An expanding pile foundation structure on coral sand and a construction method

Abstract

The application provides an expansion pile foundation structure on coral sand and a construction method, a prefabricated pile body is composed of a plurality of separated small piles; a middle part of the prefabricated pile body is provided with a hollow structure, the hollow structure is used for inserting a pile pressing iron rod and an internal support structure into the hollow structure when the prefabricated pile body is driven into the coral sand; after the internal support structure is inserted into the hollow structure, a reserved space is formed between the outer wall of the internal support structure and the inner wall of the hollow structure; and grouting is carried out in the reserved space. The pile foundation structure is simple in operation and convenient to implement experiments, can reach the construction standard, can effectively solve the settlement problem of the pile foundation on the coral sand foundation, is beneficial to the stability of the upper structure of the pile foundation, and ensures the safe construction of the upper building.

Description

Technical Field

[0001] This invention belongs to the field of coral sand geological pile foundation technology, and in particular relates to an expansion pile foundation structure and construction method on coral sand. Background Technology

[0002] In recent years, economic and social development has led people to place increasing emphasis on building quality while pursuing performance. With the continuous increase in high-rise buildings, the requirements for building foundations have also become higher, resulting in significant development of pile foundations. However, many technical problems still need to be solved in actual construction. Due to the weakness of shallow strata, low soil bearing capacity, and large natural foundation deformation, the load is relatively large. Buildings with strict deformation requirements place even stricter demands on pile foundations. Ordinary pile foundations are prone to settlement in soft soils such as coral sand. Furthermore, due to a lack of understanding of the underground soil conditions, pile foundations are often abandoned after collapse, resulting in waste and hindering reuse. Re-drilling requires expensive costs, which is detrimental to subsequent work. Moreover, the methods for strengthening pile foundations are limited and unsuitable for handling various situations. A single grouting method is insufficient for solving problems in multiple scenarios. Different grouting methods for the same type of pile foundation yield different results depending on the terrain, which is detrimental to the stability of the pile foundation. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a pile foundation structure and construction method on coral sand foundations. This pile foundation structure is simple to operate and easy to implement experimentally, meeting construction standards and effectively solving the settlement problem of pile foundations on coral sand foundations. It is beneficial to the stability of the superstructure and ensures the safe construction of the superstructure. This structure enhances the frictional resistance at the pile ends through various methods and utilizes different construction techniques. This method increases the stability of the pile foundation on coral sand while saving significant costs. Furthermore, due to the use of precast piles and mechanized construction, the construction time is greatly reduced.

[0004] To achieve the aforementioned technical features, the present invention aims to provide an expansion pile foundation structure on coral sand, comprising a precast pile body composed of multiple separate small piles; the middle portion of the precast pile body is configured as a hollow structure, which is used to insert a driving pile rod and an internal support structure when the precast pile body is driven into the coral sand; after the internal support structure is inserted later, a reserved space is formed between the outer wall of the internal support structure and the inner wall of the hollow structure; grouting is then performed inside the reserved space.

[0005] The top of the precast pile body is made into a downward conical structure. The diameter of the selected pile driving iron rod is larger than the inner diameter of the hollow structure of the precast pile body, so that the pile driving iron rod has an initial squeezing force in all directions while driving the pile downward.

[0006] The precast pile body has been cut into multiple parts before insertion. The cut parts are divided into the required number of parts according to the specific engineering needs. The outer surface of the precast pile body is provided with a spiral structure. The spiral structure is used to enhance the friction of the pile side. At the same time, the spiral pile driving method is used during pile driving, so that the entire pile body is like a screw, and the pile body is screwed into the coral sand foundation.

[0007] The internal support structure inserted inside the precast pile body has a concave polygonal cross section. The number of convex corners of the internal support structure is determined according to the actual number of parts after the precast pile body is cut. The internal support structure is made of high-strength steel. The apex of the convex corner of the internal support structure contacts the inner wall of the precast pile body. The middle of the internal support structure is a small-sized pile driving iron rod. The small-sized pile driving iron rod has threads engraved on the outside. A movable steel sleeve with an inner diameter larger than the diameter of the small-sized pile driving iron rod is installed on the outside of the small-sized pile driving iron rod. The movable steel sleeve is connected to the telescopic part of the internal support structure through the support iron rod, and the connection is made by a movable hinge.

