Shield segment micro-crack repairing system and method based on multi-modal magnetic field coupling

Abstract

The application discloses a shield segment micro-crack repairing system and method based on multi-modal magnetic field coupling, and belongs to the technical field of tunnel and underground engineering structure maintenance and repair. The system comprises an integrated multi-modal magnetic field rigid repairing head, a magnetic field time sequence controller, a magnetic repairing slurry, a mechanical arm device, a raw material storage device and a grouting device which are integrated on a repairing trolley. The slurry is composed of epoxy resin, micron and nano magnetic particles and the like, and water-swelling polyurethane can be added to realize fast sealing with water. Through the coupling effect of low-frequency oscillation, rotation and high-frequency alternating magnetic field, the shear thinning low-pressure penetration, directional deep transport and exhaust and in-situ magnetic heat rapid curing of the slurry are realized; the mechanical arm and the Halbach permanent magnet array cooperate to form a stable sealed cavity under dry and water-rich leakage working conditions with the cooperation of a flexible sealing gasket; and the application overcomes the problems of traditional grouting, such as difficult penetration, non-dense filling and slow curing, and realizes non-destructive, accurate and fast repair of shield segment micro-cracks.

Description

Technical Field

[0001] This invention relates to the field of tunnel and underground engineering structure maintenance and repair technology, and in particular to a shield tunnel segment microcrack repair system and method based on multimodal magnetic field coupling. Background Technology

[0002] With the rapid advancement of urbanization in my country, the shield tunneling method, with its advantages of high construction efficiency, minimal disturbance to the surrounding environment, and strong geological adaptability, has become the core construction method for underground engineering projects such as subways, cross-river and cross-sea tunnels, and urban underground integrated pipe corridors. Shield tunnel segments, as the prefabricated lining main structure of shield tunnels, are the core barrier ensuring the long-term safety of the tunnel. However, during production, transportation, assembly, construction, and long-term service, they are inevitably affected by factors such as uneven settlement, grouting pressure fluctuations, train cyclic vibration, material shrinkage, and soil erosion, resulting in different types of cracks. Micro-cracks with a width of less than 0.2 mm, although initially having limited impact on the structural bearing capacity, can lead to further damage if not repaired in time. Groundwater and corrosive media such as chloride ions and sulfate ions will continuously seep into the concrete along the cracks, accelerating steel corrosion, concrete neutralization, and structural durability deterioration. In severe cases, this can cause engineering accidents such as segment leakage, joint failure, and structural instability, directly threatening the long-term operational safety of the shield tunnel.

[0003] Currently, conventional repair techniques for cracks in concrete tunnel segments mainly include three categories: surface sealing, pressure grouting, and slotting filling. Among them, pressure grouting is the most widely used mainstream technology in engineering. However, in the scenario of repairing microcracks in shield tunnel segments, existing technologies have core defects that are difficult to overcome: First, the microcrack space is narrow, and the capillary resistance and viscous resistance of the grout are large. Conventional repair materials such as epoxy resin and polyurethane are difficult to penetrate deep into the crack under low pressure conditions. On the other hand, simply increasing the grouting pressure can easily damage the sealing structure of the segment joints, and even cause secondary disasters such as segment misalignment, secondary splitting and propagation of cracks, and surface heave, making it impossible to achieve non-destructive repair of microcracks. Secondly, traditional grouting processes rely on manual experience for control, making it impossible to actively regulate the flow and diffusion range of the grout within the cracks. This easily leads to problems such as premature sealing of crack openings, insufficient deep filling, and internal air blockage forming cavities, making it difficult to achieve dense, full-depth repair of micro-cracks. Thirdly, existing repair materials have inherent limitations. Epoxy resin has excellent bonding properties but high viscosity and poor adaptability to damp interfaces. While polyurethane materials offer fast water-stopping speeds, their mechanical strength after curing is insufficient, failing to balance rapid water-stopping with structural reinforcement. Furthermore, conventional resin systems have long curing cycles at room temperature, making it difficult to meet the efficient construction needs of short-duration maintenance windows in operating tunnels at night. In addition, existing repair devices mostly employ flexible bonding structures to adapt to the curved surfaces of tunnel segments, but such structures often face problems such as insufficient normal clamping force, easy seal failure, and high manufacturing costs in actual engineering. Therefore, there is an urgent need for a complete set of equipment and methods for shield tunnel repair that combines engineering practicality, economic feasibility, and a high degree of integration of multimodal magnetic fields.

[0004] In recent years, magnetic repair slurry and external magnetic field control technology have been widely studied in microfluidics, biomedicine and other fields. There have also been explorations in the industry of using a single static magnetic field to assist the directional flow of slurry and a single magnetic field to achieve material solidification. However, existing technologies still have significant bottlenecks: existing solutions mostly adopt a single static magnetic field or a single-mode magnetic field design. A single static magnetic field can only provide directional attraction and cannot achieve shear thinning of the slurry, leading to difficulties in low-pressure penetration; a single high-frequency magnetic field can only achieve solidification and cannot solve the problem of deep transport; a single rotating magnetic field can only achieve slurry stirring and cannot simultaneously meet the needs of penetration and solidification. Existing technologies cannot simultaneously solve the full-chain technical problems of "difficult low-pressure penetration, uncontrollable deep transport, and low solidification efficiency" in microcrack repair, and have not yet formed an integrated complete repair system suitable for the confined space, curved segments, and complex working conditions of shield tunnels, making it difficult to meet the actual engineering needs of precise, efficient, and non-destructive repair of microcracks in shield tunnel segments. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for repairing microcracks in tunnel lining segments based on multimodal magnetic field coupling, thereby solving the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides a shield tunnel segment microcrack repair system based on multimodal magnetic field coupling, comprising an integrated multimodal magnetic field rigid repair head, a magnetic field timing controller, a repair trolley, a robotic arm device, a raw material storage device, and a grouting device; the integrated multimodal magnetic field rigid repair head is installed at the end of the robotic arm device, the magnetic field timing controller is electrically connected to the integrated multimodal magnetic field rigid repair head, and the grouting device is connected to the raw material storage device and the integrated multimodal magnetic field rigid repair head respectively; the robotic arm device, the magnetic field timing controller, the raw material storage device, and the grouting device are all integrated on the movable repair trolley; The integrated multimodal magnetic field rigid repair head integrates at least a high-frequency induction coil layer, a rotating magnetic field coil layer, and a low-frequency oscillation coil layer from top to bottom. The magnetic field timing controller is used to output drive current to the high-frequency induction coil layer, the rotating magnetic field coil layer and the low-frequency oscillation coil layer in a time-division manner.

