JP4424051B2 - Reversing enlargement head - Google Patents

Description

  The present invention relates to an expansion digging method for forming a bulb at the lower end of the ground such as an existing pile and a cast-in-place pile, and / or an intermediate expanded pile, and an expansion head used for the method.

  Conventionally, for example, as shown in FIG. 6, an enlarged excavating blade is attached to a head rod 1 ′ having an excavating blade at the lower end, and the diameter of the excavating blade is larger than the excavating diameter of the excavating blade from a closed position attached to the head rod. Using an enlargement head that is pivotally supported so as to be swingable and expandable to an open position, this enlargement head is connected to the lower end of the earth auger, for example, and a vertical hole is first drilled to the underground support layer by the earth auger, and then Expand the expanded excavation blade to the maximum excavation diameter and drill the required length in the support layer to excavate the cylindrical bulb expansion hole, then mix with the excavated sediment while injecting cement milk to form the soil cement, Next, a method of forming an enlarged bulb by inserting an existing pile into the vertical hole and press-fitting the lower end of the pile into the soil cement is widely known.

  As an expansion head used for this construction, an expansion blade is rotatably supported in the expansion / contraction direction on the outer periphery of a drilling blade at the lower end of a screw rod (not shown), and the surrounding earth pressure during excavation by the positive rotation of the screw rod The expansion wing is closed / contracted by this, but in the case of expansion excavation, a screw rod is rotated in the reverse direction to expand the expansion wing by the surrounding earth pressure (see Patent Document 1).

  However, in the above-described conventional head, the expansion blade expands to the maximum diameter at a time during reverse rotation, so an excessive excavation resistance is added to the rotation drive part, and the screw rod becomes unrotatable especially in the expansion excavation of hard ground. There were often things.

In order to improve this, a double-acting hydraulic cylinder is built in the head rod, and two oil flow paths that supply and discharge hydraulic pressure to the cylinder are vertically passed through the screw rod. Has been proposed (see Patent Document 2).
JP 2003-239669 A JP 2002-322890 A

  However, the method of Patent Document 2 has a problem that the apparatus is expensive and complicated.

  Therefore, the present invention has been made with the object of enabling an expansion blade to be expanded stepwise from a small diameter to a maximum diameter with a simple and inexpensive device without a special drive source such as hydraulic pressure. .

As a means for solving the above-mentioned problems, the present invention provides a step-by-step desired step on a guide plate that supports the magnifying wing of the reversing magnifying head slidably or swingably in the vertical direction and is fixed to the support of the magnifying wing. The apparatus has a configuration in which a slit for dividing and expanding is provided, and the guide plate is fitted on the expansion blade .

  In addition, using the forward / reverse rotational force of the screw rod, the vertical movement of the expansion head, and earth pressure, the expansion wing is gradually divided from the small diameter to the maximum diameter, and the bulb is formed at the lower end of the ground while sequentially expanding. And / or a method of constructing an intermediate expanded pile.

  According to the present invention, it is necessary to consider the operation procedure, but the expansion blades are not operated at a stretch from the reduced diameter to the maximum expanded excavation diameter with a simple structure, and the expansion blades are stepwise according to the number of divided expansion stages. Since the diameter is gradually expanded from the small diameter to the maximum diameter, the excavation resistance is excessive even on hard ground, and the screw rod does not become unrotatable.

  Other than the expansion head, conventional equipment may be used, and there is no need to pay special attention to initial cost and maintenance.

  The present invention will be described below with reference to embodiments shown in the drawings.

  FIG. 1 is a front view (1-1) and a bottom view (1-2) showing an embodiment of a reverse rotation enlargement head used for carrying out the present invention, and FIG. 2 is a plan view thereof. Is a cross-sectional view of the main part of the enlarged wing attached in the direction of arrow S in FIG. 1 ((3-1) is a sliding type, (3-2) and (3-3) are swinging types), FIG. FIG. 4 is an operation diagram illustrating a position state in which the divided expansion support portions 6 and 6 of the expansion blade are fitted to the guide plate 4 in which the three-stage split expansion slits 5 and 5 are formed. FIG. 5 is an operation diagram in the three-stage split expansion slit of the split expansion support portion of the expansion blade according to the operation procedure in FIG. 1, and FIG. 5 is a bulb generation process when the bulb is formed by the expansion head of FIG. It is sectional drawing which shows (D).