[0008] The internal support structure is used to provide internal support when the precast pile is driven into the ground. After the internal support structure is placed, the pile driver pushes the movable steel sleeve. The support rods on the side of the movable steel sleeve push the internal support structure to expand. After the expansion is completed, the movable steel sleeve is fixed by unscrewing the small pile driving rod with a ring nut, thereby squeezing the precast pile body to bulge outward and increasing the pile side friction. After the precast pile body is opened by the support rods, magnetic grout is injected into the space to drive away water and expand cement grout to squeeze the precast pile body to both sides.

[0009] Multiple pre-reserved reinforcing bars are left on the side of the combined pile of the small pile, and multiple pre-reserved reinforcing bar holes are also reserved. The positions of the reinforcing bar holes and the pre-reserved reinforcing bars are staggered, and one end of the pre-reserved reinforcing bars is above the ground after insertion. After the pile driving is completed and the expansive concrete is poured, the pre-reserved reinforcing bars can form a new pile structure with the concrete, increasing the integrity of the pile.

[0010] The small pile has multiple small blocks inside that can move obliquely upwards, forming a piston structure. The front part of the small block is set in the shape of a spike, and the whole is cylindrical and conical. The small block is physically attached to the inner wall of the pile, and a protrusion is set at the bottom to prevent the small block from slipping.

[0011] When the small pieces are bonded together, ensure a tight bond but not a complete lock. When the expanding cement grout is added to the hollow structure, the expanding and squeezing action of the expanding cement grout will push the small pieces upward. When the pile is recovered, because the small pieces are tilted upward, after vibration during pile extraction, when the expanding cement grout falls off, the piston structure will also fall back to its original position under the action of vibration and gravity, making it easier to pull out the pile.

[0012] When the precast pile body is used in an underwater environment, some pre-drilled holes for concrete blocks are reserved in the precast pile body during the prefabrication of the lower pile body for inserting magnetic concrete blocks.

[0013] The magnetic concrete block is made by adding some waste magnetizable slag and steel scrap to the concrete during the manufacturing process. After the concrete block is precast, it is magnetized using a magnetizer and then placed into the reserved hole on the lower side of the precast pile body, so that the lower side of the precast pile body is magnetic. The magnetic concrete block can be set on the inner or outer side of the pile according to different needs.

[0014] After the entire precast pile body is inserted into the middle of the coral sand foundation, in the case of a water-rich environment, magnetic grout is first added into the gap formed between the precast pile body and the internal support structure to fill the inside of the pile body. Since there is magnetic attraction at the bottom of the pile end, the injection of magnetic grout will play a role in driving water and draining water. Then, expansive concrete is added to expand the entire pile body as a whole.

[0015] The precast pile body is filled inside and pressurized. As needed, an independent pile foundation can be adopted, or the pile cap plate can be connected by a steel reinforcement structure reserved at the top of the precast pile body to ensure the stability of its pile cap structure.

[0016] A construction method for an expanded pile foundation structure on coral sand includes the following steps:

[0017] Step 1, Prepare materials: Prepare the steel pipes, steel bars and steel plates required for the preparation of the precast pile body, magnetic concrete blocks, pile caps, internal support structures and piston structures, and prepare the expansion cement slurry and magnetic mortar required for subsequent pouring.

[0018] Step 2, formwork: Combine several small piles, magnetic concrete blocks and piston structure into a specific structural form, and form the skeleton structure of the precast pile body after combination.

[0019] Step 3, casting of the precast pile body: pour concrete into the mold of the small pile in step 2 and compact the concrete. Note that during the casting process, reserve the piston structure and the cavity of the magnetic concrete block. Use cover plates to seal the pipe openings in these two places to prevent blockage of the reserved holes.

[0020] Step 4: Assemble the magnetic concrete block, the precast pile body, the internal support structure, and the piston structure.

[0021] Method 1, Step 5.1: During the construction of pile holes for the coral sand foundation, after driving the piles, expandable cement grout is injected. A pile driver is used to construct the pile holes in the coral sand foundation. The pile body is shallowly inserted into the coral sand foundation. Then, the pile driving rod is inserted into the central space of the pile. The pile driving rod is initially pressurized with a rammer. At the same time, a hole-enlarging cover is added to the pile opening to prevent it from collapsing under pressure. Then, the entire precast pile body is screwed downwards into the coral sand foundation while being pressurized. The gaps in the pile foundation are initially filled with soil to make it compact.

[0022] Step 6.1: After the entire precast pile body is inserted, replace it with a smaller diameter pile driving iron rod, and then insert the movable steel sleeve of the internal support structure. Use the pile driving machine to open it, leaving a part of the grouting space as the grouting reserved space. Then, grouting is carried out in the grouting reserved space.

