CN108547288B - In-situ cast large tubular pile hole forming device inner valve and use method thereof - Google Patents

Abstract

The invention discloses a valve in a cast-in-situ large tubular pile hole forming device and a using method thereof, and the valve can be combined with a double-layer sleeve to form a pile mould of the cast-in-situ large tubular pile. The invention has the advantages that the stress of the mandrel is reduced; the defects of sealing failure, deformation or inclination of the large-diameter tubular pile hole forming device are greatly reduced, and the structural strength of the cast-in-place large tubular pile is improved; the service life of the pile mould is prolonged.

Description

In-situ cast large tubular pile hole forming device inner valve and use method thereof

Technical Field

The invention relates to the technical field of cast-in-situ large tubular piles, in particular to a valve in a cast-in-situ large tubular pile hole forming device and a using method thereof.

Background

The cast-in-place concrete large-diameter tubular pile, namely the PCC pile, sinks the steel inner and outer double-layer sleeve cavity structure into the designed depth of the foundation under the protection of the closed valve pile shoe in a vibration mode, concrete is uniformly injected into the cavity of the structure through the concrete flow divider, then the cavity structure is pulled out in a vibration mode, the valve pile shoe is automatically separated when the cavity structure is pulled out, and the concrete is injected into an annular groove formed after the cavity structure is pulled out, so that the cast-in-place concrete large-diameter tubular pile is formed. The PCC pile technology is a high-quality pile type technology with high efficiency and economy in the construction industry. The bearing capacity of the pile column can be improved by more than 50% by the PCC pile under the condition of the same concrete consumption, namely the same cross sectional area. The valve pile shoe in the prior art is usually fixed at the lower end of the outer pipe and is attached to the inner pipe, the guiding effect of the pile mould is mainly determined by the valve pile shoe, the traditional valve pile shoe is easily subjected to sealing failure, deformation or inclination of a cast-in-situ large-diameter pipe pile hole former when being extruded by the earth pressure, and the strength cast-in-situ quality of the large-diameter pipe pile is reduced.

For example, the patent of chinese patent document entitled "cast-in-place concrete large diameter tubular pile" with publication number CN205617361U and publication date 2016, 10, 5, discloses a cast-in-place concrete large diameter tubular pile, which comprises a pile body and a pile shoe, wherein the pile body is a hollow steel tube, an interlayer is arranged in the middle of the wall of the pile body, a concrete inlet is arranged above the wall of the pile body, a reinforcing steel layer is arranged inside the pile body, the pile shoe is circular, the pile shoe comprises a connecting part and an angle steel, the connecting part is arranged above the upper plane of the angle steel, the connecting part is cylindrical, the pile shoe is arranged below the interlayer of the pile body through the connecting part, a plurality of steel plates are uniformly arranged between the horizontal plane and the vertical plane of the angle steel, the steel plates are triangular, the lower part of the wall of the pile body is arranged on the upper plane of the angle steel, a filler bonding pile shoe is arranged below the interlayer, the utility model discloses simple structure, convenient to use sets up the angle steel, can reduce the impact force, and the protection pile head sets up the triangle-shaped steel sheet between the angle steel, and the hammering-in-process has reduced frictional resistance, and the penetrating power is strong, and the penetrating power is good, shortens the engineering time, and is with low costs, the live time is long. The cast-in-place pile has the disadvantages that the large-diameter tubular pile is driven into soil through angle steel, the pile shoe and the tubular pile are connected into a whole, a pile body cannot be taken out as one part of the tubular pile after concrete is poured, each tubular pile needs one pile body, and the cost of the cast-in-place large tubular pile is too high.

