CN101298770B - Bottom enlarging prestress conical pipe pile and construction method thereof - Google Patents

Abstract

The invention belongs to the technical field of building pile foundations, in particular to a prestressed conical pipe pile with expanded bottom. It is characterized in that it consists of two parts: the prestressed tapered pipe pile body and the enlarged head. The pile body is formed by splicing multiple truncated inverted cone pipe sections with the same inclination angle or splicing truncated inverted cone body pipe sections with different inclination angles. The prestressed tapered pipe pile; the reinforcement cage in the enlarged head adopts a radial form of variable diameter. The cross section of the pile body is circular, hollow quadrangular, hollow hexagonal or hollow triangular. The effect and benefit of the invention is to increase the positive frictional resistance of the pile side and the pile end resistance, and at the same time effectively reduce the influence of the negative frictional resistance on the pile body, so as to ensure the strength of the pile body and the construction press-in efficiency. The expanded-bottom prestressed conical pile can take advantage of the advantages of prestressed tubular piles, conical piles and expanded-bottom piles at the same time and avoid their respective shortcomings: improve the utilization rate of unit material strength, increase the positive friction resistance of the pile side and the pile end resistance and At the same time, it can effectively reduce the influence of pile side negative friction resistance on the pile body, thereby improving the overall bearing capacity of the foundation pile.

Description

A prestressed conical pipe pile with expanded bottom and its construction method

technical field

The invention belongs to the technical field of building pile foundations, and in particular relates to a bottom-expanding prestressed conical pipe pile and a construction method thereof.

Background technique

The vertical bearing capacity of pile foundation is composed of two parts: pile side friction resistance and pile tip resistance. Traditional equal-section piles have disadvantages such as low utilization rate of unit material strength, and the pile body is significantly affected by pile side negative friction resistance; prestressed concrete pipe piles have high pile strength (C60-C80), strong pile sinking capacity, and single pile bearing High strength, short construction period, low cost and other advantages. At present, the commonly used conical piles use the inclined surface of the inverted cone to convert part of the vertical downward force into a horizontal force, so as to fully exert the bearing capacity of the soil on the pile side, thereby improving the frictional resistance of the pile side. .x, etc.) have the advantages of better soil penetration and higher pile unit bearing capacity than prestressed pipe piles with equal diameters. Restrictions; currently commonly used bottom expansion piles (such as: ZL200410102711.6, ZL200510009681.9, etc.) are based on traditional equal-section piles, and the bottom of the pile is enlarged to increase the cross-sectional area of the pile end, thereby increasing the resistance value of the pile end , but this method does not improve the pile side friction resistance, and is easily affected by the pile side negative friction resistance and reduces the overall bearing capacity of the pile foundation.

Pretensioned prestressed concrete (or high-strength concrete) pipe pile is a hollow cylindrical slender concrete prefabricated component made by pretensioned prestressing process and centrifugal forming method. It is mainly composed of cylindrical pile body, end plate and Composed of steel hoops, etc.; this pile type has the advantages of high pile body strength, strong pile sinking capacity, high single pile bearing capacity, short construction period, low cost, etc., and is easy to mass-produce, so it has been widely used in actual engineering; For the selection of raw materials for prestressed pipe piles, corresponding technical specifications have been formulated for pipe joint manufacturing, pipe pile splicing, quality control, product inspection, storage, transportation and other related details (such as: the national product standard "Pretensioned Prestressed Concrete "GB13476-1999, "Pretensioned Prestressed Concrete Thin-walled Pipe Pile" JC888-2001, "Technical Regulations for the Production of Pretensioned Prestressed Pipe Pile" (FS/QW01-2002), Prestressed Concrete Pipe Pile (Atlas )03SG409, Guangdong standard "Technical Regulations for Prestressed Pipe Pile Foundation" DBJ15-22-98, etc.), which are relatively mature technologies.

Contents of the invention

The technical problem to be solved by the present invention is to provide a prestressed tapered pipe pile with enlarged bottom that can simultaneously increase the positive frictional resistance of the pile side and the resistance value of the pile end, and can effectively reduce the influence of the negative frictional resistance of the pile side on the pile body.

