Special-shaped prefabricated square pile capable of reducing negative friction influence

Abstract

The invention relates to a special-shaped prefabricated square pile capable of reducing the influence of negative friction resistance. The special-shaped prefabricated square pile comprises a small-section prefabricated square pile body, an expanded head section and a large-section prefabricated square pile body which are sequentially connected from top to bottom. The large-section prefabricated square pile is in smooth transition to the small-section prefabricated square pile through gradually reducing the area of the expanded head section; the small-section prefabricated square pile is arranged on a negative friction soil layer above a neutral point; the small-section prefabricated square pile is adopted in the negative friction resistance soil layer, and the reduction value can be quantitatively analyzed; a large-section prefabricated square pile is adopted in a positive frictional resistance soil layer, and the negative frictional resistance influence of the soil layer on a pile body is effectively reduced. The bottom of the small-section prefabricated square pile is of an expanded head section structure and is connected with the large-section prefabricated square pile in a welded mode, pile sinking can be achieved through an existing conventional construction method, and construction is easy and convenient.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation engineering, and in particular to a special-shaped prefabricated square pile capable of reducing the influence of negative friction resistance. Background Art

[0002] Due to the complexity and diversity of geological structures, various special strata such as soft soil and fill may be encountered during engineering construction. Such strata usually have low bearing capacity, large settlement, and poor engineering properties such as vibration liquefaction, collapsibility, expansion, and frost heave. When constructing buildings on such strata, pile foundations with higher bearing capacity are usually required to transfer the load to deep soil or rock layers. However, when the pile body passes through the soft strata, due to some reasons, the soil layer around the pile often sinks more than the pile body, which generates negative friction.

[0003] At present, the commonly used technical solutions to reduce the influence of pile body friction resistance include:

[0004] (1) Adding a coating or film to the pile body can reduce the negative friction by reducing the standard value of the negative friction between the soil layer and the pile body.

[0005] However, the pile coating and film are easily damaged during the pile driving process, which requires extremely high construction technology and cannot quantitatively analyze the degree of weakening of negative friction. In addition, the chemical substances in the pile coating itself are likely to have adverse effects on the surrounding environment during long-term underground use, which is not conducive to environmental protection.

[0006] (2) Adding isolation piles to the pile body to reduce the negative friction of the soil layer on the pile body through physical isolation;

[0007] However, this solution increases the construction difficulty and construction workload, prolongs the construction period, and still cannot quantitatively analyze the degree of weakening of negative friction.

[0008] (3) For example, the patent publication number CN 105200988B discloses a "combined PHC pile for reducing negative friction", which includes an upper and lower PHC pile, a telescopic portion is provided between the two PHC piles, and a displacement transmission device is provided on the top of the PHC pile. The upper PHC pile is actively sunk by a hydraulic jack, which can effectively reduce or even eliminate the negative friction of the pile body; the upper PHC pile is actively sunk by a displacement transmission device and a hydraulic jack, so that the settlement of the pile body in the soft soil layer is greater than that of the soft soil layer, thereby solving the problem of negative friction.

[0009] However, a displacement transmission device and a hydraulic jack need to be separately installed, which makes construction inconvenient, and it is currently impossible to quantitatively analyze the degree of reduction in negative friction. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides a special-shaped prefabricated square pile that can reduce the influence of negative friction to solve the above problems.

[0011] The present invention provides the following technical solutions:

[0012] A special-shaped prefabricated square pile capable of reducing the influence of negative friction resistance comprises a small-section prefabricated square pile, an enlarged head section and a large-section prefabricated square pile connected in sequence from top to bottom;

[0013] The large-section prefabricated square pile smoothly transitions to the small-section prefabricated square pile by enlarging the head section area;

[0014] The small-section prefabricated square piles are arranged in a negative friction soil layer above the neutral point.

[0015] Preferably, the enlarged head section is arranged in a zero-friction soil layer below the neutral point, and the top of the enlarged head section is flush with the neutral point, and the large-section prefabricated square piles are arranged in a positive friction soil layer.

[0016] Preferably, the side length of the large-section prefabricated square pile is D, mm; the large-section prefabricated square pile has a built-in lower pile top embedded steel plate and a lower side embedded steel plate arranged at the lower periphery of the lower pile top embedded steel plate.

[0017] Preferably, the large-section prefabricated square pile is provided with a lower pile body main reinforcement, and the inner wall of the pre-buried steel plate at the lower pile top is provided with a lower anchor reinforcement, and the lower anchor reinforcement is A lower reinforcing steel bar is arranged between the two opposite lower side embedded steel plates, and the lower reinforcing steel bar is

[0018] Preferably, an equilateral angle steel is arranged between the inner sides of the adjacent lower side embedded steel plates, and a corner pad steel is arranged on the equilateral angle steel, and the corner pad steel is welded to the main reinforcement of the lower pile body to form an integral whole, and the corner pad steel is A middle pad is welded to the middle of the inner wall of the lower side embedded steel plate.

