Variable cross-section prefabricated tubular pile
By opening grouting holes on the side walls of variable-section prefabricated pipe piles and using solid steel pipe piles and reinforced cages in rock formations, the problems of low soil strength and construction difficulties in the existing technology are solved, and construction reliability is improved and efficiency enhances the stability and strength of pile connections.
Patent Information
- Application Number
- CN202421167581.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-27
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2034-05-27
AI Technical Summary
The existing variable-section pipe pile construction methods cause great disturbances to the soil, resulting in low soil strength, easy to cause engineering accidents, and difficult construction in rock strata and unstable connections.
A variable-section prefabricated pipe pile is designed, including opening grouting holes on the side wall of the first prefabricated pile, and combining solid steel pipe piles with concentric steel cages in the rock layer, and constructed by static pressure and hammering methods, using the injection Slurry holes and steel cages reinforce soil and rock formations.
It reduces soil disturbances, improves construction reliability and efficiency, improves the stability and strength of pile connections, and avoids soil cracks and construction difficulties.
Smart Images
Figure CN222252077U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the field of geotechnical mechanics, and particularly relates to a precast pipe pile with variable cross-section. Background Art
[0002] At present, with the rapid development of urban construction, the application of pile foundation support is becoming increasingly widespread. Precast piles are increasingly widely used due to their convenient construction and high strength. In foundation pit engineering, the strata are mostly soil on the upper layer and rock on the lower layer. Therefore, at present, the method of variable cross-section pipe piles is often adopted. The lateral stress of the upper soil layer is relatively large, and pipe piles with a larger diameter are used, while the lateral stress of the lower rock layer is relatively small, and pipe piles with a smaller diameter are used. The construction of existing pipe piles is by the static pressure method or the hammering method. These two construction methods will cause great disturbance to the soil body. The internal stress of the soil body increases under the extrusion action, the strength of the soil around the pile is low, cracks are generated in the soil body, and in severe cases, engineering accidents may even be caused. Summary of the Utility Model
[0003] In order to solve the defect of low strength of the soil around the existing variable cross-section pipe pile, the utility model provides a precast pipe pile with variable cross-section, and the scheme is as follows:
[0004] A precast pipe pile with variable cross-section includes a first precast pile and a second precast pile. The second precast pile is located inside the first precast pile. Among them, grouting holes are opened on the side wall of the first precast pile.
[0005] Furthermore, the aperture of the grouting hole gradually expands from the inner wall to the outer wall of the first precast pile. The relationship between the outer wall aperture D and the inner wall aperture d of the grouting hole is D≥2d.
[0006] Furthermore, the grouting holes are longitudinally divided into multiple rows along the side wall, are evenly distributed at the same circular position, and each row has no less than 4. The grouting holes in adjacent rows are staggered.
[0007] Furthermore, the longitudinal spacing l of the grouting holes in adjacent layers <vt, where v is the diffusion rate of the slurry in different soil masses, and t is the initial setting time of the grouting body.
[0008] Furthermore, the first precast pile is set as a hollow pipe pile, and the top of the hollow pipe pile is set as a conical head, and the cone angle of the conical head is 60°.
[0009] Furthermore, the second precast pile includes a solid steel pipe pile and a steel reinforcement cage arranged concentrically. The length of the steel reinforcement cage is less than the length of the steel pipe pile. The steel reinforcement cage is welded outside the steel pipe pile and has a diameter matched with the inner diameter of the first precast pile. The steel reinforcement cage is connected to the inner wall of the first precast pile by a groove connection method.
[0010] Furthermore, a plurality of grooves are evenly opened in the circumferential direction on the inner wall of the first precast pile, and the same number of convex parts are evenly fixed at the corresponding positions on the side wall of the steel reinforcement cage. The grooves and the convex parts are used in cooperation.
[0011] Furthermore, the cross section of the groove is a trapezoid that gradually expands from the inside to the outside.
[0012] Furthermore, the short side of the trapezoid is longer than the diameter of the steel bar of the steel cage, the long side of the trapezoid is twice the diameter of the steel bar, and the height of the trapezoid is equal to the diameter of the steel bar.
[0013] Furthermore, the first prefabricated pile is configured as a PHC pipe pile.
