Precast pile and composite foundation pile thereof

Abstract

The utility model provides a precast pile and a composite foundation pile thereof, and relates to the technical field of pile foundation construction. The precast pile comprises a first pile body and a second pile body, wherein 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 outer diameter of each annular thickened protrusion (11) is D2 cm, and D2 is larger than or equal to 40 and smaller than or equal to 80; the first pile body comprises a first pile section (101) and a second pile section (102), and the first pile section (101) extends from a first end (10 '') to the second pile section (102); the distance between the annular thickened protrusions (11) on the first pile section (101) is L1 cm, the distance between the annular thickened protrusions (11) on the second pile section is L2 cm, and the relation between L1 and L2 meets the conditions that L2-L1 = [30, 70], and L2 = [80, 90]. A plurality of prestressed steel bars extending in the length direction are arranged in the first pile body (10), the prestressed steel bars are evenly distributed on the cross section of the first pile body (10), and spiral stirrups which are fixed to the prestressed steel bars and spirally distributed from the first end (10 '') to the second end (10 ') are further arranged in the first pile body (10). The spiral stirrups are provided with dense spiral stirrups with the screw pitch of d1cm in the first pile section (101) and non-dense spiral stirrups with the screw pitch of d2cm in the second pile section (102), and d1 is smaller than d2; the extending length of the dense spiral stirrup in the length direction is smaller than or equal to the length of the first pile section (101).

Description

Technical Field

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

[0002] With the increasing density of urban buildings, pile foundation construction in a growing number of new construction and renovation projects is increasingly demanding the reduction or even elimination of soil extrusion impacts on the surrounding environment. This has driven the development of embedded pile technology. Early applications of embedded pile technology were in my country's coastal soft soil areas. After drilling, embedded pile construction involves mixing and liquefying the soil within the hole before driving the pile into the ground. This process causes the liquid level within the hole to rise and partially drain, eliminating soil extrusion. Therefore, the embedded pile method is well-suited for soft soil foundations.

[0003] Under the existing construction technology of embedded piles, there are two failure interfaces in the pile body under the action of 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 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. This is a special-shaped pipe pile, see patent CN2611433Y. The bamboo pile body has "bamboo nodes" protruding from the pile body surface at intervals, so it is also called a bamboo pile. Unlike pipe piles, bamboo piles are difficult to cast on site. Although some literature indicates that cast-in-place piles can also be made into shapes similar to bamboo piles, whether it is the drilling technology or the uncertainty of foundation construction conditions, the bamboo piles formed by casting are significantly different from prefabricated bamboo piles in size, surface burrs and bearing performance. 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. In addition, except for 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. However, when using the implantation construction method, 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 surface of the bamboo, 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 using the implantation construction method, although the bamboo arrangement of the existing bamboo piles is conducive to improving the friction force and thus exerting better bearing capacity, its bearing capacity still has room for improvement. Utility Model Content

[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 combination pile thereof.

[0006] In a first aspect, the utility model 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 spaced apart along the length direction of the first pile body, wherein the outer diameter of the annular thickened protrusion (11) is D2 cm, wherein 40≤D2≤80; 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, and the spacing between the annular thickened protrusions on the second pile segment is defined as L2 cm. cm, the relationship between L1 and L2 satisfies L2-L1=[30,70], and L2=[80,90]; the first pile body comprises a plurality of prestressed steel bars extending along the length, the prestressed steel bars being evenly arranged across the cross section of the first pile body. The first pile body also comprises spiral stirrups fixed to the prestressed steel bars and spirally arranged from the first end to the second end, wherein the spiral stirrups comprise dense spiral stirrups with a pitch of d1 cm in the first pile segment and non-dense spiral stirrups with a pitch of d2 cm in the second pile segment, where d1<d2; 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. In a preferred embodiment, the length of the annular thickened protrusion is defined as L cm, where 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 circumference of the first pile body is defined as h centimeters, and h is L / 7±0.5.

