JPS6058335B2 - Pile tip treatment method in pile foundation construction - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pile foundation construction method, and in particular to a pile tip treatment that compresses or consolidates the slime deposited at the bottom of an excavation hole to create a pile bearing capacity equal to or greater than that of the ground at the bottom of the hole. Regarding the method.

without removing slime remaining at the bottom of the borehole.
There is a method of compressing or consolidating (hereinafter simply referred to as consolidating) the slime to obtain a desired ground supporting force under a desk (Japanese Patent Publication No. 55-50132).

The pile tip treatment method related to this construction method involves inserting a tubular body that will become a pile, with a shoe block removably attached to the tip, into an underground excavation hole filled with stabilizing liquid, and applying fluid pressure to the shoe block. Alternatively, the slime deposited on the bottom of the hole is compacted by applying a vertical load such as a striking force, and then a coagulable material is cast onto the shoe block below the tubular body. By the way, when a vertical load is applied to the shoe block by hydraulic pressure, a reaction force opposing the hydraulic pressure is directly applied to the tubular body.

That is, a hydraulic device including one or more jacks disposed inside the tubular body to apply hydraulic pressure to the shoe block is locked at the inner wall surface or the lower end of the tubular body, and the hydraulic device is When actuated, the jack that is in contact with the center or near the outer edge of the upper end surface of the shoe block extends, and uses the tubular body as a reaction force to move the shoe block downward from the tip of the tubular body. Therefore,
The magnitude of the hydraulic pressure must be within the range of the reaction force determined by the weight of the tubular body and the solidified material surrounding the tubular body or the mutual adhesion strength between the solidified material and the surrounding ground.

For this reason, the fluid pressure against the shoe block is limited, and it is not possible to further compact the slime, or the weight of the tubular body may be affected by the length of the tubular body or the size of the cross-sectional area of the tubular body. Another problem is that the adhesive strength does not guarantee the hydraulic pressure necessary to sufficiently compact the slime. Therefore, the present invention aims to solve the above-mentioned problems and to obtain even stronger ground support capacity. The pile tip processing method according to the present invention makes it possible to separate a shoe block consisting of multiple pieces at the tip of a tubular body that is to be a pile inserted into an underground excavation hole filled with stabilizing liquid when constructing a pile foundation. The plurality of jacks of the pressurizing device disposed inside the tubular body are sequentially operated, and one piece corresponding to each jack is sequentially lowered to further remove the entire slime deposited at the bottom of the borehole. It is characterized in that it is strongly compacted, and then a coagulable material is cast on the shoe block below the tubular body.

The features of the invention will become clearer from the following description of the illustrated embodiments.

First, a hole filled with a stable liquid such as mud is drilled underground using the mud drilling method, earth auger method, etc., and a tubular body with both ends open, such as a steel pipe or precast concrete pipe, to be used as a pile is inserted into the hole. Insert.

A shoe block consisting of a plurality of pieces is separably attached to the distal end of the tubular body before the insertion,
The planar shape of the shoe block and the cross-sectional shape of the tubular body may be rectangular or other shapes in addition to the circular shape described later. As shown in FIG. 1, a cylindrical shoe block 18 made up of a plurality of pieces 16 is disposed below the tip 14 of the tubular body 12 in the hole 10.

As shown in FIG. 2, each piece 16 is obtained by dividing a shoe block 18 having a circular plane into three parts at equal angles on the plane, and cutting the shoe block 18 in the thickness direction of the shoe block 18. Sometimes the plane is a fan. It can be constructed with three-dimensional shapes. Each of the pieces 16 constituting the shoe block 18 is suspended from a cap 22 attached to the tip 14 of the tubular body 12 via a suspension means such as a steel wire 20, and each piece 16 is made of steel. They are bound together by one tie such as a strip 24.

Further, a guide tube 2 is liquid-tightly welded to the outer periphery of the tubular body 12 near the tip 14, that is, to the outer surface of the cap 22.
6 extends below the distal end 14 of the tubular body 12 and surrounds part or all of the shoe block 18. The steel strip 24 and the guide tube 26 are in liquid-tight contact. After the tubular body 12 is inserted into the hole 10 in the above-described state, a pressurizing device 30 is provided for lowering the shoe block 18 and consolidating the slime 28 deposited at the bottom of the hole 10.
is inserted into the tubular body 12, but in order to lower the shoe block 18 in the vertical direction and increase the reaction force, pressure is applied into the tubular body 12 as shown in FIGS. 1 to 3. Prior to insertion of device 30 or actuation of pressurizing device 30, it is desirable to solidify some or all of the stabilizing liquid surrounding tubular body 12 to form solidified material 32. When solidifying the stabilizing liquid, a solidifying agent is added to the stabilizing liquid in the hole 10 and mixed and stirred, or alternatively, the stabilizing liquid is sent from the hole 10 to a solidifying agent kneading plant (not shown) on the ground. Here, it is possible to solidify the stabilizing liquid by mixing and stirring the stabilizing liquid and the solidifying agent and returning it to the hole 10 again.Also, the solidifying agent is mixed with the stabilizing liquid in the hole 10. Alternatively, it is also possible to use a stabilizing liquid mixed with a solidifying agent in advance.After forming the solidified material 32, the piece 1
6 and a plurality of jacks 34 corresponding to each piece 16.
Insert inside.

