JPH02225714A - Construction method of hollow bottom expansion cast-in-place ready-made concrete pile - Google Patents

Abstract

PURPOSE:To promote construction in pile work by inserting a double flexible tube from an opening to place concrete into a bottomed enlargement section, and making a hollow bottom expansion pile body by the up and down oscillation of the pile body. CONSTITUTION:A pile body 4 is connected to a bottomed enlargement section W at a pile connection R, a flexible tube 2 is inserted into the bottom of a pile hole H and, at the same time, the same volume of stable liquid 1 as that of the pile body 4 is pumped out to the outside of the excavated pile hole H with a pump 10 to place concrete 12 to the pile body 4. The pile body 4 is hung up by a crane to enlarge the bottomed enlargement section W, and the concrete 12 is discharged into the flexible tube 2. In addition, the pile body 4 is oscillated up and down 19 and 20, and the concrete 12 in the outside of the pile body is filled near to the head. According to this constitution, a cast-in- place pile can be constructed as a hollow bottom expansion pile, so that it can be a lightweight pile.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an improvement in the method of pouring ready-made concrete in hollow-bottomed areas, improving the bearing capacity of the tip of the pile, attenuating negative frixigins after construction, and improving the method of pouring concrete. The purpose of this project is to prevent the strength of concrete piles from decreasing in strength, to make the construction pile hollow, which increases the bearing capacity, and to improve the ease and reliability of construction in pile construction.

(Prior art) Various methods for driving so-called cast-in-place concrete piles with an expanded bottom have been developed and have they been put into practical use? The first is the bottom expansion reverse method, which uses water to hold the hole wall under a hydrostatic pressure of 0.2 Kg/Cm' and excavates without a casing, so it requires a rotary table. It rotates and circulates the earth excavated by a drill bit attached to the tip using a centrifugal pump or submersible pump, sucks up the earth and water, and discharges it out of the hole to create a water sump.
Drilling is carried out while circulating the water into the hole again, and the drilling of the expanded bottom part is carried out using the above method in combination with an expanded drill bit6.
It is.

The second well-known method is the expanded-bottom earth drill method.

I dig a pile hole while removing old soil with a drilling bucket,
If there is groundwater, the surface layer of the ground is protected with a guide casing, and the deeper part is excavated using a stabilizing liquid.Also, there is no groundwater and there is no risk of the hole wall collapsing. The upper ground was excavated by bare digging, and the expanded bottom part was excavated using an enlarged drill bit.

Conventionally, cast-in-place concrete piles have been constructed by pouring concrete into a poling hole excavated by a poling method such as L.

Or a ready-made pile body? In this case, the method of constructing the hollow expanded pile and the structure of the pile body have not been publicly known.

(Problems to be Solved by the Invention) However, in the case of using the above-mentioned conventional construction method, when concrete is poured into a hole, it is adversely affected by a large amount of groundwater.

In particular, in the two most common methods in which a stabilizing solution is used, concrete is poured in a stabilizing solution, so the formation of a viscous gel strength barrier and the pH are severely affected by the influence of both Ca ions and OH ions. give. In addition, salt in the stabilizing solution reduces the strength of the medium cross-sectional area of the cast concrete pile, making it necessary to increase the diameter of the pile by that amount, which is uneconomical and also causes quality deterioration. I can't escape it. In addition, if there is activity on the outer surface of a cast-in-place pile, there is a risk that the pile tip will collapse due to negative friction in the state where the pile tip is supported by the supporting ground. In addition, in the reverse construction method and the earth drill method, the pile side wall of the excavated pile hole is not completely retained, and when installing reinforcing bars and tremie pipes in the excavated pile hole in the supporting ground, the side wall of the pile hole collapses and earth and sand fall. It accumulates on the supporting ground, reducing the cross section of the pile tip and causing uneven settlement. Furthermore, in the Benotoé method, when the casing is pulled out or concrete is placed, a phenomenon of stiffening of the reinforcing bars occurs, which leads to a decrease in the strength of the pile tip in the supporting ground. Cast-in-place concrete piles are calculated by subtracting the dead weight W of the pile from the long-term bearing capacity na because the weight per pile is very heavy.

