Anti-bending and anti-pulling enhanced grouting prefabricated pipe pile and construction method thereof

Abstract

The invention discloses an anti-bending and anti-pulling enhanced grouting prefabricated pipe pile and a construction method thereof, and belongs to the technical field of pile foundation engineering. The pipe pile comprises a pipe pile body and an embedded grouting system. The embedded grouting system comprises an axial grouting pipe, four annular grouting pipes and a one-way valve; the annular grouting pipes are evenly distributed in the preset reinforcing position in the circumferential direction, one ends of the annular grouting pipes communicate with the axial grouting pipes, and the other ends of the annular grouting pipes penetrate through the side wall of the pipe pile. The one-way valve is arranged on the inner side of the outer port of the annular grouting pipe. During construction, pipe piles are prefabricated, and soil around the piles is reinforced through high-pressure grouting of a grouting system after pile sinking. Targeted reinforcement is achieved through the pre-embedded grouting system, the flexural rigidity and the uplift bearing capacity are greatly improved, construction is easy and convenient, and the cost is controllable.

Description

Technical Field

[0001] This invention belongs to the field of pile foundation engineering technology, specifically relating to a grouted precast pipe pile with enhanced bending and tensile strength and its construction method. Background Technology

[0002] Precast pipe piles are widely used in foundation engineering for various projects such as buildings, bridges, and municipal works due to their advantages of fast construction speed, controllable quality, high bearing capacity, and low project cost. However, in practical engineering applications, precast pipe piles often encounter the following problems: First, under the action of horizontal loads on the pile top, the pile top is prone to large horizontal displacement, and a large pile bending moment usually appears in the soil within a depth of about 5 to 10 times the pile diameter above the pile body. In this area, relying solely on the strength of the concrete itself to resist the bending moment, cracks or even pile body damage are likely to occur, threatening the stability and safety of the foundation structure; Second, for precast pipe piles subjected to uplift forces, their pull-out resistance mainly depends on the side friction resistance between the pile body and the surrounding soil. Conventional precast pipe piles have smooth surfaces and limited side friction resistance, making it difficult to meet the high pull-out resistance requirements.

[0003] Existing technologies for improving the bending and tensile strength of precast pipe piles, such as increasing pile diameter and length, suffer from drawbacks including high construction difficulty, significantly increased costs, and demanding requirements for construction equipment. Current grouting pipe pile technology, primarily based on enlarged-base grouting pipe piles, aims to enhance the vertical bearing capacity of the pile foundation. Its design focuses on increasing the vertical bearing capacity at the pile tip, with grouting concentrated at the tip to form an enlarged head. However, this technology cannot precisely target and reinforce localized areas of the pile with large horizontal bending moments. Continuous grouting to reinforce the entire pile would lead to a surge in cement consumption, significantly increasing construction costs, and the reinforcement effect lacks specificity, potentially resulting in material waste and uneven reinforcement. Therefore, there is an urgent need to develop a simple, cost-effective, stable, reliable, and targeted technical solution to simultaneously address the core issues of insufficient bending stiffness and poor tensile strength in precast pipe piles, thereby expanding its application in complex stress scenarios. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a simple, cost-controllable, and reliable reinforcement method for grouted precast pipe piles with enhanced bending and pulling resistance. Through the integrated design of "pre-set grouting structure + precise grouting reinforcement", the invention achieves targeted reinforcement of the bending moment concentration area in the upper part of the pile body, and simultaneously improves the bending stiffness and pulling capacity of the pipe pile.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A type of grouted precast pipe pile with enhanced bending and pulling resistance includes a pipe pile body and a pre-embedded grouting system, which are integrally formed during the prefabrication stage to ensure structural integrity and targeted reinforcement. The pre-embedded grouting system includes: At least one axial grouting pipe is provided along the axial direction of the pipe pile body; Four circumferential grouting pipes are evenly distributed around the pre-defined reinforcement position of the pipe pile body. One end of each circumferential grouting pipe is connected to the axial grouting pipe, and the other end penetrates the side wall of the pipe pile body and extends to its outer surface; and A one-way valve is installed inside the outer port of each of the circumferential grouting pipes to automatically close after grouting is completed.

