Reinforced concrete synchronous 3D printing lining device and method for TBM

Abstract

The invention discloses a reinforced concrete synchronous 3D printing lining device and method for a TBM, and belongs to the field of additive manufacturing. Comprising a construction rail car, a laser radar, a concrete 3D printing module, a steel bar laser printing module and a control module. The control module constructs a lining three-dimensional model according to tunnel morphology data scanned by the laser radar, extracts a main stress trace through finite element analysis, and generates a steel bar arrangement path and a concrete printing track with stress steering as a principle; the steel bar laser printing module and the concrete 3D printing module synchronously print along the path and the track respectively, and the steel bar layer is controlled to be higher than the concrete layer; and the laser power and the wire feeding speed of the steel bar laser printing module are dynamically adjusted based on monitoring information obtained by the thermodynamic camera, and the temperature fluctuation is controlled within the preset deviation. The system can realize synchronous additive forming of reinforced concrete in a TBM construction environment, and has the characteristics of high automation, high construction flexibility and capability of monitoring the whole process.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing, and in particular relates to a device and method for simultaneous 3D printing of reinforced concrete lining for TBM. Background Technology

[0002] Lining is a permanent support structure constructed along the perimeter of a tunnel using reinforced concrete and other materials to prevent deformation or collapse of the surrounding rock during underground construction. Because plain concrete is prone to cracking and has insufficient flexural strength, steel reinforcement is usually introduced to enhance its mechanical properties. However, traditional reinforced concrete lining still mainly employs a construction method combining precast steel cages with on-site casting, requiring multiple stages such as manufacturing, transportation, hoisting, and assembly. This results in problems such as long construction cycles, high reliance on manual labor, and significant costs and risks.

[0003] To optimize construction processes, 3D-printed concrete technology has been gradually introduced into engineering projects in recent years. By digitally reconstructing tunnel cross-sections and planning printing paths, in-situ fabrication of the lining is achieved, significantly shortening the construction cycle. Meanwhile, metal additive manufacturing technologies, such as laser cladding, have been applied in fields like structural repair due to their high efficiency and precision. Introducing these technologies into tunnel construction allows for simultaneous in-situ forming of reinforcing steel bars while concrete is being printed, offering potential advantages such as flexible adaptation to stress paths, reduced prefabrication steps, and increased automation.

[0004] However, in existing tunnel lining construction, traditional rebar placement methods mainly rely on precast rebar cages or on-site binding and hoisting. This method is cumbersome and usually requires off-site processing, transportation to the construction site, and installation, which not only increases the construction cycle but also places higher demands on site organization, hindering the integration of automated and digital construction systems. Furthermore, traditional rebar laying strategies are often disconnected from concrete pouring during construction, making synchronous construction impossible. The laying paths are mostly regular mesh patterns or arranged along circumferential / longitudinal directions, making it difficult to achieve heterogeneous, variable-density, and customized rebar distribution based on actual stress conditions, and lacking flexibility and topology optimization possibilities. This "rebar first, concrete later" process disrupts the collaborative work between rebar and concrete, limiting the integrity and construction adaptability of the lining structure. Therefore, there is an urgent need to develop a synchronous rebar and concrete printing method to overcome the limitations of precasting and phased construction, enabling dynamic and adaptable rebar laying while the lining is being formed, thereby improving the level of construction integration and intelligence. Summary of the Invention

[0005] To address the key issues in existing concrete 3D printing processes, such as the difficulty in achieving synchronous reinforcement placement, limited structural performance, and insufficient automation due to harsh construction environments, this invention proposes a device and method for synchronous 3D printing of reinforced concrete linings for TBM (Tunnel Boring Machine). This device enables synchronous additive molding of reinforced concrete in the TBM construction environment and features high automation, strong structural flexibility, and full-process monitoring.

[0006] The technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention proposes a reinforced concrete synchronous 3D printing lining device for TBM, including a construction track vehicle, a lidar, a concrete 3D printing module, a rebar laser printing module, and a control module.

[0008] The construction railcar moves along the tunnel axis via the construction rail inside the tunnel, and the lidar is fixed on the construction railcar to scan the tunnel shape; the concrete 3D printing module and the steel bar laser printing module are respectively installed on the construction railcar by an independent robotic arm, and the steel bar laser printing module is equipped with a thermodynamic camera.

[0009] The control module is used to construct a three-dimensional model of the lining based on the tunnel topography data scanned by lidar, and extract the principal stress trajectories through finite element analysis to generate a steel reinforcement layout path and a concrete printing trajectory based on stress guidance. The steel reinforcement laser printing module and the concrete 3D printing module print synchronously along the steel reinforcement layout path and the concrete printing trajectory, respectively, and control the steel reinforcement layer height to be higher than the concrete layer. The thermodynamic camera works in conjunction with the control module to dynamically adjust the laser power and wire feeding speed of the steel reinforcement laser printing module, and control the temperature fluctuation of the laser processing area within a preset deviation.