(Means for Solving the Problems) The present invention solves the problems in the above-mentioned prior art, and provides a ready-made product with a hollow expanded bottom that provides high strength and high bearing capacity, is economical, and is easy to construct. This led to the development of a construction method for concrete piles. Specifically, when constructing hollow-bottomed, cast-in-place ready-made concrete piles, an A-bottom with an a-bottom of a length equal to or longer than the pile length confirmed in advance by measuring the size of the pile is installed in the expanded-bottomed excavated pile hole. A double flexible tube with a flexible tube on the inside and a bottomless flexible tube on the outside is inserted so that the bottomed expanded section faces the bottom of the excavated pile hole, and concrete is poured into the bottomed expanded section to form the pile body. Concrete is cast while connecting the bottomed expanded part to the bottom of the expanded pile hole, and the shaft head 11 is struck and swung, and the tip of the pile body is installed in advance in the bottom entry part of the tr bottom. The mechanism expands the bottomed expansion part in a flexible tube separated from the bentonite liquid. The concrete inside the pile body can be separated from the outside by a float valve installed in advance inside the pile body in the bottomed expansion part, and the vertical movement of the pile body allows concrete to flow from the inside of the pile body to the outside of the pile body. This is a construction method and pile structure that makes it possible to construct a hollow, expanded-bottom cast-in-place concrete pile by using the pile body's own weight as flJ and pumping the concrete inside the pile body.

(Function) The double flexible tubes, one without a bottom and the other with a bottom, are folded into a bellows shape in advance, and are sequentially folded from the opening of the polling hole toward the bottom of the hole, with the bag-shaped bottom at the top. Charge it to While pouring concrete into the bottomed expanded part of the hollow expanded pile inside the flexible tube to be charged, connect the pile body and place concrete so that the pile body, which can become the pile body, faces the bottom of the hole. This is done alternately to expand the tip of the pile in the supporting ground at the bottom of the pile hole.
The float valve is opened and closed by swinging the pile body over L, and the concrete inside the pile body is pumped and filled to the outside of the pile body to construct a hollow expanded-bottom pile body.

(Example) Below, the specific contents of the present invention will be explained based on the embodiments of the drawings. It shows a vertical cross-section of the excavated pile hole.

FIG. 2 shows a cross section at arbitrary positions (bb to ``-'') of the excavated pile holes from [1] to (II) in the order of the driving process in FIG. 1.

Figure 3 shows a detailed explanation of the pile body 4 (D) to (F) in the order of the driving process in Figure 1 and the detailed description of the pile bodies 4 (i) to (D) to (F) in the order of the driving process in Figure 1.
(g), and detailed functions of the float valve Y, seal t) and concrete 12 due to the rocking I9.20 of the pile body A are shown in Figures (1) to (4).

Figure (h) shows concrete 12 after the pile construction process has been completed.
This shows the state in which the pile has hardened and the pile body has become a hollow concrete shaft.

In Figure 1, diagram (A) shows the pile hole I which was excavated by the earth drilling method, which is the most common method of drilling, while supplying stabilizing liquid. The vertical cross section of the casing is shown as a raindrop, and in this state it is filled with a stabilizing liquid 1, and a top casing 8 is installed at the open edge to prevent IJ≦ground collapse.

Figure (r3) shows that inside the top casing 8, there is an Arakagome γ
Insert the tube caning vibe 9 in which the flexible tube 2 with a bottom of 1° is recessed into the outer peripheral side in a bellows shape, and -
This shows that the bottom surface of the flexible duplexer 2 is on the top surface of the stabilizing liquid.

Figure (C) shows the bottomed enlarged fi < W of the flexible tube 2.
A bellows-shaped flexible tube is unraveled and charged toward the bottom of the trench through the mortar concrete 12, and the state in which mortar concrete 12 is being poured is not closed. At the same time, the pump 10
The figure shows a state in which a volume of stabilizing liquid f equivalent to the volume of the bottom part of f is pumped out of the excavated pile hole If. (D) in Figure 2
b-bi, t (r Pile body 4 incorporated in the main part W
12 is shown filled with mortar concrete 12.

