Sleeve type long spiral press-grouting pile construction method

Abstract

The invention relates to the technical field of pile foundation construction, in particular to a casing pipe type long spiral press-grouting pile construction method which comprises the steps that a measurement control net is established based on the axis of a building, a pile site is accurately positioned, a crawler crawling type long spiral drilling machine is adopted for positioning, a spiral rod is installed on the drilling machine, and the long spiral drilling machine drives the spiral rod to drill to the designated depth. In the drilling process, mud containing bentonite is continuously sprayed out through a first spraying hole of the screw rod to lubricate the hole wall, after drilling is completed, concrete is sprayed out through the first spraying hole of the screw rod, the screw rod is pulled out of a drill hole after spraying is completed, a spiral pipe pressing machine is adopted to rotationally press the steel casing into the drill hole, the mud containing bentonite is injected through a grouting opening of the steel casing, and the hole wall is lubricated. After the steel casing is pressed in, the reinforcement cage is pressed into the drill hole, and the machine is moved to the next pile position for repeated construction, and according to the sleeve type long spiral press-grouting pile construction method, the problems of drill hole collapse, hole shrinkage and the like are effectively prevented through the combination of double slurry protection walls and permanent supporting of the steel casing.

Description

Technical Field

[0001] This invention relates to the field of pile foundation construction technology, specifically to a method for constructing sleeve-type long spiral pressure grouting piles. Background Technology

[0002] Limitations of existing auger drilling technology: In the construction of traditional long auger bored piles, the drilling process is prone to borehole collapse and diameter reduction due to borehole wall instability, especially in areas with high groundwater levels or sandy soil layers. Conventional techniques often rely on separately lowering the casing after drilling or full-process static pressure casing support. However, the former is prone to borehole collapse due to the long period of exposed hole time (collapse rate of approximately 10%-20%), while the latter has high equipment costs and low efficiency (construction efficiency reduced by 30%-40%). Some processes attempt simultaneous drilling and grouting for wall support, but single wall support measures still suffer from borehole wall friction damage during the casing pressing stage, affecting the quality of pile formation.

[0003] The shortcomings of mud wall protection and recycling technologies: Existing technologies often involve injecting mud for wall protection after drilling and before pouring concrete. However, the mud is difficult to evenly cover the borehole wall, and the mud is easily carried away when the casing is pulled out, leading to wall protection failure. Furthermore, waste mud pollutes the site and has high treatment costs (accounting for 15%-25% of construction costs). Although some processes propose mud recycling, because concrete pouring and casing operations are separated, the mud cannot be effectively recycled after being replaced by concrete, resulting in resource waste and environmental pollution.

[0004] Chinese patent CN111206575A discloses a construction method for long spiral pressure grouting piles. By leaving a second steel casing inside the borehole, the bearing capacity of the pile foundation can be effectively improved. At the same time, the construction method can be adapted to more construction environments and effectively reduce construction costs. However, the above solution has a problem: the diameter of the steel casing is larger than the diameter of the spiral rod, so the movement of the steel casing downward with the spiral rod during drilling cannot be realized.

[0005] Therefore, we propose a casing-type long spiral pressure grouting pile construction method. Summary of the Invention

[0006] One of the technical problems this application aims to solve is that conventional spiral drilling technology is prone to hole collapse due to long open hole time, and the equipment cost is high and the efficiency is low. The casing pressure causes friction damage to the hole wall and the mud is difficult to evenly cover the hole wall. In some technologies, the diameter of the steel casing is larger than the diameter of the spiral rod, so the movement of the steel casing downward with the spiral rod during drilling cannot be realized.

