A pile head and cast-in-place pile construction method for preventing pile bottom sediment

Abstract

A pile head for preventing sedimentation at the bottom of piles, comprising a columnar pile head body, a plurality of connecting strips are arranged on the upper end face of the pile head body for interlacing with a steel cage, a plurality of embedded protrusions are arranged on the lower end face for inserting sediment into a hard soil layer, and a plurality of filling holes are arranged on the lower end face of the pile head body for allowing sediment to squeeze in so as to reduce the sediment thickness between the lower end faces of the pile head body. The advantage is that by arranging the pile head at the bottom of the cast-in-place pile, the adverse effects of sediment on the pile body can be effectively eliminated, thereby improving the safety performance of the cast-in-place pile. The structure of the pile head is simple and reasonable, the cost as a prefabricated part is not high, and the installation and construction are convenient.

Description

Technical Field

[0001] The invention relates to the technical field of cast-in-place pile construction, in particular to a pile head to prevent pile bottom sedimentation and a cast-in-place pile construction method. Background Art

[0002] During the construction of cast-in-place piles, the soft soil is often prone to collapse after unloading, and mud wall protection is required. After the hole is dug and before pouring concrete, it is often necessary to clean the sediment to prevent the soft soil mud or mud skin from sinking to the bottom of the hole, thereby avoiding the formation of pile bottom sediment. The existing removal technology cannot completely remove the sediment, so there are often pile positions where the sediment thickness exceeds the standard in the quality inspection of the same batch of pile foundations. The "Code for Acceptance of Construction Quality of Building Foundation Engineering" GB50202-2018 stipulates that the sediment thickness of the end-bearing pile is ≤50mm and the sediment thickness of the friction pile is ≤150mm during construction. In theory, the sediment is allowed to exist within a reasonable range. There is a certain uncertainty in the existing sediment cleaning technology, which poses a great threat to the quality of the project. When the sediment thickness exceeds the requirements of the specification, if the pile foundation is poured without cleaning, it will inevitably cause the pile foundation to sink, affecting the safety of the upper building. The existing technology also has a secondary hole cleaning and hole inspection after pouring underwater concrete, but this work is difficult and not conducive to on-site construction. Summary of the invention

[0003] The first purpose of the present invention is to provide a pile head for preventing pile bottom sediment in order to eliminate the adverse effects of the bottom sediment on the pile structure.

[0004] The second purpose of the present invention is to reduce the hole cleaning requirements and avoid secondary hole cleaning during cast-in-place pile construction, solve the adverse effects of sediment on cast-in-place piles, and provide a construction method for cast-in-place pile sediment treatment.

[0005] The present invention is achieved through the following technical solutions:

[0006] A pile head for preventing pile bottom sedimentation comprises a columnar pile head body, a plurality of connecting strips are arranged on the upper end surface of the pile head body for being inserted and interlaced with a steel cage, a lower end surface is a plane surface for supporting a hard soil layer through sedimentation, a plurality of embedding protrusions are arranged on the lower end surface of the pile head body for inserting sedimentation into a soft soil layer, and a plurality of filling holes are arranged on the lower end surface of the pile head body for allowing sedimentation to be squeezed in so as to reduce the sediment thickness between the lower end surfaces of the pile head body.

[0007] As an improvement of the above scheme, it also includes an inner cage frame, which is formed by winding steel bars. The pile head body wraps the inner cage frame, and several steel bars of the inner cage frame extend from the upper end surface of the pile head body to form the connecting strip, and the extending length is not less than 20 cm to ensure good connection performance between the pile head and the pile body after the steel cage is inserted into each other and concrete is poured.

[0008] As an improvement of the above solution, the number of the connecting strips is no less than 30.

[0009] As an improvement of the above solution, the embedding protrusion is columnar and has a tapered portion at one end away from the pile head body, which is conducive to insertion into hard soil layers and improves the stability of the pile head.

[0010] As an improvement of the above solution, the filling hole is a through hole that passes through the upper and lower end surfaces of the pile head body, thereby increasing the volume of the filling hole and avoiding the air pressure problem that makes it difficult for sediment to squeeze in.

[0011] As an improvement to the above solution, a lifting ring is provided on the upper end surface of the pile head body to facilitate lifting the pile head from above the pile hole during construction.

[0012] As an improvement of the above solution, the steel bars of the inner cage frame are threaded steel bars to improve the bonding between the pile head body and the steel cage.

[0013] As an improvement of the above solution, the pile head body and the embedded protrusion are made of concrete.

[0014] A method for constructing a bored pile, wherein the method uses the above-mentioned pile head for preventing pile bottom sedimentation, and the specific steps are as follows:

[0015] S1. Construction preparation, determine the specifications of the bored piles, drilling rigs, and drilling tools, determine the pile head to prevent pile bottom sedimentation according to the specifications of the bored piles and prefabricate them;

[0016] S2. Positioning and setting out, plane measurement, elevation measurement, pile position measurement, and control the deviation within the specified range according to the pile hole specifications;

[0017] S3. Drilling rig installation and positioning, pre-buried casing, drilling;

[0018] S4. Clean the bottom sediment of the hole and measure and inspect the pile hole. Embed the prefabricated anti-pile bottom sediment pile head of S1 into the pile hole with the protrusion facing downward, and apply pressure to the pile head from top to bottom;

[0019] S5. Place the steel cage and pour underwater concrete.

