A 3D printing concrete structure with constant distance and self-locking steel mesh and a construction method thereof

Abstract

The application is a kind of fixed-distance self-locking steel mesh jet 3D printing concrete structure and its construction method. The structure includes a concrete base formed by layer-by-layer jetting and a planar steel mesh sheet arranged at intervals along the thickness direction of the component. The fixed connection seat between adjacent planar steel mesh sheets and the corresponding locking seat are connected to form an interlayer connection node, which includes a fixed connection seat, a fixed-distance support section, a limiting shoulder, a socket joint and a locking seat. The socket joint forms a one-way mechanical lock with the locking seat installed on the adjacent layer, and the end face of the locking seat abuts against the limiting shoulder to define the spacing between adjacent mesh sheets; the limiting shoulder also serves as the thickness termination reference of the current jetting layer. The socket joint is provided with a detachable anti-blocking protective cap and a geometric identification mark to determine the position of the connection node and the relative height difference between the limiting shoulder and the current jetting surface. The application can reduce temporary support and manual review, stabilize the control of mesh layer distance and layer thickness, and reduce the risk of mesh slip under jetting impact.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing and intelligent construction technology for reinforced concrete structures, specifically to a fixed-distance self-locking steel mesh sprayed 3D printed concrete structure and its construction method. Background Technology

[0002] Additive manufacturing in construction can complete the forming of complex components with reduced use of formwork. Jetting 3D printing also has the advantages of strong adaptability to working space, flexible forming path, and convenient continuous on-site construction. However, reinforced concrete components still face the problem of difficulty in coordinating reinforcement installation and material jetting during jetting 3D printing. Traditional steel cages occupy a large space and have densely intersecting members. When the spray gun moves around the steel cage, path interference is prone to occur. After the jetting material flows through the steel, it is easy to form obstructions and shadow areas, which may lead to insufficient material on the back of the steel, local voids, increased springback, and component thickness deviations.

[0003] To reduce the continuous obstruction of the concrete spraying process by the reinforcing steel cage, existing construction methods employ a layered placement of planar reinforcing mesh, alternating between concrete spraying and mesh installation. While this method reduces construction obstacles caused by setting up a complete reinforcing cage at once, the positioning of adjacent meshes still typically relies on temporary spacers, binding wires, positioning brackets, or on-site welding for control. These methods involve numerous installation steps, and positioning accuracy is significantly affected by manual operation, making it difficult to stably coordinate with the continuous operation cycle of 3D printing.

[0004] During the layered installation of reinforcing mesh, ordinary hooks, plug-in connectors, or simple connecting rods can usually only achieve partial attachment or temporary positioning, making it difficult to simultaneously guarantee the designed spacing and connection stability between adjacent reinforcing meshes. When the component is in a vertical, inclined, or upward construction state, the reinforcing mesh may also slip, rotate, or detach under its own weight or the impact of spraying. The connection points are also easily contaminated, blocked, or completely covered by cement-based materials during the spraying process, making it difficult to accurately connect subsequent mesh panels and increasing the amount of manual cleaning and rework.

[0005] In jet 3D printing, methods such as 3D scanning and laser ranging can typically be used to inspect the surface contours of components, identify areas of under-spraying, and measure thickness deviations. However, if the inspection is limited to the surface morphology of concrete, it is impossible to directly determine whether the rebar mesh connection positions are accurate, whether the limiting shoulder has reached the designed jetting height, whether sufficient assembly space has been reserved at the connection points, and whether the next layer of rebar mesh is ready for installation. Furthermore, if the interlayer connecting components are too densely arranged, it can increase the obstruction of the jetting flow, making it more prone to incomplete filling problems on the back of the rebar and connection nodes.

