A screw pile piling system and method and its expanded head screw pile foundation structure

Abstract

The application discloses a screw pile forming system and method and an expanded-head screw pile foundation structure. The screw pile forming system comprises a screw pile, a vacuum pump and a water tank. The expanded-head screw pile structure comprises a screw pile, reinforcing steel bars, a grouting body and a riprap expanded head wrapped by grouting. The screw pile is modified from a traditional screw pile foundation by a pile tip structure and a pile top structure to adapt to hole cleaning and grouting of a riprap pore channel; the reinforcing steel bars are arranged at a central position of the pipe pile and the lower ends of the reinforcing steel bars are embedded into a riprap stratum; and the riprap expanded head is wrapped by the pipe pile bottom end through pressure grouting and diffused to pores of surrounding riprap to be connected with the riprap stratum to form an expanded head whole. The application can realize the application of the screw pile foundation in the riprap stratum, realize the bearing effect of the screw pile bottom expanded head through the built-in reinforcing steel bars and grouting of the screw pile, greatly improve the bearing capacity of the screw pile, and has the advantages of convenient implementation, short construction period and low cost without the intervention of large-scale machinery in the construction process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pile foundation, in particular to a screw pile forming method and an expanded-head screw pile structure. BACKGROUND

[0002] The screw pile has a small pile type, and its engineering installation process is like screwing a bolt, which is simple and fast. Compared with the ordinary pile foundation, the screw pile has significant advantages, including fast installation speed, short construction period, small damage to vegetation and ecological environment during construction process, small influence on the surrounding environment, strong adaptability to different climate and geological conditions, and the like. Therefore, the screw pile gradually appears in more and more soft soil engineering projects, and is applied in the fields of photovoltaic power generation engineering, wind power buried power transmission engineering, artificial island lighthouse, and the like, and the application is increasing year by year.

[0003] For a large number of soft soil environments along the river and the coast, the engineering often uses riprap to squeeze silt to form a riprap foundation, and fills the soil on the riprap foundation to form an artificial foundation. In such a site, there are three challenges in screw pile construction: 1) the screw pile cannot be penetrated into the riprap stratum, the thickness of the artificial fill soil layer is small, and the direct screw pile construction cannot meet the requirement of bearing capacity; 2) the riprap stratum is mainly composed of block stones, has good pore connectivity, and has extremely strong water permeability, and the foundation will further settle under the condition of strong underground water power; and 3) the bearing capacity of the construction site is often low, and large construction equipment is not allowed to enter, which puts forward higher requirements on the construction process of the screw pile. For the screw pile under such special foundation conditions, how to form the pile and ensure sufficient bearing capacity is the key to design and construction. SUMMARY

[0004] In view of the problem that the screw pile in the prior art is difficult to adapt to the special foundation containing the riprap stratum, the present application aims to provide a screw pile forming method and an expanded-head screw pile structure.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] A screw pile forming system, comprising a new screw pile for pile forming, and a power supply, a negative pressure control system, a water source, a grouting system, and a reinforcing steel bar arranged on the ground, wherein:

[0007] The new spiral pile comprises a pipe pile 1, a spiral piece 2 and a mud baffle 25; the spiral piece 2 is fixedly arranged at the bottom end of the pipe pile 1; the mud baffle 25 is arranged at the pile tip of the pipe pile 1 in a weak connection mode, so that the soil does not enter the pipe pile 1 during the rotation and penetration process of the spiral pile. The structure of the pile tip of the pipe pile 1: a pile tip reinforcing ring 23, a pile tip plug 6, a plug air pipe 7, a mud discharge pipe 21 with a pipe plug 27 are arranged at the bottom of the pipe pile 1; the pile tip reinforcing ring 23 is arranged near the pile tip of the pipe pile 1, and is used for improving the rigidity of the pile tip and providing installation limiting for the pile tip plug 6; the plug air pipe 7 penetrates through the pile tip plug 6, and a traction rope 24 is further arranged on the pile tip plug 6; the mud discharge pipe 21 is arranged at the center of the bottom of the pipe pile 1; the structure of the pile top of the pipe pile 1: a thread is arranged at the top inside of the pipe pile 1, and is used for being connected with a conventional grouting pipe to complete pressure grouting; a suction cap 8 is sleeved at the top of the pipe pile 1; two through holes are formed in the suction cap 8, and are used for connecting the plug air pipe 7 and a cap air pipe 9 respectively.

[0008] The water source and the grouting system are conventional technologies in the field, and the water source can be provided with a water tank 15.

