CN112343042A - UHPC prefabricated special-shaped pile and preparation method thereof - Google Patents

Abstract

The invention discloses a UHPC prefabricated special-shaped pile, which comprises a pile body with a hollow cylindrical structure, wherein the pile body is a non-prestressed reinforced concrete pile prefabricated and formed by a steel reinforcement framework and UHPC concrete, steel fibers are added into the UHPC concrete, and a plurality of annular bearing discs for enhancing the anti-settling capacity of the pile body are axially and integrally formed on the pile body at intervals; the bearing disc is an annular convex body which is formed on the upper section of the pile body by two loading inclined planes and a friction surface and has a trapezoidal structure, or the bearing disc is an annular convex body which is formed on the upper section of the pile body by two loading inclined planes and has a triangular structure; the inclination angle alpha between the lower loaded inclined plane and the horizontal plane in the two loaded inclined planes is 45 degrees. The preparation method of the UHPC prefabricated special-shaped pile has simple process, does not need the traditional tensioning and releasing process links, and solves the problems that the steel die cannot follow the pile body to compress and deform and the steel die can not be manufactured in the releasing and releasing process of the traditional process.

Description

UHPC prefabricated special-shaped pile and preparation method thereof

Technical Field

The invention relates to the technical field of civil engineering, in particular to a UHPC prefabricated special-shaped pile and a preparation method thereof.

Background

The large settlement, especially the uneven settlement in the foundation engineering easily causes the original statically indeterminate structure to generate large secondary internal force, and the structure is cracked and even damaged. The method has higher requirements on the anti-settling capacity of the pile foundation particularly in soft soil areas, and the friction type pile often needs to be lengthened to obtain larger friction resistance, so that the manufacturing cost is greatly increased. The high-strength performance of the traditional tubular pile and the pile body of the square pile are difficult to effectively exert in a soft soil area, and great mechanical biting force and frictional resistance cannot be provided. Meanwhile, the common hammering and static pressure methods of the traditional precast pile not only easily cause damage to the pile body, but also cause noise pollution.

In the prior art, a plurality of annular bulges are arranged on the outer wall of a pile body at intervals in the axial direction, so that the friction resistance of the pile side can be improved, and the bearing capacity of a pile foundation is improved. The precast pile belongs to a special-shaped pile and is produced mainly by a centrifugal method, a high-strength steel bar is used for applying pre-tensioning prestress, the prestress is anchored by an external mold, a tensioning system and a special template are required to be arranged, steam curing is carried out after the centrifugation is finished, and the steam curing is finished, and then the stretching and the demolding are carried out. The pile body can be compressed by 1.5-4 mm along the length direction due to the size of the concrete pre-compressive stress of the pile body in the tension releasing process. In the prior art, the pile body protruding part of the precast pile is fixed in the groove of the inner wall of the steel film, so that the precast pile cannot deform along with the pile body in the placing and stretching process, cracks are easily generated between the pile body and the pile body protruding part, and the precast pile body even falls off in serious conditions. In order to solve the problem, only the inner and outer die double-wall body type steel die for the prestressed concrete special-shaped pile with large manufacturing difficulty and higher manufacturing cost can be adopted, and the protruding height of the prefabricated pile body is limited.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art and provides a UHPC prefabricated special-shaped pile which is non-prestressed, high in bearing capacity, excellent in quality and low in mould cost and a preparation method thereof.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a UHPC prefabricated special-shaped pile comprises a pile body with a hollow cylindrical structure, wherein the pile body is a non-prestressed reinforced concrete pile prefabricated and formed by a steel reinforcement framework and UHPC concrete, steel fibers are added into the UHPC concrete, and a plurality of annular bearing discs for enhancing the anti-settling capacity of the pile body are axially and integrally formed on the pile body at intervals; the bearing disc is an annular convex body which is formed on the upper section of the pile body by two loading inclined planes and a friction surface and has a trapezoidal structure, or the bearing disc is an annular convex body which is formed on the upper section of the pile body by two loading inclined planes and has a triangular structure; the inclination angle alpha between the lower loaded inclined plane and the horizontal plane in the two loaded inclined planes is 45 degrees.

In order to optimize the technical scheme, the specific measures adopted further comprise:

the bearing discs are axially arranged on the pile body at equal intervals.

The maximum outer diameter of the bearing disc is 1.2-1.6 times of the outer diameter of the pile body.

The section of the bearing disc is isosceles trapezoid, and the included angle between the bearing inclined plane and the friction surface is an arc chamfer; or the section of the bearing disc is an isosceles triangle, and the included angle of the two bearing inclined planes is an arc chamfer.