Technical solution of the present invention is as follows:

The present invention improves the traditional equal-diameter prestressed pipe pile production equipment to meet the needs of the production of prestressed conical pipe piles, according to the actual engineering design of the tapered angle θ, pile length L and the size of the upper and lower pile diameters D _i Adjust the size of the conical tube pile body, end plate and steel hoop, and make the prestressed conical tube pile joints by pretensioning prestressing process and centrifugal forming method. According to the difference of the tapered barrel pile body, the prestressed tapered pipe pile with the cross section of the pipe joint pile body in the shape of a circular ring, a hollow quadrilateral, a hollow hexagon or a hollow triangle can be manufactured. The prestressed conical pipe pile is formed by splicing multiple truncated inverted cone pipe sections with the same inclination angle or splicing truncated inverted conical body pipe sections with different inclination angles.

In order to make the enlarged head of the pile end have better mechanical properties, the present invention designs a radial reinforcement cage with variable diameter: a movable hinge body is used to connect the main reinforcement and the stirrup, and together with the rest plate, a radial reinforcement cage with variable diameter is formed. Steel cage system. During the lowering of the reinforcement cage, due to the stress on the upper end of the reinforcement cage, the reinforcement cage is in a contracted state so that it can pass through the pipe pile and sink to the bottom expansion cavity; when the lower end of the reinforcement cage sinks to the design height and touches the soil, the reinforcement cage With the self-weight of the steel bar itself or the load imposed by the upper stirrup, the cage gradually expands outward into a radial shape; finally reaches the position of the rest plate and stops further development, so that the steel cage is in a more reasonable radial shape.

The effect and benefit of the present invention are that the prestressed tapered pipe pile body can increase the positive friction resistance of the pile side, and at the same time can effectively reduce the influence of the negative friction resistance on the pile body, and the prefabricated prestressed tapered pipe pile body is easy to ensure Pile body strength and construction press-in efficiency; the pile end expansion head can effectively increase the resistance of the pile end, and the variable-diameter radial reinforcement cage can improve the mechanical properties of the pile end expansion head to ensure strength. The expanded-bottom prestressed conical pile can take advantage of the advantages of prestressed tubular piles, conical piles and expanded-bottom piles at the same time and avoid their respective shortcomings: improve the utilization rate of unit material strength, increase the positive friction resistance of the pile side and the pile end resistance and At the same time, it can effectively reduce the influence of pile side negative friction resistance on the pile body, thereby improving the overall bearing capacity of the foundation pile. The inclination angle of the inclined surface of the pile body of this pile type is not easy to be too large, and the effect is better for medium and short piles.

Description of drawings

Fig. 1 is a kind of structure diagram of the present invention.

Fig. 2(a) is a schematic cross-sectional view of the end plate of the prestressed tapered pipe pile of the present invention.

Fig. 2(b) is a schematic diagram of the layout of the pipe joints of the prestressed tapered pipe pile of the present invention.

Fig. 2(c) is a schematic cross-sectional view of the pipe joint of the prestressed conical pipe pile of the present invention.

Fig. 3(a) is a schematic diagram showing the shrinkage of the diameter-reducing radial reinforcement cage of the present invention.

Fig. 3(b) is a schematic diagram of the unfolded radial reinforcement cage with variable diameter according to the present invention.

Fig. 4 is a schematic diagram of the construction process of the present invention.

In the figure: 1 is a prefabricated prestressed conical pipe pile with a truncated top and inverted cone shape, and the horizontal section is a circular ring with a large upper part and a smaller lower part; 2 is the enlarged head of the cast-in-place pile; 3 is the tapered cylindrical pile body; 4 is the end plate; 5 is the steel ferrule; 6 is the bolt hole; 7 is the anchor hole of the prestressed tendon; 8 is the prestressed tendon; 9 is the spiral stirrup; 10 is the stirrup; 11 is the main tendon; 12 is movable Hinged body; 13 is a resting plate; Fig. 4(a) before pile sinking (the solid line arrow indicates the direction of pile sinking load); Fig. 4(b) one pipe joint pile sinking is completed; Fig. 4(c) two pipes are connected by electric welding Fig. 4(d) the pile sinking is completed; Fig. 4(e) take the floating soil in the pipe pile and the spud can and expand the bottom to form a cavity (the dotted line arrow indicates the direction of taking the floating soil); Fig. 4(f) the lower reinforcement cage (the dotted line The arrow indicates the direction of the lower reinforcement cage); Figure 4(g) the enlarged head of the cast-in-place pile (the dotted arrow indicates the direction of pouring concrete); Figure 4(h) the pile.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions and accompanying drawings.

