JP2000096567A - Heat for enlarged foot-protection in inner excavation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a supporting force by providing a ring-shaped nozzle ejecting a gas in the same direction surrounding a liquid-jetting stream, at the periphery of a high pressure liquid jetting nozzle of the head. SOLUTION: A ring-shaped gas ejecting nozzle 8 is formed at the periphery of a high pressure liquid jetting nozzle 5 of a head 1 to communicate with a compressed air passage 11. A gas ejecting hole 4 is closed. In the settling process of the pile, compressed air which has been conventionally forced to eject through the ejecting hole 4 is forced to eject through the nozzle 8, and compressed air is ejected from the periphery of the nozzle 5 to form an air entraining layer at the periphery of the liquid jetting stream. The frictional energy loss around the liquid jetting stream is reduced and the collision force of the jetting stream increases and the diameter of a pedestal to be formed becomes large. Instead of this, a high pressure liquid jetting nozzle constituted of a plurality of openings positioned close to each other is disposed at the same level in the axial direction of the head or at a position having a level difference in the axial direction of the head, and the ring-shaped gas ejection nozzle is provided at the periphery. In this way, a long term supporting force of the pedestal foot-protection pile can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for expanding a borehole used in a pile excavation method in which a screw auger is inserted into a hollow portion of a precast concrete pile or a steel pipe pile to excavate the ground and build the pile in the ground. It relates to a head for rooting.

[0002]

2. Description of the Related Art An excavating head for a deep excavation used in an excavation method (hereinafter referred to as a head) is constructed by excavating the ground with a cutting tool provided at the tip of the excavation ground, and building a pile into the ground. In this case, expanded bulbs are formed in the underground support layer to increase the bearing capacity of the pile. The inside digging method is highly evaluated as a technique for obtaining a large bearing capacity by allowing large-diameter piles to be laid smoothly under the ground without generating impact, vibration, and noise.

[0003] The head is provided with a gas ejection nozzle for blowing up the cut chips and earth and sand, and is provided with one or more high-pressure liquid ejection nozzles for ejecting a liquid such as cement milk in a radially outward direction. . Such a head for excavation and expansion of rocks in the ground is swung up and down while squirting high-pressure liquid in the ground below the lower end of the hollow pile, agitating the surrounding earth and sand, and forming an enlarged bulb larger than the diameter of the pile. Form. Such expanded bulbs greatly increase the bearing capacity of the pile.

Conventionally, the long-term bearing capacity P of a supporting pile is P = (1/3) (α × N × Ap) + R where α: bearing capacity coefficient N: N value of ground Ap: cross-sectional area of pile R : Stipulated to be calculated based on the pile bearing capacity. The bearing capacity coefficient α is a coefficient based on the method of expressing the bearing force at the tip of the pile, and is, for example, 30 for a driven pile, 25 for a bulb-consolidated pile, 20 for a cement milk method, and 15 for a cast-in-place pile. Stipulated.

[0005]

SUMMARY OF THE INVENTION The present invention makes it possible to increase the bearing capacity coefficient α in the long-term bearing capacity of the above-mentioned support pile by 20% or more, and to upgrade α from 25 to 30 in the excavated bulb root compaction pile. It has been newly developed to form a bulb as follows. It is an object of the present invention to increase the diameter of a bulb formed in the ground compared to the conventional art, and to increase the supporting force of a hollow piled-up bulb-filled pile.

That is, the object of the present invention is as follows.

(A) The diameter of an enlarged bulb is increased by improving the conventional head for excavating an excavated root.

(B) For this reason, the reaching distance of cement milk (spouting liquid) spouting at high pressure is extended.

(C) The extension of the reach of the cement milk (ejecting liquid) ejected at a high pressure can be obtained by increasing the ejection pressure of the ejected cement milk, but the equipment and the cost are inevitably increased. Basically, this is achieved by a conventional device with another contrivance.