[0007] To address the aforementioned technical problems, this application provides a method for constructing a casing-type long spiral pressure grouting pile, comprising the following steps: S1: Establish a measurement control network based on the building axis to accurately locate the pile points; S2: The crawler-type long spiral drilling rig is positioned and the rig is equipped with a spiral rod; S3: The long spiral drilling rig drives the spiral rod to drill to the specified depth. During the drilling process, slurry containing bentonite is continuously sprayed out through the nozzle of the spiral rod to lubricate the hole wall. S4: After drilling is completed, concrete is sprayed through the nozzle of the auger rod. After the spraying is completed, the auger rod is pulled out of the borehole. S5: A spiral pipe press is used to rotate and press the steel casing into the borehole. When the height of the steel casing is spun more than halfway, slurry containing bentonite is injected through the grouting port of the steel casing. The slurry flows through the annular groove and guide groove of the steel casing in sequence, and finally sprays out from the second nozzle to lubricate the borehole wall for a second time. S6: After the steel casing is pressed in, press the reinforcing cage into the borehole; S7: Move the machine to the next pile location and repeat the construction.

[0008] In some embodiments, the spiral rod includes a rod body, blades spirally disposed on the rod body, and nozzles linearly distributed along the length of the rod body. The nozzles are located between the blades and arranged in a radial circumferential array. The rod body has a grouting channel communicating with the nozzles.

[0009] In some embodiments, a grouting port is provided at the end of the steel casing, the tail end of the grouting port is connected to an annular groove, the annular groove is connected to a guide groove, and the end of the guide groove is connected to a second spray hole.

[0010] In some embodiments, the bentonite-containing slurry in S3 is pumped into the grouting channel through the tail end of the screw rod and sprayed out through the nozzle to form a slurry wall protection layer.

[0011] In some embodiments, in S4, before concrete spraying, clean water is pumped into the grouting channel to clean the channel and the first spray hole, and then the concrete is pumped.

[0012] In some embodiments, during the steel casing spinning process in S5, the slurry is sprayed out through the second spray hole to cover the gap between the hole wall and the outer wall of the steel casing.

[0013] In some embodiments, the steel casing is permanently left in the borehole, and the concrete injected in S4 replaces the drilling mud to achieve mud recycling.

[0014] In some embodiments, the nozzles of the screw are provided with 4-8 nozzles at equal angles on each circumference of the screw.

[0015] In some embodiments, the annular groove of the steel casing is a circumferential annular groove, and the guide groove is a groove extending along the axial direction of the casing.

[0016] In some embodiments, the grouting pressure in S5 is controlled at 0.5-1.2 MPa, and the weight ratio of bentonite in the grout is 8%-12%.

[0017] The present invention has at least the following beneficial effects: 1. During drilling with a auger, bentonite-containing drilling mud is simultaneously injected to initially form a mud wall protection layer. When the steel casing is spun to half its height, mud is injected a second time through its injection port, annular groove, and nozzle to further lubricate the borehole wall and enhance the wall protection effect. This double mud wall protection, combined with the permanent support of the steel casing, effectively prevents borehole collapse and diameter reduction. Simultaneously, the steel casing integrates with the concrete pile, enhancing the pile's resistance to lateral pressure. Furthermore, the mud is replaced during concrete pouring, achieving recycling, reducing mud waste, lowering construction costs, and being environmentally friendly.

[0018] 2. The auger rod integrates drilling, shotcreting, and concrete pouring functions, achieving multi-process integration through grouting channels and nozzles, avoiding the time-consuming issues of drill bit replacement or equipment switching in traditional processes. The steel casing adopts a linked mechanism of auger pressing and segmented grouting, ensuring both casing pressing accuracy and avoiding hole wall damage caused by forced driving. Furthermore, clean water rinsing of the grouting channels prevents concrete residue from clogging nozzles, extending the service life of the auger rod. The overall process is tightly integrated, shortening the single-pile construction cycle and reducing equipment maintenance costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the screw rod structure of the present invention; Figure 2 This is a partial cross-sectional view of the helical rod structure of the present invention; Figure 3 This is a schematic diagram of the steel casing structure of the present invention; Figure 4 This is a schematic diagram of the steel casing structure of the present invention; Figure 5 for Figure 4 Enlarged view of point A in the middle; Figure 6 These are the front view and BB cross-sectional view of the steel casing of the present invention; Figure 7 This is a schematic diagram of the construction steps of the present invention.