[0010] Preferably, the concrete 3D printing module includes a stepper motor, a hopper, and a spiral extruder. The stepper motor drives the spiral extruder to rotate inside the hopper via a rigid coupling. A feeding interface is provided on the side wall of the hopper, and a nozzle is connected to the bottom of the hopper. A wall scraper is welded onto the spiral extruder to scrape off the concrete adhering to the hopper wall during rotation.

[0011] Preferably, the rebar laser printing module includes a laser processing head, a heat dissipation device, a wire feeding mechanism, and a thermodynamic camera; the laser processing head and the heat dissipation device are fixed by a connecting device; the wire feeding mechanism is hinged to the connecting device, includes a wire feeding inlet and a wire outlet, and the relative position of the wire feeding inlet and the laser processing head is adjustable; the thermodynamic camera is fixed to the side of the laser processing head.

[0012] Secondly, this invention proposes a printing method for a reinforced concrete synchronous 3D printing lining device for TBM, comprising the following steps:

[0013] Step 1: The construction track vehicle moves along the construction track inside the tunnel, driving the lidar fixed on it to scan the tunnel cross section, obtain morphological data and construct a three-dimensional model of the lining.

[0014] Step 2: The control module performs finite element mechanical analysis based on the lining 3D model, calculates the direction of the maximum principal stress in each finite element after meshing, sets a stress threshold to screen high stress seed points, uses a clustering algorithm to generate continuous streamlines, and generates a steel reinforcement layout path and concrete printing trajectory based on the streamlines and stress-oriented principle; based on the path and trajectory, the lining 3D model is decomposed into several printing layers using a slicing algorithm, and the printing sequence of each layer is planned.

[0015] Step 3: According to the printing sequence, the concrete 3D printing module deposits concrete material along the concrete printing trajectory using its robotic arm, while the steel bar laser printing module laser-clad steel bars along the steel bar arrangement path using its robotic arm, so as to achieve synchronous printing of the two materials and control the height of the steel bar printing layer to be 3-6mm higher than the concrete printing layer in the same layer.

[0016] Meanwhile, during the synchronous printing process, the temperature field of the laser cladding area is monitored in real time by a thermodynamic camera, and the laser power and wire feed speed are dynamically adjusted based on temperature feedback to control the temperature fluctuation of the laser cladding area within a preset range.

[0017] Furthermore, in the finite element mechanical analysis, an equivalent surrounding rock load, calibrated by geological survey data, is applied to the outside of the lining three-dimensional model.

[0018] Furthermore, methods for generating continuous streamlines include:

[0019] Mechanical simulation analysis was performed on the meshed 3D model of the lining to extract the maximum principal stress value and the corresponding direction of each finite element.

[0020] Set a principal stress threshold and select high-stress region elements as candidate seed points;

[0021] The KMeans clustering algorithm was used to group the candidate seed points and select representative seed points.

[0022] Starting from the selected seed point, streamline tracing is performed along the principal stress direction of the unit. During the tracing process, the principal stress directions of adjacent units are processed by distance weighted averaging to smooth abrupt changes in the principal stress direction, generating streamlines that reflect the continuous transmission path of the principal stress inside the lining.

[0023] Furthermore, in step 2, generating the reinforcement layout path based on the stress-directed principle includes:

[0024] Based on the continuous streamlines, the main reinforcement path is arranged along the main streamline direction so that the reinforcement direction coincides with the direction of the maximum principal stress.

[0025] In areas of high stress concentration, the number of rebar paths can be increased or the spacing between paths can be reduced, depending on the density of the streamline distribution.

[0026] In areas with high streamline curvature, adjust the bending angle of the rebar path or add auxiliary rebar paths to match the rebar distribution with the changes in streamline curvature.

[0027] Furthermore, in step 2, the process of generating the concrete printing trajectory includes:

[0028] Based on the geometric contour of the lining 3D model, a continuous concrete printing trajectory matching the tunnel surface is generated, and the concrete printing trajectory and the reinforcement layout path are spatially coordinated to ensure that the reinforcement can form a tight bond within the printed concrete layer.

[0029] Furthermore, in step 3, the process of dynamically adjusting the laser power and wire feed speed based on temperature feedback includes:

[0030] The temperature and geometric area of ​​the molten pool in the laser cladding area are monitored in real time using a thermodynamic camera, and temperature deviation data and area deviation data are obtained respectively.

[0031] The temperature deviation data and area deviation data are used as inputs, and the laser power and wire feeding speed are dynamically and collaboratively adjusted based on the coupled PID control law, outputting the laser power adjustment amount and the wire feeding speed adjustment amount.

[0032] Furthermore, the control module adopts a hierarchical control strategy, including:

[0033] First-level rapid temperature control: The molten pool temperature is monitored in real time with a sampling period of milliseconds by a thermodynamic camera. When the temperature deviates from the target value by more than 10K, the laser power is immediately and rapidly adjusted based on the current temperature deviation and the trend of change to stabilize the molten pool temperature within the target range.