[0010]

Means for Solving the Problems The present invention has been developed to solve the above-mentioned problems, and the technical means of the present invention is to provide a head used for a method of expanding and digging a pile in a pile, around a high-pressure liquid jet nozzle. And a ring-shaped gas ejection nozzle for surrounding the liquid ejection flow and ejecting gas in the same direction as the liquid ejection flow.

Conventionally, an excavated head for excavating a deep excavation has used auger screws to discharge the excavated earth and sand from the head during the settlement process of the pile, using an auger screw. Sending compressed air.

Further, the head is provided with a nozzle for jetting high-pressure liquid toward the outside in the radial direction in order to stir and sediment the earth and sand in the ground around the head and to form an enlarged bulb. This nozzle is 1-4 depending on the diameter of the pile.
It is a book. These are arranged radially at substantially uniform central angles.

A first feature of the present invention is that compressed air surrounding a liquid jet flow is jetted in parallel around a high-pressure liquid jet nozzle to reduce the energy loss due to friction of the liquid jet flow and to increase its reach. It is.

As described above, when the gas is supplied by providing the ring-shaped gas ejection port around the liquid ejection hole of the high-pressure liquid ejection nozzle, even if the gas pressure is lower than the pressure of the high-pressure ejection liquid,
Due to the Venturi principle, a high pressure liquid jet entrains gas around its periphery. By entraining the gas on the outer periphery of the liquid jet flow, the energy loss due to the jet of the jet liquid is remarkably reduced. This is considered to be because the frictional resistance of the outer peripheral portion of the flow of the ejected liquid was reduced. Therefore, the collision force of the liquid jet flow is increased, the earth and sand stirring distance is extended, and the diameter of the bulb can be increased.

According to a second aspect of the present invention, there is provided a head for use in a method for expanding a deep excavation of a pile, wherein the liquid jet nozzle is a nozzle having a plurality of adjacent openings. Head.

A second feature of the present invention is that the head is improved so as to have, as a high-pressure liquid ejection nozzle, an ejection nozzle provided with a plurality of openings which are close to each other in parallel. Such a jet nozzle is preferably applied to a large diameter pile having a pile diameter of 700 mm or more.

The plurality of liquid ejection openings provided in each high-pressure liquid ejection nozzle are arranged at the same level in the head axis direction, that is, on the same plane orthogonal to the head axis, or at a position where a slight step is provided in the head axis direction. It is preferable to arrange them. When a plurality of liquid ejection openings are arranged at a stepped position, the liquid ejection opening on the leading side in the rotation direction of the head when ejecting the liquid for the first time is located on the advancing side in the axial elevating direction of the head at that time. Is preferred.

This high-pressure liquid jet nozzle is provided with the first
The high-pressure liquid spouted from the liquid spouting opening stirs the earth and sand, and immediately after that, before the agitation portion settled by the preceding first liquid spouting opening settles down, the second liquid spouting opening forms the first liquid. Stir the earth and sand ahead of the stirring distance of the spout. Therefore, the distance for stirring the earth and sand is extended, and the diameter of the bulb can be enlarged.

According to the present invention, there is provided a technique of the first feature, in which a compressed air surrounding a liquid jet flow is jetted in parallel around a high-pressure liquid jet nozzle to thereby mainly provide a pile bulb having an outer diameter of 600 mmφ or less. Can be effectively applied to enlargement. In addition, the second feature of the present invention is to mainly increase the diameter of a bulb of a large diameter pile having an outer diameter of 700 mm or more by adopting a technical means in which a liquid ejection nozzle has a plurality of adjacent openings. it can. This 2
Due to the synergistic effect of the two technical means, the improvement of the bearing capacity of the large-diameter pile can be easily achieved irrespective of the geological conditions of the ground.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