[0006] Therefore, the existing spraying 3D printing reinforced concrete construction method still needs further improvement in terms of spacing and positioning between steel mesh layers, mechanical locking to prevent detachment, anti-blocking of connection parts, spraying thickness benchmark control, and connection node status detection, in order to reduce temporary support and manual verification, improve the synergy between layered assembly of steel mesh and continuous spraying of concrete, and improve the material wrapping quality around the steel bars and connection nodes. Summary of the Invention

[0007] The purpose of this invention is to provide a fixed-distance self-locking steel mesh sprayed 3D printed concrete structure and its construction method, so as to solve the problems of difficult control of layer spacing, easy blockage of connection parts, easy slippage of mesh under spraying impact, difficulty in filling the back of steel bars, and inability of scanning or ranging systems to directly determine whether the next layer has the conditions for assembly in the existing layer-by-layer construction of steel mesh.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] In a first aspect, the present invention provides a fixed-distance self-locking steel mesh sprayed 3D printed concrete structure, comprising a concrete matrix formed by layer-by-layer spraying, and at least two planar steel meshes spaced apart along the thickness direction of the concrete matrix; a fixing seat is provided on some mesh nodes of the bottom planar steel mesh, and a locking seat is provided on some mesh nodes of the top planar steel mesh; a locking seat is provided on the front side of some mesh nodes of the middle planar steel mesh, and a fixing seat is provided on the rear side of some mesh nodes of the middle planar steel mesh; Each fixed joint is provided with a fixed-distance support section extending in the direction of the layer to be constructed. A limiting shoulder is provided at the end of the fixed-distance support section, and a socket joint extends outward from the limiting shoulder. The locking seat has an open sleeve for inserting the socket joint and a locking member for preventing the socket joint from retracting in the opposite direction. After the socket joint is inserted into the locking seat at the corresponding position of the adjacent planar steel mesh, the end face of the locking seat abuts against the limiting shoulder to limit the design spacing between adjacent planar steel meshes. When the concrete around the current steel mesh module is sprayed to the corresponding position of the limiting shoulder, the socket joint remains outside the concrete spraying surface so that the next planar steel mesh can be socketed and locked. The fixed joints and corresponding locking joints between adjacent planar steel meshes form interlayer connection nodes.

[0010] Secondly, the present invention provides a construction method for the above-mentioned structure. Before construction, a working surface model is established by three-dimensional scanning, and the spraying path and the installation coordinates of the planar steel mesh and inter-layer connection nodes are generated; after spraying the bottom layer concrete to the installation elevation of the first mesh, the first steel mesh module is placed, and some mesh nodes of the planar steel mesh of the first steel mesh module are provided with fixed seats and their connecting parts; anti-blocking protective caps 25 are installed outside the socket joint 24; the spray gun first fills the back of the steel bars from both sides of the component normal at different angles through the spraying window 3, and then performs surface shaping spraying until the current sprayed surface 5 reaches the height corresponding to the limiting shoulder 23. Using a 3D scanning system or laser ranging system, the geometric identification marks of the anti-blocking protective cap are identified to determine the location of the interlayer connection nodes and the relative height difference between the limiting shoulder and the current sprayed surface. Abnormal areas are then locally reinforced, scraped, or corrected. After successful correction, the anti-blocking protective cap 25 is removed by a mechanical clamp or the end effector of a robotic arm. The next steel mesh module, with the pre-set locking seat 26, is then pressed into the socket joint 24 until the elastic locking plate 262 enters the annular locking groove 242 and the end face of the locking seat 26 abuts against the limiting shoulder 23. The above steps are repeated to form a continuous modular steel reinforcement skeleton along the thickness direction of the component. The outermost protective layer is then sprayed and cured.

[0011] Furthermore, the spraying equipment used in the construction method includes a mobile chassis, a six-degree-of-freedom robotic arm, a printing spray gun, a feeding system, a three-dimensional scanning system, a laser ranging system, and a control system. The three-dimensional scanning system or laser ranging system is located at the end of the robotic arm or near the printing spray gun and is used to measure the relative position between the current spraying surface and the geometric identification mark of the limiting shoulder or anti-clogging protective cap. The control system adjusts the spray gun moving speed, spray flow rate, spray gun posture, and number of repeated sprays based on the measurement results.

[0012] Thirdly, the present invention also protects components constructed using the construction method described above or having the aforementioned spaced self-locking steel mesh sprayed 3D printed concrete structure, wherein the components are any one of wall panels, bridge deck or road repair layers, tunnel or underground engineering linings, arch shells, curved panels, irregularly shaped load-bearing components, etc.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1) The fixed-distance support section 22 and the limiting shoulder 23 convert the spacing between adjacent steel mesh layers into the physical dimensions of the connection node. After the locking seat 26 abuts against the limiting shoulder 23, the design spacing can be obtained, reducing the need for temporary pads, ruler verification and on-site welding.