For another example, the chinese patent document entitled "construction method of cast-in-place reinforced concrete large-diameter tubular pile" with an authorization publication number of CN102296598B and a publication date of 2011, 12, and 28 discloses a construction method of cast-in-place reinforced concrete large-diameter tubular pile, which includes the following steps: the pile driver is in place; the movable inner support rotates to approach the limiter; the valve pile tip is closed; sinking the pile mould; removing the vibrating head; putting down a reinforcement cage; installing a vibrating head; pouring concrete; vibrating and drawing the tube; opening a valve pile tip and an inner support; concrete and a reinforcement cage enter the foundation; and pulling out the pile mould to form the pile. The movable inner supports and the limiting devices can be uniformly arranged along the pile mould by 3 or more than 3. Set up horizontal support bar on the steel reinforcement cage, its both ends set up semi-circular elbow, and set up 3 or more than 3 on every transverse section of steel reinforcement cage, set up a set of every 3 ~ 5m along vertical. The invention skillfully arranges the movable inner support and the reinforcement cage with the transverse support steel bar, effectively solves the problem of the construction of the reinforced concrete PCC pile, expands the application range of the PCC pile, has low manufacturing cost and obtains higher bearing capacity with less concrete consumption. The pile driving device has the disadvantages that the valve pile tip completes pile driving, the movable inner support supporting the inner pipe and the movable inner support of the outer pipe are connected with the inner pipe through the rotating shaft, when the pile is sunk into a pile mould, the pressure is born by the rotating shaft, the valve pile tip is easy to be distorted to cause the inclination of the pile mould, even the damage of the pile mould is easy to cause, the annular cavity is squeezed into mud to cause the reduction of the structural strength of the large-diameter pipe pile, and the use of the large-diameter pipe pile is influenced; the annular cavity of the pile mould is easy to feed mud, and the sealing property of the tubular pile is not enough.

Therefore, it is necessary to design a flap in the cast-in-situ large pipe pile hole forming device with high structural strength and good sealing strength to prolong the service life of the cast-in-situ large pipe pile hole forming device and improve the structural strength of the cast-in-situ large pipe pile.

Disclosure of Invention

The invention provides a valve in a cast-in-place large tubular pile pore-forming device and a using method thereof, aiming at improving the structural strength and the combined sealing performance of the valve in the cast-in-place large tubular pile and further improving the structural strength and the solidification efficiency of the cast-in-place concrete large-diameter tubular pile, aiming at overcoming the defects of insufficient structural strength and valve sealing performance of the existing cast-in-place large tubular pile valve.

In order to achieve the above object, the present invention adopts the following technical solutions.

A valve in a cast-in-situ large tubular pile hole forming device can be combined with a double-layer sleeve to form a pile mould of a cast-in-situ large tubular pile, the double-layer sleeve comprises an inner pipe and an outer pipe which is coaxial with the inner pipe, the inner valve comprises a plurality of valve units, the valve units are formed by cutting the same round table, the valve units are rotatably connected to the lower side of the inner pipe, wedge blocks for supporting the two adjacent valve units are arranged in the double-layer sleeve, the valve units and the wedge blocks are matched to form a hole forming round table, the hole forming round table is positioned in the outer pipe, the valve units can be lapped with the inner side surface of the outer pipe, a supporting component is arranged between each valve unit and the outer pipe and comprises a top block, and the; the inside of the supporting component or the wedge block is provided with a magnetic material body.