[0006] Furthermore, the four circumferential grouting pipes are located on the same cross-section of the pipe pile body, and the included angle between two adjacent circumferential grouting pipes is 90 degrees, ensuring uniform diffusion of the grout.

[0007] Furthermore, the pre-embedded grouting system also includes a fixing frame, which is disposed on the top of the pipe pile body and fixedly connected to the reinforcing cage of the pipe pile body, for positioning and fixing the axial grouting pipe.

[0008] The present invention also provides a construction method for the above-mentioned flexural and tensile reinforced grouted precast pipe piles, comprising the following steps: Step S1, Prefabrication: Assemble a pre-embedded grouting system on the steel cage of the prefabricated pipe pile body. The pre-embedded grouting system includes an axial grouting pipe, four circumferential grouting pipes and a one-way valve corresponding to the circumferential grouting pipes. Then pour concrete to integrate the pre-embedded grouting system with the pipe pile body to form a grouting prefabricated pipe pile. Step S2, pile driving construction: Drive the grouting precast pipe piles to the design elevation; Step S3, high-pressure grouting construction: Grout is injected into the soil around the pile under high pressure through the axial grouting pipe and the circumferential grouting pipe to reinforce the soil around the pile at the preset reinforcement position of the pile body.

[0009] Furthermore, in step S1, before pouring concrete, the outer port of the circumferential grouting pipe is temporarily sealed to prevent concrete slurry from entering.

[0010] Furthermore, in step S3, the grouting pressure is set to 2.5–3.5 MPa, and the grouting flow rate is controlled at 30–50 L / min.

[0011] Furthermore, in step S3, a segmented grouting and repeated re-injection process is adopted for grouting control.

[0012] Furthermore, after step S3, step S4 is also included: curing and molding: after grouting is completed, the inside of the axial grouting pipe is filled and its port is sealed, and the grout is cured until the solidified grout reaches the design strength.

[0013] Furthermore, in step S3, ultrafine cement slurry or cement-water glass dual-liquid slurry is selected as the grouting slurry according to the engineering geological conditions.

[0014] The present invention has the following beneficial effects: (1) Grouting precast pipe piles come with a pre-set grouting structure and the supporting construction methods are highly targeted, realizing the seamless connection of the "precast-pile driving-targeted reinforcement" process, which greatly improves the bending stiffness and pull-out bearing capacity compared with conventional precast pipe piles.

[0015] (2) By using grouting pipes arranged in a uniform circumferential pattern and optimized grouting parameters, grout can form a uniform and continuous cement-soil reinforced body in a specific area on the upper part of the pile, resulting in a stable and reliable reinforcement effect with low dispersion. The pre-positioned one-way valve can effectively prevent grout backflow and ensure the integrity of the reinforced body.

[0016] (3) The grouting structure assembly is completed simultaneously during the prefabrication stage of the pipe pile, which does not significantly increase the prefabrication cost. On-site construction only requires conventional pile driving equipment and high-pressure grouting equipment. The process is simple and the construction efficiency is high. The grouting volume is reduced by 40% to 60% compared with the whole pile grouting. The grout utilization rate is high and the overall cost is significantly reduced, which has good economic benefits and promotion value.

[0017] (4) The appropriate grout type can be selected according to different geological conditions (soft soil, silty clay, sand, etc.), and the grouting section position and diffusion radius can be adjusted according to the structural stress requirements. It is suitable for various engineering scenarios that need to withstand horizontal loads and uplift forces, such as building anti-buoyancy, slope support, photovoltaic side anchor pile foundation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the grouting precast pipe pile provided by the present invention.

[0019] Figure 2 This is a detailed drawing showing the fixing of the circumferential grouting pipe and the reinforcing cage provided by the present invention.

[0020] Figure 3 This is a schematic diagram of the installation of the one-way valve and the circumferential grouting pipe provided by the present invention.