[0020] In the diagram: 100-Helical rod; 101-Blade; 102-Spray hole one; 103-Rod body; 104-Grouting channel; 200-Steel casing; 201-Grouting port; 202-Spray hole two; 203-Guide groove; 204-Annular groove. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1, please refer to Figure 1-7 This invention provides a technical solution: a method for constructing a casing-type long spiral pressure grouting pile, comprising the following steps: S1: Establish a measurement control network based on the building axis to accurately locate the pile points; S2: The positioning of the crawler-type long spiral drilling rig is adopted, and the drilling rig is equipped with a 100mm spiral rod; S3: The long spiral drilling rig drives the spiral rod 100 to drill to the specified depth. During the drilling process, the slurry containing bentonite is continuously sprayed out through the nozzle 102 of the spiral rod 100 to lubricate the hole wall. S4: After drilling is completed, concrete is sprayed through the nozzle 102 of the auger rod 100. After the spraying is completed, the auger rod 100 is pulled out of the hole. S5: A spiral pipe press is used to rotate and press the steel casing 200 into the borehole. When the height of the steel casing 200 is spun more than halfway, slurry containing bentonite is injected through the grouting port 201 of the steel casing 200. The slurry flows through the annular groove 204 and the guide groove 203 of the steel casing 200 in sequence, and finally sprays out from the second nozzle 202 to lubricate the borehole wall for a second time. S6: After the steel casing is pressed in 200mm, press the reinforcing cage into the borehole; S7: Move the machine to the next pile location and repeat the construction.

[0023] Specifically, the purpose of this design is to spray bentonite mud during S3 drilling to immediately seal the pores in the borehole soil, preventing borehole collapse during the drilling stage and avoiding pile diameter reduction or pile breakage due to borehole wall collapse. During S5 casing installation, secondary grouting is applied to eliminate frictional resistance between the casing and the borehole wall, ensuring casing verticality and preventing casing tilting that could hinder the lowering of the reinforcing cage. The guide channel 203 and annular groove 204 achieve uniform circumferential distribution of mud on the outer wall of the casing, eliminating casing jamming caused by insufficient lubrication in certain areas of the borehole wall.

[0024] Specifically, the core function of the guide channel 203 is to direct the flow, axially diverting the mud injected through the grouting port 201 to different depths (non-radial diffusion) to ensure continuous lubrication of the entire borehole wall. Pressure equalization is achieved by offsetting the uneven lateral pressure of the soil on the casing through the axial channel, reducing the risk of deviation during casing insertion.

[0025] Specifically, the synergistic mechanism of the annular groove 204 is as follows: the mud is distributed circumferentially, collecting the mud transported by the guide groove 203 and uniformly filling the entire circumference of the outer wall of the casing. Dynamic pressure buffering is also provided, with the annular cavity storing mud and continuously releasing a lubricating layer as the casing rotates.

[0026] The final output of nozzle 202 is that the mud flows through the guide channel 203 → annular channel 204 → nozzle 202, forming a three-stage guide system of "axial-circumferential-radial" to achieve 360° coverage of the borehole wall.

[0027] Specifically, the differences compared to traditional methods are shown in the table below: This design, through the fluid control structure of the guide channel 203 and the annular channel 204, achieves directional penetration of mud into the borehole wall, reducing the resistance to casing insertion; stress homogenization at the casing-soil interface ensures the vertical accuracy of the pile; and seamless bonding between concrete and soil enhances the end bearing capacity of the pile foundation. Essentially, it replaces brute force construction with fluid mechanics principles, making it particularly suitable for ultra-high-rise pile foundation projects in soft soil regions such as the Yangtze River Delta and Pearl River Delta.

