Precast pile, composite foundation pile thereof and construction method

Abstract

The invention provides a precast pile which comprises a first pile body and a second pile body, and the two ends, in the length direction, of the first pile body are the first end and the second end correspondingly; the annular thickened protrusions are fixed to the peripheral wall of the first pile body and arranged in the length direction of the first pile body at intervals; the first pile body comprises a first pile section and a second pile section, the second pile section is provided with densified annular thickened protrusions, a plurality of prestressed steel bars and spiral stirrups extending in the length direction are arranged in the two pile bodies, and the second pile section is provided with densified spiral stirrups with smaller corresponding screw pitches. Further, the invention provides a composite foundation pile formed based on the precast pile as a bottom pile and a construction method. By means of the scheme, the bearing capacity of the pile end can be enhanced, particularly when the pile end is used as a bottom pile of a composite foundation pile, the bearing capacity of the pile end at the bottom can be evenly dispersed through the densified annular thickening protrusions and the densified spiral stirrups, pile section stress concentration is prevented, and the bearing capacity limit of a pile body is improved.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation construction, and in particular to a prefabricated pile and a composite foundation pile thereof and a construction method. Background Art

[0002] With the increase in urban building density, more and more pile foundation construction projects, both new and expanded, need to reduce or even eliminate the impact of soil squeezing on the surrounding environment, which has also led to the development of implanted pile technology. Implanted pile technology was early applied to my country's coastal soft soil areas. After drilling, the soil in the hole needs to be stirred and liquefied, and then the pile is driven into the soil. At this time, the liquid level in the hole rises and is partially discharged, which will not produce soil squeezing effect. Therefore, the implantation method is very suitable for soft soil foundations.

[0003] Under the existing construction process of implanted piles, there are two failure interfaces in the pile body under the vertical load, namely, the interface S1 between the core pile 7 and the concrete 6 around the pile, and the interface S2 between the concrete 6 around the pile and the original soil 5 around the hole wall. Figure 1 As shown. According to the bearing capacity calculation formula, Q uk =u∑ξ si q sik l i +q pk A p Only by simultaneously increasing the limit friction resistance of the above two failure interfaces S1 and S2 can the single pile bearing capacity of the implanted pile be effectively improved.

[0004] In order to improve the single pile bearing capacity of the implanted pile, bamboo piles were developed on the basis of conventional pipe piles. They are a special-shaped pipe pile, see patent CN2611433Y. The bamboo pile has "bamboo nodes" protruding from the pile body at intervals, so it is also called bamboo pile. Unlike pipe piles, bamboo piles are difficult to cast on site. Although some literature points out that cast-in-place piles can also be made into a shape similar to bamboo piles, the bamboo piles formed by casting are significantly different from prefabricated bamboo piles in size, surface burrs and bearing performance due to the uncertainty of drilling technology and foundation construction conditions. The two cannot be confused. The technology of forming special-shaped piles similar to bamboo piles by casting has no reference and reference significance in the production and construction of prefabricated bamboo piles, and in addition to production tests in the industry, there have been no actual construction projects of cast-in-place bamboo piles. Prefabricated bamboo piles are very suitable for implantation construction. When traditional static pressure and hammering methods are applied to bamboo piles, the soil squeezing effect is very prominent. When the implantation method is used for construction, since the diameter of the drill hole is larger than the bamboo part, the bamboo pile can be sent into the foundation in a "non-soil squeezing" manner. After the bamboo piles are combined with the pile perimeter concrete 6, the pile perimeter concrete 6 not only contacts the pile body, but also contacts the bamboo surface, effectively increasing the peak shear stress of the interface S1. Compared with ordinary prefabricated piles of the same diameter, the interface S1 between the pile perimeter concrete 6 and the core pile 7 is less prone to damage. When the implantation method is used for construction, although the bamboo section setting of the existing bamboo piles is conducive to improving the friction force and thus exerting a better bearing capacity, its bearing capacity still has room for improvement. Summary of the invention

[0005] The technical problem to be solved by the present application is how to improve the bearing capacity of the pile end. In view of this, the present application provides a prefabricated pile and a foundation composite pile and a construction method thereof.

[0006] In a first aspect, the present invention discloses a prefabricated pile, comprising: a first pile body, wherein the two ends of the first pile body extending in a straight line along the length direction are respectively a first end and a second end; a plurality of annular thickened protrusions fixed on the outer peripheral wall of the first pile body and arranged at intervals along the length direction of the first pile body; and the first pile body comprises a first pile segment and a second pile segment, wherein the first pile segment extends from the first end to the second pile segment; the spacing between the annular thickened protrusions on the first pile segment is defined as L1 cm, the spacing between the annular thickened protrusions on the second pile segment is defined as L2 cm, and the relationship between L1 and L2 satisfies L2-L1=[30, 70], and L2 = [80, 90]; the first pile body has a plurality of prestressed steel bars extending along the length direction, the prestressed steel bars are evenly arranged in the cross section of the first pile body, the first pile body also has spiral stirrups fixed to the prestressed steel bars and spirally arranged from the first end to the second end, and the spiral stirrups have dense spiral stirrups with a pitch of d1 cm in the first pile segment, and have non-densified spiral stirrups with a pitch of d2 cm in the second pile segment, wherein d1 < d2, and 0.5 < d1 / d2 < 0.75; the length of the dense spiral stirrups extending along the length direction is less than or equal to the length of the first pile segment.

