JP2014043732A - Drill head, drill device, and construction method of widened excavation hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill head with which an intra-hole widened part can be surely constructed by upward drilling after drilling to a predetermined depth regardless of a ground state in spite of a simple structure, a drill device, and a construction method of a widened excavation hole.SOLUTION: In a drill head 10, a plurality of excavation blades 20 each including a downward excavation chip 21b at a bottom face side are disposed upwards at a radially outer side with respect to a rotation center and at equal intervals in a rotation direction, projected towards a distal end center and mounted to a distal end of a drill shaft 101. The drill head 10 comprises: an angle adjusting mechanism 13 for enlarging a drill head diameter; and an upward excavation chip 21a disposed at a top face side of the excavation blade 20 in at least a diameter-enlarged state. The upward excavation chip 21a is set in such a manner that an excavation area S1 that is a cross-sectional area of a widened portion excavated by the upward excavation chip 21a becomes an area corresponding to a downward excavation area S excavated by the downward excavation chip 21b.

Description

  The present invention relates to a drill head that is attached to the tip of a drill that rotates to excavate the ground, a drill device that is equipped with the drill head, and a method for constructing a widened excavation hole.

Conventionally, for example, in order to construct a pile or the like, the ground is often excavated with a rotating drill to construct a drilling hole, and further, there is a method of widening the tip of the drilling hole that becomes the pile bottom in the ground. A lot of construction methods and drill heads have been proposed.
For example, the widening excavation method of the following patent document 1 is one of them.

  The widening excavation method of Patent Document 1 includes a spiral auger, an excavation blade for enlargement excavation, and a liquid injection nozzle for injecting liquid toward the outer peripheral side in the drill head, and the excavation blade is accommodated inside the outer periphery of the spiral auger. In the stored state, the drilling is performed to a predetermined depth, and then the ground is loosened with the water jet by rotating while jetting the water jet from the liquid jet nozzle, and the drill head is rotated with the drilling blade protruding to rotate into the hole. This is a method of excavating the widened portion upward.

  In this method, in addition to the configuration in which the excavating blade is widened, a configuration in which the water jet is ejected from the liquid ejecting nozzle is necessary, and there is a problem that the configuration of the apparatus becomes complicated. In addition, after the surrounding ground is loosened with a water jet, the widened part in the hole is excavated with a drilling blade. The excavation resistance when excavating the inner widened portion is increased, and there is a possibility that the widened portion in the hole cannot be excavated sufficiently.

JP 2008-106426 A

  Therefore, in the present invention, a drill head, a drill device, and a widening excavation hole that can be reliably constructed by excavating upward after excavating to a predetermined depth regardless of the ground state, although having a simple structure. It aims to provide a method.

  In the present invention, a plurality of excavating blades having excavation bits arranged at appropriate intervals in the radial direction on the bottom surface side are arranged radially outwardly upward with respect to the rotation center and at equal intervals in the rotation direction and directed toward the center of the tip. A drill head configured to be convex and mounted on the tip of a drill that is rotated by a drill device, and is disposed on the upper surface side of the drilling blade at least in a diameter-expanded state, and a diameter-expanding means that expands the diameter of the drill head. And an upper excavation means having an upward excavation bit, and the excavation bid provided on the excavation blade, wherein the widening section cross-sectional area is a cross-sectional area of the widened portion excavated by the upper excavation means. It can be characterized in that it is set so as to have an area corresponding to the cross-sectional area of the excavation hole excavated in step (b).

The drill can be an excavating jig for excavating by rotating an auger screw, a screw drill or the like.
The excavation hole to be excavated is a concept including not only an excavation hole formed by rotating a drill or the like but also an excavation hole by drilling or a boring hole.

  Arranged on the upper surface side of the excavating blade in at least the above-described diameter-expanded state means that if it is disposed on the upper surface side in the expanded diameter state, it is disposed even if disposed on the upper surface side in the state before the diameter expansion. Alternatively, it may be configured such that it is not exposed in the state before the diameter expansion and appears on the upper surface side in the diameter expansion state.

According to the present invention, it is possible to reliably construct the widened part in the hole by excavating upward after excavating to a predetermined depth regardless of the ground state, though it is a simple structure.
Specifically, a plurality of excavating blades having excavation bits arranged on the bottom surface side at an appropriate interval in the radial direction are arranged radially outwardly upward with respect to the rotation center and arranged at equal intervals in the rotation direction, and protrude toward the center of the tip. A drilling hole can be constructed to a predetermined depth by mounting the drill head configured in the shape on the tip of a drill rotated by a drill device.

  Further, the drill head is provided with a diameter expanding means for expanding the diameter of the drill head, and an upper drilling means disposed at least on the upper surface side of the drilling blade in the diameter-expanded state and having an upward drilling bit. After drilling to the depth, the diameter of the drill head is expanded by the diameter expanding means, and the drill wall in which the upper drilling means is arranged on the upper surface side of the drill blade in the expanded diameter state is rotated, thereby drilling the hole wall upward, The excavation hole can be widened to construct an in-hole widened portion. The in-hole widening portion may be constructed at any height of the excavation hole excavated to a predetermined depth.