[0021] Figure 4 This is a schematic diagram of the tee connector provided by the present invention connecting the circumferential grouting pipe and the axial grouting pipe.

[0022] Figure 5This is a top view schematic diagram of the grouting precast pipe pile provided by the present invention.

[0023] Figure 6 A schematic diagram of the welding of the fixing frame and the reinforcing cage provided by the present invention.

[0024] Figure 7 This is a schematic diagram of the grouting reinforcement of the precast pipe pile provided by the present invention.

[0025] In the diagram: 1. Pipe pile body; 2. Circumferential grouting pipe; 3. Axial grouting pipe; 4. Fixing frame; 5. Grout outlet hole; 6. Short steel bar; 7. Longitudinal reinforcement; 8. Thin iron wire; 9. Stirrup; 10. Electrical tape; 11. One-way valve; 12. T-joint; 13. Reinforcing cage; 14. Steel ring; 15. Grouting reinforcement body. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto.

[0028] Example 1 Please see Figure 1 As shown, the present invention provides a flexural and tensile enhanced grouting precast pipe pile, including a pipe pile body 1 and a pre-embedded grouting system, which are integrally formed during the prefabrication stage to ensure structural integrity and targeted reinforcement.

[0029] The pipe pile body 1 adopts a prestressed high-strength concrete hollow cylindrical structure. Its outer diameter, wall thickness, length, and concrete strength grade are determined according to the engineering design requirements. The steel cage 13 of the pipe pile body 1 is designed with conventional reinforcement according to the current standard pipe pile drawings. The fixing points of the circumferential grouting pipe 2 are reserved only at the preset reinforcement positions (corresponding to the areas with large bending moments in the pile body after pile driving). At the same time, the fixing frame installation position is reserved at the end of the steel cage 13 at the pile top. This design ensures that the installation of the pre-embedded grouting system does not affect the overall stress performance of the steel cage 13, thereby ensuring that the mechanical properties of the pipe pile body 1 are not reduced at the factory.

[0030] The pre-embedded grouting system, which is the key to grouting reinforcement, includes an axial grouting pipe 3, four circumferential grouting pipes 2, a one-way valve 11, a three-way connector 12, and a fixing frame 4.

[0031] The axial grouting pipe 3 is a steel pipe with a wall thickness of not less than 3.5 mm, and is installed along the axial direction of the pipe pile body 1. This thickness design ensures that it will not deform or burst under high-pressure grouting pressure of 2.5 to 3.5 MPa, thus guaranteeing the reliability of the grouting channel and the safety of construction.

[0032] The circumferential grouting pipe 2 is made of high-strength galvanized steel pipe, and its length is 30-50 mm longer than the wall thickness of the pipe pile to ensure penetration of the pipe wall. Four circumferential grouting pipes 2 are evenly distributed circumferentially at the preset reinforcement positions of the pipe pile body 1, and are located on the same cross-section, with adjacent pipes forming an angle of 90° (see...). Figure 2 , Figure 5 The preset reinforcement location is the moment concentration area on the upper part of the pile, corresponding to the soil reinforcement zone within a depth range of 5 to 10 times the pile diameter from the pile top after pile driving. This uniform distribution design allows the grout to form a symmetrical and uniform diffusion field around the pile during grouting, avoiding reinforcement blind spots and ensuring the balance and stability of the reinforcement effect.

[0033] One end of each circumferential grouting pipe 2 is connected to the axial grouting pipe 3 via a tee joint 12 (see...). Figure 4 The connection is sealed with raw material tape to ensure no leakage during high-pressure grouting; the other end penetrates the side wall of the pipe pile body 1 and extends to its outer surface. This end is the outer port (facing the soil side) and is provided with a grout outlet 5 (facing the soil side) for high-pressure grout to flow out and diffuse to the soil around the pile; the inner port (facing the pile core side) is reserved with a threaded interface for connection with the tee connector 12.

