Miniature steel pipe pile for foundation reinforcement in limited operation space and construction method

Abstract

The invention discloses a limited operation space foundation reinforcement miniature steel pipe pile and a construction method. Relates to the technical field of steel pipe piles and comprises a steel pipe pile body, the steel pipe pile body is provided with a plurality of sections which are sequentially connected, the bottom of the steel pipe pile body is machined into a circular truncated cone shape through a necking technology, the pipe wall of each section of steel pipe pile body is provided with a plum blossom-shaped hole, and the joint of each section of steel pipe pile body is provided with a spiral connector. Every two adjacent sections of steel pipe pile bodies are connected through a spiral connector; and the anti-pulling structure ring comprises a circular ring sleeve, springs and three steel sheets, the steel pipe pile body is sleeved with the circular ring sleeve, and the three steel sheets are connected through the springs and evenly distributed on the side, away from the steel pipe pile body, of the circular ring sleeve in the circumferential direction. The circular ring sleeve, the three springs and the three steel sheets are arranged, the three steel sheets face upwards, large friction is generated between the steel sheets and rock soil on the pile side, the steel sheets are opened back to the pile, resistance is increased, the pile body anti-pulling structure ring is beneficial to fixing and centering of the pile, and the anti-pulling and anti-compression performance of the pile is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe piles, and more particularly to a limited working space foundation reinforcement micro steel pipe pile and a construction method. Background Art

[0002] In recent years, due to various reasons, the number of projects that require reconstruction and expansion of existing power stations, power plants, industrial plants, etc. has increased day by day. Most of them need to retain the original functions and carry out reconstruction and expansion at the same time as operation. Especially for high-voltage power stations, the on-site working conditions are very restrictive to the construction of foundation. Conventional foundation construction has large mechanical equipment and large operating vibration, which poses a great threat to the operation of substation electrical equipment. Grouting micro steel pipe piles are a new type of micro piles that use geological drilling rigs to drill holes with a diameter of 15cm to 40cm, and then set steel pipes with micropores pre-processed on the pipe wall in the holes, and use a certain pressure to inject cement slurry or cement mortar to consolidate into piles. Micro steel pipe piles have the characteristics of small construction equipment, fast construction speed, reliable construction quality, small impact on the environment, and easy adjustment of pile length and pile cross-section size; in view of this, grouting micro steel pipe piles are introduced as a new type of foundation.

[0003] The document with application number 201710645886.9 discloses a post-grouting construction method for small-diameter micro static pressure steel pipe piles. The specific processes include processing and manufacturing small-diameter steel pipe piles, pile pressing, cleaning the inner wall of the steel pipe, gravity grouting, pressure grouting, static curing and pouring concrete. The document with application number 201911058954.7 discloses a grouting micro steel pipe pile and pile foundation and a construction method for small and medium-sized span bridges. The specific processes include: geological survey, fixed-point drilling, hole cleaning, processing and manufacturing micro steel pipes, welding centering frames, lowering micro steel pipes and grouting pipes, cleaning holes twice, grouting twice, setting a cushion layer, setting connecting steel bars between the pile and the pedestal, and obtaining a grouting micro steel pipe pile foundation; the document with application number 202410189977.6 discloses a micro steel pipe pile for slope reinforcement and a construction method thereof, which is designed by designing a lower tube body with a closed pointed head, an upper tube body with a grouting pipe fitting and a cylindrical connecting piece connecting the lower tube body and the upper tube body, a flange ring, a side frame, and a support frame sliding structure are arranged on the pile side, and the lower tube body and the upper tube body are installed together through a cylindrical connecting piece to form a micro steel pipe pile as a whole. However, in actual projects, there are limited spaces for the side friction of piles to play a role, insufficient tensile or compressive resistance of piles, weak bearing capacity at the pile ends, especially when the sediment is too thick.

[0004] Therefore, how to provide a fast, effective, and limited working space foundation reinforcement micro steel pipe pile and construction method with pull-out bearing capacity and compressive bearing capacity is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a micro steel pipe pile for reinforcing the foundation of a limited working space and a construction method, which aims to solve one of the problems in the above-mentioned background technology, and is fast, effective and has pull-out bearing capacity and compressive bearing capacity.