First, a conventional head will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 8 is a front view of a head 1 provided with an auger screw, in which a screw blade 2 is helically mounted around a central axis 3, and a blade 6 is provided at a tip (lower end) of the head 1. FIG. 9 is a bottom view of FIG. 8, FIG. 10 is a longitudinal sectional view with the screw blades removed, and FIG. 11 is a bottom view thereof. Double tube 1 in the center of head 1
0 is inserted, and the low-pressure compressed gas passage 11 is connected to the gas ejection nozzle 4. The gas ejection nozzle 4 is used as an auxiliary means for discharging cutting chips and earth and sand cut by the blade 6 to the ground through the hollow portion of the pile. The high-pressure liquid jet nozzle 5 is connected to the liquid passage 12 of the double pipe 10 and jets a liquid such as cement milk into the earth and sand around the head 1 to crush and agitate the excavated material or rock excavated underground. This is then solidified to form a solidified bulb below the lower end of the pile. Conventionally, the liquid jet nozzle 5 is a single cylinder nozzle that jets liquid outward in the radial direction. FIG.
1 is a bottom view of the head 1 shown in FIG. 10, in which two high-pressure liquid ejection nozzles 5 are arranged radially at a substantially central angle of 180 ° and eject compressed air in a direction substantially orthogonal to this. A hole 4 is provided.

FIGS. 1 and 2 show a head 1 according to an embodiment of the present invention. FIG. 1 is a front view of the vicinity of the lower end of the head 1 of the embodiment, and FIG. 2 is a longitudinal sectional view thereof.

The head 1 of the embodiment shown in FIGS. 1 and 2 differs from the conventional head shown in FIGS. 8 to 11 in that a ring-shaped gas ejection nozzle 8 is provided around a high-pressure liquid ejection nozzle 5.
Is provided, the compressed gas passage 11 is connected to the ejection nozzle 8, and the gas ejection hole 4 is closed. In the pile sinking process, the compressed gas that has conventionally been ejected from the gas ejection holes 4 is ejected from the ring-shaped gas ejection nozzle 8. When compressed air is ejected from around the high-pressure liquid ejection nozzle, a gas entrainment layer is formed around the liquid ejection flow, and energy loss due to friction around the liquid ejection flow is reduced. In this case, the pressure of the gas may be low. As a result, the collision force of the liquid jet flow increases, and the diameter of the bulb to be formed can be increased.

3 and 4 show a head 1 according to a second embodiment of the present invention. FIG. 3 is a side view and FIG. 4 is a bottom view. The head 1 of the present invention shown in FIG.
Is different from the conventional head shown in FIG.
Are plural (two in FIG. 1) ejection openings 51, 52
It is a point provided with. Jet opening 5 of high-pressure liquid jet nozzle 5
The heads 1 and 52 may be arranged in a plane perpendicular to the axis of the head 1 or may be arranged adjacent to each other with a slight step in the axial direction of the head 1. In the example of FIG. 3, the latter is shown.

FIG. 5 is an explanatory view of the operation of the high-pressure liquid ejection nozzle shown in FIGS. 3 and 4, schematically showing a state during ejection of the high-pressure liquid. The head 1 rotating in the head rotation direction 64 ejects the liquid from the first liquid ejection opening 51 of the high-pressure liquid ejection nozzle 5 onto the wall surface 61 formed by the cutting tool 6 of the head 1 excavated and stirred. The liquid stirs up to the arrival surface 62, and immediately thereafter, the second liquid ejection opening 52
The liquid ejected from the liquid stirs up to the reaching surface 63. FIGS. 6 and 7 show a case in which a ring-shaped gas ejection nozzle 8 surrounding a high-pressure liquid ejection nozzle having a plurality of ejection openings 51 and 52 is provided. The gas passage 11 is opened on the side wall of the liquid ejection nozzle. The ejected liquid entrains gas around it,
It can reduce the loss of squirting energy, prolong the reach of the squirting liquid, increase the diameter of the expanded bulb, and increase the bearing capacity of the pile.

