Pile forming device based on magnetic fluid drainage and cement extrusion and construction method

Abstract

The invention discloses a pile forming device based on magnetic fluid drainage and cement extrusion, which comprises a pile casing made of high-strength carbon steel, and the inner wall of the pile casing is pre-coated with a sulphoaluminate expanding agent layer; the guide pipe is connected with the pile casing and used for pouring cement paste; a magnetic liquid discharging and cement extruding integrated device integrates a magnetic field generator, a magnetic liquid storage chamber, a mixed liquid storage chamber, a cyclone separator and a sprayer. The magnetic field generator is located at the bottom of the device and vertically and downwards generates a 0.5-1.5 T magnetic field to drive the magnetic liquid to be separated from the cement mixed liquid; a filtering opening is formed in the outer side of the protective cylinder, is connected with the two-stage cyclone separator and is used for separating magnetic particles and recovering magnetic liquid. The directional drainage channel is constructed through the magnetic liquid layer, magnetic field induction and a multi-stage pressurization technology are combined, the drainage efficiency and the pile body compactness are remarkably improved, meanwhile, controllable expansion of the pile diameter is achieved through the pile casing expanding agent layer, and the pile foundation bearing capacity is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering pile foundation construction, and in particular to a pile forming device and construction method based on magnetic fluid drainage and cement extrusion. Background Art

[0002] In traditional pile foundation construction, after the cement slurry is poured, natural drainage or vacuum preloading method is relied on to remove the free water, which has low efficiency and is likely to cause insufficient compactness of the pile body. In the prior art, although mechanical extrusion drainage can improve the compactness, there are problems such as complex equipment, high energy consumption, and difficulty in completely removing the residual water. In addition, the diameter of the pile body is fixed after forming and cannot compensate for the formation deformation through post - expansion.

[0003] Therefore, a pile forming device and construction method based on magnetic fluid drainage and cement extrusion are proposed to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above - mentioned deficiencies, and provide a pile forming device and construction method based on magnetic fluid drainage and cement extrusion. By constructing a directional drainage channel with a magnetic fluid layer, combining magnetic field induction and multi - stage pressurization technology, the drainage efficiency and the compactness of the pile body are significantly improved. At the same time, the diameter of the pile can be controllably expanded by using the casing expansion agent layer to enhance the bearing capacity of the pile foundation, thereby solving the problems raised in the background art.

[0005] In order to solve the above - mentioned technical problems, the technical solution adopted by the present invention is: a pile forming device based on magnetic fluid drainage and cement extrusion, comprising: a casing made of high - strength carbon steel, with a thioaluminate - type expansion agent layer pre - coated on the inner wall; a conduit connected to the casing for pouring cement slurry; an integrated device for magnetic fluid discharge and cement extrusion, which integrates a magnetic field generator, a magnetic fluid storage chamber, a mixed liquid storage chamber, a cyclone separator and a sprayer; the magnetic field generator is located at the bottom of the device, generating a magnetic field of 0.5 - 1.5T vertically downward to drive the separation of the magnetic fluid and the cement mixed liquid; a filter port is provided on the outer side of the casing, connected to two - stage cyclone separators for separating magnetic particles and recovering the magnetic fluid.

[0006] Preferably, the expansion agent layer on the inner wall of the casing is made by mixing thioaluminate - type expansion material and cement - based binder in a ratio of 3:1, the expansion trigger time is 10 - 30 minutes after the casing is pulled out, and the expansion rate is 15 - 25%.

[0007] Preferably, the magnetic field generator is an electromagnet array, the arrangement spacing is 20 - 50cm, and the magnetic field action range covers an area of 0.5 - 1m around the bottom of the casing.

[0008] Preferably, the cyclone separator includes a first - stage 20 - mesh filter screen and a second - stage centrifugal dehydration module, so that the solid content of the accumulated water is ≤0.1%.

[0009] Preferably, the magnetic fluid in the magnetic fluid storage chamber comprises magnetic microparticles with a particle size of 0.1 - 2 mm, a base fluid, a surfactant, and a fiber reinforcing material, wherein the magnetic microparticles account for 30 - 50% and the fiber material accounts for 1 - 3%.

[0010] Preferably, the integrated adjustable nozzle, pressure sensor, and PLC control system of the magnetic fluid discharge and cement extrusion integrated device have a control accuracy of ±5%.

[0011] Preferably, the inner wall of the conduit is coated with polyurethane or lined with a stainless steel layer, and the cement slurry with a water-cement ratio of 0.4 - 0.6 is poured into the casing through it.

[0012] Preferably, the wall thickness of the casing is 8 - 15 mm, the outer layer is covered with a glass fiber reinforced plastic thin shell, and the inner layer is a degradable polyethylene film.