[0014] 2) The socket joint 24 and the locking seat 26 form a one-way mechanical lock. The stability of the steel mesh module does not depend on the direction of gravity. It can adapt to construction postures such as vertical walls, inclined shells and upward linings, and reduce the risk of mesh slippage or detachment caused by spraying impact.

[0015] 3) The limiting shoulder 23 also serves as the termination reference for the spray layer thickness. The anti-blocking protection cap 25 seals and protects the socket joint 24 and the annular locking groove 242, which helps to prevent the connection part from being blocked, buried or contaminated by mortar.

[0016] 4) Geometric recognition mark 251 enables the three-dimensional scanning system or laser rangefinder system to directly detect the position of the interlayer connection node and determine the relative height difference between the limiting shoulder 23 and the current sprayed surface 5, so that the detection object can be expanded from general surface flatness to whether the next layer of steel mesh can be assembled, improving the verifiability of the connection between layer-by-layer processes.

[0017] 5) The arrangement of nodes with denser perimeter and staggered internal arrangement takes into account edge stability and spraying channels. Spraying window 3, combined with bidirectional oblique spraying, can compensate for the shadow on the back of the steel bars from different directions and improve the concrete wrapping around the mesh and connecting nodes.

[0018] 6) Each intermediate steel mesh module uses the same socket interface, which can be repeatedly assembled on site after being prefabricated in the factory. There is no need to pre-set a complete steel cage, which reduces the continuous obstruction of the spray gun path and material flow by the steel skeleton.

[0019] 7) Structural nodes, spray thickness control, scanning or distance measurement verification and module assembly constitute an interdependent technical chain. Removing any core structure such as distance setting, limiting, anti-blocking or self-locking will make it difficult to achieve the effects of stable layer spacing, reliable connection and continuous spraying construction at the same time. Attached Figure Description

[0020] Figure 1 A schematic diagram showing the self-locking connection status of adjacent steel mesh modules at fixed intervals; Figure 2 A schematic diagram of the socket self-locking and anti-blocking protection structure of the interlayer connection node; Figure 3 This is a schematic diagram showing the arrangement of interlayer connection nodes at the edges, interiors, and spray windows; Figure 4 A schematic diagram showing the continuous assembly of multi-layer modular steel mesh along the thickness direction of the component. Figure 5 A flowchart illustrating the layer-by-layer collaborative construction process of jet 3D printing and modular steel mesh. Figure 6 A schematic diagram illustrating the online identification and closed-loop handling of exposed socket joints with anti-blocking protective caps.

[0021] Figure 7 This is a schematic diagram of the annular locking groove structure.

[0022] Reference numerals: 1—Planar steel mesh; 2—Interlayer connection node; 21—Fixed joint; 22—Spacing support section; 23—Limiting shoulder; 24—Socket joint; 241—Conical guide head; 242—Annular locking groove; 25—Anti-clogging protective cap; 251—Geometric identification mark; 26—Locking joint; 261—Open sleeve; 262—Elastic locking plate; 3—Spraying window; 4—Concrete substrate; 5—Spraying surface; 6—Three-dimensional scanning system; 7—Printing spray gun. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments are used to illustrate the technical concept and possible implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or conventional adjustments made to the shape, material, number of nodes, mesh curvature, and spraying parameters of the connection nodes without departing from the technical concept defined in the claims are all included within the scope of the present invention.

[0024] This invention provides a fixed-distance self-locking steel mesh spray-printed 3D-printed concrete structure. The structure includes a concrete matrix 4 formed by spray-printing 3D and at least two steel mesh modules arranged along the thickness direction of the component. Fixed joints are provided on some grid nodes of the planar steel mesh of the bottom steel mesh module, and locking joints are provided on some grid nodes of the planar steel mesh of the top steel mesh module; locking joints are provided on the front side of some grid nodes of the planar steel mesh of the middle steel mesh module, and fixed joints are provided on the rear side of some grid nodes of the planar steel mesh of the middle steel mesh module. Each fixed joint is provided with a fixed-distance support section extending in the direction of the layer to be constructed. A limiting shoulder is provided at the end of the fixed-distance support section, and a socket joint extends outward from the limiting shoulder. The locking seat has an open sleeve for inserting the socket joint and a locking member for preventing the socket joint from retracting in the opposite direction. After the socket joint is inserted into the locking seat at the corresponding position of the adjacent planar steel mesh, the end face of the locking seat abuts against the limiting shoulder to limit the design spacing between adjacent planar steel meshes. When the concrete around the current steel mesh module is sprayed to the corresponding position of the limiting shoulder, the socket joint remains outside the concrete spraying surface so that the next planar steel mesh can be socketed and locked. The fixed joints and corresponding locking joints between adjacent planar steel meshes form interlayer connection nodes.

