A method for correcting tilting of tall structures using micropiles based on the principle of soil electrokinetics

Abstract

This invention relates to a method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics. The method includes the following steps: constructing anode micropiles on the side of the structure with greater settlement and cathode micropiles on the side with less settlement. Both anode and cathode micropiles contain steel pipes, with the cathode micropiles having porous steel pipes and embedded filter pipes inside. The top of the steel pipe of the anode micropiles is connected to the positive terminal of a power supply, and the top of the steel pipe of the cathode micropiles is connected to the negative terminal. The filter pipes are connected to a vacuum pump. Power is supplied to the anode and cathode micropiles. After the water level is observed in the filter pipes, the vacuum pump is started to pump water. Simultaneously, the soil below the side of the structure with less settlement is treated with clay-repairing techniques until the structure tilts back to the preset position. This method overcomes the shortcomings of current methods for correcting tilt.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment and building tilt correction technology in geotechnical engineering, specifically to a method for tilt correction and reinforcement of tall structures based on the principle of soil electrokinetics. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Tall structures (such as ancient brick and stone pagodas, chimneys, power transmission towers, and water towers) are characterized by concentrated loads and sensitivity to tilting, making them prone to tilting due to uneven settlement of the foundation under long-term superstructure loads. Currently, commonly used methods for correcting tilting in engineering mainly include forced settlement, jacking, and combined methods of both. Among these, forced settlement is more widely used due to its relatively mature technology and lower cost.

[0004] The conventional process of forced settlement is as follows: First, the foundation of the building (structure) is reinforced, especially the side with greater settlement, to prevent further settlement during subsequent operations; then, the foundation soil on the side with less settlement is weakened to induce controlled settlement of the soil on that side, causing the building (structure) to tilt back.

[0005] Currently, there is an existing method for correcting building tilt based on electroosmosis technology. This method essentially uses electroosmosis to improve soil drainage efficiency, lowering the soil water level through dewatering to consolidate the soil and force the building to settle. However, this method has the following limitations: ① Dewatering is a type of forced settlement correction method, indirectly controlling the settlement of the foundation soil by controlling soil moisture. The tendency and rate of building tilting back are difficult to control, posing a high risk. ② In addition to settlement-stopping reinforcement work, electrodes and drainage boards need to be installed on the outside of the building, and a pumping and drainage system needs to be set up, resulting in high construction costs. Another method for correcting tilt is using soil removal. Soil is removed from the foundation on the side with less settlement, weakening the foundation soil on that side and causing controllable settlement. However, this method requires a large amount of soil removal, increasing the construction period and causing significant disturbance to sensitive soil foundations, making it unsuitable for correcting tilts of structures sensitive to disturbance. Summary of the Invention

[0006] In view of the shortcomings of existing technologies, the purpose of this invention is to provide a method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics, which overcomes the defects of current methods for correcting the tilt of structures.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: An embodiment of the present invention provides a method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics, comprising the following steps: Anode micropiles are constructed on the side of the structure with greater settlement, and cathode micropiles are constructed on the side with less settlement. Both anode and cathode micropiles contain steel pipes. The steel pipes in the cathode micropiles are porous steel pipes with filter pipes embedded inside. Connect the top of the steel pipe of the anode micropile to the positive terminal of the power supply, and connect the top of the steel pipe of the cathode micropile to the negative terminal; connect the filter tube to the vacuum pump. The power supply provides power to the anode micropiles and cathode micropiles. After the water level is observed in the filter tube, the vacuum pump is started to pump water. At the same time, the soil below the side of the structure with less settlement is excavated until the structure tilts back to the preset position.

[0008] Optionally, a working trench may be excavated on the side of the structure with less settlement, and the soil below the side of the structure with less settlement may be removed within the working trench.

[0009] Optionally, the anode micropile is a bored cast-in-place pile, and its construction method is as follows: first, a hole is drilled in the foundation slab of the structure and the soil below it to form a pile hole, then a steel pipe is inserted into the pile hole, and then the pile hole is grouted to form an anode micropile.