[0006] In order to achieve the above-mentioned object, on the one hand, the present invention provides a micro steel pipe pile for reinforcing a foundation in a limited working space, comprising:

[0007] A steel pipe pile body, wherein the steel pipe pile body is provided with multiple sections connected in sequence, the bottom of each section of the steel pipe pile body is processed into a truncated cone shape by a necking process, the pipe wall of each section of the steel pipe pile body is opened in a plum blossom form, a spiral joint is provided at the connection of each section of the steel pipe pile body, and two adjacent sections of the steel pipe pile body are connected by the spiral joint;

[0008] The pull-out resistant structural ring comprises a circular ring sleeve, a spring and a steel sheet. The circular ring sleeve is sleeved on the steel pipe pile body. Three steel sheets are arranged. The bottoms of the three steel sheets are hinged to the side of the circular ring sleeve away from the steel pipe pile body. The middle parts of the three steel sheets are connected with the spring and are evenly distributed along the circumference on the side of the circular ring sleeve away from the steel pipe pile body.

[0009] Furthermore, each of the steel sheets forms a V-shaped angle of 35 to 45 degrees with the top plane of the annular sleeve.

[0010] Furthermore, the inner diameter of the circular ring sleeve is 3 to 5 mm larger than the outer diameter of the steel pipe pile body, and the circular ring sleeve is fixed to the steel pipe pile body by screws or spot welding.

[0011] Furthermore, holes are densely opened in a plum blossom shape within 1 m of the bottom of each section of the steel pipe pile body, and 10 holes are arranged in a plum blossom shape every 500 mm along the circumference of each section of the steel pipe pile body.

[0012] On the other hand, the present invention provides a construction method of a micro steel pipe pile for reinforcing a foundation in a limited working space, based on the above-mentioned micro steel pipe pile for reinforcing a foundation in a limited working space, comprising the following steps:

[0013] Step 1: Construction preparation, cleaning and leveling the site;

[0014] Step 2: Processing the steel pipe pile body, determining the diameter D and wall thickness t of the steel pipe pile body, each section of the steel pipe pile body is 1.0 to 3.0 m long, adjacent steel pipe pile bodies are connected by threaded joints, the bottom of the steel pipe pile body is processed into a truncated cone shape by a necking process, and the necking length is 150 to 300 mm, the pipe wall of the steel pipe pile body is opened in the form of a plum blossom, and the plum blossom-shaped holes are densely opened within 1.0 m of the bottom of the steel pipe pile body, and an anti-pulling structural ring is made, and the side wall of the steel pipe pile body is polished. Each section of the steel pipe pile body is screwed or spot welded with 2 to 3 anti-pulling structural rings, and the distance between the outer side of the steel sheet and the center of the steel pipe pile body is greater than the hole diameter of the steel pipe pile body by 8.0 to 10.0 cm;

[0015] Step 3: On-site inspection and acceptance of grouting micro steel pipe piles, and inspection of the appearance quality and dimensions of the steel pipe pile bodies;

[0016] Step 4: Drill holes at fixed points, locate and number the holes on the steel pipe pile body, calculate the coordinates of each pile according to the control network and use the total station to place the pile position. After measuring and placing the pile position, drive a 30cm long ф10 steel bar into the soil at the position of the pile. Tie the upper and middle parts of the steel bar with two red ropes, leaving a 30cm long red rope on the ground. During construction, find the exact pile position according to the red rope. After the pile position is laid out, the pile position needs to be rechecked before the grouting micro-pile is officially opened. Drill holes with a diameter of 15 to 40cm using a geological drill or a drilling machine.