[0034] Secondary morphology stabilization control: Simultaneously monitor the geometric area of ​​the molten pool. When the area fluctuation exceeds ±5% of the target value, adjust the wire feeding speed proportionally to maintain the stability and consistency of the molten pool morphology.

[0035] Three-level safety protection control: Set an absolute safety threshold. When the temperature of the molten pool exceeds the upper limit or the area is significantly abnormal, the system will automatically perform protective intervention, including reducing laser power, limiting wire feed speed, and pausing printing for interlayer cooling. The system will resume operation after the temperature returns to normal.

[0036] The beneficial effects of this invention are:

[0037] (1) This invention integrates the principal stress traces obtained from finite element mechanics inversion into the 3D printing slicing algorithm. By constructing a three-dimensional finite element model of the lining that conforms to actual working conditions and conducting stress analysis, the distribution characteristics of the principal stress inside the lining are obtained. Through stress-guided path planning, the reinforcement is arranged along the main stress direction, no longer relying on a pre-set regular mesh reinforcement scheme. This method not only significantly improves the overall bearing capacity and crack resistance of the lining, but also reduces unnecessary reinforcement usage, achieving the dual goals of optimizing material utilization and maximizing structural performance.

[0038] (2) This invention achieves simultaneous molding of concrete extrusion printing and steel reinforcement laser additive manufacturing, breaking through the traditional fragmented multi-process mode of "spraying concrete first, then binding or planting steel bars" in lining construction. By realizing real-time synchronous deposition of steel bars and concrete in a unified device, problems such as positioning deviation, interface weakening and construction discontinuity caused by process intervals can be effectively avoided, forming an integrated structure with strong interface bonding and continuous stress link. Relying on this collaborative molding mechanism, this invention can achieve fully unmanned and automated lining construction operations in the narrow, continuous and high-intensity working conditions of shield tunneling in harsh environments, greatly improving construction efficiency and quality stability, and providing a reliable technical path for intelligent tunnel construction.

[0039] (3) Real-time temperature field monitoring and closed-loop control of thermodynamic camera are introduced. By dynamically adjusting laser power and wire feeding speed, real-time correction of additive material quality is achieved, effectively suppressing overheating, undermelting and interface defects, and ensuring the quality and interface reliability of steel reinforcement additives. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure of a reinforced concrete synchronous 3D printing lining device used for TBM.

[0041] Figure 2 This is a schematic diagram of the tunnel construction environment;

[0042] Figure 3 This is a schematic diagram showing the assembly relationship between the concrete 3D printing module and the concrete 3D printing robotic arm.

[0043] Figure 4 This is a schematic diagram of a concrete 3D printing module structure;

[0044] Figure 5 This is a schematic diagram showing the assembly relationship between the rebar laser printing module and the rebar laser printing robotic arm;

[0045] Figure 6 This is a schematic diagram of the steel bar laser printing module structure;

[0046] Figure 7 This is a finite element analysis cloud diagram of the lining load;

[0047] Figure 8 This is a principal stress streamline diagram of the lining load finite element analysis;

[0048] In the diagram, 1-Construction track, 2-Construction track vehicle, 3-LiDAR, 4-Rebar laser printing robotic arm, 5-Rebar laser printing module, 6-Concrete 3D printing module, 7-Concrete 3D printing robotic arm, 8-Tunnel ring, 501-Laser processing head, 502-Wire outlet, 503-Wire feeding inlet, 504-Connecting device, 505-Heat dissipation device, 506-Thermodynamic camera, 601-Stepper motor, 602-Motor support, 603-Rigid coupling, 604-Hopper, 605-Nozzle, 606-Spiral extrusion rod, 607-Cylinder wall scraper, 608-Feeding interface, 609-Fixed mounting plate. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can also refer to the internal connection of two components. "A plurality of" or "several" means two or more. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0051] The overall diagram of the reinforced concrete synchronous 3D printing lining device for TBM proposed in this invention is as follows: Figure 1As shown, the system mainly includes a construction railcar 2, a lidar 3, a rebar laser printing robotic arm 4, a rebar laser printing module 5, a concrete 3D printing module 6, and a concrete 3D printing robotic arm 7. The construction railcar 2 operates on the construction rail 1 at the bottom of the tunnel. Its bottom-mounted walking mechanism forms a support platform that can move along the tunnel axis. The construction rail 1 provides precise guidance and stable support for the construction railcar 2. The lidar 3 is mounted on a tripod, which is fixed to the railcar. It can follow the railcar to scan the tunnel printing surface and generate point cloud data of the actual tunnel cross-section. The bases of the concrete 3D printing robotic arm 7 and the rebar laser printing robotic arm 4 are firmly installed on the platform surface of the construction railcar 2. The ends of the two robotic arms are respectively equipped with the concrete 3D printing module 6 and the rebar laser printing module 5. Due to the narrow and complex tunnel construction environment, continuous operation is achieved through railcar movement, avoiding frequent equipment adjustments. The separate design of the robotic arm and module improves flexibility and maintainability. Figure 2 This is a schematic diagram of a tunnel construction environment, illustrating the operation of the reinforced concrete synchronous 3D printing lining device for TBM described in this invention inside a tunnel, where steel bars and concrete are simultaneously printed onto the inner wall of the tunnel ring 8.