[0023] Step 7.1, grouting at the bottom of the pile foundation: First, inject magnetic grout into the reserved grouting space using the grouting pipe. Due to the attraction of the magnetic concrete block in the lower section, the magnetic grout first repairs and fills the gaps generated during pile driving, and at the same time drives out the water inside the precast pile body.

[0024] Step 8.1: After all the water in the grouting space has been drained and the magnetic grouting is completed, pour in expansive concrete, compact it, and form a bottom expansion zone. The expansion zone pushes the piston structure to expand outward.

[0025] Step 9.1: After the expansive concrete has filled and solidified, remove the expansion cap, then backfill to fill the remaining gaps and compact it continuously.

[0026] Step 10.1: After the concrete has solidified and expanded, allow it to cool before connecting and fixing the foundation plate to the pre-reserved steel reinforcement structure.

[0027] Step 11.1 After the pile structure is completed, first remove the pile cap plate, and then scale down the internal support structure;

[0028] Step 12.1 After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the expansive concrete inside to fall off and the piston structure to retract. Then, the entire pile body is rotated and pulled out of the foundation with a pile extractor to complete the pile structure recovery.

[0029] Method 2, Step 5.2: When constructing pile holes for the coral sand foundation, inject expansive cement grout before pile driving. Use a pile driver to construct pile holes for the coral sand foundation. First, assemble the precast pile body with the internal support structure to ensure the internal support structure is open. After assembly, pour expansive cement grout directly into the central reserved system. After the expansive cement grout has initially set, use a rammer to apply initial pressure at the end of the internal support structure. At the same time, cover the pile opening with an enlarged hole cover to prevent it from collapsing under pressure. Then, while applying pressure, screw the entire precast pile body downwards into the coral sand foundation. Then, use soil to initially fill the gaps in the pile foundation and compact it.

[0030] Step 6.2: After the concrete has solidified and expanded, allow it to cool before connecting and fixing the foundation plate to the pre-reserved steel reinforcement structure.

[0031] Step 7.2: After the pile structure is completed, first remove the pile cap plate, and then scale down the internal support structure.

[0032] Step 8.2: After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the internal expansive concrete to fall off, the piston structure to retract, and then the entire pile body is rotated and pulled out of the foundation by a pile extractor to complete the pile structure recovery.

[0033] The present invention has the following beneficial effects:

[0034] 1. This invention provides a novel pile foundation structure that can be implemented at a low cost with relatively low construction difficulty. It effectively solves the settlement problem of pile foundations on coral sand foundations, promotes the stability of the superstructure, and ensures the safe construction of the superstructure. This structure enhances the frictional resistance at the pile ends through various methods, which increases the stability of the pile foundation on coral sand while saving significant costs. Furthermore, the precast piles greatly reduce construction time.

[0035] 2. By setting a toothed rough structure on the outer surface of the precast pile, the frictional resistance coefficient between the pile side and the coral sand foundation is increased. At the same time, due to the toothed contact surface, the contact area between the pile side and the coral sand foundation is also increased. Under the same external force conditions, the pile foundation will be subject to greater pile side friction. In addition, the rough toothed structure is made into a threaded structure. During pile driving construction, the pile can be screwed into the coral sand foundation. At the same time, when it is pulled out for recycling, it can be easily screwed out according to the threaded structure.

[0036] 3. By adding magnetic concrete blocks to the lower part of the precast pile body, the entire lower section of the pile body becomes magnetic. When the pile body is driven underwater, magnetic grout is injected into the middle of the pile body. Due to the characteristics of the magnetic grout, some of the water flowing into the gaps of the pile body underwater will be driven away. Then, the magnetic concrete blocks will attract and guide the cracks at the lower end of the pile body and fill the bottom of the pile body.

[0037] 4. Insert the internal support structure through the central pre-reserved system of the precast pile. After the pile is driven into the coral sand foundation, insert the internal support structure and use a pile driver to open the internal support structure, further pressing the pile sides into the foundation.

[0038] 5. After the precast pile body is opened by the internal support structure, expansive cement grout is added. When the expansive cement grout expands, the force it releases will push the separated small piles outward, allowing them to embed more deeply into the coral sand. During the process of the small piles being pushed outward, the piston structure on the side of the pile will also be pushed outward by the expansion force, thus inserting it into the coral sand. The entire pile body will be opened by the expansive cement grout, allowing it to embed more deeply, thereby further increasing the pull-out resistance of the pile foundation and making its bearing capacity greater.