  In addition, the widened section sectional area, which is the sectional area of the widened portion excavated by the upper excavating means, is an area corresponding to the sectional area of the excavating hole excavated by the excavation bid provided in the excavating blade. Is set by the upper excavation means so that the cross-sectional area of the excavation hole determined according to the rotation capability of the drilling device, that is, the area according to the excavation area when excavating to a predetermined depth is obtained. Since the cross-sectional area of the widened portion, which is the cross-sectional area of the widened portion, is set, the hole wall of the excavated hole that has already been excavated when the hole wall of the excavated hole is excavated upward by the upper excavating means regardless of the ground condition. Can be excavated upward as a guide, and the excavation hole can be reliably widened to construct an accurate widened portion in the hole.

As an aspect of the present invention, the cross-sectional area of the widened portion can be set to have an area of about 1.3 times or less with respect to the cross-sectional area of the excavation hole.
According to the present invention, the hole wall of the excavation hole can be excavated upward by the upper excavation means regardless of the ground state, and the excavation hole can be more reliably widened.

  Specifically, when the cross-sectional area of the widened portion is larger than the cross-sectional area of the drilling hole, such as twice or three times the cross-sectional area of the drilling hole, the excavation resistance exceeds the rotational capability of the drilling device. The hole wall of the excavation hole cannot be excavated upward by the upper excavation means.

  On the other hand, when the cross-sectional area of the widened portion is, for example, less than 1 times the cross-sectional area of the excavation hole, the upward excavation resistance is equal to or less than the equivalent due to excavation resistance when excavating to a predetermined depth. The hole wall of the excavation hole can be excavated upward by the upper excavation means.

  However, when excavating to a predetermined depth, it is necessary to excavate the solid ground and build a hole, that is, without excavation of the excavated excavated soil, it is necessary to move upward with the upper excavation means When excavating, it is only necessary to excavate the hole wall of the already constructed hole, and the excavation resistance is smaller than that when excavating to a predetermined depth.

  Therefore, by setting the cross-sectional area of the widened portion to be about 1.3 times or less than the cross-sectional area of the excavation hole, the hole wall of the excavation hole is excavated upward by the upper excavation means, and excavation It is possible to construct the in-hole widened portion by widening the hole more reliably. In addition, by setting the cross-sectional area of the widened portion so as to have an area of about 1.3 times or less than the cross-sectional area of the excavation hole, the widened portion in the hole is approximately 1.5 times the diameter of the excavation hole. It can be constructed with about twice the diameter. Here, the area of about 1.3 times or less than the cross-sectional area of the above-mentioned excavation hole means that, for example, when the excavation diameter is adjustable within a predetermined range, the maximum excavation within the adjustable range is possible. The area is about 1.3 times or less of the diameter.

  Further, even when the hole widening portion is constructed by drilling upward using the hole wall of the already drilled hole as a guide, the cross-sectional area of the widening portion is about 1 with respect to the cross-sectional area of the drilling hole. Since the area is set to be 3 times or less, as described above, it is possible to prevent the excavation load due to upward excavation from acting excessively, and without breaking the hole wall of the already excavated excavation hole, A widened part can be constructed.

  Further, as an aspect of the present invention, the diameter expanding means is composed of tilting means for allowing the excavating blade to tilt outward in the radial direction around the rotation center of the tip, and tilt adjusting means for adjusting the tilt of the excavating blade. can do.

  According to the present invention, the drill head diameter can be reliably expanded with a simple structure. Therefore, after excavation to a predetermined depth, the excavation blade is tilted outward by the tilt adjustment means to cause the upper excavation means to appear, the hole wall is excavated upward, the excavation hole is widened, and the in-hole widening portion is constructed. be able to.

Further, the present invention is a drilling device in which the above-described drill head is mounted on the drill.
For the above-described reason, although it is a simple structure, it is possible to reliably construct the widened portion in the hole by excavating upward after excavating to a predetermined depth regardless of the ground state.
The drill device may be a placement type or a self-propelled drill device.

As an aspect of the present invention, the drill device can be a low head drill device.
According to the present invention, even if the drilling device is a low-low-head drilling device having a low rotational capability, the hole wall of the drilling hole is drilled upward by the upper drilling means regardless of the ground condition, and the drilling hole is more reliably widened. can do.

  In addition, the low-head drilling device has a lighter weight than a normal drilling device, and it is difficult to secure a reaction force when drilling to a predetermined depth in a normal state where the diameter is not expanded, and a large-diameter drilling hole is drilled. Since this is difficult, it is often required to construct a widened portion in the hole. In such a situation, the cross-sectional area of the widening portion in which the widening portion cross-sectional area, which is the cross-sectional area of the widened portion excavated by the upper excavation means, is excavated by the excavation bid provided in the excavation blade is used for the upper excavation means. By setting the area according to the area and drilling upwards, even if it is a low-head drilling device with low rotation capability and light weight, it will be lifted by excavation resistance regardless of the ground condition In addition, the hole wall of the excavation hole can be excavated upward by the upper excavation means, and the excavation hole can be more reliably widened.

Further, as an aspect of the present invention, there is provided a suction means for sucking excavated soil from a suction port arranged at an upper portion of the drill head.
According to the present invention, excavated soil can be sucked from the suction port during excavation or after excavation. Therefore, it is possible to prevent excavation soil from accumulating at the excavation site and increasing excavation resistance without providing another suction device.