The valve units are formed by cutting an integral round table top, and the sealing performance of the side face of the cone surface between every two valve units is good. The inner side of the valve unit facing the inner pipe is connected with the outer pipe through a supporting component; and a magnetic material body is arranged in the support component or the wedge block, so that the function of jacking and adsorbing the valve unit by the jacking block is realized. The supporting component is contacted with and props against the outer pipe and the valve unit, the force applied to the joint of the upper end of the valve becomes very small, most of the acting force transmitted to the valve unit by the soil body is born by the supporting component, and the other part of the acting force is transmitted to the bottom plane of the inner pipe by the upper end surface of the valve to be born; when the valve in the lower part of the cast-in-situ large pipe pile hole forming device is driven into an underground soil body, the stress at the joint of the valve unit and the inner pipe is greatly reduced due to the connection limiting effect of the supporting assembly, the deformation and dislocation of the valve unit when the valve unit is driven into a pile mould are reduced, and the service life and the efficiency of the valve of the hole forming device are improved. The supporting component can enhance the pressure bearing capacity of the valve unit, prevent the valve unit from deforming when the pile mould is driven in, ensure that the valve unit can play a stable guiding role, prevent the pile mould from inclining and deviating, and improve the structural strength and the reliability of the cast-in-situ large tubular pile. The top block part in the supporting component is provided with a magnetic material body, the top block has magnetism and can attract and pull the valve unit to be attached to the top block, the connection sealing performance and stability of the valve unit and the inner pipe are enhanced, and the valve unit is prevented from falling off; the top block of the supporting component vibrates due to the vibration brought by the vibration hammer when demoulding, and vibrates the concrete positioned on the upper, lower, left and right sides of the supporting component, thereby enhancing the structural strength of the concrete. The outer pipe and the hole forming circular truncated cone are propped through the contact of the jacking block, the force applied to the joint of the valve and the inner pipe is borne by the jacking block, the connection strength between the valve and the inner pipe below the cast-in-place large pipe pile hole forming device is enhanced during hole forming, and the stress applied to the joint of the inner pipe circular valve unit is reduced; the hole-forming round platform is positioned in the outer pipe, and the pile die is guided by the hole-forming round platform and the outer pipe together, so that the pile die is prevented from inclining, and the structural strength of the cast-in-situ large pipe pile is improved; the cross section area of the outer pipe is larger than that of the inner pipe, and when the outer pipe is subjected to the same earthwork pressure, the stress on the outer pipe is small, so that the service life of the pile mould is prolonged; the ejector pad can strengthen the compressive capacity of valve unit, prevents that the valve unit from warping when driving into the pile mould, makes the valve unit can play stable guide effect, prevents that the pile mould from inclining the skew, improves cast-in-place big tubular pile's structural strength and reliability.

Preferably, the supporting component further comprises a clamping block, the clamping block is fixed on the side face, facing the outer pipe, of the valve unit, the clamping block comprises two parallel clamping walls, and the top block is located in the clamping portion, clamped by the two clamping walls, and in interference fit with the two clamping walls. The top block and the clamping block are fixed conveniently, and the valve unit is positioned; can cooperate the location through grip block and kicking block, prevent that the flapper unit from rocking. The supporting component is matched with the clamping block to clamp and jack, so that the problems of infirm driving, instable driving and insufficient strength of the valve of the traditional large tubular pile hole forming device in place are solved, and the supporting component can be attached to the inner side of the outer tube and the outer side of the valve unit at the same time.

Preferably, the magnetic material body is positioned at one end of the top block or the clamping block, the top block and the clamping block are respectively positioned at the inner side of the outer pipe and the outer side of the valve unit, or the top block and the clamping block are respectively positioned at the outer side of the valve unit and the inner side of the outer pipe, and the top block and the clamping block are fixedly clamped. The ejector block is fixed with the clamping block in a magnetic auxiliary mode, the ejector block is magnetic and can attract the ejector block to be attached to the valve unit, connection sealing performance and stability of the valve unit and the outer pipe are improved, the valve unit is prevented from falling off, therefore, soil is prevented from being mixed into concrete of the large-diameter pipe pile, and structural strength of the large-diameter pipe pile is improved; the ejector pad can extrude and stir the concrete that is located the ejector pad upside when the drawing of patterns, strengthens the structural strength of concrete.

As preferred, the kicking block is fixed on the outer tube, and the kicking block includes that the longitudinal section is rectangular canned paragraph and is located canned paragraph below longitudinal section for right triangle's support section, and the canned paragraph is located between inner tube and the outer tube, and the support section is located between outer tube and the valve unit, and the one side at the hypotenuse place of support section is laminated with the outside of valve unit, and the kicking block is equipped with the support cambered surface of laminating with the valve unit towards one side of valve unit. The kicking block is stable with being connected of outer tube, supports and fixed effectual.