[0007] In a preferred embodiment, the dimension of the annular thickened protrusion along the length direction is defined as L cm, wherein L2-2*L1≤L≤L1. In a further preferred embodiment, L2 is 82.5±5, L1 is 32.5±5, and L is 17.5±5. In a further preferred embodiment, the height of the annular thickened protrusion protruding from the outer peripheral surface of the first pile body is defined as h cm, wherein h is L / 7±0.5.

[0008] In a preferred embodiment, the dimension of the annular thickened protrusion along the length direction is defined as L centimeters, and 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2.

[0009] In a preferred embodiment, the first pile body is a hollow tubular structure, and an end sealing plate is installed at the first end of the first pile body, and the end sealing plate seals the opening of the hollow tubular structure at the first end. In a further preferred embodiment, the end sealing plate has a through hole connected to the internal cavity of the hollow tubular structure.

[0010] In a preferred embodiment, at least one of the annular thickened protrusions on the first pile segment has a through portion that penetrates in the length direction. In a further preferred embodiment, the through portions are two or more symmetrically arranged on both sides of the annular thickened protrusion perpendicular to the length direction, and the through portions are through grooves or through holes.

[0011] In a preferred embodiment, the first pile body includes a third pile segment, the third pile segment has dense spiral stirrups, the third pile segment extends from the second end to the second pile segment, and the third pile segment is symmetrically arranged with the first pile segment.

[0012] In a second aspect, the present invention discloses a composite foundation pile using any one of the aforementioned series of precast piles, wherein the composite foundation pile is vertically arranged and is composed of at least two precast piles combined along the length direction, and the outer periphery of the at least two precast piles is wrapped with solidified concrete; the approximate outer diameter of the composite foundation pile is D1 cm, and the outer diameter of the annular thickened protrusion is D2 cm, and D1 and D2 satisfy: when D2≤60, 5≤D1-D2≤10, and when D2>60, 10≤D1-D2≤15.

[0013] In a preferred embodiment, the bottom of the composite foundation pile has a pile end expansion portion, and the first pile section of the prefabricated pile is provided at the geometric center of the pile end expansion portion. The outer diameter of the pile end expansion portion is approximately D3 cm, and D1, D2 and D3 satisfy: 1.45≤D3 / D1≤1.55, and 5≤D1-D2≤10.

[0014] In a preferred embodiment, the bottom of the composite foundation pile has a pile end expansion portion, the geometric center of the pile end expansion portion has a first pile segment of the prefabricated pile, the height of the pile end expansion portion is greater than or equal to 210 cm and less than or equal to 360 cm, wherein the first pile segment has at least 4 annular thickened protrusions in the pile end expansion portion. In a further preferred embodiment, the height of the pile end expansion portion is greater than or equal to 240 cm and less than or equal to 320 cm, wherein the first pile segment has 5 annular thickened protrusions in the pile end expansion portion.

[0015] In a preferred embodiment, the composite foundation pile is of a uniform outer diameter structure, a prefabricated pile is provided at the geometric center of the composite foundation pile, and D1 and D2 satisfy: 10≤D1-D2≤15.

[0016] In a third aspect, the present invention further discloses a construction method using any one of the aforementioned series of precast piles, which comprises the following steps: vertical drilling: the diameter of the borehole is D1' cm, the outer diameter of the annular thickened protrusion is D2 cm, and the D1' and D2 satisfy: when D2≤60, 5≤D1'-D2≤10, when D2>60, 10≤D1'-D2≤15; grouting: injecting concrete slurry to be cured into the borehole; piling: placing the precast pile into the borehole with the first pile section facing downward.

[0017] In a preferred embodiment, the vertical drilling includes expanding the diameter of the borehole at the bottom of the borehole to obtain an expanded diameter drilling portion, and the first pile section of the prefabricated pile is arranged at the geometric center of the expanded diameter drilling portion. The diameter of the expanded diameter drilling portion is D3' centimeters, and D1', D2 and D3' satisfy: 1.45≤D3' / D1'≤1.55, and 5≤D1'-D2≤10.

[0018] In a preferred embodiment, the vertical drilling includes expanding the diameter of the borehole at the bottom to obtain an expanded diameter drilling portion, the expanded diameter drilling portion has a first pile section of the prefabricated pile at the geometric center, the expanded diameter drilling portion has a height greater than or equal to 210 cm and less than or equal to 360 cm, wherein the first pile section (101) has at least 4 annular thickened protrusions (11) in the expanded diameter drilling portion. In a further preferred embodiment, the expanded diameter drilling portion has a height greater than or equal to 240 cm and less than or equal to 320 cm, wherein the first pile section (101) has 5 annular thickened protrusions (11) in the expanded diameter drilling portion.

[0019] In a preferred embodiment, the borehole is of uniform diameter as a whole, a prefabricated pile (1) is provided at the geometric center of the borehole, and D1' and D2 satisfy: 10≤D1'-D2≤15. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a bearing capacity analysis diagram of the implantation construction in the prior art;

[0021] Figure 2 This is a schematic diagram of the structure of the prefabricated pile embodiment 1 of the present application;

[0022] Figure 3 A schematic diagram of the size identification and an enlarged diagram of the annular thickened protrusion structure of the prefabricated pile embodiment 1 of the present application;

[0023] Figure 4 This is a schematic diagram of the cage reinforcement structure of the prefabricated pile embodiment 1 of the present application;

[0024] Figure 5 A schematic diagram of the three-dimensional structure and the through-portion structure of another prefabricated pile embodiment of the present application;

[0025] Figure 6 A schematic diagram of the three-dimensional structure and end sealing plate structure of another prefabricated pile embodiment of the present application;