[0052] Specifically, the assembly relationship between the concrete 3D printing module 6 and the concrete 3D printing robotic arm 7 is as follows: Figure 3 As shown, the concrete 3D printing module 6 is threadedly connected to the concrete 3D printing robotic arm 7 via a circumferential threaded hole on the end flange of the concrete 3D printing robotic arm 7. The assembly relationship between the rebar laser printing module 5 and the rebar laser printing robotic arm 4 is as follows: Figure 5 As shown, the rebar laser printing module 5 is threadedly connected to the rebar laser printing robotic arm 4 via a circumferential threaded hole on the end flange. The lidar 3 is fixed to a tripod on the construction railcar 2 and can move with the vehicle to scan the tunnel cross-section. Both the concrete 3D printing robotic arm 7 and the rebar laser printing robotic arm 4 are connected to the construction railcar 2 using anchor bolts to ensure the stability of the printing device. The anchor bolt connection enhances vibration resistance and adapts to the dynamic loads during TBM excavation.

[0053] like Figure 4As shown, the concrete 3D printing module 6 mainly includes a stepper motor 601, a motor support 602, a rigid coupling 603, a hopper 604, a nozzle 605, a spiral extrusion rod 606, a cylinder wall scraper 607, a feed inlet 608, and a fixed mounting plate 609. Stepper motor 601 is threaded onto motor support 602, which is bolted to mounting plate 609. The output shaft of stepper motor 601 passes vertically through mounting plate 609 and is connected to spiral extrusion rod 606 via rigid coupling 603. Hopper 604 is bolted to mounting plate 609, and a side opening in hopper 604 serves as feed inlet 608 for continuous material feeding. Nozzle 605 is threaded onto outlet of hopper 604. Spiral extrusion rod 606 is vertically installed in hopper 604, and wall scraper 607 is welded to spiral extrusion rod 606 to thoroughly mix concrete accumulated on the hopper wall during 3D printing. The spiral extrusion rod combined with wall scraper prevents concrete segregation or clogging, ensuring uniform extrusion. Rigid coupling ensures stable torque transmission, preventing printing interruptions. Nozzle can be replaced according to actual needs, adapting to different lining conditions and construction requirements, improving printing accuracy and efficiency.

[0054] like Figure 6As shown, the rebar laser printing module 5, a key component for in-situ rebar forming in this invention, mainly includes a laser processing head 501, a wire feeding mechanism, a connecting device 504, a heat dissipation device 505, and a thermodynamic camera 506. The laser processing head 501 and the heat dissipation device 505 are threadedly connected to the connecting device 504. Both mechanisms can have their power adjusted via a host computer. The heat dissipation device 505 employs a liquid-cooled circulating cooling method to prevent thermal damage to the printed concrete layer caused by the high temperatures generated during laser processing, maintain a stable laser operating temperature, ensure stable laser output power, and adapt to the harsh environment of continuous operation inside tunnels. The wire feeding mechanism includes a wire outlet 502 and a wire inlet 503. A precision servo motor drives the mechanism, which is hinged to the connecting device 504. This allows for free adjustment of the position between the wire outlet 502 and the laser processing head 501, adapting to lining surfaces with different curvatures. This ensures the wire always enters the molten pool at the optimal angle and can dynamically adjust according to complex changes in the rebar path, achieving precise forming of spatially curved rebars. This avoids cladding quality defects caused by positional deviations and improves forming accuracy. The metal wire enters through the wire inlet 503, is ultimately conveyed to the wire outlet 502, and finally reaches the molten pool. A thermodynamic camera 501 is threadedly connected to the laser processing port for easy monitoring of the molten pool temperature field. In this module, the metal wire enters through the wire inlet 503, is precisely metered, and then conveyed to the wire outlet 502. The laser processing head 501 forms a high-temperature molten pool at a predetermined position, instantly melting the wire end and bonding it to the substrate. Throughout the process, the thermodynamic camera 506 continuously monitors the molten pool state, and the data is uploaded to the control system in real time. The position of the molten pool is adjusted by the posture adjustment of the laser processing head 501 via a robotic arm, and continuous and stable forming is ensured by a hinged adjustable wire outlet; a heat dissipation device prevents overheating from affecting the concrete substrate. In-situ forming of reinforcing bars is achieved through laser cladding, reducing prefabrication steps. The use of a thermodynamic camera ensures the quality of the printed interface and avoids thermal damage. In this embodiment, the laser processing head 501 uses a high-power fiber laser, and the output laser, after focusing, can form an energy density of over 3kW / cm² in the processing area. The thermodynamic camera 506 has a sampling frequency of up to 1000Hz.