[0007] Preferably, the integrated multimodal magnetic field rigid repair head adopts an eight-layer coaxial stacked structure, which, from top to bottom, consists of a mechanical interface layer, a cooling layer, the high-frequency induction coil layer, the rotating magnetic field coil layer, the low-frequency oscillation coil layer, a Halbach permanent magnet array layer, a flexible sealing gasket, and a grouting / venting channel. The front edge of the integrated multimodal magnetic field rigid repair head is provided with at least three laser ranging sensors, and the number of laser ranging sensors can be adjusted based on the size and attitude correction accuracy requirements of the integrated multimodal magnetic field rigid repair head to achieve three-dimensional attitude correction of the repair head, preferably 3-5. Waterproof and insulating encapsulation structures are provided in its electrical connection area, the outer side of each coil layer, and the wire transition area.

[0008] Preferably, the high-frequency induction coil layer is composed of a ferrite core and Litz wire windings, with an output magnetic field frequency of 100kHz-500kHz; the rotating magnetic field coil layer adopts a three-phase stator-type segmented ring winding structure, with an output magnetic field frequency of 1Hz-100Hz; the low-frequency oscillation coil layer is composed of a pair of square Helmholtz coils, with an output magnetic field frequency of 0.1Hz-10Hz; and the Halbach permanent magnet array layer is composed of neodymium iron boron permanent magnets arranged according to the Halbach array rule, with a working side magnetic flux density ≥0.6T.

[0009] Preferably, a composite electromagnetic shielding layer composed of copper foil and ferrite material is provided between each pair of the high-frequency induction coil layer, the rotating magnetic field coil layer, and the low-frequency oscillation coil layer, and a heat insulation layer is provided between the low-frequency oscillation coil layer and the Halbach permanent magnet array layer.

[0010] Preferably, the robotic arm device is equipped with a passive floating ball joint mechanism or an active attitude-adjusting micro electric push rod, which uses a position-based impedance constant force control algorithm to provide normal clamping force, and is superimposed with the normal attraction force generated by the coupling of the Halbach permanent magnet array layer and the steel cage inside the segment to form a stable sealed cavity on the crack surface.

[0011] Preferably, the magnetic repair slurry, by weight, is composed of 100 parts epoxy resin, 50 parts curing agent, 40-50 parts carbonyl iron powder, 40-50 parts superparamagnetic iron oxide, 80-100 parts fly ash, 9-12 parts reactive diluent, 1.5 parts coupling agent, and 1.5-2 parts fumed silica; when used for repair in water-rich leakage environments, the magnetic repair slurry further includes 5-10 parts water-swellable polyurethane prepolymer.

[0012] Preferably, an isolation and sealing structure is provided between the grouting / venting channel, the cooling channel and the electrical channel.

[0013] Preferably, the grouting device includes a grouting pipe and a low-pressure injection device, which are connected to the repair area through the grouting / venting channel on the integrated multimodal magnetic field rigid repair head.

[0014] Preferably, the magnetic field timing controller has a built-in phased timing control module, which outputs driving currents of corresponding frequency, amplitude and phase to the high-frequency induction coil layer, the rotating magnetic field coil layer and the low-frequency oscillation coil layer in a time-division manner; the shield tunnel segment microcrack repair system based on multi-mode magnetic field coupling also includes an insulation monitoring module and a leakage protection module that are signal-connected to the magnetic field timing controller.

[0015] The method for repairing microcracks in tunnel lining segments based on multimodal magnetic field coupling includes the following steps: S1. The repair trolley moves to the tunnel crack area, and the robotic arm moves the integrated multimodal magnetic field rigid repair head to the target crack position. After completing the attitude correction, the flexible sealing gasket is initially attached to the surface of the shield segment. S2. The robotic arm applies a normal clamping force to the integrated multimodal magnetic field rigid repair head, which, together with the auxiliary adsorption force of the Halbach permanent magnet array layer, compresses the flexible sealing gasket to form a locally sealed repair cavity. S3. Mix epoxy resin, curing agent, carbonyl iron powder, superparamagnetic iron oxide, fly ash, reactive diluent, coupling agent and fumed silica in proportion to form a magnetic repair slurry and store it in the raw material storage device. S4. Use a grouting device to inject magnetic repair grout into the locally sealed repair cavity. At the same time, the magnetic field timing controller controls the low-frequency oscillation coil layer to output a low-frequency oscillation magnetic field to reduce the apparent viscosity of the grout and promote grout penetration. S5. When the grout enters the crack, the magnetic field timing controller controls the rotating magnetic field coil layer to output a rotating magnetic field. This magnetic field drives the magnetic repair grout to be transported to the depth of the crack and to expel the gas inside the crack. S6. Stop grouting. The magnetic field timing controller controls the high-frequency induction coil layer to output a high-frequency alternating magnetic field, so that the magnetic repair grout is magnetothermal cured in situ. S7. After curing is complete, the magnetic field timing controller shuts off the magnetic field, releases the normal clamping force applied by the robotic arm device, and retracts the integrated multimodal magnetic field rigid repair head.