[0028] Example 2, please refer to Figure 1-6 The spiral rod 100 includes a rod body 103, blades 101 spirally disposed on the rod body 103, and nozzles 102 linearly distributed along the length of the rod body 103. The nozzles 102 are located between the blades 101 and arranged in a radial circumferential array. The rod body 103 is provided with a grouting channel 104 communicating with the nozzles 102.

[0029] Specifically, this setup aims to achieve the following: the blade 101 cuts the soil to form a pile hole, the spiral structure assists in slag removal, and increases drilling speed by 20%-30%. The spray hole 102 provides radial and uniform injection of mud / concrete, ensuring real-time wall protection and reducing hole collapse rate by over 60%. The grouting channel 104 separates and transports mud and concrete, preventing pipeline blockage and increasing material utilization to 95%.

[0030] Specifically, the cutting blade 101 and the nozzle 102 are coordinated in time and space, with the nozzle 102 positioned between adjacent cutting blades 101. The centrifugal force field generated by the rotation of the cutting blade 101 accelerates the radial penetration of the drilling mud. A circumferential array arrangement (typically 6-8 holes / ring) ensures 360° full-section coverage. Dynamic control is employed: during the drilling phase, the cutting blade 101 cuts the soil, and the nozzle simultaneously injects bentonite mud to fill the cutter marks and fissures; during the drill lifting phase, the cutting blade 101 rotates in the opposite direction to compact the soil, and the nozzle switches to inject concrete to replace the mud.

[0031] The fluid dynamics of the grouting channel 104 are optimized so that the channel diameter is ≥ 1 / 5 of the drill pipe outer diameter, reducing pumping resistance and preventing grout segregation; the inner wall smoothness is Ra≤3.2μm (mirror polishing), reducing friction loss and extending pump life; the diversion logic ensures that the interval between mud and concrete switching is ≤10 seconds, preventing cross-contamination of grout.

[0032] The geomechanical effects of radial injection include pressure permeation, where the injection hole 102 jets mud at a pressure of 0.5-1.0 MPa, allowing the mud to permeate to a range of 2-3 times the pile diameter around the hole, forming a hardened mud cake to protect the wall (permeation and solidification time ≤30 minutes); and stress compensation, where the injected grout reverses and squeezes the soil around the hole wall, offsetting the lateral stress loss caused by drilling unloading and maintaining the in-situ strength of the soil.

[0033] Example 3, see Figure 1-6 The steel casing 200 is provided with a grouting port 201 at the end. The end of the grouting port 201 is connected to the annular groove 204. The annular groove 204 is connected to the guide groove 203. The end of the guide groove 203 is connected to the second spray hole 202.

[0034] Specifically, the purpose of this setup is as follows: Grouting port 201 is the starting point for mud input, controlling flow rate and pressure to establish an initial pumping pressure (0.5-1.2 MPa). Circular groove 204 is an annular pressure buffer chamber that evenly distributes the mud; its annular cross-section reduces flow velocity, achieving uniform pressure distribution. Guide channel 203 provides axial directional guidance, transporting the mud to the target area; the channel cross-section gradually changes to control the flow velocity. Spray hole 202 radially injects mud, forming a lubricating film with a jet diffusion angle of 15°-30°, covering the gap between the casing and the borehole wall.

[0035] The three-stage flow guidance system dynamics consist of two stages: Stage 1 (annular groove 204): Slurry enters the annular groove 204 (20mm width × 15mm depth) from the injection port 201. The annular structure converts fluid kinetic energy into static pressure energy, eliminating pumping pressure pulsations. Stage 2 (flow guide trough 203): Flow guide troughs 203 (rectangular cross-section 10mm × 8mm) extend axially along the casing, with a set every 1m (typically 6 troughs / set), axially diverting the slurry from the annular groove 204 to different depths.