[0025] This invention comprises three types of reinforcing mesh modules. The first type has a fixing seat and a component connected to the fixing seat only on the rear side of the planar reinforcing mesh sheet. The second type has a locking seat on the front side, a fixing seat on the rear side, and a component connected to the fixing seat. The third type has a locking seat only on the front side of the planar reinforcing mesh sheet. The second type of reinforcing mesh module also includes modules with different positions of the front locking seat to achieve an alternating layout of interlayer connection points between adjacent layers.

[0026] The planar steel mesh 1 is formed by cross-welding, binding or mechanical connection of longitudinal and transverse steel bars.

[0027] In this invention, one side of the spray surface is defined as the front, and the opposite side is defined as the rear.

[0028] Interlayer connection nodes 2 are provided at at least some of the grid nodes of the planar steel mesh 1, including a spaced support section 22, a limiting shoulder 23, a socket joint 24, a fixed connection seat 21, and a locking seat 26. The fixed connection seat 21 is fixedly connected to the planar steel mesh 1 in a steel mesh module on one side; the other side of the fixed connection seat is connected to one end of the spaced support section 22, which extends along the thickness direction of the component, and its effective length from the plane of the planar steel mesh in a steel mesh module to the limiting shoulder 23 corresponds to the design layer spacing of the adjacent planar steel mesh. A limiting shoulder 23 is provided at the other end of the fixed-distance support section 22. A socket joint 24 is provided on the outside of the limiting shoulder 23. The fixed-distance support section, the limiting shoulder, and the socket joint are coaxially arranged. The socket joint 24 extends from the limiting shoulder 23 to the layer to be constructed. There is a certain distance between the socket joint and the limiting shoulder.

[0029] The locking seat 26 is fixed on the front side of the planar steel mesh of the next steel mesh module. The locking seat 26 is sleeved on the corresponding position of the socket joint 24 of the planar steel mesh of the previous steel mesh module. After locking, the end face of the locking seat 26 abuts against the limiting shoulder 23, thereby directly limiting the spacing between adjacent planar steel meshes through mechanical contact.

[0030] The socket joint 24 preferably includes a tapered guide head 241 and an annular locking groove 242; the locking seat 26 includes an open sleeve 261 and an elastic locking plate 262. When the socket joint 24 enters the open sleeve 261, the tapered guide head 241 causes the elastic locking plate 262 to expand outward. After the annular locking groove 242 passes over the elastic locking plate 262, the elastic locking plate 262 returns to its original position and enters the annular locking groove 242, forming a unidirectional mechanical locking that does not require a separate spring or on-site binding. After the locking is completed, the socket joint 24 restricts the separation of adjacent steel mesh modules along the normal direction of the component, and the limiting shoulder 23 cooperates with the end face of the locking seat 26 to restrict further approach, thereby jointly controlling the layer spacing.

[0031] The annular locking groove 242 is used to limit the elastic locking piece 262.

[0032] To prevent sprayed material from entering the socket joint 24 and the annular locking groove 242, an anti-clogging protective cap 25 is installed on the outside of the socket joint 24. The anti-clogging protective cap 25 is only used during spraying and is removed when assembling the next layer of planar steel mesh after the previous layer of spraying is completed. The side of the anti-clogging protective cap 25 closest to the printed surface abuts against the limiting shoulder 23, and the cap body completely covers the conical guide head 241 of the socket joint 24; the top of the cap body is provided with a cross-shaped ridge, annular boss, or other geometric identification mark 251 that can be identified by three-dimensional scanning or laser ranging.

[0033] The geometric identification mark 251 is used to locate the connection nodes between each layer, and also to determine the relative height difference between the limiting shoulder 23 and the current sprayed surface 5 at the located node; when the relative height difference is within the preset range, it indicates that the current sprayed layer has reached the assembly benchmark and the next layer of steel mesh module can be locked.