FIG. 12 and FIG. 13 show process charts of an embodiment of forming an enlarged bulb using the head of the present invention. An auger is inserted into the pile 100 on the ground by a pile standing device. As shown in FIG. 12A, the pile 100
In step 1, the ground 102 at the lower end of the pile is excavated, and the pile is settled while supplying compressed air to discharge the excavated earth and sand through the hollow pile with an auger screw. As shown in FIG. 12 (b), when the head 101 reaches the lower end of the bulb formation ground, the head 101 is moved to the formation 1 as indicated by an arrow 104.
12 is raised while stirring, and then, as shown in FIG. 12C, the head 101 is lowered in the direction of the arrow 106 while ejecting high-pressure liquid to expand the bulb forming part 105.
Next, as shown in FIG.
The head 101 is raised as shown by the upward arrow 108 while ejecting the nozzle 7, and the bulb 109 is formed as it is in FIG.
As shown in (a), ascending the pile, when reaching a predetermined height, for example, a height level 110 of 3 to 4 times the length of the bulb, stops the ejection of cement milk, raises the head as it is, and finally lifts the head. The head is pulled out as shown in FIG. 13C, and the construction of the pile with the enlarged bulb 109 is completed.

When an enlarged bulb is formed by using the head of the present invention, a bulb having a diameter of about 1.4 to 2 times the diameter of the conventional one can be formed, and the bearing capacity of the pile can be greatly improved. Can be.

Next, a basic test of the performance of the head of the present invention will be described. This basic test is a test for confirming a change in the injection pressure when only the high-pressure liquid is jetted and a change in the jet pressure when an air layer is formed around the jet of the high-pressure liquid. FIG.
Is a plan view of the basic test apparatus, and FIG. 15 is an elevation view thereof.
Width 1800mm x length 3000mm x depth 1650mm
A water tank 120 was prepared, a support table 122 was erected therein, and a pressure gauge 123 was attached to a side surface of the support table 122. The pressure gauge 123 used a load cell, and had a capacity of 20 kgf / cm ² per surface area.

On the other hand, two guide frames 124 are passed over the upper surface of the water tank 120 so that the head 131 can be moved along the guide frames 124, and the nozzles 132 of the head 131 are arranged so as to face the pressure gauge 123. . The nozzle 132 was a Laval nozzle having a diameter of 3 mmφ. While changing the distance between the nozzle 132 and the pressure gauge 123 by measuring it with a scale 125, the high-pressure liquid was jetted from the nozzle 132, and the pressure exerted by the jet jet on the pressure gauge 123 was measured. The test is performed on two levels, that is, when the water tank 120 is filled with water and when the atmosphere is in the atmosphere, and when the nozzle 132 ejects the high-pressure liquid alone and supplies air around the high-pressure liquid. Was. The case where water was used as the high-pressure liquid and the case where cement milk was used were implemented. Details of these test conditions are shown in Table 1.

The pressure of the air is 10 to 13 kgf / cm ²
(Standard 10 gf / cm ² ) and the amount of air is 3.5 Nm ³
/ Min or more (standard 5 Nm ³ / min). The diameter of the air ejection nozzle was 50 mmφ. The cement milk was a slurry having a water cement ratio of 70%.

The pressure is measured with a response frequency range of DC-5k.
Hz dynamic response measuring instrument and the response frequency range is DC-1.
25kHz, tape speed 2.28cm / sec, data recorder with 14 channels, response frequency range is DC-
It was measured by an electromagnetic oscillograph having 1 kHz and 12 channels, and was stored in a computer through a low-pass filter having a cutoff frequency of 100 Hz to 10 kHz.

These data were analyzed and the results are shown in Table 2.
4 and FIGS. 16 to 18. FIG. 16 corresponds to Table 2; 1-1, No. 1; 1-2, N
o. Data for 1-3 (in water, ejected liquid without air). FIG. 17 corresponds to Table 3; 1-4, No. No. 1-5, No. 1; 1
-6, no. Data for 1-7 (in water, ejected liquid with air). FIG. 18 corresponds to Table 4; 2-1, No. 2; 2-2, N
o. Data for 2-3 (spout in air).