[0009] The negative pressure control system comprises a vacuum pump 10, a valve and other conventional devices in the field, so as to support the hole cleaning and grouting mechanism of the riprap pore channel.

[0010] Further, the pile tip at the bottom end of the spiral pile is an inclined hole, and the mud baffle 25 is an oval plate which can cover the inclined hole at the bottom end of the spiral pile.

[0011] Further, the pipe pile 1, the spiral piece 2 and the mud baffle 25 are all made of steel material.

[0012] Further, the pipe pile 1 and the mud baffle 25 are weakly connected in a uniform electric welding mode.

[0013] Further, the sealing gasket 22 is arranged on the pile tip reinforcing ring 23.

[0014] Further, the sealing ring 32 is further arranged between the suction cap 8 and the top of the pipe pile 1.

[0015] A pile forming process method realized by a spiral pile forming system, and a mud and sand cleaning process is as follows:

[0016] Firstly, the pile tip plug 6 with the pipe plug 27 is placed in the pipe pile 1, the pipe pile 1 is sealed by the cap 8, and all pipelines are in a closed state, so that the space below the pile tip plug 6 is a closed space;

[0017] Then, the plug air pipe 7 is connected with the vacuum pump 10, the power of the vacuum pump 10 is turned on, and the negative pressure effect is formed in the space below the pile tip plug 6, so that the pipe pile 1 is sunk to the position of the pile tip reinforcing ring 23;

[0018] Then, stop the vacuum pump 10, and connect the plug air pipe 7 and the cap air pipe 9 to the water tank 15 and the vacuum pump 10 respectively, open the cap air pipe valve, and turn on the power of the vacuum pump 10. The pipe plug 27 will be automatically pulled out under the negative pressure, and a vacuum is formed in the stones around the pile tip. Under the drive of the vacuum pressure, the water around the pile 1 converges into the pile 1 and is sucked into the pile 1. At the same time of the vacuum suction, the plug air pipe 7 valve is opened intermittently for water injection, which produces a flushing effect on the soil and also produces a pulsating pressure effect in the suction process, which helps to destroy the silt structure between the stones and thus be carried away by the water flow. The silt around the pile tip of the screw pile is sucked out of the silt discharge pipe 21 and collected around the silt discharge pipe 21; stop the vacuum pump 10, open the cap 8, and clean the collected silt 26 around the silt discharge pipe 21; repeat the above steps multiple times until the concentration of the silt discharged by the suction reaches the required level.

[0019] Finally, pull the traction rope 24 and remove the pile tip plug 6.

[0020] An expanded-head screw pile foundation structure obtained by a screw pile piling system construction process, comprising a screw pile, a reinforcing steel bar, a grouting body, and a riprap expanded head wrapped by grouting.

[0021] The screw pile comprises a hollow pipe pile 1 and a spiral blade, a pile tip structure, and a pile top structure fixedly installed at the end of the pile body; the pile tip structure comprises a pile tip reinforcing ring 23 and a mud baffle 25;

[0022] The pile top structure refers to a thread arranged on the inside of the top of the pipe pile 1, which can be connected with a conventional grouting pipe;

[0023] The reinforcing steel bar is arranged at the center of the pipe pile 1, and the lower end of the reinforcing steel bar is embedded in the riprap stratum;

[0024] The grouting body is pressure grouting and fills the pipe pile 1;

[0025] The riprap expanded head is an expanded head formed by pressure grouting to wrap the bottom end (including the spiral blade) of the pipe pile 1 and diffuse to the pores of the surrounding riprap, which is connected with the riprap stratum as a whole; the riprap stratum is mainly composed of stones, has good pore connectivity, and has extremely strong water permeability.

[0026] Preferably, the mud baffle 25 at the bottom of the screw pile is an oval plate that can cover the inclined hole at the bottom end of the screw pile, and the mud baffle 25 is weakly connected with the bottom of the pipe pile 1 of the screw pile.

[0027] Preferably, the sum of the cross-sectional areas of the reinforcing steel bars is 0.5-2 times the strength equivalent cross-sectional area of the hollow pipe pile 1.

[0028] Preferably, the pressure grouting has an initial setting time of no less than 5 minutes.

[0029] Preferably, the weak connection has a connection strength capable of keeping the mudguard 25 connected with the bottom of the pipe pile 1 of the screw pile together, and the soil does not enter the pile body during the screw pile penetration process, but directly pokes the mudguard 25 to form a pressure grouting channel when the screw pile is installed in place.