[0034] Interlayer connection nodes 2 are alternately arranged along the perimeter of the planar steel mesh 1, and the perimeter can also be denser than the interior to suppress edge warping and local rotation of the mesh. In the interior area, they are arranged in a staggered, checkerboard, or interleaved pattern, with the internal interlayer connection nodes of adjacent layers staggered in planar projection. Multiple spraying windows 3 are reserved between the longitudinal and transverse steel bars of the planar steel mesh and the interlayer connection nodes 2, allowing the spray gun to deliver material to the back of the steel bars from different angles, reducing the shadow area formed by spraying in the same direction.

[0035] Example 1: Three-layer modular steel mesh spray-painted 3D printed wall panel This embodiment takes a jet-printed 3D-printed reinforced concrete wall panel with a length of 3000mm, a height of 2400mm, and a thickness of 300mm as an example. Three layers of steel mesh modules are set inside the wall panel, and the steel mesh 1 in each plane is arranged parallel to the thickness direction of the wall panel; the design spacing between the first layer and the second layer, and between the second layer and the third layer, is 100mm, and the thickness of the protective layer on both sides of the wall panel is 50mm.

[0036] The planar steel mesh 1 is composed of longitudinal and transverse steel bars of HRB400 grade steel with a diameter of 10mm, and the spacing between the longitudinal and transverse grids is 150mm×150mm. The interlayer connection node 2 is a steel component, and the fixed joint 21 is fixed to the intersection of the longitudinal and transverse steel bar grid nodes by welding. The effective length of the spaced support section 22 from the plane of the mesh to the limiting shoulder 23 is 100mm, and the diameter is 12mm; the limiting shoulder 23 is an annular shoulder with an outer diameter of 26mm and a thickness of 4mm; the socket joint 24 extends 20mm outward from the limiting shoulder 23, of which the tapered guide head 241 is 8mm long and the annular locking groove 242 is 4mm wide.

[0037] The locking seat 26 is fixed to the front side of the planar reinforcing mesh of the next reinforcing mesh module, and adjacent reinforcing mesh modules are fixed together through interlayer connection nodes. The inner diameter of the open sleeve 261 is adapted to the outer diameter of the socket joint 24, and two oppositely arranged elastic locking plates 262 are provided at the sleeve inlet. After the socket joint 24 is fully inserted, the elastic locking plates 262 are embedded in the annular locking groove 242, and the inlet end face of the locking seat 26 abuts against the limiting shoulder 23. Since the effective length of the fixed-distance support section 22 is equal to the designed mesh spacing, the distance between the two planar reinforcing meshes 1 after locking is limited to 100mm.

[0038] The anti-clogging protective cap 25 is made of thin-walled engineering plastic or thin-walled metal. An assembly gap of approximately 2mm is provided between the cap body and the socket joint 24. The bottom end of the cap body presses against the limiting shoulder 23. A cross-shaped ridge is formed on the top of the cap body as a geometric identification mark 251, and a pull ring or clamping part is provided. During spraying, the anti-clogging protective cap 25 covers the conical guide head 241 and the annular locking groove 242. After scanning or ranging verification is completed, the mechanical clamp or end effector of the robotic arm removes the protective cap 25 through the pull ring or clamping part.

[0039] Interlayer connection nodes 2 are set at the corners and center of the four sides of the mesh to form outer edge nodes, or they can be arranged more densely. Inside, they are arranged in a staggered pattern every other grid to form internal staggered nodes. The interlayer connection nodes connecting the second and third planar steel meshes are spatially offset by one grid from the interlayer connection nodes connecting the first and second planar steel meshes, so that the projections of the interlayer connection nodes of adjacent layers do not completely overlap. The grid areas without interlayer connection nodes 2 form spray windows 3, allowing the spray gun to approach the back of the steel bars at different angles.

[0040] Before construction, the work surface is cleaned, and a point cloud of the work surface is acquired using a 3D scanning system 6. A geometric model of the wall panel is then established, generating the spraying path, mesh installation elevation, and design coordinates for inter-layer connection nodes. The spraying equipment includes a mobile chassis, a six-degree-of-freedom robotic arm, a printing spray gun 7, a material supply system, a 3D scanning system 6, a laser ranging system, and a control system. Fine aggregate concrete suitable for pumping and spraying can be used as the spraying material; the actual material mix ratio is determined based on the spraying equipment, component orientation, and engineering performance requirements.