[0039] 6. By pre-reserving steel reinforcement holes between the small piles, the integrity between the small piles will be destroyed after the main pile is opened by the expanding cement grout. At this time, the pre-reserved steel reinforcement will play a role. When the expanding cement grout expands and spreads, it will penetrate into the small piles and contact and bond with the pre-reserved steel reinforcement to form a unified whole. In this way, a good integrity can be maintained even after the pile end is opened.

[0040] 7. The entire pile structure can be recycled by scaling up and down the internal support structure. When the pile is no longer needed for recycling, the internal support structure is reduced in size, restoring part of the central reserved space. The overall structure of the expansive concrete is destroyed, and then it is detached by shaking. At the same time, the piston structure of the pile falls back to its initial position, completing the pile recycling. Attached Figure Description

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Figure 1 This is a front view of the overall device of the present invention.

[0043] Figure 2 This is a schematic diagram of the connecting bars between the small piles of the present invention.

[0044] Figure 3 This is a schematic diagram of the reserved connecting bars and reserved holes on a single small pile of the present invention.

[0045] Figure 4 This is a front view of a single piling of the present invention.

[0046] Figure 5 It is a pile-side threaded structure.

[0047] Figure 6 This is a top view of the initial state of the internal support structure.

[0048] Figure 7 Top view showing the internal support structure in its unfolded state.

[0049] Figure 8 This is an overall diagram of the initial state of the internal support structure.

[0050] Figure 9 An overall view of the internal support structure in its extended state.

[0051] Figure 10 This is an overall diagram of the initial state of the internal support structure and pile body combination.

[0052] Figure 11 This is an overall diagram showing the combined open state of the internal support structure and piles.

[0053] Figure 12 This is an overall diagram showing the connection between the pile cap and the pile. Detailed Implementation

[0054] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0055] Example 1:

[0056] See Figure 1-12 An expansion pile foundation structure for coral sand is disclosed, comprising a precast pile body 1, which is composed of multiple separate small piles 2. The middle portion of the precast pile body 1 is designed as a hollow structure, into which driving rods and internal support structures are inserted during the driving of the precast pile body into the coral sand. After the internal support structure is inserted later, a reserved space is formed between the outer wall of the internal support structure and the inner wall of the hollow structure. Grouting is then performed within this reserved space. This pile foundation structure is simple to operate and easy to implement experimentally, meeting construction standards and effectively solving the settlement problem of pile foundations on coral sand foundations. It is beneficial to the stability of the superstructure and ensures the safe construction of the superstructure. This structure enhances the frictional resistance at the pile ends through various methods and utilizes different construction methods. This approach increases the stability of the pile foundation on coral sand while saving significant costs. Furthermore, the use of precast piles and mechanized construction greatly reduces the construction time.

[0057] Furthermore, the top of the precast pile body 1 is made into a downward-pointing conical shape, and the diameter of the selected pile-driving iron rod is larger than the inner diameter of the hollow structure of the precast pile body 1, so that the pile-driving iron rod has an initial squeezing force in all directions while driving the pile downward. This squeezing increases the friction on the outer side.

[0058] Furthermore, the precast pile body 1 has been cut into multiple parts before insertion. The number of parts cut is determined according to the specific engineering needs. The outer surface of the precast pile body 1 is provided with a spiral structure 7. The spiral structure 7 is used to enhance the friction on the pile side. At the same time, during pile driving, a spiral driving method is used to make the entire pile body resemble a screw, screwing the pile body into the coral sand foundation. The spiral structure 7 improves the convenience of subsequent screwing operations of the precast pile body 1.

[0059] Furthermore, the internal support structure inserted inside the precast pile body 1 has a concave polygonal cross-section. The number of convex angles of the internal support structure is determined according to the actual number of parts after the precast pile body 1 is cut. The internal support structure is made of high-strength steel. The apex of the convex angle of the internal support structure contacts the inner wall of the precast pile body 1. The middle of the internal support structure is a small-sized pile driving iron rod 8. The small-sized pile driving iron rod 8 has threads engraved on its outer side. A movable steel sleeve with an inner diameter larger than the diameter of the small-sized pile driving iron rod 8 is installed on the outer side of the small-sized pile driving iron rod 8. The movable steel sleeve is connected to the telescopic part 10 of the internal support structure through the support iron rod. A movable hinge 11 is used at the connection point; the internal support structure is used to provide internal support when the precast pile is driven into the ground. After the internal support structure is placed, the pile driver pushes the movable steel sleeve, and the support iron rod on the side of the movable steel sleeve pushes the internal support structure to expand. After the expansion is completed, the movable steel sleeve is fixed by unscrewing the small pile driving iron rod 8 with a ring nut 12, thereby squeezing the precast pile body 1 outward to increase the pile side friction. After the precast pile body 1 is opened by the support iron rod, magnetic grout is injected into the space to drive water and expand cement grout to squeeze the precast pile body 1 to both sides.