[0017] Step 5: First hole cleaning: Drill to the designed depth, check the hole diameter, hole depth, hole position and verticality. After confirming that the hole is qualified, use the drilling rig's own circulating drilling water supply system to set the pressure of 0.2-0.5MPa for the first hole cleaning;

[0018] Step 6: Lower the steel pipe pile body, calculate the required number of sections of the steel pipe pile body, select a combination of steel pipe pile bodies of different lengths of 1.0 to 3.0 m, set an anti-pullout structural ring at the bottom of the pile end, press the steel pipe pile body with the anti-pullout structural ring into the hole section by section, and when lowering the steel pipe pile body, the steel sheets on the anti-pullout structural ring are all facing upwards until the construction depth is reached, ensuring that the pile top is 0.2 to 0.4 m above the ground;

[0019] Step 7: Lower the grouting pipe, move the drilling rig, lower a disposable U-shaped pressure grouting pipe into the steel pipe pile body of the pile body to the bottom of the pile, set movable sealing plugs on the two pipe openings of the U-shaped grouting pipe, and set a one-way valve at the bottom of the U-shaped grouting pipe for grouting;

[0020] Step 8: Grouting and hole cleaning. Connect one pipe port A of the U-shaped grouting pipe to the grouting equipment, and close the other pipe port B. Inject cement slurry into the steel pipe pile body through the grouting pipe. Set the grouting pressure to 0.2-0.5MPa. When fresh cement slurry is returned from inside and outside the steel pipe pile body, stop grouting, complete the slurry replacement in the steel pipe pile body, and keep the grouting pipe. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained.

[0021] Step 9: One-time pressure grouting. Within 25-30 minutes of grouting and hole cleaning, connect one pipe port A of the U-shaped pressure grouting pipe to the grouting equipment, and close the other pipe port B. Use the pressure grouting pipe to inject cement slurry into the steel pipe pile body at a pressure of 1.0-1.5MPa until the slurry emerges from the pile top and pile side. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained.

[0022] Step 10: Secondary pressure grouting. 60-690 minutes after the first pressure grouting is completed, one port A of the U-shaped pressure grouting pipe is connected to the grouting equipment, and the other port B is closed. 5.0-8.0 MPa high-pressure cement grouting is injected into the steel pipe pile body through the pressure grouting pipe to test the effect of the first pressure grouting and grouting. The grouting material is filled into the soil layer around the pile tip to expand to the pile head;

[0023] Step 11: Clear the slag from the pile top. 2 to 3 days after the grouting steel pipe pile construction is completed, manually chisel out the excess cement slurry gel formed by the grouting on the pile top to ensure that the pile core and the steel pipe pile body are flat and dense, and the center of the pile top is 0.2 to 0.4m above the ground to meet the subsequent construction requirements.

[0024] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a limited working space foundation reinforcement micro steel pipe pile and a construction method, which has the following technical advantages:

[0025] By setting an anti-pullout structural ring on the steel pipe pile body, three springs and steel sheets with a certain stiffness are arranged on the circular ring sleeve, and the steel sheets on the circular ring sleeve are all arranged upward, it is ensured that when the steel pipe pile body is placed downward in the hole, the steel sheets can be retracted toward the pile body. When pulling out in the reverse direction, the steel sheets arranged on the circular ring sleeve produce greater friction with the rock and soil on the side of the pile, and open away from the pile to increase resistance. The anti-pullout structural ring is conducive to fixing and centering the pile and improving the pullout and compression resistance of the pile.

[0026] Through the first grouting and hole cleaning, the first pressure grouting and the second pressure grouting, the sediment in the hole is removed and the adverse effect of the sediment on the bearing capacity is reduced, which effectively improves the wrapping effect of the cement slurry on the pile end and pile side on the steel pipe. At the same time, the second pressure grouting is high-pressure grouting. The slurry spreads to the soil near the upper and lower sides of the pile end under pressure, forming an expansion body near the pile tip, further improving the pile quality and thus improving the compressive and tensile bearing capacity;