[0007] In a preferred embodiment, the dimension of the annular thickened protrusion along the length direction is defined as L centimeters, 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2, and 0.5<d1 / d2<0.75.

[0008] 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, wherein the end sealing plate seals the opening at the first end of the hollow tubular structure. In a further preferred embodiment, the end sealing plate has a through hole that communicates with the internal cavity of the hollow tubular structure.

[0009] In a preferred embodiment, at least one of the annular thickened protrusions on the first pile segment has a through portion extending through the length. In a further preferred embodiment, the through portions are two or more symmetrically disposed on two sides of the annular thickened protrusion perpendicular to the length, and the through portions are through grooves or through holes.

[0010] In a preferred embodiment, the first pile body includes a third pile segment having dense spiral stirrups therein, the third pile segment extending from the second end to the second pile segment, and the third pile segment is symmetrically arranged with the first pile segment.

[0011] In a second aspect, the utility model discloses a composite foundation pile using any 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.

[0012] In a preferred embodiment, the bottom of the composite foundation pile has a pile end expansion portion, and the geometric center of the pile end expansion portion has the first pile section of the prefabricated pile. 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.

[0013] In a preferred embodiment, the composite foundation pile has an enlarged pile end at its base, with a first precast pile segment located at its geometric center. The height of the enlarged pile end is greater than or equal to 210 cm and less than or equal to 360 cm, and the first segment has at least four annular thickened protrusions within the enlarged pile end. In a further preferred embodiment, the height of the enlarged pile end is greater than or equal to 240 cm and less than or equal to 320 cm, and the first segment has at least five annular thickened protrusions within the enlarged pile end.

[0014] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a bearing capacity analysis diagram for the implantation method in the prior art;

[0016] Figure 2 This is a schematic structural diagram of Example 1 of the prefabricated pile of this application;

[0017] Figure 3 A schematic diagram of the size identification and an enlarged view of the annular thickened protrusion structure of Example 1 of the prefabricated pile of this application;

[0018] Figure 4 This is a schematic diagram of the cage reinforcement structure of the prefabricated pile embodiment 1 of the present application;

[0019] Figure 5 A schematic diagram of the three-dimensional structure and the through-portion structure of another prefabricated pile embodiment of the present application;

[0020] Figure 6 This is a schematic diagram of the three-dimensional structure and end sealing plate structure of another prefabricated pile embodiment of the present application;

[0021] Figure 7 A schematic diagram of the structure of another precast pile embodiment of the present application and a schematic diagram of the stirrup structure;

[0022] Figure 8 This is a schematic structural diagram of another embodiment of the prefabricated pile of the present application;

[0023] Figure 9 This is a schematic structural diagram of another embodiment of the prefabricated pile of the present application;

[0024] Figure 10 This is a schematic diagram of the construction method embodiment 1 of the present application and the composite foundation pile structure formed;

[0025] Figure 11 This is a schematic diagram of the construction method embodiment 2 of the present application and the composite foundation pile structure formed;

[0026] 1. Precast pile; 2. End plate; 21. End cap; 3. Rebar cage; 31. Prestressed steel bars; 32. Spiral stirrups; 10. First pile shaft; 10", first end; 10', second end; 11. Annular thickening protrusion; 110. Through-hole; 101. First pile section; 102. Second pile section; 103. Third pile section; 1000', drilled hole; 1000, composite foundation pile; 6', concrete slurry; 5. Untouched soil; 6. Concrete around pile; 7. Core pile; 1002. Pile end expansion; DETAILED DESCRIPTION

[0027] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0028] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0029] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "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," and "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.

[0030] The following is combined with Figures 2 to 11 The present application is further described in detail with reference to specific embodiments.