[0019] Preferably, the bottom cross-section of the enlarged head section has a side length of D-5, mm; the top cross-section has a side length of d, mm; the slope is 1:3; the side length of the small cross-section prefabricated square pile is d, mm;

[0020] The enlarged head section is internally provided with a middle bottom embedded steel plate and a middle side embedded steel plate arranged on the periphery of the middle bottom embedded steel plate, and the middle side embedded steel plate is a trapezoidal plate.

[0021] Preferably, reinforcing steel bars are arranged between the two opposing middle side embedded steel plates, and the reinforcing steel bars are A stiffening plate is arranged between the middle bottom embedded steel plate and the middle side embedded steel plate, and the reinforcing steel bars are welded to the middle side embedded steel plate and the stiffening plate.

[0022] Preferably, the small-section prefabricated square piles are internally provided with reinforcing steel bars and middle pile body main bars, the reinforcing steel bars obliquely extend into the enlarged head section and are welded to the stiffening plates, and the middle pile body main bars vertically extend into the enlarged head section.

[0023] Preferably, it also includes a plurality of groups of connecting steel plates of folded plate structure, and the connecting steel plates are welded to the outer side walls of the middle side embedded steel plates and the lower side embedded steel plates.

[0024] The present invention has the following beneficial technical effects:

[0025] The present invention adopts small-section prefabricated square piles in the negative friction soil layer, which can save the pile foundation engineering volume and reduce the downward pull load caused by the negative friction, and effectively reduce the negative friction influence of the soil layer on the pile body.

[0026] The bottom of the small-section prefabricated square pile adopts an enlarged head section structure and is connected to the large-section prefabricated square pile by welding. The pile can be sunk using the current conventional construction method, and the construction is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the prefabricated square piles of the present invention inserted into the soil layer;

[0028] Figure 2 This is a cross-sectional view of the top of a large-section prefabricated square pile of the present invention;

[0029] Figure 3 yes Figure 2 AA direction cross-sectional view;

[0030] Figure 4 It is a schematic diagram of the coordination of the side embedded steel plate, the lower side embedded steel plate and the connecting steel plate in the present invention;

[0031] Figure 5 It is a cross-sectional view of the enlarged head section and part of the small-section prefabricated square pile of the present invention;

[0032] Figure 6 yes Figure 5 BB direction cross-sectional view;

[0033] Figure 7 It is a schematic diagram of the structure of the side embedded steel plate in the present invention;

[0034] Figure 8 It is a structural schematic diagram of the stiffening plate of the present invention.

[0035] The reference numerals in the figure are:

[0036] 1. Prefabricated square piles with small cross-section; 2. Enlarged head section; 3. Prefabricated square piles with large cross-section; 4. Connecting steel plates;

[0037] 21. Pre-buried steel plate at the middle bottom; 22. Pre-buried steel plate at the middle side; 23. Stiffening plate; 24. Middle anchor bar; 25. Strengthening steel bar; 26. Reinforcement steel bar; 27. Main bar of the middle pile body;

[0038] 31. Pre-buried steel plate at the top of the lower pile; 32. Pre-buried steel plate at the lower side; 33. Equilateral angle steel; 34. Lower anchor bar; 35. Lower reinforcement steel bar; 36. Main reinforcement of the lower pile body; 37. Corner padding bar; 38. Middle padding bar; DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example:

[0041] A special-shaped prefabricated square pile that can reduce the influence of negative friction, such as Figure 1-8 As shown:

[0042] like Figure 1 As shown in the figure, the negative friction soil layer at the bottom of the cap adopts a small-section prefabricated square pile 1, and the lower part of the small-section prefabricated square pile 1 adopts an enlarged head section 2; the positive friction soil layer adopts a large-section prefabricated square pile 3. The large-section prefabricated square pile 3 has a significant disturbance to the upper soil layer during the pile sinking process. It is conservatively assumed that the soil layer of the enlarged head section 2 does not provide lateral resistance to the pile body after being disturbed, and the corresponding soil layer is defined as a zero friction soil layer. The small-section prefabricated square pile 1 and its enlarged head section 2 and the large-section prefabricated square pile 3 are prefabricated as a whole in the factory. The side length of the small-section prefabricated square pile 1 is d (mm), the side length of the large-section prefabricated square pile 3 is D (mm), and the top of the enlarged head section 2 is flush with the neutral point.

