A variable inner diameter screw pile and a non-synchronous construction method for screw piles

Abstract

The present invention discloses a variable inner diameter screw pile and a non-synchronous construction method for the screw pile, which includes a variable inner diameter screw pile body; the variable inner diameter screw pile body includes at least two screw pile segments with the same outer diameter, and the pile core diameter of at least one screw pile in the screw pile segments is different from that of the pile cores of the remaining screw pile bodies. The soil is drilled by using a soil auger drill, which reduces the requirements for the torque of the equipment during drilling. Among them, the method of pre-drilling a soil guiding hole and then re-drilling to form a pile is adopted. The soil guiding hole is drilled in the pile core part, and after the soil is drilled, the backflow pressure of the soil around the pile is relatively small. When re-drilling to form a pile, the high spiral teeth are used to sweep the soil to form a spiral, which causes little disturbance to the soil on the hole wall and has a high side bearing capacity of the pile. During the process of lifting the drill and pumping the material to form a pile, when the discharge is blocked due to the large backflow pressure of the soil layer, the method of stopping rotation and static pulling or forward rotation and lifting the drill is adopted to increase the amount of pile body concrete, so as to avoid quality accidents such as pile body diameter reduction, pile breakage, and non-compact concrete.

Description

Technical Field

[0001] The present invention relates to a screw pile, specifically to a variable inner diameter screw pile and a non-synchronous construction method for screw piles, belonging to the technical field of construction engineering. Background Art

[0002] At present, screw cast-in-place piles can be divided into several types, such as equal-diameter screw cast-in-place piles (equal outer diameter and equal inner diameter), semi-screw piles (upper straight rod section and lower screw section), and variable-diameter screw piles (fully threaded piles with a larger upper and smaller lower outer diameter of the pile body thread and pile core diameter).

[0003] For equal-diameter screw piles, since the diameter of the pile bearing part, that is, the pile core part, is smaller than that of a straight cast-in-place pile of the same specification, when the pile body is loaded, the strength of the pile body is insufficient, and the upper pile head is prone to fragmentation, and it is difficult to improve the bearing capacity compared with a straight cast-in-place pile of the same specification.

[0004] The upper straight section of the semi-screw pile is provided to increase the compressive capacity of the upper part of the pile body. Compared with the screw section, the concrete consumption is large, and the bearing capacity is equivalent to that of a straight pile of the same specification. Therefore, the overall bearing capacity needs to be improved.

[0005] For variable-diameter screw piles, the pile forming process is partial soil displacement pile forming. When the lower part of the pile body is reverse-rotated to form a screw, the soil backflow force in the pile hole is large. The fresh concrete in the single-tooth enlarged screw part will flow back to the pile body under the backflow pressure of the pile side and the overlying soil above the screw teeth. After pile forming, the effect of the single tooth on expanding the screw teeth of the pile body during reverse screw formation is not obvious. Therefore, the outer diameter of the lower pile body is smaller than that of the upper pile body. Since good soil layers are mostly deep underground in most areas, the outer diameter of the screw pile in the better soil layer is not effectively enlarged, and the bearing capacity of the lower screw pile cannot be further improved.

[0006] From the perspective of pile forming methods, the previous screw cast-in-place piles can be divided into displacement screw piles and partial displacement screw piles.

[0007] The pile forming method of a screw pile with synchronous drilling and synchronous reverse rotation and pulling out of the drill to form a pile has no soil output during drilling, which is a displacement screw pile.

[0008] The upper straight rod section of the semi-screw pile and the upper screw pile section of the variable-diameter screw pile formed by forward rotation to form a screw are partial displacement piles.

[0009] In order to achieve soil displacement pile forming and meet the pile core diameter of the lower screw pile section during reverse screw formation, various screw pile drills are different from long auger drills in that the drill core tube is thick and the drill spiral blade is thick. Such a spiral drill with a thick core tube and thick blades has much greater resistance during synchronous soil displacement drilling than the soil sampling drilling of a long auger drill.

[0010] Restricted by the limited torque of current auger drill equipment, during construction with various auger drills, in order to achieve synchronous soil squeezing and drilling, not only is the penetration rate slow in relatively hard soil layers, but also after drilling to a certain depth in non-rigid soil layers, due to the backflow of the soil in the pile hole tightly holding the drill tool, the drilling resistance increases and it is still impossible to achieve a fast drilling speed, resulting in low efficiency and difficulty in meeting the needs of current construction. In soil layers with a certain hardness, due to the overly slow soil squeezing, excessive disturbance to the soil in the pile hole occurs. After pile formation, it is difficult for the overly disturbed soil to recover to its original state. In some soil layers, the side resistance of the screw pile is even lower than that of a straight pile of the same specification. Summary of the Invention

[0011] The purpose of the present invention is to provide a variable-inner-diameter screw pile and a non-synchronous construction method for screw piles to solve the above problems.