[0030] With the technical scheme, the application has the following advantages:

[0031] Due to the arrangement of the screw pile, the reinforcing steel bar, the grouting body, the riprap stratum, and the steel bar embedded in the riprap stratum, when in use, the screw pile is rotated and penetrated until the riprap stratum, and the riprap stratum is continuously grouted, so that the bottom end of the pile body (including the screw blade) is wrapped by the grouting material, and a stable connection with the riprap stratum full of grouting material is achieved, forming an expanded head screw pile foundation including the grouting riprap stratum. The foundation is equivalent to a pile foundation with an expanded bottom end, and the volume of the expanded pile head is large, having good bearing performance. Compared with the traditional screw pile foundation, the expanded head pile foundation and the method thereof of the application do not involve the excavation or heavy mechanical drilling of the riprap stratum, and fully utilize the characteristics of the scattered particles of the riprap stratum for in-situ grouting construction, which greatly reduces the disturbance to the surrounding soft soil, and has the characteristics of fast construction speed, small requirement for manpower and material resources, and small post-construction settlement. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Schematic diagram of the mudguard at the tip of the screw pile;

[0033] Figure 2 Schematic diagram of the tip structure of the screw pile and the tip plug;

[0034] Figure 3 Schematic diagram of the top structure of the screw pile and the cap sealing principle;

[0035] Figure 4 Schematic diagram of the principle of cleaning the pore silt of the riprap stratum;

[0036] Figure 5 Schematic diagram of the structure of the expanded head screw pile foundation.

[0037] In the figure: 1-pipe pile, 2-screw blade, 3-riprap stratum, 4-block stone void silt, 5-drilling hole, 6-tip plug, 7-plug air pipe, 8-suction cap, 9-cap air pipe, 10-vacuum pump, 11-filling layer, 12-natural stratum, 13-grouting body, 14-reinforcing steel bar, 15-water tank

[0038] 21 - mud pipe, 22 - gasket, 23 - tip reinforcement ring, 24 - traction rope, 25 - fender, 26 - collecting silt, 27 - pipe plug, 31 - internal thread, 32 - sealing ring. DETAILED DESCRIPTION

[0039] The following will be described in detail Figures 1-5 The specific embodiments are further described in detail.

[0040] First part

[0041] Figure 1 As shown, the spiral pile of the present application includes a pipe pile 1, a spiral piece 2 and a fender 25, all of which are made of steel material, and the pipe pile 1 and the fender 25 are weakly connected by uniform electric welding.

[0042] Figure 2 , Figure 3 As shown, the further modified spiral pile of the present application is shown in the figure, which shows the key part of the tip structure and the tip plug 6 of the spiral pile, forming a new spiral pile containing a weakly connected fender 25. The new spiral pile is modified from the tip structure and the top structure of the traditional spiral pile to adapt to the hole cleaning and grouting of the riprap pore channel. By setting the fender 25 at the tip, the soil does not enter the pipe pile 1 during the rotation and penetration of the spiral pile; by setting the tip reinforcement ring 23 at the tip, the rigidity of the tip is improved to avoid bending and twisting damage during penetration, and at the same time, the tip plug 6 for hole cleaning of the riprap pore channel is provided with installation limiting; by setting the thread on the inside of the top of the pipe pile 1, it can be connected with the conventional grouting pipe to complete the pressure grouting.

[0043] The working mechanism of the modified spiral pile is:

[0044] When the pipe plug 27 seals the mud pipe 21, and a negative pressure is applied from the plug air pipe 7, the tip plug 6 will inevitably slide to the bottom of the pipe pile 1 until it is limited and stuck at the position of the tip reinforcement ring 23. Conversely, the space above the tip plug 6 of the pipe pile 1 is vacuumed, and the plug air pipe 7 is connected with the atmosphere, then the pipe plug 27 will be pushed away from the mud pipe 21 under the action of atmospheric pressure.