[0016] Therefore, the beneficial effects of the shield tunnel segment microcrack repair system and method based on multimodal magnetic field coupling described above are as follows: 1. This invention breaks through the limitations of traditional static magnetic fields or single magnetic fields in underground engineering grouting applications. It adopts an integrated multi-modal magnetic field rigid repair head design, which greatly improves the engineering practicality and economic feasibility compared with flexible structures, while ensuring sufficient normal main clamping force.

[0017] 2. Multimodal magnetic field synergy for non-destructive and efficient repair: This invention achieves low-pressure penetration of grout shear thinning, directional deep transport and degassing, and in-situ magnetothermal rapid curing through the coupling effect of three types of magnetic fields: low-frequency oscillation, rotation, and high-frequency alternation. This solves the core problems of traditional grouting, such as difficult penetration, incomplete filling, and slow curing, in one go. It eliminates the need for high-pressure grouting, thus avoiding secondary structural damage to the tunnel segments from the source and meeting the needs of microcrack repair.

[0018] 3. Synergistic sealing design, adapted to shield tunneling conditions: Through the synergistic effect of the main clamping force of the robotic arm and the auxiliary adsorption force of the Halbach permanent magnet array, combined with the flexible sealing gasket, a stable local sealing repair cavity can be quickly formed on the curved surface of the shield tunnel segment, solving the problems of easy leakage and poor sealing stability of traditional grouting. The whole system is integrated into the repair trolley, which is suitable for mobile operation in the narrow space of the tunnel.

[0019] 4. Precise timing control to improve repair quality: The magnetic field timing controller enables independent timing control of three types of magnetic fields, which can accurately match magnetic field parameters according to the repair stage. At the same time, the interlayer shielding design avoids interference between magnetic fields, enabling active and controllable control of slurry flow and ensuring full-depth and dense repair of microcracks.

[0020] 5. The material system has strong adaptability and covers multiple working conditions: The magnetic repair grout is compounded with dual-scale magnetic particles. Among them, the micron-sized carbonyl iron powder generates periodic magnetic response and local magnetostrictive shearing effect in the low-frequency oscillating magnetic field, thereby destroying the particle arch structure at the crack opening, reducing the apparent viscosity of the grout, and promoting the grout to enter the crack neck. The high-frequency alternating magnetic field excites the nano-sized superparamagnetic iron oxide in the grout to generate a magnetocaloric effect, which makes the grout heat up rapidly and undergo cross-linking and curing. It takes into account both the magnetic response dynamic effect and the magnetocaloric curing effect. The basic formula can meet the repair of microcracks in dry environments. After adding water-swellable polyurethane prepolymer, it can be adapted to the repair of water-rich leakage conditions, achieving rapid water stoppage and structural reinforcement at the same time, with wide engineering applicability.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is an overall architecture diagram of the shield tunnel segment microcrack repair system based on multimodal magnetic field coupling of the present invention; Figure 2 A three-dimensional cross-sectional view and layered structure diagram of an integrated multimodal magnetic field rigid repair head; Figure 3 Diagram showing the connection relationship between the integrated multimodal magnetic field rigid repair head and the robotic arm device; Figure 4 This is a diagram showing the internal structure and coil winding arrangement of a multimode magnetic field generator. Figure 5 A schematic diagram of the microscopic dynamic behavior of magnetic particles in a magnetic repair slurry under a multimodal magnetic field; Figure 6 This is a flowchart of the repair process for microcracks in tunnel lining segments based on multimodal magnetic field coupling.

[0023] Figure Labels 1. Integrated multimodal magnetic field rigid repair head; 1.1 Mechanical interface layer; 1.2 Cooling layer; 1.3 High-frequency induction coil layer; 1.4 Rotating magnetic field coil layer; 1.5 Low-frequency oscillation coil layer; 1.6 Halbach permanent magnet array layer; 1.7 Flexible sealing gasket; 1.8 Grouting / venting channel; 2. Magnetic field timing controller; 3. Magnetic repair slurry; 3.1 Epoxy resin; 3.2 Curing agent; 3.3 Carbonyl iron powder; 3.4 Superparamagnetic iron(III) oxide; 3.5 Fly ash; 3.6 Reactive diluent; 3.7 Coupling agent; 3.8 Fumed silica; 3.9 Water-swellable polyurethane prepolymer; 4. Repair trolley; 5. Robotic arm device; 6. Raw material storage device; 7. Grouting device. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0025] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] like Figures 1-6 As shown, this invention provides a system and method for repairing microcracks in tunnel lining segments based on multimodal magnetic field coupling. The system includes an integrated multimodal magnetic field rigid repair head 1, a magnetic field timing controller 2, magnetic repair grout 3, a repair trolley 4, a robotic arm device 5, a raw material storage device 6, and a grouting device 7. The integrated multimodal magnetic field rigid repair head 1 is installed at the end of the robotic arm device 5. The magnetic field timing controller 2 is electrically connected to the integrated multimodal magnetic field rigid repair head 1. The grouting device 7 is connected to both the raw material storage device 6 and the integrated multimodal magnetic field rigid repair head 1. The magnetic field rigid repair head 1, robotic arm device 5, magnetic field timing controller 2, raw material storage device 6, and grouting device 7 are all integrated on the repair trolley 4, enabling mobile operation in the confined space of the shield tunnel. Among them, the integrated multimodal magnetic field rigid repair head 1 integrates at least a high-frequency induction coil layer 1.3, a rotating magnetic field coil layer 1.4, and a low-frequency oscillation coil layer 1.5 from top to bottom. The magnetic field timing controller 2 is used to output drive current to the high-frequency induction coil layer 1.3, the rotating magnetic field coil layer 1.4, and the low-frequency oscillation coil layer 1.5 in a time-division manner.

