating and stirring head for steel pipe soil cement pile construction according to claim 1, wherein a diameter of the lower excavating wing when rotated is 0.4 to 0.7 times an excavating diameter of the upper excavating wing. Drilling / mixing head for soil cement pile construction.   3. The excavation and stirring head for steel pipe soil cement pile construction according to claim 1, wherein a yield point of the overhang portion of the co-rotation prevention wing is at least 2.5 times a yield point of a steel material forming the co-rotation prevention wing body. 4. A drilling / mixing head for construction of a steel pipe soil cement pile.   The excavation and stirring head for steel pipe soil cement pile construction according to claim 1, 2 or 3, wherein an edge is formed at a lower end or upper and lower ends of the overhang portion. Stirring head.   The excavation and stirring head for steel pipe soil cement pile construction according to any one of claims 1 to 4, wherein the overhang portion of the co-rotation prevention wing is detachably attached to the co-rotation prevention wing body. Drilling and stirring head for steel pipe soil cement pile construction.   The excavation and stirring head for construction of a steel pipe soil cement pile according to claim 5, wherein a connection side end of the overhang portion is overlapped with the co-rotation prevention wing body and attached by high-strength bolt friction welding. Drilling / mixing head for steel pipe soil cement pile construction.   The excavation and stirring head for steel pipe soil cement pile construction according to claim 1, wherein the overhang portion of the co-rotation prevention wing is bendably attached to a tip end of the co-rotation prevention wing body. Drilling and stirring head for construction of steel pipe soil cement pile.   The excavation and stirring head for steel pipe soil cement pile construction according to any one of claims 1 to 7, wherein the upper excavation wing, the co-rotation prevention wing, and the agitation wing are bendable. A drilling and stirring head for construction of a steel pipe soil cement pile, the diameter of which is equal to or less than the inner diameter of a steel pipe buried in the soil cement column.

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