  Furthermore, the present invention uses the above-described drill apparatus, rotates the drill, and constructs a drilling hole by excavating the predetermined depth while sucking excavated soil with the suction means, and then operates the diameter expanding means. The diameter of the drill head is increased, the upper excavation means is appeared, the drill is rotated, and the upper excavation means is excavated at the upper part and is pulled up to a predetermined height to construct the widened portion in the hole, After the construction of the widened portion in the hole, the method is a method for constructing the widened excavation hole that lowers the drill and sucks the excavated soil excavated by the upper excavating means deposited on the bottom of the hole.

By this construction method, regardless of the ground condition, the hole wall of the excavation hole can be excavated upward by the upper excavation means, and the excavation hole can be reliably widened to construct the widened portion in the hole.
In addition, after drilling to a predetermined depth, the drill head is expanded, the upper drilling means is excavated to the upper part and pulled up to a predetermined height to build the widened part in the hole, and then the drill is lowered and deposited on the bottom of the hole Since the excavated soil excavated by the upper excavating means is sucked, an excavated hole having an in-hole widened portion in which excavated soil is not deposited at the hole bottom can be constructed.

  In addition, since excavating to a predetermined depth and then pulling it up to a predetermined height to construct the widened portion in the hole and further descending and sucking the excavated soil with the suction means, the time for leaving the hole wall of the excavated hole as it is is short. Therefore, the hole wall is not collapsed, and a diameter-expanded hole having a more desired shape can be constructed.

  According to the present invention, a drill head, a drill device, and a method for constructing a widening excavation hole, which can be constructed with a simple structure, without being dependent on the ground state, after excavating to a predetermined depth and then excavating upward to reliably construct the widened portion in the hole Can be provided.

Explanatory drawing of a drill head. Explanatory drawing of an expanded state drill head. Schematic diagram of a low-head excavator. The flowchart which builds a bottom cast-in-place pile by RCD method. Explanatory drawing explanatory drawing of an expanded excavation hole. The flowchart which constructs a wide cast-in-place pile by RCD method. Explanatory drawing of widening excavation hole.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram of the drill head 10, FIG. 2 is an explanatory diagram of the diameter-expanded drill head 10 a, and FIG. 3 is a schematic diagram of the low-head drilling machine 100. Specifically, FIG. 1 (a) shows a front view of the drill head 10, and FIG. 1 (b) shows an AA arrow view in FIG. 1 (a). 2 (a) and 2 (b), the diameter-expanded state drill head 10a is illustrated in the same manner as in FIGS. 1 (a) and 1 (b). In FIG. 1A and FIG. 2A, only the stabilizer 30 is shown in the BB arrow view in FIG. In FIG. 1B, the stabilizer 30 is indicated by a broken line.

  FIG. 4 shows a flowchart for constructing a bottomed cast-in-place pile by the RCD method, and FIG. 5 shows a drilling construction explanatory diagram of the bottomed excavation hole Kt for constructing the bottomed cast-in-place pile.

  Further, FIG. 6 shows a flowchart for constructing a widened cast-in-place pile by the RCD method, and FIG. 7 shows an explanatory diagram of excavation construction of the widened excavation hole Kf for constructing the widened cast-in-place pile.

The drill head 10 is a drill head that is detachably attached to the tip of a drill shaft 101 provided in the low-head excavator 100 shown in FIG. 3, can drill hard soil, and can widen the drilling diameter.
Specifically, the drill head 10 includes a head shaft 12 attached to the tip of the drill shaft 101 by the detaching means 11, four excavating blades 20 arranged at equal intervals in the radial direction on the outer peripheral surface of the head shaft 12, An angle adjusting mechanism 13 for adjusting the inclination angle of the excavating blade 20 and a tip bit 14 disposed on the tip side of the head shaft 12 are configured.

  The drill shaft 101 and the head shaft 12 are constituted by a hollow tube connected so as to be conductive by the attaching / detaching means 11, and a soil discharge facility such as a suction / jet / airlift type is connected to the upper end side of the drill shaft 101, An excavation soil H excavated by the drill head 10 is sucked from the tip opening portion 12a of the head shaft 12 so as to excret the soil.

  The tip bit 14 has a convex shape with the bottom center convex downward, and a plurality of excavation tips 14a are arranged at predetermined intervals in the radial direction along a bottom surface portion inclined obliquely upward from the center of the bottom toward the radially outer side. doing.

  Further, a suction opening 14b that is an opening that allows passage of excavated soil sucked from the tip opening 12a is provided in a portion facing the tip opening 12a of the head shaft 12 in the upper center of the tip bit 14.

  The excavating blade 20 is an excavating blade configured such that the tilt angle can be adjusted with respect to the head shaft 12 with a pivot axis (not shown) as a pivot center, and as shown in FIG. Four are arranged at equal intervals.

  As shown in FIG. 2A, the excavating blade 20 is formed in a substantially trapezoidal shape in which the bottom portion 20b is inclined obliquely upward in the radially outward direction in a state where the upper portion 20a is substantially horizontal. A plurality of downward excavation tips 21b are provided along 20b at predetermined intervals in the radial direction. Further, a plurality of upward excavation tips 21a are provided in the predetermined range outside the diameter of the upper side portion 20a with a predetermined interval in the radial direction. The predetermined range outside the diameter where the upward excavation tip 21a is arranged will be described in detail later.