[0028] Specifically, the integrated multimodal magnetic field rigid repair head 1 adopts an eight-layer coaxial stacked structure, consisting of, from top to bottom, a mechanical interface layer 1.1, a cooling layer 1.2, a high-frequency induction coil layer 1.3, a rotating magnetic field coil layer 1.4, a low-frequency oscillation coil layer 1.5, a Halbach permanent magnet array layer 1.6, a flexible sealing gasket 1.7, and a grouting / venting channel 1.8; the mechanical interface layer 1.1 is connected to the end of the robotic arm device 5 and integrates electrical channels, cooling medium channels, and fluid channels; the cooling layer 1.2 uses micro-water cooling channels or micro-air cooling channels embedded in an aluminum alloy substrate for active heat dissipation and heat removal of the system; the flexible sealing gasket 1... .7 The flexible silicone or rubber material with a thickness of 5–10 mm is used, and the edge is provided with a labyrinth groove to prevent slurry leakage. It can compensate for the surface curvature, roughness and local misalignment of the tunnel segment. The front edge of the integrated multimodal magnetic field rigid repair head 1 is provided with 3-5 laser ranging sensors. Through closed-loop detection of the surface curvature of the shield tunnel segment, combined with the passive floating ball joint mechanism or active attitude adjustment micro electric push rod on the robotic arm device 5, the attitude adaptive adjustment and uniform force of the concrete tunnel segment with a curvature radius ≥2m can be achieved. Its electrical connection area, the outer side of each coil layer and the conductor transition part are all provided with a waterproof insulation encapsulation structure to prevent water leakage from entering the electrical cavity along the structural gaps.

[0029] The high-frequency induction coil layer 1.3 consists of a ferrite core and Litz wire windings, with an output magnetic field frequency of 100kHz-500kHz, used to excite the nano-scale superparamagnetic iron(III) oxide 3.4 in the slurry to generate a magnetocaloric effect; the rotating magnetic field coil layer 1.4 adopts a three-phase stator-type segmented ring winding structure, with an output magnetic field frequency of 1Hz-100Hz, used to drive the slurry to actively transport to the depth of the crack and promote gas discharge; the low-frequency oscillation coil layer 1.5 consists of a pair of square Helmholtz coils, with an output magnetic field frequency of 0.1Hz-10Hz, used to drive the micron-scale carbonyl iron powder 3.3 in the slurry to generate a periodic response, destroy the particle arch structure at the crack opening and reduce the apparent viscosity of the slurry; the Halbach permanent magnet array layer 1.6 consists of neodymium iron boron permanent magnets arranged according to the Halbach array rule, with a working side magnetic flux density ≥0.6T, which can provide auxiliary adsorption force, reduce the continuous pressing load of the robotic arm device 5 and improve sealing stability.

[0030] A composite electromagnetic shielding layer made of copper foil and ferrite material is provided between each pair of the high-frequency induction coil layer 1.3, the rotating magnetic field coil layer 1.4, and the low-frequency oscillation coil layer 1.5. The shielding layer uses the principle of eddy current reflection and high permeability absorption to suppress parasitic coupling and interference between high, medium and low frequency electromagnetic fields. A heat insulation layer is provided between the low-frequency oscillation coil layer 1.5 and the Halbach permanent magnet array layer 1.6 to prevent high-frequency magnetothermal effects on the performance of the permanent magnet.

[0031] The robotic arm device 5 is equipped with a passive floating ball joint mechanism or an active attitude-adjusting micro electric push rod. It uses a position-based impedance constant force control algorithm to provide the normal main clamping force, which is superimposed with the normal auxiliary adsorption force generated by the coupling of the Halbach permanent magnet array layer 1.6 and the steel cage inside the segment to form a stable sealed cavity on the crack surface. This overcomes the reverse pressure of the grout and the groundwater pressure during the grouting process, and can achieve reliable sealing without excessive mechanical clamping force, thus avoiding additional damage to the segment.

[0032] The magnetic repair slurry 3, by weight, is composed of 100 parts epoxy resin 3.1, 50 parts curing agent 3.2, 40-50 parts micron-sized carbonyl iron powder 3.3, 40-50 parts nano-sized superparamagnetic iron tetroxide 3.4, 80-100 parts fly ash 3.5, 9-12 parts reactive diluent 3.6, 1.5 parts coupling agent 3.7, and 1.5-2 parts fumed silica 3.8. Among these, the micron-sized carbonyl iron powder 3.3 experiences a large magnetic torque under a rotating magnetic field and is primarily responsible for generating pumping and shearing forces. Effect; Nanoscale superparamagnetic iron oxide 3.4 has no hysteresis phenomenon, which can not only fill the tiny pores that micron particles cannot enter, but more importantly, it generates strong relaxation loss under high frequency alternating magnetic field, serving as an efficient internal heat source for "magnetothermal curing"; When used for repair in water-rich leakage environments, the magnetic repair slurry 3 also includes 5-10 parts of water-swellable polyurethane prepolymer 3.9, which reacts with water to generate carbon dioxide gas, causing the slurry volume to expand. It achieves rapid sealing with water by relying on the synergistic effect of chemical foaming expansion pressure and high frequency magnetothermal curing.

[0033] The grouting / venting channel 1.8, the cooling channel, and the electrical channel are equipped with an isolation and sealing structure to prevent grout, cooling medium, or groundwater from entering the electrical cavity and to ensure the electrical safety of the system.

