Steel pipe composite pile and construction method thereof

Abstract

The steel pipe composite pile comprises a sleeve valve steel pipe pile, a core filling body and a cement paste composite reinforcing body, the sleeve valve steel pipe pile comprises a sleeve valve pipe and spiral blades welded to the outer wall of the sleeve valve pipe, grouting holes are formed in the pipe wall of the sleeve valve pipe, and pre-closed grouting valves are installed on the grouting holes; the core filling body is located in an inner cavity of the sleeve valve pipe. The sleeve valve steel pipe pile is wrapped with the cement paste composite reinforcing body, the cement paste composite reinforcing body is formed by compositing cement paste and underground soil, the cement paste composite reinforcing body comprises an expansion part, and a spiral blade is arranged in the expansion part. The invention further discloses a construction method of the steel pipe composite pile. The sleeve valve pipe is adopted as a steel structure, segmented grouting is achieved, grouting reinforcement can be conducted on a soil body according to needs, and the soil body around the pile is modified; the spiral blades improve the bearing capacity of the pile body, the core filling body improves the compressive rigidity and stability of the pile body, and the beneficial effect that drilling, pile body installation and grouting reinforcement are integrated is achieved.

Description

Technical Field

[0001] This invention relates to pile foundation engineering technology in geotechnical engineering, and particularly to a steel pipe composite pile and its construction method. Background Technology

[0002] In urban construction, renovation of existing buildings, and reinforcement of infrastructure, pile foundation construction is often required under conditions of limited space and high environmental protection requirements. Commonly used methods such as micropiles and traditional helical anchor piles have significant limitations: micropiles involve numerous construction procedures, long construction periods, and difficulty in effectively controlling grouting quality; while traditional helical anchor piles integrate drilling and pile installation, their one-time pile bottom grouting cannot provide targeted reinforcement to different soil layers, and the morphology and uniformity of the grout cannot be guaranteed, resulting in limited improvement in bearing capacity. Furthermore, existing methods are inefficient in hard or complex strata, and single pile bearing capacity remains a bottleneck. Summary of the Invention

[0003] To at least partially address the numerous problems existing with current micropiles and helical anchor piles in pile foundation construction under conditions of limited space and high environmental protection requirements, this application proposes a steel pipe composite pile, which includes:

[0004] The sleeve valve steel pipe pile includes a sleeve valve pipe and at least two sets of spiral blades welded to the outer wall of the sleeve valve pipe. The at least two sets of spiral blades are arranged at intervals along the axial direction. Several grouting holes are provided on the pipe wall of the sleeve valve pipe. A pre-closed grouting valve is installed on each grouting hole. The opening pressure of the pre-closed grouting valve is 5-25MPa.

[0005] The core filler is located inside the sleeve valve tube;

[0006] A cement grout composite reinforcement body is wrapped around a sleeve valve steel pipe pile. The cement grout composite reinforcement body is composed of cement grout injected into the outside of the sleeve valve steel pipe pile and underground soil. The cement grout composite reinforcement body includes at least one enlarged section and has a set of helical blades in at least one enlarged section.

[0007] This application uses a sleeve valve tube as the steel structure of the steel pipe composite pile, which enables segmented grouting. Grouting can be performed on the soil outside the sleeve valve tube as needed to reinforce the soil around the pile, thereby modifying the soil around the pile and significantly improving the bearing capacity and quality control of the single pile. The spiral blades welded to the outside of the sleeve valve tube are used to improve the bearing capacity of the pile body. It has the advantage of integrating drilling, pile installation and grouting reinforcement, which can effectively improve construction efficiency. A core filling body is set inside the sleeve valve tube to further improve the compressive stiffness and stability of the pile body.

[0008] Specifically, the core filler is formed by mixing and solidifying cement grout with graded crushed stone, or by solidifying fine aggregate concrete. In actual construction, different materials can be selected to form the core filler according to different requirements or existing conditions. Both methods can solidify the core filler and the sleeve valve pipe into a whole, ensuring the high density and integrity of the core filler. When the core filler is formed by mixing and solidifying cement grout with graded crushed stone, the cement grout can also eliminate the potential for voids within the core filler, effectively improving the bearing capacity of the pile.