[0055] Before construction begins, a high-precision scan of the tunnel excavation face and the area to be constructed is performed using LiDAR to obtain real construction topography data. This data is automatically converted into a 3D solid model and imported into finite element analysis software to construct a 3D model of the lining. Numerical simulation analysis of the structural stress state is performed within the finite element analysis software, adaptively planning printing process parameters (including nozzle speed, extrusion speed, rebar placement path and density, etc.). The rebar placement path and density are generated by extracting the principal stress traces of the lining. Subsequently, after obtaining the rebar placement path and the 3D model of the lining to be printed, a slicing algorithm is used to decompose the entire lining into several printing layers, generating digital slices with adaptive rebar direction. This forms a slice model for the co-printing of rebar and concrete. Subsequent layer-by-layer path planning can be performed based on this slice, simultaneously generating the concrete printing trajectory and the rebar additive trajectory, ensuring that the rebar can form a tight bond within the printed concrete layer, making the forming process continuous and stable. During the slicing process, the height of the rebar printing layer is controlled to be slightly higher than the concrete layer to achieve continuous and stable deposition of the rebar on the existing rebar substrate.

[0056] like Figure 7 As shown, this invention establishes a three-dimensional finite element model of the lining based on ABAQUS software, with structural dimensions strictly determined according to the actual working conditions of a TBM tunnel. To realistically simulate the interaction between the surrounding rock and the lining structure, an equivalent surrounding rock load calibrated by geological survey data is applied outside the model, and boundary conditions conforming to actual constraints are set. The concrete material adopts the concrete damage-plastic (CDP) constitutive model to accurately characterize the nonlinear mechanical behavior of concrete under alternating tension and compression.

[0057] After completing the finite element analysis, the system first extracts the maximum principal stress value and corresponding principal stress direction for each element, using the centroid position of high principal stress elements as seeds. Then, by setting a principal stress threshold (e.g., selecting the top 15%–30% of high principal stress elements), high-stress regions are screened as candidate streamline seeds, intelligently identifying key stress areas of the structure. To ensure that streamlines cover key stress areas, this invention uses the KMeans clustering algorithm to group candidate seeds based on spatial location and principal stress measurement, selecting several representative seed points to generate continuous streamlines. During streamline generation, to ensure streamline continuity and conformity to actual structural stress, a principal stress direction smoothing algorithm is introduced. This involves using a distance-weighted average of the principal stress directions of neighboring elements to effectively reduce abrupt changes in direction. Simultaneously, streamline points are located within structural elements, ensuring that streamlines accurately reflect the stress transmission direction within the lining, providing a reliable basis for reinforcement arrangement.

[0058] like Figure 8As shown, the final generated principal stress streamlines clearly demonstrate the force flow distribution characteristics within the structure. Based on this streamline map, the arrangement of the foundation reinforcement is optimized: First, the main reinforcement bars are arranged along the main streamline direction, ensuring that the direction of the reinforcement bars matches the direction of the maximum principal stress, thereby guaranteeing that the reinforcement bars can effectively bear tensile stress. In areas of high stress concentration, the number of reinforcement bars is increased or the spacing is reduced according to the density of streamlines to achieve localized reinforcement; in areas with large streamline curvature, the bending angle of the reinforcement bars is adjusted or auxiliary reinforcement bars are added to match the reinforcement bar path with the streamline curvature, ensuring continuous and uniform force transmission. Similarly, in low-stress areas, the number of reinforcement bars can be reduced or the spacing can be extended. Through the above strategies, the reinforcement arrangement not only closely matches the actual stress direction of the structure but also balances material utilization efficiency and the overall load-bearing capacity of the structure, significantly improving the load-bearing efficiency and construction feasibility of the lining structure.

[0059] The concrete 3D printing module is responsible for stably extruding printable concrete material according to the planned path, achieving high-precision interlayer stacking. Concrete is continuously supplied by the feed interface 508 of the concrete 3D printing module 5, and is stably conveyed under the action of the spiral extrusion rod 606 driven by a stepper motor 601. The speed of the stepper motor 601 is adjusted by the control system, which can adjust the extrusion speed in real time according to the printing speed to ensure the uniformity of the printed filament. Freshly mixed concrete is extruded through the nozzle 605 and deposited onto the surface of the tunnel ring 8. As the end of the concrete 3D printing robotic arm 7 moves along the planned trajectory, it forms high-precision printed filaments. In this embodiment, the nozzle 605 can adopt a special curved surface design so that the extruded concrete filaments can perfectly conform to the tunnel contour.