Preferably, the upper end face of the valve unit and the bottom plane of the inner pipe are horizontally sealed when the valve unit is closed, and the lower end of the valve unit is provided with a vertical cylindrical surface so as to be lapped with the inner side face of the outer pipe to form cylindrical surface sealing. The lower end of the valve unit is respectively lapped with the inner side surface of the outer pipe to form a cylindrical vertical surface seal, and the seal between the lower end of the valve unit and the outer pipe is completed.

Preferably, the upper end of the flap unit is provided with a connecting sleeve, a mandrel is arranged in the connecting sleeve, two ends of the mandrel are positioned outside the connecting sleeve to form two connecting parts, and the lower end of the inner tube is provided with a matching sleeve matching the connecting parts. Rotatable connection of the valve unit and the inner pipe is completed through the connecting sleeve and the mandrel, and demoulding of the pile mould after concrete pouring is facilitated.

Preferably, the top end of the side face of the top block, which is attached to the outer pipe, is provided with a transition fillet. Stress concentration of the top block is prevented through the transition round angle, and the service life of the top block is prolonged; the valve unit is convenient to demould, and the demoulding efficiency of the pile mould is improved.

Preferably, a protection ring rib is arranged on the inner side of the outer pipe corresponding to the lower end of the valve unit. The joint sealing performance of the pore-forming circular truncated cone and the outer tube is improved, and the pressure applied to the valve unit when the tubular pile is driven into the ground is reduced.

A use method of a valve in a cast-in-situ large tubular pile hole forming device comprises the following steps:

a. the pile driver is put in place, and the valve unit and the double-layer sleeve are assembled into a pile mould through a mandrel;

b. the inner tube and the valve unit are adsorbed by using a magnetic material body on the support assembly or the wedge block, and the valve unit is closed;

c. sinking the pile mould into the underground design depth through a pile machine;

d. pouring concrete into the cavity of the double-layer sleeve;

e. and lifting the double-layer sleeve, automatically opening the valve unit under the pressure of concrete, and solidifying the concrete to form the tubular pile.

The invention has the advantages that:

1. the valve unit has a stable structure, so that the pore-forming platform can play a stable guiding role, the pile mould is prevented from inclining and deviating, and the structural strength and reliability of the cast-in-situ large pipe pile are improved;

2. the valve unit is positioned in the outer pipe, and the valve unit and the outer pipe guide the pile mould together, so that the pile mould is prevented from inclining, and the structural strength of the cast-in-situ large pipe pile is improved;

3. the jacking block is stressed, the stress of the mandrel is small, and the service life of the mandrel is prolonged;

4. the valve units are formed by cutting the same round table, are aligned after being combined, have good sealing performance and improve the structural strength of the large-diameter tubular pile;

5. when the top block of the supporting component is demolded, the concrete positioned on the upper part, the lower part and the left part and the right part of the supporting component is vibrated due to the vibration brought by the vibration hammer, so that the structural strength of the concrete is enhanced;

6. the cross section area of the outer pipe is larger than that of the inner pipe, when the outer pipe is subjected to the same earthwork pressure, the stress on the outer pipe is small, and compared with an outer valve pipe pile with the same size, the service life of a pile mould is prolonged;

7. the support component with magnetism can also enhance the connection sealing property and stability of the valve unit and the outer pipe, complete magnetic sealing and improve the strength of the cast-in-situ large-diameter pipe pile.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

FIG. 2 is an exploded view of the mounting of the hole forming boss of the present invention.

Fig. 3 is a top view of a piling mould used in the present invention.

Fig. 4 is a schematic structural diagram of the top block of the present invention.