[0031] Prefabricated pile embodiment 1

[0032] See also Figures 2 to 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 first pile body 10 has two ends extending in a straight line along the length direction, namely a first end 10" and a second end 10'; a plurality of annular thickened protrusions 11 fixed to the outer peripheral wall of the first pile body 10 and spaced apart 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 further noted that the first pile segment 101 and the second pile segment 102 may have a common annular thickened protrusion 11 at the intersection, as shown in FIG. Figure 2 As shown, the outer diameter of the annular thickened protrusion (11) is D2 cm, wherein 40≤D2≤80; 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 4As shown, the prestressed steel bars 31 are evenly arranged in the cross section of the first pile body 10. 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'. The spiral stirrups 32 have dense spiral stirrups with a pitch of d1 cm in the first pile segment 101 and non-densified spiral stirrups with a pitch of d2 cm in the second pile segment 102, wherein d1 < d2, 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 an exemplary pile body structure size of Example 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 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 length of the annular thickened protrusions 11 is L = 17.5 cm, the height of the annular thickened protrusions 11 from the outer circumference 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 outer diameter of the first pile body 10 is 55 cm. Figure 2-4 The precast pile 1 shown may be formed by a common prestressed precast pile, and may further include end plates 2 located at a first end 10 ″ and a second end 10 ′ of the first pile body 10 .

[0033] 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 toward the first end 10", compared with conventional bamboo piles, it is easier to disperse the pressure that the end face of the first end 10" needs to bear in the soil, thereby improving the bearing limit of the pile end of the bamboo pile. In the specific setting, the spacing between the annular thickened protrusions 11 on the non-reinforced second pile segment is L2 = [80, 90], which is more suitable for matching with the underground soil layer structure. On this basis, the spacing between the annular thickened protrusions 11 on the first pile segment 101 is L1 cm, satisfying L2-L1 = [30, 70]. The spiral stirrups in the precast pile 1 have a reinforced spiral stirrup with a pitch of d1 cm in the first pile segment 101. The length of the reinforced spiral stirrup 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 the reinforced annular thickened protrusion 11 at the pile end, the part is further laterally reinforced by the reinforced stirrups to facilitate the transmission of force to various parts 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.

[0034] 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.

[0035] Based on the prefabricated pile embodiment 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 As shown in the partial enlarged view in FIG. 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 Example 1, this can prevent the lateral friction force on the outer periphery of the pile body from being too concentrated on the annular thickened protrusion 11, causing cracks or detachment between the annular thickened protrusion 11 and the first pile body 10.

[0036] 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 centimeters, 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2, and 0.5<d1 / d2<0.75. It should be noted that in the above setting, if each pile segment has multiple different values of L1, L2, L, d1, and d2, the average value is used for calculation. Based on the above setting, 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 bundle density gradient of the stirrup setting. Compared with embodiment 1, it is more convenient to more evenly transmit the end bearing pressure through the outer peripheral bearing surface of the first pile segment 101.

[0037] 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 As mentioned above, 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 5 The 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, there is no need to excessively fill the interior of the hollow bamboo tube pile with concrete slurry or mixed concrete slurry, which can further save the cost of concrete materials compared to Example 1; and since the concrete slurry or mixed concrete slurry 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.

[0038] Based on the prefabricated pile example 1, in a more preferred embodiment, as Figure 5 Said 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, said through portions 110 are two or more symmetrically arranged on both sides of said annular thickened protrusion perpendicular to the length direction. Figure 5The through groove shown can also be a through hole. Compared with Example 1, the provision of the above-mentioned through portion is further conducive to controlling the drill diameter of the drill hole, 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 placement of the precast pile 1, avoiding the pile body from being unable to sink to the bottom due to the sealing effect of the annular thickened protrusion 11 on the slurry in the drill hole; and the symmetrically arranged through portions can make the slurry overflow at the same speed, 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-holes are arranged on four annular thickened protrusions 11, and Figure 5 In the embodiment shown in FIG, the through-holes are provided on seven annular thickened protrusions 11 .

[0039] 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 7 As 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 costs 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 face. The end bearing force in this solution 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 beneficial to the overall bearing capacity of the pile foundation.

[0040] Other Improved Prefabricated Pile Embodiments

[0041] like Figure 8 、 9 Shown are other improved embodiments of the present invention based on the prefabricated pile embodiment 1.

[0042] 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.