  The angle adjusting mechanism 13 is connected to an outer fitting ring 13a that is slidably fitted to the head shaft 12 so as to be slidable in the vertical direction, and one end 13ba is connected to the outer fitting ring 13a so as to be pivotable in the vertical direction. By connecting the end portion 13bb to the excavating blade 20, the outer fitting ring 13a and the connecting arm 13b for connecting the excavating blade 20 are formed.

The external fitting ring 13a is configured such that the vertical position with respect to the head shaft 12 is regulated by a jack (not shown).
One connecting arm 13b is provided for each of the four excavating blades 20 arranged.

  Further, the connection between the other end portion 13bb of the connecting arm 13b and the excavating blade 20 will be described in detail. The other end portion 13bb is configured to be slidable in parallel with the upper side portion 20a in the vicinity of the upper side portion 20a of the excavating blade 20. The slide shaft 22 is connected to the excavating blade 20 so as to be rotatable about the slide shaft 22.

  By the angle adjusting mechanism 13 configured as described above, the inclination angle of the excavating blade 20 configured to be able to adjust the inclination angle with respect to the head shaft 12 with the pivot shaft (not shown) as the pivot center can be regulated. .

Specifically, when the outer fitting ring 13a is regulated at the upper position by a jack (not shown), as shown in FIG. 1 (a), the inclination angle is steep via the connecting arm 13b and the slide shaft 22. The inclination angle of the excavating blade 20 can be regulated.
On the other hand, when the outer fitting ring 13a is restricted to the lower position by the jack, as shown in FIG. 2 (a), the excavation blade 20 tilts and tilts via the connecting arm 13b and the slide shaft 22. The angle is regulated in a gradual state.

  In contrast to the normal state where the inclination angle is steep as shown in FIG. 1A, as shown in FIG. 2A, the excavating blade 20 is inclined and the inclination angle becomes gentle, so that the excavation is performed. The area S is in an enlarged diameter state. By the way, in this specification, the drill head 10 in an expanded state in which the diameter of the excavation area is expanded by tilting the excavating blade 20 and making the inclination angle gentle is referred to as an expanded-diameter drill head 10a for convenience. . Further, as shown by circular hatching in FIG. 1B, the area of the range that can be excavated by the drill head 10 in a normal state is defined as a downward excavation area S.

Next, a predetermined range that is a range in which the upward excavation tip 21a is arranged on the outer diameter side of the upper side portion 20a of the excavation blade 20 will be described.
A ring-shaped area in plan view obtained by rotating the range in which the upward excavation tip 21a is disposed, that is, the upward direction disposed in a predetermined range outside the diameter in the upper side portion 20a of the excavation blade 20 in accordance with the rotation of the expanded diameter drill head 10a. The upward excavation area S1 excavated by the excavation tip 21a is set according to the downward excavation area S excavated by the drill head 10 in a normal state.
Specifically, the upward excavation area S1 is set to be about 1.3 times or less than the downward excavation area S.

In this embodiment, the diameter of the drilling hole when drilling by rotating the drill head 10 in the normal state is 2000 mm, and the downward drilling area S at that time is set to 3.14 m ^2. The rotation trajectory area due to the rotation of the head 10a is 7.065 m ² , the diameter at that time is 3000 mm, which is 1.5 times the diameter of the drill head 10, and the upward excavation area S1 by the upward excavation tip 21a is the downward excavation area It is set to be 1.25 times S.

Between the angle adjusting mechanism 13 and the excavating blade 20 configured as described above, a rotatable stabilizer 30 is provided which is regulated in the vertical direction with respect to the head shaft 12.
The stabilizer 30 constitutes an outer fitting ring 31 that is rotatably fitted to the head shaft 12 above the angle adjusting mechanism 13 and a downward excavation area S by the drill head 10 as shown in FIG. The ring member 32 has substantially the same diameter as the circular shape in plan view, and the connecting bar 33 that connects the outer fitting ring 31 and the ring member 32 in the radial direction. Note that eight connecting bars 33 are arranged at equal intervals in the circumferential direction. Further, in the cross section of the ring member 32, the upper and lower ends are bent inwardly to form an end taper 32a.
The drill head 10 configured as described above is used by being mounted on the tip of the drill shaft 101 mounted on the low-head excavator 100 as described above.

Subsequently, a method for constructing a bottom-span cast-in-place pile by the low head excavator 100 equipped with the drill head 10 will be described.
As a method for constructing a cast-in-place pile by using the low-head excavator 100 equipped with the drill head 10, a reverse circulation method (hereinafter referred to as RCD method) will be described below. The method of excavating the excavation hole using the head 10 is not limited to the above RCD method, and may be used other than the construction of a pile, for example.

  In the RCD method, soil is excavated by the drill head 10 attached to the tip of the drill shaft 101 while holding the hole wall with the hydrostatic pressure of the bentonite solution filled in the excavation hole, and the earth removal mechanism H is used by reverse circulation with water. After excavating the excavated soil, concrete is driven into the excavation hole to create a pile.