[0010] Optionally, the grouting material for the anode micropiles is carbon fiber cement slurry, which is prepared by adding carbon fiber to cement. The carbon fiber accounts for 1.5%-2% of the mass of the carbon fiber cement slurry, and the cement is silicate cement with a water-cement ratio of no more than 0.55.

[0011] Optionally, the grouting pressure is 0.3MPa-1.0MPa when grouting material is injected.

[0012] Optionally, the cathode micropile is a bored cast-in-place pile, and its construction method is as follows: first, a hole is drilled in the foundation slab of the structure and the soil below it to form a pile hole; then, a porous steel pipe is inserted into the pile hole; pebbles are filled in the gap between the porous steel pipe and the pile hole wall; a filter pipe is embedded in the porous steel pipe; then, medium and coarse sand is filled between the filter pipe and the porous steel pipe; and grouting is performed in the pile hole to form a cathode micropile.

[0013] Optionally, during the construction of cathode micropiles, a grouting pipe is embedded in a porous steel pipe before filling with medium-coarse sand. After the structure is corrected, the filter pipe is retrieved, and the grouting pipe is used to grout the pile hole to form a complete pile body.

[0014] Optionally, when grouting the cathode micropiles, silicate cement is used as the grouting material, with a water-cement ratio not exceeding 0.55.

[0015] Optionally, the grouting pressure for cathode micropiles is 0.3MPa-1.0MPa.

[0016] Optionally, terminals are welded to the top of the perforated steel tube, and the terminals are connected to the power supply via copper-core insulated wires.

[0017] The beneficial effects of this invention are as follows: 1. The method for correcting and reinforcing tilted structures of the present invention involves installing anode micropiles on the side of the structure with greater settlement and cathode micropiles on the side with less settlement. The anode and cathode micropiles are connected to a power source. On the side with less settlement, a soil removal method is used for construction. Simultaneously, a vacuum pump is used to pump water from the filter pipe inside the microcathode pile. The differential settlement formed by the drainage action assists the soil removal method in forcing the tilt. By combining soil removal and drainage, the tilt is corrected, overcoming the shortcomings of using electroosmosis technology alone. The tilting trend and rate of the building are easy to control, and the risk is low. Because drainage is used to assist the soil removal method, the amount of soil removed is reduced, the construction period is shortened, and the disturbance to sensitive soil foundations is reduced. It is suitable for historical buildings or important structures that are sensitive to disturbance.

[0018] 2. The structure tilting correction and reinforcement method of the present invention, after the anode micropiles and cathode micropiles are energized, can utilize the soil electrokinetic principle to move negatively charged soil particles toward the anode micropiles and adsorb them at the pile-soil interface, effectively densifying and improving the soil around the pile, significantly increasing the side friction resistance of the anode micropiles, enhancing the reliability and effectiveness of the settlement prevention and reinforcement, improving the bearing capacity gain of micropiles with increased pile length, and breaking through the technical bottleneck of the difficulty in improving the bearing capacity of traditional micropiles in this type of stratum.

[0019] 3. In the structural tilt correction and reinforcement method of the present invention, the anode micropiles and cathode micropiles are used as reinforcement measures, as well as electrodes and drainage, which effectively reduces the construction steps of electroosmosis application, simplifies the construction process, and saves the process and cost of additional electrode and special drainage system installation. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a flowchart of the method in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the anode micropiles and cathode micropiles arranged in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the anode micropile of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of a cathode micropile according to Embodiment 1 of the present invention; Among them, 1. Structure, 2. Pre-reinforced foundation plate, 3. Inclined angle, 4. Anode micropile, 5. Cathode micropile, 6. DC power supply, 7. Power supply circuit, 8. Vacuum pump, 9. Water pipe, 10. Working trench, 11. Excavation hole, 12. Bottom outline, 13. Top outline, 14. Working plane, 15. Terminal, 16. Steel pipe, 17. Copper core insulated wire, 18. Carbon fiber mixed cement grout, 19. Porous steel pipe, 20. Filter pipe, 21. Pebble, 22. Medium and coarse sand, 23. Grouting pipe. Detailed Implementation