[0043] like Figure 2-3 As shown, the pile top structure of the large cross-section prefabricated square pile 3 is the same as that of the prior art. In order to better illustrate the implementation method, this case introduces it. The large cross-section prefabricated square pile 3 is built with a lower pile top embedded steel plate 31, a lower side embedded steel plate 32 and a lower pile body main reinforcement 36; the lower pile top embedded steel plate 31 has a thickness of 10 mm and a side length of (D-25) mm; the lower anchor bar 34 extends downward from the bottom wall of the lower pile top embedded steel plate 31, and the lower anchor bar 34 is The length of the lower anchor bar 34 is 770 mm; the lower side embedded steel plate 32 is welded to the lower pile top embedded steel plate 31 and the equilateral angle steel 33 embedded in the four corners. The thickness of the lower side embedded steel plate 32 is 10 mm, the height is 240 mm, and the length is (D-45) mm; the lower reinforcing steel bar 35 is welded between the two opposing lower side embedded steel plates 32. The lower reinforcing steel bar 35 is The structure is a grid cage; an L-shaped equilateral angle steel 33 is welded between two adjacent lower side embedded steel plates 32, and the equilateral angle steel 33 is L90×8 and 240 mm long; corner pads 37 are welded at both the horizontal and vertical ends of the equilateral angle steel 33, and the corner pads 37 are The length is 140mm, and the two sets of corner pads 37 are welded together to the same lower pile main reinforcement 36; the middle pad 38 is welded to the middle of the lower side embedded steel plate 32, and the middle pad 38 is The length is 140 mm, and part of the lower pile main reinforcement 36 is welded to the middle pad reinforcement 38 to form a whole.

[0044] like Figure 5-6 As shown, the bottom cross-section of the enlarged head section 2 has a side length of (D-5) mm, the top cross-section has a side length of d (mm), and the slope is 1:3; the enlarged head section 2 has a middle bottom embedded steel plate 21 and a middle side embedded steel plate 22; the middle bottom embedded steel plate 21 has a thickness of 10 mm and a side length of (D-25) mm; the middle side embedded steel plate 22 has a thickness of 10 mm and is a trapezoidal plate, as shown in FIG. Figure 7 As shown; the middle side embedded steel plate 22 is welded to each edge line of the top of the middle bottom embedded steel plate 21; the top of the middle bottom embedded steel plate 21 is welded with a middle anchor bar 24, and the middle anchor bar 24 is The anchor bar length is 770 mm, and the middle anchor bar 24 extends upward to the inside of the small-section prefabricated square pile 1; a reinforcing steel bar 26 is welded between the two opposing middle side embedded steel plates 22, and the reinforcing steel bar 26 is The bottom embedded steel plate 21 and the side embedded steel plate 22 are welded with a stiffening plate 23, the thickness of the stiffening plate 23 is 10mm, such as Figure 8 As shown, the stiffening plate 23 is connected to the middle bottom embedded steel plate 21 and the middle side embedded steel plate 22 by double-sided fillet welds, and the weld foot size is 10 mm; the reinforcing steel bar 26 is connected to the middle side embedded steel plate 22 and the stiffening plate 23 by welds;

[0045] The reinforcing steel bar 25 of the enlarged head section 2 is The anchoring length of the small-section prefabricated square pile 1 is 770 mm, the reinforcing steel bar 25 is arranged parallel to the plane of the embedded steel plate 22 at the middle side, and the thickness of the protective layer between the reinforcing steel bar 25 and the side of the enlarged head section 2 is 50 mm. The reinforcing steel bar 25 is welded to the stiffening plate 23, and the upper end of the reinforcing steel bar 25 extends to the inside of the small-section prefabricated square pile 1;

[0046] The small-section prefabricated square pile 1 has a middle pile body main reinforcement 27 therein, and the middle pile body main reinforcement 27 extends downward to the inside of the enlarged head section 2 .

[0047] like Figure 4 As shown, the connection between the enlarged head section 2 and the large-section prefabricated square pile 3 is welded. The connecting steel plate 4 is a folded plate with a thickness of 10 mm. The two bent ends of the connecting steel plate 4 are respectively welded to the outer walls of the middle side embedded steel plate 22 and the lower side embedded steel plate 32; the vertical projection height of the connecting steel plate 4 on the enlarged head section 2 and the large-section prefabricated square pile 3 is 200 mm, and the width is 120 mm. The connecting steel plate 4 and the middle side embedded steel plate 22 and the lower side embedded steel plate 32 are all welded on all four sides, and the weld leg size is 10 mm.