Insertion of the pressure device 30 into the tubular body 12 is accomplished by inserting the pressure device 30 into the tubular body 12 via a wire 36 connected to a suitable suspension device (not shown) and extending through the interior of the tubular body 12. It can be carried out by hanging.

Furthermore, the pressurizing device 30 is engaged with the tubular body 12 and fixed at a predetermined position inside the tubular body 12 . The appropriate predetermined position is a position where the tip of the jack 34 contacts the upper end surface of the piece 16, but preferably the center of gravity of each piece is such that each jack 34 contacts each piece 16 in a corresponding manner. make them contact each other so that they are on the vertical line. The pressurizing device 30 is engaged with the tubular body 12 by a plurality of other jacks 3 that can extend in a direction perpendicular to the extending direction of the jack 34.
8 toward the inner wall surface of the tubular body 12.

In the illustrated example, the jack 38 is provided with an arc-shaped pressing plate 40 at its tip, and the pressing plate 40 is attached to the jack 38.
When the pressure device 8 is extended, it is frictionally engaged with the inner wall surface of the tubular body 12, and the pressurizing device 30 is fixedly installed inside the tubular body 12. After the pressurizing device 30 is installed in the tubular body 12 as described above, the shoe block 18 is lowered by sequentially operating each jack 34 to press each piece 16 in the vertical direction. Although each jack 34 can be operated by electromagnetic force, it is economical and
Considering the output, etc., it is preferable to use hydraulic pressure, and FIG. 1 shows an example using hydraulic pressure.

Further, for the same reason, the operation of the jack 38 is also based on hydraulic pressure. In the illustrated example, pressure fluid is supplied to each jack 34 from a hydraulic pressure source (not shown) installed on the ground via a hose 42 extending inside the tubular body 12 . Pressure fluid is supplied to the jack 38 from the hydraulic pressure source via a hose 44 separately from the jack 34. In order to operate each jack 34 in sequence, for example, the same number of solenoid valves (not shown) as the jacks 34 are arranged between each jack 34 and the hose 42, and the solenoid valves are sequentially opened and closed. This can be done by supplying pressurized fluid to each jack 34.

The solenoid valve is electrically connected to a control device (not shown) installed on the ground via an electric wire 46 extending inside the tubular body 12. Alternatively, the jacks 34 can be operated in sequence by sequentially supplying pressure fluid to each jack 34 through a plurality of hoses (not shown) connected to each jack 34, without using the solenoid valve. be able to. When a vertical pressing force is applied to each piece 16 as described above, the steel wire 20 suspending the piece 16 breaks, and each piece 16 descends along the other pieces 16 and the strip 24. , the slime 28 deposited at the bottom of the hole, that is, below the tubular body 12, is consolidated. As mentioned above, the magnitude of the pressing force on the shoe block when consolidating the slime through the shoe block cannot exceed the upper limit of the allowable reaction force, but the shoe block in this example 18 consists of three equally divided pieces 16, and the pressing force is applied to each piece 16 sequentially, so compared to the case where an undivided shoe block is pressed all at once, the shoe block 18 is Similar results can be obtained if approximately three times as much pressing force is applied. In addition, when consolidating slime, please refer to Figures 4 and 5.
The shoe block can be lowered by the following method, which will be explained based on the drawings.

In the illustrated example, the cylindrical shoe block 18a is a cylindrical piece 16a obtained by drawing concentric circles on the plane of the shoe block 18a and cutting along the circumference in the thickness direction of the shoe block 18a. and an outer cylindrical piece 16b that remains after hollowing out the piece 16a, and each piece 16a, 16b is composed of the piece 16a, 1
It is suspended in the direction of the lower end surface of the tubular body 12 via a steel wire (not shown) that is cut when a vertical load is applied to the tubular body 6b. A pressurizing device 30a for applying a vertical load to the pieces 16a, 16b is a wire 36 extending through the inside of the tubular body 12.
A plurality of jacks 38 are suspended in the tubular body 12 via the pressurizing device 30a and extend to the sides thereof, and a press plate 40 attached to the tips of the jacks 38 is used to press a predetermined position inside the tubular body 12. Fixed.