[0022] In this embodiment, electroosmosis refers to the phenomenon where water molecules in the soil move towards the negative electrode along with hydrated cations after inserting positive and negative electrodes into the soil and connecting a DC power source. Simultaneously, because clay particles in the soil carry a negative charge, they move towards the anode after being energized; this phenomenon is called electrophoresis. Electroosmosis and electrophoresis are collectively referred to as electroosmosis. Micropiles are small-diameter piles commonly used in geotechnical engineering, typically with a diameter of 100mm-300mm and a large slenderness ratio. They are constructed using a bored pile method, and the pile reinforcement can be steel pipes, reinforcing bars, etc., while the grouting material can be cement mortar or fine aggregate concrete. Micropiles can be used for foundation reinforcement of historical buildings (correction of tilting and settlement, underpinning reinforcement, and reinforcement of defective foundations), foundation pit and slope protection, transmission tower foundations, and construction impact isolation and protection measures.

[0023] Example 1 This embodiment provides a method for correcting and reinforcing the tilt of tall structures using micropiles based on the principle of soil electrokinetics. The structure 1 has a foundation slab at its bottom with an inclination angle of 3. The top contour 12 and bottom contour 13 of the structure are coaxial, and the area of ​​the top contour 12 is smaller than the area of ​​the bottom contour 13. Figure 1 As shown, the correction and reinforcement includes the following steps: Step 1: Before the tilt correction operation, the foundation of structure 1 is pre-reinforced to form the pre-reinforced foundation slab 2. Settlement monitoring points, inclinometers, strain gauges, crack observation devices, etc. are arranged on the structure 1 to be tilted.

[0024] This step can be accomplished using existing technology and will not be described in detail here.

[0025] Step 2: As Figure 2 As shown, according to the design scheme for preventing settlement of the structure, multiple anode micropiles 4 are constructed on the side of the structure with greater settlement, and multiple cathode micropiles 5 are constructed on the side of the structure with less settlement.

[0026] like Figure 3 As shown, the anode micropile 4 is a bored cast-in-place pile, and its construction method is as follows: Drilling is performed on the pre-reinforced foundation slab 2 on the side of the structure with greater settlement, and on the soil beneath it, to form pile holes. Existing technology can be used for drilling, and it will not be described in detail here. The diameter of the holes on the pre-reinforced foundation slab 2 is larger than the diameter of the pile holes.

[0027] A steel pipe 16 is inserted into the pile hole. The steel pipe 16 serves as the reinforcement of the anode micropile 4 and also as the anode electrode. The steel pipe 16 is made of stainless steel.

[0028] After the steel pipe 16 is inserted, the grouting material is injected until the anode micropile is formed. In this embodiment, the grouting material is carbon fiber cement slurry 18, which is prepared by adding carbon fiber to cement. The carbon fiber accounts for 1.5%-2.0% of the total weight of the carbon fiber cement slurry. Those skilled in the art can set it according to actual needs. The cement is silicate cement with a water-cement ratio of no more than 0.55. Those skilled in the art can set the water-cement ratio of the cement according to actual needs. It will not be described in detail here.

[0029] By incorporating carbon fibers into cement, the conductivity of the cement slurry and the conductive contact area between the cement slurry and the electrode can be increased.

[0030] In this embodiment, the pressure during grouting is 0.3MPa-1.0MPa.

[0031] Terminal 15 is pre-welded to the top of the steel pipe for connection to the power supply.

[0032] like Figure 4 As shown, the cathode micropile 5 is a bored cast-in-place pile, and its construction method is as follows: Drilling is performed on the pre-reinforced foundation slab 2 on the side of structure 1 with less settlement, and on the soil beneath it, to form pile holes. The construction method for the pile holes can use existing technology and will not be described in detail here. The diameter of the hole on the pre-reinforced foundation slab 2 is larger than the diameter of the pile hole.

[0033] After the pile hole is formed, a porous steel pipe 19 is inserted into the pile hole as a reinforcement and also as a cathode electrode. The wall of the porous steel pipe 19 has multiple through holes with a diameter of 10 mm and a spacing of 50 mm between adjacent holes.

[0034] Terminal 15 is welded to the top of the porous steel tube 19 for connecting to a power source.