[0020] As an improvement of the above scheme, the condition for determining the pile head for preventing pile bottom sedimentation according to the specifications of the bored pile is that the outer diameter of the pile head body is the same as the outer diameter of the bored pile, and an error within a reasonable range is allowed here.

[0021] The present invention has the following beneficial effects:

[0022] 1. By setting the pile head at the bottom of the bored pile, the adverse effects of sediment on the pile body can be effectively eliminated, and the safety performance of the bored pile can be improved. The structure of the pile head is simple and reasonable, the cost as a prefabricated part is not high, and the installation and construction are convenient.

[0023] 2. When the pile head provided by the present invention is provided during the construction of cast-in-place piles, the requirements for sediment cleaning and detection can be reduced, thereby improving the quality of the project and the work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a three-dimensional structural diagram of an anti-pile bottom sediment pile head described in Example 1.

[0025] Figure 2 This is a three-dimensional structural diagram of an anti-pile bottom sediment pile head described in Example 2.

[0026] Figure 3 A three-dimensional structural diagram of a pile head for preventing pile bottom sedimentation according to Example 2 from another angle

[0027] Figure 4 This is a schematic diagram of the pile head construction status in a cast-in-place pile construction method described in Example 3.

[0028] Explanation of the reference numerals: pile head body 1, inner cage frame 2, connecting bar 3, embedded protrusion 4, filling hole 5, conical part 6, sediment 7, hard soil layer 8. DETAILED DESCRIPTION

[0029] Example 1

[0030] like Figure 1 As shown, a pile head for preventing pile bottom sedimentation includes a columnar pile head body 1 and an inner cage frame 2 (partially not shown). The pile head body 1 is cylindrical, and its diameter is slightly smaller than the designed pile diameter. A plurality of connecting strips 3 are provided on the upper end surface of the pile head body 1 for interlacing with the steel cage, and the lower end surface is a plane for supporting the hard soil layer through sedimentation. A plurality of filling holes 5 are provided on the lower end surface of the pile head body 1 for allowing sedimentation to squeeze in so as to reduce the sedimentation thickness between the lower end surfaces of the pile head body 1. The filling holes 5 are through holes that penetrate the upper and lower end surfaces of the pile head body 1 to increase the volume of the filling holes 5.

[0031] Example 2

[0032] like Figure 2 , Figure 3As shown, a pile head for preventing pile bottom sedimentation, which is different from Example 1, has a plurality of embedded protrusions 4 on the lower end surface for inserting sediment into the soft soil layer, and a plurality of filling holes 5 are provided on the lower end surface of the pile head body 1 for allowing sediment to be squeezed in so as to reduce the sediment thickness between the lower end surfaces of the pile head body 1. The filling holes 5 are through holes, which penetrate the upper and lower end surfaces of the pile head body 1 to increase the volume of the filling holes 5. The inner cage frame 2 is wound by steel bars, and the pile head body 1 wraps the inner cage frame 2. Several steel bars of the inner cage frame 2 extend from the upper end surface of the pile head body 1 to form the connecting strip 3, and the extending length is 30 mm to ensure good connection performance between the pile head and the pile body after mutual insertion with the steel cage and pouring concrete. There are 30 connecting strips 3. The embedded protrusion 4 is columnar and has a tapered portion 6 at one end away from the pile head body 1, which is conducive to inserting into the hard soil layer and improving the stability of the pile head. A lifting ring (not shown) is provided on the upper end surface of the pile head body 1 to facilitate the pile head to be lifted from above the pile hole during construction. The steel bars of the inner cage frame 2 are threaded steel bars to improve the bonding between the pile head body 1 and the steel cage. The pile head body 1 and the embedded protrusion 4 are made of concrete.

[0033] Example 3

[0034] like Figure 4 As shown, a method for constructing a bored pile, using an anti-pile bottom sediment pile head described in Example 1, the specific steps are as follows:

[0035] S1. Construction preparation, confirm the geology, if it is a hard soil layer, select the pile head of Example 1, if it is a soft geology, select the pile head of Example 2, determine the outer diameter of the bored pile to be 800mm, drill rig, drilling tools, and determine the outer diameter of the pile head body 1 of the pile head for preventing pile bottom sedimentation to be 800mm according to the outer diameter of the bored pile. An error within a reasonable range is allowed here.

[0036] S2. Positioning and setting out, plane measurement, elevation measurement, pile position measurement. The allowable deviation of pile position is: for diameter <1000mm, the allowable deviation is 70+0.1Hmm; for diameter ≥1000mm, the allowable deviation is 100+0.1Hmm.