[0027] During the grouting process, a disposable U-shaped pressure grouting pipe is lowered into the steel pipe of the pile body to the bottom of the pile. Movable sealing plugs are set at the two pipe openings of the U-shaped grouting pipe, and a one-way valve is set at the U-shaped bottom for grouting. One pipe opening A of the U-shaped pressure grouting pipe is connected to the grouting equipment, and the other pipe opening B is closed. The slurry is injected upward from the bottom of the hole through the one-way grouting valve at the bottom of the U. The slurry can also penetrate, diffuse, fill and compact through the holes in the pipe wall of the steel pipe pile body to finally form an integrated structure of the steel pipe pile body-slurry-soil solidification body. The grouting and cleaning of the U-shaped pipe are realized by switching the two pipe openings of the grouting pipe and the one-way grouting valve at the bottom of the U, so as to achieve the function of setting the grouting pipe once and grouting multiple times. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 A schematic diagram of the structure of a micro steel pipe pile for reinforcing a foundation in a limited working space provided by the present invention;

[0030] Figure 2 A schematic diagram of the structure of the anti-pullout structural ring provided by the present invention;

[0031] Figure 3 A perspective view of the end of a steel pipe pile body provided with a grouting pipe provided by the present invention;

[0032] Figure 4 A top perspective view of a steel pipe pile body provided with a grouting pipe provided by the present invention;

[0033] Figures 5A-5E A schematic diagram of the construction of micro steel pipe piles for confined working space foundation reinforcement provided by the present invention;

[0034] Figure 6 This is a schematic diagram of the plum blossom-shaped opening structure provided by the present invention.

[0035] Among them: 1 is the steel pipe pile body; 2 is the hole; 3 is the circular ring; 4 is the steel sheet and 5 is the spring. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] See also Figure 1 -5. The embodiment of the present invention discloses a micro steel pipe pile for reinforcing a foundation in a limited working space, comprising:

[0038] A steel pipe pile body 1, wherein the steel pipe pile body 1 is provided with multiple sections connected in sequence, the bottom of each section of the steel pipe pile body 1 is processed into a truncated cone shape by a necking process, the pipe wall of each section of the steel pipe pile body 1 is provided with a plum blossom-shaped opening 2, a spiral joint is provided at the connection of each section of the steel pipe pile body 1, and two adjacent sections of the steel pipe pile body 1 are connected by a spiral joint;

[0039] The pull-out structure ring comprises a circular sleeve 3, a spring 5 and a steel sheet 4. The circular sleeve 3 is sleeved on the steel pipe pile body 1. Three steel sheets 4 are arranged. The bottoms of the three steel sheets 4 are hinged to the side of the circular sleeve 3 away from the steel pipe pile body 1. The middle parts of the three steel sheets 4 are connected by springs and are evenly distributed along the circumference on the side of the circular sleeve 3 away from the steel pipe pile body 1. By arranging the pull-out structure ring on the steel pipe pile body 1, the circular sleeve 3 is provided with three steel sheets 4 with a certain rigidity. The steel sheets 4 on the circular sleeve 3 are all arranged upward, ensuring that when the steel pipe pile body 1 is placed downward in the hole, the steel sheets 4 can be retracted toward the pile body. When pulled out in the reverse direction, the steel sheets 4 arranged on the circular sleeve 3 produce greater friction with the rock and soil on the side of the pile, and open away from the pile to increase the resistance. The pull-out structure ring is conducive to the fixation and centering of the pile and the improvement of the pull-out and compression resistance of the pile.

[0040] In this embodiment, each steel sheet 4 forms a V-shaped angle of 35-45° with the top plane of the annular sleeve 3 .

[0041] In this embodiment, the inner diameter of the annular sleeve 3 is 3-5 mm larger than the outer diameter of the steel pipe pile body 1 , and the annular sleeve 3 is fixed to the steel pipe pile body 1 by screws or spot welding.

[0042] In this embodiment, the bottom of each section of the steel pipe pile body 1 is within a range of 1 m with densely opened holes 2 in a plum blossom shape, and each section of the steel pipe pile body 1 is provided with 10 holes 2 in a plum blossom shape every 500 mm along the circumference direction.