[0035] After the porous steel pipe 19 is inserted, pebbles 21 are filled into the gap between the wall of the porous steel pipe 19 and the surface of the pile hole.

[0036] A filter pipe 20 and a grouting pipe 23 are embedded in a porous steel pipe. The space between the filter pipe 20, the grouting pipe 23 and the porous steel pipe is filled with medium-coarse sand 22. Existing medium-coarse sand can be used for the medium-coarse sand 22, and will not be described in detail here. A water level detection element is pre-installed in the filter pipe 20 to detect the water level. Existing equipment can be used for the water level detection element, and will not be described in detail here.

[0037] Then, grouting material is injected into the pile hole to form a cathode micropile.

[0038] In this embodiment, the grouting material for the cathode micropile 5 is silicate cement with a water-cement ratio of no more than 0.55. Those skilled in the art can set it according to actual needs. The grouting pressure of the grouting material is 0.3MPa-1.0MPa. Those skilled in the art can set it according to actual needs, and it will not be described in detail here.

[0039] Step 3: After the anode micropiles 4 and cathode micropiles 5 are constructed, a working trench 10 is excavated on the side of the structure 1 where the settlement is smaller. The working plane 14 occupied by the working trench 10 is rectangular and its length is greater than the length of the pre-reinforced base plate 2.

[0040] Step 4: Install a power supply near the construction site. In this embodiment, a DC power supply 6 is used. An electrical monitoring device is set up to monitor the voltage, current and other conditions in the circuit in real time. An emergency switch is set up on the power supply circuit 7. The setting of the electrical monitoring device and the emergency switch can be done using existing technology, and will not be described in detail here.

[0041] Step 5: Connect the terminal 15 at the top of the steel pipe 16 of the anode micropile 4 to the positive terminal of the power supply through the copper core insulated wire 17. Connect the terminal at the top of the porous steel pipe 19 of the cathode micropile 5 to the negative terminal of the power supply through the copper core insulated wire 17. Connect the vacuum pump 8 to the filter tubes 20 of multiple cathode micropile 5 through the water supply pipe 9. The vacuum pump 8 can be used to realize the function of pumping groundwater.

[0042] Step 6: The DC power supply 6 is activated, energizing the anode micropile 4 and the cathode micropile 5. When the water level is detected in the filter tube 20, the vacuum pump 8 starts to drain the water. Based on the design tilting amount and tilting rate of the tilt correction scheme, excavation and forced settlement begin. The excavation work is carried out in the working trench. Continuous monitoring is conducted during the tilt correction period, and the settlement caused by drainage promotes the settlement of the side with smaller settlement.

[0043] Step 7: After the structure is tilted back to the predetermined position, the vacuum pump 8 stops draining, and the drainage facilities such as the filter pipe 20, vacuum pump 8, and water pipe 9 are recovered. The excavation hole 11 during the excavation construction is sealed by grouting. Grouting is carried out through the grouting pipe 23 reserved by the cathode micropile 5, and the anode micropile 4 and cathode micropile 5 are sealed. That is, grouting is carried out between the anode micropile 4 and cathode micropile 5 and the hole wall of the pre-reinforced foundation plate 2, so that the anode micropile 4 and cathode micropile 5 are reliably connected to the pre-reinforced foundation plate 2.

[0044] Step 8: Backfill the working trench 10, backfill the ground surface, restore the ground surface, and complete the correction of the structure.

[0045] In the tilt correction method of this embodiment, the anode micropiles arranged on the side of the structure with greater settlement serve as both structural load-bearing piles and discharge electrodes. Carbon fiber-infused cement grout is used to increase the effective conductive contact area of ​​the electrodes, while the porous steel pipe body is made of stainless steel to reduce the problem of anode corrosion. The cathode micropiles arranged on the side of the structure with less settlement, through the porous steel pipe and filter pipe, simultaneously undertake the triple functions of reinforcement, electrode, and drainage, effectively reducing the construction steps for electroosmosis, simplifying the construction process, and eliminating the need for additional electrode installation and dedicated drainage systems, thus saving costs. Furthermore, for tall structures with small foundation areas, the voltage and power consumption required for electroosmosis are lower than for ordinary buildings, resulting in significant economic benefits.