[0045] Second part

[0046] Figure 4 The principle diagram of cleaning silt in the pore of riprap stratum (i.e. the system diagram of the present application) is shown in the figure, which analyzes the silt cleaning process in combination with Figure 4

[0047] First, place the tip plug 6 with the tightly plugged pipe plug 27 in the pipe pile 1, seal the pipe pile 1 with the cap 8, and all pipelines are in a closed state, at this time the space below the tip plug 6 is a closed space;

[0048] ​Next, connect the plug air pipe 7 to the vacuum pump 10, turn on the power of the vacuum pump 10, and form a negative pressure in the space below the pile tip plug 6, so as to sink to the position of the pile tip reinforcing ring 23;

[0049] Then, stop the vacuum pump 10, and then connect the plug air pipe 7 and the cap air pipe 9 to the water tank 15 and the vacuum pump 10 respectively, open the air pipe valve, and turn on the power of the vacuum pump 10. The pipe plug 27 will be automatically pulled out under the negative pressure, and a vacuum will be formed in the stones around the pile tip. Under the drive of the vacuum pressure, the water around the pipe pile 1 converges into the pipe pile 1 and is sucked into the pipe pile 1. At the same time of the vacuum suction, the plug air pipe 7 is intermittently opened for water injection, which produces a flushing effect on the soil and also produces a pulsating pressure effect in the suction process, which helps to destroy the structure of the silt between the stones and thus be carried away by the water flow. The silt around the spiral pile tip will be sucked out of the silt discharge pipe 21 and collected around the silt discharge pipe 21; stop the vacuum pump 10, open the cap 8, and clean the collected silt 26 around the silt discharge pipe 21; repeat the above steps multiple times until the concentration of the silt discharged by the suction reaches the required level. Finally, pull the traction rope 24 to remove the pile tip plug 6.

[0050] Third part of the embodiment

[0051] Artificial fill layer 11.

[0052] Riprapping stratum 3, mainly composed of stones, has good pore connectivity and extremely strong water permeability, but a certain amount of silt will be filled between the stones, affecting the grouting effect and requiring hole cleaning. Above it is the fill layer 11.

[0053] Natural stratum 12. Above it is the riprapping stratum 3.

[0054] After measurement and positioning, the spiral pile is rotated and penetrated into the artificial fill layer 11, and the spiral pile has a pile body diameter d of 114 mm, a spiral blade diameter D of 406 mm, and a length of 4.5 m. The thickness of the spiral pile wall is 7.8 mm, and the thickness of the spiral blade is 9.5 mm.

[0055] The main construction procedures of the enlarged-head spiral pile include:

[0056] S1, selecting the new spiral pile with a weakly connected mud baffle 25 designed in the application; and arranging the riprapping stratum pore silt cleaning system designed in the application on site;

[0057] S2, rotating and penetrating the new spiral pile until it enters the riprapping stratum and cannot continue to penetrate, and the mud baffle 25 is poked open by the reinforcing steel bar 14;

[0058] S3, placing the pile tip plug 6 tightly plugged with the pipe plug 27 into the pipe pile 1, sealing the pipe pile 1 with the cap 8, and closing all pipelines;

[0059] S4, connect the plug air pipe 7 to the vacuum pump 10, turn on the power of the vacuum pump 10, the plug tip 6 sinks to the bottom of the pipe pile 1 due to the negative pressure;

[0060] S5, stop the vacuum pump 10, then connect the plug air pipe 7 and the cap air pipe 9 to the water tank 15 and the vacuum pump 10 respectively, open the cap air pipe valve, turn on the power of the vacuum pump 10, the pipe plug 27 will be automatically pulled out under negative pressure;

[0061] S6, while vacuum pumping, intermittently open the plug air pipe 7 valve for water injection, the silt around the tip of the screw pile will be pumped out of the mud discharge pipe 21 and collected around the mud discharge pipe 21;

[0062] S7, stop the vacuum pump 10, open the cap 8, and clean the collected silt 26 around the mud discharge pipe 21;

[0063] S8, repeat steps S6 and S7 multiple times until the concentration of the pumped-out silt meets the requirements;

[0064] S9, pull the traction rope 24 to remove the plug tip 6;

[0065] S10, embed the reinforcing steel 14 into the riprap stratum;

[0066] S11, sleeve the grouting device, pressure water the screw pile, gradually increase the pressure from small to large, flush and dredge the grouting channel;

[0067] S12, stop water injection, then pressure grout the screw pile until it is full.

[0068] Preferably, in S2, if the mud guard 25 is difficult to pierce, the rotating screw pile reserves a space for the movement of the mud guard 25, or in S1, the connection strength between the mud guard 25 and the bottom of the pipe pile 1 is reduced.

[0069] Preferably, in S4, if the lower end of the reinforcing steel is difficult to embed into the riprap stratum, drill a hole in the riprap stratum from the inside of the pipe pile 1, then insert the reinforcing steel into the drilled hole, and the embedding depth of the reinforcing steel into the riprap stratum is not less than 20 times the diameter of the reinforcing steel.