[0014] Compared with the prior art, the advantages of the utility model are:
[0015] 1. The utility model provides grouting holes on the side wall of the first precast pile to reinforce the soil by grouting, which greatly reduces the harm of soil disturbance, improves the problem of low strength of soil around the pile in the previous precast pipe pile support, and improves construction reliability.
[0016] 2. The utility model improves the problem of the difficulty of pipe piles entering the rock during the previous hammering process by constructing steel pipe piles in the rock layer, thereby improving the construction efficiency.
[0017] 3. The utility model connects the steel pipe pile and the first prefabricated pile together through slurry and a steel cage, thereby improving the problems of unstable connection and eccentricity of the upper and lower piles in the previous variable-section pile connection and improving the connection strength. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 The construction steps of the variable cross-section prefabricated pipe piles according to an embodiment of the utility model are as follows;
[0019] Figure 2 This is a schematic diagram of the arrangement of grouting holes for the first precast pile part of an embodiment of the utility model.
[0020] Figure 3 A schematic cross-sectional view of a grouting hole structure according to an embodiment of the utility model;
[0021] Figure 4 This is a schematic structural cross-sectional view of a variable-section prefabricated pipe pile according to an embodiment of the utility model;
[0022] Figure 5 It is a schematic diagram of the structural section of a first prefabricated pile in one embodiment of the utility model;
[0023] Figure 6 A schematic cross-sectional view of the mating position of the protrusion and the groove in one embodiment of the utility model;
[0024] In the above figures: 1. first precast pile; 11. grouting hole; 12. groove; 2. second precast pile; 21. steel pipe pile; 22. steel cage; 221. protrusion; 3. soil layer; 4. rock layer; 5. slurry. DETAILED DESCRIPTION
[0025] For the convenience of those skilled in the art to understand the present utility model, the specific embodiments of the present utility model will be described below with reference to the accompanying drawings.
[0026] As Figures 1 to 6 shown, a precast pipe pile with variable cross-section is applicable to the construction of geological conditions where the upper layer is soil layer 3 and the lower layer is rock layer 4, and includes a first precast pile 1 and a second precast pile 2. The second precast pile 2 is located inside the first precast pile 1 and can partially extend out. The first precast pile 1 is a hollow tapered head pipe pile, and the second precast pile 2 includes a steel cage 22 and a steel pipe pile 21 arranged concentrically. During construction, the first precast pile 1 is pressed into the soil layer 3 by the static pressure method, and then the second precast pile 2 is placed into the first precast pile 1, and the steel pipe pile 21 is pressed into the rock layer 4 by the hammer pressure method.
[0027] For the existing precast pipe pile with variable cross-section, the whole pile adopts the form of a hollow concrete pipe pile. The original intention is that the lower half of the pile body is often in the rock layer 4, and compared with the soil layer 3, the stress is smaller. Therefore, a hollow pipe pile with a smaller cross-section can be used. However, in order to ensure the strength of the pipe pile at the same time, the outer diameter reduction of the hollow concrete pipe pile is limited, resulting in difficulties in the construction of the pipe pile of the existing structure in the rock layer 4. Therefore, the precast pipe pile with variable cross-section of the present utility model uses a solid steel pipe pile 21 with a smaller diameter to replace the hollow concrete pipe pile to achieve the purpose of facilitating rock penetration.
[0028] The first precast pile 1 is constructed for the soil layer 3. The structure of this pipe pile is the same as that of the PHC pipe pile. A conical head is provided at the top of the pipe pile, and the cone angle is 60°. This can facilitate the smooth entry of the first precast pile 1 into the soil and improve the construction efficiency. The inside of the first precast pile 1 is hollow to provide guiding and positioning for the second precast pile 2 constructed along the pipe wall subsequently.
[0029] As Figure 2 、 3 shown, grouting holes 11 are distributed on the side wall of the first precast pile 1. The grouting holes 11 are divided into multiple rows longitudinally along the side wall, and at least 4 are in a group circumferentially. In this embodiment, there are 4 in a group and they are evenly distributed. The grouting holes 11 in adjacent rows are staggered; the longitudinal spacing between the grouting holes 11 in adjacent layers is l, and l < vt, ensuring that the slurry 5 fully diffuses into the soil to be reinforced before solidification.
[0030] l is related to the process of the slurry 5. A pretest is carried out on the grouted body to determine the initial setting time t; a grouting pretest is carried out to determine the diffusion rate v of the slurry 5 in different soil qualities.