Diagram (D) shows (-i) Pile body 4 is connected to forming ore large part W by anti-connection part R, and the flexible tube 2 is unraveled and charged to the supporting ground at the bottom of the pile hole i! At the same time, it is equivalent to pile body 4. The figure shows a state in which a volume of stabilizer 1 is pumped out of the excavated pile hole I (outside) by a pump IO, and concrete 12 is poured into the pile body 4.

(D) c to C in FIG. 2 show the internal structure of the bottomed enlarged part W, which is filled with concrete 12 and shows the state of the enlarged surface.

Figure (E) shows that the excavated pile length is connected to the piles whose length was measured in advance, concrete 12 with P constant 'd is poured inside the pile body 4, and the plunger 〇 to prevent mixing of the concrete and bentonite liquid is inserted into the concrete I2. ] After the pile body 4 is lifted by a crane or the like, it is gradually lowered toward the bottom 1 of the pile hole to enlarge the bulk part W of the a-forming ore and discharge the concrete 12 into the flexible tube 2. The liquid 1 is pushed up to the pile head via the flexible tube 2, and bentonite liquid having the same value as the concrete 12 discharged from the inside of the pile body is sent into the pile body by a pump 10 in order to pressurize the concrete inside the pile body. The pressurizer in this case can be fresh water or compressed air.

In Figure 2 (1) d-d, there is a stabilizing liquid I in the pile hole H and the flexible tube 2, and there is also a stabilizing liquid inside the pile body A! 4 indicates that it is filled.

Fig. 1(e) shows the function of the float valve Y and sole P installed inside the pile body 4. The float valve Y opens due to the swing 19 of the pile body 4, and the concrete I2 flows 4.
is discharged to the outside of the pile body due to the pressure difference.
Foot [1] The foot valve Y opens, and the seal P
2, the concrete is pushed in the direction of the swing 19 together with the pile body 4, and the concrete is pushed downward.

Figure (F) shows the pile body 4 being moved upward by a crane, etc.
The figure shows a state in which the filling of the concrete I2 to the outside of the pile body is promoted and the concrete 12 is filled up to the vicinity of the pile head.

Figure 1 () shows the function of the float valve Y and the float valve Y installed inside the pile body 4. When the pile body 4 moves upward, the float valve Y closes due to the upward swing 20, and when the pile body The concrete I2 discharged to the outside of pile body 4 is
i1, 4i bl of concrete 12 inside the pile body, and nail of bentonite liquid 1! By repeating rocking 19 and rocking 20 from the PnI of J1, the concrete 12 can be pushed up to the counter head, and the pile body - "concrete 12 or seal r depending on the sum of a" is pressed upward and bent. It shows that the concrete!2 is being pumped smoothly into the concrete.

In Figure (G), the tubular casing pipe 9 that had been joined to the 4-opening 1-1 part of the flexible tube 2 has been removed, and the tip of the pile has been expanded to 1.5 mm (the length of the resistance line of W). Then, after hitting the counter head and measuring the rebound to confirm the supporting capacity, the flexible tube 2 and the pile body 4 are cut at the joint position in order to make the support F\ 1'j people on the ground.

Figure (11) shows that after the concrete ■2 poured into the outside ffs of the pile body 4 becomes hardened concrete I4, the internal stabilizing liquid 1 is pumped out of the pile body 4 using a pump IO, and the head treatment is performed to form a casing. This shows iB pulling out Vibe 8 to complete the construction of a hollow-bottomed, cast-in-place concrete pile.

Fig. 2 (II) r -flirt° Bottom expansion part W Concrete 12 filled with ore is hardened concrete.
Therefore, there is no hardened concrete in one of the pile bodies 4, indicating the condition of a hollow expanded-bottom pile.

FIG. 3 (11) shows the outside of the existing ore 11 W filled with concrete 12 at the tip of the pile body 4, which is charged into the bentonite liquid 1 in the excavated pile bottom 11 via the flexible tube 2. Shows the shape of @.

Figure (+) shows the inside of the unexpanded state 4 of the expansion mechanism of the large part W of the T-forming ore.

Figure (e) shows the initial state in which the bottomed expansion 1w is opened by the tip of the pile body 4, and the concrete 12 flows out from the joint of the rectangular expansion mechanism (f). Concrete 12 is filled from the bottom, and bentonite liquid I is poured into the bottom of the pile hole 11 due to the difference in specific gravity.
i This shows that it is starting to be pushed up to the ground.