[0026] Figure 7 A schematic diagram of the structure of another prefabricated pile embodiment of the present application and a schematic diagram of the stirrup structure;

[0027] Figure 8 This is a schematic diagram of the structure of other embodiments of the prefabricated piles of the present application;

[0028] Fig. 9 This is a schematic diagram of the structure of other embodiments of the prefabricated piles of the present application;

[0029] Fig.10 This is a schematic diagram of the construction method embodiment 1 of the present application and the composite foundation pile structure formed;

[0030] Fig.11 This is a schematic diagram of the construction method embodiment 2 of the present application and the composite foundation pile structure formed;

[0031] 1. Precast pile; 2. End plate; 21. End sealing plate; 3. Steel cage; 31. Prestressed steel bar; 32. Spiral stirrup; 10. First pile body; 10", first end; 10', second end; 11. Annular thickened protrusion; 110. Through-hole; 101. First pile section; 102. Second pile section; 103. Third pile section; 1000', drill hole; 1000, composite foundation pile; 6', concrete slurry; 5. Original soil; 6. Pile surrounding concrete; 7. Core pile; 1002. Pile end expansion; DETAILED DESCRIPTION

[0032] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0033] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0034] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0035] The following is combined with Figure 2 to Figure 11 The present application is further described in detail with specific embodiments.

[0036] Prefabricated pile embodiment 1

[0037] See also Figure 2 to Figure 4 As shown, Example 1 of the present application discloses a prefabricated pile 1. The prefabricated pile 1 comprises: a first pile body 10, wherein the two ends of the first pile body 10 extending in a straight line along the length direction are respectively a first end 10" and a second end 10'; a plurality of annular thickened protrusions 11, which are fixed on the outer peripheral wall of the first pile body 10 and are arranged at intervals along the length direction of the first pile body 10; and the first pile body comprises a first pile segment 101 and a second pile segment 102, wherein the first pile segment 101 extends from the first end 10" to the second pile segment 102; it should be additionally pointed out that the first pile segment 101 and the second pile segment 102 may have a common annular thickened protrusion 11 at the intersection, such as Figure 2 As shown; the spacing between the annular thickened protrusions 11 on the first pile segment 101 is defined as L1 cm, the spacing between the annular thickened protrusions 11 on the second pile segment is defined as L2 cm, the relationship between L1 and L2 satisfies L2-L1=[30,70], and L2=[80,90]; the first pile body 10 of the precast pile 1 has a steel cage 3, wherein the steel cage 3 includes a plurality of prestressed steel bars 31 extending in the length direction and spiral stirrups 32 spirally wound and fixed on the prestressed steel bars 31, as shown Figure 4 As shown, the prestressed steel bars 31 are evenly arranged in the cross section of the first pile body 10, and the first pile body 10 also has spiral stirrups 32 fixed to the prestressed steel bars 31 and spirally arranged from the first end 10" to the second end 10', and the spiral stirrups 32 have dense spiral stirrups with a pitch of d1 cm in the first pile segment 101, and have non-densified spiral stirrups with a pitch of d2 cm in the second pile segment 102, wherein d1 < d2, and 0.5 < d1 / d2 < 0.75, and the length of the dense spiral stirrups extending along the length direction is less than or equal to the length of the first pile segment 101. As Example 1 The exemplary pile body structure dimensions are as follows: for example, the pitch of the dense spiral stirrup is d1=4.5 cm, the pitch of the non-densified spiral stirrup is d2=8.5 cm, the spacing between the annular thickened protrusions 11 on the second pile 102 is L2=82.5 cm, the spacing between the annular thickened protrusions 11 on the first pile section 101 is L1=32.5 cm, the dimension of the annular thickened protrusions 11 along the length direction is L=17.5 cm, the height of the annular thickened protrusions 11 protruding from the outer circumference of the first pile body 10 is h=2.5 cm, the outer diameter of the annular thickened protrusions 11 is 60 cm, and the outer diameter of the first pile body 10 is 55 cm. Figure 2-4 The precast pile 1 shown may be formed by using common prestressed precast piles, and may further include end plates 2 located at a first end 10 ″ and a second end 10 ′ of the first pile body 10 .

[0038] Since the first pile section 101 of the prefabricated pile disclosed in the present invention is provided with more densely packed annular thickened protrusions 11 biased toward the first end 10", it is easier to disperse the pressure that the end face of the first end 10" needs to bear in the soil than conventional bamboo piles, thereby improving the bearing limit of the pile end of the bamboo pile. In a specific setting, the spacing between the annular thickened protrusions 11 on the non-encrypted second pile segment is L2=[80, 90], which is more suitable for matching with the underground soil layer structure, and on this basis, the spacing between the annular thickened protrusions 11 on the first pile segment 101 is L1 cm to satisfy L2-L1=[30, 70]. The spiral stirrups in the precast pile 1 have encrypted spiral stirrups with a pitch of d1 cm in the first pile segment 101, and the length of the encrypted spiral stirrups extending along the length direction is less than or equal to the length of the first pile segment 101. Therefore, on the basis of dispersing the pressure borne by the pile end face by encrypting the annular thickened protrusions 11 at the pile end, the part is further laterally strengthened by the encrypted stirrups to facilitate the transmission of the force of each part of the outer peripheral surface of the first pile segment 101, so that the end bearing pressure is more evenly transmitted through the outer peripheral pressure bearing surface of the first pile segment 101.