[0012] The present invention achieves the above purpose through the following technical solutions: A variable-inner-diameter screw pile includes a variable-inner-diameter screw pile body; the variable-inner-diameter screw pile body includes at least two screw pile segments with equal outer diameters, and the pile core diameter of at least one screw pile segment among the screw pile segments is different from that of the pile cores of the remaining screw pile bodies, wherein the outer diameters of the threads of each screw pile segment are equal.

[0013] As a further scheme of the present invention: At least one screw pile segment of the variable-inner-diameter screw pile body is non-soil-squeezing hole formation.

[0014] As a further scheme of the present invention: The variable-inner-diameter screw pile body is a combined pile formed by the combination of screw pile segments and non-screw pile segments.

[0015] A non-synchronous construction method for screw piles of a variable-inner-diameter screw pile, the non-synchronous construction method for screw piles includes the following steps:

[0016] Step 1: Use a helical blade drill tool with thickened screw blades and increased screw teeth at the bottom to perform non-synchronous rotary soil-taking drilling. The soil in the pile hole moves upward with torque along with the drill tool and rises along the screw blades and is discharged out of the hole until reaching the bottom of the pile.

[0017] Step 2: Stop the rotation of the drill tool and lift the drill or lift the drill and pump materials without changing the rotation direction of the drill tool to form a dense pile end.

[0018] Step 3: After the material discharge is smooth, reverse the rotation and lift the drill. At this time, the soil between the screw blades moves downward with torque along with the drill tool and is squeezed back to the hole wall along the screw blade guide. The concrete forms the lower screw segment of the screw pile in the pile hole formed by lifting the drill, the soil squeezed back to the hole wall, and the hole wall space sheared by the rotation of the increased teeth.

[0019] Step 4: Lift the drill to the designed diameter change position of the pile body, change the rotation direction again and lift the drill and pump materials until the concrete pouring is completed to form the upper screw segment of the screw pile.

[0020] As a further solution of the present invention: after the screw pile non-synchronous construction method drills to the bottom of the pile, if the soil layer where the pile end is located is not prone to hole collapse and the material discharge is smooth, the drill can be directly rotated counterclockwise to lift and pump the material to form the lower screw pile body of the screw pile.

[0021] As a further solution of the present invention: during the non-synchronous soil sampling and drilling of the screw pile non-synchronous construction method, the penetration depth and the number of rotations of the drill within the section should be recorded in segments. If the penetration is slow (the number of rotations of the drill within the section multiplied by the thickness of the increased spiral teeth ≥ 1 / 2 of the section length), the method of pre-drilling with soil sampling and then re-drilling to form the pile should be adopted. When pre-drilling, non-displacement drilling tools such as a spiral drill without increased spiral teeth or a down-the-hole hammer should be used, and the outer diameter of the drilling tool should not be greater than the core diameter of the screw pile.

[0022] As a further solution of the present invention: the pre-drilling with soil sampling of the screw pile non-synchronous construction method can be full-length pre-drilling of the pile body or partial pre-drilling.

[0023] As a further solution of the present invention: the drill for pre-drilling with soil sampling of the screw pile non-synchronous construction method can adopt an equal-diameter spiral drill pipe and drilling tool with an outer diameter.

[0024] As a further solution of the present invention: the drill for pre-drilling with soil sampling of the screw pile non-synchronous construction method can adopt a combined spiral drill pipe and drilling tool with a gradually decreasing outer diameter from top to bottom.

[0025] As a further solution of the present invention: during the process of lifting the drill and pumping the material to form the pile in the screw pile non-synchronous construction method, in the part of forming the pile by rotating the drill counterclockwise and lifting, if the material discharge is not smooth, the rotation of the drill can be stopped, the drill can be lifted, and the material can be pumped to form a straight section or changed to forming the pile by rotating the drill clockwise and lifting and pumping the material.

[0026] As a further solution of the present invention: after pre-drilling of the screw pile non-synchronous construction method, a spiral drill with increased spiral teeth at the bottom can be used to rotate the drill clockwise and re-drill to the bottom of the pile, and then the drill can be lifted and the material can be pumped without changing the rotation direction to form the screw pile body.