FIG. 5 is a schematic view showing the construction of wedges according to the present invention.

Fig. 6 is a schematic structural diagram of another embodiment of the present invention.

In the figure: the outer tube 1 pore-forming conical surface 11, the inner tube 2, the connecting sleeve 3, the mandrel 4 pore-forming circular table 5, the valve unit 51, the vertical cylindrical surface 511, the wedge block 52, the top block 6, the fixed section 601, the supporting section 602, the cambered surface 603, the transition fillet 604, the clamping block 7 and the protection circular rib 8.

Detailed Description

The invention is further described below with reference to the figures and specific embodiments.

In fig. 1 to 6, a flap in cast-in-place large tubular pile hole former, can constitute the pile mould of cast-in-place large tubular pile with double-deck sleeve pipe, double-deck sleeve pipe includes inner tube 2 and outer tube 1 with the inner tube 2 coaxial line, interior flap includes a plurality of flap units 51, flap unit 51 is that same round platform cutting takes shape, the upper end of flap unit 51 is equipped with adapter sleeve 3, be equipped with dabber 4 in the adapter sleeve 3, thereby the both ends of dabber 4 are located adapter sleeve 3's outside and form two connecting portion, the lower extreme of inner tube 2 is equipped with the cooperation sleeve pipe of cooperation connecting portion, make rotatable the connection of flap unit 51 the downside at inner tube 2 through dabber 4 and the sheathed tube of cooperation connection. The lower extreme of outer tube 1 is equipped with the pore-forming conical surface 11, and the pore-forming conical surface 11 is located the inboard of outer tube 1 lower extreme, makes things convenient for double-deck sleeve pipe to squeeze into ground downwards. In fig. 3, wedges 52 for supporting two adjacent flap units 51 are arranged in a double-layer sleeve, the two side edges of the flap units 51 are parallel, wedge-shaped gaps are reserved after the flap units 51 are cut, the wedge-shaped gaps are supported by the wedges 52, the flap units 51 are matched with the wedges 52 to form hole-forming circular truncated cones, the hole-forming circular truncated cones are positioned in the outer tube 1, the flap units 51 can be lapped with the inner side surface of the outer tube 1, a supporting assembly is arranged between the flap units 51 and the outer tube 1, the supporting assembly comprises a top block 6, and the top block 6 can be simultaneously attached to the outer tube 1 and the hole-forming circular truncated cones 5; the support member or wedge 52 has a body of magnetic material disposed therein, as shown in fig. 4. The supporting component further comprises a clamping block 7, the clamping block 7 is fixed on the side face, facing the outer tube 1, of the valve unit 51, the clamping block 7 comprises two parallel clamping walls, and the top block 6 is located inside the two clamping walls and in interference fit with the two clamping walls. After the flap unit 51 is attached to the outer tube 1, the ejector block 6 and the clamping block 7 can be just attached to each other, and the axial fixation of the ejector block 6 towards one side of the outer tube 1 is completed through the clamping block 7. The magnetic material body is positioned at one end of the top block 6 or the clamping block 7, the top block 6 and the clamping block 7 are respectively positioned on the inner side of the outer tube 1 and the outer side of the valve unit 51, or the top block 6 and the clamping block 7 are respectively positioned on the outer side of the valve unit 51 and the inner side of the outer tube 1, and the top block 6 and the clamping block 7 are clamped and fixed. In fig. 1 and 4, the top block 6 is fixed on the outer tube 1, the top block 6 is welded on the inner side of the outer tube 1, the clamping block 7 is welded on the outer side of the valve unit 51, the top block 6 comprises a fixing section 601 with a rectangular longitudinal section and a supporting section 602 with a right-angled triangle longitudinal section below the fixing section 601, the fixing section 601 is located between the outer tube 1 and the inner tube 2, the supporting section 602 is located between the outer tube 1 and the valve unit 51, one side of the inclined side of the supporting section 602 is attached to the outer side of the valve unit 51, and a supporting arc surface 603 attached to the valve unit 51 is arranged on one side of the top block 6 facing the valve unit 51. As can be seen from fig. 1 and 4, the side of the top block 6 facing the inner tube 2 is provided with a segment of circular groove and cylindrical hole for respectively accommodating the connecting sleeve 3 and the magnetic material body to prevent the interference of the movement of the valve unit 51. In fig. 5, the wedges 52 are similar in structure to the top block 6, and the wedges 52 are different from the top block in that the wedges are gradually reduced in size from a side close to the outer tube 1 toward a side of the inner tube 2 to facilitate the rotation of the flapper unit 51. In fig. 4 the body of magnetic material is fixed to the side of the top piece 6 facing the flap unit 51. The upper end surface of the valve unit 51 and the bottom plane of the inner tube 2 are horizontally sealed when the valve unit 51 is closed, and the lower end of the valve unit 51 is provided with a vertical cylindrical surface 511 so as to be lapped with the inner side surface of the outer tube 1 to form cylindrical surface sealing. The upper end of the top block 6, which is attached to the side surface of the inner tube 2, is provided with a transition fillet 604. The inner side of the outer tube 1 is provided with a protective circular ring rib 8 corresponding to the lower end of the valve unit 51.