[0034] Two parallel short steel bars 6 (using the same type of steel bar as the longitudinal reinforcement 7, approximately 30cm long) are symmetrically welded to both sides of the circumferential grouting pipe 2. The short steel bars 6 are then tied and fixed to the longitudinal reinforcement 7 using thin iron wires 8 (see...). Figure 2 This fixing method ensures that the circumferential grouting pipe 2 does not shift or deflect during concrete pouring, vibration, and centrifugal molding, thus guaranteeing the accuracy of the preset position.

[0035] After the circumferential grouting pipe 2 is fixed, its outer end is temporarily sealed by wrapping it with 3-4 layers of electrical tape 10. For example, using electrical tape for sealing can prevent concrete grout from seeping into the pipe cavity and causing blockage during the precast stage. This temporary sealing measure is simple and effective, ensuring the unobstructed flow of the grouting channel before pile driving.

[0036] The one-way valve 11 is located inside the outer port of each circumferential grouting pipe 2 (see...). Figure 3The grouting pipe 2 is threadedly connected to the circumferential grouting pipe 3, and the sealing gasket is made of wear-resistant and corrosion-resistant nitrile rubber. The opening pressure of the one-way valve 11 is set to 0.2-0.4 MPa, which is suitable for conventional grouting pressure requirements. During grouting, the grout pressure overcomes the opening pressure to open the valve; after grouting stops, the valve automatically closes under the action of the spring. This front-mounted one-way valve design can effectively block the backflow of pore water and uncured grout into the pipe cavity, prevent voids or defects in the grouted body due to grout loss, and ensure the integrity of the grouted body and the reliability of the reinforcement effect.

[0037] The fixing frame 4 is welded from a steel ring 14 and short steel bars 6 (see...). Figure 6 The inner diameter of the steel ring 14 is 2-3 mm larger than the outer diameter of the axial grouting pipe 3, just enough to wrap and fix the axial grouting pipe 3. Four short steel bars 6 are evenly welded around the outer circumference of the ring. The fixing frame 4 is welded to the end of the reinforcing cage 13 on the pile top side, and fixed with the stirrups 9. The axial grouting pipe 3 and the steel ring 14 are spot welded. The fixing frame 4 effectively restricts the radial and axial displacement of the axial grouting pipe 3 during the prefabrication, hoisting and driving of the pipe pile, prevents the grouting system from being damaged by vibration or collision, ensures that the axis of the axial grouting pipe 3 is basically coincident with the axis of the pipe pile body 1, and the axial grouting pipe 3 on the pile top side is not exposed, avoiding the risk of damage during the pile driving process.

[0038] Based on the above-mentioned grouting precast pipe piles, the present invention also provides a supporting construction method, the specific steps of which are as follows: S1, Prefabrication of grouting precast pipe piles: S11. Complete the fabrication of the reinforcing cage 13 according to the structural design. Weld the short reinforcing bars 6 to both sides of the circumferential grouting pipe 2. Then, tie and fix the circumferential grouting pipe 2 to the reinforcing cage 13 with thin iron wire 8 according to the preset position, ensuring that the length of the outer end of the circumferential grouting pipe 2 extending out of the outer circle of the reinforcing cage 13 is equal to the wall thickness of the pipe pile. Connect the four circumferential grouting pipes 2 and the axial grouting pipe 3 with a three-way connector 12, and seal the connection with PTFE tape. Then, install the one-way valve 11 on the inner side of the outer end of the circumferential grouting pipe 2 and tighten it. Weld the fixing bracket 4 to the preset position at the end of the reinforcing cage 13, insert the axial grouting pipe 3 and adjust its position to ensure that the axial grouting pipe 3 is coaxial with the pipe pile body 1 and that the axial grouting pipe 3 on the pile top side does not protrude from the pile top.

[0039] S12, the steel cage 13 with the pre-embedded grouting system assembled is hoisted into the steel formwork of the pipe pile, the steel cage 13 is adjusted to be centered to ensure the thickness of the protective layer, and then concrete is pumped for pouring.