[0039] Based on prefabricated pile embodiment 1, in other embodiments, the pitch d1 of the dense spiral stirrups can be selected from 4.0, 4.5, 5.0 cm and any value within the range thereof, the pitch d2 of the non-densified spiral stirrups can be selected from 8.0, 8.5, 9.0 cm and any value within the range thereof, the spacing L2 between the annular thickened protrusions 11 on the second pile segment 102 can be selected from 80, 82.5, 85, 87.5, 90 cm and any value within the range thereof, and the spacing L1 between the annular thickened protrusions 11 on the first pile segment 101 can be set accordingly based on the range of L2-L1=[30,70]. The dimension L of the annular thickened protrusion 11 along the length direction can be selected from 10, 12.5, 15, 17.5, 20, 22.5, 25 cm and any value within the range thereof; the height h of the annular thickened protrusion 11 protruding from the outer circumferential surface of the first pile body 10 can be selected from 2, 2.5, 3 cm and any value within the range thereof. Based on h=2.5 cm, the outer diameter D2 of the annular thickened protrusion 11 is 40, 50, 60, 70, 80 cm and any value within the range thereof, and the corresponding outer diameter of the first pile body 10 is 35, 45, 55, 65, 75 cm and any value within the range thereof.

[0040] Based on the prefabricated pile Example 1, in a more preferred embodiment, the dimension of the annular thickened protrusion 11 along the length direction is further defined as L centimeters, wherein L2-2*L1≤L≤L1. In a further preferred embodiment, L2 is 82.5±5, L1 is 32.5±5, and L is 17.5±5. The above scheme further limits the height of the suitable annular thickened protrusion 11, and optimizes the height of the annular thickened protrusion 11 of different pile sections. Under the above setting, compared with Example 1, the decomposition of the pile end bearing pressure and the setting cost of the annular thickened protrusion are taken into account, and it has better compatibility with the existing bamboo pile production and use process. In a further preferred embodiment, the height of the annular thickened protrusion 11 protruding from the outer peripheral pressure-bearing surface of the first pile body 10 is defined as h centimeters, and h is L / 7±0.5, such as Figure 3 According to the aforementioned length dimension L cm of the annular thickened protrusion 11, the protrusion of the annular thickened protrusion 11 should not be too large. Compared with the embodiment 1, it can avoid that the lateral friction force of the pile body is too concentrated on the annular thickened protrusion 11, causing cracks or falling off between the annular thickened protrusion 11 and the first pile body 10.

[0041] Based on the prefabricated pile embodiment 1, in a more preferred embodiment, the dimension of the annular thickened protrusion along the length direction is further defined as L cm, 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2. It should be noted that in the above settings, if each pile segment has multiple L1, L2, L, d1, d2 with different values, the average value is used for calculation. Based on the above settings, the density gradient of the annular thickened protrusion 11 in the first pile segment 101 and the second pile segment 102 can be coordinated with the bundling density gradient of the stirrup setting. Compared with embodiment 1, it is more convenient for the end bearing pressure to be more evenly transmitted through the outer peripheral bearing surface of the first pile segment 101.

[0042] Based on the prefabricated pile embodiment 1, in a more preferred embodiment, the first pile body 10 is a hollow tubular structure, and the first end 10" of the first pile body 10 is installed with an end sealing plate 21, such as Figure 6 The end sealing plate 21 seals the opening of the hollow tubular structure at the first end 10". In a further preferred embodiment, the end sealing plate 21 has a through hole (not shown) communicating with the inner cavity of the hollow tubular structure. The end sealing plate 21 can be made of Figure 5The perforated end plate 2 shown is formed by sealing the central opening, for example, an end sealing plate 21 is fixed or welded to the end plate 2 with additional bolts; the end sealing plate 21 can also be formed by directly fixing the non-perforated end plate 2 to the bottom of the first pile body 10. Since the end bearing force is evenly distributed and transmitted through the outer peripheral pressure-bearing surface of the first pile segment 101, it is not necessary to fill the interior of the hollow bamboo tube pile with too much concrete slurry or concrete slurry of mixed concrete, which can further save the cost of concrete materials compared to Example 1; and since the concrete slurry or concrete slurry of mixed concrete cannot flow into the interior of the hollow tube pile, the above-mentioned liquid slurry will apply unbalanced pressure to the outer peripheral pressure-bearing surface of the first pile segment 101, which can strengthen the interface bonding force between the solidified concrete and the outer peripheral pressure-bearing surface of the first pile segment 101.

[0043] Based on the prefabricated pile example 1, in a more preferred embodiment, Figure 5 At least one of the annular thickened protrusions 11 on the first pile segment has a through portion 110 that penetrates in the length direction. In a further preferred embodiment, the through portions 110 are two or more symmetrically arranged on both sides of the annular thickened protrusion perpendicular to the length direction. Figure 5 The through groove shown may also be a through hole. Compared with Example 1, the provision of the above-mentioned through portion is further conducive to controlling the drilling diameter of the borehole, so that during the construction process, the injected concrete slurry to be solidified can be transferred from the through portion from bottom to top during the process of placing the precast pile 1, thereby preventing the pile body from sinking to the bottom due to the sealing effect of the annular thickened protrusion 11 on the slurry in the borehole; and the symmetrically arranged through portions can make the slurry overflow at the same speed, thereby avoiding uneven solidification of the concrete around the pile. In addition, the through portion 110 can be set according to the settlement resistance of the precast pile 1 during the specific construction process, for example, in the attached Figure 6 In the embodiment shown, the through-portions are arranged on four annular thickened protrusions 11, and Figure 5 In the embodiment shown in FIG. 1 , the through-holes are arranged on seven annular thickened protrusions 11 .