[0043] On the other hand, the present invention provides a construction method of a micro steel pipe pile for reinforcing a foundation in a limited working space, based on the above-mentioned micro steel pipe pile for reinforcing a foundation in a limited working space, comprising the following steps:

[0044] Step 1: Construction preparation, cleaning and leveling the site;

[0045] Step 2: Processing of the steel pipe pile body 1, determining the diameter D and wall thickness t of the steel pipe pile body 1, the wall thickness t is 6.0mm-12.0mm, each section of the steel pipe pile body 1 is 1.0-3.0m long, adjacent steel pipe pile bodies 1 are connected by threaded joints, the bottom of the steel pipe pile body 1 is processed into a truncated cone shape by a necking process, and the necking length is 150-300mm, the pipe wall of the steel pipe pile body 1 adopts a plum blossom-shaped opening 2, ф15-20mm, and the plum blossom-shaped encrypted opening 2 is made within 1.0m of the bottom of the steel pipe pile body 1, and an anti-pullout structural ring is made, and the side wall of the steel pipe pile body 1 is polished. Each section of the steel pipe pile body 1 is screwed or spot welded with 2-3 anti-pullout structural rings, and the anti-pullout structural ring is mainly used for fixing and centering the pile and improving the anti-pullout performance of the pile. The distance between the outer side of the steel sheet 4 and the center of the steel pipe pile body 1 is greater than the hole diameter of the steel pipe pile body 1, which is 8.0-10.0cm;

[0046] Step 3: On-site inspection and acceptance of grouting micro steel pipe piles, check the appearance quality and appearance dimensions of the steel pipe pile body 1; the cumulative area of ​​local sticky skin and pitting should not be greater than 0.5% of the total outer surface of the pile, and the depth of each sticky skin and pitting should not be greater than 5mm; appearance dimension inspection: inner diameter (0mm, +20mm), outer diameter (0mm, +20mm), pipe wall thickness (±10mm), length (0mm, +20mm);

[0047] Step 4: Drill holes 2 at fixed points, locate and number the holes 2 on the steel pipe pile body 1, calculate the coordinates of each pile according to the control network and use the total station to release the pile position. After measuring and releasing the pile position, use 30cm long ф10 steel bars to drive into the soil at the position of the pile. Tie the upper and middle parts of the steel bars with two red ropes, leaving 30cm long red ropes on the ground. During construction, find the exact pile position according to the red rope. Before the grouting micro-pile is officially opened after the pile position is laid out, the pile position needs to be rechecked for the second time. Drill holes 2 using geological drills or drilling machines to drill holes 2 with a diameter of 15 to 40cm;

[0048] Step 5: First hole cleaning 2, drill to the designed depth, check the hole diameter, hole depth, hole position and verticality, and after confirming that the hole is qualified, use the drilling rig's own circulating drilling water supply system to set the pressure of 0.2-0.5MPa to clean the hole for the first time;

[0049] Step 6: lower the steel pipe pile body 1, calculate the required number of sections of the steel pipe pile body 1, select a combination of steel pipe pile bodies 1 of different lengths of 1.0 to 3.0 m, set an anti-pullout structural ring at the bottom of the pile end, press the steel pipe pile body 1 with the anti-pullout structural ring into the hole section by section, and when lowering the steel pipe pile body 1, the steel sheets 4 on the anti-pullout structural ring are all facing upward until the construction depth is reached, ensuring that the pile top is 0.2 to 0.4 m above the ground;

[0050] Step 7: lower the grouting pipe, shift the drilling rig, lower a disposable U-shaped pressure grouting pipe into the steel pipe pile body 1 of the pile body to the bottom of the pile, set movable sealing plugs at the two pipe openings of the U-shaped grouting pipe, and set a one-way valve at the bottom of the U-shaped grouting pipe for grouting;

[0051] Step 8: Grouting and hole cleaning. Connect one pipe port A of the U-shaped grouting pipe to the grouting equipment, and close the other pipe port B. Inject cement slurry into the steel pipe pile body 1 of the pile body through the grouting pipe. Set the grouting pressure to 0.2-0.5MPa. When fresh cement slurry is returned from inside and outside the steel pipe pile body 1, stop grouting, complete the slurry replacement in the steel pipe pile body 1 of the pile body, and keep the grouting pipe. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained. The cement slurry used for grouting uses self-expanding cement as the cementitious material, and the water-cement ratio is 0.60-0.80. During the grouting process, the grouting pressure is monitored and recorded in real time.