Figure (2) shows an expanding machine hl' for large part of white ore W using pile body 4.
Push lK' open and use it as an enlargement mechanism! This shows the state in which it has begun to open. It also shows that the float valve Y attached to the inside of the pile body 4 of the main part W of the ore is opened and the concrete 12 inside the pile body is discharged in the direction of the arrow. Closed by.

Figure (r) shows the state in which the large part of the ore W is opened by the tip of the pile body 4, and the state in which the bottom part of the part of the ore in which the part of the ore of f1<w is struck by the pile body 4 and penetrates together. This shows a state in which concrete I2 is subsequently filled and the bentonite liquid is pushed up.

Figure (3) shows that the bottomed expansion part W has been completely opened by the pile body 4 and the expansion has been completed (the bottom of the four-formed ore large part W and the pile body 4 have both been driven into the supporting ground for 9 hours). The state is shown. Also, at this time, the sole (■) is open in the concrete +2.

Figure (g) shows the state in which the pile body 4 has been raised to the height of α with the support ground still penetrated by 1 w. By spacing the concrete 12 vertically to a height of , filling of the concrete 12 between the pile body 4 and the flexible tube 2 is promoted smoothly.

Figure (4) shows one person on the supporting ground (J-Pull the pile body 4 to an arbitrary height with the bottom part W kept in a shell-sized state).
This shows the state in which the large ore section W remains enlarged, and due to the FE force difference between the inside of the pile body and the outside of the pile body) the a-to valve Y is opened, and the concrete I2 continues to connect with the pile body 4. It is filled between the flexible tubes 2. Also sole
) open in the concrete 12 to facilitate filling of the concrete.

Figure (h) shows that after the pile body A has been lowered, the concrete ■2 is filled up to the height of the outer circumference of the pile head of the pile body W and the pile body 4, and hardened concrete 14 is formed inside the pile body 4. indicates a hollow area, and the belt I attached to a predetermined position of the pile body 4
t indicates that by the impact of the pile body 4 (J), the large ore body W is fixed from the upper part to the supporting ground; A pile is constructed.A similar result can be obtained by using a screw-in type connection R between the upper and lower parts of the pile body 4, or by electric welding or the like to connect the pile bodies.

Furthermore, in the embodiment described in 11, a steel pipe was used for the pile body 4 when constructing the pile, but it is not necessarily limited to any material as long as it can be used as a pile body depending on the purpose.

(Effects of the Invention) The present invention provides a pile body in which a bottomed flexible tube is attached to an expanded bottomed pile hole via a bottomed flexible tube and a bottomed expanded portion is attached to the bottom of an expanded bottomed pile hole. When constructing a hollow-bottomed, cast-in-place concrete shaft, the bottomed expansion part is expanded in the support ground where the pile body is expanded and the concrete is cast into the inside of the pile body. Because the concrete is placed inside the pile body through the flexible tube at the bottom of the pile hole, there is no direct contact between the stabilizing liquid used when polling the excavated hole and the poured concrete. Because it is not affected by the stabilizing liquid, it has a much higher strength than underwater concrete piles made by the other two methods, and it is possible to thin the pile by half and use concrete, etc. In addition, by opening and closing the float valve installed inside the pile body in conjunction with the rocking of the pile body, it is possible to construct a hollow expanded pile even though it is a cast-in-place pile, so it is possible to construct a hollow expanded pile with the same diameter. Even compared to the pile, it becomes a very smooth pile.Also, if the flexible tube used is double layered with lana, which is a material with excellent surface smoothness, Figure 1 shows an embodiment of the present invention, which can attenuate the negative flexibility generated in hollow-bottomed local soil by 80%, and also prevent abrasion effects by adjusting the length of the flexible tube. Since it can be undulated, the ESM bearing capacity of the pile can be controlled.

Furthermore, during construction, sufficient bearing capacity is ensured as there will be no adverse effects from pressurized water in the ground F, and the expanded bottom section built on the support layer will be mechanically expanded, and the tip of the pile will become the bottomed expanded section. It is blocked by the bottom of the pile, allowing rebound to confirm the bearing capacity, and since the influence of slime at the bottom of the pile is extremely small, the bearing capacity of the pile as designed is ensured even though it is difficult to use cast-in-place piles, and uneven settlement is prevented by +1. - It is very useful.