[0031] The aperture of the grouting hole 11 gradually expands from the inner wall to the outer wall of the first precast pile 1. The outer wall aperture of the grouting hole 11 is D, and the inner wall aperture is d, where D ≥ 2d. This can ensure that when the first precast pile 1 is statically pressed into the soil, it is difficult for the external soil to enter the pile body; and during grouting, the inner diameter of the grouting hole 11 is smaller.
[0032] The larger the outer diameter, the slurry 5 can enter the soil more smoothly under the pressure difference.
[0033] The second precast pile 2 is constructed for the rock layer 4, and includes a solid steel pipe pile 21 and a concentrically arranged steel cage 22. The length of the steel cage 22 is less than that of the steel pipe pile 21. The steel cage 22 is welded to the outside of the steel pipe pile 21, and its diameter matches the inner diameter of the first precast pile 1. The steel cage 22 is connected to the inner wall of the first precast pile 1 by a groove connection.
[0034] like Figures 4 to 6 As shown, a plurality of grooves 12 are evenly arranged in the inner wall of the first precast pile 1 in a circumferential direction, and the same number of protrusions 221 are evenly fixed at corresponding positions on the side wall of the steel cage 22, and the grooves 12 and the protrusions 221 are used in coordination.
[0035] Specifically, the steel cage 22 is connected to the steel pipe pile 21 by welding. To facilitate construction, the form of the steel cage 22 is consistent with the steel cage 22 of the conventional concrete pile. To prevent the steel pipe pile 21 from being out of center with the concrete pipe pile, the steel cage 22 is welded to the steel pipe pile 21, and a groove 12 is set inside the first prefabricated pile 1 to limit the steel cage 22. A protrusion 221 is set at the corresponding position of the steel cage 22. Figure 5 , 6 As shown, the cross-section of the groove 12 is a trapezoid that gradually expands from the inside to the outside. The length of the short side of the trapezoid is close to the diameter of the steel bar and slightly larger than the diameter of the steel bar. For example, if the diameter of the steel bar is 10mm, the diameter of the short side is 12mm. The long side of the trapezoid is usually twice the diameter of the steel bar, and the height of the trapezoid is 1 times the diameter of the steel bar. The specific construction method of the protrusion 221 is to weld a prefabricated trapezoidal steel plate to the end of the steel bar. This can ensure that the steel cage 22 does not slide inside the pipe pile, thereby ensuring that the pipe pile is concentric with the steel pipe pile 21. The number of grooves 12 can be determined according to the actual construction situation, and stability can be guaranteed when it is greater than three. In this embodiment, four grooves 12 are selected.
[0036] In this embodiment, the first precast pile 1 is a PHC pipe pile, and concrete is poured inside, hereinafter referred to as a concrete pile. During construction, the steel pipe pile 21 passes through the hollow inside of the first precast pile 1, is lowered to the bottom, and is hammered into the rock. The wall thickness of the concrete pile and the diameter of the steel pipe pile 21 can be obtained by calculation. First, the diameter and wall thickness of the concrete pile are determined based on construction experience and stratum properties. Secondly, in order to prevent stress concentration at the variable cross-section of the concrete pile and the steel pipe pile 21 due to excessive bending stiffness, the bending stiffness of the two piles should be kept consistent as much as possible.
[0037] The bending stiffness of the two piles is equal, and the formula is as follows:
[0038] E1I1=E2I2
[0039] The moment of inertia of the concrete pile section is as follows:
[0040]
[0041] The moment of inertia of the steel pipe pile 21 section is as follows:
[0042]
[0043] In the above formula: E1 is the elastic modulus of the concrete pile, which is a fixed value; I1 is the moment of inertia of the concrete pile section; R1 is the outer diameter of the first precast pile 1, d1 is the inner diameter of the concrete pipe pile, and the inner and outer diameters of the concrete pile can be determined by analogy with engineering experience, that is, I1 is determined; E2 is the elastic modulus of the steel pipe pile 21, which is a fixed value; I2 is the moment of inertia of the steel pipe pile 21 section, and R2 is the diameter of the steel pipe pile 21. Among them, E1, E2 and I1 have been determined, so the diameter R2 of the steel pipe pile 21 can be determined by the above formula.
[0044] like Figure 1 As shown, the construction process is as follows:
[0045] Step 1: First, level the site, measure and lay out the lines, and then locate the site.