The embodiment shown in fig. 6 differs from that of fig. 1 in that the bore-forming cone 11 of the outer tube 1 in fig. 3 is located outside the lower end of the outer tube 1.

A use method of a valve in a cast-in-situ large tubular pile hole forming device comprises the following steps: the pile driver is in place, and the valve unit 51 and the double-layer sleeve are assembled into a pile mould through the mandrel 4; the outer tube 1 and the valve unit 51 are attracted by the magnetic material body on the support assembly or the wedge, and the valve unit 51 is closed; sinking the pile mould into the underground design depth through a pile machine; pouring concrete into the cavity of the double-layer sleeve; the double-layer sleeve is lifted, the valve unit 51 is automatically opened under the pressure of concrete, and the concrete is solidified to form a tubular pile.

The valve units 51 are formed by cutting an integral round table top, and the installation and sealing performance of the side surface of the cone surface between every two valve units 51 is good; the outer pipe 1 and the valve unit 51 are propped against through the contact of the supporting component, the force borne by the mandrel 4 at the upper end of the valve becomes very small, most of the acting force transmitted to the valve unit 51 by soil is borne by the supporting component, and the other part of the acting force is transmitted to the bottom plane of the inner pipe 2 from the upper end surface of the valve and borne; when the valve below the cast-in-situ large pipe pile hole forming device is driven into an underground soil body, the stress of the mandrel 4 is greatly reduced due to the connection limiting effect of the supporting assembly, the deformation and dislocation of the valve unit 51 when the valve unit is driven into a pile mould are reduced, and the service life and the efficiency of the valve of the hole forming device are improved. The supporting component can enhance the pressure bearing capacity of the valve unit 51, prevent the valve unit 51 from deforming when the pile mould is driven in, ensure that the valve unit 51 can play a stable guiding role, prevent the pile mould from inclining and deviating, and improve the structural strength and the reliability of the cast-in-situ large tubular pile. The top block 6 in the supporting assembly is provided with a magnetic material body, the top block 6 is provided with magnetism and can attract the valve unit 51 to be attached to the top block 6, and the wedge block 52 can also be provided with the magnetic material body; the top block 6 of the supporting component vibrates the concrete positioned on the upper, lower, left and right sides of the supporting component due to the vibration brought by the vibration hammer during demoulding, so that the structural strength of the concrete is enhanced.