[0027] The beneficial effects of the present invention are as follows: 1) In different soil layers, different pile sections are set as needed. On the premise of ensuring the integrity and density of the pile body, the outer diameter of the screw pile in the hard soil layer is further enlarged to obtain higher pile side bearing capacity;

[0028] 2) By changing the original synchronous displacement drilling method during the construction of the screw pile and using a soil sampling spiral drill to drill, the requirement for the torque of the equipment during drilling can be greatly reduced. Among them, the method of pre-drilling with soil sampling and then re-drilling to form the pile, by adopting partial pre-drilling of the pile core and during re-drilling, the increased spiral teeth sweep the soil to form a spiral, the disturbance to the soil on the hole wall is small, the pile side bearing capacity is high, avoiding the quality defect of reducing the pile side bearing capacity due to excessive disturbance of the soil around the pile, and after soil sampling drilling, the backflow pressure of the soil around the pile is small, and the increased spiral teeth of the drill can fully play the beneficial effect of expanding the height of the screw teeth of the screw pile when rotating the drill counterclockwise and lifting to form the spiral.

[0029] 3) During the process of forming a pile by pumping materials while withdrawing the drill, when encountering difficulties in discharging materials due to large backflow pressure of the soil layer, the methods of stopping rotation and static pulling or forward rotation and pulling the drill are adopted to increase the amount of pile body concrete, so as to avoid quality accidents such as pile body diameter reduction, pile breakage, and non-compact concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a pile type of the present invention;

[0031] Figure 2 It is a schematic diagram of a screw pile with a static pulling straight rod section when the drill stops rotating of the present invention;

[0032] Figure 3 It is a schematic diagram of a screw pile with an enlarged straight rod section formed by forward rotation of the drill of the present invention;

[0033] Figure 4 It is a schematic diagram of a screw pile with a dense enlarged pile end of the present invention;

[0034] Figure 5 It is a schematic diagram of a screw pile with a pile top enlarged head of the present invention;

[0035] Figure 6 It is a schematic diagram of a screw pile with a screw pile section formed by forward rotation of the drill in the lower thread section of the present invention;

[0036] Figure 7 It is a schematic diagram of a screw pile with equal outer diameters of the upper and lower thread parts and a larger upper and smaller lower pile core of the present invention;

[0037] Figure 8 It is a schematic diagram of the first construction process of the present invention;

[0038] Figure 9 It is a schematic diagram of the second construction process of the present invention;

[0039] Figure 10 It is a schematic diagram of the third construction process of the present invention.

[0040] In the figure: 1. Pile top enlarged head, 2. Positive rotation thread section, 3. Positive rotation enlarged straight rod section, 4. Static pulling straight rod section, 5. Reverse rotation thread section, 6. Dense enlarged pile end, 7. Earth auger with thickened screw blades and increased screw teeth at the bottom, 8. Long spiral earth auger, 9. Variable cross-section earth auger, 10. Screw pile drill with partial screw teeth. SPECIFIC EMBODIMENTS

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0042] Embodiment 1

[0043] Please refer to Figure 1 , a variable-inner-diameter soil-sampling screw pile, including a variable-inner-diameter screw pile body. The top of the screw pile body is a pile-top enlarged head 1 formed by the low-speed forward rotation of the drilling tool. The pile-top enlarged head 1 is connected to a forward-rotation screw section 2 formed by the forward rotation of the drilling tool. The forward-rotation screw section 2 is connected to a forward-rotation enlarged straight rod section 3. The forward-rotation enlarged straight rod section 3 is connected to a static-pulling straight rod section 4 formed by the static pulling of the drilling tool. The static-pulling straight rod section 4 is connected to the forward-rotation screw section 2. The lower end of the forward-rotation screw section 2 is connected to a reverse-rotation screw section 5 formed by the reverse rotation of the drilling tool. The reverse-rotation screw section 5 is connected to a dense enlarged pile end 6. The outer diameter of the threads of the forward-rotation screw section is equal to that of the reverse-rotation screw section, and the core diameter of the forward-rotation screw section is greater than the core diameter of the reverse-rotation screw section.