Firstly, the first section of prestressed conical pipe pile pipe joint (also called the bottom) with the pile point (boot) is made by static pressure method, hammering method, vibration method, water jet method, pre-drilling method and middle digging method. Pile, as shown in Fig. 2) sinks into the soil (as shown in Fig. 4(a)(b)); secondly, the end plate electric welding connection method is used to connect the second prestressed conical pipe pile pipe joint and make it sink into the soil (as shown in Figure 4(c)), complete the following sections of pipe piles in sequence so that the bottom of the pile sinks to the design elevation, and the pile length meets the design requirements (as shown in Figure 4(d)); then take out the pile tip (boots), use earth-taking equipment (such as air suction equipment, etc.) to take out the soil plug located in the lower part of the pile body in the pipe pile (when using an open pile point (boot), the height of the soil plug is about 1/3 of the pile length, and use For the closed pile tip (boot), the height of the soil plug is relatively small), inspect the quality of the pipe pile body and re-measure the length of the pile sinking, etc.; then use the bottom expansion equipment to expand the bottom of the pile to form a For the cavity of the base that is larger than the diameter of the lower pile, the soil in the cavity is taken out with air suction equipment (as shown in Figure 4(e)); As shown), when the reinforcement cage sinks to the design elevation, a load is applied on the upper end of the reinforcement cage to make it unfold radially (as shown in Figure 3(b)), and the lowering process of the reinforcement cage is completed (Figure 4(f) shown); then cast-in-place concrete forms the pile head at the bottom of the pile and ensures that the pile head is formed regularly and the cast-in-place pile head is well connected with the prefabricated prestressed pipe pile (as shown in Figure 4(g)); finally the pile is completed ( As shown in Figure 4(h)).

Claims (3)

1. bottom enlarging prestress conical pipe pile, comprise prestress conical pipe pile pile body and enlarged footing two parts, it is characterized in that: pile body adopts the prestress conical pipe pile that is spliced to form to the truncation back taper body tube coupling of the splicing of the truncation back taper body tube coupling at the same inclination angle of more piece or different angle; Reinforcing cage in the enlarged footing adopts the radial form of reducing.

2. a kind of bottom enlarging prestress conical pipe pile according to claim 1 is characterized in that: the pile body cross section is annular, hollow quadrangle, hollow hexagon or hollow triangle.

3. the job practices of the described a kind of bottom enlarging prestress conical pipe pile of claim 1 is characterized in that following steps:

(1) the first segment prestress conical pipe pile tube coupling that adopts static pressure method, hammering method, lash method, water jetting, prebored hole method or middle pick method will have shoe sinks in the soil;

(2) adopt end plate electric welding connecting method to connect the second joint prestress conical pipe pile tube coupling and make it to sink in the soil, finish successively and sink to the design elevation place at the bottom of a few pipe joint stakes in back make, stake reaches designing requirement;

(3) take out shoe, utilize borrow equipment to take out the soil plug that is positioned at the pile body bottom in the pile tube;

(4) expand the end at the bottom of utilizing bottom-expanding equipment to stake, make a bottom portion form a base cavity pocket, inhale indigenous equipment with air and take out soil in the cavity greater than bottom stake footpath;

(5) sink to being in the radial reinforcing cage of contraction-like reducing, when reinforcing cage sank down into design elevation, apply a load that it is launched into was radial in the reinforcing cage upper end, finished the process of transferring of reinforcing cage;

(6) cast-in-situ concrete forms the stake major part and guarantees that a major part rule moulding links to each other well with prefabricated prestressing pipe pile with the present walling pile major part at the bottom of stake, and pile is finished.

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