[0034] The grouting device 7 includes a grouting pipe and a low-pressure injection device, which is connected to the repair area through the grouting / venting channel 1.8 on the repair head; the grouting / venting channel 1.8 is located on the side or inner edge of the repair head and is used to inject the magnetic repair grout 3 and expel the gas inside the crack.

[0035] The magnetic field timing controller 2 has a built-in phased timing control module. This module can output driving currents of corresponding frequency, amplitude and phase to the high-frequency induction coil layer 1.3, rotating magnetic field coil layer 1.4 and low-frequency oscillation coil layer 1.5 according to the three core stages of crack repair: grout penetration, deep transport and in-situ solidification. This enables independent time-sequential control and interference-free coupling of the three types of magnetic fields. The system is also equipped with an insulation monitoring module and a leakage protection module connected to the magnetic field timing controller 2. These modules are used to monitor the insulation resistance, working current, leakage current to ground and internal water ingress status of the repair head in real time. When insulation abnormality, leakage current exceeding the limit or internal water ingress is detected, the magnetic field timing controller 2 cuts off the power supply output of the corresponding coil layer or all coil layers to ensure operational safety.

[0036] A method for repairing microcracks in tunnel lining segments based on multimodal magnetic field coupling is described in Example 1, which involves repairing longitudinal microcracks in the arch of a subway shield tunnel segment. The method includes: S1, moving a repair trolley to the crack area in the tunnel, and using a robotic arm to move an integrated multimodal magnetic field rigid repair head to the target crack location. An attitude adjustment mechanism corrects the repair head's posture, ensuring initial contact between the flexible sealing gasket and the shield segment surface. This guarantees that the maximum chord height error between the repair head's working surface and the segment's curved surface is within the effective compression compensation range of the flexible sealing gasket. The attitude correction formula is: ; in, To correct the maximum chord height error between the working face and the curved surface of the tunnel segment; To repair the effective contact width of the head; The radius of curvature of the shield tunnel segment; to ensure the initial fit of the flexible sealing gasket, the following should be met: ; in, This is the effective compression compensation amount for the flexible sealing gasket; This includes additional unevenness caused by surface roughness, local misalignment, and construction errors of the tunnel segments. By positioning and adjusting the robotic arm, the flexible sealing gasket establishes uniform initial contact with the tunnel segment surface before compression, providing a posture basis for subsequent compression and sealing.

[0037] S2. The robotic arm applies a normal clamping force to the integrated multi-modal magnetic field rigid repair head. Combined with the auxiliary adsorption force of the Halbach permanent magnet array layer, this compresses the flexible sealing gasket to form a locally sealed repair cavity. The total normal clamping force is the sum of the main clamping force applied by the robotic arm and the auxiliary adsorption force provided by the Halbach permanent magnet array. This effectively overcomes grouting reaction force and groundwater pressure, reduces the continuous clamping load on the robotic arm, and improves sealing stability. The total normal clamping force of the repair head acting on the segment surface... Represented as: ; in, This is the total normal clamping force; The normal clamping force applied to the robotic arm; The auxiliary adsorption force provided to the Halbach permanent magnet array. If the effective sealing contact area is... Then the average sealing pressure for: ; To prevent grout leakage or cavity instability during grouting, the following conditions must be met: ; in, For safety factor; This refers to the grouting pressure. This represents the groundwater pressure or reverse seepage pressure within the fracture. The equivalent magnetic pressure generated at the working face by the Halbach permanent magnet array. Approximately expressed as: ; Corresponding auxiliary adsorption force for: ; in, The working side magnetic flux density of the Halbach permanent magnet array; Permeability of free space; The effective magnetic field area; The correction factor takes into account the thickness of the concrete cover, the distribution of reinforcing bars, and the influence of air gaps. In this process, the robotic arm provides the main sealing force, while the Halbach permanent magnet array only provides auxiliary adsorption force. The two work together to form a stable local sealing and repair cavity.

[0038] S3. Mix epoxy resin, curing agent, carbonyl iron powder, superparamagnetic iron oxide, fly ash, reactive diluent, coupling agent and fumed silica in proportion to form a magnetic repair slurry and store it in the raw material storage device. S4. Magnetic repair grout is injected under low pressure into the locally sealed repair cavity through a grouting device. Simultaneously, a magnetic field timing controller controls the low-frequency oscillation coil layer to output a low-frequency oscillating magnetic field, driving the micron-sized carbonyl iron powder in the grout to generate a periodic magnetic response and local magnetostrictive shearing effect. This disrupts the particle arch structure at the crack opening, reduces the apparent viscosity of the grout, and promotes the grout's entry into the crack neck. At this stage, the nano-sized superparamagnetic iron oxide can generate a synergistic magnetic response with the external field, reserving an internal heat source for rapid magnetothermal solidification under the subsequent high-frequency alternating magnetic field. Under the action of the low-frequency oscillating magnetic field, the micron-sized carbonyl iron powder experiences an alternating magnetic torque. Driven by this, it produces reciprocating deflection. Represented as: ; in, The particle volume; It is the magnetization intensity vector; The applied magnetic field strength is used. Micron-sized particles are oscillated within the confined crack space, which not only disrupts the arching effect between particles but also transforms into a strong local shear rate through hydrodynamic coupling, thereby triggering the non-Newtonian fluid shear thinning characteristics of the slurry and significantly reducing the apparent viscosity.