[0040] S13, after pouring, is covered and kept moist for 24 hours at room temperature, then transferred to steam curing. The curing temperature is controlled between 40 and 60℃, and the curing time is not less than 8 hours. Demolding is performed after ensuring the concrete strength reaches more than 70% of the design strength. After demolding, moist curing continues until the design strength is reached. This curing system ensures the early strength and later durability of the pipe pile concrete.

[0041] S2, Pile Driving Construction: Based on the pile dimensions and site geological conditions, conventional static pressure or hammer driving methods are selected for pile driving. During the pile driving process, special attention is paid to protecting the axial grouting pipe 3 interface at the pile top to prevent damage or blockage. After the pile reaches the design elevation, a small amount of clean water is injected into the axial grouting pipe 3 to test the grouting channel's patency, preparing for subsequent high-pressure grouting. This testing step is simple and easy to perform, effectively preventing grouting failure due to channel blockage.

[0042] S3, High-pressure jet grouting construction: S31, Grout Preparation: Select the type of grout based on geological conditions. For sandy soil layers with good permeability, ultrafine cement grout can be selected, with a water-cement ratio controlled between 0.7 and 0.8 to ensure good fluidity and permeability. For cohesive soil or soil layers with developed fissures, a cement-water glass two-component grout can be selected, with the water-cement ratio of the cement grout controlled between 0.5 and 0.6 to ensure appropriate gel time and later strength. Use a high-speed mixer for mixing for at least 3 minutes to ensure uniform grout. After mixing, filter the grout through a filter screen with a pore size no larger than 2 mm before pouring it into the grouting tank to prevent impurities from clogging the grouting channels and one-way valve 11. This grout preparation process ensures the quality of the grouting material and the smoothness of the grouting process.

[0043] S32, parameter settings: The grouting pressure is set to 2.5~3.5MPa. This pressure range ensures that the grout can effectively diffuse into the soil pores while avoiding excessive pressure that could cause the surrounding soil to heave. The grouting flow rate is controlled at 30~50L / min to ensure that the grout is injected at a uniform speed and to avoid local pressure concentration. After each grouting section is completed, the grouting pressure is kept constant for 5~8min. This pressure stabilization process ensures that the grout fully penetrates into the soil pores, increasing the density and uniformity of the grouting solid.

[0044] S33, Grouting Control: The "segmented grouting and repeated reinjection" process is adopted, that is, a portion of grout is injected first, paused briefly to allow the pressure to drop slightly, and then injection is continued, and this process is repeated. This process can effectively avoid soil splitting or grout loss caused by excessive injection volume at one time, ensuring full grouting without damaging the surrounding environment.

[0045] S4, Curing and Shaping: After grouting, the interior of the axial grouting pipe 3 is filled with cement grout to prevent it from becoming a corrosion channel; then, a special rubber sealing plug is used to seal the port of the axial grouting pipe 3 at the top of the pile. After curing until the grout solidification reaches the design strength, the pipe pile, the solidified grout, and the surrounding soil form an integrated composite solidification (see...). Figure 7 The grouting reinforcement (15) completes the reinforcement. This post-treatment step effectively prevents the grouting pipe from becoming a corrosion channel in the later stage, ensuring the long-term durability of the structure.

[0046] In this embodiment, because the circumferential grouting pipes 2 are uniformly arranged circumferentially, the grout forms a uniform and continuous cement-soil reinforced body at the preset reinforcement position during grouting, effectively improving the bending stiffness and pull-out lateral friction resistance of the area. The anti-backflow design of the one-way valve 11 ensures the integrity of the reinforced body. Compared with full pile grouting, the grouting volume is reduced by 40% to 60%, the grout utilization rate is high, and the overall cost is significantly reduced.