[0060] The rebar laser printing module feeds a quantitative amount of metal wire into the laser cladding area via a wire feeding mechanism. The laser processing head generates a high-energy-density molten pool in a localized area, causing the metal wire to melt instantaneously and solidify with the previous layer of metal to form a continuous and dense reinforcing bar, thereby forming a load-bearing additive reinforcing bar. Specifically, the rebar wire is fed from the wire inlet 503 to the wire outlet 502. The laser processing head focuses a high-energy-density beam at the intersection of the wire and the substrate, forming a localized molten pool. The end of the wire melts rapidly and bonds with the substrate, then cools and solidifies to complete the deposition. This invention employs a layered printing strategy. By controlling the height of the rebar layer to be slightly higher than the concrete layer by 3-6 mm, it ensures that when printing a new layer of rebar, the starting point of the laser cladding is firmly established on the solidified previous layer of rebar, forming a reliable intermetallic bond, rather than depositing on the incompletely cured concrete surface. This avoids mutual interference between different material layers, thus ensuring the integrity, stability, and overall structural integrity of the rebar skeleton in continuous stacking.

[0061] In the simultaneous printing of concrete and reinforcing steel in tunnel lining, the high-temperature molten pool generated during laser cladding of the reinforcing steel interacts intensely with the incompletely cured concrete substrate, which is in a sensitive hydration stage, through both thermal radiation and heat conduction. This thermal effect is one of the most critical technological challenges determining the final forming quality, interfacial integrity, and long-term durability of the composite structure. Improper control of the molten pool heat input can easily induce localized high temperatures and steep temperature gradients within the concrete matrix, leading to thermal stress concentration, microcrack formation, and interfacial degradation, thereby reducing the overall mechanical properties and dimensional accuracy of the formed structure. To address this, this invention proposes a closed-loop molten pool heat control method. By real-time monitoring and dynamic adjustment of the molten pool temperature, precise control of heat input is achieved, reducing the impact of thermal disturbance on the printed concrete layer.

[0062] In one specific embodiment of this invention, precise management of heat input energy is achieved through real-time and precise monitoring of the thermophysical state of the molten pool and dynamic coordinated adjustment of multiple parameters. This minimizes the negative impact of thermal disturbance on the concrete substrate and ensures the integrated molding quality of the composite structure. The control system uses the molten pool temperature, which directly affects the molding quality, as a key factor. The geometric area of ​​the molten pool characterizes its stability. As the primary controlled variable, the molten pool is synchronously monitored at the millisecond level using a high-resolution thermodynamic camera to acquire temperature field and morphology images, and the deviations from the preset target values ​​are calculated, corresponding to temperature deviations. Area deviation ,in and To set a target value, based on the aforementioned deviation, the control system adjusts the laser power using a coupled PID control law. With wire feeding speed The control law for dynamic coordinated adjustment is as follows:

[0063]

[0064] The controller input is the deviation vector:

[0065]

[0066] The control output is an adjustment signal vector:

[0067]

[0068] in, This refers to the laser power adjustment amount. This refers to the adjustment amount of the wire feeding speed.

[0069] Here is the coupling gain matrix:

[0070]

[0071] in, Used to characterize the proportional effect of molten pool temperature deviation on laser power adjustment; Used to characterize the compensation and adjustment of laser power by the geometric area deviation of the molten pool; Used to characterize the indirect adjustment of wire feed speed by molten pool temperature deviation; Used to characterize the direct adjustment of wire feed speed by the geometric area deviation of the molten pool. Integral gain matrix. Used for time-cumulative correction of temperature and area deviations; differential gain matrix Used to suppress the rate of change of molten pool temperature and the rate of change of geometric area.

[0072] It can indirectly correct the wire feeding speed due to temperature deviation and synergistically compensate the laser power due to area deviation. Temperature deviation not only directly adjusts the laser power, but also indirectly affects the wire feeding speed to change the ratio of heat input to material input. Similarly, area deviation directly adjusts the wire feeding speed and also compensates for the laser power.

[0073] The control system's execution logic is divided into three layers. The first layer is rapid temperature control, with the control objective being to maintain the molten pool temperature at... Within, its ultra-high frequency (sampling period) Monitor temperature; when the absolute value of the temperature deviation is detected... Dynamically adjust power:

[0074]

[0075] First-level rapid temperature control can respond within milliseconds, quickly pulling the molten pool temperature back up. The stable range is to prevent instantaneous thermal shock.

[0076] The second level is area stability control, and the control objective is to maintain the molten pool area at a certain level. The sampling period is When the area deviation exceeds the limit, the wire feeding speed is adjusted proportionally:

[0077]

[0078] Secondary area stabilization control ensures the uniformity and consistency of the cladding morphology.

[0079] Level three is for safety protection, setting an absolute safety threshold; when a detection... or When the system detects a dangerous situation, it immediately implements protective intervention: reducing the laser power by 15% and limiting the wire feeding speed to the rated value. 60%. If the temperature does not drop within the set time, the "interlayer cooling wait" mechanism is activated, pausing the printing operation for 0.5-1.0 seconds to allow the concrete substrate to cool down naturally through heat diffusion, thus fundamentally avoiding overheating damage.