[0009] Furthermore, for ease of construction, the pre-sealed grouting valve uses a brittle material plug, which is made of gypsum-based composite material, M5-M15 cement mortar, or controllable degradable polymer. Because a helical blade is installed on the sleeve valve tube, traditional elastic rings can only be used as pre-sealed grouting valves in areas where the helical blades are not present at the ends of the sleeve valve tube. Using a brittle material plug as the pre-sealed grouting valve effectively overcomes this problem. When manufacturing the brittle material plug, it is only necessary to insert the aforementioned materials into the grouting hole. An appropriate thickness of the aforementioned materials can also be applied to the outer wall of the grouting hole area to adjust the opening force of the brittle material plug, offering advantages of simple and quick operation.

[0010] Furthermore, a sealing pile tip is installed at the lower end of the sleeve valve pipe. This sealing pile tip not only seals the lower end of the sleeve valve pipe, but also reduces the resistance of the sleeve valve steel pipe pile when drilling into the underground soil.

[0011] To ensure the successful completion of the above-mentioned construction of steel pipe composite piles, this application also proposes a construction method for steel pipe composite piles, which includes the following steps:

[0012] (1) Rotate and press the sleeve valve steel pipe pile into the underground soil to the design elevation; the sleeve valve steel pipe pile includes a sleeve valve pipe and at least two sets of spiral blades welded on the outer wall of the sleeve valve pipe. The at least two sets of spiral blades are arranged at intervals along the axial direction. Several grouting holes are provided on the pipe wall of the sleeve valve pipe. A pre-closed grouting valve is installed on each grouting hole. The opening pressure of the pre-closed grouting valve is 5-25MPa.

[0013] (2) Insert the grouting core tube into the inner cavity of the sleeve valve tube and perform segmented grouting;

[0014] The lower end of the grouting core tube is the grouting perforated tube, which has several grout outlet holes. Both ends of the grouting perforated tube are equipped with grout stop plugs.

[0015] (3) Pile body filling: Fill the sleeve valve pipe with graded crushed stone, and then inject cement grout into the sleeve valve pipe; or pour fine stone concrete into the sleeve valve pipe.

[0016] This application utilizes high-pressure segmented grouting to induce a triple effect of penetration, compaction, and fracturing in the soil surrounding the pile, forming a series of "pressure plates" that significantly improve the side friction resistance around the pile. During grouting, precise grouting reinforcement can be achieved for different soil layers according to design requirements to cope with various complex geological conditions. The use of welded spiral blades on the outside of the sleeve valve tube enhances the pile's bearing capacity, offering the advantage of integrating drilling, pile installation, and grouting reinforcement. A core filler is placed inside the sleeve valve tube to further improve the pile's compressive stiffness and stability.

[0017] Specifically, in order to achieve splitting and compaction of the soil around the piles, in step (2), the grouting pressure is 5-25 MPa when performing segmented grouting. 5 MPa is the starting pressure that produces a significant improvement effect. If it is lower than 5 MPa, the desired effect may not be achieved. The upper limit of 25 MPa takes into account both equipment capacity and economy, so as to avoid using equipment with higher pressure ratings, improve the economy of construction, and avoid increasing construction costs.

[0018] To further improve the economic efficiency of construction, different grouting pressures are selected for different geological layers. It is preferred to use a grouting pressure of 5-15 MPa for soft soil layers and 15-25 MPa for dense soil layers when performing segmented grouting.

[0019] Specifically, in order to ensure the penetration of cement grout into the soil around the pile, in step (2), when performing segmented grouting, the water-cement ratio of the cement grout used is 0.5-1.0.

[0020] Specifically, in order to ensure that the cement grout can reach the bottom of the sleeve valve tube smoothly, in step (3), when injecting cement grout into the sleeve valve tube, the water-cement ratio of the cement grout is 0.5-1.0, and the grouting pressure is 2-5 MPa. Under the above pressure, it can be ensured that the cement grout fully penetrates and coats all the crushed stone to form a high-density core filler, while avoiding the disturbance that high pressure may cause to the cement grout composite solidified body around the already formed pile.

[0021] In this application, the water-cement ratio is the weight ratio of water to cement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the sleeve valve steel pipe pile.

[0023] Figure 2 for Figure 1 Enlarged view of section A.

[0024] Figure 3 This is a schematic diagram of a steel pipe composite pile.

[0025] Figure 4 for Figure 3 Enlarged view of section B.

[0026] Figure 5 This is a diagram showing the state of grouting during the grouting process via the grouting core tube.