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

From these results, it can be seen that the pressure drop in the atmosphere is small regardless of the distance, and that the pressure in the water at the same distance is not affected when the ejected liquid accompanies the air or when the air is not entrained. Was found to be 3 to 4 times.

Next, the actual model test of the present invention will be described.

Two vertical holes having a length of 6 m, a width of 6 m and a depth of 6 m were excavated from the ground surface. The excavated stratum was mainly shale containing some gravels. The first vertical hole is filled with earth and sand mainly composed of conglomerate soil, and the second vertical hole is stacked with compaction by compacting and compacting the sand about every 30 cm in thickness. A second artificial ground was created. A penetration test of the artificial ground thus formed was performed. In the penetration test, the first vertical hole was subjected to a boring-type standard penetration test, and the second vertical hole was performed using a Swedish sounding apparatus. The results of the penetration test are as shown in Tables 5 and 6.

[0040]

[Table 5]

[0041]

[Table 6]

Next, a prestressed concrete pile having an outer diameter of 600 mm was attached to the head shown in FIG.
Using a 0 mm spiral auger, it was submerged in the first and second artificial grounds by the inside digging method, and bulbs were formed on the pile bottom continuously.

In the process of lowering the head by lowering the head, water is used at a pressure of 100 kg / cm ² , the number of rotations of the head is 20 times / min, and the lowering speed is 50 cm / min.
Was performed under the following conditions. Next, in the lifting process,
Pressure 200 kg / cm ² in artificial ground, erupted cement milk at a pressure 180 kg / cm ² in the second artificial ground. At this time, the conditions were the same: the number of rotations of the head was 6 times / min, the pulling speed was 8 cm / min, and the amount of the ejected cement milk was 90 L / min. At this time, the pressure of the compressed air was 10 kgf / cm ² and the flow rate was 5 Nm ³ / min.

After the formation of the bulbs, the first and second artificial grounds were dug up, and the enlarged bulbs were dug out to measure the dimensions. The dimensions of the bulb are about 1 m in height and 1.5 mφ in average diameter (conventionally about 1.1 m) in the first artificial ground (concrete layer), and about 1 m in height and 2 mφ in average diameter in the second artificial ground. (Conventional about 1.0
m). Thus, according to the head of the present invention,
An enlarged bulb having a diameter of 1.4 to 2 times as large as that of a conventional enlarged bulb can be formed, and the cross-sectional area of the bulb becomes 2 to 4 times, and the supporting force is greatly increased.

[0045]

According to the present invention, it is possible to increase the diameter of the bulb by the deep excavation method to increase the bearing capacity of the pile and to improve the long-term bearing capacity. .

[Brief description of the drawings]

FIG. 1 is a front view of a head according to an embodiment.

FIG. 2 is a longitudinal sectional view of a head according to the embodiment.

FIG. 3 is a side view of the head of the embodiment.

FIG. 4 is a bottom view of FIG. 3;

FIG. 5 is an operation explanatory view of the embodiment.

FIG. 6 is a view showing a nozzle having a plurality of ejection openings.

FIG. 7 is a longitudinal sectional view of FIG.

FIG. 8 is a front view of a conventional head.

FIG. 9 is a bottom view of FIG.

FIG. 10 is a longitudinal sectional view of FIG.

FIG. 11 is a bottom view of FIG. 8;

FIG. 12 is a process chart of an enlarged bulb formation.

FIG. 13 is a process diagram of the creation of an enlarged bulb.

FIG. 14 is a plan view of a test water tank.

FIG. 15 is an elevation view of a test water tank.

FIG. 16 is a graph showing a relationship between a nozzle position of ejected liquid and a pressure.

FIG. 17 is a graph showing a relationship between a nozzle position of ejected liquid and a pressure.

FIG. 18 is a graph showing a relationship between a nozzle position of ejected liquid and a pressure.