[0043] In addition, the overall length of the precast pile 1 can be set, and the structure 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 with each other about the vertical center plane perpendicular to the length direction of the first pile body 10. This symmetrical structure can decompose the stress at the upper and lower ends of the pile body, where stress concentration occurs, through the soil or concrete surrounding the pile, so that it is not concentrated on the end bearing surface of the pile end.

[0044] In addition, the annular thickened protrusions 11 of the first pile segment 101 and the third pile end 103 may be arranged densely or in an asymmetric structure.

[0045] In addition, the spacing between adjacent annular thickened protrusions 11 on the first pile segment 101 and the third pile end 103 may also be set to be gradual, so that the spacing increases as the side approaches the second pile end 102, thereby gradually decomposing the bearing pressure from the middle of the pile to the pile end, thereby avoiding excessive concentration of the bearing pressure around the pile on the pile surface in a certain length area.

[0046] On the other hand, the present invention provides a construction method based on the above-mentioned prefabricated pile 1.

[0047] Construction method embodiment 1

[0048] As attached Figure 10 (a), 10(b), 10(c), as shown in the figure, the construction method embodiment 1 discloses a construction method using the prefabricated pile embodiment 1 and other preferred embodiments and improved embodiments based on the prefabricated pile embodiment 1, and the construction method comprises the following steps:

[0049] Vertical drilling: as attached Figure 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 construction requirements, and the borehole wall is the original soil 5 around the hole wall.

[0050] Grouting: injecting the concrete slurry 6' to be cured into the borehole; the concrete slurry 6' to be cured may be injected, for example, using the current static drilling root pile construction method, and stirring is performed while injecting the slurry.

[0051] Piling: placing the prefabricated pile 1 into the drilled hole with the first pile section 101 facing downwards.

[0052] According to the prefabricated pile implementation 1, as an exemplary pile body structure size of the prefabricated pile 1, for example, the pitch of the dense spiral stirrups d1 = 4.5 cm, the pitch of the non-densified spiral stirrups 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 protrusion (11) is D2 = 60 cm, and the diameter of the first pile body 10 is D2-2*h = 55 cm.

[0053] During the piling process, before placing the precast pile 1 into the drilled hole, a splice must be made at the top of the precast pile 1, depending on the depth of the drilled hole. This splice can be made with another precast pile 1 or another type of precast pile. Pile placement can then proceed. For example, the splice and placement can be performed using existing static drill root pile installation techniques. The splice can be made by welding the end plates of the precast pile 1 or by using a plug-in or latch-type structure.

[0054] 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 can be 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.

[0055] 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 described in detail here.

[0056] Construction method embodiment 2

[0057] As attached Figure 11 As shown in (a), 11(b), 11(c), and 11(d), compared with construction method embodiment 1, other technical contents 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 solidified forms a pile end expansion portion 1002 in the bottom expansion drill hole, wherein the size of the bottom expansion drill hole is D3'=105 cm, that is, D3' / D1'=1.5.

[0058] This embodiment further enhances the bearing capacity of the base. By enlarging the bottom borehole, the first pile segment 101 can be tightly coupled to the pile end enlargement 1002 through the denser annular thickened protrusion 11, thereby fully and evenly utilizing the bearing capacity of the denser annular thickened protrusion 11 of the first pile segment 101 at the pile end. This also avoids stress concentration and increases settlement resistance through the pile end enlargement 1002, thereby preventing settlement of the composite foundation pile 1000 in certain areas of the foundation. When D3' / D1' is too large, drilling equipment and construction costs are excessive, while the increased bearing capacity is redundant. When D3' / D1' is too small, the end bearing capacity is not fully utilized. Therefore, in other embodiments, a ratio of 1.45 ≤ D3' / D1' ≤ 1.55 is preferred. This ensures increased bearing capacity while saving costs when the first pile segment 101 has the denser annular thickened protrusion 11.

[0059] Construction method embodiment 3

[0060] As attached Figure 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.