[0060] Furthermore, multiple pre-reserved reinforcing bars 15 are provided on the side of the combined pile of the small pile 2, along with multiple pre-reserved reinforcing bar holes 16. The reinforcing bar holes 16 and the pre-reserved reinforcing bars 15 are staggered, and one end of the pre-reserved reinforcing bars 15 is above the ground after insertion. After the pile driving is completed and expansive concrete is poured, the pre-reserved reinforcing bars 15 can form a new pile structure with the concrete, increasing the overall integrity of the pile. Moreover, the combined insertion structure between the reinforcing bar holes 16 and the pre-reserved reinforcing bars 15 facilitates the assembly of the two, improving the ease of assembly.

[0061] Furthermore, the small pile 2 has multiple small blocks 17 that can move obliquely upward inside, forming a piston structure 25. The front part of the small block 17 is set in the shape of a spike, and the whole is cylindrical and conical. The small block 17 is physically attached to the inner wall of the pile, and a protrusion 18 is set at the bottom to prevent the small block 17 from slipping off. When the small block 17 is attached, it is ensured to be tightly attached, but not completely locked. When the expanding cement grout is added to the hollow structure, the small block 17 is squeezed upward due to the expansion and compression of the expanding cement grout. When the pile is retracted, because the small block 17 is obliquely upward, after vibration during pile extraction, when the expanding cement grout falls off, the piston structure 25 will also fall back to its original position under the action of vibration and gravity, thus making it easier to pull out the pile.

[0062] Furthermore, when the precast pile body 1 is used in an underwater environment, during the prefabrication of the lower pile body of the precast pile body 1, some pre-drilled holes 19 for concrete blocks are reserved in the precast pile body 1 for inserting magnetic concrete blocks 20. The aforementioned magnetic concrete blocks 20 facilitate the formation of corresponding magnetic attraction ends, thereby facilitating the attraction of magnetic mortar.

[0063] Furthermore, the magnetic concrete block 20 is made by adding some waste magnetizable slag steel chips to the concrete during the manufacturing process. After the concrete block is prefabricated, it is magnetized using a magnetizer and then placed into the reserved hole 19 of the concrete block on the lower side of the prefabricated pile body 1, so that the lower side of the prefabricated pile body 1 is magnetic. The magnetic concrete block 20 can be set on the inner or outer side of the pile according to different needs.

[0064] Furthermore, after the entire precast pile body 1 is inserted into the middle of the coral sand foundation, in the case of a water-rich environment, magnetic grout is first added into the gap formed between the precast pile body 1 and the internal support structure to fill the inside of the pile body. Since there is magnetic attraction at the bottom of the pile end, the injection of magnetic grout will play a role in driving water and draining water. Then, expansive concrete is added to expand the entire pile body as a whole.

[0065] Furthermore, after the precast pile body 1 is filled and pressurized, an independent pile foundation is adopted as needed, or the pile cap plate 24 is connected by a steel reinforcement structure 23 reserved at the top of the precast pile body 1 to ensure the stability of its pile cap structure.

[0066] Example 2:

[0067] A construction method for an expanded pile foundation structure on coral sand includes the following steps:

[0068] Step 1, Prepare materials: Prepare the steel pipes, steel bars and steel plates required for the preparation of the precast pile body 1, magnetic concrete block 20, pile cap 24, internal support structure and piston structure 25, and prepare the expansion cement grout and magnetic mortar required for subsequent pouring.

[0069] Step 2, formwork: Combine the specific structural forms of several small piles 2, magnetic concrete blocks 20 and piston structure 25, and form the skeleton structure of the precast pile body 1 after combination.

[0070] Step 3, Pile body casting of precast pile body 1: Pour concrete into the mold of small pile 2 in step 2 and compact the concrete. Note that during the casting process, reserve the cavity of piston structure 25 and magnetic concrete block 20. Use cover plates to seal the pipe openings in these two places to prevent blockage of the reserved holes.

[0071] Step 4: Assemble the magnetic concrete block 20, the precast pile body 1, the internal support structure and the piston structure 25.