[0037] S3. Drilling rig installation and positioning, site leveling, to meet construction conditions; according to the design documents, select appropriate machinery and equipment; machinery and equipment enter the site, and place them in place according to the planned area, and large equipment is assembled and repaired. Pre-buried casing, casing should be buried accurately, stably, vertically, and the soil should be compacted around it. The deviation between the center line of the casing and the center of the pile position shall not exceed 30mm; the top surface of the casing should be 2m higher than the construction water level or groundwater level, and 0.5m higher than the construction ground; the top surface of the casing sunk in place is allowed to deviate by 50mm, and the verticality is allowed to deviate by 1%. During drilling, the verticality of the hole should be guaranteed, and the allowable deviation is 1%; before drilling, prepare mud according to the design and specification requirements.

[0038] S4. Clean the sediment at the bottom of the hole and measure and inspect the pile hole. The sediment cleaning requirement here can be equal to or float between the allowable values. The hole depth is not less than the design value. If rock embedding is required, the depth is not less than the design value. The verticality deviation is ≤1%. The S1 prefabricated anti-pile bottom sediment pile head embedding protrusion 4 is hung downward into the pile hole, and pressure is applied to the pile head from top to bottom. The sediment 7 at the bottom of the pile hole enters the filling hole 5 due to the squeezing of the pile head. If it is a soft soil layer, the embedding protrusion 4 is inserted into the soft soil layer 8 through the sediment.

[0039] S5. Place the steel cage. When transporting and hoisting the steel cage, protective measures must be taken to prevent the steel cage from deforming. Use a flatbed truck to transport it to the work site, and use a crane to hoist the steel cage into the hole. A dedicated person is assigned to direct the crane operation. There are two hoisting points. During the hoisting process, it must be gently lifted and placed. After the steel cage is fully lifted, it should be slowly moved to the corresponding pile hole. When the steel cage is hoisted into the hole, the center of the steel skeleton should be aligned with the pile hole and then inserted into the hole. During the lowering process, the steel cage should be kept vertical and not allowed to touch the inner wall of the pile hole. Due to the existence of the pile head, the work process of secondary hole cleaning and hole inspection is omitted, which improves work efficiency. Lower the catheter. When the catheter is installed, the joints are tightly connected. A sealing ring is set at each joint connection to prevent the catheter from leaking air and water, pour underwater concrete, and pull out the catheter.

[0040] The above detailed description is a specific description of a feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the patent scope of this case.

Claims

1. A pile head for preventing pile bottom sedimentation, characterized in that: It comprises a columnar pile head body and an inner cage frame, wherein a plurality of connecting strips are arranged on the upper end face of the pile head body, the lower end face is a plane, and a plurality of filling holes are arranged on the lower end face of the pile head body; the inner cage frame is formed by winding steel bars, the pile head body wraps the inner cage frame, a plurality of steel bars of the inner cage frame extend from the upper end face of the pile head body to form the connecting strips, and the extending length thereof is not less than 20 cm; a plurality of embedding protrusions are arranged on the lower end face of the pile head body; the embedding protrusions are columnar and a conical portion is arranged at one end away from the pile head body; the lower end face is a plane and can support the hard soil layer through sediment, the plurality of embedding protrusions are used to insert the sediment into the soft soil layer, and the plurality of filling holes are used to squeeze the sediment in so as to reduce the sediment thickness between the lower end faces of the pile head body.

2. The pile head for preventing pile bottom sedimentation according to claim 1, characterized in that: The filling hole is a through hole that passes through the upper and lower end surfaces of the pile head body.

3. The pile head for preventing pile bottom sedimentation according to claim 1, characterized in that: A lifting ring is arranged on the upper end surface of the pile head body.

4. The pile head for preventing pile bottom sedimentation according to claim 1, characterized in that: The steel bars of the inner cage frame are threaded steel bars.

5. The pile head for preventing pile bottom sedimentation according to any one of claims 1 to 4, characterized in that: The pile head body and the embedded protrusion are made of concrete.

6. A method for constructing a bored pile, characterized in that: The method uses the pile head for preventing pile bottom sedimentation according to any one of claims 1 to 5, and the specific steps are as follows: S1. Construction preparation, determine the specifications of the bored piles, drilling rigs, and drilling tools, determine the pile head to prevent pile bottom sedimentation according to the specifications of the bored piles and prefabricate them; S2. Positioning and setting out, plane measurement, elevation measurement, pile position measurement, and control the deviation within the specified range according to the pile hole specifications; S3. Drilling rig installation and positioning, pre-buried casing, drilling; S4. Clean the bottom sediment of the hole and measure and inspect the pile hole. Embed the prefabricated anti-pile bottom sediment pile head of S1 into the pile hole with the protrusion facing downward, and apply pressure to the pile head from top to bottom; S5. Place the steel cage and pour underwater concrete.

7. A cast-in-place pile construction method according to claim 6, characterized in that: The condition for determining the pile head for preventing pile bottom sedimentation according to the specifications of the bored pile is that the outer diameter of the pile head body is the same as the outer diameter of the bored pile.

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