[0061] This embodiment achieves a certain degree of optimization over the effect of Example 2 by setting the bottom-enlarged drilling height to encompass four annular thickened protrusions 11. Compared to solutions in which only two or three annular thickened protrusions 11 are coupled to the pile end enlargement 1002, the arrangement of four annular thickened protrusions 11 more easily ensures the coupling force between the first pile segment 101 and the pile end enlargement 1002.

[0062] Construction method embodiment 4

[0063] As attached Figure 11 As shown in Figure (e), Construction Method Example 4 is similar to Construction Method Example 3 in other technical aspects, with the primary difference being that the bottom-enlarged hole height during the drilling step is set to 2.9 meters, encompassing the five annular thickened protrusions 11. This embodiment further strengthens the bonding between the first pile segment 101 and the pile end enlargement 1002.

[0064] Construction method embodiment 5

[0065] Construction Method Example 5 is similar to Construction Method Example 1 in all other technical aspects, differing primarily in that the borehole is further configured with a constant diameter, wherein the borehole diameter is D1' = 75 cm. This embodiment eliminates the pile end enlargement portion 1002 and is suitable for geological environments where bottom enlargement is not feasible. By increasing the drill diameter to a constant diameter, the bond between the precast pile 1 and the surrounding concrete is strengthened. Furthermore, the increased diameter of the surrounding concrete also increases the bearing capacity of the surrounding undisturbed soil 5.

[0066] Another aspect of the present invention provides a composite foundation pile based on the aforementioned prefabricated pile 1 .

[0067] Composite foundation pile embodiment 1

[0068] According to the above construction method embodiment 1, Figure 10 As shown in Figures 10(a), 10(b), and 10(c), based on the precast pile 1, a composite foundation pile 1000 is formed by drilling, grouting, and planting a pile, and finally solidifies, with the precast pile 1 as the core pile 7. The composite foundation pile 1000 is vertically arranged, and has an approximate outer diameter of D1 cm. It is composed of two precast piles 1 combined along the length direction. 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 = the borehole diameter D1' = 75 cm. Due to the error inherent in the foundation drilling construction, the outer peripheral surface of the pile-surrounding concrete 6 forms a roughly cylindrical pile shape. Its outer diameter has a certain construction error, and its molding also causes an error due to the unevenness of the interface S2 of the pile-surrounding concrete 6 and the original soil 5 around the hole wall, resulting in a roughly cylindrical structure. The two precast piles 1 within the composite foundation pile 1000 are based on the precast pile embodiment 1. For example, the pitch of the dense spiral stirrups d1 = 4.5 cm, the pitch of the non-densified spiral stirrups d2 = 8.5 cm, the spacing L2 between the annular thickened protrusions 11 on the second pile segment 102 = 82.5 cm, the spacing L1 between the annular thickened protrusions 11 on the first pile segment 101 = 32.5 cm, the length L of the annular thickened protrusions 11 = 17.5 cm, the height h of the annular thickened protrusions 11 from the outer circumference of the first pile body 10 = 2.5 cm, the outer diameter D2 of the annular thickened protrusions 11 = 60 cm, and the diameter of the first pile body 10 = D2-2*h = 55 cm. The foundation treatment pile based on the composite foundation pile 1000 has all the advantages of the precast pile embodiment 1, which will not be repeated here.

[0069] Composite foundation pile embodiment 2

[0070] As attached Figure 11As shown in (d), composite foundation pile embodiment 2 is obtained based on construction method embodiment 2. Compared with composite foundation pile embodiment 1, composite foundation pile embodiment 2 has the same other technical contents. The main difference is that in the construction plan for forming the composite foundation pile, bottom expansion drilling is further performed in the drilling step of the drilling bottom, and the concrete slurry to be solidified forms a pile end expansion portion 1002 in the bottom expansion drilled hole, wherein the outer diameter D3 of the pile end expansion portion 1002 is roughly the same as the size of the bottom expansion drilled hole, that is, D3=D3'=105 cm. The approximate outer diameter of the composite foundation pile 1000 is D1=75 cm, that is, D3 / D1=1.5.