[0046] During the energizing process, negatively charged soil particles move toward the anode micropile and are adsorbed onto the pile-soil interface, effectively densifying and improving the soil around the pile, significantly increasing the side friction resistance of the anode micropile, enhancing the reliability and effectiveness of the settlement prevention and reinforcement, and improving the bearing capacity gain of the micropile by increasing its length. This breaks through the technical bottleneck of the difficulty in improving the bearing capacity of traditional micropiles in this type of stratum.

[0047] A vacuum pump is used to pump water from the filter pipe inside the microcathode pile. The differential settlement caused by the drainage action assists the forced settlement of the excavation method. The combination of excavation and drainage is used to correct the tilt, which overcomes the shortcomings of using electroosmosis technology alone. The tilting trend and rate of the building are easy to control, and the risk is low. Because drainage is used to assist the excavation method, the amount of soil to be excavated is reduced, the construction period is shortened, and the disturbance to sensitive soil foundations is reduced. It is suitable for historical buildings or important structures that are sensitive to disturbance.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for correcting and reinforcing the tilt of tall structures using micropiles based on the principle of soil electrokinetics, characterized in that, Includes the following steps: Anode micropiles are constructed on the side of the structure with greater settlement, and cathode micropiles are constructed on the side with less settlement. Both anode and cathode micropiles contain steel pipes. The steel pipes in the cathode micropiles are porous steel pipes with filter pipes embedded inside. Connect the top of the steel pipe of the anode micropile to the positive terminal of the power supply, and connect the top of the steel pipe of the cathode micropile to the negative terminal; connect the filter tube to the vacuum pump. The power supply provides power to the anode micropiles and cathode micropiles. After the water level is observed in the filter tube, the vacuum pump is started to pump water. At the same time, the soil below the side of the structure with less settlement is excavated until the structure tilts back to the preset position.

2. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 1, characterized in that, Excavate a working trench on the side of the structure with less settlement, and excavate the soil below the side of the structure with less settlement within the working trench.

3. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 1, characterized in that... The anode micropiles are bored cast-in-place piles. The construction method is as follows: first, holes are drilled in the foundation slab of the structure and the soil below to form pile holes. Then, steel pipes are inserted into the pile holes, and the pile holes are grouted to form anode micropiles.

4. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 3, characterized in that... The grouting material for the anode micropiles is carbon fiber cement slurry, which is prepared by adding carbon fiber to cement. The carbon fiber accounts for 1.5%-2% of the mass of the carbon fiber cement slurry, and the cement used is silicate cement with a water-cement ratio of no more than 0.

55.

5. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 3, characterized in that... When injecting grouting material, the injection pressure is 0.3MPa-1.0MPa.

6. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 1, characterized in that... The cathode micropile is a bored cast-in-place pile. The construction method is as follows: First, a hole is drilled in the foundation slab of the structure and the soil below it to form a pile hole. Then, a porous steel pipe is inserted into the pile hole. Pebbles are filled in the gap between the porous steel pipe and the pile hole wall. A filter pipe is embedded in the porous steel pipe. Medium and coarse sand is filled between the filter pipe and the porous steel pipe. Grouting is performed in the pile hole to form a cathode micropile.

7. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 6, characterized in that... During the construction of cathode micropiles, a grouting pipe is embedded in a porous steel pipe before filling with medium-coarse sand. After the structure is corrected, the filter pipe is retrieved, and the grouting pipe is used to grout the pile hole to form a complete pile body.

8. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 6, characterized in that... When grouting cathode micropiles, silicate cement is used as the grouting material, with a water-cement ratio not exceeding 0.

55.

9. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 6, characterized in that... When grouting cathode micropiles, the grouting pressure is 0.3MPa-1.0MPa.

10. The method for correcting and reinforcing tall structures using micropiles based on the principle of soil electrokinetics as described in claim 1, characterized in that, Terminals are welded to the top of the porous steel pipe, and the terminals are connected to the power supply via copper-core insulated wires.

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