[0044] Based on the prefabricated pile embodiment 1, in a more preferred embodiment, the first pile body includes a third pile segment 103, such as Figure 7As shown, the third pile segment 103 has dense spiral stirrups, and the third pile segment 103 extends from the second end 10' to the second pile segment 102, and the third pile segment 103 is symmetrically arranged with the first pile segment 101. Compared with Example 1, the symmetrical arrangement can further reduce the additional lifting cost during transportation and installation, and the pile body itself also needs to be reinforced at the pile connection part to avoid the end bearing force of the pile end being completely concentrated on the end surface. The end bearing force in this scheme can be transmitted through the concrete around the pile and the dense annular thickened protrusion 11, and the dense annular thickened protrusion 11 itself also has dense spiral stirrups for transverse reinforcement, which is conducive to the overall bearing capacity of the pile foundation.

[0045] Other Improved Prefabricated Pile Embodiments

[0046] like Figure 8 , 9 Shown are other improved embodiments of the present invention based on the prefabricated pile embodiment 1.

[0047] like Figure 8 As shown, the prefabricated pile 1 of the present invention can set the ratio of the length of the first pile segment 101 to the length of the first pile body 10 according to specific construction requirements, and adjust the setting density of the annular thickened protrusions 11 therein. When the ground holding force is strong, the spacing between adjacent annular thickened protrusions 11 on the first pile segment 101 can be reduced to a certain extent.

[0048] In addition, the overall pile length of the prefabricated pile 1 can be set, and the structures of the first pile segment 101, the second pile end 102, and the third pile end 103 can be set based on the overall pile length, wherein the first pile segment 101 and the third pile end 103 are symmetrical to each other based on the vertical center plane perpendicular to the length direction of the first pile body 10. The above symmetrical structure can decompose the stress of the upper and lower ends of the pile body where the stress is concentrated through the soil or concrete around the pile, so that it will not be concentrated on the end bearing surface of the pile end.

[0049] In addition, the annular thickened protrusions 11 of the first pile segment 101 and the third pile end 103 may be arranged densely and may also be set to an asymmetric structure.

[0050] In addition, the spacing between adjacent annular thickened protrusions 11 on the first pile segment 101 and the third pile end 103 can also be set to be gradual, so that the spacing becomes larger as it is closer to the second pile end 102, so that the bearing pressure is gradually decomposed from the middle of the pile to the pile end, avoiding the excessive concentration of the pile surrounding pressure on the pile surface in a certain length area.

[0051] Another aspect of the present invention provides a construction method based on the above-mentioned prefabricated pile 1.

[0052] Construction method embodiment 1

[0053] As attached Fig.10 As shown in (a), 10(b), and 10(c), as shown in the figure, the construction method embodiment 1 discloses a construction method using the precast pile embodiment 1 and other preferred implementation schemes and improved embodiments based on the precast pile embodiment 1, and the construction method comprises the following steps:

[0054] Vertical drilling: as attached Fig.10 As shown in (a), the outer diameter of the annular thickened protrusion 11 is 60 cm, and the diameter D1' of the borehole 1000 is set to 70 cm. The borehole depth can be set according to the construction requirements, and the surrounding wall of the borehole is the original soil 5 around the hole wall.

[0055] Grouting: injecting concrete slurry 6' to be cured into the borehole; the injected concrete slurry 6' to be cured may be, for example, made by the current static drilling root pile construction method, and stirred while injecting the slurry.

[0056] Piling: placing the prefabricated pile 1 into the drilled hole with the first pile section 101 facing downward.

[0057] According to the prefabricated pile implementation 1, as exemplary pile body structural dimensions of the prefabricated pile 1, for example, the pitch of the dense spiral stirrups is d1=4.5 cm, the pitch of the non-densified spiral stirrups is d2=8.5 cm, the spacing between the annular thickened protrusions 11 on the second pile section 102 is L2=82.5 cm, the spacing between the annular thickened protrusions 11 on the first pile section 101 is L1=32.5 cm, the dimension of the annular thickened protrusions 11 along the length direction is L=17.5 cm, the height of the annular thickened protrusions 11 protruding from the outer peripheral surface of the first pile body 10 is h=2.5 cm, the outer diameter of the annular thickened protrusions (11) is D2=60 cm, and the diameter of the first pile body 10 is D2-2*h=55 cm.

[0058] In the pile planting step, before placing the prefabricated pile 1 into the drill hole, it is necessary to connect the piles at the top of the prefabricated pile 1 according to the depth of the drill hole, wherein another prefabricated pile 1 or other types of prefabricated piles can be used for the connection. Then continue to place the piles. For example, the connection and placement of the piles can be carried out according to the existing static drilling root pile process. The connection of the piles can be welded with the end plates of the prefabricated pile 1 or a plug-in or latch-type structure can be used.

[0059] After connecting and placing piles according to the drilling length, when the combined pile body structure is close to the drilling depth or longer than the drilling depth, the pile connection can be stopped according to the design requirements, and the concrete slurry around the pile is waited for to solidify, so that the concrete 6 around the pile is combined with the precast pile 1 to form a composite foundation pile 1000.

[0060] The composite foundation pile 1000 constructed by the above method has all the effects brought by the above-mentioned prefabricated pile embodiment 1, which will not be repeated here.