The diameter of the steel fiber is 0.15-0.25 mm, and the length-diameter ratio is 60-120: 1.

the volume of the steel fiber accounts for 1-2% of the volume of the UHPC concrete.

The pile end plates are embedded in the two ends of the pile body, the steel reinforcement framework is a cylindrical framework formed by binding or welding non-prestressed steel bars arranged axially and hoop steel bars arranged annularly, and the pile end plates are welded and connected with the non-prestressed steel bars of the steel reinforcement framework.

The invention also provides a preparation method of the UHPC prefabricated special-shaped pile, which comprises the following steps:

1) manufacturing a single-layer wall type steel pile mould with a bearing disc forming cavity according to design requirements;

2) binding non-prestressed reinforcements and stirrups by using thin iron wires or welding by electric welding to manufacture a steel reinforcement framework, and welding and installing pile end plates at two ends of the steel reinforcement framework;

3) hoisting the steel reinforcement framework welded with the pile end plate in a single-layer wall type steel pile mould which is cleaned up and coated with a release agent uniformly;

4) pouring the UHPC concrete material added with the steel fiber into a single-layer wall type steel pile mould with a steel reinforcement framework, and closing the mould after pouring is finished;

5) and after die assembly, forming by a centrifugal process, then conveying to a curing pool for high-temperature steam curing until the concrete strength reaches a specified value, and then demolding to prepare the UHPC prefabricated special-shaped pile.

Compared with the prior art, the invention has the advantages that the bearing disks are formed on the pile body at intervals, and the diameters of the bearing disks are larger than that of the pile body, so that the end bearing effect of the pile can be realized, the mechanical biting force and the frictional resistance between the pile and the soil body around the pile are increased, and the aims of greatly improving the bearing capacity of the foundation pile and reducing the settlement deformation are fulfilled. The pile of the invention is made of UHPC concrete, steel fiber capable of improving the tensile strength of the pile body is distributed in the pile body, and the strength of the concrete can reach 120MPa to 160MPa, so that the bearing performance of the pile body is higher. The preparation method of the UHPC prefabricated special-shaped pile has simple process, does not need the traditional tensioning and releasing process links, and solves the problems that the steel die cannot follow the pile body to compress and deform and the steel die can not be manufactured in the releasing and releasing process of the traditional process.

Drawings

FIG. 1 is one of the schematic structural diagrams of the present invention;

FIG. 2 is a second schematic structural diagram of the present invention;

FIG. 3 is a top view of the invention with the pile tip plate removed;

fig. 4 is one of the cross-sectional views of the carrier plate of the present invention;

fig. 5 is a second schematic cross-sectional view of the force bearing disc of the present invention;

fig. 6 is a third schematic sectional view of the force bearing disc of the invention.

Detailed Description

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

Figures 1 to 6 are schematic views of the structure of the present invention and its use in pile sinking.

Wherein the reference numerals are: the pile comprises an arc chamfer R, a pile body 1, a bearing disc 2, a load bearing inclined plane 21, a friction surface 22, a pile end plate 3, a non-prestressed reinforcement 4 and a stirrup 5.

The invention discloses a UHPC prefabricated special-shaped pile which has extremely strong mechanical engaging force and frictional resistance, so that the anti-settling capacity of a pile foundation in a soft soil area is extremely high, and the UHPC prefabricated special-shaped pile comprises a pile body 1 with a hollow cylindrical structure. The pile body 1 of the invention is a non-prestressed reinforced concrete pile, and a special template with a tensioning system is not needed in the manufacturing process, so that the releasing and tensioning process in the traditional pile forming process is not needed. The pile body 1 is formed by prefabricating a steel reinforcement framework and UHPC concrete, and in order to further improve the mechanical property of the pile, the UHPC concrete is added with distributed steel fibers. UHPC is the short for ultra-high performance concrete, is a new cement-based material with high strength, high toughness and excellent durability, each mechanical property index of the material is between that of concrete and steel, and the tensile strength can reach more than 10Mpa by adding a certain content of steel fiber. The steel bar framework is a cylindrical framework formed by binding or welding non-prestressed steel bars 4 arranged axially and stirrups 5 arranged annularly. In the invention, the volume of the steel fiber accounts for 1-2% of the volume of the UHPC concrete, the diameter of the steel fiber is preferably 0.15-0.25 mm, and the length-diameter ratio is 60-120: 1.

fig. 1 and 2 show that a plurality of force bearing disks 2 for enhancing the anti-settling capacity of the pile body are axially and integrally formed on the pile body 1 at intervals, and the force bearing disks 2 are axially and optimally arranged on the pile body at equal intervals, and can be arranged according to the requirement. The diameter of the bearing disc 2 is larger than that of the pile body 1, and the maximum outer diameter of the bearing disc 2 is 1.2-1.6 times of the outer diameter of the pile body 1. The bearing disc 2 increases the contact surface between the pile body 1 and the soil around the pile, so that the friction resistance between the pile body and the soil is increased.