[0027] Figure 6 This is a construction flowchart for steel pipe composite piles. Detailed Implementation

[0028] The structure of the sleeve valve steel pipe pile 100 is described below. Please refer to [link / reference]. Figure 1 and Figure 2 The sleeve valve steel pipe pile 100 includes a sleeve valve pipe 11 and five sets of spiral blades 12 welded to the outer wall of the sleeve valve pipe. The spiral blades 12 are spaced apart axially. The accompanying drawings only show two sets of spiral blades as an example; the number of sets of spiral blades can be adjusted according to the construction conditions, and may include two, three, or six sets, or other numbers. The sleeve valve steel pipe 11 is made of seamless steel pipe with an outer diameter of 114 mm and a wall thickness of 4 mm. A sealing pile tip 15 is provided at the lower end of the sleeve valve pipe, which seals the lower end of the inner cavity of the sleeve valve pipe.

[0029] Several grouting holes 13 are provided on the wall of the sleeve valve pipe. A pre-sealed grouting valve is installed in each grouting hole. The opening pressure of the pre-sealed grouting valve is ≥5MPa. The pre-sealed grouting valve is a brittle material plug, which is made of low-grade M5-M15 cement mortar. Specifically, in this embodiment, the brittle material plug is made of M10 cement mortar, which has the following materials:

[0030] 70 kg of ordinary Portland cement (P.O42.5R), 23 kg of Grade II fly ash, 450 kg of natural sand, 27 g of hydroxypropyl methylcellulose, and 22 g of sodium dodecyl sulfate are mixed with water to prepare a cement mortar with a water retention rate of 92.1%, a consistency of 55 mm, and a 28-day compressive strength of 12.5 MPa. The quantities of the above components can be adjusted proportionally according to specific needs.

[0031] In other embodiments, the cement mortar may be prepared in the following proportions: 53-80 kg of cement, 18-27 kg of fly ash, 370-530 kg of natural sand, 16-160 kg of hydroxypropyl methylcellulose, and 17-33 kg of sodium dodecyl sulfate.

[0032] It is understandable that brittle material emboli can also be prepared using existing technologies such as gypsum-based composite materials or controllable degradable polymers.

[0033] In this embodiment, an M10 cement mortar layer is applied to the outer wall of the area corresponding to the grouting hole. After solidification, the M10 cement mortar forms a mortar bonding layer 14 with a thickness of 5 mm. The thickness of the mortar bonding layer is determined according to the opening pressure and requires corresponding tests to ensure that the brittle material plug can penetrate the mortar bonding layer under the grouting pressure during the subsequent grouting process. It can be understood that when the corresponding pressure can be guaranteed by the brittle material plug alone, the mortar bonding layer can be omitted. In this embodiment, the opening pressure of the brittle material plug is 8 MPa and 13 MPa, wherein the brittle material plug with an opening force of 13 MPa is located in the area where the helical blade is installed, so as to form the enlarged portion 22 described below in the helical blade area, and the opening pressure of the other brittle material plugs is 8 MPa.

[0034] The following is an explanation of steel pipe composite piles; please refer to [link / reference]. Figure 3 and Figure 4 The steel pipe composite pile includes the aforementioned sleeve valve steel pipe pile 100, a core filler 51, and a cement grout composite reinforcement body 21. The core filler is located within the inner cavity of the sleeve valve pipe and is formed by mixing and solidifying cement grout with graded crushed stone. It is understood that, in another embodiment, the core filler may also be formed by solidifying fine aggregate concrete.

[0035] The cement grout composite reinforcement 21 is wrapped around the sleeve valve steel pipe pile. This cement grout composite reinforcement is formed by the combination of cement grout injected into the outside of the sleeve valve steel pipe pile and the underground soil. The cement grout composite reinforcement includes five enlarged sections 22, with each set of helical blades corresponding to one enlarged section 22, and each set of helical blades located within its corresponding enlarged section. The enlarged sections are formed by radial expansion of the outer circumference of the cement grout composite reinforcement 21, wherein the outer diameter of the cement grout composite reinforcement 21 is 500-550 mm, and the outer diameter of the enlarged sections is 850-900 mm.

[0036] The construction method for the aforementioned steel pipe composite piles is described below. Please refer to [link / reference needed]. Figure 6 The construction method includes the following steps:

[0037] (1) Position the drilling rig and use the drilling rig to rotate and press the sleeve valve steel pipe pile 100 into the underground soil to the design elevation;

[0038] (2) Insert the grouting core tube 31 into the inner cavity of the sleeve valve tube 11 for segmented grouting. Please also refer to... Figure 5 The lower end of the grouting core tube is the grouting perforated tube 32, which has several grout outlet holes 321. Both ends of the grouting perforated tube are equipped with grout stop plugs 33. The grouting core tube 31, the grouting perforated tube 32 and the grout stop plugs 33 all adopt existing mature technologies, which will not be described in detail here.