[0041] First, a 50mm thick base protective layer is sprayed. When the base material can support the reinforcing mesh module and the surface still maintains interlayer bonding capacity, the first reinforcing mesh module is placed according to the design coordinates, so that the spaced support section 22 is perpendicular to the mesh plane and faces the side to be constructed. Then, an anti-clogging protective cap 25 is installed on the outside of each socket joint 24. During the spray printing process, the position of each interlayer connection node is determined by a 3D scanning system 6 or a laser rangefinder system installed at the end of the robotic arm or near the printing gun, and the relative position of the current spray surface 5 to the geometric identification mark 251 of the limiting shoulder 23 or the anti-clogging protective cap 25 is measured.

[0042] The spraying process is divided into two stages: back filling and surface shaping. In the back filling stage, the spray gun 7 sprays from both sides of the wall panel normal at opposite angles through the spray window 3, so that the area blocked by the steel reinforcement in the first spray is filled by the second spray. In the surface shaping stage, the spray gun 7 sprays strip by strip along a direction close to the normal, and uses the limiting shoulder 23 as the thickness reference, so that the current sprayed surface 5 and the limiting shoulder 23 are within the preset relative height difference range, with an allowable deviation of ±3mm.

[0043] After the current layer is sprayed, the 3D scanning system 6 or the laser ranging system identifies the geometric identification mark 251 on the top of each anti-blocking protective cap 25, and calculates the relative height difference between the limiting shoulder 23 and the current sprayed surface 5 (e.g., Figure 6 (As shown). If the relative height difference is greater than the upper limit, it indicates that there is insufficient material around the node, and the control system generates a local replenishment path; if the relative height difference is less than the lower limit, it indicates that there is too much material near the limiting shoulder 23 or the connection part is covered, then stop spraying in this area and scrape or trim the excess material; if the interlayer connection node is tilted or misaligned beyond the allowable value, it is corrected before the next mesh assembly.

[0044] After scanning or ranging verification is passed, the anti-blocking protective cap 25 is removed from the mechanical clamp or end effector of the robotic arm. The second steel mesh module, with the pre-set locking seat 26, is aligned with the socket joint 24 of the first steel mesh module and pressed in along the normal direction of the wall panel. When the elastic locking plate 262 enters the annular locking groove 242 and the end face of the locking seat 26 abuts against the limiting shoulder 23, the fixed-distance self-locking of the second steel mesh module is completed. The second interlayer concrete is sprayed in the same manner and the third steel mesh module is locked in place. Finally, a 50mm thick outer protective layer is sprayed.

[0045] After construction, the wall panel surface is repaired and cured, and the position of the steel mesh modules, component thickness, and surface quality are checked. In the above method, the steel mesh modules achieve mechanical stability after each locking, without relying on their own weight or setting temporary diagonal bracing in the wet concrete.

[0046] Example 2: Curved lining or arch shell components This embodiment is used for curved lining or arch shell components. Each steel mesh module is prefabricated into a curved mesh sheet adapted to the design curvature, and the spaced support sections 22 are set along the normal direction of the local curved surface. The first steel mesh module can be fixed to the bottom concrete through embedded parts, foundation connectors or local anchors, but subsequent steel mesh modules are directly connected to each other through socket joints 24 and locking seats 26, and it is not required that each layer of mesh be connected to the rock mass anchor rod separately.

[0047] For arch or upward-facing operations, the elastic locking plate 262 of the locking seat 26 prevents reverse withdrawal after the socket joint 24 is inserted, and the limiting shoulder 23 prevents further pressing in. Therefore, the stability of the mesh does not depend on the direction of gravity. The spraying path is generated according to the local normal of the curved surface. The spray gun 7 fills the back from the adjacent spraying window 3 with two opposite tangential angles, and then shapes the surface along the local normal. The three-dimensional scanning system 6 or the laser ranging system uses the curved surface design model as a reference to determine the relative height difference and node offset between the limiting shoulder 23 and the current spraying surface 5.

[0048] Example 3 In this embodiment, the socket joint 24 (see...) Figure 7 The rear part of the socket joint 24 is a tapered guide head 241, and the front of the tapered guide head is provided with an annular locking groove 241. The width of the annular locking groove is such that it can limit the position of the elastic locking piece when it is embedded in the locking seat.