In the embodiment, the bearing disc 2 can be an annular convex body formed on the pile body by two loading inclined planes 21 and a friction surface 22 and having a trapezoidal structure in the section as shown in fig. 1, but the bearing disc 2 can also be an annular convex body formed on the pile body by two loading inclined planes 21 and having a triangular structure in the section as shown in fig. 2.

The two loaded ramps 21 of the present invention include a lower loaded ramp 21 located below and an upper loaded ramp 21 located above. The inclination angle α of the lower of the two load-bearing ramps 21 to the horizontal plane is preferably at most 45 °. The loading inclined plane 21 has the function of end bearing, and both the loading inclined plane 21 and the friction surface 22 can greatly enhance the mechanical engaging force and the frictional resistance between the pile and the soil body.

When the carrier plate 2 of the invention is of a trapezoidal configuration, there are two situations, the first being that the height h of the carrier plate 2 is equal to the length a of the friction surface 22 as shown in figure 4. Secondly, as shown in fig. 5, the height h of the carrier plate 2 is greater than the length a of the friction surface 22.

In order to avoid stress concentration, the invention reduces the damage to the bearing disc 2 possibly caused in the production, transportation and construction processes. As shown in fig. 4 and 5, when the force bearing disc 2 is in a trapezoidal structure, the included angle between the load inclined plane 21 and the friction surface 22 of the force bearing disc 2 is designed as an arc chamfer R. As shown in fig. 6, when the force bearing disc 2 is in a triangular structure, the included angle between the two load bearing inclined planes 21 is designed as an arc chamfer R.

When the section of the bearing disc 2 is trapezoid, the invention can be isosceles trapezoid, and when the section of the bearing disc 2 is triangle, the invention can also be isosceles triangle.

As shown in fig. 1, pile end plates 3 are embedded in both ends of a pile body 1 of the invention, and the pile end plates 3 are connected with non-prestressed reinforcements 4 of a steel reinforcement framework in a welding manner. The pile end plate 3 is provided for facilitating the sinking of the connecting pile.

The invention also provides a preparation method of the UHPC prefabricated special-shaped pile, which comprises the following steps:

1) manufacturing a single-layer wall type steel pile mould with a bearing disc forming cavity according to design requirements;

2) manufacturing a steel reinforcement framework by binding non-prestressed reinforcements 4 and stirrups 5 by using thin iron wires or performing electric welding, and welding and installing upper pile end plates 3 at two ends of the steel reinforcement framework;

3) hoisting the steel reinforcement framework welded with the pile end plate 3 in a single-layer wall type steel pile mould which is cleaned and coated with a release agent uniformly;

4) pouring the UHPC concrete material added with the steel fiber into a single-layer wall type pile mould with a steel reinforcement framework, and closing the mould after pouring is finished;

5) and after die assembly, forming by a centrifugal process, then conveying to a curing pool for high-temperature steam curing until the concrete strength reaches a specified value, and then demolding to prepare the UHPC prefabricated special-shaped pile.

The UHPC prefabricated special-shaped pile is made of UHPC concrete, the strength of the concrete can reach 120-160 MPa, which is more than 1.5 times of the strength of the existing conventional PHC tubular pile concrete (C80), the bearing performance of the pile body is higher, the wall thickness of the pile body can be thinner, and the light weight and high strength effects are achieved. The UHPC prefabricated special-shaped pile is prefabricated and formed in a factory, steel fibers capable of improving the tensile strength of the pile body are distributed in the pile body, so that a prestressed steel bar in the pile body can be omitted, a steel mould with a single-layer wall body structure and low cost and a simple structure can be adopted in the production process, the tensioning and releasing process links in the production process are omitted, and the problems that the steel mould cannot follow the compression deformation of the pile body and the steel mould is manufactured in the releasing process are solved, so that the structural size of a bearing disc of the UHPC prefabricated special-shaped pile is not limited by the steel mould manufacturing technology and the production demoulding technology, and the bearing disc with a larger protruding height can be prefabricated. The pile body of the invention is provided with a plurality of bearing discs, the resistance of the depth of the pile body to each soil layer can be fully utilized, the area of the foundation pile and the soil around the pile is enlarged, the mechanical engaging force and the frictional resistance are fully exerted, the end bearing effect of the bearing discs is improved, the original friction end bearing pile with only one end bearing point is changed into the end bearing friction pile with a plurality of end bearing points, the bearing capacity of the foundation pile is greatly improved, and the settlement deformation is reduced.