  In order to construct the RCD method, facilities such as a low-head excavator 100, a soil removal facility connected to the upper end of the drill shaft 101, and a water storage tank are required. Although FIG. 3 shows a stationary low-head excavator 100, a self-propelled excavator such as a crawler may be used.

  A specific construction method will be described with reference to FIGS. In this construction, a case will be described in which a bottomed pile having a depth reaching the support layer Gs composed of the hard soil below the soft layer Gn on the surface is constructed.

  First, as shown to Fig.5 (a), the stand pipe 110 is built in the surface layer Gh (step s1). Then, as shown in FIG. 5B, the low head excavator 100 is installed on the ground surface, and primary excavation is performed from the inside of the stand pipe 110 with the drill head 10 in a normal state (step s2). At this time, the excavated earth and sand excavated by the downward excavation tip 21 b of the excavating blade 20 is sucked from the tip opening 12 a of the head shaft 12 and discharged through the inside of the drill shaft 101. In addition, in FIG.5 (c) thru | or (f), illustration of the low sky head excavator 100 is abbreviate | omitted.

  Primary drilling is continued until the drill head 10 reaches a predetermined depth (step s3: No), and when the drill head 10 reaches a predetermined depth in the support layer Gs (step s3: Yes), as shown in FIG. Then, while rotating the drill head 10, the drill blade 20 is tilted by the angle adjusting mechanism 13 to expand the diameter of the drill head 10 to obtain a diameter-expanded drill head 10 a (step s 4). A drilling hole drilled to a predetermined depth by the drill head 10 in a normal state is referred to as a primary drilling hole K1.

  Then, as shown in FIG. 5 (d), the diameter-expanded drill head 10a is rotated to perform secondary excavation with the upward excavation tip 21a on the hole wall of the primary excavation hole K1 (step s5). A bottom widened portion K2 that widens the pile bottom of the primary excavation hole K1 is constructed. The secondary excavation is performed up to a predetermined height while being guided by the stabilizer 30 to the hole wall of the primary excavation hole K1 (step s6: No). In the secondary excavation, the secondary excavation is arranged on the upper side portion 20a of the excavation blade 20. The excavated soil excavated by the upward excavation tip 21a accumulates at the bottom of the primary excavation hole K1.

  When the secondary excavation reaches a predetermined height (step s6: Yes), as shown in FIG. 5 (e), the diameter-expanded state drill head 10a is lowered to the pile bottom, and the excavated soil accumulated on the pile bottom is removed by the soil removal mechanism H. Suction and evacuation (step s7), the diameter-adjusted drill head 10a is reduced in diameter by the angle adjustment mechanism 13, and the primary excavation hole K1 above the expanded bottom K2 is pulled up as shown in FIG. 5 (f). (Step s8), the bottomed excavation hole Kt is completed.

  In addition, since the edge part taper 32a is formed in the upper end part of the ring member 32 in the stabilizer 30, even when the stabilizer 30 penetrates into the primary excavation hole K1 exceeding the bottom expansion part K2, the edge part of the ring member 32 is shown. The stabilizer 30 can be guided by the taper 32a and smoothly enter the primary excavation hole K1.

Then, a reinforcing bar is inserted into the bottom expanded excavation hole Kt (step s9), and further, a tremy pipe is erected into the bottom expanded excavation hole Kt (step s10), and concrete is placed in the expanded bottom excavation hole Kt, Is pulled out (step s11). When the concrete is driven to the ground surface, the stand pipe 110 is pulled out and backfilled (step s12), and the RCD method is completed.
By this construction, a cast-in-place pile piled up with the support layer Gs can be constructed.

  Next, a case where an enlarged cast-in-place pile having a diameter larger than the primary excavation hole K1 excavated by the drill head 10 in a normal state is constructed by the RCD method will be described. As described above, in order to construct an enlarged cast-in-place pile having a larger diameter than the primary excavation hole K1 excavated by the drill head 10 in the normal state, the large-diameter expanded excavation hole Kf is excavated, but the hard support layer Gs is used. It is difficult for the low-head drilling machine 100 to excavate by drilling by primary drilling with the drill head 10a having an enlarged diameter.

  Therefore, as shown in FIG. 7A, the stand pipe 110 is installed in the ground layer Gh (step t1), and as shown in FIG. 7B, the low-head excavator 100 is installed on the ground surface, and the stand From the inside of the pipe 110, primary excavation is performed by the expanded diameter drill head 10a in which the soft layer Gn is expanded. This is the primary expanded digging (step t2). At this time, the excavated earth and sand excavated by the downward excavation tip 21 b of the excavating blade 20 is sucked from the tip opening 12 a of the head shaft 12 and discharged through the inside of the drill shaft 101.

  The expanded primary drilling is continued until the expanded diameter drill head 10a reaches the support layer Gs (step t3: No), and when the drill head 10 reaches a predetermined depth in the support layer Gs (step t3: Yes), the drill head 10 is moved. While rotating, the diameter-adjusted drill head 10a is reduced in diameter by the angle adjusting mechanism 13 (step t4).