[0061] Construction method embodiment 2

[0062] As attached Fig.11 As shown in (a), 11(b), 11(c), and 11(d), compared with construction method example 1, other technical contents of construction method example 2 are the same, and the main difference is that in the drilling step, a bottom expansion drilling is further performed at the bottom of the borehole, wherein the concrete slurry to be cured forms a pile end expansion portion 1002 in the bottom expansion borehole, wherein the size of the bottom expansion borehole is D3'=105 cm, that is, D3' / D1'=1.5.

[0063] This embodiment further enhances the performance of the bearing capacity of the bottom. By expanding the bottom borehole, the first pile segment 101 can be closely combined with the pile end enlargement part 1002 through the encrypted annular thickened protrusion 11, so that the bearing capacity of the encrypted annular thickened protrusion 11 of the first pile segment 101 at the pile end can be fully and evenly exerted, and stress concentration can be avoided at the same time. The settlement resistance can be increased through the pile end enlargement part 1002, thereby preventing the composite foundation pile 1000 from settling in part of the base. When D3' / D1' is too large, the drilling equipment and construction costs are too high, and the performance of increased bearing capacity is redundant. When D3' / D1' is too small, the end bearing capacity is not fully exerted. Therefore, in other embodiments, 1.45≤D3' / D1'≤1.55 is preferred, which can ensure that when the first pile segment 101 has the encrypted annular thickened protrusion 11, the bearing capacity is improved and the cost is saved at the same time.

[0064] Construction method embodiment 3

[0065] As attached Fig.11 As shown in (d), compared with construction method embodiment 2, other technical contents of construction method embodiment 3 are the same, and the main difference is that in the drilling step, the bottom expansion drilling height is set to 2.4 meters covering the four annular thickened protrusions 11.

[0066] This embodiment ensures that the effect of Example 2 is optimized to a certain extent by setting the bottom expansion drilling height to include four annular thickened protrusions 11. Compared with the solution of only two or three annular thickened protrusions 11 combined with the pile end expansion part 1002, the setting of four annular thickened protrusions 11 can more easily ensure the bonding force between the first pile segment 101 and the pile end expansion part 1002.

[0067] Construction method embodiment 4

[0068] As attached Fig.11As shown in (e), compared with the construction method embodiment 3, the other technical contents of the construction method embodiment 4 are the same, and the main difference is that in the drilling step, the bottom expansion drilling height is set to 2.9 meters covering the five annular thickened protrusions 11. This embodiment further strengthens the bonding force between the first pile segment 101 and the pile end enlarged portion 1002.

[0069] Construction method embodiment 5

[0070] Compared with the construction method embodiment 1, the other technical contents of the construction method embodiment 5 are the same, and the main difference is that the borehole is further a constant diameter structure, wherein the diameter of the borehole is D1'=75 cm. This embodiment cancels the pile end expansion part 1002, and is suitable for some geological environments where it is not easy to expand the bottom borehole. By expanding the drill diameter with constant diameter, the bonding force between the prefabricated pile 1 and the concrete around the pile is strengthened, and at the same time, the concrete around the pile can also improve the bearing capacity of the original soil 5 around the hole wall due to the expansion of the diameter.

[0071] Another aspect of the present invention provides a composite foundation pile based on the aforementioned prefabricated pile 1 .

[0072] Composite foundation pile embodiment 1

[0073] According to the aforementioned construction method embodiment 1, Fig.10As shown in Figures 10(a), 10(b), and 10(c), on the basis of the precast pile 1, through the processes of drilling, grouting, and pile planting, a composite foundation pile 1000 with the precast pile 1 as the core pile 7 is finally solidified. The composite foundation pile 1000 is vertically arranged, and the approximate outer diameter of the composite foundation pile 1000 is D1 cm, and it is composed of two precast piles 1 combined along the length direction, and the outer periphery of the two precast piles 1 is wrapped with solidified pile surrounding concrete 6; the approximate outer diameter of the composite foundation pile 1000 is D1 = drilling diameter (D1') = 75 cm, and because the foundation drilling construction itself has errors, the outer peripheral surface of the pile surrounding concrete 6 forms a roughly cylindrical pile shape, and its outer diameter has a certain construction error, and its molding will also cause errors due to the unevenness of the interface S2 peripheral wall between the pile surrounding concrete 6 and the original soil 5 around the hole wall, so that it has a roughly cylindrical structure. The two precast piles 1 inside the composite foundation pile 1000 are, according to the precast pile implementation 1, as exemplary pile body structural dimensions of the precast pile 1, for example, the pitch of the dense spiral stirrups is d1=4.5 cm, the pitch of the non-densified spiral stirrups is d2=8.5 cm, the spacing between the annular thickened protrusions 11 on the second pile 102 section is L2=82.5 cm, the spacing between the annular thickened protrusions 11 on the first pile section 101 is L1=32.5 cm, the dimension of the annular thickened protrusions 11 along the length direction is L=17.5 cm, the height of the annular thickened protrusions 11 protruding from the outer peripheral surface of the first pile body 10 is h=2.5 cm, the outer diameter D2 of the annular thickened protrusions 11 is 60 cm, and the diameter of the first pile body 10 is D2-2*h=55 cm. The foundation treatment pile based on the above composite foundation pile 1000 has all the effects brought by the above-mentioned precast pile implementation 1, which will not be repeated here.