[Brief explanation of the drawing]

FIG. 2 is a vertical cross-sectional view showing the construction method of a cast concrete pile in the order of construction. FIG. 2 is an enlarged cross-sectional view of each section in FIG. 1. FIG. 3 is a cross-sectional view showing the movement of concrete in the expanded bottomed part and flexible tube in FIG. 1. ~ Expanded bottom part 111 anti-six 2 ~ Stabilizing liquid ~ Flexible tube (2 It) ~ Reinforcing bar 4 ~! 4 pipes ~ Top caning vipe ~ Duplex casing vibe ~ Pump ~ Concrete hardened concrete (F bottom-in large blunt shaft - Up in the swinging direction of the connection part of the pile body) Invention of motion direction and Fu Sato

Claims (12)

[Claims] (1) When constructing a hollow expanded pile in an expanded bottom excavated pile hole, the expanded bottomed part of the pile body that will become the expanded bottom pile is inserted into the excavated pile hole via a bottomless flexible tube and a bottomed flexible tube. A construction method for hollow, expanded-bottom ready-cast concrete piles in which concrete is poured into the interior of the pile body. (2) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, after charging two layers of bottomless flexible tubes and bottomed flexible tubes into the excavated pile hole, insert the bottomed expanded pile into the bottomed flexible tube. The method for constructing a hollow, expanded-bottom, ready-cast concrete pile according to claim 1, wherein the concrete is poured after the bottomed expanded portion of the pile body and the pile body are charged toward the bottom of the expanded-bottomed excavation. (3) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, a bottomless flexible tube and a bottomed flexible tube are stacked in advance in the excavated pile hole, and the bottomed expanded portion of the expanded-bottomed pile is inside the bottomed flexible tube. The hollow expanded-bottom ready-cast concrete pile according to claim (1), wherein the flexible tube and the pile body are sequentially charged toward the bottom of the excavated pile hole while pouring concrete into the pile body. Construction method. (4) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, a bottomless flexible tube and a bottomed flexible tube are stacked in advance in the excavated pile hole, and the bottomed expanded portion is connected to the bottomed expanded portion through the bottomed flexible tube. In order to charge the pile body toward the bottom of the excavated pile, and to make it easier to fill the concrete with high fluidity up to the expanded bottomed part of the pile and the top of the outer periphery of the pile body, multiple A claim in which a moldable flexible seal is installed to allow the pile body to move up and down between the pile hole and the pile body, thereby pushing up concrete to the pile head, so that concrete can be poured smoothly around the outer periphery of the pile body. (1) Construction method for hollow expanded-spot ready-cast concrete piles. (5) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, after inserting the expanded bottomed part of the pile body that will become the expanded-bottomed pile into the excavated pile hole via a bottomless flexible tube and a bottomed flexible tube. , concrete is poured into the bottomed expansion part and the pile body, and an expansion mechanism is installed inside the bottomed expansion part to mechanically expand the bottomed expansion pile tip by the pile body, and the expansion mechanism is installed inside the bottomed expansion part, and the expansion mechanism is installed in all directions toward the outer periphery of the pile body at the pile tip. The method for constructing a hollow, bottom-expanding, cast-in-place ready-made concrete pile according to claim (1), wherein the expanding mechanism itself is a pile structure. (6) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, the expanded bottomed part of the pile body that will become the expanded-bottomed pile is inserted into the excavated pile bottom through a bottomless flexible tube and a bottomed flexible tube. Concrete is placed inside the pile body, and the bottomed expanding part at the tip of the pile is expanded in the bottomed flexible tube by the swinging pressure of the pile body.
Concrete placed inside the pile body opens at the bottomed expanded section in the expanded bottom excavation section, where the strip-shaped joint is opened, and highly fluid concrete is discharged from the expanded joint, resulting in concrete 2.3. Due to the difference in specific gravity between the bentonite liquid and the bentonite liquid (1.1), the bentonite liquid is pushed up and concrete is filled from the bottom of the excavated pile, and by replenishing the concrete inside the pile body, the concrete is filled up to the top of the outer periphery of the pile body in the excavated pile hole. A method for constructing a hollow, expanded-bottom, cast-in-place concrete pile according to claim (1). (7) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, the expanded bottomed part of the pile