[0072] Step 5.1: During the construction of pile holes in the coral sand foundation, after driving the piles, expandable cement grout is injected. A pile driver is used to construct the pile holes in the coral sand foundation. The pile body is shallowly inserted into the coral sand foundation. Then, the pile driving rod is inserted into the center space of the pile. The pile driving rod is initially pressurized with a rammer. At the same time, a hole-enlarging cover is added to the pile opening to prevent it from collapsing under pressure. Then, the entire precast pile body 1 is screwed downward into the coral sand foundation while being pressurized. The gaps in the pile foundation are initially filled with soil to make it compact.

[0073] Step 6.1: After the entire precast pile body 1 is inserted, replace it with a smaller diameter pile driving iron rod 8, and then insert the movable steel sleeve of the internal support structure. Use the pile driving machine to open it, leaving a part of the grouting space as the grouting reserved space. Then, grouting is carried out in the grouting reserved space.

[0074] Step 7.1, grouting at the bottom of the pile foundation: First, inject magnetic grout into the reserved grouting space using the grouting pipe. Due to the attraction of the magnetic concrete block 20 in the lower section, the magnetic grout first repairs and fills the gaps generated during pile driving, and at the same time drives out the water inside the precast pile body 1.

[0075] Step 8.1: After all the water in the grouting space has been drained and the magnetic grouting is completed, pour in expansive concrete, compact it, and form a bottom expansion zone. The expansion zone pushes the piston structure 25 to expand outward.

[0076] Step 9.1: After the expansive concrete has filled and solidified, remove the expansion cap, then backfill to fill the remaining gaps and compact it continuously.

[0077] Step 10.1: After the concrete has solidified and expanded, and cooled, connect and fix the foundation plate 24 to the reserved steel reinforcement structure 23.

[0078] Step 11.1 After the pile structure is completed, first remove the pile cap plate 24, and then reduce the size of the internal support structure;

[0079] Step 12.1 After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the internal expansive concrete to fall off, the piston structure to retract, and then the entire pile body is rotated and pulled out of the foundation by a pile extractor to complete the pile structure recovery.

[0080] Example 3:

[0081] A construction method for an expanded pile foundation structure on coral sand includes the following steps:

[0082] Step 1, Prepare materials: Prepare the steel pipes, steel bars and steel plates required for the preparation of the precast pile body 1, magnetic concrete block 20, pile cap 24, internal support structure and piston structure 25, and prepare the expansion cement grout and magnetic mortar required for subsequent pouring.

[0083] Step 2, formwork: Combine the specific structural forms of several small piles 2, magnetic concrete blocks 20 and piston structure 25, and form the skeleton structure of the precast pile body 1 after combination.

[0084] Step 3, Pile body casting of precast pile body 1: Pour concrete into the mold of small pile 2 in step 2 and compact the concrete. Note that during the casting process, reserve the cavity of piston structure 25 and magnetic concrete block 20. Use cover plates to seal the pipe openings in these two places to prevent blockage of the reserved holes.

[0085] Step 4: Assemble the magnetic concrete block 20, the precast pile body 1, the internal support structure and the piston structure 25.

[0086] Step 5.2: During the construction of the pile holes in the coral sand foundation, before driving the piles, expandable cement grout is injected. The pile hole is constructed in the coral sand foundation using a pile driver. The precast pile body 1 and the internal support structure are assembled first to ensure that the internal support structure is open. After assembly, expandable cement grout is poured directly into the central reserved system. After the expandable cement grout has initially set, a rammer is used to apply initial pressure to the end of the internal support structure. At the same time, a hole-enlarging cover is added to the pile opening to prevent it from collapsing under pressure. Then, the entire precast pile body 1 is screwed downward into the coral sand foundation while under pressure. The gaps in the pile foundation are then initially filled with soil to make it compact.

[0087] Step 6.2: After the concrete has solidified and expanded, let it cool, then connect and fix the foundation plate 24 to the reserved steel reinforcement structure 23.

[0088] Step 7.2: After the pile structure is completed, first remove the pile cap plate 24, and then reduce the size of the internal support structure;

[0089] Step 8.2: After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the internal expansive concrete to fall off, the piston structure to retract, and then the entire pile body is rotated and pulled out of the foundation by a pile extractor to complete the pile structure recovery.