  Note that a drilling hole drilled to a predetermined depth by the low-head excavator 100 in a normal state is referred to as an enlarged primary drilling hole Ka1. Then, the support layer Gs is subjected to primary drilling with a reduced diameter drill head 10 (step t5: FIG. 7 (c)) and continued until the drill head 10 reaches a predetermined depth. (Step t6: No), when the drill head 10 reaches the predetermined depth in the support layer Gs (Step t6: Yes), as shown in FIG. The excavating blade 20 is tilted to set the drill head 10 to the expanded diameter drill head 10a in the expanded state (step t7). Note that a drilling hole drilled to a predetermined depth by the drill head 10 in a normal state is referred to as a reduced diameter primary drilling hole Ka2.

  Then, as shown in FIG. 7E, the diameter-expanded drill head 10a is rotated to perform secondary excavation upward with the upward excavation tip 21a on the hole wall of the reduced diameter primary excavation hole Ka2 (step t8). ), An expanded bottom portion Ka3 that widens the pile bottom of the reduced diameter primary excavation hole Ka2. The secondary excavation is performed up to a predetermined height while being guided by the stabilizer 30 to the hole wall of the reduced diameter primary excavation hole Ka2 (step t9: No). In this secondary excavation, the secondary excavation is arranged on the upper side portion 20a of the excavation blade 20. The excavated soil excavated by the upward excavation tip 21a is accumulated at the bottom of the primary excavation hole K1.

  When the secondary excavation reaches a predetermined height (step t9: Yes), as shown in FIG. 7 (f), the diameter-expanded state drill head 10a is lowered to the pile bottom, and the excavated soil accumulated on the pile bottom is removed by the soil removal mechanism H. Suction and discharging (step t10), the diameter-adjusted drill head 10a is reduced in diameter by the angle adjusting mechanism 13, and as shown in FIG. 7G, the diameter-expanded primary excavation hole Ka1 above the bottom-expanded portion Ka3. Is pulled up (step t11), and the diameter-expanded excavation hole Kf is completed.

Then, a reinforcing bar is inserted into the enlarged diameter excavation hole Kf (step t12), and further, a tremmy pipe is installed in the enlarged diameter excavation hole Kf (step t13), and concrete is placed in the enlarged diameter excavation hole Kf. Then, the tremy tube is pulled out (step t14). When the concrete is driven to the ground surface, the stand pipe 110 is pulled out and backfilled (step t15), and the RCD method is completed.
By this construction, it is possible to construct a cast-in-place pile whose diameter is larger than that of a normal excavation hole.

  In this way, a plurality of excavating blades 20 having the downward excavation tips 21b arranged on the bottom surface side arranged at appropriate intervals in the radial direction are arranged radially outwardly upward with respect to the rotation center and at equal intervals in the rotation direction. The angle adjusting mechanism 13 for expanding the diameter of the drill head and the drilling blade 20 in the diameter-expanded state are provided on the drill head 10 that is convex toward the head and is mounted on the tip of the drill shaft 101 rotated by the low-head excavator 100. And the upward excavation tip 21a, and the upward excavation tip 21a has an upward excavation area S1 which is a cross-sectional area of the widened portion excavated by the upward excavation tip 21a. Even though it is a simple structure, even if it is a hard support layer Gs, by setting the area according to the downward excavation area S to be excavated with the excavation bid, After digging up Teifuka it is, can be constructed reliably 拡底 portion K2 drilled upward.

  Specifically, a plurality of excavating blades 20 having a downward excavation tip 21b arranged on the bottom surface side arranged at an appropriate interval in the radial direction on the bottom side is arranged radially outward and upward at equal intervals in the rotation direction. The primary drilling hole K1 can be constructed to a predetermined depth by mounting the drill head 10 that is convex toward the tip of the drill shaft 101 that is rotated by the low-head drilling machine 100.

  Further, the drill head 10 is provided with an angle adjusting mechanism 13 for expanding the diameter of the drill head, and an upwardly facing upward drilling tip 21a disposed at least on the upper surface side of the drilling blade 20 in the diameter-expanded state. After the excavation, the drill head diameter is expanded by the angle adjusting mechanism 13 to become the expanded drill head 10a, and the expanded drill head 10a in which the upward drilling tip 21a is disposed on the upper surface side of the drill blade 20 is rotated. Thus, the hole wall can be excavated upward, and the primary excavation hole K1 can be widened to construct the expanded bottom portion K2.

  It should be noted that the upward excavation area S1 which is the cross-sectional area of the widened portion excavated by the upward excavation tip 21a is an area corresponding to the downward excavation area S excavated by the excavation bid provided to the excavation blade 20. Is set by the upward excavation tip 21a so as to have a downward excavation area S determined according to the rotational capability of the low head excavator 100, that is, an area corresponding to the downward excavation area S of the primary excavation hole K1. Since the upward excavation area S1, which is the cross-sectional area of the widened portion, is set, even the hard support layer Gs has already been excavated when the hole wall of the primary excavation hole K1 is excavated upward with the upward excavation tip 21a. The hole wall of the primary excavation hole K1 can be excavated upward using the stabilizer 30 as a guide, and the primary excavation hole K1 is reliably widened so that the bottom portion K2 has high accuracy. It can be constructed.

  Further, by setting the upward excavation area S1 to be about 1.3 times or less the downward excavation area S, the hole wall of the primary excavation hole K1 can be formed even for the hard support layer Gs. The primary excavation hole K1 can be more reliably widened by excavating upward with the upward excavation tip 21a.