[0013] In addition, the present invention also discloses a construction method based on the magnetic fluid drainage and cement extrusion pile-forming device, comprising the following steps: Step 1: Spray the magnetic fluid on the bottom and periphery of the casing to form a magnetic fluid layer of 5 - 10 cm; Step 2: Start the magnetic field generator to induce the migration of free water and suction-separate the accumulated water containing magnetic fluid; Step 3: After pouring the cement slurry, pressurize and drain water in three stages, with a compactness ≥95%; Step 4: Pull out the casing to trigger the expansion agent layer to expand the pile diameter by 10 - 30%.

[0014] Furthermore, the staged pressurization in Step 3 includes: the first stage is to drain free water at 0.5 MPa for 2 minutes, the second stage is to drain capillary water at 1.5 MPa for 3 minutes, and the third stage is to compact the cement slurry at 2.5 MPa for 5 minutes.

[0015] The present invention has the following beneficial effects: 1. By constructing a magnetic fluid directional drainage channel and a multi-stage staged pressurization technique, the present invention realizes the rapid separation and discharge of free water and capillary water, making the compactness of the pile body ≥95%, and solving the problems of excessive water residue and insufficient compactness in traditional construction; 2. By integrating a PLC control system and an adjustable nozzle, the present invention dynamically adjusts the magnetic field strength, magnetic fluid spraying amount, and extrusion pressure according to the casing diameter and foundation parameters, with a control accuracy of up to ±5%, significantly improving the construction adaptability and process reliability; 3. By adopting a two-stage cyclone separator and a magnetic block array adsorption technique, the present invention realizes a magnetic microparticle recovery rate ≥95%, has a high magnetic fluid recycling utilization rate, reduces material waste, lowers construction costs, and conforms to the concept of green environmental protection construction; 4. The present invention pre - coats a layer of sulfoaluminate expansive agent on the inner wall of the casing. After the casing is pulled out, expansion is triggered, causing the pile diameter to increase by 10 - 30%, enhancing the frictional biting force between the pile foundation and the surrounding soil, and significantly improving the bearing capacity and anti - deformation ability of the pile body. 5. Through the integrated design of functions such as magnetic fluid drainage, cement extrusion, and casing expansion, the present invention simplifies the traditional multi - device cooperation process, shortens the construction period, and simultaneously reduces energy consumption and equipment maintenance costs, meeting the need for rapid pile formation in soft soil foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross - sectional view of the underground pile body structure of the present invention; Figure 2 is a schematic structural diagram of the integrated device for magnetic fluid drainage and cement extrusion of the present invention; Figure 3 is a schematic layout diagram of the magnetic field generator of the present invention; Figure 4 is a schematic three - dimensional structure diagram of the present invention; Figure 5 is a schematic three - dimensional structure diagram of the underground pile body of the present invention; Reference numerals: 1: Fixed cement expansion material package; 2: Casing; 3: Conduit; 4: Integrated device for magnetic fluid drainage and cement extrusion; 5: Mixed liquid storage chamber; 6: Magnetic fluid storage chamber; 7: Sprayer; 8: Cyclone separator; 9: Magnetic field generator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present invention will be further described below in conjunction with the drawings and embodiments: Refer to Figures 1 to 5 , a pile - forming device based on magnetic fluid drainage and cement extrusion, comprising: a casing 2 made of high - strength carbon steel, with a layer of sulfoaluminate - type expansive agent pre - coated on the inner wall; a conduit 3 connected to the casing 2 for pouring cement slurry; an integrated device 4 for magnetic fluid drainage and cement extrusion, integrating a magnetic field generator 9, a magnetic fluid storage chamber 6, a mixed liquid storage chamber 5, a cyclone separator 8, and a sprayer 7; the magnetic field generator 9 is located at the bottom of the device, generating a magnetic field of 0.5 - 1.5T vertically downward to drive the separation of the magnetic fluid and the cement mixed liquid; a filter port is provided on the outer side of the casing 2, connected to two - stage cyclone separators 8 for separating magnetic particles and recovering the magnetic fluid. The core of this device is to drive the separation of the magnetic fluid and the cement mixed liquid through a magnetic field to achieve directional drainage; the casing and the conduit cooperate to complete cement pouring, and the integrated device integrates functions such as magnetic field control, magnetic fluid spraying, and mixed liquid recovery; specifically, a high - strength carbon steel casing with a wall thickness of 8 - 15mm can be installed to the target pile depth, the conduit is docked with the integrated device; parameters such as the casing diameter are input through the PLC system, the magnetic fluid spraying module is started, the magnetic field generator generates a magnetic field of 0.5 - 1.5T vertically downward, driving the directional flow of the magnetic fluid, and the mixed liquid is recovered through the cyclone separator.