The jack 38 is operated via a hose 49 that extends inside the tubular body 12 from a hydraulic pressure source (not shown) on the ground.
This can be done by supplying pressure liquid to 8. Further, the pressurizing device 30a includes a plurality of jacks 34a that extend vertically downward at the same time, and the jacks 34a are arranged at intervals, such that the upper end surface of each jack 34a, that is, the bottom of the cylinder 50, The upper end of the piston rod 52, which is the lower end surface of each jack 34a, is in contact with the upper end surface of the piece 16b. The jack 34a can be activated, for example, by alternately supplying pressurized fluid to both sides of the piston within the cylinder 50. In this case, hoses 51 and 53 extending from the hydraulic pressure source through the inside of the tubular body 12 are connected to the cylinder 50. Furthermore, an electric motor 56 connected to an electric wire 54 connected to a ground power source (not shown) is disposed inside the pressurizing device 30a, and a rotating shaft 58 of the motor 56 rotates as the motor 56 operates. A pinion 60 is fitted thereto.

An arm 62 having a rack that engages with a pinion 60 is disposed below the motor 56 in connection with the side of the cylinder 50 of the jack 34a, and the rotation of the pinion 60 moves the jack 34a to the position shown by the chain line in the figure. be able to. When the shoe block 18a is lowered by operating the pressurizing device 30a to compress the slime 28, first, pressurized liquid is supplied to each cylinder 50 via the hose 51 to extend each piston rod 52.

Each piston rod 52 applies the same pressing force to the piece 16b from each position on the upper end surface of the piece 16b, and lowers the piece 16b along the guide tube 48. Next, after the piston rod 52 is pulled up to its original position by supplying pressure fluid through the hose 53, the jack 34a is moved to the chain line position in the figure by operating the motor 56.

The moved jack 34a has a stepped portion 64 formed in which the top of the piston rod 52 is formed on the top end surface of the center piece 16a, and the bottom of the cylinder 50 is formed near the bottom of the pressurizing device 30a.
are placed in a state where they are in contact with or can be brought into contact with each other. After completing the movement of the jack 34a as described above, pressurized fluid is again supplied to the cylinder 50 via the hose 51 to extend the piston rod 52.

As the piston rod 52 extends, the central piece 16a descends, consolidating the slime 28. Note that the center piece 16a may be lowered first, and then the piece 16b may be lowered. In this example as well, it is possible to apply a pressing force close to the allowable limit to each piece 16a, 16b, so when the entire shoe block 18a is lowered at once to consolidate the slime 28. Compared to this, the compaction density of the slime 28 can be greatly increased.

After consolidating the slime 28 as described above, the wire 3
6 upward to remove the pressurizing device from inside the tubular body 12.

Next, a coagulable material 64 such as concrete or mortar is placed on the shoe block that has descended below the tubular body 12 to connect the tubular body 12 and the shoe block (sixth
figure).

According to the present invention, since it is possible to sequentially apply the permissible pressing force that can be applied to the entire shoe block at once to each piece that makes up the shoe block, the compaction density of the slime caused by the shoe block can be greatly improved. It can be increased significantly.

As a result, it becomes possible to obtain strong ground bearing capacity from the saw layer under the pile. Further, according to the present invention, by dividing the shoe block into a plurality of pieces of appropriate size, the pressing force to be applied to the pieces can be freely selected.

Therefore, each piece can be lowered with the optimal pressing force to consolidate the slime according to the pile length and pile diameter.

[Brief explanation of drawings]

Fig. 1 is a partial vertical sectional view showing the pressurizing device inserted into the tubular body, Fig. 2 is a transverse sectional view taken along the line 2-2 in Fig. 1, and Fig. 3 is the same as that shown in Fig. 1. FIG. 4 is a partial longitudinal sectional view taken along the line 3-3 of FIG. 4, FIG. Line 5-
5 is a cross-sectional view taken along line 5, and FIG. 6 is a partial longitudinal sectional view showing the state in which the coagulable material is cast onto the shoe block below the tubular body. 10: underground excavation hole, 12: tubular body, 14: tip of tubular body, 16, 16a, 16b: piece, 18: shake block, 28: slime, 30, 30a: pressurizing device, 34
, 34a: Jacket, 64: Coagulable material.

Claims (1)

[Scope of Claims] 1. A tubular body inserted into an underground borehole filled with a stabilizing liquid, the tubular body having a shoe block consisting of a plurality of pieces separably attached to its tip. After inserting therein a pressurizing device comprising a plurality of jacks and engaging the pressurizing device with the tubular body such that each jack is disposed correspondingly to one of the pieces, the bottom of the hole is A pile tip in the construction of a pile foundation, comprising lowering each piece by actuating each jack in sequence to consolidate the accumulating slime, and then casting a coagulable material onto the shoe block below the tubular body. Processing method. 2. The method of claim 1, wherein the shoe block piece has a fan-shaped planar shape. 3. The method of claim 1, wherein the shoe block pieces include a central piece having a circular planar shape and an outer piece surrounding the central piece and having a ring-like planar shape.