[0070] Preferably, in S6, if the screw pile is blocked or difficult to penetrate during pressure grouting, the fluidity and initial setting time of the grouting material are increased.

[0071] Fourth part

[0072] After the construction of the embodiment is completed, the final result is Figure 5 Enlarged head screw pile foundation structure:

[0073] An enlarged head screw pile foundation comprises a new screw pile, reinforcing steel bars, grouting body and riprap enlarged head.

[0074] The new screw pile comprises a hollow pipe pile 1 and a screw blade, a pile tip structure and a pile top structure fixedly installed at the end of the pile body; the pile tip structure comprises a pile tip reinforcing ring 23 and a mud baffle 25;

[0075] The pile top structure refers to arranging a thread inside the top of the pipe pile 1, which can be connected with a conventional grouting pipe;

[0076] The reinforcing steel bars are arranged at the center of the pipe pile 1, and the lower end of the reinforcing steel bars is embedded into the riprap stratum;

[0077] The grouting body is pressure grouting and fills the pipe pile 1;

[0078] The riprap enlarged head is an enlarged head formed by pressure grouting to wrap the bottom end (including the screw blade) of the pipe pile 1 and diffuse to the pores of the surrounding riprap, and is connected with the riprap stratum as a whole; and

[0079] The riprap stratum mainly comprises block stones, has good pore connectivity and extremely strong water permeability.

[0080] Preferably, the mud baffle 25 at the bottom of the screw pile is an elliptical plate, which can exactly cover the inclined hole at the bottom end of the screw pile, and the mud baffle 25 is weakly connected with the bottom of the pipe pile 1 of the screw pile.

[0081] Preferably, the sum of the cross-sectional areas of the reinforcing steel bars is 0.5-2 times the strength equivalent cross-sectional area of the hollow pipe pile 1.

[0082] Preferably, the pressure grouting has an initial setting time of not less than 5 minutes.

[0083] Preferably, the weak connection has a connection strength that can keep the mud baffle 25 and the bottom of the pipe pile 1 of the screw pile connected together, so that the soil cannot enter the inside of the pile body during the penetration of the screw pile, but can directly punch the mud baffle 25 to form a pressure grouting channel when the screw pile is installed in place.

[0084] The overall structural bearing capacity of the screw pile in the embodiment is realized by grouting to fix the screw pile-riprap together, which is equivalent to adding an enlarged head with a much larger size at the bottom of the screw pile, thereby greatly increasing the range of the riprap stratum bearing the screw pile and greatly reducing the settlement of the enlarged head screw pile.

[0085] The embodiments of the present application are all the preferred embodiments of the present application, and do not limit the protection scope of the present application, so that equivalent changes made according to the structure, shape and principle of the present application should be covered in the protection scope of the present application.

Claims

1. A screw pile piling system, characterized in that, It comprises a spiral pile for piling, and a power supply, a negative pressure control system, a water source, a grouting system and reinforcing steel arranged on the ground. The spiral pile comprises a pipe pile (1), a spiral blade (2) and a mud baffle (25); the spiral blade (2) is fixedly arranged at the bottom end of the pipe pile (1); the mud baffle (25) is arranged at the pile tip of the pipe pile (1) in a weakly connected manner, so that soil does not enter the pipe pile (1) during the rotation and penetration of the spiral pile; the structure of the pile tip of the pipe pile (1) comprises a pile tip reinforcing ring (23), a pile tip plug (6), a plug air pipe (7), and a mud discharge pipe (21) provided with a pipe plug (27); the pile tip reinforcing ring (23) is arranged near the pile tip of the pipe pile (1) and is used for improving the rigidity of the pile tip and providing installation limiting for the pile tip plug (6); the plug air pipe (7) penetrates through the pile tip plug (6), and the pile tip plug (6) is further provided with a traction rope (24); the mud discharge pipe (21) is arranged at the center of the bottom of the pipe pile (1); the structure of the pile top of the pipe pile (1) comprises threads arranged at the inner side of the top of the pipe pile (1) and used for being connected with a conventional grouting pipe to complete pressure grouting; the top of the pipe pile (1) is sleeved with a suction cap (8); the suction cap (8) is provided with two through holes used for being connected with the plug air pipe (7) and a cap air pipe (9) respectively. The water source is provided with a water tank (15). The negative pressure control system comprises a vacuum pump (10) and valves, so as to support hole cleaning and grouting mechanism of the riprapping pore channel.