[0049] Each intermediate steel mesh module has a pre-set locking seat on the side facing the previous construction layer (front side) and a socket joint on the side facing the next construction layer (rear side), allowing multiple planar steel mesh panels to be continuously and repeatedly assembled along the thickness direction of the component using the same interface; the outermost steel mesh module of the component only has locking seats facing the adjacent module. Both locking seats and fixed seats can be prefabricated and fixed in the corresponding positions on the planar steel mesh panels in the factory. When making interlayer connections, the positions of the locking seats correspond one-to-one with the positions of the socket joints connected to the fixed seats of the previous layer, and the whole assembly is pressed in to achieve interlayer connection. On one side of the middle planar steel mesh panel, a locking seat is set on the front side and a fixed seat is set on the rear side. The positions of the grid nodes fixed on the front locking seats and the rear fixed seats on the same planar steel mesh panel are different, so that the interlayer connection nodes formed by the connection of the next adjacent layer through the fixed seats and locking seats are staggered from the interlayer connection nodes of the previous adjacent layer.

[0050] During construction, steel mesh modules are placed layer by layer, protective caps are installed, the back of the steel bars is filled with bidirectional oblique spray, scanning or distance measurement is performed for verification, the caps are mechanically removed and the next module is locked in place, and this process is repeated until the designed thickness is reached. This invention can reduce temporary supports and manual verification, stably control the mesh layer spacing and protective layer thickness, reduce the risk of mesh slippage under spraying impact, and improve the material wrapping quality around the steel bars and connection nodes.

[0051] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A 3D-printed concrete structure using a fixed-distance self-locking steel mesh spraying method, comprising a concrete matrix formed by layer-by-layer spraying, and at least two planar steel mesh sheets spaced apart along the thickness direction of the concrete matrix; characterized in that, Fixed joints are provided on some grid nodes of the bottom planar steel mesh, and locking joints are provided on some grid nodes of the top planar steel mesh; locking joints are provided on the front side of some grid nodes of the middle planar steel mesh, and fixed joints are provided on the rear side of some grid nodes of the middle planar steel mesh. Each fixed joint is provided with a fixed-distance support section extending in the direction of the layer to be constructed. A limiting shoulder is provided at the end of the fixed-distance support section, and a socket joint extends outward from the limiting shoulder. The locking seat has an open sleeve for inserting the socket joint and a locking member for preventing the socket joint from retracting in the opposite direction. After the socket joint is inserted into the locking seat at the corresponding position of the adjacent planar steel mesh, the end face of the locking seat abuts against the limiting shoulder to limit the design spacing between adjacent planar steel meshes. When the concrete around the current steel mesh module is sprayed to the corresponding position of the limiting shoulder, the socket joint remains outside the concrete spraying surface so that the next planar steel mesh can be socketed and locked. The fixed joints and corresponding locking joints between adjacent planar steel meshes form interlayer connection nodes.

2. The fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to claim 1, characterized in that, The socket joint includes a tapered guide head and an annular locking groove disposed at the rear of the tapered guide head; the locking member consists of at least two elastic locking pieces extending inward from the inner wall of the open sleeve. When the tapered guide head is inserted, it pushes the elastic locking pieces to deform outward elastically. After the annular locking groove passes the elastic locking pieces, the elastic locking pieces reset and are embedded in the annular locking groove.

3. The fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to claim 1, characterized in that, The socket joint is fitted with a detachable anti-clogging protective cap. The open end of the anti-clogging protective cap abuts against the limiting shoulder and together with the limiting shoulder seals the socket joint. The outer surface of the anti-clogging protective cap is provided with raised or recessed geometric identification marks. The geometric identification marks are used by a three-dimensional scanning system or a laser ranging system to identify the position of the interlayer connection node and determine the relative height difference between the limiting shoulder and the current spraying surface.

4. The fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to claim 3, characterized in that, The anti-blocking protective cap includes a cap body and at least one of a cross-shaped ridge, an annular boss, or a polygonal identification head disposed on the top of the cap body. An assembly gap of 1 to 3 mm is provided between the cap body and the socket connector. The cap body is provided with a pull ring or clamping part for removal by mechanical clamps.

5. The fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to any one of claims 1 to 4, characterized in that, The interlayer connection nodes are continuously or densely arranged along the perimeter nodes of the planar steel mesh, and are spaced apart in a quincunx, checkerboard, or staggered manner inside the planar steel mesh; the internal interlayer connection nodes of adjacent planar steel mesh layers are staggered in planar projection, so that a spraying window for the jetting material flow is formed between adjacent planar steel mesh layers and interlayer connection nodes.