  First, the expansion blade mounting portion is of a sliding type ((3-1) in FIG. 3). This reverse expansion head 3 is connected to the lower end of a screw rod (not shown) of the earth auger. At the lower end of the head rod 2 having the excavating blade 7, brackets 13, 13 serving as enlarged wing support members are provided in a projecting manner at opposite positions in the diametrical direction. , 13 are mounted on the shafts 8 and 8 so as to be horizontally rotatable and slidable vertically.

  Next, the mounting portion of the expansion blade is of a sliding type configuration, but the configuration of the swing type I ((3-2) in FIG. 3) is a slidable sphere on both brackets 13 and 13. The support receivers 10 and 10 are provided, and the spherical expansion blades 1 and 1 mounting portions 9 and 9 each having a hollow hole drilled in a conical inverted cone in accordance with the inclination angle of the expansion blades 1 and 1 are shafts 8. , 8 are swingably supported, and the others are the same as the above sliding type.

  In the configuration of the swing type II ((3-3) in FIG. 3), both brackets 13 and 13 are provided with spherical sliding support receivers 12 and 12, and the spherical shape of the enlarged blades 1 and 1 is provided there. The attachment parts 11, 11 are swingably fitted, and the other parts are the same as those of the sliding type.

  A guide plate 4 having three-stage slits 5 and 5 is mounted on the outer periphery of the brackets 13 and 13 without any difference between the sliding type and the swinging type. 13 and 13 are fitted with the split expansion support portions 6 and 6 of the expansion blades 1 and 1 whose mounting portions are supported, and the tip portions of the expansion blades 1 and 1 protrude from the guide plate 4. .

  Next, the operation of the above embodiment will be described with reference to FIGS.

  First, at a predetermined pile construction position, the sliding type reverse rotation enlargement head 3 is connected to the lower end of the screw rod (not shown) of the earth auger, and the ground is excavated to the set depth while rotating the screw rod forward (see figure). 5 (I)) U. At this stage, the splitting and expanding support portions 6 and 6 of the expanding blades in the slits 5 and 5 are in a state where the expanding blades 1 and 1 are subjected to earth pressure from the horizontal direction. The closed position, that is, the right end of the divided expansion support portions 6 and 6 of the expansion blade is pressed against the wall a of the slits 5 and 5. The upper surfaces of the divided expansion support portions 6 and 6 of the expansion blades are pressed against the n surfaces of the slits 5 and 5 because the expansion blades 1 and 1 receive earth pressure from below in the vertical direction due to penetration of the expansion head 3. It becomes the state.

  Next, once the rotation is stopped, the first stage reverse rotation expansion excavation is performed by reverse rotation. At this time, since the reverse earth pressure is received from the horizontal direction, the expansion blades 1 and 1 are expanded in the first stage, that is, the left ends of the divided expansion support portions 6 and 6 of the expansion blades are b of the slits 5 and 5. Reach the wall. In this state (FIG. 4B), the expansion head 3 is pulled up to a predetermined height, whereby the first-stage expansion excavation (FIG. 5B) is performed. In addition, since the expansion blades 1 and 1 receive earth pressure from above in the vertical direction when the expansion head 3 is pulled up, the bottom surfaces of the split expansion support portions 6 and 6 of the expansion blade are pressed against the g surface of the slits 5 and 5. It becomes.

  When the first stage of expansion excavation is completed, the rotation is stopped and the expansion head 3 is pushed down to the position where it was first excavated. By doing so, the expanding blades 1 and 1 receive earth pressure from below in the vertical direction and move to a state where they are pressed against the h-plane of the slits 5 and 5 (FIG. 4C).

  In this manner, the second-stage reverse rotation expansion excavation is performed by rotating the reverse rotation again. At this time, since the reverse earth pressure is received from the horizontal direction, the expansion blades 1 and 1 are expanded in the first stage, that is, the left ends of the divided expansion support portions 6 and 6 of the expansion blades are d of the slits 5 and 5. Reach the wall. In this state ((D) in FIG. 4), the expansion head 3 is pulled up to a predetermined height, whereby the second-stage expansion excavation ((C) in FIG. 5) is performed. The bottom surfaces of the split expansion support portions 6 and 6 of the expansion blades are pressed against the i surface of the slits 5 and 5 because the expansion blades 1 and 1 receive earth pressure from above in the vertical direction when the expansion head 3 is pulled up. It becomes.

  Further, when the second stage of expansion excavation is completed, the rotation is stopped and the expansion head 3 is pushed down to the position where the excavation was first performed. By doing so, the expanding blades 1 and 1 receive earth pressure from below in the vertical direction and move to a state where they are pressed against the j plane of the slits 5 and 5 ((E) in FIG. 4).