[0074] Composite foundation pile embodiment 2

[0075] As attached Fig.11 As shown in (d), composite foundation pile embodiment 2 is obtained based on construction method embodiment 2. Compared with composite foundation pile embodiment 1, other technical contents of composite foundation pile embodiment 2 are the same. The main difference is that in the construction plan for forming the composite foundation pile, a bottom expansion drilling is further performed in the drilling step of the bottom of the borehole, wherein the concrete slurry to be cured forms a pile end expansion portion 1002 in the bottom expansion borehole, wherein the outer diameter dimension D3 of the pile end expansion portion 1002 is approximately the same as the dimension of the bottom expansion borehole, i.e., D3=D3'=105 cm. The approximate outer diameter of the composite foundation pile 1000 is D1=75 cm, i.e., D3 / D1=1.5.

[0076] The composite foundation pile embodiment 2 further enhances the bearing capacity of the bottom. By expanding the bottom borehole, the first pile segment 101 can be closely combined with the pile end expansion part 1002 through the encrypted annular thickened protrusion 11, so as to fully and evenly exert the bearing capacity of the encrypted annular thickened protrusion 11 of the first pile segment 101 at the pile end, and at the same time avoid stress concentration, and increase the settlement resistance through the pile end expansion part 1002, so as to prevent the composite foundation pile 1000 from settling in part of the base. When D3 / D1 is too large, the drilling equipment and construction costs are too high, and the performance of increased bearing capacity is redundant; when D3 / D1 is too small, the end bearing capacity of the pile end expansion part 1002 is not fully exerted; therefore, in other embodiments, 1.45≤D3 / D1≤1.55 is preferred, which can ensure that the bearing capacity is improved and the cost is saved when the first pile segment 101 has the encrypted annular thickened protrusion 11.

[0077] Composite foundation pile embodiment 3

[0078] As attached Fig.11 As shown in (d), compared with the composite foundation pile embodiment 2, the other technical contents of the composite foundation pile embodiment 3 are the same, and the main difference is that in the drilling step, the bottom expansion drilling height is set to 2.4 meters covering the four annular thickened protrusions 11.

[0079] In composite foundation pile embodiment 3, the bottom expansion drilling height is set to cover four annular thickened protrusions 11. Compared with the solution in which only two or three annular thickened protrusions 11 are combined with the pile end expansion part 1002, the setting of four annular thickened protrusions 11 makes it easier to ensure the bonding force between the first pile segment 101 and the pile end expansion part 1002.

[0080] Composite foundation pile embodiment 4

[0081] As attached Fig.11 As shown in (e), the composite foundation pile embodiment 4 is similar to the composite foundation pile embodiment 3 in other technical contents, and the main difference is that the bottom expansion drilling height is set to 2.9 meters in the drilling step to cover the five annular thickened protrusions 11. This embodiment further strengthens the bonding force between the first pile segment 101 and the pile end enlarged portion 1002.

[0082] Composite foundation pile embodiment 5

[0083] Compared with the composite foundation pile embodiment 1, the composite foundation pile embodiment 5 has the same technical contents, and the main difference is that the borehole is further a constant diameter structure, wherein the diameter of the borehole is D1'=75 cm, so that the outer diameter of the composite foundation pile is approximately D1=75 cm. This embodiment cancels the pile end expansion part 1002, and is suitable for certain geological environments where it is not easy to expand the bottom drilling. By expanding the drill diameter with constant diameter, the bonding force between the prefabricated pile 1 and the pile surrounding concrete 6 is strengthened, and at the same time, the pile surrounding concrete 6 can also improve the bearing capacity of the original soil 5 around the hole wall due to the expansion of the diameter.

[0084] In addition to the above-mentioned construction method embodiments 1-5 and composite foundation pile embodiments 1-5, the present application also discloses a more preferred implementation scheme based on precast pile 1 and other improved construction methods of other improved embodiments and corresponding composite foundation piles. Those skilled in the art can be aware of the above-mentioned schemes, and can form other undetailed precast pile schemes based on all the contents disclosed in the above-mentioned precast pile 1 embodiment and their combinations to implement construction and composite foundation piles, which will not be repeated here.

[0085] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0086] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0087] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A prefabricated pile (1), characterized in that: include: A first pile body (10), wherein two ends of the first pile body (10) extending in a straight line along the length direction are respectively a first end (10") and a second end (10'); A plurality of annular thickened protrusions (11) fixed on the outer peripheral wall of the first pile body (10) and arranged at intervals along the length direction of the first pile body (10); and The first pile body comprises a first pile segment (101) and a second pile segment (102), wherein the first pile segment (101) extends from a first end (10") to the second pile segment (102); The spacing between the annular thickened protrusions (11) on the first pile segment (101) is defined as L1 centimeters, and the spacing between the annular thickened protrusions (11) on the second pile segment is defined as L2 centimeters, and the relationship between L1 and L2 satisfies L2-L1=[30,70], and L2=[80,90]; The first pile body (10) has a plurality of prestressed steel bars extending in the length direction, the prestressed steel bars being evenly arranged in the cross section of the first pile body (10), and the first pile body (10) also has spiral stirrups fixed to the prestressed steel bars and spirally arranged from the first end (10") to the second end (10'), and the spiral stirrups have dense spiral stirrups with a pitch of d1 cm in the first pile segment (101), and have non-dense spiral stirrups with a pitch of d2 cm in the second pile segment (102), wherein d1<d2, and 0.5<d1 / d2<0.75; the length of the dense spiral stirrups extending in the length direction is less than or equal to the length of the first pile segment (101).

2. The prefabricated pile (1) according to claim 1, characterized in that: The dimension of the annular thickened protrusion (11) along the length direction is defined as L centimeters, wherein L2-2*L1≤L≤L1.