  Specifically, when the upward excavation area S1 is larger than the downward excavation area S, for example, twice or three times the downward excavation area S, the excavation resistance exceeds the rotational capability of the low head excavator 100, so that the primary excavation If the hole wall of the hole K1 cannot be excavated upward by the upward excavation tip 21a, and the upward excavation area S1 is, for example, less than or equal to 1 times the downward excavation area S, the excavation resistance when excavating to a predetermined depth Since the upward excavation resistance is equal to or less than that, the hole wall of the primary excavation hole K1 can be reliably excavated upward with the upward excavation tip 21a.

  However, when the primary excavation hole K1 is excavated to a predetermined depth, it is necessary to excavate the ground in a solid state to construct the hole, that is, to excavate without excavating the excavated excavated soil. When excavating upward with the excavation tip 21a, it is only necessary to excavate the hole wall of the already constructed hole, and the excavation resistance is smaller than when excavating to a predetermined depth. Therefore, by setting the upward excavation area S1 to be about 1.3 times or less the downward excavation area S, the hole wall of the primary excavation hole K1 is excavated upward with the upward excavation tip 21a, and the primary excavation area 21 The bottom expanded portion K2 can be constructed by more reliably widening the excavation hole K1. In addition, by setting the upward excavation area S1 to be an area that is about 1.3 times or less than the downward excavation area S, the bottom expanded portion K2 is about 1.5 times the diameter of the primary excavation hole K1. The bottom can be expanded with a diameter of.

  Further, even when the bottom expanded portion K2 is constructed by excavating upward with the hole wall of the primary excavation hole K1 already excavated as a guide, the upward excavation area S1 is about 1.3 with respect to the downward excavation area S. Since the area is set to be twice or less, as described above, it is possible to prevent the excavation load due to the upward excavation from acting excessively, and to expand the bottom without breaking the hole wall of the already excavated primary excavation hole K1. K2 can be constructed.

  In addition, the excavation blade 20 can be tilted outward in the radial direction by the pivot shaft, and the tilt adjustment of the excavation blade 20 is adjusted by the angle adjusting mechanism 13, so that the drill head diameter can be reliably increased with a simple structure. it can. Therefore, after excavating to a predetermined depth, the angle adjusting mechanism 13 tilts the excavating blade 20 outward in the radial direction so that the upward excavation tip 21a appears, excavates the hole wall upward, widens the primary excavation hole K1, and expands the bottom. K2 can be constructed.

  The low head excavator 100 with the drill head 10 mounted on the drill shaft 101 is simple in structure, but after excavating to a predetermined depth regardless of the ground state, the bottom expanded portion K2 is reliably constructed by excavating upward. can do.

  Note that the low-head excavator 100 has a low rotational ability to rotate the drill shaft 101, but even with the hard support layer Gs, the hole of the primary excavation hole K1 is excavated upward by the upward excavation tip 21a to perform the primary excavation. The hole K1 can be expanded more reliably.

  In addition, the low-head excavator 100 is lighter in weight than the normal low-head excavator 100, and it is difficult to secure a reaction force when excavating to a predetermined depth in a normal state where the diameter is not expanded. Since it is difficult to excavate the excavation hole K1, the construction of the expanded bottom portion K2 is often required, but the upward excavation tip 21a is an upward excavation area that is a cross-sectional area of the widened portion excavated by the upward excavation tip 21a. The low-headed excavator 100 is set to have an area corresponding to the downward excavation area S to be excavated by the excavation bid provided on the excavation blade 20 and excavated upward, so that the rotary capability is low and the weight is low. Even if it is the hard support layer Gs, the hole wall of the primary excavation hole K1 is excavated upward by the upward excavation tip 21a without being lifted by excavation resistance, and the primary excavation hole K is obtained. It is possible to more reliably widening the.

  Further, by providing the soil removal mechanism H that sucks excavated soil from the tip opening 12a disposed at the top of the drill head 10, the excavated soil can be sucked from the tip opening 12a while excavating or after excavation. Therefore, it is possible to prevent excavation soil from accumulating at the excavation site and increasing excavation resistance without providing another suction device.

  Furthermore, after the drill shaft 101 is rotated using the above-described low-head excavator 100 and the primary excavation hole K1 is constructed by excavating to a predetermined depth while sucking excavated soil with the soil removal mechanism H, the angle adjusting mechanism is constructed. 13 is expanded to increase the diameter of the drill head, the upward drilling tip 21a appears, the drill shaft 101 is rotated, the upper drilling tip 21a is excavated at the upper part and pulled up to a predetermined height to construct the expanded bottom portion K2. Then, after constructing the bottom expanded portion K2, the hard support layer Gs is formed by the method of constructing the bottom expanded excavation hole Kt for lowering the drill shaft 101 and sucking the excavated soil excavated by the upward excavation tip 21a deposited on the bottom of the hole. Even if it exists, the hole wall of the primary excavation hole K1 is excavated upward by the upward excavation tip 21a, and the primary excavation hole K1 is surely widened to construct the expanded bottom portion K2. Rukoto can.