[0052] Step 9: one-time pressure grouting. Within 20-30 minutes of grouting and hole cleaning, connect one pipe port A of the U-shaped pressure grouting pipe to the grouting equipment, and close the other pipe port B. Use the pressure grouting pipe to inject cement slurry at 1.0-1.5MPa pressure into the steel pipe pile body 1 until the slurry emerges from the pile top and pile side. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained. The cement slurry used for grouting uses self-expanding cement as the cementitious material, and the water-cement ratio is 0.45-0.6. During the grouting process, the grouting pressure is monitored and recorded in real time.

[0053] Step 10: Secondary pressure grouting. After 60-90 minutes of the first pressure grouting, one pipe port A of the U-shaped pressure grouting pipe is connected to the grouting equipment, and the other pipe port B is closed. 5.0-8.0MPa high-pressure pressurized cement grouting is injected into the steel pipe pile body 1 through the pressure grouting pipe to test the effect of the first pressure grouting and grouting. The grouting material is filled into the soil layer around the pile tip to expand to the pile head. The cement slurry used for grouting uses self-expanding cement as the cementitious material, and the water-cement ratio is 0.45-0.6. During the grouting process, the grouting pressure is monitored and recorded in real time.

[0054] Step 11: 2-3 days after the completion of the grouting steel pipe pile construction, the excess cement slurry gel formed by the grouting on the pile top is manually chiseled off to ensure that the pile core and the steel pipe pile body 1 are flat and dense, and the center of the pile top is 0.2-0.4m above the ground to meet the subsequent construction requirements.

[0055] In addition, in this embodiment, telescopic rods are provided between the middle parts of the three steel sheets 4 and the annular sleeve 3, and the spring 5 is sleeved on the telescopic rods.

[0056] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0057] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A micro steel pipe pile for reinforcing foundation in limited working space, characterized in that: include: A steel pipe pile body, wherein the steel pipe pile body is provided with multiple sections connected in sequence, the bottom of each section of the steel pipe pile body is processed into a truncated cone shape by a necking process, the pipe wall of each section of the steel pipe pile body is opened in a plum blossom form, a spiral joint is provided at the connection of each section of the steel pipe pile body, and two adjacent sections of the steel pipe pile body are connected by the spiral joint; The pull-out resistant structural ring comprises a circular ring sleeve, a spring and a steel sheet. The circular ring sleeve is sleeved on the steel pipe pile body. Three steel sheets are arranged. The bottoms of the three steel sheets are hinged to the side of the circular ring sleeve away from the steel pipe pile body. The middle parts of the three steel sheets are connected with the spring and are evenly distributed along the circumference on the side of the circular ring sleeve away from the steel pipe pile body.

2. The micro steel pipe pile for reinforcing foundation in limited working space according to claim 1, characterized in that: Each of the steel sheets forms a V-shaped angle of 35-45° with the top plane of the circular ring sleeve.

3. The micro steel pipe pile for reinforcing foundation in limited working space according to claim 1, characterized in that: The inner diameter of the circular ring sleeve is 3-5 mm larger than the outer diameter of the steel pipe pile body, and the circular ring sleeve is fixed on the steel pipe pile body by screws or spot welding.

4. The micro steel pipe pile for reinforcing foundation in limited working space according to claim 1, characterized in that: The bottom of each section of the steel pipe pile body is provided with densely-filled holes in a plum blossom shape within a range of 1m, and each section of the steel pipe pile body is provided with 10 holes in a plum blossom shape every 500mm along the circumference direction.