3. The prefabricated pile (1) according to claim 2, characterized in that: L2 is 82.5±5, L1 is 32.5±5, and L is 17.5±5.

4. The prefabricated pile (1) according to claim 3, characterized in that: The height of the annular thickened protrusion (11) protruding from the outer peripheral surface of the first pile body (10) is defined as h centimeters, where h is L / 7±0.

5.

5. The prefabricated pile (1) according to claim 3, characterized in that: The dimension of the annular thickened protrusion (11) along the length direction is defined as L centimeters, and 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2.

6. The prefabricated pile (1) according to claim 1, characterized in that: The first pile body (10) is a hollow tubular structure, and an end sealing plate is installed at the first end (10") of the first pile body (10), and the end sealing plate seals the opening of the hollow tubular structure at the first end (10").

7. The prefabricated pile (1) according to claim 6, characterized in that: The end sealing plate is provided with a through hole communicating with the inner cavity of the hollow tubular structure.

8. The prefabricated pile (1) according to claim 1, characterized in that: At least one of the annular thickened protrusions (11) on the first pile segment (101) has a through portion that penetrates in the length direction.

9. The prefabricated pile (1) according to claim 8, characterized in that: The through-portions are two or more symmetrically arranged on two sides of the annular thickened protrusion (11) perpendicular to the length direction, and the through-portions are through-grooves or through-holes.

10. The prefabricated pile (1) according to any one of claims 1 to 9, characterized in that: The first pile body (10) comprises a third pile segment (103) having dense spiral stirrups, the third pile segment (103) extending from the second end (10') to the second pile segment (102), and the third pile segment (103) is symmetrically arranged with the first pile segment (101).

11. A composite foundation pile using the prefabricated pile (1) according to any one of claims 1 to 10, characterized in that: The composite foundation pile is vertically arranged and is composed of at least two prefabricated piles (1) combined along the length direction, and the outer circumference of the at least two prefabricated piles (1) is wrapped with solidified concrete; the approximate outer diameter of the composite foundation pile is D1 cm, and the outer diameter of the annular thickened protrusion (11) is D2 cm, and D1 and D2 satisfy: when D2≤60, 5≤D1-D2≤10, and when D2>60, 10≤D1-D2≤15.

12. The composite foundation pile according to claim 11, characterized in that: The bottom of the composite foundation pile has a pile end expansion portion, and the first pile section (101) of the prefabricated pile (1) is located at the geometric center of the pile end expansion portion. The outer diameter of the pile end expansion portion is approximately D3 cm, and D1, D2 and D3 satisfy: 1.45≤D3 / D1≤1.55, and 5≤D1-D2≤10.

13. The composite foundation pile according to claim 11, characterized in that: The bottom of the composite foundation pile has a pile end expansion portion, and the geometric center of the pile end expansion portion has a first pile section (101) of the prefabricated pile (1), the height of the pile end expansion portion is greater than or equal to 210 cm and less than or equal to 360 cm, wherein the first pile section (101) has at least 4 annular thickened protrusions (11) in the pile end expansion portion.

14. The composite foundation pile according to claim 13, characterized in that: The height of the pile end enlarged portion is greater than or equal to 240 centimeters and less than or equal to 320 centimeters, wherein the first pile section (101) has five annular thickened protrusions (11) in the pile end enlarged portion.

15. The composite foundation pile according to claim 11, characterized in that: The composite foundation pile is of a uniform outer diameter structure, and a prefabricated pile (1) is provided at the geometric center of the composite foundation pile, and D1 and D2 satisfy: 10≤D1-D2≤15.

16. A construction method using the prefabricated pile (1) according to any one of claims 1 to 10, characterized in that: The following steps are involved: Vertical drilling: the diameter of the drilling hole is D1' cm, the outer diameter of the annular thickened protrusion (11) is D2 cm, and D1' and D2 satisfy: when D2≤60, 5≤D1'-D2≤10, when D2>60, 10≤D1'-D2≤15; Grouting: injecting concrete slurry to be cured into the drilled hole; Piling: placing the prefabricated pile (1) into the drilled hole with the first pile section (101) facing downwards.

17. The construction method according to claim 16, characterized in that: The vertical drilling includes expanding the diameter of the borehole at the bottom to obtain an expanded diameter drilling portion, and the first pile section (101) of the prefabricated pile (1) is arranged at the geometric center of the expanded diameter drilling portion. The diameter of the expanded diameter drilling portion is D3' centimeters, and D1', D2 and D3' satisfy: 1.45≤D3' / D1'≤1.55, and 5≤D1'-D2≤10.

18. The construction method according to claim 16, characterized in that: The vertical drilling comprises expanding the diameter of the borehole at the bottom to obtain an expanded diameter drilling portion, wherein the geometric center of the expanded diameter drilling portion has a first pile section (101) of a prefabricated pile (1), and the height of the expanded diameter drilling portion is greater than or equal to 210 cm and less than or equal to 360 cm, wherein the first pile section (101) has at least 4 annular thickened protrusions (11) in the expanded diameter drilling portion.

19. The construction method according to claim 18, characterized in that: The height of the expanded diameter drilling portion is greater than or equal to 240 centimeters and less than or equal to 320 centimeters, wherein the first pile section (101) has five annular thickened protrusions (11) in the expanded diameter drilling portion.

20. The construction method according to claim 16, characterized in that: The borehole as a whole is of equal diameter structure, a prefabricated pile (1) is provided at the geometric center of the borehole, and D1' and D2 satisfy: 10≤D1'-D2≤15.

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