[0039] S5. After the grout enters the crack, the magnetic field timing controller controls the rotating magnetic field coil layer to output a rotating magnetic field, driving the micron-sized carbonyl iron powder in the grout to generate spin and local fluid disturbance; simultaneously, a traveling wave component drag force is generated, causing the grout to be actively transported to the depth of the crack, and the gas inside the crack is discharged through the exhaust channel, thereby improving the compactness of the crack filling and avoiding the formation of internal cavities. The three-phase winding not only generates a rotating field in the central region to drive the particle spin and form a micro-pump, but the gradient field formed by its natural decay along the direction of the crack depth (Z-axis) also applies Kelvin attraction, i.e., gradient attraction, to the magnetic particles. Represented as: ; Simultaneously, due to the boundary effects and phase sequence switching of the winding, an asynchronous traveling wave component is generated along the Z-axis of the magnetic field. This is achieved by utilizing the magnetic relaxation hysteresis effect of magnetic particles in viscous fluids (relaxation time is...). The traveling wave field will generate a time-averaged drag driving force on the grout along the crack depth direction, i.e., traveling wave thrust. Represented as: ; Under the combined action of the gradient attraction and the traveling wave thrust, the grout overcomes the capillary and viscous resistance of the microcracks, achieving reverse active filling.

[0040] S6. Once the grout filling reaches the predetermined level, grouting is stopped. The magnetic field timing controller controls the high-frequency induction coil layer to output a high-frequency alternating magnetic field, exciting the nano-sized superparamagnetic iron oxide in the grout to generate a magnetocaloric effect, causing the grout to rapidly heat up and undergo cross-linking and solidification. During this period, the water-cooling channels of the cooling layer continue to operate, ensuring that the temperature of the upper coil and adjacent structures does not exceed 80℃. The nano-sized superparamagnetic particles rapidly convert electromagnetic energy into thermal energy through Néel relaxation and Brownian relaxation in the high-frequency alternating magnetic field. As the grout temperature... The increase in the crosslinking rate constant of the epoxy resin system, according to the Arrhenius equation. It increases exponentially, which is represented as: ; in, Prefix factor; It is the activation energy of the reaction; The constant is the ideal gas constant. This endogenous heating mechanism enables the slurry to overcome the time bottleneck of room temperature curing and achieve rapid enhancement within an extremely short window period.

[0041] S7. After curing, the magnetic field timing controller shuts off the magnetic field, releases the normal clamping force applied by the robotic arm, and the robotic arm retracts the integrated multimodal magnetic field rigid repair head to complete the microcrack repair.

[0042] Example 2 describes the repair of microcracks and joints in shield tunnel segments under water-rich seepage conditions. This system is also applicable, with slight adjustments to the process. The adjusted steps include: In step S2, under water-rich seepage conditions, the robotic arm applies a normal clamping force to the integrated multimodal magnetic field rigid repair head to compress the flexible sealing gasket and expel the free water film on the joint surface. Simultaneously, the Halbach permanent magnet array couples with the internal steel reinforcement cage of the segment, providing auxiliary normal adsorption force. The combined action of the main clamping force of the robotic arm and the auxiliary adsorption force of the Halbach permanent magnet array allows the repair head to form a stable local sealed repair cavity at the water-rich seepage interface, thereby resisting the seepage water pressure inside the joint and reducing the risk of grout leakage during the grouting process. Under water-rich seepage conditions, the total normal clamping force remains unchanged; if the effective sealing contact area is... The average sealing pressure, the equivalent magnetic pressure generated by the Halbach permanent magnet array on the working surface, and the corresponding auxiliary adsorption force are respectively: ; ; ; in, The correction factor is used to account for the thickness of the concrete cover, the distribution of reinforcing bars, and the influence of air gaps.

[0043] The specific reasons for adjusting S2 are as follows: 1. The lubrication and isolation effect of the water film: In water-rich seepage environments, the joint surface is usually covered with a continuous or intermittent water film. This water film weakens the direct contact between the repair head and the concrete surface, and is prone to forming leakage channels under the action of grouting pressure and groundwater reverse pressure. If the local sealing pressure is insufficient, the water interface will become unstable, leading to grout backflow, leakage, or even failure of the local sealing cavity. Therefore, under this condition, it is difficult to form a stable seal by relying solely on the passive adhesion of the flexible sealing gasket. Sufficient normal pressure must be provided by the main clamping force of the robotic arm and the auxiliary adsorption force of the Halbach permanent magnet array to displace free water at the interface and maintain the stability of the seal. 2. The magnetic flux focusing effect of the Halbach array: In order to improve the adhesion and sealing ability of the repair head at the water interface without significantly increasing the mechanical clamping load, the system adopts a Halbach permanent magnet array. The Halbach permanent magnet array is arranged in a specific magnetization direction, which significantly enhances the magnetic flux density on the working side, while the magnetic field on the back side is relatively weakened, thereby forming a higher local magnetic field strength and magnetic field gradient on the side closer to the concrete segment. After the enhanced magnetic field couples with the internal steel reinforcement cage of the tunnel segment, it can generate a higher auxiliary adsorption force, improving the interface sealing reliability of the repair head in a water-rich leakage environment. 3. Water-bearing sealing mechanism: In this invention, the sealing in a water-rich leakage environment does not rely solely on magnetic attraction to displace the water film, but rather on the synergistic effect of "mechanical clamping - auxiliary magnetic attraction - flexible sealing gasket". The robotic arm provides the main clamping action, the Halbach permanent magnet array provides continuous auxiliary adsorption action, and the flexible sealing gasket compensates for the surface roughness, local misalignment, and unevenness of the water-bearing interface in the tunnel segment joint area through elastic deformation, thereby constructing a local sealing repair cavity that can resist groundwater pressure and grouting back pressure. 4. Waterproof insulation and leakage protection measures: Since this embodiment is applied to a water-rich leakage environment, before the repair operation, the electrical insulation and sealing status of the integrated multi-modal magnetic field rigid repair head are first checked. Waterproof and insulating encapsulation structures are installed on the mechanical interface layer, electrical connection area, outer sides of each coil layer, and conductor transition areas. These structures can be formed using epoxy potting layer, polyurethane insulation layer, silicone rubber sealing layer, fluororubber sealing ring, or combinations thereof, to prevent water leakage from entering the high-frequency induction coil layer, rotating magnetic field coil layer, and low-frequency oscillation coil layer through structural gaps, cable interfaces, or connection channels. Isolation and sealing structures are installed between the grouting channel, exhaust channel, cooling channel, and electrical channel to prevent grout, water, or cooling media from entering the electrical cavity.Meanwhile, the system is equipped with an insulation monitoring module and a leakage protection module to monitor the insulation resistance of the repair head, the coil operating current, the leakage current to ground of the casing, and the internal water ingress status in real time. When the insulation resistance is detected to be lower than the set threshold, the leakage current exceeds the set value, or an abnormal water ingress signal appears inside the repair head, the magnetic field timing controller immediately cuts off the power supply output of the corresponding coil layer or all coil layers and issues an alarm signal to ensure the electrical safety and system stability of the magnetic field loading process in a water-rich leakage environment. Furthermore, during the repair process in a water-rich leakage environment, the low-frequency oscillating magnetic field, rotating magnetic field, and high-frequency alternating magnetic field are preferably loaded in a phased, intermittent, or sequential controlled manner. The magnetic field output at each stage is carried out under waterproof insulation encapsulation and leakage protection monitoring conditions, thereby reducing the risk of electrical breakdown, leakage, and short circuit in a water-rich leakage environment and ensuring the safe and reliable repair process of the joint leakage.