[0044] Embodiment 2

[0045] Please refer to Figure 2 , a variable-inner-diameter screw pile, including a variable-inner-diameter screw pile body; the upper part of the variable-inner-diameter screw pile body is a forward-rotation screw section 2 formed by the forward rotation of the drilling tool to form a pile, the lower part of the variable-inner-diameter screw pile body is a reverse-rotation screw section 5 formed by the reverse rotation of the drilling tool to lift the drill to form a pile, the middle of the variable-inner-diameter screw pile body is a straight rod section 4 formed by stopping rotation and static pulling, the core diameter of the forward-rotation screw section 2 is greater than the core diameter of the reverse-rotation screw section 5, and the spiral outer diameter of the forward-rotation screw section 2 is equal to that of the reverse-rotation screw section 5.

[0046] Embodiment 3

[0047] Please refer to Figure 3 , a variable-inner-diameter screw pile, including a variable-inner-diameter screw pile body; the upper part of the variable-inner-diameter screw pile body is a forward-rotation screw section 2 formed by forward rotation to form a pile, the lower part of the variable-inner-diameter screw pile body is a reverse-rotation screw section 5 formed by reverse rotation of the drilling tool to lift the drill to form a pile, the middle of the variable-inner-diameter screw pile body is a forward-rotation enlarged straight rod section 3 formed by slow forward lifting of the drill, and its slow drill-lifting speed is such that the lifting distance per rotation of the drill is not greater than the thickness of the high-pitch thread at the bottom of the drill. The core diameter of the forward-rotation screw section 2 is greater than the core diameter of the reverse-rotation screw section 5, and the outer diameter of the threads of the forward-rotation screw section 2 is equal to that of the reverse-rotation screw section 5.

[0048] Embodiment 4

[0049] Please refer to Figure 4, a variable inner diameter screw pile, comprising a variable inner diameter screw pile body; the upper part of the variable inner diameter screw pile body is a positive rotation screw thread section 2 formed by positive rotation for pile driving, the bottom of the variable inner diameter screw pile body is a dense enlarged pile end 6 formed by positive rotation and low-speed drill lifting, the upper part of the dense enlarged pile end 6 is a reverse rotation screw thread section 5 formed by reverse rotation drill lifting, the core diameter of the positive rotation screw thread section 2 is larger than the core diameter of the reverse rotation screw thread section 5, and the outer diameters of the positive rotation screw thread section 2, the reverse rotation screw thread section 5 and the dense enlarged pile end 6 are equal.

[0050] Example Five

[0051] Please refer to Figure 5 , a variable inner diameter screw pile, comprising a variable inner diameter screw pile body; the upper part of the variable inner diameter screw pile body is a positive rotation screw thread section 2 formed by positive rotation for pile driving, the lower part of the variable inner diameter screw pile body is a reverse rotation screw thread section 5 formed by reverse rotation drill lifting, the top of the variable inner diameter screw pile body is a pile top enlarged head 1 formed by positive rotation and low-speed drill lifting, the core diameter of the positive rotation screw thread section 2 is larger than the core diameter of the reverse rotation screw thread section 5, and the outer diameters of the positive rotation screw thread section 2, the reverse rotation screw thread section 5 and the pile top enlarged head 1 are equal.

[0052] Example Six

[0053] Please refer to Figure 6 , a variable inner diameter screw pile, comprising a variable inner diameter screw pile body; the upper part of the variable inner diameter screw pile body is a positive rotation screw thread section 2 formed by positive rotation for pile driving, the lower part of the variable inner diameter screw pile body is a reverse rotation screw thread section 5 formed by reverse rotation drill lifting, and a part of the lower reverse rotation screw thread section 5 of the variable inner diameter screw pile body is formed into a positive rotation screw thread section 2 by positive rotation, the core diameter of the positive rotation screw thread section 2 is larger than the core diameter of the reverse rotation screw thread section 5, and the thread outer diameters of the positive rotation screw thread section 2 and the reverse rotation screw thread section 5 are equal.

[0054] Example Seven

[0055] Please refer to Figure 7 , a variable inner diameter screw pile, comprising a variable inner diameter screw pile body; the upper part of the variable inner diameter screw pile body is a positive rotation screw thread section 2 formed by positive rotation for pile driving, the lower part of the variable inner diameter screw pile body is a reverse rotation screw thread section 5 formed by reverse rotation drill lifting, the core diameter of the positive rotation screw thread section 2 is larger than the core diameter of the reverse rotation screw thread section 5, and the outer diameters of the positive rotation screw thread section 2 and the reverse rotation screw thread section 5 are equal.