[0018] Preferably, the expansive agent layer on the inner wall of the casing 2 is made by mixing sulfoaluminate-based expansive material and cement-based binder in a ratio of 3:1. The expansion trigger time is 10 - 30 minutes after the casing is pulled out, and the expansion rate is 15 - 25%. The expansive agent layer triggers a chemical reaction after the casing is pulled out, that is, ettringite is generated, realizing controllable expansion of the pile diameter and improving the bearing capacity of the pile foundation; the sulfoaluminate expansive agent and the cement-based binder can be mixed in a ratio of 3:1 and sprayed onto the inner wall of the casing with a thickness of 2 - 5 mm; within 10 - 30 minutes after the casing is pulled out, the expansive agent reacts with water, and the pile diameter expands by 10 - 30%.

[0019] Preferably, the magnetic field generator 9 is an electromagnet array with an arrangement spacing of 20 - 50 cm, and the magnetic field action range covers an area of 0.5 - 1 m around the bottom of the casing. The electromagnet array ensures the directional migration efficiency of the magnetic fluid through the controllable magnetic field intensity, 0.5 - 1.5 T and the distribution range; arrange electromagnets in the area of 0.5 - 1 m around the bottom of the casing, such as with a spacing of 30 cm, generate a vertically downward magnetic field after being energized, and act continuously for 10 - 20 minutes to drive the free water in the cement slurry to migrate towards the filter opening.

[0020] Preferably, the cyclone separator 8 includes a first-stage 20-mesh filter screen and a second-stage centrifugal dehydration module, so that the solid content of the accumulated water ≤ 0.1%. The two-stage separation system efficiently recovers magnetic particles and reduces the impurity content of the accumulated water to ensure the recycling of the magnetic fluid; the mixed liquid is suctioned to the cyclone separator through the filter opening of the casing. The first-stage filter screen with a particle size ≥ 0.1 mm intercepts magnetic particles, and the second-stage centrifugal module dehydrates and discharges clear water with a solid content ≤ 0.1%, and the magnetic fluid recovery rate ≥ 95%.

[0021] Preferably, the magnetic fluid in the magnetic fluid storage chamber 6 contains magnetic particles with a particle size of 0.1 - 2 mm, a base liquid, a surfactant, and a fiber reinforcing material, among which the magnetic particles account for 30 - 50% and the fiber material accounts for 1 - 3%. The fiber material, such as polypropylene fiber, can enhance the erosion resistance of the magnetic fluid, and the magnetic particles migrate directionally in the magnetic field to form a stable drainage channel; mix 40% magnetite particles, the base liquid, 2% polypropylene fiber, and the surfactant and stir to form a uniform suspension, and form a magnetic fluid layer with a thickness of 5 - 10 cm through a sprayer.

[0022] Preferably, the magnetic fluid discharge and cement extrusion integrated device 4 integrates an adjustable nozzle, a pressure sensor, and a PLC control system with a control accuracy of ±5%. The PLC system dynamically adjusts the magnetic fluid spraying amount, magnetic field intensity, and extrusion pressure according to the casing parameters to achieve precise construction; input the casing diameter, such as 1 m, and the pile length, such as 15 m, and the PLC automatically calculates that the magnetic fluid spraying amount is 200 L, and the extrusion pressure is increased in stages, and the pressure fluctuation is monitored in real time and adjusted.

[0023] Preferably, the inner wall of the conduit 3 is coated with polyurethane or lined with a stainless steel layer, and the cement slurry with a water-cement ratio of 0.4 - 0.6 is poured into the casing 2 through it. The inner wall coating reduces the flow resistance of the cement slurry, prevents the conduit from being blocked, and ensures the perfusion uniformity; seamless steel pipes are used, with a polyurethane coating on the inner wall, and the cement slurry with a water-cement ratio of 0.5 containing 5% sulfoaluminate expansive agent is poured into the casing at a uniform speed to avoid pile breakage.

[0024] Preferably, the wall thickness of the casing 2 is 8 - 15 mm, with an outer covering of a glass fiber reinforced plastic thin shell and an inner layer of a degradable polyethylene film. The double-layer structure casing not only provides mechanical support but also triggers the reaction of the expansive agent after the casing is pulled out; the outer layer of the casing uses a 2-mm-thick glass fiber reinforced plastic, and the inner layer is a 0.1-mm-thick degradable polyethylene film. After the casing is pulled out, the film degrades when it meets water, releasing the expansive agent.

[0025] In addition, the present invention also discloses a construction method based on a magnetic fluid drainage and cement extrusion pile-forming device, including the following steps: Step 1: Sprinkle magnetic fluid on the bottom and around the casing to form a 5 - 10 cm magnetic fluid layer; Step 2: Start the magnetic field generator to induce the migration of free water and suck and separate the magnetic fluid-containing accumulated water; Step 3: After pouring the cement slurry, pressurize and drain water in three stages, with a compactness ≥ 95%; Step 4: Pull out the casing 2 to trigger the expansive agent layer to expand the pile diameter by 10 - 30%. Through the synergistic effect of magnetic fluid drainage and multi-stage pressurization, the problem of residual moisture in traditional construction is solved, and at the same time, the controllable expansion of the pile diameter is achieved.