Claims

1. An expanded pile foundation structure on coral sand, characterized in that: It includes a precast pile body (1), which is a precast pile composed of multiple separate small piles (2); the middle part of the precast pile body (1) is set as a hollow structure, which is used to insert the pile driving iron rod and internal support structure into the hollow structure when the precast pile body is driven into the coral sand; after the internal support structure is inserted into the hollow structure later, a reserved space will be formed between the outer wall of the internal support structure and the inner wall of the hollow structure. Grouting is performed inside the reserved space later; the cross section of the internal support structure inserted inside the precast pile body (1) is a concave polygon. The number of convex corners of the internal support structure is determined according to the actual number of parts after the precast pile body (1) is cut. The internal support structure adopts a high-strength steel structure. The convex corner of the internal support structure contacts the inner wall of the precast pile body (1). The middle of the internal support structure is a small pile driving iron rod (8). The small pile driving iron rod (8) is threaded on the outside. A movable steel sleeve with an inner diameter larger than the diameter of the small pile driving iron rod (8) is installed on the outside of the small pile driving iron rod (8). The movable steel sleeve is connected to the telescopic part (10) of the internal support structure through the support iron rod. Furthermore, a movable hinge (11) is used at the connection point; the internal support structure is used to provide internal support when the precast pile is driven into the ground. After the internal support structure is placed, the movable steel sleeve is pushed by the pile driver. The support iron rod on the side of the movable steel sleeve pushes the internal support structure to expand. After the expansion is completed, the movable steel sleeve is fixed by unscrewing the small pile driving iron rod (8) with a ring nut (12), thereby squeezing the precast pile body (1) outward to increase the pile side friction. After the precast pile body (1) is opened by the support iron rod, magnetic grout is injected into the reserved space to drive water and expand cement grout to squeeze the precast pile body (1) to both sides; the precast pile body (1) After internal filling and pressurization, independent pile foundations are adopted as needed, or the pile cap plate (24) is connected by a steel reinforcement structure (23) reserved at the top of the precast pile body (1) to ensure the stability of its pile cap structure; multiple reserved bars (15) are reserved on the side of the combined pile of the small pile (2), and multiple steel reinforcement holes (16) are reserved at the same time. The steel reinforcement holes (16) and the reserved bars (15) are staggered relative to each other, and one end of the reserved bars (15) is above the ground after insertion. After the pile is driven and the expansive concrete is poured, the reserved bars (15) can form a new pile structure with the concrete, increasing the integrity of the pile; multiple structures that can move obliquely upwards are set inside the small pile (2). Small block (17) forms piston structure (25). The front part of small block (17) is set in the shape of a spike, and the whole is cylindrical cone. Small block (17) is physically attached to the inner wall of the pile. A protrusion (18) is set at the bottom to prevent small block (17) from slipping. When small block (17) is attached, it is ensured to be tightly attached, but not completely locked. When the hollow structure is filled with expanding cement grout, the small block (17) is squeezed upward due to the expansion and squeezing effect of the expanding cement grout. When the pile is recycled, because small block (17) is tilted upward, after vibration is performed when the pile is pulled out, when the expanding cement grout falls off, the piston structure (25) will also fall back to its original position under the action of vibration and gravity, so that the pile can be pulled out more easily.

2. The expanded pile foundation structure on coral sand according to claim 1, characterized in that: The top of the precast pile body (1) is made into a downward conical structure. The diameter of the selected pile driving iron rod is larger than the inner diameter of the hollow structure of the precast pile body (1), so that the pile driving iron rod has a preliminary squeezing force in all directions while driving the pile downward.

3. The expanded pile foundation structure on coral sand according to claim 1, characterized in that: The precast pile body (1) has been cut into multiple parts before insertion. The cut parts are divided into the required number of parts according to the specific engineering needs. The outer surface of the precast pile body (1) is provided with a spiral structure (7). The spiral structure (7) is used to enhance the friction of the pile side. At the same time, the spiral pile pressing method is adopted during pile pressing, so that the entire pile body is like a screw and the pile body is screwed into the coral sand foundation.

4. The expanded pile foundation structure on coral sand according to claim 3, characterized in that: When the precast pile body (1) is used in an underwater environment, some concrete block reserved holes (19) are reserved in the precast pile body (1) during the precasting of the lower pile body of the precast pile body (1) for inserting magnetic concrete blocks (20).

5. The expanded pile foundation structure on coral sand according to claim 4, characterized in that: The magnetic concrete block (20) is made by adding some waste magnetizable slag steel chips to the concrete during the manufacturing process. After the concrete block is prefabricated, it is magnetized by a magnetizer and then placed into the pre-reserved hole (19) of the concrete block under the precast pile body (1) so that the lower side of the precast pile body (1) is magnetic. The magnetic concrete block (20) can be set inside or outside the pile according to different needs.