[0056] As Figure 8 described above: The method for non-synchronous pile driving of the screw pile includes but is not limited to the following three types. As Figure 1 shown, it is the first construction method, which includes the following steps:

[0057] Step 1: Rotate the soil auger 7 (the first drill tool) with thickened screw blades and heightened screw teeth at the bottom quickly in the direction of the drill tool blades to drill into the soil until reaching the bottom of the pile;

[0058] Step 2: Without changing the rotation direction, lift the drill tool at a low speed while pumping material to form the dense pile end part at the lower part;

[0059] Step 3: Change the rotation direction and lift the drill tool while pumping material in the reverse rotation to form the reverse spiral pile part with a smaller pile core diameter;

[0060] Step 4: In soil layers where the material discharge is not smooth, etc., change the rotation direction, drill and lift the drill tool forward to increase the concrete pouring volume to form the forward spiral pile part with a larger pile core diameter; the construction of this part can also be changed to stop the rotation of the drill tool and perform static pulling out to form the static pulling out straight rod section;

[0061] Step 5: Continue to rotate in the reverse direction to form the reverse spiral pile part with a smaller pile core;

[0062] Step 6: When reaching the designed diameter-changing part, lift the drill tool forward to form the forward spiral pile part with a larger pile core diameter at the upper part;

[0063] Step 7: At the pile top part, lift the drill tool with a low-speed forward rotation to form the dense pile top enlarged part.

[0064] Please refer to Figure 9 , and its second construction method includes the following steps:

[0065] Step 1: Use the long spiral soil auger 8 (the second drill tool) with spiral blades to drill into the soil until reaching the bottom of the pile. The outer diameter of the drill tool should not be greater than the pile core diameter of the spiral pile, and take out the soil in the pile hole with a diameter not greater than the pile core diameter;

[0066] Step 2: The pile hole can be backfilled with the taken-out soil chips, or directly redrilled into a pile in the pile hole;

[0067] Step 3: Use the soil auger 7 (the first drill tool) with a diameter not less than the diameter of the preformed pile hole and thickened screw blades and heightened screw teeth at the bottom to redrill to the bottom of the pile;

[0068] Step 4: Without changing the rotation direction of the drill tool, rotate forward and lift the drill tool while pumping material to form the spiral pile.

[0069] Among them, in this method, a long spiral drill tool with an outer diameter not greater than the pile core diameter of the lower reverse spiral section of the spiral pile can be used to pre-drill a hole first, and then use a spiral drill tool with heightened screw teeth and a screw blade outer diameter equal to the pile core diameter of the forward spiral section of the spiral pile to redrill to the bottom of the pile position, and then lift the drill tool in the reverse rotation while pumping material to form the lower reverse spiral section with a smaller pile core diameter. When reaching the designed diameter-changing place, rotate the drill tool forward and lift the drill tool while pumping material to form the upper forward spiral pile section with a larger pile core.

[0070] Please refer to Figure 10, its third construction method includes the following steps:

[0071] In the first step, use a variable cross-section soil sampling drill 9 (the third drill) with the outer diameter of the lower spiral blade not greater than the core diameter of the reverse spiral section of the screw pile, the length not greater than the pile length of the lower reverse spiral section of the screw pile, and the outer diameter of the upper spiral blade not greater than the core diameter of the upper positive spiral section of the screw pile to drill and form a hole by taking soil.

[0072] In the second step, backfill the pile hole or directly use a soil sampling spiral drill 7 (the first drill) with an outer diameter equal to the core diameter of the upper positive spiral section of the screw pile and thickened spiral blades and heightened spiral teeth at the bottom or a screw pile drill 10 (the fourth drill) with screw teeth in part to redrill to the bottom of the pile in the pile hole after the pilot hole.

[0073] In the third step, reverse the drill and pump the material to form the lower reverse spiral section.

[0074] In the fourth step, when reaching the designed diameter change point, change the rotation direction and rotate the drill forward and pump the material to form the upper positive spiral section of the screw pile.

[0075] Working principle: When using this variable inner diameter screw pile and the asynchronous construction method of the screw pile, set a screw pile body with a larger diameter in a better soil layer, and in different soil layers, reasonably control the soil output according to needs. On the premise of ensuring that the screw pile body forms a screw and avoiding excessive disturbance of the soil around the pile, through different drilling and pile forming methods, reduce the construction difficulty and speed up the construction progress, and further improve the side resistance of the screw pile. According to relevant specifications, the soil sampling piles can be arranged more densely and have a wider adaptability.