[0044] In S5, the inward pumping force (volume force) generated by the rotating magnetic field overcomes the reverse hydrostatic pressure of the groundwater, achieving reverse grouting and pushing the grout into the seepage channel. The specific reasons for adjusting S5 are: 1. In microcrack repair, the greatest resistance comes from the reverse pressure gradient: For dry cracks, capillary suction can assist in grout intake, and the resistance is mainly air resistance. However, in water-rich seepage cracks, the cracks are filled with groundwater, and the grout must overcome the groundwater pressure to enter the crack. Fluid resistance, the relationship of which can be expressed as: ; Traditional oscillating magnetic fields primarily function as "shear thinning" (reducing viscosity). While they can disrupt the particle arching effect, they cannot provide a continuous, directional macroscopic pressure gradient. In water-rich seepage environments, simply reducing viscosity will cause the grout to be pushed back by groundwater. 2. Rotating magnetic field-induced spin fluid pumping: To obtain significant driving force without increasing external mechanical grouting pressure, the system utilizes a rotating magnetic field to generate volume forces within the fluid, including: the spin and revolution of magnetic particles: When a rotating magnetic field is applied, ferromagnetic particles (carbonyl iron powder) in the fluid experience a magnetic torque. The action causes high-speed rotation, which is represented as: ; The rotation of microparticles, through fluid viscosity coupling, drives the surrounding fluid to rotate, forming countless microscopic eddies. Macroscopic pumping effect: According to ferrohydrodynamics, this microscopic spin macroscopically transforms into a traveling wave driving force along the direction of magnetic field propagation. This driving force acts on every magnetic particle inside the slurry, preventing excessive pressure at the crack opening while maintaining strong driving potential energy deep within the crack. Specifically, the rotating magnetic field is usually accompanied by a traveling wave component, which can drag magnetic particles deeper into the crack. Centrifugal exhaust and thrust: The rotating magnetic field also generates a centrifugal effect. Because the density of the magnetic repair slurry is much greater than that of water and air bubbles, under the action of the rotating centrifugal force field, the slurry is thrown towards the crack wall and deeper into the crack, while water and air bubbles are squeezed towards the center of rotation and discharged outwards, effectively replacing the water within the crack.

[0045] Simultaneously, the materials were adjusted. Specifically, a water-swellable polyurethane prepolymer component was added to the magnetic repair grout. Combined with magnetothermal curing, this accelerates the foaming and expansion of polyurethane while sealing the leakage channels, achieving a dual water-stopping effect of "chemical grouting + physical expansion." The specific reasons for the adjustment are: 1. Introduction of polyurethane prepolymer and magnetothermal synergy: To adapt to water-rich leakage environments, the material system was adjusted to an "epoxy-polyurethane-magnetic particle" composite system. The polyurethane prepolymer contains isocyanate groups (-NCO). When it comes into contact with water in the crack, the following chemical reaction occurs: ; The carbon dioxide gas generated by the reaction causes the grout volume to expand. The expansion pressure generated can actively compress the crack walls, sealing the micropores and achieving physical water stoppage. 2. Accelerated kinetics of magnetothermal curing: Although polyurethane prepolymer reacts with water, the reaction rate may be slow at low groundwater temperatures (usually 10-15℃), still posing a risk of passive water erosion. In this case, the system uses a high-frequency alternating magnetic field to excite superparamagnetic iron oxide to generate heat. According to the Arrhenius equation, the reaction rate constant... With temperature The process is exponential, with polyurethane foam responsible for rapid water sealing (physical expansion and extrusion), and epoxy resin responsible for subsequent high-strength bonding (chemical grouting). Both processes are completed simultaneously under the action of magnetothermal.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A shield tunnel segment microcrack repair system based on multimodal magnetic field coupling, characterized in that: The device includes an integrated multimodal magnetic field rigid repair head, a magnetic field timing controller, a repair trolley, a robotic arm device, a raw material storage device, and a grouting device. The integrated multimodal magnetic field rigid repair head is installed at the end of the robotic arm device. The magnetic field timing controller is electrically connected to the integrated multimodal magnetic field rigid repair head. The grouting device is connected to both the raw material storage device and the integrated multimodal magnetic field rigid repair head. The robotic arm device, the magnetic field timing controller, the raw material storage device, and the grouting device are all integrated on the movable repair trolley. The integrated multimodal magnetic field rigid repair head integrates at least a high-frequency induction coil layer, a rotating magnetic field coil layer, and a low-frequency oscillation coil layer from top to bottom. The magnetic field timing controller is used to output drive current to the high-frequency induction coil layer, the rotating magnetic field coil layer and the low-frequency oscillation coil layer in a time-division manner.

2. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 1, characterized in that: The integrated multimodal magnetic field rigid repair head adopts an eight-layer coaxial stacked structure, consisting of a mechanical interface layer, a cooling layer, a high-frequency induction coil layer, a rotating magnetic field coil layer, a low-frequency oscillation coil layer, a Halbach permanent magnet array layer, a flexible sealing gasket, and a grouting / venting channel from top to bottom. The front edge of the integrated multimodal magnetic field rigid repair head is equipped with at least three laser ranging sensors, and the number of laser ranging sensors can be adjusted based on the size and attitude correction accuracy requirements of the integrated multimodal magnetic field rigid repair head to achieve three-dimensional attitude correction of the repair head; preferably, 3-5 sensors are used. Waterproof and insulating encapsulation structures are provided in the electrical connection area, on the outer side of each coil layer, and at the wire transition points.

3. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 2, characterized in that: The high-frequency induction coil layer is composed of a ferrite core and Litz wire windings, with an output magnetic field frequency of 100kHz-500kHz; the rotating magnetic field coil layer adopts a three-phase stator-type segmented ring winding structure, with an output magnetic field frequency of 1Hz-100Hz; the low-frequency oscillation coil layer is composed of a pair of square Helmholtz coils, with an output magnetic field frequency of 0.1Hz-10Hz; the Halbach permanent magnet array layer is composed of neodymium iron boron permanent magnets arranged according to the Halbach array rule, with a working side magnetic flux density ≥0.6T.

4. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 3, characterized in that: Each of the high-frequency induction coil layer, the rotating magnetic field coil layer, and the low-frequency oscillation coil layer is provided with a composite electromagnetic shielding layer composed of copper foil and ferrite material, and a heat insulation layer is provided between the low-frequency oscillation coil layer and the Halbach permanent magnet array layer.

5. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 2, characterized in that: The robotic arm device is equipped with a passive floating ball joint mechanism or an active attitude-adjusting micro electric push rod. It uses a position-based impedance constant force control algorithm to provide normal clamping force, which is superimposed with the normal attraction force generated by the coupling of the Halbach permanent magnet array layer and the steel cage inside the segment, forming a stable sealed cavity on the crack surface.

6. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 1, characterized in that: The magnetic repair slurry, by weight, is composed of 100 parts epoxy resin, 50 parts curing agent, 40-50 parts carbonyl iron powder (micron-sized), 40-50 parts superparamagnetic iron oxide (nano-sized), 80-100 parts fly ash, 9-12 parts reactive diluent, 1.5 parts coupling agent, and 1.5-2 parts fumed silica. When used for repair in water-rich leakage environments, the magnetic repair slurry also includes 5-10 parts water-swellable polyurethane prepolymer.

7. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 2, characterized in that: An isolation and sealing structure is provided between the grouting / venting channel, the cooling channel and the electrical channel.

8. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 1, characterized in that: The grouting device includes a grouting pipe and a low-pressure injection device, which are connected to the repair area through the grouting / venting channel on the integrated multimodal magnetic field rigid repair head.

9. The shield tunnel segment microcrack repair system based on multimodal magnetic field coupling according to claim 2, characterized in that: The magnetic field timing controller has a built-in phased timing control module, which outputs driving currents of corresponding frequency, amplitude and phase to the high-frequency induction coil layer, the rotating magnetic field coil layer and the low-frequency oscillation coil layer in a time-division manner. The shield tunnel segment microcrack repair system based on multi-mode magnetic field coupling also includes an insulation monitoring module and a leakage protection module that are connected to the magnetic field timing controller.

10. The method for repairing microcracks in tunnel lining segments based on multimodal magnetic field coupling according to any one of claims 1-9, characterized in that, Includes the following steps: S1. The repair trolley moves to the tunnel crack area, and the robotic arm moves the integrated multimodal magnetic field rigid repair head to the target crack position. After completing the attitude correction, the flexible sealing gasket is initially attached to the surface of the shield segment. S2. The robotic arm applies a normal clamping force to the integrated multimodal magnetic field rigid repair head, which, together with the auxiliary adsorption force of the Halbach permanent magnet array layer, compresses the flexible sealing gasket to form a locally sealed repair cavity. S3. Mix epoxy resin, curing agent, carbonyl iron powder, superparamagnetic iron oxide, fly ash, reactive diluent, coupling agent and fumed silica in proportion to form a magnetic repair slurry and store it in the raw material storage device. S4. Use a grouting device to inject magnetic repair grout into the locally sealed repair cavity. At the same time, the magnetic field timing controller controls the low-frequency oscillation coil layer to output a low-frequency oscillation magnetic field to reduce the apparent viscosity of the grout and promote grout penetration. S5. When the grout enters the crack, the magnetic field timing controller controls the rotating magnetic field coil layer to output a rotating magnetic field. This magnetic field drives the magnetic repair grout to be transported to the depth of the crack and to expel the gas inside the crack. S6. Stop grouting. The magnetic field timing controller controls the high-frequency induction coil layer to output a high-frequency alternating magnetic field, so that the magnetic repair grout is magnetothermal cured in situ. S7. After curing is complete, the magnetic field timing controller shuts off the magnetic field, releases the normal clamping force applied by the robotic arm device, and retracts the integrated multimodal magnetic field rigid repair head.

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