[0039] During the segmented grouting process, the first cement grout enters the grouting core tube and then enters the annular cavity between the grouting perforated pipe and the sleeve valve pipe through the grout outlet 321. Driven by the first cement grout, the brittle material plug is ejected out of the grouting hole and passes through the mortar bonding layer 14, forming a hole in the mortar bonding layer. This causes the mortar bonding layer to partially or completely detach. The first cement grout is then ejected outward through the grouting hole and enters the surrounding soil, combining with the soil to form a cement grout composite solidified body 21, forming an enlarged section 22 in the corresponding area of ​​the spiral blade. The grouting pressure is 13 MPa when forming the enlarged section, and 8 MPa when grouting the remaining areas excluding the enlarged section. The water-cement ratio of the first cement grout is 0.8.

[0040] (3) Pile body filling: Graded crushed stone is filled into the sleeve valve pipe, and then the second cement grout is injected into the sleeve valve pipe from the top until the second cement grout overflows the pipe opening. The second cement grout mixes with the graded crushed stone and solidifies to form the core filling body 51. The water-cement ratio of the second cement grout is 0.6 and the grouting pressure is 3MPa.

[0041] It is understood that, in another embodiment, fine aggregate concrete can also be poured into the sleeve valve tube, and the fine aggregate concrete forms a core filler after solidification.

Claims

1. A steel pipe composite pile, characterized in that, include: The sleeve valve steel pipe pile includes a sleeve valve pipe and at least two sets of spiral blades welded to the outer wall of the sleeve valve pipe. The at least two sets of spiral blades are arranged at intervals along the axial direction. Several grouting holes are provided on the pipe wall of the sleeve valve pipe. A pre-closed grouting valve is installed on each grouting hole. The opening pressure of the pre-closed grouting valve is 5-25MPa. The core filler is located inside the sleeve valve tube; A cement grout composite reinforcement body is wrapped around a sleeve valve steel pipe pile. The cement grout composite reinforcement body is composed of cement grout injected into the outside of the sleeve valve steel pipe pile and underground soil. The cement grout composite reinforcement body includes at least one enlarged section and has a set of helical blades in at least one enlarged section.

2. The steel pipe composite pile according to claim 1, characterized in that, The core filler is made of cement grout mixed with graded crushed stone and then solidified, or of fine stone concrete that has solidified.

3. The steel pipe composite pile according to claim 1, characterized in that, The pre-closed grouting valve is a brittle material plug, which is made of gypsum-based composite material, M5-M15 cement mortar, or controllable degradable polymer.

4. The steel pipe composite pile according to claim 1, characterized in that, A sealing stud is provided at the lower end of the sleeve valve tube.

5. A construction method for steel pipe composite piles, characterized in that, Includes the following steps: (1) Rotate and press the sleeve valve steel pipe pile into the underground soil to the design elevation; the sleeve valve steel pipe pile includes a sleeve valve pipe and at least two sets of spiral blades welded on the outer wall of the sleeve valve pipe. The at least two sets of spiral blades are arranged at intervals along the axial direction. Several grouting holes are provided on the pipe wall of the sleeve valve pipe. A pre-closed grouting valve is installed on each grouting hole. The opening pressure of the pre-closed grouting valve is 5-25MPa. (2) Insert the grouting core tube into the inner cavity of the sleeve valve tube and perform segmented grouting; The lower end of the grouting core tube is the grouting perforated tube, which has several grout outlet holes. Both ends of the grouting perforated tube are equipped with grout stop plugs. (3) Pile body filling: Fill the sleeve valve pipe with graded crushed stone, and then inject cement grout into the sleeve valve pipe; or pour fine stone concrete into the sleeve valve pipe.

6. The construction method according to claim 5, characterized in that, In step (2), the grouting pressure is 5-25 MPa when performing segmented grouting.

7. The construction method according to claim 6, characterized in that, When performing segmented grouting, a grouting pressure of 5-15 MPa is used for soft soil layers and a grouting pressure of 15-25 MPa is used for dense soil layers.

8. The construction method according to claim 5, characterized in that, In step (2), when performing segmented grouting, the water-cement ratio of the cement grout used is 0.5-1.

0.

9. The construction method according to claim 5, characterized in that, In step (3), when injecting cement grout into the sleeve valve pipe, the water-cement ratio of the cement grout is 0.5-1.0, and the grouting pressure is 2-5 MPa.

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