[Explanation of symbols]

 Reference Signs List 1 head 2 screw blade 3 central axis 4 gas ejection nozzle 5 liquid ejection nozzle 6 blade 10 double pipe 11 gas passage 12 liquid passage 41 gas ejection nozzle on / off valve 42 valve opening / closing device 43 gas communication unit 44 gas communication unit opening / closing device 51 52 liquid ejection opening 61 wall surface excavated by a cutting tool 62 arrival surface from first liquid ejection opening 63 arrival surface from second liquid ejection opening 64 head rotation direction 100 pile 101 head 102 ground 103 formation stratum 104 arrow 105 bulb formation Part 106 arrow 107 cement milk 108 arrow 109 bulb 110 height level 120 water tank 121 inside 122 support stand 123 pressure gauge 124 guide frame 125 scale 131 head 132 nozzle

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 591197699 Japan High Pressure Concrete Co., Ltd. 3-8-3 Minami 2-Jo Nishi, Chuo-ku, Sapporo, Hokkaido (71) Applicant 000229667 Japan Hume Tube Co., Ltd. 5-33, Shimbashi, Minato-ku, Tokyo No. 11 (71) Applicant 000201504 Maeda Seisakusho Co., Ltd. 6-7, Uehonmachi, Sakata-shi, Yamagata (71) Applicant 593096561 Max Concrete Co., Ltd. 2-19-6, Yanagibashi, Taito-ku, Tokyo (71) Applicant 593096572 Yamazaki Pile Co., Ltd. 5-15 Minamiasuno-cho, Suwon-cho, Kitakanbara-gun, Niigata (71) Applicant 396014393 Marunouchi Concrete Industry Co., Ltd. Waki Co., Ltd. 2-4-9 Nihonbashi Kayabacho, Chuo-ku, Tokyo (72) Inventor Masao Katsuragi Tokyo 2-35, Aobacho, Higashimurayama-shi (72) Inventor Tadashi Takiguchi 6-5-26-Kurihara, Niiza-shi, Saitama (72) Inventor Morihiko Yamazaki 2- 10-14 Ryogoku, Sumida-ku, Tokyo Daido Concrete Industry Co., Ltd. (72) Inventor Satoru Yamada 1-400-4, Yoshino-cho, Omiya-shi, Saitama Prefecture (72) Inventor Kazuyoshi 5-7-17 Yanagizaki, Kawaguchi-shi, Saitama Prefecture (72) Inventor Masaaki Tada Suehiro, Yamagata-shi, Yamagata Prefecture No. 3-14, Town (72) Inventor Atsuhiro Yamashita 5-10-9, Shimoishikami, Nerima-ku, Tokyo (72) Inventor Tatsuya Abe 815 characters, Allimura, Nishikanbara-gun, Niigata (72) Inventor Akihiko Komori Nishi, Aichi 20-1 Ebisu-cho, Nishi-Biwajima-cho, Kasugai-gun Marunouchi Concrete Industry Co., Ltd. (72) Inventor Hiroyuki Egasu 1293, Adocho, Hanamigawa-ku, Chiba-shi 1293 Adocho, Hanamigawa-ku Sanwa Kiki Co., Ltd. Chiba Plant F term (reference) 2D050 AA03 AA06 BB04 CA02 C A05 CB03

Claims (4)

[Claims] 1. A head for use in a method of digging and enlarging a pile in a pile, wherein a ring-shaped gas ejection nozzle surrounding a high pressure liquid ejection nozzle and injecting gas in the same direction as the high pressure liquid ejection nozzle is provided around the high pressure liquid ejection nozzle. A head for expanding a deep digging root. 2. The excavating head according to claim 1, wherein the high-pressure liquid jet nozzle is a nozzle having a plurality of adjacent openings. 3. The head according to claim 2, wherein the plurality of adjacent openings are arranged at the same level in the head axis direction or at a position where a step is formed in the head axis direction. 4. A ring-shaped gas ejection nozzle which surrounds the plurality of openings and collectively surrounds the plurality of openings and injects gas in the same direction as the liquid ejection direction. A head for expanding a deep digging root.