[0080] The control system achieves dynamic balance control of heat input and material supply in the molten pool through coordinated compensation of temperature deviation and area deviation, thereby improving the temperature stability of the molten pool to ±10 K and the geometric area fluctuation to less than ±5%. This effectively suppresses thermal cracking and delamination of the concrete matrix and significantly improves the interfacial bonding strength and forming accuracy of the concrete-reinforced composite printed structure.

[0081] This invention utilizes a thermodynamic camera to monitor the temperature field of the laser printing area in real time. The closed-loop temperature control method described above can respond quickly in the early stages of temperature fluctuations. Based on temperature feedback, key process parameters such as laser power and wire feed speed are adjusted in a closed loop to achieve precise control of the molten pool temperature. This ensures the interface quality and overall forming accuracy of the concrete-reinforced steel composite structure, providing key technical support for the engineering application of simultaneous printing of concrete and steel reinforcement.

[0082] Through repeated iterations of the above steps, the concrete and steel bar printing modules move in a coordinated manner with a unified temporal sequence and spatial path, completing the structural forming of the steel bar reinforced 3D printed lining layer by layer, realizing a high-precision and high-efficiency integrated construction process.

[0083] This invention proposes a synchronous 3D printing device for reinforced concrete lining in TBM (Tunnel Boring Machine). Through the coupled control of concrete printing and laser additive manufacturing of reinforcing steel, the device achieves simultaneous deposition of reinforcing steel and concrete materials within the same construction window, resulting in reinforced concrete linings with higher structural integrity, superior mechanical properties, and stronger construction continuity. The system mainly consists of a concrete printing module and a laser printing module for reinforcing steel, supplemented by an environmental scanning module and a thermal monitoring closed-loop control module, realizing fully automated construction from morphology acquisition, modeling and simulation, adaptive slicing, to synchronous printing of two materials.

[0084] This device adopts a highly modular architecture design, integrating a reconfigurable control interface and an algorithm-driven path planning mechanism, possessing excellent system scalability and scenario adaptability. Through algorithm upgrades, it can support printing and monitoring functions for more materials; by flexibly combining concrete printing modules and rebar additive modules, it can adapt to different geological conditions, lining cross-sectional types, and construction organization requirements; and by being compatible with various motion execution equipment such as robotic arms or gantry cranes, it can meet the intelligent construction needs of various scenarios such as buildings, bridges, and underground engineering. This device demonstrates broad application prospects in improving structural quality, reducing labor costs, and promoting the rational construction of complex structures, and has significant practical value and promotional significance for promoting the intelligent upgrading of the construction industry and the construction of high-performance structures.

[0085] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A device for simultaneous 3D printing of reinforced concrete lining for TBM, characterized in that, It includes a construction track vehicle (2), a lidar (3), a concrete 3D printing module (6), a steel bar laser printing module (5), and a control module; The construction railcar (2) moves along the tunnel axis via the construction rail (1) inside the tunnel, and the lidar (3) is fixed on the construction railcar (2) to scan the tunnel shape; the concrete 3D printing module (6) and the steel bar laser printing module (5) are respectively installed on the construction railcar (2) via an independent robotic arm, and the steel bar laser printing module (5) is equipped with a thermodynamic camera (506). The control module is used to construct a three-dimensional model of the lining based on the tunnel topography data scanned by the lidar (3), and extract the principal stress traces through finite element analysis to generate a steel reinforcement layout path and concrete printing trajectory based on the principle of stress guidance. The steel bar laser printing module (5) and the concrete 3D printing module (6) print synchronously along the steel bar layout path and the concrete printing trajectory, respectively, and control the steel bar layer height to be higher than the concrete layer; the thermodynamic camera (506) and the control module work together to dynamically adjust the laser power and wire feeding speed of the steel bar laser printing module (5) and control the temperature fluctuation of the laser processing area within the preset deviation.

2. The reinforced concrete synchronous 3D printing lining device for TBM according to claim 1, characterized in that, The concrete 3D printing module (6) includes a stepper motor (601), a hopper (604), and a spiral extrusion rod (606). The stepper motor (601) drives the spiral extrusion rod (606) to rotate inside the hopper (604) through a rigid coupling (603). The side wall of the hopper (604) is provided with a feeding interface (608), and the bottom of the hopper (604) is connected to a nozzle (605). A cylinder wall scraper (607) is welded on the spiral extrusion rod (606) for scraping off the concrete adhering to the hopper wall during rotation.