[0047] Example 2 This embodiment is basically the same as Embodiment 1, except that: according to the actual stress requirements of the project, multiple "preset reinforcement positions" can be set at different depths of the pile body. Each position corresponds to a set of four circumferential grouting pipes 2 and their one-way valves 11. Each set of circumferential grouting pipes 2 is connected to the same axial grouting pipe 3 to achieve multi-layer reinforcement. For example, for anti-buoyancy piles subjected to large horizontal loads or uplift forces, two sets of circumferential grouting pipes 2 can be used to reinforce the upper and lower parts of the pile body respectively, further improving the overall bending and uplift resistance. This multi-layer reinforcement design enables the present invention to adapt to more complex stress conditions and expands its application range.

[0048] Example 3 This embodiment is basically the same as Embodiment 1, except that the grout type and grouting parameters can be adjusted adaptively for different geological conditions. For example, in gravel layers with high permeability, ultrafine cement grout can be used and the grouting pressure can be appropriately increased to 3.0–3.5 MPa to expand the grout diffusion radius and form a larger reinforced area. In soft clay layers, cement-water glass dual-liquid grout can be used and the grouting flow rate can be controlled at 30–40 L / min to avoid fracturing damage, while the rapid gelation characteristics of the dual-liquid grout can be used to control the grout diffusion range. This geologically adaptable design ensures the applicability of the invention under different engineering conditions and the reliability of the reinforcement effect.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of grouted precast pipe pile with enhanced bending and tensile strength, characterized in that, include: The pipe pile body is a precast hollow concrete structure. A pre-embedded grouting system is embedded inside the pipe pile body; The pre-embedded grouting system includes: At least one axial grouting pipe is provided along the axial direction of the pipe pile body; Four circumferential grouting pipes are evenly distributed around the pre-defined reinforcement position of the pipe pile body. One end of each circumferential grouting pipe is connected to the axial grouting pipe, and the other end penetrates the side wall of the pipe pile body and extends to its outer surface; and A one-way valve is installed inside the outer port of each of the circumferential grouting pipes to automatically close after grouting is completed.

2. The flexural and tensile reinforced grouted precast pipe pile according to claim 1, characterized in that, The four circumferential grouting pipes are located on the same cross-section of the pipe pile body, and the included angle between two adjacent circumferential grouting pipes is 90 degrees.

3. The flexural and tensile reinforced grouted precast pipe pile according to claim 1 or 2, characterized in that, The pre-embedded grouting system also includes a fixing frame, which is set on the top of the pipe pile body and fixedly connected to the reinforcing cage of the pipe pile body, for positioning and fixing the axial grouting pipe.

4. A construction method for a flexurally and pleurally reinforced precast pipe pile as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step S1, Prefabrication: Assemble a pre-embedded grouting system on the steel cage of the prefabricated pipe pile body. The pre-embedded grouting system includes an axial grouting pipe, four circumferential grouting pipes and a one-way valve corresponding to the circumferential grouting pipes. Then pour concrete to integrate the pre-embedded grouting system with the pipe pile body to form a grouting prefabricated pipe pile. Step S2, pile driving construction: Drive the grouting precast pipe piles to the design elevation; Step S3, high-pressure grouting construction: Grout is injected into the soil around the pile under high pressure through the axial grouting pipe and the circumferential grouting pipe to reinforce the soil around the pile at the preset reinforcement position of the pile body.

5. The construction method according to claim 4, characterized in that, In step S1, before pouring concrete, the outer port of the circumferential grouting pipe is temporarily sealed to prevent concrete slurry from entering.

6. The construction method according to claim 4, characterized in that, In step S3, the grouting pressure is set to 2.5–3.5 MPa, and the grouting flow rate is controlled at 30–50 L / min.

7. The construction method according to claim 4, characterized in that, In step S3, grouting is controlled by a process of segmented grouting and repeated backfilling.

8. The construction method according to claim 4, characterized in that, Step S3 is followed by step S4, which is curing and shaping: after grouting is completed, the inside of the axial grouting pipe is filled and its port is sealed, and the grout is cured until the solidified grout reaches the design strength.

9. The construction method according to claim 4, characterized in that, In step S3, ultrafine cement slurry or cement-water glass dual-liquid slurry is selected as the grouting slurry according to the engineering geological conditions.

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