[0036] The three-stage spraying (orifice 202) has an orifice diameter of 5-8mm and is arranged radially at a 45° angle. It uses the centrifugal force of the rotating casing (5-10 rpm) to evenly coat the orifice wall with mud, forming a 0.5-1.0mm thick lubricating film.

[0037] The differences between this and a traditional casing are shown in the table below.

[0038] Example 4, see Figure 1-6 S3 contains bentonite slurry which is pumped into the grouting channel 104 through the tail end of the screw rod 100 and sprayed out through the nozzle 102 to form a slurry wall protection layer.

[0039] Specifically, the purpose of this setup is to allow the grouting channel 104 to be pumped into the tail end, avoiding the external grouting pipe from wrapping around the drill rod and simplifying the construction process. The nozzles 102 are arranged in a radial array to eliminate blind spots in the wall protection and cover the entire hole circumference; the nozzle layout between the blades 101 allows for immediate grouting to fill the cracks after the blades 101 cut the soil.

[0040] The mud flow is as follows: pumped in at the tail end → axially conveyed through grouting channel 104 → radially injected through nozzle 102 → seeped into the soil through the cutting surface of blade 101. During the seepage aging process, bentonite particles (≤2μm in diameter) seep into the pores of the soil around the hole along with the mud, forming a seepage zone (3-5 times the pile diameter in width). The bentonite expands upon contact with water, reducing the permeability coefficient of the soil in the seepage zone to the 10⁻⁷ cm / s level within 30 minutes, thus blocking groundwater seepage.

[0041] The formation process of the mud wall protection layer involves several stages: In the injection stage, mud is injected into the borehole wall at a pressure of 0.8-1.2 MPa, breaking up loose soil and compacting the contact surface. In the settling stage, bentonite particles adsorb and form a gel structure, providing 60-110 kPa of lateral support. In the solidification stage, the mud shrinks and hardens after losing water, forming a rigid mud cake 0.5-1.0 mm thick.

[0042] The nozzle 102 and the blade 101 are coordinated in time and space, with the nozzle 102 positioned between the blades 101. The centrifugal force of the rotating blades 101 (15-30 rpm) propels the mud against the borehole wall. The circumferential array arrangement (conventional 6 boreholes / ring, 60° angle) achieves 360° coverage without blind spots. In terms of timing, after the blades 101 cut the soil, the nozzle 102 immediately injects mud to fill the micro-cracks on the cutting surface, suppressing unloading and rebound deformation.

[0043] Example 5, see Figure 1-6 In S4, before concrete spraying, clean water is pumped into the grouting channel 104 to clean the channel and the spray hole 102, and then the concrete pumping is switched.

[0044] Specifically, the purpose of this design is to thoroughly remove bentonite slurry residue by rinsing with clean water, and to prevent the slurry from mixing into the concrete to form a weak interlayer; to switch the fluid to establish a pure concrete delivery interface, and to prevent slurry clumps in the grouting channel 104 from clogging the nozzles; and to maintain the nozzles to prevent the dried slurry film from sticking to the nozzles, thereby reducing the effective diameter of the nozzles and causing a sudden increase in pump pressure.

[0045] The mechanism of water flushing involves turbulent scouring, where high-speed water flow (velocity ≥ 2 m / s) tears apart the colloidal structure of the mud, with water pressure = 0.8-1.2 MPa (> mud viscosity resistance). Ion replacement occurs, where water dilutes the Na+ / Ca2+ ion concentration, and the flushing water volume is ≥ 3 times the channel volume; surface energy disrupts the water molecule penetration domain of the bentonite layers, breaking down electrostatic attraction, with a flushing time ≥ 30 seconds.

[0046] Example 6, see Figure 1-6 In S5, when the steel casing 200 is spun, the mud is sprayed out through the second nozzle 202 to cover the gap between the nozzle wall and the outer wall of the steel casing 200.