Ultra-High Performance Concrete, referred to as UHPC (Ultra-High Performance Concrete), is also called reactive powder Concrete; UHPC is an ultrahigh-strength cement-based material with high strength, high toughness and low porosity; the basic preparation principle is as follows: by increasing the fineness and activity of the components, coarse aggregate is not used, and defects (pores and microcracks) in the material are minimized, so that ultrahigh strength and high durability are obtained. The UHPC can be called as an engineering material with good durability, the mechanical property of the UHPC with proper reinforcement is close to that of a rigid structure, and meanwhile, the UHPC has excellent wear resistance and anti-explosion performance. Therefore, UHPC is particularly suitable for use in large span bridges, blast resistant structures (military engineering, bank vaults, etc.) and thin-walled structures, as well as in highly abrasive, highly corrosive environments. Currently, UHPC has been used in practical projects such as large-span pedestrian overpasses, highway-railway bridges, thin-walled silos, nuclear waste tanks, wire rope anchor stiffeners, ATM protective casings, and the like. It is expected that there will be more and more applications.

While the preferred embodiments of the present invention have been illustrated, various changes and modifications may be made by one skilled in the art without departing from the scope of the invention.

Claims (8)

1. The utility model provides a prefabricated heterotypic stake of UHPC, includes pile body (1) of hollow cylindrical structure, characterized by: the pile body (1) is a non-prestressed reinforced concrete pile prefabricated and formed by a steel bar framework and UHPC concrete, and steel fibers are added into the UHPC concrete; a plurality of annular bearing discs (2) for enhancing the anti-settling capacity of the pile body are axially and integrally formed on the pile body (1) at intervals; the bearing disc (2) is an annular convex body which is formed on the upper section of the pile body by two loaded inclined planes (21) and a friction surface (22) and has a trapezoidal structure, or the bearing disc (2) is an annular convex body which is formed on the upper section of the pile body by two loaded inclined planes (21) and has a triangular structure; the inclination angle alpha between the lower load bearing inclined plane (21) positioned at the lower part of the two load bearing inclined planes (21) and the horizontal plane is 45 degrees.

2. The UHPC prefabricated special-shaped pile as claimed in claim 1, which is characterized in that: the bearing discs (2) are axially arranged on the pile body at equal intervals.

3. The UHPC prefabricated special-shaped pile as claimed in claim 2, which is characterized in that: the maximum outer diameter of the bearing disc (2) is 1.2-1.6 times of the outer diameter of the pile body (1).

4. A UHPC prefabricated profile pile according to claim 3, wherein: the section of the bearing disc (2) is isosceles trapezoid, and the included angle between the load inclined plane (21) and the friction surface (22) is an arc chamfer (R); or the section of the bearing disc (2) is an isosceles triangle, and the included angle of the two bearing inclined planes (21) is an arc chamfer (R).

5. The UHPC prefabricated special-shaped pile as claimed in claim 4, wherein: the diameter of the steel fiber is 0.15-0.25 mm, the length-diameter ratio is 60-120: 1.

6. the UHPC prefabricated special-shaped pile as claimed in claim 5, wherein: the volume of the steel fiber accounts for 1-2% of the volume of the UHPC concrete.

7. The UHPC prefabricated special-shaped pile as claimed in claim 6, which is characterized in that: pile body (1) both ends all pre-buried have pile head plate (3), the framework of steel reinforcement be by axial setting non-prestressed reinforcement (4) and hoop reinforcement (5) ligature or the welded barrel-shaped body skeleton that constitutes that the hoop set up, pile head plate (3) be connected with framework of steel reinforcement's non-prestressed reinforcement (4) welding.

8. A method for preparing a UHPC prefabricated profiled pile according to any one of claims 1 to 7, which is characterized in that: the method comprises the following steps:

1) manufacturing a single-layer wall type steel pile mould with a bearing disc forming cavity according to design requirements;

2) manufacturing a steel reinforcement framework by binding non-prestressed reinforcements (4) and stirrups (5) by using thin iron wires or welding by electric welding, and welding and installing pile end plates (3) at two ends of the steel reinforcement framework;

3) hoisting the steel reinforcement framework welded with the pile end plate (3) in a single-layer wall type steel pile mould which is cleaned up and coated with a release agent uniformly;

4) pouring the UHPC concrete material added with the steel fiber into a single-layer wall type pile mould with a steel reinforcement framework, and closing the mould after pouring is finished;

5) and after die assembly, forming by a centrifugal process, then conveying to a curing pool for high-temperature steam curing until the concrete strength reaches a specified value, and then demolding to prepare the UHPC prefabricated special-shaped pile.

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