5. A construction method for confined working space foundation reinforcement micro steel pipe piles, according to the confined working space foundation reinforcement micro steel pipe piles according to claims 1-4, characterized in that: The following steps are involved: Step 1: Construction preparation, cleaning and leveling the site; Step 2: Processing the steel pipe pile body, determining the diameter D and wall thickness t of the steel pipe pile body, each section of the steel pipe pile body is 1.0 to 3.0 m long, adjacent steel pipe pile bodies are connected by threaded joints, the bottom of the steel pipe pile body is processed into a truncated cone shape by a necking process, and the necking length is 150 to 300 mm, the pipe wall of the steel pipe pile body is opened in the form of a plum blossom, and the plum blossom-shaped holes are densely opened within 1.0 m of the bottom of the steel pipe pile body, and an anti-pulling structural ring is made, and the side wall of the steel pipe pile body is polished. Each section of the steel pipe pile body is screwed or spot welded with 2 to 3 anti-pulling structural rings, and the distance between the outer side of the steel sheet and the center of the steel pipe pile body is greater than the hole diameter of the steel pipe pile body by 8.0 to 10.0 cm; Step 3: On-site inspection and acceptance of grouting micro steel pipe piles, and inspection of the appearance quality and dimensions of the steel pipe pile bodies; Step 4: Drill holes at fixed points, locate and number the holes on the steel pipe pile body, calculate the coordinates of each pile according to the control network and use the total station to place the pile position. After measuring and placing the pile position, drive a 30cm long ф10 steel bar into the soil at the position of the pile. Tie the upper and middle parts of the steel bar with two red ropes, leaving a 30cm long red rope on the ground. During construction, find the exact pile position according to the red rope. After the pile position is laid out, the pile position needs to be rechecked before the grouting micro-pile is officially opened. Drill holes with a diameter of 15 to 40cm using a geological drill or a drilling machine. Step 5: First hole cleaning: Drill to the designed depth, check the hole diameter, hole depth, hole position and verticality. After confirming that the hole is qualified, use the drilling rig's own circulating drilling water supply system to set the pressure of 0.2-0.5MPa for the first hole cleaning; Step 6: Lower the steel pipe pile body, calculate the required number of sections of the steel pipe pile body, select a combination of steel pipe pile bodies of different lengths of 1.0 to 3.0 m, set an anti-pullout structural ring at the bottom of the pile end, press the steel pipe pile body with the anti-pullout structural ring into the hole section by section, and when lowering the steel pipe pile body, the steel sheets on the anti-pullout structural ring are all facing upwards until the construction depth is reached, ensuring that the pile top is 0.2 to 0.4 m above the ground; Step 7: Lower the grouting pipe, move the drilling rig, lower a disposable U-shaped pressure grouting pipe into the steel pipe pile body of the pile body to the bottom of the pile, set movable sealing plugs on the two pipe openings of the U-shaped grouting pipe, and set a one-way valve at the bottom of the U-shaped grouting pipe for grouting; Step 8: Grouting and hole cleaning. Connect one pipe port A of the U-shaped grouting pipe to the grouting equipment, and close the other pipe port B. Inject cement slurry into the steel pipe pile body through the grouting pipe. Set the grouting pressure to 0.2-0.5MPa. When fresh cement slurry is returned from inside and outside the steel pipe pile body, stop grouting, complete the slurry replacement in the steel pipe pile body, and keep the grouting pipe. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained. Step 9: One-time pressure grouting. Within 20-30 minutes of grouting and hole cleaning, connect one pipe port A of the U-shaped pressure grouting pipe to the grouting equipment, and close the other pipe port B. Use the pressure grouting pipe to inject cement slurry into the steel pipe pile body at a pressure of 1.0-1.5MPa until the slurry emerges from the pile top and pile side. After grouting, open the pipe port B and inject clean water into the pipe port A of the grouting pipe to ensure that the cement slurry in the U-shaped pipe is completely drained. Step 10: Secondary pressure grouting. 60-90 minutes after the first pressure grouting is completed, one port A of the U-shaped pressure grouting pipe is connected to the grouting equipment, and the other port B is closed. 5.0-8.0MPa high-pressure cement grouting is injected into the steel pipe pile body through the pressure grouting pipe to test the effect of the first pressure grouting and grouting. The grouting material is filled into the soil layer around the pile tip to expand to the pile head; Step 11: Clear the slag from the pile top. 2 to 3 days after the grouting steel pipe pile construction is completed, manually chisel out the excess cement slurry gel formed by the grouting on the pile top to ensure that the pile core and the steel pipe pile body are flat and dense, and the center of the pile top is 0.2 to 0.4m above the ground to meet the subsequent construction requirements.

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