6. The fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to claim 1, characterized in that, The effective length of the fixed-distance support section from the planar steel mesh to the limiting shoulder is 30-150mm, the length of the socket joint extending from the limiting shoulder is 10-30mm, and the radial protrusion width of the limiting shoulder relative to the fixed-distance support section is 3-10mm; the diameter of the steel bars in the planar steel mesh is 6-16mm, and the mesh spacing is 80-250mm.

7. A method for constructing a fixed-distance self-locking steel mesh sprayed 3D printed concrete structure according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1, perform 3D scanning modeling of the work surface, establish the work surface model and generate the installation coordinates of the spraying path, planar steel mesh, and inter-layer connection nodes; S2, spraying the bottom layer of concrete to the installation elevation of the first steel mesh module; fixed joints and their connecting components are provided on some grid nodes of the planar steel mesh of the first steel mesh module; S3, place the first steel mesh module with its socket joint facing the layer to be constructed, and check its planar position, normal direction and protective layer thickness; S4, Install anti-blocking protective caps on the outside of the socket joint, spray and fill the back of the planar steel mesh and the area around the interlayer connection node from at least two different directions through the spraying window, and continue spraying to the corresponding position of the limiting shoulder. S5. Use a three-dimensional scanning system or laser ranging system to identify the geometric identification marks of the anti-blocking protective cap, determine the position of the interlayer connection node and the relative height difference between the limiting shoulder and the current spraying surface, and carry out local re-spraying, scraping or correction of abnormal areas. S6, remove the anti-blocking protective cap by means of mechanical clamp or end effector of mechanical arm, press the next steel mesh module with the pre-set locking seat into the socket joint of the previous steel mesh module until the locking component and the locking part of the socket joint are engaged and the end face of the locking seat abuts against the limiting shoulder. S7. Repeat steps S4 to S6 until the designed number of reinforcement layers and component thickness are achieved, forming a continuous modular steel reinforcement skeleton along the component thickness direction. Then spray the outermost protective layer and cure it.

8. The construction method according to claim 7, characterized in that, In step S5, the offset of the interlayer connection node is determined by the difference between the three-dimensional coordinates of the geometric identification mark and the design coordinates, and the current spray layer thickness is determined by the relative height difference between the geometric identification mark of the limiting shoulder or anti-blocking protective cap and the current spray surface. When the relative height difference is greater than the upper limit, local re-spraying is performed around the interlayer connection node. When the relative height difference is less than the lower limit, spraying in that area is stopped and the material covering the outside of the limiting shoulder or anti-blocking protective cap is removed. Step S4 includes back filling spraying and surface shaping spraying; the back filling spraying of the rebar is carried out through the spraying window at opposite angles along both sides of the component normal, so that the shadow areas of the two sprayings compensate each other; the surface shaping spraying is carried out along the component normal direction and the limiting shoulder is used as the thickness reference. When placing the steel mesh module, the sprayed concrete is within a construction time window that can support the steel mesh module and still has interlayer bonding ability on the surface; after the steel mesh module is locked, it does not need to rely on its own weight to maintain stability. The mechanical locking formed by the socket joint and the locking seat is used to limit the relative displacement of the steel mesh module along the normal and tangential directions of the component.

9. The construction method according to claim 7, characterized in that, The spraying equipment used in the construction method includes a mobile chassis, a six-degree-of-freedom robotic arm, a printing spray gun, a feeding system, a three-dimensional scanning system, a laser ranging system, and a control system. The three-dimensional scanning system or laser ranging system is set at the end of the robotic arm or near the printing spray gun to measure the relative position between the current spraying surface and the geometric identification mark of the limiting shoulder or anti-clogging protective cap. The control system adjusts the spray gun moving speed, spray flow rate, spray gun posture, and number of repeated sprays based on the measurement results.

10. A component constructed using the construction method of any one of claims 7-9, or having a fixed-distance self-locking steel mesh sprayed 3D printed concrete structure as described in any one of claims 1-6, characterized in that, The component is any one of the following: wall panel, bridge deck or road repair layer, tunnel or underground engineering lining, arch shell, curved panel, or irregularly shaped load-bearing component.

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