[0071] This composite foundation pile embodiment 2 further enhances the bearing capacity of the base. By enlarging the bottom borehole, the first pile segment 101 can be tightly coupled to the pile end enlargement 1002 through the denser annular thickened protrusion 11, thereby fully and evenly utilizing the bearing capacity of the denser annular thickened protrusion 11 of the first pile segment 101. This also avoids stress concentration and increases settlement resistance through the pile end enlargement 1002, thereby preventing settlement of the composite foundation pile 1000 in certain areas of the foundation. When D3 / D1 is too large, drilling equipment and construction costs are excessive, while the increased bearing capacity is redundant. When D3 / D1 is too small, the end bearing capacity of the pile end enlargement 1002 is not fully utilized. Therefore, in other embodiments, a ratio of 1.45≤D3 / D1≤1.55 is preferred. This ensures increased bearing capacity while saving costs when the first pile segment 101 has the denser annular thickened protrusion 11.

[0072] Composite foundation pile embodiment 3

[0073] As attached Figure 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.

[0074] In Example 3 of the composite foundation pile, 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 can more easily ensure the bonding force between the first pile segment 101 and the pile end expansion part 1002.

[0075] Composite foundation pile embodiment 4

[0076] As attached Figure 11As shown in Figure (e), Example 4 of the composite foundation pile is identical to Example 3 in other technical aspects, with the primary difference being that the bottom-enlarged hole height during the drilling step is set to 2.9 meters, encompassing the five annular thickened protrusions 11. This example further strengthens the bond between the first pile segment 101 and the expanded portion 1002 at the pile end.

[0077] Composite foundation pile embodiment 5

[0078] Compared to Composite Foundation Pile Example 1, Composite Foundation Pile Example 5 shares other technical details, differing primarily in that the borehole is further configured with a constant diameter, where the borehole diameter is D1' = 75 cm, resulting in an outer diameter of the composite foundation pile of approximately D1 = 75 cm. This embodiment eliminates the pile end expansion portion 1002, making it suitable for geological environments where bottom expansion drilling is difficult. By increasing the borehole diameter, the bond between the precast pile 1 and the surrounding concrete 6 is strengthened. Furthermore, the increased diameter of the surrounding concrete 6 also enhances the bearing capacity of the surrounding undisturbed soil 5.

[0079] 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 and corresponding composite foundation piles of other improved embodiments. Those skilled in the art can be aware of the above-mentioned schemes and can form other undescribed precast pile schemes based on all the contents disclosed in the above-mentioned precast pile 1 embodiment and their combinations for implementing construction and composite foundation piles, which will not be repeated here.

[0080] 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 accompanying 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.

[0081] 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" 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 can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0082] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection 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 linearly 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 spaced apart along the length direction of the first pile body (10), with the outer diameter of the annular thickened protrusions (11) being D2 cm, wherein 40≤D2≤80; 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); 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 along the length direction, and the prestressed steel bars are evenly arranged in the cross section of the first pile body (10). 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-densified spiral stirrups with a pitch of d2 cm in the second pile segment (102), wherein d1 < d2; 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).

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, 0.5*d1 / d2<(L1+L) / (L2+L)<1.1*d1 / d2, and 0.5<d1 / d2<0.

75.

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

7. The precast 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 precast pile (1) according to claim 8, characterized in that The through-portions are two or more symmetrically arranged on both 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) includes a third pile segment (103) having dense spiral stirrups. 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).

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 periphery 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 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 is provided with a pile end expansion portion, and the geometric center of the pile end expansion portion is provided with a first pile section (101) of a prefabricated pile (1). The outer diameter of the pile end expansion portion is approximately D3 centimeters, and D1, D2 and D3 satisfy the following conditions: 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 is provided with a first pile segment (101) of a prefabricated pile (1), the height of the pile end expansion portion is greater than or equal to 210 centimeters and less than or equal to 360 centimeters, wherein the first pile segment (101) has at least four 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 at least 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.

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