[0047] Specifically, the purpose of this design is to solve the problems of deflection, jamming and hole wall disturbance during the pressing of the steel casing 200 through dynamic mud film construction and tribological optimization. Its technical essence is to use fluid lubrication to replace mechanical friction.

[0048] Specifically, the dynamic formation process of the mud film involves: spraying and covering, with mud ejected from nozzle 202 at a 45° angle at a jet velocity of 2-3 m / s and a diffusion angle of 20°-30°; spun spreading; centrifugal homogenization by rotating the casing (8-12 rpm); centrifugal acceleration ≥0.5g to ensure 360° coverage; and pressure infiltration, where the mud infiltrates into the soil at a pressure of 0.3-0.5 MPa to a depth of 3-5 cm, forming a composite protective layer.

[0049] Specifically, nozzle 202 radially sprays to establish an initial lubrication layer, preventing scraping of the hole wall when the end of the casing gets stuck; the casing spins, converting the rotational force into a circumferentially distributed driving force for the mud, with the lubrication film thickness fluctuating by <±0.1mm; the guide groove 203 system maintains constant lubrication pressure throughout the entire depth, with the pressure fluctuation being <±10%.

[0050] This design utilizes the dynamic coupling effect of spinning and spraying to convert mechanical friction into fluid friction, overcoming the limit of casing indentation resistance; it uses centrifugal force to force homogenization and eliminate verticality deviation; and it simultaneously reinforces the borehole wall, replacing the traditional pre-grouting process.

[0051] In Example 7, the steel casing 200 is permanently left in the borehole, and the concrete injected in S4 replaces the mud in the borehole to achieve mud recycling.

[0052] Specifically, the purpose of this design is to provide structural replacement, with the outer wall of the casing combined with the concrete to form a composite pile body, thereby increasing the shear strength of the pile body and eliminating the need for the casing extraction process; the borehole wall experiences zero disturbance, avoiding concrete segregation caused by the traditional casing extraction, reducing the pile defect rate from 8% to 0.5%, shortening the construction period, and eliminating the casing extraction and backfilling processes.

[0053] Example 8: The nozzle 102 of the spiral rod 100 has 4-8 nozzles at equal angles on each circumference of the rod body 103. The annular groove 204 of the steel casing 200 is a circumferential annular groove, and the guide groove 203 is a groove extending along the axial direction of the casing. The grouting pressure in S5 is controlled at 0.5-1.2 MPa, and the weight ratio of bentonite in the slurry is 8%-12%.

[0054] Specifically, the design aims to achieve the following: 4 orifices ensure structural strength (section attenuation rate < 5%); 6 orifices cover a blind zone < 15°, ensuring optimal mud penetration uniformity; 8 orifices provide full circumference coverage without blind zones (redundant design). The orifice center angle θ = 360° / 6 = 60° ensures a continuous overlapping zone of the jet on the orifice wall. The 204 annular groove has a semi-circular cross-section (R = 10mm) to reduce stress concentration; the groove depth / cylinder wall thickness ratio is 15mm / 20mm = 0.75 to ensure a safety factor for the remaining wall thickness strength; and the circumferential continuity is 360° without interruption to eliminate pressure fluctuations.

[0055] The following is combined with Figures 1-6 The working process of the screw rod 100 and the steel casing 200 is as follows.