2. A screw pile piling system as claimed in claim 1, wherein, The pile tip at the bottom end of the spiral pile is an inclined aperture, and the mud baffle (25) is an oval plate capable of covering the inclined aperture at the bottom end of the spiral pile.

3. A screw pile piling system as claimed in claim 1, wherein, The pipe pile (1), the spiral blade (2) and the mud baffle (25) are all made of steel material.

4. A screw pile piling system as claimed in claim 1, wherein, The pipe pile (1) and the mud baffle (25) are weakly connected in a uniform electric welding manner.

5. A screw pile piling system as claimed in claim 1, wherein, The pile tip reinforcing ring (23) is provided with a sealing gasket (22), and the suction cap (8) and the top of the pipe pile (1) are provided with a sealing ring (32).

6. A method of piling by the screw pile forming system as claimed in claim 1, characterized in that, The process of cleaning the silt is as follows: Firstly, the pile tip plug (6) tightly plugged is arranged in the pipe pile (1), and the pipe pile (1) is sealed by the cap (8); all pipelines are closed; at this time, the space below the pile tip plug (6) is a closed space; Then, the plug air pipe (7) is connected with the vacuum pump (10); the power supply of the vacuum pump (10) is turned on; the space below the pile tip plug (6) is formed with a negative pressure effect; and the pipe pile (1) is sunk to the position of the pile tip reinforcing ring (23); Then, the power supply of the vacuum pump (10) is turned off; the plug air pipe (7) and the cap air pipe (9) are connected with the water tank (15) and the vacuum pump (10) respectively; the valve of the cap air pipe is opened; the power supply of the vacuum pump (10) is turned on; the pipe plug (27) is automatically pulled out under the negative pressure; and a vacuum is formed around the pile tip; under the driving of the vacuum pressure, the water around is gathered into the pipe pile (1) and is sucked into the pipe pile (1); at the same time of the vacuum suction, the valve of the plug air pipe (7) is intermittently opened to inject water, so as to produce a flushing effect on the soil and a pulsating pressure effect in the suction process, which is helpful to destroy the silt structure between the blocks and thus the silt is taken away by the water flow; The silt around the screw pile tip is sucked out of the silt discharge pipe (21) and collected around the silt discharge pipe (21); stop the vacuum pump (10), open the cap (8), and clean the collected silt (26) around the silt discharge pipe (21); repeat the above steps several times until the concentration of the discharged silt reaches the required concentration; Finally, pull the traction rope (24) to remove the pile tip plug (6).

7. An enlarged head screw pile foundation structure obtained from the piling process method as claimed in claim 6, characterized by, The screw pile, the reinforcing steel bar, the grouting body, and the riprap enlarged head wrapped by the grouting body are included. The screw pile includes a hollow pipe pile (1) and a screw blade, a pile tip structure, and a pile top structure fixedly installed at the end of the pile body; the pile tip structure includes a pile tip reinforcing ring (23) and a mud baffle (25); The pile top structure refers to a thread arranged on the inner side of the top of the pipe pile (1) and connectable with a conventional grouting pipe; The reinforcing steel bar is arranged at the center of the pipe pile (1), and the lower end of the reinforcing steel bar is embedded in the riprap stratum; The grouting body is a pressure grouting body and fills the pipe pile (1); The riprap enlarged head is an enlarged head formed by pressure grouting to wrap the pipe pile (1) containing the screw blade at the bottom end and diffuse to the pores of the surrounding riprap body and connect with the riprap stratum; the riprap stratum mainly includes block stones, has good pore connectivity, and has extremely strong water permeability.

8. An enlarged footing pile foundation structure as claimed in claim 7 wherein, The mud baffle (25) at the bottom of the screw pile is an oval plate that can cover the inclined hole at the bottom end of the screw pile, and the mud baffle (25) is weakly connected with the bottom of the pipe pile (1) of the screw pile; the weak connection has a connection strength that can keep the mud baffle (25) and the bottom of the pipe pile (1) of the screw pile connected together, and the soil body cannot enter the inside of the pile body during the screw pile penetration process, but the mud baffle (25) is directly punched to form a pressure grouting channel when the screw pile is installed in place.

9. An enlarged footing pile foundation structure as claimed in claim 7 wherein, The sum of the cross-sectional areas of the reinforcing steel bars is 0.5-2 times the equivalent cross-sectional area of the strength of the hollow pipe pile.

10. The expanded footing pile foundation structure of claim 7, wherein, The pressure grouting has an initial setting time of not less than 5 minutes.

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