[0026] Furthermore, the staged pressurization in Step 3 includes: the first stage is to drain free water at 0.5 MPa for 2 minutes, the second stage is to drain capillary water at 1.5 MPa for 3 minutes, and the third stage is to compact the cement slurry at 2.5 MPa for 5 minutes. The staged pressurization matches the different water drainage requirements, and finally the compactness ≥ 95%; the hydraulic extruder pressurizes in stages: initially 0.5 MPa to drain free water, accounting for about 60% of the total drainage volume, 1.5 MPa to drain capillary water, about 30%, and 2.5 MPa to compact the cement slurry to a compactness of 96%.

[0027] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A device for forming piles based on magnetic fluid drainage and cement extrusion, characterized in that Comprising: A casing (2) made of high-strength carbon steel, with a pre-coated layer of sulphoaluminate-based expansive agent on its inner wall; a conduit (3) connected to the casing (2) for grouting cement slurry; a magnetic fluid discharge and cement extrusion integrated device (4) integrating a magnetic field generator (9), a magnetic fluid storage chamber (6), a mixed liquid storage chamber (5), a cyclone separator (8) and a sprayer (7); the magnetic field generator (9) is located at the bottom of the device, generating a magnetic field of 0.5 - 1.5 T vertically downward to drive the separation of the magnetic fluid and the cement mixed liquid; a filter port is provided on the outer side of the casing (2), connected to two-stage cyclone separators (8) for separating magnetic particles and recovering the magnetic fluid.

2. The device for magnetic fluid drainage and cement extrusion pile forming according to claim 1, characterized in that, The expansive agent layer on the inner wall of the casing (2) is made by mixing sulphoaluminate-based expansive material and a cement-based binder in a ratio of 3:1, with an expansion trigger time of 10 - 30 minutes after the casing is pulled out and an expansion rate of 15 - 25%.

3. The device for forming piles by magnetic fluid drainage and cement extrusion according to claim 1, wherein The magnetic field generator (9) is an electromagnet array with an arrangement spacing of 20 - 50 cm, and the magnetic field action range covers an area of 0.5 - 1 m around the bottom of the casing.

4. A device for magnetic fluid drainage and cement extrusion pile formation according to claim 1, characterized in that, The cyclone separator (8) includes a first-stage 20-mesh filter screen and a second-stage centrifugal dehydration module, so that the solid content in the accumulated water is ≤ 0.1%.

5. The apparatus for magnetic fluid drainage and cement extrusion pile forming according to claim 1, wherein The magnetic fluid in the magnetic fluid storage chamber (6) contains magnetic particles with a particle size of 0.1 - 2 mm, a base liquid, a surfactant and a fiber reinforcing material, among which the magnetic particles account for 30 - 50% and the fiber material accounts for 1 - 3%.

6. The device for forming piles by magnetic fluid drainage and cement extrusion according to claim 1, wherein, The magnetic fluid discharge and cement extrusion integrated device (4) integrates an adjustable nozzle, a pressure sensor and a PLC control system with a control accuracy of ± 5%.

7. A device for forming piles by magnetic fluid drainage and cement extrusion according to claim 1, characterized in that, The inner wall of the conduit (3) is coated with polyurethane or lined with a stainless steel layer, and the cement slurry with a water-cement ratio of 0.4 - 0.6 is grouted into the casing (2) through it.

8. A device for forming piles by magnetic fluid drainage and cement extrusion according to claim 1, characterized in that, The wall thickness of the casing (2) is 8 - 15 mm, covered with a thin shell of glass fiber reinforced plastic on the outside and an inner layer of degradable polyethylene film.

9. A construction method of a pile-forming device based on magnetic fluid drainage and cement extrusion according to any one of claims 1-8, characterized in that Including the following steps: Step 1: Spray the magnetic fluid on the bottom and periphery of the casing to form a magnetic fluid layer of 5 - 10 cm; Step 2: Start the magnetic field generator to induce the migration of free water and suction-separate the accumulated water containing the magnetic fluid; Step 3: After grouting the cement slurry, pressurize and drain water in three stages, with a compactness ≥ 95%; Step 4: Pull out the casing (2) to trigger the expansive agent layer to expand the pile diameter by 10 - 30%.

10. A construction method of a pile-forming device based on magnetic fluid drainage and cement extrusion according to claim 9, characterized in that, The staged pressurization in Step 3 includes: the first stage is to drain free water at 0.5 MPa for 2 minutes, the second stage is to drain capillary water at 1.5 MPa for 3 minutes, and the third stage is to compact the cement slurry at 2.5 MPa for 5 minutes.

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