3. The reinforced concrete synchronous 3D printing lining device for TBM according to claim 1, characterized in that, The rebar laser printing module (5) includes a laser processing head (501), a heat dissipation device (505), a wire feeding mechanism, and a thermodynamic camera (506); the laser processing head (501) and the heat dissipation device (505) are fixed by a connecting device; the wire feeding mechanism is hinged to the connecting device, includes a wire feeding inlet (503) and a wire outlet (502), and the relative position of the wire feeding inlet (503) and the laser processing head is adjustable; the thermodynamic camera (506) is fixed to the side of the laser processing head.

4. A printing method for a reinforced concrete synchronous 3D printing lining device for TBM based on claim 1, characterized in that, Includes the following steps: Step 1: The construction track vehicle (2) moves along the construction track (1) inside the tunnel, driving the laser radar (3) fixed on it to scan the tunnel cross section, obtain morphological data and construct a three-dimensional model of the lining. Step 2: The control module performs finite element mechanical analysis based on the lining 3D model, calculates the direction of the maximum principal stress in each finite element after meshing, sets a stress threshold to screen high stress seed points, uses a clustering algorithm to generate continuous streamlines, and generates a steel reinforcement layout path and concrete printing trajectory based on the streamlines and stress-oriented principle; based on the path and trajectory, the lining 3D model is decomposed into several printing layers using a slicing algorithm, and the printing sequence of each layer is planned. Step 3: According to the printing order, the concrete 3D printing module (6) deposits concrete material along the concrete printing trajectory through its robotic arm, while the steel bar laser printing module (5) laser clads steel bars along the steel bar arrangement path through its robotic arm, so as to realize the synchronous printing of the two materials and control the height of the steel bar printing layer in the same layer to be 3-6mm higher than the concrete printing layer. Meanwhile, during the synchronous printing process, the temperature field of the laser cladding area is monitored in real time by a thermodynamic camera (506), and the laser power and wire feeding speed are dynamically adjusted based on temperature feedback to control the temperature fluctuation of the laser cladding area within a preset range.

5. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 4, characterized in that, In finite element mechanical analysis, an equivalent surrounding rock load, calibrated by geological survey data, is applied to the outside of the lining three-dimensional model.

6. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 4, characterized in that, Methods for generating continuous streamlines include: Mechanical simulation analysis was performed on the meshed 3D model of the lining to extract the maximum principal stress value and the corresponding direction of each finite element. Set a principal stress threshold and select high-stress region elements as candidate seed points; The KMeans clustering algorithm was used to group the candidate seed points and select representative seed points. Starting from the selected seed point, streamline tracing is performed along the principal stress direction of the unit. During the tracing process, the principal stress directions of adjacent units are processed by distance weighted averaging to smooth the abrupt change in the principal stress direction, generating streamlines that reflect the continuous transmission path of the principal stress inside the lining.

7. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 4, characterized in that, Step 2, generating the reinforcement layout path based on stress guidance includes: Based on the continuous streamlines, the main reinforcement path is arranged along the main streamline direction so that the reinforcement direction coincides with the direction of the maximum principal stress. In areas of high stress concentration, the number of rebar paths can be increased or the spacing between paths can be reduced, depending on the density of the streamline distribution. In areas with high streamline curvature, adjust the bending angle of the rebar path or add auxiliary rebar paths to match the rebar distribution with the changes in streamline curvature.

8. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 7, characterized in that, Step 2, the process of generating the concrete printing trajectory includes: Based on the geometric contour of the lining 3D model, a continuous concrete printing trajectory matching the tunnel surface is generated, and the concrete printing trajectory and the reinforcement layout path are spatially distributed in coordination.

9. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 4, characterized in that, Step 3, the process of dynamically adjusting the laser power and wire feed speed based on temperature feedback, includes: The temperature and geometric area of ​​the molten pool in the laser cladding area are monitored in real time using a thermodynamic camera, and temperature deviation data and area deviation data are obtained respectively. The temperature deviation data and area deviation data are used as inputs, and the laser power and wire feeding speed are dynamically and collaboratively adjusted based on the coupled PID control law, outputting the laser power adjustment amount and the wire feeding speed adjustment amount.

10. The printing method for a reinforced concrete synchronous 3D printing lining device for TBM according to claim 9, characterized in that, The control module adopts a hierarchical control strategy, including: First-level rapid temperature control: The molten pool temperature is monitored in real time with a sampling period of milliseconds by a thermodynamic camera. When the temperature is detected to deviate from the target value by more than 10K, the laser power is immediately and rapidly adjusted based on the current temperature deviation and the trend of change to stabilize the molten pool temperature within the target range. Secondary morphology stabilization control: Simultaneously monitor the geometric area of ​​the molten pool. When the area fluctuation exceeds ±5% of the target value, adjust the wire feeding speed proportionally to maintain the stability and consistency of the molten pool morphology. Three-level safety protection control: Set an absolute safety threshold. When the temperature of the molten pool exceeds the upper limit or the area is significantly abnormal, the system will automatically perform protective intervention, including reducing laser power, limiting wire feed speed, and pausing printing for interlayer cooling. The system will continue to operate after the temperature returns to normal.

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