[0046] Step 2: transport the first precast pile 1 to the construction site and press the pile into the soil layer 3 by static pressure. The exposed length of the first precast pile 1 is measured to determine the buried depth. When the pile is pressed to a predetermined depth, the static pressure construction of the first precast pile 1 is stopped.
[0047] Step 3: construct the second precast pile 2, and lower the second precast pile 2 along the groove 12 inside the first precast pile 1. Figure 4 , 5 A steel cage 22 is disposed on the top of the second precast pile 2, and the protrusion 221 on the steel cage 22 fits with the inner groove 12 of the first precast pile 1, which can fix the position of the second precast pile 2, so that the first precast pile 1 and the second precast pile 2 are concentric.
[0048] Step 4: hammer the second precast pile 21 to the bottom of the first precast pile 1 by a pile driver. Then continue hammering to embed the steel pipe pile 21 into the rock layer 4. When the steel cage 22 contacts the bottom of the first precast pile 1, the construction of the steel pipe pile 21 is completed.
[0049] Step 5: Grouting the pile body. Inject slurry 5 on the top of the first precast pile 1. The slurry 5 combines with the steel cage 22 to strengthen the connection between the two piles. Under continuous grouting, the slurry 5 will penetrate into the soil along the grouting holes 11 on the side wall of the first precast pile 1 to reinforce the soil around the pile.
[0050] The above-described implementation methods of the utility model do not constitute a limitation on the protection scope of the utility model. Any modification, equivalent replacement and improvement made within the spirit and principle of the utility model shall be included in the protection scope of the claims of the utility model.
Claims
1. A variable cross-section prefabricated pipe pile, characterized in that: It includes a first precast pile (1) and a second precast pile (2), and the second precast pile (2) is located inside the first precast pile (1). Among them, a grouting hole (11) is opened on the side wall of the first precast pile (1).
2. The variable cross-section prefabricated pipe pile according to claim 1, characterized in that: The aperture of the grouting hole (11) gradually expands from the inner wall to the outer wall of the first precast pile (1), and the relationship between the outer wall aperture D and the inner wall aperture d of the grouting hole (11) is D≥2d.
3. The variable cross-section prefabricated pipe pile according to claim 1, characterized in that: The grouting holes (11) are arranged in multiple rows longitudinally along the side wall, are evenly distributed at the same circumferential position, and each row has no less than 4, and the grouting holes (11) in adjacent rows are staggered.
4. The variable cross-section prefabricated pipe pile according to claim 3, characterized in that: The longitudinal spacing l between adjacent layers of grouting holes (11) < vt, where v is the diffusion rate of the slurry in different soil masses and t is the initial setting time of the grouting body.
5. The variable cross-section prefabricated pipe pile according to claim 1, characterized in that: The first precast pile (1) is set as a hollow pipe pile, and the top of the hollow pipe pile is set as a conical head, and the cone angle of the conical head is 60°.
6. The variable cross-section prefabricated pipe pile according to claim 1, characterized in that: The second precast pile (2) includes a solid steel pipe pile (21) and a concentrically arranged steel reinforcement cage (22). The length of the steel reinforcement cage (22) is less than the length of the steel pipe pile (21). The steel reinforcement cage (22) is welded to the outside of the steel pipe pile (21) and has a diameter matched with the inner diameter of the first precast pile (1). The steel reinforcement cage (22) is connected to the inner wall of the first precast pile (1) by a groove connection method.
7. The variable cross-section prefabricated pipe pile according to claim 6, characterized in that: A plurality of grooves (12) are evenly opened in the circumferential direction on the inner wall of the first precast pile (1), and the same number of protruding members (221) are evenly fixed at corresponding positions on the side wall of the steel reinforcement cage (22). The grooves (12) and the protruding members (221) are used in cooperation.
8. The variable cross-section prefabricated pipe pile according to claim 7, characterized in that: The cross section of the groove (12) is a trapezoid that gradually expands from the inside to the outside.
9. The variable-section prefabricated pipe pile according to claim 8, characterized in that: The length of the short side of the trapezoid is greater than the diameter of the steel bar of the steel reinforcement cage (22), the length of the long side of the trapezoid is twice the diameter of the steel bar, and the height of the trapezoid is equal to the diameter of the steel bar.
10. The variable cross-section prefabricated pipe pile according to claim 1, characterized in that: The first precast pile (1) is set as a PHC pipe pile.