  After that, the reverse rotation is performed again to perform the third-stage reverse expansion digging, and the excavation head is pulled up while discharging the chemical liquid such as cement milk (not shown) from the discharge port of the expansion head 3 via the chemical liquid passage. go. At this time, since the reverse earth pressure is received from the horizontal direction, the expansion blades 1 and 1 are expanded in the third stage, that is, the left ends of the divided expansion support portions 6 and 6 of the expansion blades are f of the slits 5 and 5. Reach the wall. In this state ((F) in FIG. 4), the expansion head 3 is pulled up to a predetermined height, whereby the third stage of expansion excavation ((D) in FIG. 5) is performed. In addition, since the expansion blades 1 and 1 receive earth pressure from above in the vertical direction when the expansion head 3 is pulled up, the bottom surfaces of the split expansion support portions 6 and 6 of the expansion blade are pressed against the k-plane of the slits 5 and 5. It becomes.

  When the bulb formation is completed by these procedures, once the reverse rotation is stopped and returned to the normal rotation, the expansion wings 1 and 1 are closed, the expansion head 3 is pulled up and recovered, and the existing pile is moved to the bulb. By inserting, it is possible to create a bulb-type pile by expanding the expanding blades 1 and 1 step by step using the forward / reverse rotational force and earth pressure of the screw rod.

  Here, the sliding type has been described. However, in the case of the swing type, as is clear from the structure (see (3-2) and (3-3) in FIG. 3), When the diameter is reduced and when it is fully expanded, it is not horizontal and is inclined, but the operation mode is substantially the same as that of the above-described sliding type.

  In order to create a bulb and intermediate expanded pile, after creating the bulb in the above procedure, the expansion head 3 is pulled up while rotating the screw rod forward, and the expansion blades 1 and 1 are closed and contracted by earth pressure. Then, when the enlargement head 3 is pulled up to a predetermined position, by performing the above procedure, it is possible to create a pile whose diameter has been expanded to a predetermined intermediate portion of the pile.

  Moreover, although the example which operates in three steps is shown in the present embodiment, it is needless to say that the present invention can be applied in the case of two or more steps.

  The front view (1-1) and bottom view (1-2) which show one Embodiment of the reversal expansion head in this invention.   FIG. 2 is a plan view for explaining expansion of an enlarged wing portion in FIG. 1.   FIG. 1 is a cross-sectional view of the main part of the enlarged wing attached in the direction of arrow S in FIG.   The operation | movement figure in the 3 step | paragraph division | segmentation expansion slit of the division | segmentation expansion | deployment support part of the expansion blade by the operation | movement procedure in FIG.   Sectional drawing ((I)-(D)) sectional drawing at the time of bulb creation with the expansion head of FIG.   The front view (6-1) and side view (6-2) of the reversal expansion head currently used conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 'Expansion wing 2,2' Head rod 3, 3 'Expansion head 4 Guide plate 5 Slit 6 Divided expansion support part 7 of a expansion wing 7, 7' Excavation blade 8 Axis 9 Attachment part 10 Spherical sliding support receiver 11 Mounting part 12 Spherical sliding support 13 Bracket a to n Slit end face

Claims (2)

The expansion blade provided on the upper outer periphery of the expansion head rod that has a drilling blade at the lower end closes the expansion blade by the surrounding earth pressure during forward rotation excavation, and expands the expansion blade by the surrounding earth pressure during reverse rotation In the reversing and expanding head, the expanding blade of the reversing and expanding head is slidable or swingable in the vertical direction, and is divided and expanded in a stepwise manner on a guide plate fixed to the supporting member of the expanding blade . A reversing enlargement head characterized in that a slit is provided and the guide plate is fitted on the enlargement blade . The expansion blade provided on the upper outer periphery of the expansion head rod that has a drilling blade at the lower end closes the expansion blade by the surrounding earth pressure during forward rotation excavation, and expands the expansion blade by the surrounding earth pressure during reverse rotation In the pile construction method using the reverse expansion head of claim 1 , the expansion blade is gradually increased from a small diameter to a maximum diameter by utilizing the forward / reverse rotational force of the screw rod, the vertical movement of the expansion head, and earth pressure. A method of creating a bulb or intermediate diameter expanded pile, wherein the pile is constructed while being expanded by a sequential division method of three or more stages .

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