6. The expanded pile foundation structure on coral sand according to claim 4, characterized in that: After the entire precast pile body (1) is inserted into the middle of the coral sand foundation, in the case of a water-rich environment, magnetic grout is first added into the gap formed between the precast pile body (1) and the internal support structure to fill the inside of the pile body. Since there is magnetic attraction at the bottom of the pile end, the injection of magnetic grout will play a role in driving water and draining water. Then, expansive concrete is added to expand the entire pile body as a whole.

7. A construction method for an expanded pile foundation structure on coral sand as described in any one of claims 4-6, characterized in that, Includes the following steps: Step 1, Prepare materials: Prepare steel pipes, steel bars and steel plates required for the preparation of the precast pile body (1), magnetic concrete block (20), pile cap plate (24), internal support structure and piston structure (25), and prepare the expansion cement slurry and magnetic mortar required for subsequent pouring; Step 2, formwork: Combine several small piles (2), magnetic concrete blocks (20) and piston structure (25) into a specific structural form, and form the skeleton structure of the precast pile body (1) after combination; Step 3, Pile body pouring of precast pile body (1): Pour concrete into the mold of small pile (2) in step 2 and compact the concrete. Note that during the pouring process, reserve the cavity of piston structure (25) and magnetic concrete block (20). Use cover plates to seal the pipe openings in these two places to prevent blockage of the reserved holes. Step 4: Assemble the magnetic concrete block (20), the precast pile body (1), the internal support structure and the piston structure (25); Method 1, Step 5.1, When constructing the pile hole of the coral sand foundation, after driving the pile, inject the expansion cement grout and use the pile driving machine to construct the pile hole of the coral sand foundation. Since the pile body is shallowly inserted into the coral sand foundation, the pile driving iron rod is then inserted into the center space of the pile. The pile driving iron rod is initially pressurized with a rammer. At the same time, a hole-enlarging cover is added to the pile opening to prevent it from collapsing under pressure. Then, the entire precast pile body (1) is screwed downward into the coral sand foundation while being pressurized. The gap of the pile foundation is initially filled with soil and compacted. Step 6.1: After the entire precast pile body (1) is inserted, replace it with a smaller diameter pile driving iron rod (8), then insert the movable steel sleeve of the internal support structure, and use the pile driving machine to open it, leaving a part of the grouting space as the grouting reserved space, and then grouting in the grouting reserved space; Step 7.1, grouting at the bottom of the pile foundation: first inject magnetic grout into the reserved space for grouting using the grouting pipe. Due to the attraction of the magnetic concrete block (20) in the lower section, the magnetic grout first repairs and fills the gaps generated during pile driving, and at the same time drives out the water inside the precast pile body (1). Step 8.1: After all the water in the grouting space has been drained and the magnetic grouting is completed, pour in the expansive concrete and compact it to form a bottom expansion zone. The expansion zone pushes the piston structure (25) to expand outward. Step 9.1: After the expansive concrete has filled and solidified, remove the expansion cap, then backfill to fill the remaining gaps and compact it continuously. Step 10.1: After the concrete has solidified and expanded, let it cool, then connect and fix the foundation plate (24) to the reserved steel reinforcement structure (23); Step 11.1 After the pile structure is used, first remove the pile cap plate (24), and then reduce the size of the internal support structure; Step 12.1 After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the expansive concrete inside to fall off and the piston structure to retract. Then, the entire pile body is rotated and pulled out of the foundation with a pile extractor to complete the pile structure recovery. Method 2, Step 5.2, When constructing the pile hole of the coral sand foundation, inject expansive cement grout before driving the pile, and use a pile driver to construct the pile hole of the coral sand foundation. First, assemble the precast pile body (1) with the internal support structure, and determine the internal support structure to be opened. After the assembly is completed, pour the expansive cement grout directly into the central reserved system. After the expansive cement grout has initially set, use a rammer to initially pressurize the end of the internal support structure. At the same time, cover the pile opening with an enlarged hole cover to prevent it from collapsing under pressure. Then, while pressurizing, screw the entire precast pile body (1) downward into the coral sand foundation. Then, use soil to initially fill the gap of the pile foundation and compact it. Step 6.2: After the concrete has solidified and expanded, let it cool, then connect and fix the foundation plate (24) to the reserved steel reinforcement structure (23); Step 7.2: After the pile structure is used, first remove the pile cap plate (24), and then reduce the size of the internal support structure; Step 8.2: After the internal support structure retracts, the pile body is shaken with a vibratory machine to cause the internal expansion concrete to fall off, the piston structure to retract, and then the entire pile body is rotated and pulled out of the foundation by a pile extractor to complete the pile structure recovery.

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