[0076] It should be further noted that: the problem solved by the variable inner diameter screw pile and the asynchronous construction method of the screw pile is to provide a more reasonable pile type structure, that is, the compression part of the pile body meets the stress distribution requirements of the pile body, set a screw pile body with a larger diameter in a better soil layer, and in different soil layers, reasonably control the soil output according to needs. On the premise of ensuring that the screw pile body forms a screw and avoiding excessive disturbance of the soil around the pile, through different drilling and pile forming methods, reduce the construction difficulty and speed up the construction progress, and further improve the side resistance of the screw pile.

[0077] The difference between this variable inner diameter screw pile and other variable diameter screw piles lies in: for other variable diameter screw piles, both the inner diameter and the outer diameter are larger at the top and smaller at the bottom, while for this variable inner diameter screw pile, only the inner diameter is different and the outer diameter of the pile body is equal up and down; this variable inner diameter screw pile also adds multi-stage diameter change and the variable diameter screw pile is composed of multiple segments (three segments and above); the variable diameter screw piles in the existing technology are all full-thread piles, while for this pile type, some paragraphs can be straight according to actual needs.

[0078] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0079] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A variable inner diameter screw pile, including the pile body of the variable inner diameter screw pile, is constructed by a non-synchronous construction method. It is characterized in that: The non-synchronous construction method includes the following steps: Step 1: Use a helical blade drill tool with thickened screw blades and increased screw teeth at the bottom to rotate non-synchronously for soil extraction and drilling. The soil in the pile hole moves upward with torque along with the drill tool and rises along the screw blades and is discharged out of the hole until the bottom of the pile is drilled to. Step 2: Stop the rotation of the drill tool and lift the drill or lift the drill and pump materials without changing the rotation direction of the drill tool to form the pile end. Step 3: After the material discharge is smooth, reverse the rotation and lift the drill. At this time, the soil between the screw blades moves downward with torque along with the drill tool and is squeezed back to the hole wall along the screw blades. The concrete forms the lower threaded section of the screw pile in the pile hole formed by lifting the drill, the soil squeezed back to the hole wall, and the hole wall space sheared by the rotation of the enlarged teeth. Step 4: Lift the drill and pump materials to the design variable diameter position of the pile body, change the rotation direction again, lift the drill and pump materials until the concrete pouring is completed, and lift the drill tool out of the pile hole to form the upper threaded section of the screw pile. The pile body of the variable inner diameter screw pile includes at least two screw pile sections with the same outer diameter. At least one of the screw pile sections has a pile core diameter different from that of the pile cores of the other screw pile bodies. Among them, the outer diameters of the threads of each screw pile section are equal. At least one screw pile section of the pile body of the variable inner diameter screw pile is formed by non-excavation or the pile body of the variable inner diameter screw pile is a combined pile composed of screw pile sections and non-screw pile sections.

2. A variable inner diameter screw pile according to claim 1, It is characterized in that: After the non-synchronous construction method drills to the bottom of the pile, if the soil layer where the pile end is located is not easy to collapse and the material discharge is smooth, the drill can be directly reversed, lifted and pumped with materials to form the lower screw pile body.

3. A variable inner diameter screw pile according to claim 1, It is characterized in that: During the non-synchronous soil extraction and drilling of the non-synchronous construction method, the penetration and the number of rotations of the drill tool within the section should be recorded in segments. If the penetration is slow, pre-drilling for soil extraction should be adopted. When pre-drilling, a helical drill tool without increased screw teeth or a down-the-hole hammer should be used, and its outer diameter should not be greater than the pile core diameter of the screw pile.

4. A variable inner diameter screw pile according to claim 1, It is characterized in that: The pre-drilling for soil extraction of the non-synchronous construction method is a full-length hole or a partial hole for the pile body.

5. A variable inner diameter screw pile according to claim 1, It is characterized in that: The drill rods and drill tools for soil extraction in the non-synchronous construction method use drill rods and drill tools with the same outer diameter or a combined type of drill rods and drill tools with a larger upper outer diameter and a smaller lower outer diameter.

6. A variable inner diameter screw pile according to claim 1, It is characterized in that: During the process of lifting the drill and pumping materials to form a pile in the non-synchronous construction method, in the part of reverse rotation, lifting and forming a pile, if the material discharge is not smooth, the rotation of the drill tool can be stopped and the drill tool can be lifted to form a straight section or changed to forward rotation, lifting the drill and pumping materials to form a pile.

7. A variable inner diameter screw pile according to claim 1, It is characterized in that: After the pre-drilling in the non-synchronous construction method, a helical drill tool with increased screw teeth at the bottom can be used to rotate forward and re-drill to the bottom of the pile, and then lift the drill and pump materials directly without changing the rotation direction to form the screw pile body.

Images