[0048] Estimation of savings in pile foundation engineering and reduction in pull-down load caused by negative friction:

[0049] The depth of the negative friction layer is h1(m), the standard value of the weighted negative friction of the negative friction layer is q1(kPa), and the side lengths of the small-section prefabricated square pile 1 and the large-section prefabricated square pile 3 are d(mm) and D(mm) respectively. Compared with the scheme of using large-section prefabricated square piles 3 for the entire height, the savings of the pile foundation engineering can be roughly estimated by adopting this scheme. 3 ), the reduction of the downward pull load caused by negative friction (excluding the slight effect of the enlarged header):

[0050] Δ=(D 2 -d 2 )h1×10 -6 (m 3 )

[0051]

[0052] Assuming that the side length of the small-section prefabricated square pile is d = 300mm, the side length of the large-section prefabricated square pile is D = 300mm, the depth of the negative friction layer is h1 = 10m, and the weighted negative friction standard value of the negative friction layer is q1 = 30kPa, the saving of a single square pile can be calculated as Δ = 1.6m 3 , the reduction of the pull-down load caused by negative friction The benefits are significant.

[0053] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A special-shaped prefabricated square pile capable of reducing the influence of negative friction, characterized in that: It comprises a small-section prefabricated square pile (1), an enlarged head section (2) and a large-section prefabricated square pile (3) which are sequentially connected from top to bottom; The large-section prefabricated square pile (3) is smoothly transitioned to the small-section prefabricated square pile (1) by gradually shrinking the area of ​​the enlarged head section (2); The small-section prefabricated square piles (1) are arranged in a negative friction soil layer above the neutral point.

2. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 1, characterized in that: The enlarged head section (2) is arranged in a zero-friction soil layer below the neutral point, and the top of the enlarged head section (2) is flush with the neutral point; the large-section prefabricated square pile (3) is arranged in a positive-friction soil layer.

3. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 1, characterized in that: The side length of the large-section prefabricated square pile (3) is D, mm; the large-section prefabricated square pile (3) has a built-in lower pile top embedded steel plate (31) and a lower side embedded steel plate (32) arranged at the lower periphery of the lower pile top embedded steel plate (31).

4. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 3, characterized in that: The large-section prefabricated square pile (3) is internally provided with a lower pile body main reinforcement (36), and the inner wall of the lower pile top embedded steel plate (31) is provided with a lower anchor reinforcement (34), and the lower anchor reinforcement (34) is A lower reinforcing steel bar (35) is arranged between the two opposite lower side embedded steel plates (32), and the lower reinforcing steel bar (35) is provided at the upper and lower layers.

5. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 4, characterized in that: An equilateral angle steel (33) is arranged between the inner sides of the adjacent lower side embedded steel plates (32), and a corner pad steel (37) is arranged on the equilateral angle steel (33), and the corner pad steel (37) is welded to the lower pile body main reinforcement (36) to form an integral whole, and the corner pad steel (37) is A middle pad rib (38) is welded to the middle of the inner wall of the lower side embedded steel plate (32), and the middle pad rib (38) is 6. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 3, characterized in that: The bottom cross-section of the enlarged head section (2) has a side length of D-5, mm; the top cross-section has a side length of d, mm; the slope is 1:3; the side length of the small cross-section prefabricated square pile (1) is d, mm; The enlarged head section (2) is internally provided with a middle bottom embedded steel plate (21) and a middle side embedded steel plate (22) arranged on the periphery of the middle bottom embedded steel plate (21); the middle side embedded steel plate (22) is a trapezoidal plate.

7. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 6, characterized in that: A reinforcing steel bar (26) is arranged between the two opposing middle side embedded steel plates (22), and the reinforcing steel bar (26) is provided on the upper and lower layers. A stiffening plate (23) is arranged between the middle bottom embedded steel plate (21) and the middle side embedded steel plate (22), and the reinforcing steel bar (26) is welded to the middle side embedded steel plate (22) and the stiffening plate (23).

8. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 7, characterized in that: The small-section prefabricated square pile (1) is internally provided with reinforcing steel bars (25) and middle pile body main bars (27); the reinforcing steel bars (25) extend obliquely into the enlarged head section (2) and are welded to the stiffening plate (23); and the middle pile body main bars (27) extend vertically into the enlarged head section (2).

9. The special-shaped prefabricated square pile capable of reducing the influence of negative friction according to claim 6, characterized in that: It also includes a plurality of groups of connecting steel plates (4) of folded plate structure, wherein the connecting steel plates (4) are welded to the outer side walls of the middle side embedded steel plates (22) and the lower side embedded steel plates (32).

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