  In addition, after drilling to a predetermined depth, the drill head 10 is expanded in diameter, and while the upper excavation tip 21a is excavating the upper portion, the drill head 101 is pulled up to a predetermined height to construct the expanded portion K2, and then the drill shaft 101 is lowered to In order to suck the excavated soil excavated by the upward excavation tip 21a deposited on the primary excavation tip 21a, it is possible to construct the primary excavation hole K1 having the expanded bottom portion K2 in which the excavated soil is not accumulated.

  In addition, after excavating to a predetermined depth, the bottom portion K2 is constructed by raising to a predetermined height, and further descends and the excavated soil is sucked by the soil removal mechanism H, so the hole wall of the primary excavation hole K1 is left as it is. Since the time is shortened, the hole wall is not collapsed, and a diameter-expanded hole having a desired shape can be constructed.

As described above, in the correspondence between the configuration of the present invention and the above-described embodiment, the excavation bit corresponds to the downward excavation tip 21b,
Similarly,
The drilling device and the low head drilling device correspond to the low head drilling machine 100,
The drill corresponds to the drill shaft 101,
The diameter expanding means and the tilt adjusting means correspond to the angle adjusting mechanism 13,
The upper excavation means corresponds to the upward excavation tip 21a,
The widened section cross-sectional area corresponds to the upward excavation area S1,
The cross-sectional area of the drilling hole corresponds to the downward drilling area S,
The tilting means corresponds to the pivot axis serving as the pivot center of the excavating blade 20,
The inlet corresponds to the tip opening 12a,
The suction means corresponds to the soil removal mechanism H,
The drilling hole corresponds to the primary drilling hole K1,
The widened part in the hole corresponds to the widened part K2,
The widening hole corresponds to the widening hole Kt,
However, the present invention is not limited to the above embodiment.

  For example, the drill head 10 may be mounted not only on the drill shaft 101 but also on the tip of an auger screw or screw drill. In the above description, the mounting type low-head excavator 100 is used. However, a self-propelled low-head excavator may be used, and further, a non-low-head excavator may be used.

  In the above description, the diameter of the excavating blade 20 is tilted to increase the diameter. For example, the diameter-expanded portion configured to be drawable from the outer diameter portion of the excavating blade 20 may be pulled out and expanded in this case. The excavation tip 21a may be disposed on the upper surface of the drawer portion. Thus, any diameter expansion structure and diameter expansion method may be used regardless of the diameter expansion structure and diameter expansion method of the excavating blade 20.

  In the above description, the bottom portion of the primary excavation hole K1 is excavated with the diameter-expanded state drill head 10a to construct the expanded bottom portion K2. However, any location in the height direction of the primary excavation hole K1 is formed with the upward excavation tip 21a. You may excavate and build the expanded bottom part K2. Further, the bottom expanded portion K2 may be constructed in the soft layer Gn, and the bottom expanded excavation hole Kt having the bottom expanded portion K2 may be formed in the ground which is a hard support layer Gs layer.

DESCRIPTION OF SYMBOLS 10 ... Drill head 10a ... Diameter expansion state drill head 12a ... Tip opening part 13 ... Angle adjustment mechanism 20 ... Excavation blade 21a ... Upward excavation tip 21b ... Downward excavation tip 100 ... Low head excavator 101 ... Drill shaft H ... Excavation mechanism K1 ... primary excavation hole K2 ... bottom expansion part Kt ... bottom expansion excavation hole S ... downward excavation area S1 ... upward excavation area

Claims (7)

A plurality of excavating blades having excavation bits arranged at appropriate intervals in the radial direction on the bottom side are arranged radially outwardly with respect to the rotation center and arranged at equal intervals in the rotation direction so as to protrude toward the center of the tip. A drill head attached to a tip of a drill rotated by a drill device,
A means for expanding the diameter of the drill head;
An upper excavation means disposed at least on the upper surface side of the excavating blade in an expanded state and having an upward excavation bit;
The upper excavation means,
A drill head set so that a cross-sectional area of the widened portion, which is a cross-sectional area of the widened portion excavated by the upper excavating means, has an area corresponding to the cross-sectional area of the excavation hole excavated by the excavation bid provided in the excavating blade. . The drill head according to claim 1, wherein the cross-sectional area of the widened portion is set to have an area of about 1.3 times or less with respect to the cross-sectional area of the excavation hole. The diameter expanding means is
Tilt means for allowing the excavating blade to tilt outward in the radial direction around the rotation center of the tip;
The tilt adjusting means adjusts the tilt of the excavating blade.
The drill head according to claim 1 or 2. A drilling device in which the drill head according to any one of claims 1 to 3 is mounted on the drill. The drilling device according to claim 4, wherein the drilling device is constituted by a low head drilling device. The drill apparatus according to claim 4 or 5, further comprising suction means for sucking excavated soil from a suction port disposed at an upper portion of the drill head. Using the drill device according to claim 6,
While rotating the drill and constructing a drilling hole by drilling to the predetermined depth while sucking excavated soil with the suction means,
While operating the diameter expansion means to expand the diameter of the drill head, the upper excavation means appears,
Rotate the drill, build up the widened part in the hole by pulling up the upper part with the upper excavation means to a predetermined height,
The construction method of the widening excavation hole which draws in excavation soil excavated by the upper excavation means deposited in the bottom of the hole after constructing the widening part in the hole.

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