[0056] The long spiral drilling rig drills holes through the spiral rod 100. During the drilling process, the soil is carried out of the hole by the rotating blades 101 of the spiral rod 100. At the same time, mud containing bentonite is introduced through the connection with the tail end of the spiral rod 100. It enters the spiral rod 100 through the grouting channel 104 and is sprayed out through the nozzle 102 of the spiral rod 100, which lubricates the hole wall and plays a role in mud wall protection. After drilling to the specified depth, clean water is injected into the grouting channel 104 to clean the grouting channel 104 and the nozzle 102. Then, concrete is sprayed into the grouting channel 104 until the concrete spraying is completed. Subsequently, a spiral pipe press is used to rotate and press the steel casing 200 into the borehole. During the spinning process, the outer wall of the steel casing 200 can support the borehole wall. When the height of the steel casing 200 is spun to half, slurry containing bentonite is injected through the grouting port 201 of the steel casing 200. The slurry flows through the grouting port 201 of the steel casing 200 into the annular groove 204, and then from the annular groove 204 into the guide groove 203. Finally, it is ejected from the second nozzle 202 through the guide groove 203, further lubricating the borehole wall and playing the role of slurry wall protection. The steel casing 200 is not removed. At the same time, since the density of concrete is greater than that of slurry, the slurry can be displaced during the entire grouting process, achieving the purpose of slurry recycling.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for constructing casing-type long spiral pressure grouting piles, characterized in that: Includes the following steps: S1: Establish a measurement control network based on the building axis to accurately locate the pile points; S2: The crawler-type long auger drilling rig is positioned and the auger rod (100) is installed on the drilling rig. S3: The long spiral drilling rig drives the spiral rod (100) to drill to a specified depth. During the drilling process, slurry containing bentonite is continuously sprayed out through the nozzle (102) of the spiral rod (100) to lubricate the hole wall. S4: After drilling is completed, concrete is sprayed through the first nozzle (102) of the spiral rod (100). After the spraying is completed, the spiral rod (100) is pulled out of the borehole. S5: A spiral pipe press is used to rotate and press the steel casing (200) into the borehole. When the height of the steel casing (200) is spun more than halfway, slurry containing bentonite is injected through the grouting port (201) of the steel casing (200). The slurry flows through the annular groove (204) and the guide groove (203) of the steel casing (200) in sequence, and finally sprays out from the second nozzle (202) to lubricate the borehole wall for a second time. S6: After the steel casing (200) is pressed in, the reinforcing cage is pressed into the borehole; S7: Move the machine to the next pile location and repeat the construction.

2. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: The spiral rod (100) includes a rod body (103), blades (101) spirally arranged on the rod body (103), and nozzles (102) linearly distributed along the length of the rod body (103). The nozzles (102) are located between the blades (101) and arranged in a radial circumferential array. The rod body (103) has a grouting channel (104) communicating with the nozzles (102).

3. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: The steel casing (200) is provided with the grouting port (201) at the end. The end of the grouting port (201) is connected to the annular groove (204). The annular groove (204) is connected to the guide groove (203). The end of the guide groove (203) is connected to the second spray hole (202).

4. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: The bentonite-containing slurry in S3 is pumped into the grouting channel (104) through the tail end of the screw rod (100) and sprayed out through the nozzle (102) to form a slurry wall protection layer.

5. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: In S4, before concrete injection, clean water is pumped into the grouting channel (104) to clean the channel and the first spray hole (102), and then the concrete is pumped.

6. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: In S5, when the steel casing (200) is spun, the mud is sprayed out through the second nozzle (202) to cover the gap between the hole wall and the outer wall of the steel casing (200).

7. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: The steel casing (200) is permanently left in the borehole, and the concrete injected in S4 replaces the mud in the borehole to achieve mud recycling.

8. The construction method for casing-type long spiral pressure grouting piles according to claim 2, characterized in that: The nozzle 1 (102) of the spiral rod (100) has 4-8 nozzles at equal angles on each circumference of the rod body (103).

9. The construction method for casing-type long spiral pressure grouting piles according to claim 3, characterized in that: The annular groove (204) of the steel casing (200) is a circumferential annular groove, and the guide groove (203) is a groove extending along the axial direction of the casing.

10. The construction method for casing-type long spiral pressure grouting piles according to claim 1, characterized in that: The grouting pressure in S5 is controlled at 0.5-1.2 MPa, and the weight ratio of bentonite in the slurry is 8%-12%.

Images