body that will become the expanded-bottomed pile is inserted into the excavated pile hole via a bottomless flexible tube and a bottomed flexible tube. After charging toward the bottom and discharging the concrete previously placed inside the pile body from the enlarged part and filling it into the excavated hole, the pile body is inserted into the pile hole in order to take rebound in order to check the bearing capacity of the pile body. The hollow expanded-bottom cast-in-place ready-made concrete pile according to claim (1), wherein the slime remaining at the bottom of the pile hole is thickened at the bottom of the bottomed expansion part by using the force of impact toward the bottom. construction method. (8) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, direct the expanded bottomed part of the pile body that will become the expanded-bottomed pile toward the bottom of the excavation through the bottomless flexible tube and the bottomed flexible tube in the excavated hole. Concrete is placed during charging, the bottomed expansion part of the expanded bottom pile is expanded, and highly fluid concrete is discharged into the bottomed flexible tube.Due to the difference in specific gravity between the concrete and bentonite liquid, the flexible tube is released from the bottom of the pile. 2. The method for constructing a hollow, expanded-bottom, cast-in-place concrete pile according to claim 1, wherein the concrete and the bentonite liquid are not brought into direct contact with each other at that time. (9) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, the expanded bottomed part of the pile body that will become the expanded-bottomed pile is inserted into the excavated hole via a bottomless flexible tube and a bottomed flexible tube to the bottom of the excavated hole. Concrete is cast while charging to the bottom of the pile hole, and the expanded bottomed part is expanded by the pressure of the pile body, and the bottom of the expanded bottomed part and the supporting surface of the tip of the pile body are integrated at the bottom of the expanded bottom excavated pile hole. Therefore, when performing rebound to confirm bearing capacity, the tip of the pile is closed (claim 1).
) Construction method for hollow-bottomed, cast-in-place concrete piles. (10) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, insert the expanded bottomed part of the pile body that will become the expanded-bottomed pile into the excavated pile hole via a bottomless flexible tube and a bottomed flexible tube. Concrete is placed while charging toward the bottom, and after expanding the bottomed expansion part with the pile body at the bottom of the pile hole, the concrete is poured smoothly between the entire bottomed expansion part, the flexible tube on the outer periphery of the pile body, and the pile body. 2. The method for constructing a hollow, expanded-bottom, cast-in-place concrete pile according to claim (1), wherein the pile body is moved up and down at an arbitrary height within the enlarged portion of the expanded-bottomed pile so that the concrete can be filled with concrete. (11) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, the expanded bottomed part of the pile body that will become the expanded-bottomed pile is inserted into the excavated pile hole via a bottomless flexible tube and a bottomed flexible tube to the bottom of the excavated pile hole. Concrete is placed while charging toward By adjusting the flexible tube from two layers to one, it is possible to anticipate the frictional force around the pile body.In calculating the long-term bearing capacity of the pile, the tip of the expanded bottom pile has the bearing capacity as a driven pile, and the area around the pile body is a friction pile. The method for constructing a hollow, expanded-bottom, cast-in-place concrete pile according to claim (1), which can be expected to have a supporting capacity as high as possible. (12) When constructing a hollow expanded pile in an expanded-bottomed excavated pile hole, after inserting the pile body into the excavated pile hole through a bottomless flexible tube and a bottomed flexible tube toward the bottom of the excavated pile, the flexible tube The bottomed expansion part expands inside the pile, and the concrete ejected from it is blocked by the float valve installed inside the pile body in advance due to the rocking of the pile body, and is poured into the pile body. Fill the space between the flexible tube and the pile with concrete based on the difference in specific gravity between the concrete and bentonite liquid, and open and close the float valve by vertically swinging the pile to fill the concrete between the flexible tube and the pile in the ground of the excavated pile hole. The inside of the pile is hollow, which reduces the weight of the pile and saves on concrete.The flexible tube and concrete protect the outer periphery of the pile, preventing corrosion of the pile. The method for constructing a hollow, expanded-bottom cast-in-place ready-made concrete pile according to claim (1), which prevents.