Claims (9)

1. A cast-in-situ large tubular pile hole former inner valve can be combined with a double-layer sleeve pipe into a pile mould of the cast-in-situ large tubular pile, the double-layer sleeve pipe comprises an inner pipe and an outer pipe which is coaxial with the inner pipe, and is characterized in that the inner valve comprises a plurality of valve units, the valve units are cut and formed by a same round platform, the valve units are rotatably connected to the lower side of the inner pipe, wedge blocks for supporting two adjacent valve units are arranged in the double-layer sleeve pipe, the valve units and the wedge blocks are matched to form a hole forming round platform, and the edges of the two sides of the valve units are; the wedge block gradually reduces in size from one side close to the outer pipe to one side of the inner pipe; the hole-forming circular truncated cone is positioned in the outer tube; the valve unit can be in lap joint with the inner side surface of the outer pipe, a support assembly is arranged between the valve unit and the outer pipe, the support assembly comprises a top block, and the top block can be attached to the outer pipe and the valve unit at the same time; the supporting component further comprises a clamping block, the clamping block is fixed on the side face, facing the outer pipe, of the valve unit, the clamping block comprises two parallel clamping walls, and the top block is located inside the two clamping walls and in interference fit with the two clamping walls.

2. The cast-in-place large tubular pile hole forming device inner valve according to claim 1, wherein a magnetic material body is arranged in the supporting component or the wedge block.

3. The cast-in-place large tubular pile hole forming device internal valve of claim 2, wherein the magnetic material body is positioned at one end of the top block or the clamping block, the top block and the clamping block are respectively positioned at the inner side of the outer tube and the outer side of the valve unit, or the top block and the clamping block are respectively positioned at the outer side of the valve unit and the inner side of the outer tube, and the top block and the clamping block are fixedly clamped.

4. The internal valve of a cast-in-situ large tubular pile hole forming device according to claim 1, 2 or 3, wherein the top block is fixed on the outer tube, the top block comprises a fixing section with a rectangular longitudinal section and a supporting section with a right triangle longitudinal section below the fixing section, the fixing section is positioned between the inner tube and the outer tube, the supporting section is positioned between the outer tube and the valve unit, one side of the supporting section where the bevel edge is positioned is attached to the outer side of the valve unit, and one side of the top block facing the valve unit is provided with a supporting arc surface attached to the valve unit.

5. The internal valve of a cast-in-situ large tubular pile pore-forming device according to claim 1, 2 or 3, wherein the upper end surface of the valve unit is horizontally sealed with the bottom plane of the inner tube when the valve unit is closed, and the lower end of the valve unit is provided with a vertical cylindrical surface so as to be lapped with the inner side surface of the outer tube to form cylindrical surface sealing.

6. The cast-in-situ large tubular pile hole forming device inner valve according to claim 1, wherein the valve unit is provided with a connecting sleeve at the upper end, a mandrel is arranged in the connecting sleeve, two ends of the mandrel are positioned outside the connecting sleeve to form two connecting parts, and the inner tube is provided with a matching sleeve matching the connecting parts at the lower end.

7. The internal valve of a cast-in-situ large tubular pile hole forming device according to claim 1, wherein the upper end of the top block, which is attached to the side surface of the outer tube, is provided with a transition fillet.

8. The cast-in-situ large tubular pile hole forming device inner valve according to claim 1, wherein the inner side of the outer tube corresponding to the lower end of the valve unit is provided with a protective circular ring rib.

9. A method for using a valve in a cast-in-situ large tubular pile hole forming device based on any one of the claims 1 to 8, comprising the following steps:

a. the pile driver is put in place, and the valve unit and the double-layer sleeve are assembled into a pile mould through a mandrel;

b. the inner tube and the valve unit are adsorbed by using a magnetic material body on the support assembly or the wedge block, and the valve unit is closed;

c. sinking the pile mould into the underground design depth through a pile machine;

d. pouring concrete into the cavity of the double-layer sleeve;

e. and lifting the double-layer sleeve, automatically opening the valve unit under the pressure of concrete, and solidifying the concrete to form the tubular pile.

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